New Dual Initiators To Combine Quasiliving Carbocationic Polymerization and Atom Transfer Radical Polymerization

Abstract

New dual initiators, 3,3,5-trimethyl-5-chlorohexyl 2-bromopropionate (IB2BP) and 3,3,5-trimethyl-5-chlorohexyl 2-bromo-2-methylpropionate (IB2BMP), which contain initiating sites for both carbocationic polymerization and atom transfer radical polymerization (ATRP), were synthesized and used to create poly(isobutylene-b-methyl acrylate) (PIB-b-PMA) diblock copolymers. Initiator synthesis involved reaction of methyl 3,3-dimethyl-4-pentenoate with 2 equiv of methylmagnesium bromide, followed by hydroboration−oxidation of the double bond to yield 1,5-dihydroxy-3,3,5-trimethylhexane (DHTMH). IB2BP was synthesized by reaction of the primary hydroxyl group of DHTMH with 2-bromopropionyl bromide, followed by chlorination of the tertiary hydroxyl group with anhydrous HCl. IB2BMP was synthesized analogously using 2-bromo-2-methylpropionyl bromide. Both initiators displayed slow cationic initiation of isobutylene, leading to moderate initiation efficiencies (0.50 < Ieff < 0.80) at low temperature (−70 °C) and low mo...