Chain transfer to solvent in the radical polymerization of N-isopropylacrylamide

Abstract

Chain transfer to solvent has been investigated in the conventional radical polymerization and nitroxide-mediated radical polymerization (NMP) of N-isopropylacrylamide (NIPAM) in N,N-dimethylformamide (DMF) at 120 °C. The extent of chain transfer to DMF can significantly impact the maximum attainable molecular weight in both systems. Based on a theoretical treatment, it has been shown that the same value of chain transfer to solvent constant, C tr,S, in DMF at 120 °C (within experimental error) can account for experimental molecular weight data for both conventional radical polymerization and NMP under conditions where chain transfer to solvent is a significant end-forming event. In NMP (and other controlled/living radical polymerization systems), chain transfer to solvent is manifested as the number-average molecular weight (Mn) going through a maximum value with increasing monomer conversion. © 2011 Wiley Periodicals, Inc.