Recent Advance in ESR Study on the Radical Polymerization

摘要

Much attention has been paid to electron spin resonance (ESR) studies of the radical polymerization of vinyl or diene compounds, Usually, the concentration of the propagating radicals was too low to be detected in the practical conditions in the radical polymerization by a conventional CW-ESR spectrometoryl. Recently, we have found that the well-resolved ESR spectra assigned to the propagating radicals for several vinyl and diene monomers could be observed in a single scan without the aid of the computer accumulation. Accordingly, direct infonnation on the structure, properties, and concentration of propagating radicals could be obtained. Furthermore, the ESR measurements were found to be possible in the steady state of the concentration of the propagating radicals if the optimum conditions are chosen in the initiator concentration and irradiation light intensity. Accordingly, propagation rate constants for vinyl and diene compounds were determined by this method. In the course of the determination of kp for styrene, we found a difference in kp between photo-and thermal-initiated polymerizations of styrene. Moreover, application of the time-resolved ESR spectrcopy to the elucidation of the mechanism of initiation process in the radical polymerization will be mentioned. In this review, I will mention recent advance in ESR study on radical polymerization.