Crosslinking of polystyrene film by di(4-dibenzoyl peroxide) ether synthesized or formed in situ using visible light-induced photo-peroxidation of 4,4’-oxydibenzil

Abstract

Upon irradiation (λ > 400 nm) in aerated glassy polystyrene (PS) film, 4,4′-oxydibenzil (BZ-O-BZ), possessing two benzil (BZ) moieties in its structure, undergoes insertion of molecular oxygen between carbonyls of BZ moieties leading to the formation of di(4-benzoyl peroxide)ether (BP-O-BP).In addition, there may be decomposition of the benzoyl peroxide (BP) structures that are photosensitised intramolecularly by BZ structures in BP-O-BZ intermediates. Thermal decomposition of the BP-O-BP yields two acyloxy radicals, which can either be added to the phenyl rings of PS resulting in crosslinking or in a combination of the liberated hydrogen to form an acid. Acyloxy radicals may also react with the chain of PS causing degradation (main chain scission). The thermal decomposition of the synthesised BP-O-BPs and added to high-molecular PS films produces a fully crosslinked material and higher crosslink densities than the peroxides prepared in situ by irradiation of BZ-O-BZ. The mechanism of the PS crosslinking with the BP-O-BP synthetically prepared as well as the BP-O-BP prepared in situ photochemically is elucidated. PS crosslinking with BP-O-BP represents a new and effective method of PS crosslinking.