| Substitution reactions with phosphorus- and oxygen-centered nucleophiles have been conducted to prepare derivatives of brominated poly(isobutylene-co-isoprene) (BIIR). The characterization of the polymeric products has been accomplished through structural analyses of low molecular weight analogues synthesized from brominated 2,2,4,8,8-pentamethyl-4-nonene (BPMN). Derivatizations both in solution and under solvent-free conditions have been performed and, in some cases, principles of phase transfer catalysis (PTC) have been employed to overcome reagent immiscibility.; Phosphonium bromide and phosphonate derivatives of BIIR have been prepared from triphenylphosphine and tributyl phosphite, respectively. These trivalent phosphorus compounds do not promote side reactions. Instead, they participate in bromide displacement reactions that can occur in the absence of solvent. The potential use of Wittig chemistry under PTC conditions to further modify the phosphonium bromide derivative of BIIR has been explored but the reaction has been found to occur only under very specific conditions.; Elastomers with ether and ester functionalities have been generated by conducting substitution reactions of BIIR with alkoxide and carboxylate salts. While the former derivatizations were conducted in solution, a new solvent-free PTC procedure was developed to prepare both aliphatic and aromatic esters of BIIR. This procedure involves the activation of alkali metal salts with catalytic amounts of quaternary ammonium halides using conventional polymer processing equipment. The high reactivity of the allylic bromide sites within BUR has been also exploited to prepare isobutylene-based graft copolymers. It is demonstrated that polymer-polymer coupling between BIIR and mono-functionalized polymers can take place in solution under relatively mild conditions. |
