Polymerization-induced self-assembly via RAFT in emulsion: effect of Z-group on the nucleation step

Polymerization-induced self-assembly (PISA) has emerged as one of the most powerful and widely employed techniques for preparation of block copolymer and polymeric nanoparticles in dispersed systems. Its success relies on a rapid, easily scalable and straightforward process, associated with the ability to readily control nanoparticle morphology. In the present work, we have investigated the effect of the Z-group of RAFT agents ZC(S)–SR on the nucleation step of aqueous RAFT PISA performed in environmentally friendly emulsion polymerization. Seven different poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) macroRAFTs were synthesized using RAFT agents containing Z-groups of different hydrophilicity. Slow polymerizations and incomplete chain extension reactions were observed for systems with the most hydrophilic Z-group, while the more hydrophobic Z groups led to higher polymerization rates and very successful chain extensions. A mechanism based on Z-group induced RAFT exit is proposed to rationalize this surprising behaviour, providing important information on the mechanistic understanding and optimization of PISA in emulsion.