Radiation induced crosslinking of poly(vinyl methylether) in aqueous solutions

Radiation induced crosslinking of poly(vinyl methylether) (PVME) has been i nvestigated in aqueous solutions. The spectral and kinetic features of the transients involved in the crosslinking reaction have been studied by pulse radiolysis of dilute PVME solutions. H atoms reacts with PVME, like OH rad icals, by abstracting an H atom predominantly from beta-position with respe ct to -OCH3 group, but the rate of reaction of H atom is an order of magnit ude slower than that of OH reaction. The PVME radicals formed by H attack h ave been found to decay by usual 2nd-order kinetics unlike PVME radicals pr oduced by OH attack that are reported to decay by a complex time-dependent kinetics that deviates strongly from 2nd-order kinetics. The rate constant of e(aq)(-) with PVME at pH 5.5 has been found to be 1.2 x 10(8) dm(3) mol( -1) s(-1). From the decay behaviour of the transient species formed by reac tion of e(aq)(-) with PVME, it has been shown that the transient initially reacts with solvent protons by a fast reaction to yield radical species whi ch subsequently recombine by a slow mode. The dependence of gelation dose a nd radiation yields of crosslinking (Gx) of PVME on various factors such as polymer concentration, dose rate, pH, presence of oxygen and crosslinking agent has also been studied by steady-state radiolysis using an electron-be am accelerator. (C) 1999 Elsevier Science Ltd. All rights reserved.