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

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-PM A) diblock copolymers. Initiator synthesis involved reaction of methyl 3,3-dimethy1-4-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). 1B2BP 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 center dot 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 < I-eff < 0.80) at low temperature (-70 degrees C) and low monomer/initiator ratio (82). Higher cationic initiation efficiency (0.80 < elf < 0.90) was observed when temperature was increased to 50 degrees C and/or the monomer/initiator ratio was increased. In spite of low /err, the resulting PI Bs had narrow polydispersity, and each chain contained one intact 2-bromopropionyl head group, which was subsequently used for ATRP of methyl acrylate. Efficiency of radical initiation was very high, and targeted PMA block lengths were obtained.