Investigations into the mass spectrometric method for the determination of the mode of termination in radical polymerization

Abstract

The fraction of termination by disproportionation, λ, in radical polymerization may be determined by a mass spectrometric (MS) analysis of the resulting polymer. It is subjected to an array of stringent consistency checks, working with polymerizations of methyl methacrylate at 85 °C in three different solvents and with four different initiators. λ is shown to be unaffected by the choice of initiator, initiator concentration, or isoviscous solvent. These findings serve to allay any fears about the method being undermined by effects such as primary radical termination or chain transfer to solvent, thereby establishing its robustness. At the same time, direct evidence for the occurrence of chain transfer to the solvent methyl isobutyrate is uncovered, and the importance of knowing other rate-parameter values accurately, if λ is to be determined accurately, is illustrated. By carrying out MS analyses, it is concluded that electrospray ionization with time-of-flight detection gives the best results for the present purpose. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.