Abstracts Chemistry

Novel Modifications of Styrene-Butadiene and Isoprene Rubber

by Nathan David Schmitz

Novel modifications of styrene-butadiene rubber were studied using conventional curatives, sulfur curing packages or peroxides, to efficiently utilize supramolecular reinforcement strategies that improve the mechanical properties of rubber. Thiol-ene coupling proved to be an effective method for modifying styrene-butadiene rubber during peroxide curing, but it was inadequate when attempted during sulfur vulcanization.Supramolecular reinforcement was achieved by grafting mercapto-functionalized sodium phosphate esters to styrene-butadiene rubber during peroxide curing which electrostatically associate. The association strength between these ionic grafts played a critical role in determining the degree of reinforcement. Possible mechanisms by which reinforcement occurs were discussed and, at low grafting densities, at least one mechanism was determined not to play a major role. It was shown that substantial modification of cis-1,4-polyisoprene does not occur by thiol-ene coupling and that another chemical means must be used to modify this substrate.Reagents consisting of thioaldehydes derived from thiosulfinates were used in Alder-ene reactions to modify cis-1,4-polyisoprene. Based on this chemistry, new grafting and crosslinking agents were developed that react quickly and at relatively low temperatures. Important elements in the molecular design of these curatives were discussed and it was demonstrated that good mechanical properties are attainable.