Synthesis and Redispersibility of Poly(styrene-block-n-butyl acrylate) Core–Shell Latexes by Emulsion Polymerization with RAFT Agent–Surfactant Design

Abstract

A coagulatable and redispersible poly(styrene-block-n-butyl acrylate) (PS-b-PnBA) copolymer latex system was developed. A series of PS-b-PnBA diblock copolymers with the PnBA content up to 70 wt % were prepared via a reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization. An amphipathic poly(acrylic acid-b-styrene) trithiocarbonate was synthesized and employed as macro-RAFT agent and surfactant. The resulted latex particles contained a soft poly(n-butyl acrylate) core and a hard polystyrene shell. The hard plastic shell could prevent the elastomer core from deformation and fusion at room temperature. It was found that the latex particles with the nBA content ⩽60 wt % could be easily coagulated by HCl and redispersed by NaOH with some ultrasound treatment. The coagulation and redispersion processes were repeatable. When the nBA content reached 70 wt %, the plastic shell became too thin, resulting in collapsed sticky particles. The critical shell thickness for redispersible latexes was about 8 nm.