Atom Transfer Radical Copolymerization of Styrene and n-Butyl Acrylate

Abstract

Styrene and n-butyl acrylate were copolymerized by atom transfer radical polymerization catalyzed by CuBr/4,4‘-di(5-nonyl)-2,2‘-bipyridine. Composition was consistent with a simple terminal model analysis and was independent of [CuBr]0, [I]0, and temperature for copolymerizations with initial feed content of styrene (fst)0 = 0.510. Monomer reactivity ratios evaluated from experimental data by nonlinear least-squares calculations were 0.68 ≤ r1 ≤ 0.82 and 0.22 ≤ r2 ≤ 0.26. 13C NMR spectra of styrene/n-butyl acrylate copolymers were very similar to copolymers prepared through conventional radical polymerizations, indicating that carbon-centered free radicals were generated under these conditions. Conversion/molecular weight plots showed no evidence of transfer, though measured molecular weights were consistently higher than theoretical ones. Semilogarithmic plots of monomer conversion versus time were nonlinear, indicating an irreversible termination reaction whose contribution decreases with decreasing temperature. Polymerizations of styrene in n-butyl propionate (a nonpolymerizable model for n-butyl acrylate) were also nonlinear, suggesting that end group decomposition of styrene units was enhanced by the presence of n-butyl acrylate.