Synthesis, Characterization, and Properties of Starlike Poly(<i>n</i>-butyl acrylate)-<i>b</i>-poly(methyl methacrylate) Block Copolymers

Abstract

A series of 10- and 20-arm starlike block copolymers containing inner soft poly(<i>n</i>-butyl acrylate) (PBA) block and outer hard poly(methyl methacrylate) (PMMA) block were synthesized by atom transfer radical polymerization (ATRP). Short macroinitiators for preparation of starlike copolymers, poly(2-bromoisobutyryloxyethyl acrylate) (PBiBEA) with degree of polymerization DP = 10 and 20, was prepared by ATRP of trimethylsilyloxyethyl acrylate (HEATMS) and subsequently esterified. Partial star coupling during the star extension with PMMA blocks was observed, and the coupling increased with increasing number of arms and arm length. Phase-separated morphologies of cylindrical hard PMMA block domains arranged in the soft PBA matrix were observed by atomic force microscopy and small-angle X-ray scattering. The mechanical and thermal properties of the copolymers were also thoroughly characterized, and their thermoplastic elastomer behavior was studied. Tensile strength of the starlike copolymers was considerably higher compared to linear and three-arm stars with similar compositions.