Photochemical Polymerization in Aqueous Solution

Abstract

A NEW series of polymerization photo-sensitizers in aqueous solution, which is based on electron transfer excitation, is described for the first time. E. Rabinowitch¹ has interpreted the absorption spectra of some ion pairs such as Fe³⁺OH^-, Fe³⁺Cl^-, etc., as electron transfer spectra. The light absorption would, according to his hypothesis, cause the reduction of the metal ion and the oxidation of the anion to an atom or free radical ; thus, for example, Fe³⁺OH^-→ Fe²⁺OH. No experimental evidence has been forthcoming which would demonstrate the presence of the latter in the irradiated solution. In this note we present such evidence, and this is based on the ability of these photochemically produced radicals or atoms to initiate the polymerization of vinyl compounds under conditions (hν>300mμ) in which no direct photopolymerization of the corresponding monomers would occur.