Abstract
Access to well-defined (high degree of structural, molecular weight and compositional homogeneity) polyethylenes (PEs) and PE-based copolymers is necessary in order to elucidate the structure-properties relationships and evaluate potential applications. Recently, Shea developed a novel polymerization methodology leading to perfectly linear PEs. The general reaction scheme involves the formation of an organoboron zwitterionic complex between a methylide (monomer, anion) and a trialkylborane Lewis acid (activator/initiator) which breaks down by the intramolecular 1,2-migration. As a consequence, the activated methylene group of methylide is randomly inserted one by one into the three branches of the trialkylborane leading to a 3-arm PE star. The resulting star is subsequently oxidized/hydrolysed to give perfectly OH-end-capped linear PEs. Our group is developing both novel borane initiators and ylide monomers and combines polyhomologation with other living polymerizations to synthesize model polymethylene (or PE)-based polymeric materials.