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

Document Type

Article

Publication Date

9-14-2010

Department

Polymers and High Performance Materials

Abstract

New dual initiators, 3,3,5-trimethyl-5-chlorohexyl 2-bromopropionate (IB(2)BP) and 3,3,5-trimethyl-5-chlorohexyl 2-bromo-2-methylpropionate (IB(2)BMP), 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 IB(2)BMP 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.

Publication Title

Macromolecules

Volume

43

Issue

17

First Page

7048

Last Page

7055

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