Atom Transfer Radical Polymerization of tert-Butyl Acrylate and Preparation of Block Copolymers

Abstract

Atom transfer radical polymerization (ATRP) of tert -butyl acrylate is reported. Controlled polymerizations were performed using a CuBr/ N,N, N ‘, N ‘ ‘, N ‘ ‘-pentamethyldiethylenetriamine catalyst system in conjunction with an alkyl bromide as the initiator. Low molecular weight polymers with narrow molecular weight distributions were obtained by the addition of a solvent to create a homogeneous catalytic system. The addition of the solvent was necessary to decrease the polymerization rate and afford low polydispersity materials. This differs from the ATRP of methyl or n -butyl acrylate using this catalytic system, which do not require the addition of a solvent to obtain well-defined polymers. Subsequent hydrolysis of the polymer in refluxing dioxane with addition of HCl afforded poly(acrylic acid). Characterization using 1 H NMR and FT-IR confirmed complete hydrolysis of the ester group. Further use of poly( tert -butyl acrylate) as a macroinitiator for block copolymerizations followed by hydrolysis of the ester group produced amphiphilic block copolymers. In addition, the preparation of an ABC triblock copolymer of poly( tert -butyl acrylate)- b -poly(styrene)- b -poly(methyl acrylate) by ATRP is reported.