This Is AuburnElectronic Theses and Dissertations

Multicomponent Polymer Systems: Polymer Compositional Analysis using Low-Field 1H-NMR Spectroscopy and Tuning the Compositional Drift in Styrene/Isoprene Anionic Copolymerizations




Bukkapatna Chakrapani, Sneha

Type of Degree

Master's Thesis


Chemical Engineering


This Thesis investigates multicomponent polymer systems in the context of their characterization and their synthesis. The composition of the different polymers comprising multicomponent polymer systems is a vital variable in tuning their properties. Herein, low-field 1H NMR Spectroscopy (60 MHz), a newly commercially available technology, is inspected as a possible low-cost alternative to the significantly more expensive (in terms of capital and maintenance costs) higher-field NMR spectrometers (> 250 MHz) for the compositional analysis of multicomponent polymer systems, namely polymer blends and block copolymers. The results from a low-field spectrometer are corroborated using a high-field spectrometer and are found to be adequately quantitative within the typical confidence for compositional analyses of this nature using traditional high-field NMR spectroscopy. Next, a series of copolymers of styrene and isoprene are synthesized by anionic copolymerization using a co-solvent mixture of cyclohexane and triethylamine, of varied relative compositions to probe the impact on compositional drift (statistical composition along the polymer chain). Copolymerization reactions are monitored online using in-situ Attenuated-Total-Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to obtain monomer conversions as well as overall conversions in order to completely describe the copolymer compositional profiles. Compositional drift profiles are used to extract reactivity ratios using the Beckingham-Sanoja-Lynd approach to define the copolymer architecture and as a quantitative means of comparison. Conclusively, this system allows for the tuning of copolymer compositional profiles as desired with potential applications in designing polymer architectures with desired properties.