Photochemical behaviour of poly(ethylene oxide) (PEO) in aqueous solution: Influence of iron salts

The degradation of poly(ethylene oxide) (PEO) photoinduced (λ ≥ 300 nm) by Fe(III) (6.0 × 10−4 mol L−1) in aqueous solution in the presence of oxygen at 15 °C has been investigated in various experimental conditions of pH and concentrations: pH 3.1 and 7.8 and at three different concentrations of PEO: 0.1, 5.0 and 50.0 g L−1. The formation of oxidation products was followed by infrared analysis of deposit obtained by evaporation of aliquots of irradiated polymer solutions. The photooxidation of PEO aqueous solutions both in the presence and in the absence of Fe(III) leads to the formation of macromolecular formates and esters. Formate ions are formed by the hydrolysis of macromolecular formates leading to the acidification of the medium. The presence of Fe(III) modifies the rate of oxidation especially in weakly acidic medium. The photogenerated OH radicals from iron species accelerate the oxidation of PEO. Thermooxidation experiments of PEO in aqueous solution in the presence of Fe(III) at 50 °C are also reported and compared with photooxidation results.