STUDIES OF STRUCTURAL, NONLINEAR OPTICAL AND THERMAL 
PROPERTIES OF SPECIFIC NONCONJUGATED CONDUCTIVE POLYMERS 
INCLUDING A  
CO-POLYMER STYRENE-BUTADIENE-RUBBER 
 
by 
 
Gurudutt Telang 
 
 
 
 
A thesis submitted to the Graduate Faculty of 
Auburn University 
 in partial fulfillment of the 
 requirements for the Degree of 
 Master of Science  
 
Auburn, Alabama 
August 4, 2012 
 
 
 
 
Keywords: Nonconjugated conductive polymer, Styrene-butadiene-rubber, Photovoltaic,  
               Quadratic Electro-optic effect, Differential Scanning Calorimeter 
 
 
Copyright 2012 by Gurudutt Telang 
 
 
Approved by 
 
Mrinal Thakur, Chair, Professor of Mechanical Engineering 
Dan Marghitu, Professor of Mechanical Engineering 
P K Raju, Thomas Walter Distinguished, Professor of Mechanical Engineering 
 
 
 
ii 
 
 
 
 
 
 
 
Abstract 
 
 
 The structures, quadratic electro-optic effects, thermal properties, and 
photovoltaic characteristics of specific nonconjugated polymers have been studied. 
Various tools and techniques such as Optical absorption, Differential Scanning 
Calorimetry, and FTIR spectroscopy have been used to study these polymers, in 
particular a nonconjugated co-polymer styrene-butadiene-rubber (SBR). The optical 
absorption spectrum of styrene-butadiene-rubber at low doping of iodine showed two 
peaks at 4.27 eV and 3.2 eV due to radical cations and charge-transfer from double bond 
to dopant respectively. Upon doping, FTIR showed a reduction in the intensity of peaks   
964 cm-1 and 910 cm-1 corresponding to =C-H bending vibration-band. This is due to 
transformation of double bonds into radical cation upon charge transfer. 
Quadratic electro-optic effect for iodine doped styrene-butadiene-rubber has been 
measured at specific wavelengths 633 nm and 1550 nm using field-induced birefringence 
method. The Kerr coefficients measured at 633 nm and 1550 nm were 3.1x10-10 m/V2 and 
1.2x10-10 m/V2 respectively. These Large Kerr coefficients and third order susceptibilities 
have been attributed to the subnanometer-size metallic domains (organic quantum dots) 
formed upon doping and charge-transfer. 
 Thermal properties of the specific nonconjugated conductive polymers have been 
studied over a range of temperatures (-550C to 1100C) before and after doping with 
iodine. It was observed that specific heat capacity of poly(?-pinene) increases upon 
iii 
 
doping while in the case of 1,4-trans-polyisoprene, SBR and cis-1,4-polyisoprene 
reduces. The Tg of undoped poly(?-pinene) as observed is at 770C and the Tm of           
1,4-trans-polyisoprene has been found to be at 600C in this range respectively. After 
doping these thermal transitions were not clearly observable. In the case of                
styrene-butadiene-rubber and cis-1,4-polyisoprene, no significant change in heat flow 
characteristics and line-shape was found before and after doping with iodine. 
 The refractive indices of iodine doped poly(?-pinene) were calculated using 
Kramer-Kronig transformations utilizing the optical absorption data for high level of 
doping. Refractive indices at specific wavelengths (633nm) for doped PBP and SBR have 
been determined by measuring reflectivity at different angles of incidence. Photovoltaic 
effect in a composite involving nonconjugated conductive polymer, poly(?-pinene) (PBP) 
has been studied. Photovoltaic cells were constructed with iodine-doped poly(?-pinene) 
film sandwiched between two electrodes: 1) titanium dioxide on ITO glass and 2) carbon 
on ITO glass, and using potassium iodide as an electrolyte. It was observed that as the 
intensity of the incident light increases the photo-current and photo-voltage increases 
proportionally (photovoltaic effect). 
 Thus structural, optical, quadratic electro-optic effect, thermal properties and 
photovoltaic studies of specific nonconjugated conductive polymers including a novel   
co-polymer (Styrene-butadiene-rubber) have been made.
iv 
 
 
 
 
 
 
 
Acknowledgments 
 
 
 This work would not have been possible without the help, support and 
guidance of many close individuals. I take this opportunity first to express my gratitude 
to my advisor Dr. Mrinal Thakur who has not only guided in my research but also has 
been a great mentor to me throughout my study at the Auburn University. His 
suggestions and guidance from time to time has proved to be instrumental to this work. I 
am also very grateful to my committee members   Dr. Maghitu and Dr. P K Raju for their 
valuable time and serving as my committee members. 
Also, I am thankful to Photonic Research Material laboratory where I have spent most of 
the time for my research. I appreciate all the help from my colleagues Sapana Srivastava, 
Prashant Dubey and Mradul Sangal at Photonic Materials Research Laboratory. I am also 
thankful to all the lab instructors from various department labs for their instructions and 
help in my experiment that I conducted. I want to thank my Auburn friends (Vamsi, 
Rohan, Meetesh, Suryakant, Gopal), Mumbai University friends and colony friends for 
their encouragement and help during my masters. Finally, I thank my Mom, Dad, Purva, 
and rest of my family for their constant support and unconditional love. 
 
 
 
 
v 
 
 
 
 
 
 
Table of Contents 
 
 
Abstract???????????????????????????????.. ii 
Acknowledgments ???????????????????????????. iv 
List of Tables ?????????????????????????????. ix 
List of Figures ????????????????????????????? x 
Chapter 1 INTRODUCTION???????????????????????.. 1 
Chapter 2 BACKGROUND???????????????????????? .5 
 2.1 Governing Maxwell?s Equation ? ????????????????... .5 
 2.2 Interaction of light in an optical medium??????????????..6  
        2.2.1 Isotropic medium  ...................................................................................6 
        2.2.2 Anisotropic medium ? ???????????????? .??... 7 
        2.3.1 Linear optical processes ? ??????????????? .??. 8 
        2.3.2 Non Linear optical processes ? ?????????????. .........9 
             2.3.2.1 Second order nonlinear processes ? ???????????.. 9 
                     2.3.2.1.1 Sum-Frequency Generation???????????? 10 
                     2.3.2.1 2 Difference-Frequency Generation ? ???? .???? 11 
                     2.3.2.1 3 Second Harmonic Generation ? ????? .????... 11 
                     2.3.2.1 4 Third Harmonic Generation ? ????? .?????.. 12 
                     2.3.2.1 5 Optical Rectification Generation ? ??? .?????.. 13 
             2.3.2.2 Third order nonlinear processes ????????????? 13 
vi 
 
        2.4 Nonlinear optical materials ? ????????? .???????. 15 
             2.4.1 Second order Optical Material ? ?????? .??????? 15 
             2.3.4.2 Third order Optical Material ? ???????????? .? 16 
 2.5 Nonconjugated conducting polymers (NCP) ? ???? .???????. 17 
 2.6 FTIR Spectroscopy ? ????????????????????? .18 
 2.7 Electro-Optic Effect ? ???????????????? .????... 19 
 2.8 Differential Scanning Calorimetry (DSC)?????????????... 22 
 2.8 Refractive index???????????????????????... 23 
        2.8.1 Kramers- Kronig Relations in Nonlinear optics????????? 26 
Chapter 3 OBJECTIVES????????????????????????... 27 
Chapter 4 NONCONJUGATED CONDUCTIVE POLYMERS?????????.. 29 
 4.1 Poly (?-pinene) (PBP)?????????????????????. 30 
 4.2 Polyisoprene ???????????????????????.......3 1 
        4.2.1 Trans-1,4-polyisoprene (TPI) .???????????????.. 31 
        4.2.2 Cis-1,4-polyisoprene (CPI)????????????????... 32 
 4.3 Styrene-butadiene-rubber (SBR)?????????????????. 33 
Chapter 5 COMPARISON OF OPTICAL PROPERTIES OF NANOMETALLIC AND 
DOPED NONCONJUGATED CONDUCTIVE POLYMERS?????????? .34 
 
 5.1 Introduction??????????????????????? ..?? 34 
 5.2 Nonlinear optical properties......................................................................?... 35 
 5.3 Comparison of Third order Optical Nonlinearities????????? ..? 36 
Chapter 6 QUADRATIC ELECTRO- OPTIC EFFECT AND STRUCTURAL STUDIES 
OF NONCONJUGATED CO-POLYMER STYRENE-BUTADIENE-RUBBER?? ...38 
 
 6.1 Introduction?????????????????????????.. 38 
vii 
 
 6.2 Optical absorption??????????????????????? 39 
 6.3 FTIR Measurements????????????? ?????????. 41 
 6.4 Sample preparation for Electro-optics experiment??????????.. 42 
 6.5 Experimental Setup ??????????????????????. 43 
 6.6 Result and Discussion?????????????????????.. 44 
 6.7 Conclusion?????????????????????????... 48 
Chapter 7 STUDIES OF THERMAL PROPERTIES IN NONCONJUGATED 
POLYMERS USING DIFFERENTIAL SCANNING CALORIMETRY (DSC)............49 
  
 7.1 Introduction?????????????????????????.. 49 
 7.2 Specific heat of Nano particles????????????????........ 49 
 7.3 Differential Scanning Calorimetry (DSC)? ????????????... 50 
 7.4 Experiment?????????????????????????... 51 
 7.5 Results???????????????????????????.. 52 
        7.5.1 DSC of trans-1,4-polyisoprene???????????????.. 52 
        7.5.2 DSC of Poly(?-pinene) ??????????????????. 55 
        7.5.3 DSC of Styrene-Butadiene-Rubber ??????????? .??.. 57 
        7.5.4 DSC of Cis-1,4-polyisoprene????????????? .??? 60 
 7.6 Discussion?????????????????????????? 62 
 7.7 Conclusion?????????????????????????... 64 
Chapter 8 PHOTOVOLTAIC EFFECT IN A COMPOSITE INVOLVING IODINE-
DOPED POLY(?-PINENE), A NONCONJUGATED CONDUCTIVE POLYMER......73 
  
 8.1 Introduction???????????????????????? ......66 
 8.2 Experiment????????????????????????? ...68 
 8.3 Result and Discussions????????????????????? 69 
viii 
 
 8.4 Conclusion?????????????????????????... 71 
Chapter 9 STUDY OF ABSORPTION COEFFICIENT AND REFRACTIVE INDICES 
OF NONCONJUGATED POLYMERS USING SPECIFIC METHODS????? ....72 
  
 9.1 Introduction?????????????????????????. 72 
 9.2 Result and Discussions?????????????????????7 2 
 9.3 Conclusion?????????????????? ???????... 77 
Chapter 10 SUMMARY????????????????????????? 79 
BIBLIOGRAPHY???????????????????????????.. 81 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ix 
 
 
 
 
 
 
 
List of Tables 
 
 
Table 5.1 Third order nonlinear properties of nanoparticle and polymers?????... .37 
Table 6.1 Comparison of third order nonlinearities??????????????... 47 
Table 7.1 Specific heat capacities of specific NCP before and after iodine doping?? ..64 
Table 9.1 Refractive indices for different incident angles for PBP????????... 76 
Table 9.2 Refractive indices for different incident angles for SBR????????... 77 
Table 9.2 Refractive indices of iodine doped SBR at 633 nm for specific methods.........77 
  x 
 
 
 
 
 
 
 
List of Figures 
 
 
Figure 2.1: Sum-Frequency Generation?????????????????... 11 
Figure 2.2: Difference of Frequency Generation??????????????. 11 
Figure 2.3: Second-harmonic Generation ????????????????... 12 
Figure 2.4: DSC plot of heat flow vs. temperature in a material ???????? 22 
Figure 2.5: Refractive index and Absorption coefficient of fused silica ????? 25 
Figure 4.1: Molecular structure of poly(?-pinene) ?????????????.. 30 
Figure 4.2: Molecular structure of trans-1, 4- polyisoprene?????????? 31 
Figure 4.3: Micrograph of trans-1,4- polyisoprene film ???????????. 32 
Figure 4.4: Molecular structure of cis-1,4-polyisoprene ? ?????????? 32 
Figure 4.5: Molecular structure of styrene-butadiene-rubber ?????????. 33 
Figure 5.1 Absorption spectra of Gold nanoparticle of different diameter ?? .?? 35 
Figure 5.2: Third order susceptibility of gold nanoparticles ?????????... 36 
Figure 6.1: Transformation of double bond into cation radicals in SBR ????? 39 
Figure 6.2: Optical absorption of styrene-butadiene-rubber ?????? .???.. 40 
Figure 6.3: Optical Absorption of Silver Nanocrystal ???????????? 41 
Figure 6.4 FTIR spectroscopy of styrene-butadiene-rubber ???? .?????.. 42 
Figure 6.5: Molecular structure of undoped styrene-butadiene-rubber ? ..????. 43 
Figure 6.6: Experimental setup for electro-optics ?????????????... 44 
Figure 6.7: Quadratic modulation depth due to applied Electric field for 633nm ?.. 44 
Figure 6.8: Quadratic modulation depth due to applied Electric field for 1550 nm ...45 
Figure 7.1: DSC plot of heat flow vs. temperature in a material ???????? 51 
  xi 
 
Figure 7.2: DSC scan of trans-polyisorene before doping ??????????.. 53 
Figure 7.3: DSC scan of trans-polyisoprene after doping ??????????... 53 
Figure 7.4: DSC scan of trans-polyisoprene before doping (00C to 300C) ????. 54 
Figure 7.5: DSC scan of trans-polyisoprene after doping (00C to 300C) ????? 54 
Figure 7.6: DSC scan of poly(?-pinene) before doping ???????????.. 55 
Figure 7.7: DSC scan of poly(?-pinene) after doping ????????????. 56 
Figure 7.8: DSC scan of poly(?-pinene) before doping for range (00C to 250C) ?... .56 
Figure 7.9: DSC scan of poly(?-pinene) after doping for range (00C to 250C) ??.. 57 
Figure 7.10: DSC scan of styrene-butadiene rubber before doping ??????? 58 
Figure 7.11: DSC scan of styrene-butadiene rubber after doping ???????... 58 
Figure 7.12: DSC scan of SBR before doping for the range (250C to 350C) ???.. 59 
Figure 7.13: DSC scan of SBR after doping for the range (250C to 350C) ????. 59 
Figure 7.14: DSC scan of cis-1,4-polyisoprene before doping ????????... 60 
Figure 7.15: DSC scan of cis-1,4-polyisoprene after doping ?????????.. 61 
Figure 7.16: DSC scan of undoped CIS before doping for range (200C to 350C) ?.. 61 
Figure 7.17: DSC scan of undoped CIS before doping for range (200C to 350C)?... 62 
Figure 8.1: World Population statistics ?????????????????... 67 
Figure 8.2: World Energy Consumption from 1980-2030 ?????????? ..67 
Figure 8.3: Experimental setup for photovoltaic ?????????????.... 69 
Figure 8.4: Plot of Intensity vs. Photo-Voltage ??????????????.. 69 
Figure 8.5: Plot of Intensity vs. Photo-Current??????????????... 70 
Figure 9.1: Absorption coefficient SBR at heavy doping with iodine?????? .74 
Figure 9.2: Refractive index of heavily poly(?-pinene) ???????????. .75 
 
  1 
 
Chapter 1 
 
INTRODUCTION 
 
Photonics is one of the fastest growing fields of science and technologies in 
the modern world. It blends together optics and electronics to effectively handle and 
process enormous amount of data with exceptional speed. Photonic science has wide 
range of applications that include generation, emission, signal processing, 
transmission, switching, amplification, detection and sensing of light. Also photonics 
finds its application in numerous fields including telecommunication, medical 
science, optics, electronics etc. Continued research on linear and nonlinear optical 
properties of materials builds the core of such applications in photonics. Novel 
nanomaterials and structure provide immense scope to the field of photonic 
applications. This presented thesis deals with research performed on new organic 
nanometallic materials. 
At present, scientists and technologists are exploring new types of renewable 
resources i.e. wind energy, geothermal energy, bio-fuel, solar energy etc. The need for 
exploring these renewable resources is due to the increasing consumption of 
nonrenewable energy resources. Renewable source device such as solar cell is used to 
convert incident light energy into electrical energy. These cells are generally made of 
some inorganic and organic materials, which absorb light from the source, release 
electrons and produce electricity. Inorganic materials have been the
  2 
 
main ingredient of photovoltaic cell for few decades, but its fabrication and installation is 
costly. Due to these drawbacks of inorganic materials, organic material got much into 
attention of photonic researchers. Low dielectric property and high optical property not 
only makes them applicable in photovoltaic cell but also used in many other application 
of photonics, i.e. electro-optics, absorption etc. 
In this jet age, we deal with enormous amount of data processing at exceptionally 
high speed. As a result it has generated a considerable amount of interest among 
researchers to explore these organic materials like nonconjugated conductive polymers in 
the communication field. Their low dielectric constants ensure that the speed is never 
compromised. Further ease of fabrications and the flexibility they provide to the engineer 
at molecular level have made them very popular. Hence it would not be surprising, if 
these materials soon become the backbone of the optical communication, information 
storage and other important fields. As a result exploring the basic nonlinear properties of 
such novel materials is must. But much waits to be explored and experiment in this field. 
The research discussed is divided into the following areas: 
1. Quadratic electro-optics effect of nonconjugated conductive co-polymer styrene-
butadiene-rubber , doped with iodine at shorter wavelength  
2. Thermal properties of specific nonconjugated conductive polymers            poly(?-
pinene) (PBP), trans-1,4-polyisoprene (TPI), cis-1,4-polyisoprene (CIS) and a co-
polymer styrene-butadiene-rubber (SBR) by using Differential Scanning 
Calorimeter, before and after doping with iodine. 
3. Photovoltaic effect in a composite involving nonconjugated conductive polymer, 
poly(?-pinene) (PBP). 
  3 
 
4. Refractive indices of iodine doped nonconjugated co-polymer                           
styrene-butadiene-rubber (SBR) and poly(?-pinene) using Kramer-Kronig 
transformation and determination of refractive index for different angle of 
incidence. 
The research work is systematically organized into chapters with an appropriate 
sequence. 
Chapter 1: Consist of an introduction to the thesis research work. 
Chapter 2: titled ?Background? explains the basic theories and fundamental concepts of 
photonic and nonlinear optics and properties, that support the proposed thesis. 
Chapter 3: Overall goals of this research and studies are discussed in this chapter, titled 
as ?Objective?. 
Chapter 4: Discusses the physical structure and electrical properties of nonconjugated 
conductive polymers. 
Chapter 5: Optical nonlinear properties of various nanomaterials and metal nanoparticles 
are explained and compared with optical properties of nonconjugated conductive co-
polymer styrene-butadiene-rubber in this chapter. 
Chapter 6: Describes the quadratic electro-optic effect in the nonconjugated conductive     
co-polymer iodine-doped styrene-butadiene-rubber measured at specific wavelength 633 
nm and 1550 nm. 
Chapter 7: Explains the thermal properties on specific nonconjugated conductive 
polymers before and after doping. This study of characterization of the specific 
nonconjugated polymer is done by differential scanning calorimetry. 
  4 
 
Chapter 8: Discusses the photovoltaic effect in a composite involving nonconjugated 
conductive polymer, poly(?-pinene) (PBP).   
Chapter 9: Studies the refractive index of nonconjugated polymers using Kramer-Kronig 
transformation.  
Chapter 10: Summarizes the proposed research work. 
  5 
 
Chapter 2 
 
BACKGROUND 
 
 
 
In recent years, there has been a rapid expansion of activities in the field of 
nonlinear optics. Nonlinear optics is the study of phenomena that occurs due to 
modification of the optical properties of a medium in the presence of an electric field 
or an intense laser light. Some of these nonlinear responses includes: linear and 
quadratic electro-optic modulation/switching, optical limiting, frequency conversion, 
all-optical modulation, and others [1-4]. 
2.1 Governing Maxwell?s Equation 
The theory of propagation of light was first proposed by James Clerk Maxwell 
and was later confirmed by Heinrich Hertz [5, 6]. Light travels as an electromagnetic 
wave for which the direction of propagation, magnetic field and electric field are 
mutually perpendicular to each other. The propagation of light is governed by 
Maxwell?s equations. Maxwell?s equations describe classical optics and 
electrodynamics using a set of partial differential equations. The Maxwell?s equations 
for electric and magnetic field vectors E   and H   and B   and D   as electric and 
magnetic displacement vectors is established using following equations. [7, 8] 
                                                                         
                                                                          
                
    
                                                   
  6 
 
                
    
                                                
Where   and J stands for electric charge and current densities respectively.In optics, 
for most cases, one deals with negligible electrical or thermal conductivity referred as 
dielectric. This causes no free charge and no current (Conductivity is defined by the 
flow of electric charges) resulting into   and J to be zero.  When electromagnetic field 
is applied, there is a possible atomic orbital distortion which is described as 
polarization magnetization. The effect of electromagnetic field on material media is 
governed by these equations 
                                                                   
                                                               
? and ? are permittivity tensor and permeability tensor and     and       are electric and 
magnetic polarizations respectively. The    and    are permittivity and permeability 
of vacuum respectively. 
2.2 Interaction of light in an optical medium 
Optical media can be classified into two types: 
1. Isotropic medium 
2. Anisotropic medium 
2.2.1  Isotropic medium 
The term ?isotropy? refers to having similar properties for all direction in a 
medium. The electric field   , displacement vector     and polarization    do not depend 
on the direction of electric field in an isotropic medium. The polarization induced is 
always parallel to applied electric field; it always carries a linear relationship. Thus 
linear polarization for an isotropic medium is expressed by the following equation. 
  7 
 
                                                          
Correspondingly, the relationship between the displacement vector and the 
susceptibility   is given by 
                                                
 
In an isotropic medium electrons are tightly bound to the nucleus, which 
makes these materials non-conducting and nonmagnetic. As a result these materials 
can be compared to the dielectric medium when subjected to an external electric field. 
 The polarization due to the dipole, induced by the electric field is mention below [2]. 
                                                
Where P is the polarization, e is the electronic charge, and r is the 
displacement induced by the electric field. Correspondingly the wave equation for 
such a medium can be stated as 
             (                                      
2.2.2  Anisotropic medium 
The term ?anisotropy? refers to different properties for different directions in a 
media. In this directionally dependent nonlinear medium, the polarization is not 
necessarily parallel to the applied electric field. And hence the polarization P can be 
expressed by the following equations given below. 
                                                                  
                                                                  
                                                               
Where ? the susceptibility is a tensor of rank 2 and the electric displacement vector D 
is given by 
  8 
 
    ?       ?          ?                                   (2.14) 
where ?    represents the permittivity tensor. If a co-ordinate system is chosen such that 
it coincides with the principal dielectric axes of the medium, we get the following 
matrices. 
 
  
  
  
   =  
    
    
    
   
  
  
  
                                      (2.15) 
The energy density due to the electric field is given by 
                               (2.16) 
Since the x, y, z are chosen along the principal axes, we have 
U =                                                (2.17) 
2U =       
  
 +     
  
 +     
  
                                       (2.18) 
If x= D1     , y= D2    , z= D3              (2.19) 
  
    + 
  
    + 
  
    = 1                                               (2.20) 
Equation (2.20) is known as the indicatrix equation, it shows the relationship 
between the refractive index and the direction of polarization in a nonlinear 
anisotropic medium. Since the indicatrix equation traces the path of an ellipsoid, it is 
also referred to as refractive index ellipsoid [9]. 
2.3.1  Linear optical processes  
Before the introduction of lasers, optical phenomenon was considered to be 
linear. The relationship between the polarization and the electric field was considered 
to be linear. The electric field and linear polarization are expressed as 
                                                                                  
                                                                                         
  9 
 
And the real dielectric constant is expressed as 
                                                                
Where n is refractive index, ? is absorption coefficient and      is linear 
susceptibilities respectively. 
2.3.2  Nonlinear optical processes 
            It was observed that with the advent of lasers linear relationship did not hold 
good. A nonlinear dependence of polarization with applied electric field was reported                               
[8-12]. In nonlinear optical media, the propagation of light is not so simple. The 
polarization depends on higher powers of electric field and is usually highly 
anisotropic. In an isotropic dielectric media; polarization occurs due to applied 
electric field, while in anisotropic media it may not be. 
                                                                              
                                                                                                     
Where                are second and third order susceptibilities, and      and 
           represents linear and nonlinear polarization respectively. 
                           
                                                                    
                                                                                    
2.3.2.1  Second order nonlinear processes 
Nonlinear optical materials can be classified as centrosymmetric and non 
centrosymmetric. Centrosymmetric materials are those materials in which polarization 
is an odd function of electric field. Since P (-E) = -P (E) holds well in 
centrosymmetric materials, the even terms are zero. In centrosymmetric materials 
  10 
 
       =                       (2.29) 
This is possible only when ?(2) = 0 or ?(2n) = 0 for all positive integers of n.  
Whereas non-centrosymmetric materials are those materials in which 
polarization is an even function of electric field. Since P (-E) is not equal to P (E) in 
non-centrosymmetric materials, the even terms can be nonzero. Clearly it is seen that 
the optical material should be non-centrosymmetric to exhibit second order nonlinear 
properties. 
Nonlinear optics gives rise to a host of optical phenomena. Discusses below 
are few second order nonlinear properties. These are as follows.  
1. Sum frequency generation, Second harmonic generation  
2. Difference frequency generation  
3. Third harmonic generation 
4. Optical rectification 
2.3.2.1.1 Sum-Frequency Generation    
 Sum frequency generation is a nonlinear optical process used to study the molecular 
structure and dynamics at the surface and interfaces.  When in a strong applied field, 
two laser beams having strong frequency ?1 and a weak applied field frequency ?2 
interact with nonlinear material; there is a situation in which the strong signal ?1, 
combine with the weak signal ?2 to produced higher frequency signal ?3= ?1+?2              
[ 7].  
 
 
 
 
 
  11 
 
 
 
 
Figure 2.1: Sum-Frequency Generation 
2.3.2.1.2 Difference-Frequency Generation  
In this process, applied input fields with input frequencies ?1 or ?2 and ?3  
interact with nonlinear medium to produce output frequency as the difference between 
the other two frequencies. This process is similar to sum of frequency process. 
However in this processes, applied input fields (with frequencies ?1 or ?2 and ?3) 
interact with lossless nonlinear material to produce an output signal at difference 
frequency (?2 = ?3 - ?1) or (?1 = ?3 ? ?2).  
 
 
 
 
 
 
 
2.3.2.1.3 Second harmonic Generation 
  
Second harmonic generation (SHG) is also denoted as frequency doubling. It 
is a nonlinear optical process in which photons interact with a nonlinear material, 
merging effectively to form new photons with twice the energy, and therefore twice 
the frequency and half the wavelength of the input photons. Second harmonic 
?3= ?1 + ?2 
 + 
?1 
 ?2  
?
?3 
 
?1 
?2 
?3 
 
?2 
?1 
Figure 2.2: Difference of Frequency Generation 
 
  12 
 
generation is regarded as a specialcase of sum frequency generation. Full permutation 
symmetry of susceptibilities have been seen in second harmonic generation which are 
primarily caused by two fundamental frequencies ?1 and ?2= 2?1. The ?2= 2?1 is the 
second harmonic frequency/frequency doubling frequency as shown in Figure 2.3 
 
Figure 2.3: Second-harmonic Generation 
2.3.2.1.4 Third Harmonic Generation  
Third Harmonic Generations is also known as optical frequency multiplier. An 
optical frequency multiplier is a nonlinear optical device, in which photon interact 
with a nonlinear material, and merge effectively to form new photons with greater 
energy, producing higher frequency and shorter wavelength.  Direct third harmonic 
generation (THG), also called frequency tripling) exists, and can be used to discover 
the interface between material of different excitability. It is similar second harmonic 
generation and produced higher frequency and shorter wavelength than second 
harmonic generation. It is widely used in high power lasers and inertial confinement 
fusion experiments. 
2.3.2.1.5 Optical Rectification 
Nonlinear second order susceptibility is the primary cause of origin of 
nonlinear optical processes. In second order susceptibility there are two different 
cases presented  
  13 
 
                =                                  2.30) 
 
It consists of one real part and one imaginary part. The real part of                
defines Pockels effect or linear electro-optics. When an optical beam and a dc (or low 
frequency ac) electric field interact with a second order material, there is change in 
refractive index observed proportional to applied dc electric field. This process is 
known as Pockel's effect or linear electro-optic effect. This was first observed by a 
German physicist Friedrich Pockel in 1906 [13, 14] .Where else the real part of  
                define another process known as optical rectification. When two 
electric fields interact with each other in nonlinear medium results in a static electric 
field then the process is called optical rectification [16].  
2.3.2.2  Third order nonlinear processes  
Third order nonlinear processes are based on the term ?0 ?(3) E3 in the 
polarization expansion of the Eqn.( 2.27). The most general third order process 
nonlinear process involves the interaction of four different frequency connected by ?1 
+?2 +?3 = ?4. The ?1, ?2 and ?3 are distinct frequencies for third order polarization in 
NLO materials and are given by the equation below: 
E(t) = E1(t)               
 
            
 
    + c.c      Eqn. (2.31) 
 When some of these materials interact with an optical field and a slow time 
varying external field, the change in the indices is quadratically related to the external 
field applied. This effect is denoted as Kerr effect. This effect was first reported by a 
Scottish physicist John Kerr in 1875. [17]. Kerr effect can be observed when a laser 
beam propagates through a third order material. Kerr effect is the change in 
  14 
 
the refractive index of a material in response to an applied electric field and is given 
by the equation below  
                       
Where ?n = change in refractive index,  
            K = Kerr co-efficient,  
           f = wavelength of the laser beam and 
           E = magnitude of the slow time varying electric field. 
Where n2 is the nonlinear refractive index and I is the intensity of the laser 
source.  
                                     
The nonlinear refractive index is related to the third order susceptibility ?3 as 
per the equation below. 
         
   
                      
Where   the weak field refractive index of the material and c is is the speed of light.  
When a laser source whose transverse intensity propagates through a nonlinear 
material, a phase delay due to Kerr effect deforms the wave front causing it to either 
focus or defocus depending on the sign of the nonlinear refractive index n2 [13].  If n2 
is negative the material behaves like a negative lens which diverges the beam and is 
called self-defocusing. When n2 the material behaves like a positive lens, it converges 
the incident beam is known as self-focusing. 
2.4 Nonlinear optical materials 
The field of nonlinear optics has witnessed exponential growth after the 
advent of laser since 1960. Nonlinear materials interact with high intensity light to 
produce nonlinear effect. Based on the composition, these materials can be primarily 
  15 
 
be categorized into two classes organic and inorganic [18]. Inorganic NLO materials 
such as lithium niobate (LiNbO3) or potassium dihydrogen phosphate (KH2PO4) are 
known to exhibit second harmonic generation (SHG) effect [19]. As a result during 
the last 40 year these inorganic materials have been seen dominating the world of 
nonlinear optics. Where else as far as organic materials are concerned, during the 
1990?s, p-electron organic materials were identified as promising candidates for 
nonlinear optical applications. However, more recent studies of NLO materials have 
focused on the use of organic materials with ?-electron conjugated systems [20]. Such 
materials offer the advantages of larger optical nonlinearity and faster optical 
response. Other driving forces behind the recent development of organic NLO?s 
include higher bandwidth, lower driving voltage, more flexible device design, and 
potentially lower processing cost [21]. In this section we will discuss about nonlinear 
optical materials .This section is divided into two subsections namely second order 
materials and third order materials respectively.  
2.4.1              Second order Optical Material  
 In early 1960s development and characterization of nonlinear material was 
done on some criteria. These criteria includes the material must be non-
centrosymmetric, must have excellent optical quality and high refractive index, must 
easily available etc. The first reported nonlinearity was observed in quartz when 
Franklin and co-workers recorded a very weak second harmonic signal in quartz using 
Q-switched ruby laser source [22]. In 1962 two research teams individually showed 
that phase matching in ammonium-dihydrogen phosphate (ADP) can result in 
significantly stronger second harmonic signals [23,24]. Two years later Boyd and co-
workers reported lithium meta-niobate (LiNbO3) to be ?An efficient phase matchable 
NLO material.?[25]. Further inquiries in LiNbO3 showed some advantages and 
  16 
 
disadvantages, but the despite this shortcoming this material is perhaps the most 
popular inorganic NLO material. Later several investigators presented the application 
of organic nonlinear material in various fields i.e. photovoltaic, photonic devices etc. 
However these researchers reported the potential of organic materials in 
photonic devices much attention was given to inorganic materials in 1960s [26, 27]. 
This trend changed when Kutz demonstrated a powder technique to evaluate the 
optical nonlinearities in powder samples of materials. The shift in focus on organic 
nonlinear materials was due to the several advantages they have over their inorganic 
counterparts. Since NLO effects are electronic in nature, exceptionally high switching 
speeds can be attained [28].  
2.4.2  Third Order Optical Materials 
A wide range of materials have been invested for third order nonlinearities 
since for these materials did not require symmetry condition. Different techniques 
such as third harmonic generation (THG), degenerate four-wave mixing (DFWM and 
self-focusing techniques were used to determine third order susceptibility. However 
due to variability of the nature of experimental conditions used in the optical 
processes, it was difficult to compare the results initially. However the ongoing 
research from several years has made it possible to develop materials that have high 
third order. One such developed third order material is nonconjugated conducting 
polymers. A particular discussion has been done on nonconjugated conducting 
polymers as third order materials. 
2.4.2.1  Nonconjugated conducting polymers (NCP)  
It was reported back in 1988 by M Thakur that conducting polymers are not 
limited to conjugated systems alone. It was reported that with an appropriate 
substituent a backbone having an isolated double-bond structure may become 
  17 
 
conducting. Thus new set of polymers came into existence called as nonconjugated 
conducting polymer. The first reported NCPs by Thakur and co-workers were:        
1,4-cis-1,4-polyisoprene, 1,4-trans-polyisoprene and poly(dimethyl butadiene) [29]. 
Subsequently, poly(?-pinene) [30], polyalloocimene, polynorbornene and styrene-
butadiene-rubber (SBR), [31] were shown by Thakur?s group to belong to the class of 
nonconjugated conductive polymers. It was seen that the conductivity of the polymers 
increased many orders of magnitude with doping of iodine.  
Upon doping these nonconjugated polymers, positive charges/holes are 
created at the isolated double-bond sites. There is also a formation of I3? upon 
doping. The hole is loosely bound to I3?. In short iodine dopant interacts with the 
double bond of the polymer backbone causing the double bond to lose an electron. 
The transfer of charges occurs due to the movement of the positive carriers or holes 
that are created upon doping. The  =C-H bending vibration band of the polymer 
significantly reduced upon doping since the double bonds transformed into radical 
cations upon doping and charge-transfer . Thus nonconjucated polymers when doped 
with iodine which is an electron acceptor become electrically conductive. Moreover 
these nonconjugated conductive polymers have been shown to have quantum dot 
characteristics because of the confinement of charges within subnanometer domains. 
Such confinement has led to significantly larger third order optical nonlinearities for 
these systems compared to known materials and structures. When one or more free 
electrons are confined within a space typically ranging from a few nanometers to 
microns, the system is called as a quantum dot. The number of confined electrons, 
which can be accurately manipulated, dictates the size and shape of the q-dot. The 
behavior of quantum dots is analogous to that of atoms. Just as there are energy levels 
in atoms, q-dots also possess energy levels which exist due to the confinement of the 
  18 
 
electrons. This leads to significant orders of magnitude enhancement of the third 
order optical susceptibility due to the confined electronic structure. A change in 
refractive index was reported in iodine doped1, 4-cispolyisoprene at 633nm for an 
applied voltage of 2V/?m. The corresponding Kerr coefficient was reported to be 
1.6?10-10 m/V2 which is about 66.67 times higher than that of nitrobenzene 
measured at 589nm.[32] A modulation depth of 0.12% was reported in iodine       
poly(?-pinene) at 633nm.  
2.5  FTIR Spectroscopy  
FTIR stands for Fourier Transform Infrared Spectroscopy. FTIR is used 
mainly for characterization purpose. It can be used to indentify primarily chemicals 
that are organic and inorganic. It can also be used to analyze solids, liquids, gasses or 
to find a component in an unknown mixture. FTIR is perhaps the most powerful tool 
for identifying the functional groups or the type of chemical bonds in polymers. These 
functional groups include ketone, ester, acid etc. FTIR makes use of absorption, 
transmission and emission of light at different wavelengths to characterize any 
material.  The wavelength of the light absorbed or transmitted is used to make 
structural characterization of the chemical bond in a polymer. By interpreting the 
infrared absorption, the chemical bonds in a polymer can be determined. FTIR spectra 
for of pure compounds are generally unique. As a result the spectrum of an unknown 
can be identified by comparison to the spectrum of known compounds. It gives peaks 
at different wavelengths depending on the vibrational energies of the chemical 
groups. Thus, each peak corresponds to specific chemical groups. Molecules consist 
of atoms with different bond lengths and bond angles. Moreover these bonds vibrate 
at different frequencies depending on the type of bonds. For any bond there is specific 
frequency at which it vibrates. Based on the different stretching and bending vibration 
  19 
 
frequency corresponding  different wavelengths or wave-numbers are determines , 
and groups like CH2, CO, CH and NH groups can be identified [33]. The total 
transmission ?T? can be recorded as  
     
 
                                                 
And the transmission can be converted into absorption by using the Beer Lambert 
Law. 
                                       
For example, chemical bond C-O absorbs near 1100-1300cm-1 and O-H group, 
absorbs strongly at ~ 3300-2500cm-1. Ketone have strong absorption due to the 
presence of C=O carbonyl group near 1725-1705cm-1 [34, 35]. Similarly, the other 
organic functional group can be characterized. 
2.6   Electro-Optic Effect   
The electro-optics effect refers to the change in refractive index due to the 
applied electric field. If the change is linear to the applied electric field it is called 
linear electro optic effect. In this case the induced polarization of the material is 
linearly proportional to the electric field and is also termed as Pockels effect. Crystal 
having centered of symmetry show no linear electro-optics effect. There is induced 
index change that is directly proportional to the square of the electric field instead of 
varying linearly with it. In other words induced polarization in the material is 
quadratically proportional to the applied electric field. Such effect is also referred as 
Quadratic electro-optics effect or Kerr effect. This interaction of the optical radiation 
with the material subjected to an electric field can be described completely in terms of 
the impermeability tensor ?ij by the relation [36] 
  20 
 
              
 
                                                         
Quantum theory of solids, dictates that the optical impermeability tensor 
depends on the distribution of charges in the crystal. Application of electric field 
realigns these charges with a possible slight deformation of the ion lattice which 
causes change in the optical impermeability tensor. This change in the impermeability 
tensor can be related to the applied electric field by the following relation. 
                                             
Where the      and      stands for linear electro-optic coefficient and quadratic 
electro-optic coefficient respectively. This quadratic electro-optics effect was first 
discovered by J. Kerr in 1875 in optically isotropic media such as glasses and liquids. 
Unlike linear electro-optic effect which is observed in anisotropic media, the 
quadratic electro-optic effect is seen in all media as there is no symmetry restriction. 
When an electric field is applied, the dimensions and orientation of the index ellipsoid 
change depending on the direction of the applied electric field and also on the 
symmetry properties of the 6 ? 6 matrix elements of the      coefficient. The 
quadratic electro-optic coefficients for an crystal is given by 
 
 
  21 
 
 The index of ellipsoid for such an isotropic medium on the application of E reduces 
to 
                                                                              
Where     and      are the quadratic electro-optic coefficients and E is the 
magnitude of the applied electric field. 
                                       
                                       
The birefringence ne ? no  is given by 
                                             
By using the relationship                     can be written a 
                                                 
Eq. 2.45 is often written in terms of the Kerr coefficient (K) in m/V2 as 
                          
Where             
This equation represents the relation between change in refractive index and the Kerr 
coefficient (K). 
2.7  Differential Scanning Calorimetry (DSC)  
DSC is used for thermal analysis of various materials. The different properties 
of the materials are been studied as they change with temperature. DSC curves reflect 
change in energy as function of time.  In DSC two pans sit on an identical platform 
connected to a furnace by a common heat flow path and the entire working of the 
equipment is controlled by a computer. In one pan the polymers is placed and the 
  22 
 
reference is in the other. The computer is programmed to increase the temperature of 
both the pans at same specified rate from one temperature to another. The computer 
makes sure that the heating rate stays exactly the same throughout the two separate 
pans in the experiment. The polymer is the one sample; it implies that it will take 
more heat to keep the temperature of sample pan increase at the same rates as the 
reference pan. The extra amount of heat required forms the basis of the DSC 
experiment. DSC graphs consist of temperature increase on the X axis and heat flow 
on the Y axis [37]. The whole plot finally will somewhat looks like this. 
 
Figure 2.4: DSC plot of heat flow vs. temperature in a material 
. 
 During the working the temperature of both the sample and reference are 
increased at a constant rate. Since the DSC is at constant pressure, heat flow is 
equivalent to enthalpy changes:  
      
  
                             
  23 
 
Here      is the heat flow measured in mcal sec-1. The heat flow difference between the 
sample and the reference is 
  
      
  
            
  
                                              
So in general differential scanning calorimeter is an instrument used for 
measuring specific heat capacities, heat flow rate, phase transition temperatures, glass 
transition (Tg) and melting temperature (Tm).  Glass transition (Tg) is the phase 
change from amorphous solid into glassy liquid due to increase in temperature and 
also cause change in specific heat capacity [38, 39, 81].  Whereas melting temperature 
is that temperature at which, molecules of amorphous material get freedom to move, 
convert into crystalline phase. Thus DSC is an important tool in exploring thermal 
properties of materials. 
2.8  Refractive index 
In optics the refractive index of a medium is the measure of the speed of 
light in that medium. It is expressed as a ratio of the speed of light in vacuum to that 
in the considered medium [40, 41].  
This can be written mathematically as: 
                         
Where c = speed of light in a vacuum. 
             v= speed of light in medium. 
  24 
 
Refractive index is a function of frequency or wavelength. The relationship 
between relationship between relative permittivity ??? and relative permeability ??? is 
given in the Eqn. (2.49) 
                                                
                                               
Usually at higher optical frequency, relative permeability of optical material become 
near unity.   
This can be seen in the equation given below, which is obtained by substituting Eqn. 
(2.50) in Eqn. (2.49)        
                                               
The refractive index for glasses and crystals are seen in the range of 1.4 ? 2.8, 
lie in visible spectra region.  Generally, semiconductors also show good nonlinear 
properties. A very good example is Gallium Arsenide (GaAs) with refractive index of 
~3.5 at 1?m, due to strong absorption at different wavelengths below the band gap 
wavelength of  ~870nm [42] It has also been seen that refractive index increase 
towards shorter wavelength; as can be seen for fused silica in Figure 2.5.  
  25 
 
 
Figure 2.5: Refractive index and Absorption coefficient of fused silica                    
(SiO2 Glass) [46] 
These nonlinear properties are expresses as complex number consisting of real and 
imaginary part similar to the refractive index, dielectric and susceptibility. The 
following equations given below represent the real and imaginary part relationship in 
susceptibility, dielectric and refractive index respectively.      
                                                           
                                                          
                                                                        
Where     ,       and       and are real parts and      ,        and         
and are imaginary parts of refractive index, susceptibility and dielectric constant 
respectively. 
  26 
 
2.8.1   Kramers- Kronig Relations in Nonlinear optics  
Researchers Ralph Kronig and Hendrik Anthony Kramer together found a 
relationship between the real part and the imaginary part of the refractive index with 
the help of the theory on analytic complex numbers. [8, 44-46]. Similar relations 
between real and imaginary parts of the dielectric constant and susceptibility are 
given below in Eqn. (2.55) and Eqn. (2.56) 
              
          
      
  
 
                                
            
          
      
  
 
                           
Refractive index expressed in term of absorption coefficient   
               
   
      
  
 
                       
 These Kramers?Kronig relations are very useful in nonlinear optics [47]. It 
relates the change in the refractive index caused by some excitation of a medium             
(e.g. generation of carriers in a semiconductor) to the change in the absorption (i.e. 
absorption coefficient). As the change in the absorption is normally significant only in 
a limited range of optical frequencies, it can be relatively easily measured. And the 
refractive index and reflectivity can be measured from the change in absorption 
coefficient respectively [8, 48]. 
  27 
 
Chapter 3 
 
OBJECTIVES 
 
The overall objective of this research is to explore the structural, photovoltaic 
and quadratic electro-optics effect of specific nonconjugated polymers. These 
polymers mainly include poly(?-pinene) (PBP), cis-1,4-polyisoprene (CPI) and    
trans-1,4-polyisoprene (TPI) and a copolymer styrene-butadiene-rubber (SBR). 
The structural changes in the molecular structure of a specific nonconjugated 
polymer SBR has been studied using FTIR, optical absorption, optical microscopy, 
before and after doping with iodine. The effect on specific heat capacity and the heat 
flow of specific nonconjugated polymers before and after doping were studied using a 
differential scanning calorimeter (DSC). The heat flow of these polymers has studies 
over a wide range of temperature from -500C to 1100C. The effects on specific heat 
capacity of these nonconjugated polymers at specific temperature range before and 
after doping is also discussed. However further investigations have to be carried in 
this field. 
The quadratic electro-optic effect in the styrene-butadiene-rubber co-polymer 
will be studied using field-induced birefringence technique, and the Kerr coefficients 
have be determined at 633nm and 1550 nm. The measured optical nonlinearities are 
been correlated to the nanometallic like structures of doped polymers.
  28 
 
The effect of using a doped nonconjugated polymer in a photovoltaic cell has been 
examined. The photovoltaic effect on the photocurrent due to the usage of nonconjugated 
polymer has been studied and discussed. Measurement and calculation of refractive 
indices of these novel nonconjugated polymers before and after doping are important. 
Linear absorption coefficients (UV-Visible) of styrene-butadiene-rubber have been 
measured for different doping levels of iodine. Refractive indices have been calculated 
using Kramer-Kronig transformation of absorption data for different doping levels. 
Numerical integration using MATLAB software was used for these calculations. Also the 
refractive indices of nonconjugated polymer, poly(?-pinene) (PBP) and SBR have been 
calculated at specific wavelengths 633nm by measuring reflectivity at 50, 100 and 150 
angles of normal incidence respectively. 
Overall this thesis will discuss the research study made on the structure 
properties, photovoltaic effect, electro-optics, refractive indices and thermal in specific 
doped nonconjugated conductive polymers and copolymer. 
  29 
 
Chapter 4 
 
NONCONJUGATED CONDUCTIVE POLYMERS 
 
Organic polymers and inorganic materials have a wide range of applications in the 
field of photonics. Nonlinear optical properties of organic polymers have received 
substantial research attention in view of wide range of applications in the field of 
photonics especially in telecommunication photonics. Among organic materials, 
conjugated polymers having one-dimensional delocalization of electrons become 
electrically conductive upon doping. In 1988, M. Thakur demonstrated that with 
nonconjugated polymers with at least one double-bond in the repeat also become 
electrical conductive upon doping [31].  
Recently, nonconjugated conductive polymers have been shown to have quantum 
dot characteristics because of the confinement of charges within subnanometer domains. 
Such confinement has led to significantly larger third order optical nonlinearities for 
these systems compared to known materials and structures. This has led to significant 
interest of researchers in the field of nonconjugated polymers.  Since then various 
nonconjugated polymers have been researched by many researchers worldwide. This 
chapter illustrates literature review on specific non conjugated polymers that have been 
explored in this research work. These specific nonconjugated polymers include             
  30 
 
poly(?-pinene) (PBP), cis-1,4-polyisoprene (CPI), trans-1,4-polyisoprene (TPI) and a 
copolymerstyrene-butadiene-rubber (SBR).Earlier study includes exploring the 
conductivity of non-conjugated polymers upon doping with iodine.Upon doping, there 
is formation of radical cation and charge transfer from double bond to dopant which is 
primarily responsible for the non-conjugated polymers to become conductive.It was 
found that the conductivity was based on the number of fraction of double bonds in 
the nonconjugated polymers. The ratio of double bonds to the total number of bonds 
along the polymer chain is termed as fraction of double bonds. Conjugated polymers 
have double bonds alternating with single bonds; as a result their number fraction of 
double bonds is 1/2, while non-conjugated conductive polymers have double bond 
number fractions less than ?.   [29, 31, 32]. Mentioned below are few specific non 
conjugated polymers on which the research has been carried out in this work. 
 4.1 Poly (?-pinene) (PBP) 
PBP has been reported as novel nonconjugated polymer. It has ring type 
structure, with 1/6 number fraction of double since double repeat after every sixth 
carbon. The conductivity of PBP rapidly increases upon doping with iodine. The 
molecular structure of styrene ?butadiene-rubber is shown in the figure below. 
 
 
Figure 4.1: Molecular structure of poly(?-pinene) 
  31 
 
Conductivity of PBP has been measured before and after doping with iodine, it 
increased by many orders of magnitude upon doping with iodine (0.008 S/cm). This is 
due to formation of radical cation and charge transfer from double bond to dopant. 
Earlier research show some characterization of PBP has been done by study of its thin 
film with optical absorption, FTIR, X-ray diffraction and other spectroscopic 
methods. PBP shows large nonlinear properties and have large Kerr coefficient, 
1.6x10-10 m/V2 at 1550 nm [49, 50]  
 4.2 Polyisoprene  
Polyisoprene shows two conformations: trans-1,4-polyisoprene and                          
cis-1,4-polyisoprene. These two conformations have same molecular formula but 
different orientation of carbon atom in the structure. Every fourth carbon atom in both 
the structure has double bond (number fraction of double bond is ?). They have 
maximum conductivity of ~ 0.1 S/cm and the conductivity increases by many orders 
of magnitude after doping with iodine. [29, 32] 
 4.2.1 Trans-1,4-polyisoprene (TPI)  
Trans-1,4-polyisoprene is a polycrystalline material with a planar zig-zag 
molecular structure. Recently it is known for its conductivity upon doping with 
iodine. The molecular structure of trans-1,4-polyisoprene is shown in the Figure 
below. 
 
Figure 4.2: Molecular structure of Trans-1, 4- polyisoprene [51] 
  32 
 
Characterization had done of TPI by study of its thin film with optical absorption, 
FTIR, X-ray diffraction. Kerr coefficient for trans-1,4-polyisoprene has already been 
reported to be 1.6x10-10 m/V2, which is higher than Poly(?-pinene) [29, 31, 51]. The 
above Figure shows a micrograph of trans-1,4- polyisoprene film. 
 
Figure 4.3: Micrograph of trans-1,4- polyisoprene film 
4.2.2 Cis-1,4-polyisoprene (CPI)  
Cis-1,4-polyisoprene is also known as natural rubber. It is a predominantly 
amorphous polymer and gives smooth film when deposited on glass slide from a 
solution. The electrical conductivity of cis-1,4-polyisoprene increases 100 billion 
times upon doping with iodine. The molecular structure of cis-1,4-polyisoprene is 
shown in Figure.4.4. 
 
Figure 4.4:  Molecular structure of Cis-1,4-polyisoprene. 
  33 
 
The characterization of CPI of its thin film with optical absorption, FTIR, X-ray 
diffraction and other spectroscopic methods has been done earlier. Kerr coefficient for 
Cis-1,4-polyisoprene has been already reported to be 1.6x10-10 m/V2, which is 
higher than Poly(?-pinene) [29]. 
 4.3    Styrene-butadiene-rubber (SBR) 
Styrene-Butadiene-Rubber (SBR) is a synthetic rubber copolymer consisting of 
styrene and butadiene. It generally finds its application in car tires due to its ability to 
have good abrasion resistance [71]. Styrene-butadiene-rubber is nonconductive in its 
normal state. It becomes conductive upon doping with doping agents like iodine, 
SnCl4 and SbCl5. Styrene-butadiene-rubber was doped with iodine and it was noticed 
that the conductivity of the styrene-butadiene-rubber film reaches a value of about 
0.01 S/cm and then the value remains a constant as the film is saturated with the 
iodine. The fact that the film darkens upon doping is attributed to the breaking up of 
the double bonds. The molecular structure of styrene-butadiene-rubber is shown in the 
Figure below. 
 
Figure 4.5: Molecular structure of styrene-butadiene-rubber. 
Characterizations of styrene-butadiene-rubber using FTIR, optical absorption and 
DSC in this research work. 
  34 
 
Chapter 5 
COMPARISON OF OPTICAL PROPERTIES OF NANOMETALLIC AND 
DOPED NONCONJUGATED CONDUCTIVE POLYMERS 
 
5.1 Introduction 
 
Nano materials are the area of interest due to its wide application in the field of 
medical, military, biosensors, photovoltaic devices etc. The linear and nonlinear optical 
properties of the main reason for the wide range of application it has. They have a unique 
absorption, transmission and color spectrum pattern which depends on the shape, size and 
the surface of the nanoparticles. 
When the nanoparticles interact with the incident light, electron and photons are 
excited at different wavelength and start oscillating. This results into unusual 
phenomenon known as Surface plasma resonances. This quality of nanoparticles decides 
the magnitude of strong absorption and scattering properties [52-54].This resonance is 
achieved at a specific wavelength and angle. It depends of the nanoparticle sample film, 
the frequency of plane polarized light and the refractive index of the media. Silver and 
gold nanoparticles are the most commonly known for surface plasma resonance. This was 
mainly because of the broad absorption band of wavelengths 400nm (near Ultraviolet) 
and 1000nm (near Infrared). 
  35 
 
 
Figure 5.1 Absorption spectra of Gold nanoparticle of different diameter [55] 
The above Figure clearly suggests that the absorption of gold nanoparticles 
surely depend on the size of the nanoparticles. As the size of the particle increases the 
absorption peak also increases. There is also a shift seen towards shorter wavelengths 
and broadness of peak becoming sharper as one goes from larger size to smaller size. 
5.2 Nonlinear Optical Properties 
 Nonlinear optical properties of nanoparticles like Silver; gold and 
copper have been explored by many researchers. Higher optical absorption and large 
nonlinear properties have been seen in nanoparticles. Both these Third order 
susceptibilities and Kerr coefficient were measured by using Z-scan and it was 
reported that third order  susceptility  for nanometals is the function of frequency 
[57].At higher frequencies and shorter wavelength nanometals show larger kerr 
  36 
 
coefficient and third order susceptibilty. Nonlinear absorption coefficient and 
susceptibility of copper nanoparticles in 2-Ethoxyethanol with 1 wt % PVP has been 
reported by H. H. Huang et. al. in 1997 [58]. They estimated third order absorption 
coefficient is about 15 ?10-10 m/W and ?3 is 4.27? 10-11 esu. ?3 for copper 
nanoparticles also reported by A. Cetin et. al., about 1.55?10-10 esu [58]. Hideyuki 
Inouye et. al (1999) studied Kerr signal of Gold nanoparticles and estimates  is about 
?3  = 2.0 x 10-8 esu [59]. Nonlinear refraction and absorption coefficient at 532 nm 
laser of Au nanoparticles in water have studied by J. T. Seo et.al. He claims that the 
nonlinear absorption coefficient and refractive index were -1.89?10-9 m/W and 
4.54?10-16  m2/W respectively. The Figure given below shows the third order 
susceptibility in resonant region as shown in Figure 5.3 [60]. 
 
Figure 5.2: Third order susceptibility of gold nanoparticles with molar concentration 
5.3 Comparison of Third order Optical Nonlinearities  
  Nonlinear properties of nanoparticles are applicable for ultrafast 
telecommunication, optical switching and other photonic devices. Recent research 
shows that both of the conjugated and nonconjugated polymers exhibit large nonlinear 
optical properties after doping with electron acceptors. Some of conjugated polymers, 
  37 
 
i.e. PTS-polydiacetelene; nonconjugated polymers, i.e. cis-1,4-polyisoprene, trans-
polyisoprene, they have given good response upon iodine doping.  Kerr coefficient for                        
cis-1,4-polyisoprene and trans-1,4-polyisoprene were found 1.6x10-10 (m/V2) and            
3.4 x10-10 (m/V2), which reflect that they are in nanometallic range. Table 5.1 
comparing nonlinear properties of nanoparticles of metals and polymer.   
 
Quantum Dots 
Wavelength 
(nm) 
K 
(m/V2) 
?(3) 
(esu) 
Poly(?-pinene) 1550 nm 1.6x10-10 
3.4x10-8 
Estd 
Cis-1,4-polyisoprene 633 nm 1.6x10-10 
3.4x10-8 
Estd 
Trans-polyisoprene  633nm 3.4x10-10 
5.6x10-
8Estd. 
Poly(ethylenepyrrolediyl) 633 nm 1.2x10-9 10-7 Estd 
Cu : Al2O3 575 nm ----- 10-8 
Au : SiO2 532 nm ----- 1.7x10-10 
PTS-polydiacetylene 
 
1550 nm 3x10-12 5x10-10 
 
Table 5.1: Third order nonlinear properties of nanoparticle and polymers. 
  38 
 
Chapter 6 
QUADRATIC ELECTRO- OPTIC EFFECT AND STRUCTURAL STUDIES 
OF NONCONJUGATED CO-POLYMER STYRENE-BUTADIENE-RUBBER 
 
6.1  Introduction 
Nonlinear optical properties of nano-optical materials have received 
significant research attention in the field of photonics application [1, 29, and 62]. In 
particular, third-order optical materials have attracted significant research interest due 
to their applications in various fields including electro-optic modulation, ultrafast 
switching, optical phase conjugation, optical limiting, etc. [2-4, 67]. Numerous 
classes of third-order materials have been investigated. Conjugated polymers such as 
polydiacetylenes were reported to have to high optical nonlinearities [3, 4]. These 
nonlinear optical properties are mainly attributed because of one-dimensional 
delocalization of electrons.  Also recently, nonconjugated conductive polymers have 
been shown to have quantum dot characteristics because of the confinement of 
charges within subnanometer domains. Such confinement has led to significantly 
larger third order optical nonlinearities for these systems compared to knownmaterials 
and structures. Quadratic electro-optic effect in nonconjugated conductive polymers 
including cis-1,4-polyisoprene, 1,4-trans polyisoprene , poly(b-pinene), 
poly(ethylenepyrrolediyl)  derivative and polynorbornene have been recently reported 
[36,50,69,70]. Exceptionally large Kerr-coefficients (about 30 times that of 
conjugated polymers) has been observed in these systems [36]. 
  39 
 
In this chapter, we discussed structural and nonlinear optical property; in 
particular, quadratic electro-optic effect in iodine doped styrene-butadiene-rubber 
film. 
 
Figure 6.1: Transformation of double bond into cation radicals in SBR 
Positive charge and cation radicals are confined near double in a sub 
nanometer domain as shown in Figure 6.1, which is less than a nano-scale. Below we 
have studied in detail the styrene-butadiene-rubber with the help of optical absorption, 
FTIR spectroscopy and its electro-optic effect has been measured. 
6.2  Optical Absorption 
Structural characterization of styrene-butadiene-rubber was conducted using 
optical absorption. Optical absorption measurements of the films were made using 
Ultrospec 2100 pro by Amersham Biosciences at various doping levels of iodine in 
styrene-butadiene-rubber. Sample made on glass slide were used for optical 
absorption. It was recorded that the absorption of undoped styrene-butadiene-rubber 
to be clearly transparent as shown in    Figure 6.2.  
  40 
 
 
Figure 6.2: Optical absorption of styrene-butadiene-rubber 
However upon doping it shows two peaks, one due formation of radical 
cations at 4.27eV and second due to charge transfer double bond to dopants (electron 
acceptors) at 3.2eV. It was also observed that upon increase in the concentration of 
iodine due to doping, peaks increases and peak correspond to 3.2eV widen ups and 
undergoes red shift due to reduction in separation distance between donor and 
acceptor. The optical absorption of silver nanocrystal has shown in Figure 6.3, 
indicate that absorption peak depends on size of nanoparticles; it increases with 
increase in size of particles [50]. Nonconjugated polymers have comparable optical 
absorption spectrum to the nanometallic absorption spectrum. The peaks of silver 
nanocrystal are at 425nm whereas the peaks of styrene-butadiene-rubber are less that 
400 nm due to its charge confined in subnanometer domain which also suggests the 
nanometallic behavior or quantum dot characteristics of styrene-butadiene-rubber.  
  41 
 
 
Figure 6.3: Optical Absorption of Silver Nanocrystal. 
6.3  FTIR Measurements 
The degree of conductivity of nonconjugated polymer depends on breakdown 
of double bond into radical cation and charges [73-75]. FTIR spectroscopy studies 
were done on styrene-butadiene-rubber both before and after doping with iodine.  
Thin samples were made of styrene-butadiene-rubber and FTIR spectroscopy was 
carried on them before and doping with iodine using Nicolet 6700 FTIR equipment. 
FTIR data indicated the =C-H vibration bands (964 cm-1 and 910 cm-1) of 
polybutadiene decrease upon doping due to transformation of the double bonds into 
radical cation [72] 
  42 
 
 
Figure 6.4 FTIR spectroscopy of SBR 
6.4  Sample preparation for Electro-optics experiment 
Sample of styrene-butadiene-rubber latex was obtained from the Goodrich 
Chemical company. As opposed to conjugated polymers, styrene-butadiene-rubber 
being a nonconjugated co-polymer is easily soluble in common organic solvents like 
toluene and chloroform. Thin films of SBR were prepared by dissolving SBR in 
chloroform on glass substrates. The rubber films thus obtained have a thickness of 
about 3.4 microns and 5 microns. The 5 microns thick sample was measured in 633 
nm measurement, where else 3.4 microns was measured after 1550 nm measurement 
after the experiments have been performed. These films are held in a dish covered 
with aluminum foil and iodine equally placed besides it in the dish. Due to thermal 
evaporation of the iodine, the styrene-butadiene-rubber films get doped. On doping 
the films change color from colorless to black depending on the amount of dopant 
(i.e) iodine that has interacted with the styrene-butadiene-rubber film. The films were 
doped about 7 hours. The molecular structure of the undoped and doped                       
  43 
 
styrene-butadiene-rubber is shown in (Figure.6.1 and Figure.6.5) respectively. The 
doped sample is placed on copper electrodes with (optical glue) styrene applied 
between there surfaces. The sample is then mounted on a fixture to carry out electro-
optics experiment. 
 
Figure 6.5: Molecular structure of undoped styrene-butadiene-rubber 
6.5  Experimental setup 
The high quality films on glass substrate were used to perform quadratic 
electro-optic measurements by field-induced birefringence technique at 633 nm and 
1550 nm. A Helium Neon laser was used to make measurements at 633 nm and 
measurements at 1550 nm were performed using a semiconductor laser (BW-Tek). A 
schematic of the electro-optics set-up is shown in (Figure.6.6). The sample was placed 
between the polarizer and analyzer which were oriented orthogonal to each other to 
facilitate the polarization of the incident laser beam. This is also termed as Cross 
polarization.An AC voltage at 4 kHz was applied across the sample with the help of 
two copper electrodes to create an electric field. The modulation in optical intensity 
due to field-induced birefringence in the sample was measured using a photo-diode 
and a lock-in amplifier latched to twice the frequency of the applied field.  
  44 
 
 
Figure 6.6: Experimental setup for electro-optics 
6.6  Result and Discussion 
 
     Figure 6.7: Quadratic modulation depth due to applied Electric field for 633nm 
  45 
 
 
Figure 6.8: Quadratic modulation depth due to applied Electric field for 1550 nm 
It was observed that the modulation depth quadratically varies with the applied 
field. A typical modulation depth vs. applied field plot is as shown in (Figure.6.7) and 
(Figure 6.8) for 633 nm and 1550 nm respectively. The Kerr coefficients as 
determined from these measurements are 3.1x10-10 m/V2 at 633 nm and              
1.2x10-10 m/V2 at 1550 nm. The value at 633 nm is higher most likely because of 
resonant enhancement. These values are exceptionally large and slightly larger than 
that of doped cis-1,4-polyisoprene [16]. The value at 633 nm is about 129 times larger 
than that of the standard material nitrobenzene (Kerr coefficient is 2.4x10-12 m/V2 at 
589 nm). In comparison, the Kerr coefficient of PTS-polydiacetylene at 1.55 ?m is         
3x10-12 m/V2 [17]. 
The large Kerr Coefficient is observed due to charge transfer involving double 
bond of nonconjugated polymer and the sub-nanometer size nanometallic domains 
(encircled Region in (Figure 6.1) formed upon doping. These structures particularly 
  46 
 
represent novel metallic-like quantum dots of sub nanometer dimension for which 
enhanced optical nonlinearity can be expected. The electrical conductivity of these 
systems is comparable to that of metallic quantum dots / nanoparticles [76]. The 
optical absorption maxima are at higher energies / shorter wavelengths compared to 
metallic quantum dots of some of the smallest sizes known (~ 6 nm) [77]. The 
broader line-width of the optical absorption maximum is consistent with that of a 
nanometal with sub nanometer domain size [78]. These characteristics are all 
consistent with those of nanometallics with subnanometer-size domains.  
  47 
 
Material Wavelength (nm) ?(3) (esu) Kerr coefficient  
(m/V2) 
PTS-
polydiacetylene 
1550 5x10-10 3x10-12 
Poly ?-pinene 633 2.6x10-8Estd. 1.2x10-10 
Cis ?
polyisoprene 
633 3.4x10-8Estd. 1.6x10-10 
Trans-1,4- 
polyisoprene 
633 5.6x10-8Estd. 3.5x10-10 
Trans-1,4- 
polyisoprene 
1550 
4.0x10-8Estd 
2.5x10-10 
Ag-SiO2 1064 7.3x10-10   [42] 3.4x10-12 Estd 
Cu-SrTiO3 770 6.5x10-11  [44] 3.0x10-13 Estd 
styrene-butadiene-
rubber (SBR) 
633 4.97x10-8  Estd 3.1x10-10Estd. 
styrene-butadiene-
rubber (SBR) 
1550 2.16x10-8  Estd 1.2x10-10Estd 
 
Table 6.1: Comparison of third order nonlinearities 
  48 
 
6.7  Conclusion 
 
Thin films of styrene-butadiene-rubber before and after iodine-doping have 
been structurally characterized using optical absorption and FTIR spectroscopy. The 
optical absorption spectrum at low doping shows two peaks at 4.27 eV due to radical 
cation and the other at 3.2 eV due to charge-transfer respectively. Doping leads to a 
reduction of the intensity of =C-H bending vibration-band 964 cm-1 due to formation 
of radical cations upon charge-transfer. Quadratic electro-optics of styrene-butadiene-
rubber has been attributed first time in the field of photonics. Quadratic electro-optic 
measurements of doped styrene-butadiene-rubber have shown exceptionally large 
Kerr coefficients: 3.1x10-10 m/V2 at 633 nm and 1.2x10-10m/V2  at 1550 nm. These 
large nonlinearities have been caused due to the sub-nanometer size metallic domains 
(quantum dots) formed upon doping and charge-transfer involving this nonconjugated 
conductive polymer. These exceptionally large nonlinearities of iodine doped styrene-
butadiene-rubber are important in ultrafast telecommunication devices and various 
other applications in photonics. 
  49 
 
 
Chapter 7 
STUDIES OF THERMAL PROPERTIES IN NONCONJUGATED 
POLYMERS USING DIFFERENTIAL SCANNING CALORIMETRY (DSC) 
 
7.1  Introduction 
Study of thermal properties, heat flow, specific heat capacities and phase 
transition temperatures are important for various applications in thermodynamics and 
nanoparticle technology fields. Thermal properties of polymers and nanoparticles got 
attention of researchers since last few decades. Nonconjugated polymers such as 
poly(?-pinene), 1,4-trans-polyisoprene, styrene-butadiene-rubber and                        
cis-1,4-polyisoprene have shown few nanometallic and crystalline characteristics. 
Thermal properties of nonconjugated polymers such as poly(?-pinene) and                          
trans-1,4-polyisoprene, styrene-butadiene-rubber and cis-polyisoprene using DSC 
graphs have been explored in this chapter. Heat capacities of these polymers before 
and after doping and corresponding effect on Tg and Tm of the polymers before and 
after doping have also been discussed considering the molecular and nano structures 
of these materials before and after doping. 
7.2  Specific heat of Nano particles  
Study of thermal properties of nano sized particles has shown that they exhibit 
higher specific capacity than composite bulk materials (about 10 to 12 times) 
  50 
 
[79]. J.Rupp group in 1987 reported that two nano-crystalline metal particles, Cu and 
Pd have higher compared with polycrystalline.  Nano sized particle have greater 
atomic vibration at high temperature, which leads increase in specific heat capacity 
[80].  Also in the case of CuO, R. S. Prasher observed that the shape of the particles 
does matter for heat capacity. It is seen that cubic and thin particles have greater heat 
capacity. Thus particle size and density does play a role in the heat capacity.  Softer 
nanocrystalline particles have greater atomic vibration than microscopic particles 
resulting into greater heat capacity. 
7.3  Differential Scanning Calorimetry (DSC) 
Differential Scanning Calorimetry (DSC) is the most widely used technique of 
all the thermal analysis method. There are two different types of DSC-methods, 
namely heat flux DSC and the power compensated.  In this research work we have 
used heat flux based DSC apparatus. The DSC equipment consists of two empty 
aluminum pans placed in an isolated chamber so that the initial temperature of both 
the pans remains the same. The polymer whose thermal properties has to be studied is 
kept in one pan which serves as sample pan and the other serves as reference pan. In a 
heat flux DSC machine the material whose thermal properties have to be measured is 
placed in aluminum pan. There is also an empty pan which serves as a reference pan. 
The degrees to which, the rate at which and the end temperature range for the pans are 
defined by the computer controlled heating program. The output graphs of a DSC are 
called thermograms. Thermograms are the plots of the difference of heat delivered to 
the sample and to the reference as a function of the sample temperature. There are 
various kinds of thermograms obtained from DSC analysis which gives different 
kinds of information. Thus differential scanning calorimeter is a conventional 
instrument used for measuring specific heat capacities, heat flow rate and phase 
  51 
 
transition temperatures, glass transition (Tg) and melting temperature (Tm).  Increase 
in temperature leads into change in phase of amorphous solids into glassy liquid; refer 
as glass transition (Tg) and it also cause change in specific heat of materials [80,81].  
At very high temperature, molecules of amorphous material get freedom to move, 
convert into crystalline phase and further increment in temperature cause melting 
denoted as melting temperature (Tm) [81].  Glass transition and melting temperatures 
can be seen in DSC Plot in Figure (7.1) 
 
Figure 7.1: DSC plot of heat flow vs. temperature in a material 
7.4 Experiments 
Thin films of Poly(?-pinene), trans-1,4-polyisoprene were cast on quartz 
substrates from a toluene solution. But it was found that the film of                        
trans-1,4-polyisoprene did not have good optical quality due to existence of 
microscopic or polycrystalline grains. This problem was overcome by adding a very 
small amount of C60 (~ 1% by weight of the polymer) to the solution. This procedure 
led to sharply reduced grain sizes and thus excellent optical quality films. Similarly 
Poly(?-pinene) crystals were dissolved in toluene solutions and were casted on quartz 
  52 
 
substrate. The poly(?-pinene) films were doped with iodine for around 12 hours. 
These both doped and undoped high quality films then were finely powdered and 
were used in DSC. In the case of styrene-butadiene-rubber and cis-1,4-polyisoprene 
similar type of method was used. These rubbers were doped with iodine and 
powdered form was used in the DSC experiment. 
7.5 Results  
7.5.1 DSC of trans-1,4-polyisoprene. 
Heat flow of doped and undoped trans-1,4-polyisoprene has been done on 
specific temperature range from -500C to 1100C. The constant rate of increase in 
temperature was kept 50C. Graphs of rate of heat flow, specific heat capacity and 
temperature were obtained for trans-1,4-polyisoprene before and after doping with 
iodine.. The DSC results for trans-1,4-polyisoprene have been discussed first. Melting 
temperature peak of undoped trans-1,4-polyisoprene has been seen at 600C, which 
also reported by Huafeng Shao et al [40] for TPI with crystallinity about 50-60% and 
Edward G. et al also suggested that melting temperature (Tm) for low melting 
polymer about  640C [83,84]. 
  53 
 
 
Figure 7.2: DSC scan of undoped Trans-polyisorene before doping. 
 
 
Figure 7.3: DSC scan of doped Trans-polyisoprene after doping 
Melting peak can be seen clearly in Figure 7.1 at 60 0C, whereas after doping 
with iodine melting point was not well defined. Specific heat of                             
trans-1,4-polyisoprene  increased after doping with iodine. Figure 7.2 and Figure 7.3 
  54 
 
shows heat capacity and heat flow of undoped and doped trans-1,4-polyisoprene for 
temperature range 100C -30 0C . 
 
Figure 7.4: DSC scan of trans-1,4-polyisoprene before doping (00C to 300C). 
 
              Figure 7.5: DSC scan of trans-1,4-polyisoprene after doping (00C to 300C). 
It was observed in Figures 7.4 and 7.5 that specific heat capacities of trans-1,4-
polyisoprene decrease around 30 degrees from 3.75 J/g0C to 2.42 J/g0C. 
  55 
 
7.5.2 DSC of Poly(?-pinene)   
DSC analysis for temperature range -500C to 1000C was done for doped and 
undoped Poly(?-pinene) . It was observed that the melting temperature peak of 
undoped Poly(?-pinene) before doping has been seen at 770C . Whereas after doping 
it is not distinctly visible.  It is found that the nature of the graphs obtained by the 
DSC of Poly(?-pinene) was in accordance to the graphs mentioned by An-Long Li, 
Xiao-Yan Wang, Hui Liang, Jiang Lu in 2006[85].  
 
Figure 7.6: DSC scan of  Poly(?-pinene) before doping. 
  56 
 
 
Figure 7.7: DSC scan of Poly(?-pinene) after doping. 
Figures 7.6 and 7.7 shows heat flow of doped and undoped Poly(?-pinene) for 
temperature range -500C to 1100C respectively. Specific heat of Poly(?-pinene) 
increased after doping with iodine. Glass transition for undoped                           
Poly(?-pinene)appeared at 770C, but after doping the glass transition was not clear 
observed. 
 
Figure 7.8: DSC scan of poly(?-pinene) before doping for the range (00C to 250C). 
  57 
 
 
Figure 7.9: DSC scan of Poly(?-pinene) after doping for the range (00C to 250C). 
The Figures 7.8 and 7.9 shows heat capacity and heat flow of doped and undoped 
Poly(?-pinene) for the temperature range 10-250C. It was observed in Figure 7.6 and 
Figure 7.7 the specific heat capacities of poly(?-pinene) increases around 30 degrees 
from 2.055 J/g0C to 2.35 J/g0C. 
7.5.3 DSC of Styrene-Butadiene-Rubber 
DSC analysis for temperature range -500C to 1000C was done for doped and 
undoped styrene-butadiene-rubber. It was observed that the melting temperature peak 
of undoped styrene-butadiene-rubber before and after doping was not clearly 
observable. This can be attributed to the increase in rigidity upon doping which the 
polymer undergoes. It is seen that glass transition in SBR takes place at much lower 
temperature, and hence we cannot observe it in the graph below [61]. 
 
  58 
 
 
Figure 7.10: DSC scan of styrene-butadiene-rubber before doping. 
 
Figure 7.11: DSC scan of styrene-butadiene-rubber after doping. 
  59 
 
 
Figure 7.12: DSC scan of SBR before doping for the range (250C to 350C). 
 
Figure 7.13: DSC scan of SBR after doping for the range (250C to 350C). 
It was observed in Figures 7.12 and 7.13 that specific heat capacities of 
styrene-butadiene-rubber reduce around 300C from 2.425 J/g0C to 1.86 J/g0C. 
  60 
 
7.5.4 DSC of Cis-1,4-polyisoprene 
DSC analysis for temperature range -500C to 1000C was done for doped and 
undopedcis-1,4-polyisoprene. It was also observed that the melting temperature peak 
of undoped cis-1,4-polyisoprene before and after doping was not clearly observable in 
the considered temperature range. It is observed that the glass transition of cis-1,4-
polyisoprene takes place below the -500 C [66]. This can be attributed to the increase 
in rigidity upon doping which the polymer undergoes.  
 
 
Figure 7.14: DSC scan of undoped cis-1,4-polyisoprene before doping. 
 
  61 
 
 
Figure 7.15: DSC scan of cis-1,4-polyisoprene after doping (200C to 350C). 
 
Figure 7.16: DSC scan of cis-1,4-polyisoprene before doping for the range 
 (200C to 350C). 
  62 
 
 
Figure 7.17: DSC scan of cis-1,4-polyisoprene after doping for the range                      
(200C to 350C). 
It was observed in Figure 7.16 and 7.17 that specific heat capacities of                      
cis-1,4-polyisoprene reduce around 300C from 2.954 J/g0C to 0.72 J/g0C. 
7.6 Discussion 
It was observed that the specific heat capacity of poly(?-pinene) increases 
upon doping with iodine. However nonconjugated polymers like cis-1,4-polyisoprene, 
trans-1,4-polyisoprene and styrene-butadiene-rubber show decrease in the specific 
heat capacity upon doping with iodine. Upon doping, the double bond of these 
nonconjugated polymers transfers into cation radical and charge transfer takes place 
from double bond to the dopant. This confinement of charges within subnanometer 
domains gives rise to quantum dot characteristics (organic quantum dots). Such 
confinement gives significantly larger third order optical nonlinearities for these 
systems compared to known materials and structures. Studies have shown that these 
nonconjugated polymers upon doping show nanometallic type behavior due to the 
  63 
 
formation of quantum dots [29, 31]. This phenomenon of nanometallic like behavior 
can bring out significant change in the specific heat capacity of the doped polymer as 
compared to undoped polymer. The earlier chapters illustrate the similar behavior of 
these quantum dots to the nano metals. The study of thermal properties of nano sized 
particles has shown that they exhibit higher specific capacity than composite bulk 
materials (about 10 to 12 times). In this case, such type of effect of increase in the 
specific heat capacity due to nanometallic like behavior of the polymer is found in 
poly(?-pinene) alone. While in the case of cis-1,4-polyisoprene,                             
trans-1,4-polyisoprene and styrene-butadiene-rubber non metallic effect is dominated 
by iodine and elastomeric properties displayed by these rubber polymers. These 
polymers exhibit nanometal like behavior on doping with iodine. But since these 
polymers are elastic in nature (less rigid) the effect of this nanometallic behavior is 
superseded by iodine (Iodine has low specific heat capacity). Hence when iodine 
dominates the nanometallic behavior of these polymers, we can observe a decrease in 
the specific heat capacity upon doping. These polymers are more elastic unlike 
poly(?-pinene) which is glassy, hard and rigid at room temperature; this also 
influences the thermal properties of the polymer [61, 63-65]. The following table 
shows the change in specific heat capacities of specific nonconjugated conductive 
polymers before and after doping with iodine at 250C. 
 
 
 
  64 
 
 
Nonconjugated 
Polymers 
 
Undoped (J/g0C.) 
 
Doped (J/g0C.) 
PBP 2.025 2.35 
TPI 3.75 2.42 
CIS 2.954  0.72 
SBR 2.42 1.86 
 
Table 7.1 Specific heat capacities of specific NCP iodine doping at 250C. 
 
7.7 Conclusion 
Efforts were done to study the thermal properties of nonconjugated polymers 
including include poly(?-pinene) (PBP), cis-1,4-polyisoprene (CPI),                       
trans-1,4-polyisoprene (TPI) and a copolymer styrene-butadiene-rubber (SBR) before 
and after doping. Thermal properties of the specific nonconjugated polymers before 
and after doping with iodine have been studied for a specific range (-550C to 1100C). 
The effect on the heat flow for specific temperature range (-550C to 1100C) and 
specific heat capacity were discussed. It was observed that specific heat capacity of 
poly(?-pinene) increases upon doping, while in the case of other nonconjugated 
polymer such as cis-1,4-polyisoprene, trans-1,4-polyisoprene and styrene-butadiene-
rubber, the specific heat capacity reduces upon doping at 250C. The reduction in the 
specific heat capacity is found higher in cis-1,4-polyisoprene than trans-1,4-
polyisoprene since the former is found out to be more elastic and its elasticity reduces 
more rapidly upon doping . The increase in the specific heat capacity of poly(?-
pinene) which is glassy at room temperature was attributed to the formation of 
  65 
 
organic quantum dots (similar to nanometallic quantum dots) upon doping. The Tm of 
undoped poly(?-pinene) and trans-1,4-polyisoprene has been found to be at 770C and 
600C respectively. After doping the Tm transition was not clearly observable. In the 
case of styrene-butadiene-rubber and cis-1,4-polyisoprene, no significant transition in 
heat flow was found before and after doping with iodine. Thus line shape of the heat 
flow curves of styrene-butadiene-rubber a cis-1,4-polyisoprene do not change 
significantly upon doping with iodine for the specific rang (-550C to 1100C). More 
detail studies need to be done in this field.  
  66 
 
Chapter 8 
PHOTOVOLTAIC EFFECT IN A COMPOSITE INVOLVING                        
IODINE-DOPED POLY(?-PINENE), A NONCONJUGATED CONDUCTIVE 
POLYMER. 
 
8.1  Introduction 
Energy is a phenomenon which enables human beings to do work. All the day 
to day activities require some sort of energy to perform. In fact energy drives the 
universe. Sun is one of the most humongous sources of energy that we know till now. 
There are two types of energy source namely renewable and nonrenewable. The 
renewable consist of solar energy, wind energy etc where else nonrenewable consist 
of fossil fuels, oil, and petroleum etc.  
However today, the need of exploring new ways to obtain energy from these 
renewable sources has gained attention of many researchers. This need is mainly due 
to the excessive utilization of nonrenewable resources in this modern world. The 
increase in world population is increasing the need for energy. It is estimated that the 
world population will be nearly doubled by the end of the twenty first century which 
will increase energy demand by nearly two times. The world population statistics 
from 1950 and the projected population statistics till 2050 are shown below [86]. 
  67 
 
              
    Figure 8.1 World Population statistics [86] 
The population is projected to increase to 9 billion by 2042, which is nearly 
50% increase from the year 1999 [86]. This would cause an increase in the world 
energy consumption. The world energy consumption from 1980 and the projected 
energy consumption till 2030 are shown below [87, 88]. 
 
Figure 8.2 World Energy Consumption from 1980-2030 [87] 
It is estimated that in 2030 the world energy need is projected to go nearly by       
40%-50% of the present need. At present around 86.5% of the world energy needs are 
supplied through burning fossil fuels [89]. This has resulted into advent of the need 
  68 
 
for exploring energy from the renewable resources. And photovoltaic is one such way 
to generate energy from a renewable source. 
Organic polymers have attracted a great deal of interest in the area of 
photovoltaic. Photovoltaic are a field in which light energy is used to produce electric 
current by movement of free electrons. These materials show promising results and can 
serve as lower cost alternatives to inorganic photovoltaic materials [90]. The first 
two-layer organic photovoltaic system appears to have been reported in 1958 [91].    
Poly (p-phenylene vinylene) (PPV) has been widely studied in the area of organic 
photovoltaic devices [92, 93, 94]. Exploration in the field of photovoltaic devices 
based on polythiopene has also been reported [91]. The incident light is responsible to 
produce electron from such organic materials resulting into generation of electric 
current. Earlier photo-induced electron-transfer between conjugated polymer and C60 
leading to photovoltaic effects have been investigated in detail [95]. 
8.2  Experiment 
Photovoltaic cells used in the report were formed by sandwiching the film of 
doped poly(?-pinene) between two electrodes. The carbon coated on the conducting 
side of tin oxide-coated glass slide was used as one electrode; where else the 
colloidal paste of the mixture of titanium-dioxide (TiO2), acetic acid and triton        
X-100 surfactant was coated on another conducting side of the other tin oxide 
coated glass slide. The film of the involving doped poly(?-pinene) was cast on the 
carbon electrode. The titanium-dioxide electrode was placed on a heater on a heat 
plate for about 20 minutes to get completely dry. Pressure by means of a 
clip was applied to keep the composite and the electrodes in contact. The film 
thickness was about 1 ?m. Films thinner than that were not used in these experiments 
to avoid short-circuit between the electrodes. Carbon electrode was connected to the 
negative terminal of a high impedance electrometer (Keithley 617 Programmable 
  69 
 
Electrometer) and the titanium-dioxide electrode was connected to the positive end of 
the electrometer to measure the photo voltage and photo current.  The titanium-dioxide 
electrode was placed face-up to ensure that the light is incident on the polymer 
through this electrode.  The experimental setup is shown in Figure. 8.3. 
 
 
Figure 8.3: Experimental setup for photovoltaic 
8.3 Results and Discussion: 
 
Figure 8.4: Plot of Intensity vs. Photo-Voltage 
  70 
 
 
Figure 8.5: Plot of Intensity vs. Photo-Current 
 
The graphs were plotted of Figure (8.4) intensity vs. voltage and Figure (8.5) intensity 
vs. current. It current and voltage was observed to increase as the distance of light 
source increases correspondingly. It is mainly because of the fact that the closer the 
light source the intensity of the light absorbs increases which increases the amount of 
released electrons. As the number of electron increase, the photo current increases. The 
photo voltage and photo current produced for a photovoltaic cell involving          
iodine-doped poly(?-pinene) was recorded to increase from 0.24V to 0.55V and               
10?A- 130?A respectively. In this cell involving iodine doped poly(?-pinene) , the 
doped-nonconjugated polymer, iodine-doped poly(?-pinene) acts as an electron hole 
generator due to formation of radical cation and charge transfer between double bond 
to dopant upon doping. When the incident light is absorbed by the polymer, the 
electron hole pairs are produced which transfer the hole to the carbon electrode and 
electrons to iodine and ultimately to titanium dioxide electrode.  This movement of 
electrons and holes are responsible for the observe photo voltage and photo current. 
  71 
 
However further studies on efficiency and current ratings of the cells are under 
progress. 
8.4 Conclusion: 
Photo-induced charge transfer in an iodine doped poly(?-pinene) photovoltaic 
cell is observed for the first time. It is seen that as the intensity of the light increases 
the photo current and photo voltage increases. It is observed that the photo-voltage and 
photo-current increases from 0.24V to 0.55V and 10?A- 130?A respectively. This 
photovoltaic cell finds itself into various fields of applications providing cheaper cost 
in the areas of solar cells, photo-detectors, photo sensors etc.
 
 
Chapter 9  
STUDY OF ABSORPTION COEFFICIENT AND REFRACTIVE INDICES OF 
NONCONJUGATED POLYMERS USING SPECIFIC METHODS 
 
9.1 Introduction  
In optics the refractive index in a medium is the measure of the speed of light in 
that medium [68]. Absorbance, also referred to optical density is due to the light 
absorption that occurs when atoms or molecules take up the energy of a photon of light, 
thereby reducing the transmission of light as it is passed through a sample.  Attenuation 
of light takes place exponentially as it passes through the thickness of the sample and 
depends on the concentration of the absorbing species in the sample [70, 42]. 
Absorbance measurements are often carried out in analytical chemistry, since the 
absorbance of a sample is proportional to the thickness of the sample and the 
concentration of the absorbing species in the sample. Optical absorption coefficient data 
obtained from experimental measurements can be used to calculate refractive indices 
using a Kramers-Kronig relation which is discussed in the following. 
9.2  Result and Discussion 
The relationship between input-output intensities ratio and absorption coefficient 
is given by  
 
 
                                                              
For the calculation convenience, the Absorption coefficient can be deduced from Eqn. 
(9.1) as follows 
                                                
 
where I and I? are output and input intensities  of light  
          ?l? is distance  travel by light,  which is thickness of sample in this case 
The above equation Eqn. (9.2) is used to calculate absorption coefficient from 
absorption data. Optical absorption of nonconjugated co-polymer styrene-butadiene-
rubber has been studied at different doping level with iodine. As discussed earlier in 
chapter 6, the conductivity of styrene-butadiene-rubber increases by many orders of 
magnitude upon doping with iodine. The graphs obtain shows two peaks, one at 3.2 eV 
due to charge transfer from double bond to dopant or iodine, second at 4.27 eV due to 
formation of cation radicals. As the level of doping of iodine increases, the absorption 
peaks increases and as a result strong absorption is recorded. It is mainly because of more 
and more double bond transfer into cation radicals upon increase in the doping level, 
which cause strong absorption and higher absorption coefficient. The figure 9.1 shows, 
wavelength vs. optical density graph corresponding to heavily doped styrene-butadiene-
rubber. Higher the doping stronger is the nanometallic characteristics in nonconjugated 
conductive co-polymer styrene-butadiene-rubber. 
  74 
 
 
Figure 9.1: Absorption coefficient SBR at heavy doping with iodine 
Similar absorption coefficient data was obtained for poly(?-pinene) at heavy doping with 
iodine. The further calculations were done using the expression that relates absorption 
coefficients to the refractive indices. Thus the refractive indices of iodine doped PBP 
have been calculated by numerical integration using Kramers-Kronig transformation, 
which is shown in Eqn. (9.2) 
                     
  
          
 
 
                                   
The Kramers-Kronig relation gives refractive indices as a function of energy. Numerical 
integration was done by using MATLAB software.  The Figure 9.2 shows a plot of 
refractive indices in terms of their respective energies. Also it was observed that 
refractive index at 633 nm (2 eV) is 1.64. 
  75 
 
 
Figure 9.2: Refractive index of heavily doped PBP 
 Refractive indices at specific wavelengths 633 nm for heavily doped               
poly(?-pinene) and styrene-butadiene-rubber have been determined by measuring the 
incident and reflected laser light at different angles of incidence. The incident light was 
polarized parallel and in series to conduct the experiment. Polarized light waves are light 
waves in which the vibrations occur in a single plane. Experiments were carried out using 
thick samples of poly(?-pinene) and styrene-butadiene-rubber on glass slides and were 
heavily doped for a long time. Helium Neon laser was used to carry out the experiment. 
The incident laser beam light was polarized in parallel and in series by holding a 
polarizer in front of the laser. The intensity of the incident beam on the doped samples 
and corresponding intensity of the reflected beam from the doped sample were measured 
and refractive indices were calculated using MATLAB. The following formula was used 
  76 
 
to find out refractive indices at various incident angles on the polymer for series and 
parallel polarization respectively.  
     
                                         
                                        
             Eqn 9.4 
Where   R= |r|2 
The refractive indices for the iodine doped poly(?-pinene) were obtained for 
different angles with different polarization of the incident beams are as follows 
Angle in degrees Refractive index in  
S-polarization 
Refractive index in  
P-polarization 
50 1.81 1.68 
100 1.67 1.69 
150 1.61 1.60 
 Avg = 1.69 Avg =1.65 
 
Table 9.1 Refractive indices for different incident angles for PBP. 
The refractive indices for the iodine doped styrene-butadiene-rubber were obtained for 
different angles with different polarization of the incident beams are as follows. These 
numbers for iodine-doped SBR may not be reliable because of the loss due to surface 
scattering. 
 
  77 
 
 
Angle in degrees Refractive index in  
S-polarization 
Refractive index in  
P-polarization 
50 1.33 1.30 
100 1.32 1.31 
150 1.32 1.32 
 Avg = 1.32 Avg =1.31 
 
Table 9.2 Refractive indices for different incident angles for SBR. 
Refractive Index By Kramers-Kronig 
Relation 
By Reflectivity 
 Experiment 
Iodine doped PBP 1.64 1.67 
 
Table 9.3 Refractive indices of iodine doped PBP at 633nm using               
specific methods. 
9.3 Conclusion  
Refractive indices of doped nonconjugated conductive co-polymers               
poly(?-pinene) has been calculated from absorption coefficients using Kramers-Kronig 
transformation upon high doping with iodine. Very large absorption coefficients and 
corresponding refractive indices have been observed for doped nonconjugated conductive 
co-polymers. Such large absorption coefficients are consistent with subnanometer 
metallic structure. These linear optical constants are vital to determine considering 
exceptionally large Kerr coefficients/third order susceptibilities of this nonconjugated 
 
 
conductive co-polymer. The refractive indices for doped PBP and doped SBR were 
determined as (1.69 and 1.65) and (1.32 and 1.31) for S-polarization and P-polarization 
respectively. Also it was observed that the refractive index at 633 nm (2eV) obtained 
from Kramers-Kronig transformation of absorption coefficient are consistent with the 
measured values. 
 
 
 
                 Chapter 10 
  
                                                                        SUMMARY 
 
The research work performed in this project is summarized in the 
following. Structural studies of the nonconjugated co-polymer                    
styrene-butadiene-rubber have been performed before and after doping with 
iodine. Quadratic electro-optics effect in styrene-butadiene-rubber after doping 
with iodine has been measured at specific wavelengths: 633nm and 1550nm.  
 The optical absorption spectrum of styrene-butadiene-rubber at low 
doping of iodine shows two peaks: one at 4.2eV due to radical cation and the 
other at 3.2eV due to charge-transfer. Doping leads to a reduction of the intensity 
of =C-H bending vibration-band (964cm-1 and 910cm-1) due to formation of 
radical cations upon charge-transfer. Exceptionally large Kerr coefficients as 
measured 3.1x10-10 m/V2 at 633nm and 1.2x10-10 m/V2 at 1550nm are 
exceptionally large and have been attributed to the subnanometer size metallic 
domains (quantum dots) formed upon doping and charge-transfer. 
 Thermal properties of the specific nonconjugated polymers before and 
after doping with iodine have been studied for a specific range (-550C to 1100C) 
using differential scanning caloriemeter. It was observed that specific heat 
capacity of          poly(?-pinene) increases upon doping, while in the case of other 
nonconjugated polymer such as cis-1,4-polyisoprene, trans-1,4-polyisoprene and 
 
 
styrene-butadiene-rubber, the specific heat capacity reduces upon doping. The 
difference has been attributed to the fact poly(? pinene) is glassy at room 
temperature while the others are partly or totally elastomeric. The Tm of undoped 
poly(?-pinene) and trans-1,4-polyisoprene has been found to be at 770C and  600C 
respectively. After doping the Tm transition was not clearly observable. In the 
case of SBR and cis-1,4-polyisoprene, no significant transition in heat flow line-
shape was found before and after doping with iodine.  
  The reflectivity of iodine doped poly(?-pinene) and styrene-butadiene-
rubber was calculated to be approximately 1.67 and 1.31 approximately. Also the 
refractive indices obtained from Kramer-Kronig transformation and 633 nm 
specific wavelength reflectivity experiments at approximately 633nm (2eV) were 
found to be approximately same (1.64 and 1.67). Photovoltaic effect in a 
composite involving nonconjugated conductive polymer; poly(?-pinene) (PBP) 
has been studied. Efforts were made to increase efficiency of photovoltaic cells by 
involving iodine doped specific nonconjuagted polymer poly(?-pinene) 
sandwiched between the two electrodes 1) Mixture of titanium dioxide, Triox-X 
and acetic acid and 2) carbon. However further research work has to be done in 
the field of refractive indices and photovoltaic involving doped specific 
nonconjugated polymers. Overall structural, optical, thermal, photovoltaic and 
quadratic electro-optic characteristics of specific nonconjugated conductive 
polymers including the co-polymer styrene-butadiene-rubber have been studied.
81 
 
BIBLIOGRAPHY 
 
1. M. Samoc, A. Samoc, B. Luther-Davis, Z. Bao, L. Yu, B. Hsieh, U. Scherf, J. 
Opt. Soc. Am. B 15 (1998) 817. 
2. P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical Effects in 
Molecules and Polymers, John Wiley & Sons, Newyork, 1991. 
3. R.W. Munn, C.N. Ironside, Principles and Applications of Nonlinear Optical 
Materials, Blackie Academic & Professional, USA, 1993. 
4.  J.M. Ballesteros, R. Serna, J. Solis, C.N. Afonso, A.K. Petford-Long, D.H. 
Osborne, R.F. Haglund Jr., Appl. Phys. Lett. 71 (1997) 2445. 
5. M Born and E Wolf. Principles of optics: electromagnetic theory of 
propagation, interference and diffraction of light. Cambridge University Press, 
1999. 
6. D L Sengupta and T K Sarkar. Maxwell, Hertz, the Maxwellians and the early 
history of electromagnetic waves, volume 1. 2001. 
7. G. P. Agrawal and R. W. Boyd,?Contemporary Nonlinear Optics?, Academic 
Press, 1992. 
8. R. W. Boyd. Nonlinear Optics. Academic Press, 2003. 
82 
 
9. Y R Shen. The Principles of Nonlinear Optics. John Wiley and Sons, Newyork, 
1984. 
10. E G Sauter. Nonlinear optics. Wiley-Interscience, 1996. 
11. A Yariv and P Yeh. Optical waves in crystals. Wiley New York, 1984. 
12. N Bloembergen. Nonlinear optics. World Scientific, 1996. 
13. R Paschotta. Encyclopedia of laser physics and technology. Vch Pub,2008. 
14. H S Nalwa and S Miyata. Nonlinear optics of organic molecules and polymers. 
CRC press, 1997. 
15. Mansoor Sheik-Bahae and Michael P. Hasselbeck, Department of Physics and 
Astronomy, University of New Mexico, Albuquerque, New Mexico ?Third 
order non-linear properties?  
16. Ananthakrishnan Narayanan ?Electrical and Nonlinear Optical Studies of 
Specific Organic Molecular and Nonconjugated Conductive Polymeric 
Systems.?  
17. P Weinberger. Philosophical Magazine Letters, 8(12): 897?907, 2008 
18. Alfa Aesar  ?Nonlinear Optical Materials?  
19.  L. R. Dalton, et.al., Chem. Mater., 1995, 7, 1060 
20.  (a) F. Pan, et.al., Appl. Phys. Lett., 1999, 74, 492; (b) T. Kaino, et.al., Adv. 
Funct. Mater. , 2002, 12, 599; (c) W. Geis, et.al., Appl. Phys. Lett., 2004, 84, 
3729; (d) F.  Pan, et.al. , Appl. Phys. Lett., 1996, 69, 13; (e) U. Meier, et.al., J. 
Appl. Phys., 1998, 83, 3486.  
21.  (a) L. R. Dalton, Pure Appl. Chem., 2004, 76, 1421.Y. Shi, et.al., Science, 
2000, 288, 119; (b) L. R. Dalton, et.al., Adv. Mater., 2002, 14, 1339. 
83 
 
22.  P A Franken; A E Hill; C W Peters; G Weinreich. Phys. Rev. Lett., 7: 118, 
1961. 
23. P D Marker; R W Terhune; M Nisenoff; C M Savage. Phys. Rev. Lett., 8: 21, 
1962. 
24. J A Giordmaine. Phys. Rev. Lett., 8: 19, 1962. 
25. G D Boyd; C K N Patel. Appl. Phys. Lett., 5: 234, 1964. 
26. P M Rentzepis; Y H Pao. Appl. Phys. Lett., 5: 156, 1964. 
27. G H Heilmeir; N Ockman; R Braunstein; D A Kramer. Appl. Phys. Lett., 5: 
229, 1964. 
28.  Ch Bosshard; K Sutter; P Pretre; J Hulliger; M Florsheimer; P Kaatz; P Gunter. 
Advances In Nonlinear Optics. Gordon and Breach Publishers, 1995. 
29. M. Thakur, ?A class of conducting polymers having nonconjugated backbones?   
Macromolecules, 21 (3), pp 661?664, 1988. 
30. H Rajagopalan; P Vippa; M Thakur. Appl. Phys. Lett., 88: 033109/1, 2006. 
31. M. Thakur, ?Nonconjugated conductive polymer? J. Macromol. Sci., Pure Appl. 
Chem., A38 1337, 2001. 
32. M. Thakur, R. Swamy. and J. Titus, ?Quadratic Electrooptic Effect in a 
Nonconjugated Conductive Polymer? Macromolecules, 37 (8), pp 2677?2678, 
2004. 
33. Found at internet address: http://www.wcaslab.com/tech/tbftir.htm 
34. P. S. Kalsi, ?Spectroscopy of Organic Compounds? New Age International, 
2007 
84 
 
35.  George Socrates, ?Infrared and Raman characteristic group frequencies: tables 
and charts?, John Wiley and Sons, 2004. 
36. Jitto Titus ?Studies of the off-resonant nonlinear optical properties of an organic 
molecular crystal and specific nonconjugative polymers ?. 
37. PFEN 3100 (Polymer Engineering) at Auburn university ?Fundamentals of 
polymer?. 
38. SII Nanotechnology, ?Specific Heat Capacity Measurement Using DSC-I? 
Japan (1981) 
39. Bu-Xuan Wang, Le-Ping Zhou, Xiao-Feng Peng, ?Surface and Size Effects on 
the Specific HeatCapacity of Nanoparticles? International Journal of 
Thermophysics, Vol. 27, No. 1, 139-151, (2006). 
40.  Hugh D. Young, Roger A. Freedman, University Physics, Addison-Wesley 
(2008). 
41.  Wolfram Research "Index of Refraction - from Eric Weisstein's World of 
Physics" 
42. Found at internet address: Rudlger Paschotta , ?Encyclopedia of Laser Physics 
and Technology?  http://www.rp-photonics.com/refractive_index.html 
43. V. Deiogio, Christos Flytzanis, ?Nonlinear optical Materials: Principle and 
Applications?, Varenna on Lake Como, 1993. 
44.  D.C. Hutchings et al., ? Kramers-Kronig in nonlinear optics?, Opt. Quantum 
Electron. 24, 1, 1992. 
45. Joseph Habib Simmons, Kelly S. Potter, ?Optical materials? 2000. 
85 
 
46. V. Deiogio, Christos Flytzanis, ?Nonlinear optical Materials: Principle and 
Applications?, Varenna on Lake Como, 1993.  
47. D.V.G.L.N. Roa, P.Wu, B.R. Kimball, M. Nakashima, B.S. Decristofano, 
?Trends in Optics and Photonics?, 63, WB4/1- WB4/3, 2001. 
48. Found at internet address: http://www.rp-photonics.com/encyclopedia.html. 
49. P. Vippa, H. Rajagopalan, M. Thakur, ?Electrical and Optical Properties of a 
Novel Nonconjugated Conductive Polymer, Poly(?-pinene)?, J Polym. Sci. Part 
B: Polym. Phys. 43: 3695?3698, 2005. 
50. A. Narayanan and M. Thakur, Solid State Comm., 150, 375, 2010. 
51. S. Shrivastava, and M. Thakur ?Quadratic electro-optic effect in the 
nonconjugated conductive polymer iodine-doped trans-polyisoprene, an organic 
nanometallic system?, Solid State Communication, 2011. 
52.  Li, W. R.; Xie, X. B.; Shi, Q. S.;, Zeng, H. Y.;, Ou-Yang, Y. S.; Chen, Y. B. 
Appl Microbiol Biotechnol, 85(4), 1115-22, 2010. 
53. Lubick, N. Environ. Sci. Technol., 42 (23), 8617, 2008. 
54. S. L. Hsu, A. J. Signorelli, G. P. Pez, and R. H. Baughman, J. Chem. Phys., 
69,1978 106. 
55. Stephan Link and Mostafa A. El-Sayed, ?Size and Temperature Dependence of 
the Plasmon Absorption of Colloidal Gold Nanoparticles? J. Phys. Chem. B, 
103, 4212-4217, 1999. 
56.  Jirakorn ThisayuktaY, Hiroyuki Shiraki, Yoshio Sakai, Takenori Masumi, 
Sudarshan Kundu, Yukihide Shiraishi, Naoki Toshima and Shunsuke 
Kobayashi,?Dielectric Properties of Frequency Modulation Twisted Nematic 
86 
 
LCDs Doped with Silver Nanoparticles?, Japanese Journal of applied physics, 
Vol. 43, 5430-5434, 2004. 
57.  R.H. Magruder III, Li Yang and R.F. Haglund Jr, ?Optical properties of gold 
nanocluster composite formed by deep ion implantation in silica?, Appl. Phys. 
Lett. 62(15), 1730-1732, 1993. 
58.  H. H. Huang, F. Q. Yan, Y. M. Kek ?Synthesis, Characterization, and 
Nonlinear Optical Properties of Copper Nanoparticles? Langmuir, 13, 172-175, 
1997. 
59. Hideyuki Inaiye, Koichiro Tanaka ?Femtosecond optical Kerr effect in Gold 
Nanopartical system?,  Jpn. J. Appl. Phys. Vol-37, L1520-1522, 1988. 
60. Seong-Min Ma1, JaeTae Seo1, WanJoong Kim ?Cubic Nonlinear Optical 
Properties of Ag Nanoparticles and Ag/Au Coreshells?, Journal of Physics: 
Conference Series 109 (2008). 
61. Found at internet address: Thermal analysis of Rubber. 
http://www2.shimadzu.com/applications/thermal/t115.pdf 
62. M. Thakur and B.S. Elman, J. Chem. Phys., 90 (1989) 2042 
63. Ernesto L Rodriguez, Frank Filisko Department of Materials and Metallurgical 
Engineering, Macromolecular Research Center. ? Thermal effects in Styrene-
butadiene rubber at high hydrostatics pressure? 1986 
64. Treloar, ?The physics of Rubber Elasticity? 
65. I. Franta,? Elastomers and Rubber compounds?. 
87 
 
66. Found at internet address: 
http://www.sigmaaldrich.com/catalog/product/aldrich/182141?lang=en&region
=US&cm_sp=Customer_Favorites-_-Detail_Page-_-Text-182141 
67. J. Titus and M. Thakur, Appl. Phys. Lett., 90 (2007) 121111. 
68. Index of Refraction - from Eric Weisstein's World of Physics" Wolfram 
Research.     Found at internet address: 
http://scienceworld.wolfram.com/physics/ 
69. R. Swamy, H. Rajagopalan, P. Vippa, M. Thakur, A. Sen, Solid State Comm., 
143 (2007) 
70. Found at internet address: http://www.turnerdesigns.com/t2/doc/appnotes/S-
0075.pdf 
71. Mark S. M. Alger, Polymer Science Dictionary  
72. ?FTIR spectra and mechanical strength analysis of some selected rubber 
derivatives?      S. Gunasekaran, R.K. Natarajan, A. Kala 
73. N. Vasanthan and A. E. Tonelli, ?FTIR investigation of the inclusion compound 
formed between trans-1,4-polyisoprene and urea?, Polymer,  Vol. 36 No. 25, pp. 
4887-4889, 1995. 
74.  Arthur E. Wooward, N. Vasanthan, and Joseph P. Corrigan, ?Infra red 
spectroscopic investigation of bulk crystallized trans-1,4-polyisoprene?, 
Polymer, Vol.34  No.11, 1993.  
75. V. Arjunan a, S. Subramanian a, S. Mohan ?Fourier transform infrared and 
Raman spectral analysis of trans-1,4-polyisoprene? Spectrochimica Acta Part A 
57, 2547?2554,  2001. 
88 
 
76. G. Nimitz, A. Enders, P. Marquardt, R. Pelster and B. Wessling, Synth. Met., 45 
(1991)197. 
77. K. Uchida, S. Kaneko, S. Omi, C. Hata, H. Tanji, Y. Asahara, and A. J. 
Ikushima, J. Opt. Soc. Am. B, 11 (7) (1994) 1236. 
78. ?Semiconductor and Metal Nanocrystals?, ed. V.I. Klimov, Marcel Dekker, 
New York, 2004, pp.422-431. 
79. Bu-Xuan Wang, Le-Ping Zhou,  Xiao-Feng Peng, ?Surface and Size Effects on 
the Specific HeatCapacity of Nanoparticles? International Journal of 
Thermophysics, Vol. 27, No. 1, 139-151, (2006) 
80. J. Rupp, R. Birringer, ? Enhanced Specific Heat Capacity (Cp) measurements 
(150-300K) of nanometer-sized crystalline materials?, Physical Review B Vol. 
36, 1987 
81. Differential Scanning Calorimetry, second and third order transitions in 
polymers http://www.colby.edu/chemistry/PChem/lab/DiffScanningCal.pdf 
82. SII Nanotechnology, ?Specific Heat Capacity Measurement Using DSC-I? 
Japan (1981) 
83. Huafeng Shao, Baochen Huang, Wei Yao, Haixia Li,  ?Synthesis and 
characterization of low relative molecular weight trans-1,4-poly(isoprene)? 
Journal of Applied Polymer Science, Vol. 107, Issue 6, pages 3734?3738, 2008 
84. Edward G. Lovering, David C. Wooden, ?Equilibrium Melting points of the 
Low melting and High melting Crystalline Forms of trans-1,4-polyisoprene ? 
Journal of Polymer Science Part A-2, Vol.9, 175-179, 1971 
89 
 
85. An-Long Li, Xiao-Yan Wang, Hui Liang, Jiang Lu ?Controlled Radical co-
polymerization ?-Pinene and n-butyl acrylate? 2006 
86.  U.S. Census Bureau, International Data Base, 2008 First Update 
87. History: Energy Information Administration (EIA), International Energy 
Annual 2004 (May-July 2006)  
88. Projections: EIA, System for the Analysis of Global Energy Markets (2007) 
89. World Consumption of Primary Energy by Energy Type and Selected Country 
Groups, 1980-2004. Energy Information Administration, U.S. Department of 
Energy (July 31, 2006). Retrieved on 2007-01-20. 
90.  Kearns D. R, Calvin M, J. Chem. Phys., 29, (1958), pp. 950 
91.  Paul A. Lane and Zakya H. Kafafi, Solid-state Organic Photovoltaic: A review 
of Molecular and Polymeric Devices, Naval Research Laboratory, Washington, 
D.C.,USA 
92. Glenis S., Horowitz G., Tourillon G., Garnier, F., Thin solid Films, 111(2), 
(1984),pp. 93-103 
93. Fang Y., Chen S. A., Chu M. L., Synth. Met., 52(3), (1992), pp. 261-272 
94. Horowitz G., Garnier F., Sol. Energy Mater., 13(1), (1986), pp. 47-55. 
95.  A Palthi , A Narayanan , M Thakur  ?Photovoltaic Effect in a Composite 
involving the Nonconjugated Conductive Polymer, Poly(?-pinene) and C60 ?