Molecular Bonding in Product Engineering

Abstract

Molecular Bonding plays an important role in the performance of product and chemical processes. Various types of bonds are: ionic bond, covalent bond, co-ordinate bond, metallic bond, van der Waal’s bond and hydrogen bond. This dissertation involves examination of hydrogen bonds, covalent bonds and van der Waal’s bonds in order to improve performance of a wide variety of products in the present commercial world: liquid crystal display in computers and laptops, and sustained release formulations in Pharmaceutical Drug Delivery. Current challenges in the product performance are examined and then improvements in the product performance from a perspective of molecular bonding are proposed. The most important factors that play a major role in molecular bonding are the intermolecular forces and intermolecular distances. By developing a fundamental understanding and means of enhancing the strength of these bonds, product improvement can be achieved for a better overall performance.

In liquid crystal displays (LCDs) the active element is a liquid crystal matrix with several dichroic dyes dissolved in them. The liquid crystal molecule responds to the change in the electric field (i.e., pixel switching), whereas the dye molecule exhibits optical absorption. For fast optical switching of the pixels, hydrogen bond between the liquid crystal molecule and dichroic dyes plays an important role. A strong hydrogen bond between the two enhances the contrast properties of the LCDs. This depends upon finding the right combination of liquid crystal and dichroic dye molecules that exhibits strong hydrogen bonding along the longitudinal length of the molecule. Strengths of h-bonding are examined using both Fourier transform infrared spectroscopy, and molecular modeling and simulation. In controlled drug release applications, drug is encapsulated in polymer microspheres, and the drug release occurs by the biodegradation of the polymer. A current challenge is due to too much drug release (burst release) during the first day itself, causing the drug level to rise above the toxic limits. To address this challenge, surface covalent bonds are added to the drug/polymer microspheres. This surface covalent bonding is carried out by polymerization of crosslinkable monomers by UV light. The surface layer imparts additional mass transfer barrier to the drug release, thereby reducing the initial burst release. Both hydrophilic and hydrophobic types of drugs are tested and reduction in initial burst release was obtained. A further step into the development of sustained release formulations involves microencapsulation of active pharmaceutical ingredients (API) nanoparticles in solid form into biodegradable polymer microparticles. These particles are built on the basis of van der Waal’s forces of attraction between the polymer strands and the API nanoparticles and amongst themselves. This helps in creating a uniform distribution of the API in the polymer matrix and therefore provides a sustained release of the API for a long period of time with almost no burst release. An extension of this process is towards utilizing the above process for sustained release formulations of proteins and peptides.