Kinetics of processes accompanying photoreduction of chloride complexes of Fe 3+ in solid polymers

Abstract

Additives of FeCl 3 and tetrachloroferriate tetraethylammonium FeCl 4N(C 2H 5) 4 (Y) in polymethylmethacrylate (PMMA) and FeCl 3 in polypropylene (PP) have been used as test materials for investigating the kinetic peculiarities of the photoreduction of transition metal coordination compounds in the solid-phase in an inert atmosphere under the effect of light of different spectral compositions ( λ = 313, 365, 405 nm) at 77 and 293 K. Accumulation of macroradicals generated in chlorine atom reactions with the polymer matrix at 77 K has also been studied. It has been shown that, in contrast to liquid-phase reactions and reactions in PP above the glass transition temperature, T g , these processes are characterised by a certain distribution of a number of the reacting particles according to their photoreduction quantum yields (ϕ) at temperatures below T g , whatever the addition (FeCl 3 or Y). The results are processed to obtain quantitative data. The kinetic non-equivalence of the reaction centres in the polymer matrix which, due to its structural inhomogeneity, apparently manifests itself in the thermal stage of decomposition of an unstable intermediate state resulting in the formation of chlorine atoms. The values of ϕ and kinetics of FeCl 3 consumption are compared in PP and PMMA. It has been found that if matrix mobility is decreased, which may be achieved either by increasing the T g of the polymer or decreasing the experimental temperature, the process kinetics acquire features of solid-phase reactions. At low temperatures, the radicals were observed to react with Fe 2+ ions, regenerating FeCl − 4 ions. Kinetic parameters of this process have been obtained.