Chemical modification of brominated poly(isobutylene- co-isoprene): Elimination and cycloaddition chemistry and substitution reactions wiht carboxylate nucleophiles

Butyl rubber is a random copolymer of isobutylene and isoprene. Consisting primarily of isobutylene (∼98 mole %), butyl rubber exhibits extremely low permeability, excellent chemical resistance, and its isoprene subunits enable it to form a covalently crosslinked network. Bromination of butyl rubber yields a value-added material that contains a highly reactive allylic bromide functional group. In addition to increasing the rate of sulfur cures, allylic bromide functionality provides a synthetic route for further chemical modification of brominated butyl rubber (BIIR).;The first objective of this research project was to study the solid-state and solution dehydrobromination of BIIR. The second objective was maleation of the exo-conjugated diene generated from dehydrobromination, followed by a feasibility study into alcoholysis reactions with this bicyclic anhydride. The third objective was to study the kinetics of nucleophilic substitution reactions on BIIR using carboxylate nucleophiles and phase-transfer catalyzed by tetrabutylammonium bromide. This area of research was extended to the synthesis, purification, and transmission electron microscopy analysis of a graft copolymer synthesized from the nucleophilic substitution of BIIR and carboxylic acid terminated polybutadiene.;BIIR was reacted in a xylenes solution at reflux to yield a high conversion of total allylic bromide to exo-conjugated diene. Crosslinking, fragmentation, and rearrangement reactions were successfully mitigated through the efficient removal of HBr by an appropriate acid scavenger. Cycloaddition of maleic anhydride to exo-conjugated diene generated the bicyclic anhydride product in quantitative yield at low temperatures. Alcoholysis of this product by dodecanol proved to be a kinetically slow process when performed in solution, but proceeded readily in the solid-state. BIIR-g-PE (11%) was successfully synthesized after a 120 h solution reaction.;Stearic acid was selected to assess the kinetics of bromide displacement from BIIR by carboxylate nucleophiles. Tetrabutylammonium bromide was an effective phase-transfer catalyst, supporting allylic-ester formation at rate that was independent of initial stearic acid concentration. This reaction can be extended to polymer-polymer coupling to prepare copolymers of butyl rubber and polybutadiene. The phase partitioning behaviour of the copolymer was assessed by transmission electron microscopy (TEM). Higher weight fractions of polybutadiene in the copolymer resulted in a significant increase in BR domain size.