Chloroprene (CP)-based block copolymers were synthesized via the RAFT-mediated emulsion polymerization of CP using polyacrylate macro-chain transfer agents (CTAs) via a one-pot (in-situ), two-step process. The quantitative formation of hydrophobic macro-CTA in the latex in the first step and subsequent incorporation of CP monomer into the latex using a high internal phase emulsion (HIPE) in the second step were observed to be crucial for producing poly(CP)-based block copolymers. The formation of poly(CP)-b-poly(n-butyl acrylate) s were confirmed by an evident shift in the SEC traces and the H-1 and DOSY NMR measurements. The block copolymers exhibited microphased structures composed of the poly(CP) matrix with low Tg (-30 degrees C) and the poly(nBA) spherical phase with lower Tg (-50 to -60 degrees C), as revealed by dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM). This study represents the first report of the controlled synthesis of poly(CP)-based block copolymers by RAFT-mediated emulsion polymerization using HIPE. (C) 2018 Elsevier Ltd. All rights reserved.