Radiation effect on poly(vinylbenzyltrimethylammonium chloride) in aqueous solution: pulse radiolysis and steady-state study.

Abstract

Poly(vinylbenzyltrimethylammonium chloride) (PVBT) has been synthesized by radiation-induced polymerization of Vinylbenzyltrimethylammonium chloride (VBT). The viscosity average molecular weight of synthesized polymer was estimated to be approximately 10(5) by viscosity measurements. The radiation-induced affects on PVBT have been investigated by steady-state and pulse radiolysis (PR) techniques. The reactions of primary radicals (*)OH, e(aq)(-), and H(*) generated by the radiolysis of water with PVBT were studied. The reactions of some other species such as N(3)(*), Cl(2)(*-), Br(2)(*-), SO(4)(*-), and CO(2)(*-) with PVBT were also investigated. The results indicate that the reactivity of these species toward PVBT is lower then that with the monomer VBT. The rate constants for the reactions of OH radical and H atom with PVBT were evaluated both by competition kinetics and by direct observation of the buildup of transient species. The difference in the rate constant values evaluated by the two methods indicated that (*)OH and H(*) react with PVBT to give more than one species. It was observed that the OH radical and H atom react with PVBT in different manners. Near neutral pH, the OH radicals react to form an adduct and to generate a radical by abstracting methylenic H atom. The H atom, however, also abstracts the H atom from the PVBT backbone. The rate constant value for the reaction of hydrated electron with PVBT was found to be 3.1 currency 10(9) dm(3) mol(-1) s(-1). Steady-state irradiation studies of the aqueous PVBT solution indicated that PVBT predominantly undergoes cross-linking on irradiation. Cross-linking is a function of dose rate, concentration, and ambient of irradiation. At concentrations < 2%, only intramolecular cross-linking takes place, whereas beyond this concentration, the intermolecular cross-linking of polymer chains takes place to form a soft gel. The gel dose (D(gel)) is a function of the ambient of irradiation.