Structural Difference in Macro-RAFT Agents Redirects Polymerization-Induced Self-Assembly.

Polymerization-induced self-assembly (PISA) has served as a versatile platform for the large-scale preparation of well-defined block copolymer nano-objects. It appears to be "common sense" that block copolymers with narrow molecular weight distributions are inevitable. In this study, we have conducted the direct comparison of reversible addition-fragmentation transfer (RAFT)-mediated PISA of 2-hydroxypropyl methacrylate (HPMA) using polymethacrylate- and polyacrylate-based macro-RAFT agents. Taking advantage of the poor RAFT controllability of polyacrylate-based macro-RAFT agents with respect to HPMA, uniform submicron-sized polymeric microspheres were prepared by photoinitiated RAFT-mediated PISA of HPMA. The diameter of polymeric microspheres can be precisely controlled by further chain-extension of PHPMA. Finally, uniform epoxy-functionalized multicompartment block copolymer particles (MBCPs) were prepared by a two-step photoinitiated RAFT-mediated PISA with poly(glycidyl methacrylate) (PGlyMA) as the third block. The performance of MBCPs as Pickering emulsifiers was evaluated in detail. This study not only expands the scope of RAFT-mediated PISA for preparing well-defined polymer particles but also provides important insights into the mechanism of RAFT-mediated PISA.