Toughening of an epoxy thermoset with poly[styrene-alt-(maleic acid)]-block-polystyrene-block-poly(n-butyl acrylate) reactive core–shell particles

Abstract

A series of tailored reactive core–shell particles (RCSPs), structurally core-crosslinked reactive block copolymer micelles, were synthesized via reversible addition–fragmentation chain transfer (RAFT) miniemulsion polymerization mediated by an amphiphilic macro-RAFT agent. The core–shell structures of RCSPs were confirmed by SEC, DSC, and TEM observations. The particle sizes of RCSPs were all in unimodal distributions according to DLS measurement. The designed RCSPs were then blended with epoxy resin. RCSPs with 8 wt% more reactive segments were found to be well-dispersed in the cured epoxy matrix in the scale of pre-existing core–shell particles. By considering the similar RCSP particle size and RCSP volume fraction in the epoxy matrix, it was judged that the reactive segment of RCSPs played a key role in toughness improvement. It was noted that the epoxy blends are significantly toughened by RCSPs in terms of the measurement of the critical stress field intensity factor (K_IC).