Reversible Addition Fragmentation Chain Transfer-Mediated Copolymerizations: The Challenge of Random Copolymer Blocks

The synthesis of random copolymer blocks as part of a block copolymer is potentially one of the unique features of living radical polymerization. However, in this contribution it is shown that subtle variations, such as the choice of a different initiating radical are sufficient to induce variations in copolymer composition at the early stages of the chain growth. The very first few monomer additions in a RAFT-mediated styrene — acrylonitrile copolymerization are studied using in situ 1 H NMR spectroscopy. Initialization behavior is observed in a similar fashion as seen in a RAFT-mediated homopolymerization. In a RAFT-mediated alternating styrene — maleic anhydride copolymerization, the effect of the nature of the leaving group of the RAFT-agent is clearly demonstrated by careful analysis of the resulting (low molar mass) copolymers.