Functional Imidazolium Ionomer Derivatives of Isobutylene-Rich Elastomers

Macromolecules containing small amounts of ionic functionality, collectively known as ionomers, are valued for their exceptional physical properties, antimicrobial activity, and superiour adhesion to high surface energy solids and polymer blend components.  Most commercial ionomers are carboxylate or sulfonate derivatives of ethylene-rich thermoplastics, but elastomeric ionomers bearing quaternary ammonium and phosphonium halide functionality have been described in both the scholarly and the patent literature.  Of current interest are cationic ionomers prepared by halide displacement from brominated poly(isobutylene-co-isoprene), or BIIR, using imidazoles that bear reactive functionality.  Alkylation of nucleophiles such as N-vinyl imidazole and N-(trimethoxysilyl propyl) imidazole by BIIR yields imidazolium bromide salts that are thermally stable, yet capable of supporting free radical cures and/or siliceous filler dispersion by further chemical modifications.  As such, this class of reactive imidazolium ionomers promises to support new, value-added applications for butyl rubber and its analogues.