High chain-end fidelity in sono-RAFT polymerization

Abstract

The chain-end fidelity of polymers synthesized via the sono-RAFT technique in an aqueous medium was investigated by performing chain extension studies and preparation of multi-block copolymers. Sono-RAFT polymerization of N,N-dimethylacrylamide (DMA), 2-hydroxyethyl acrylate (HEA) and N-acryloyl morpholine (NAM) exhibited higher conversion values, low dispersity and excellent chain-end fidelity. MALDI-TOF analysis indicated that the fraction of dead chains observed was almost negligible indicating high livingness of the polymer end groups. The sono-RAFT technique was compared to the photo-iniferter method by performing chain extension experiments. Polymers prepared via sono-RAFT were identical to those prepared via the photo-iniferter RAFT method in terms of livingness, and the polymer reached very high conversion within a fraction of the time compared to the latter method. An icosapenta block copolymer (25 blocks) was synthesized at room temperature within 46 h. The resulting block copolymer displayed a controlled molecular weight and a final dispersity of 1.39.