An Experimental and Theoretical Study of the Synthesis of Bioninspired Copololymers of Vinylbenzylthymine and Vinyl triethylammnonium Chloride

Abstract

‘Bioinspired’ copolymers based on vinylbenzyl thymine (VBT) and an ionically-charged monomer, such as vinylbenzyl triethylammonium chloride (VBA), were synthesized and theoretically investigated. These watersoluble copolymers are polystyrene (PS)-based, and their structure mimics DNA. In the presence of shortwavelength UV light, the thymine groups dimerize into non-toxic, environmentally benign, and biodegradable photo-resist materials. Copolymerizations with different comonomer ratios were carried out at 658C. Samples were taken along the reactions to determine monomer conversion, chemical composition, and molecular weight distribution. While average molecular weights fall along the reaction, the average composition remains almost constant and coincident with the initial comonomer ratios, thus indicating a similar reactivity of all the comonomer radicals. The developed mathematical model simulates the synthesis of the base biopolymer, in the sense of predicting the evolution of the global reaction variables and molecular structure of the polymer. The termination and propagation kinetic constants were adjusted to the experimental data. The resulting values are quite different to those of a normal styrene homopolymerization, thus suggesting a noticeable effect between the solvent and the comonomer pending groups.