Photodecomposition of poly(styrene peroxide) in vinyl monomers and structural features of the formed polymers

Poly(styrene peroxide) (PSP) initiated photopolymerization of vinyl monomers has been carried out using benzoyl peroxide or di-tert-butyl peroxide as a reference photoinitiator with radiations of wavelength ⩾300 nm. Comparative rates of PSP degradation in the vinyl monomers are examined to assess its efficiency of radical generation. The faster rate of PSP decomposition in acrylamide and acrylonitrile has been attributed to their catalytic effects on PSP decomposition. The obtained polymers were characterized by molecular weight, 1H-NMR and thermal studies. Interestingly, it revealed the absence of attached PSP segments in poly(acrylamide) and poly(acrylonitrile) unlike in poly(methyl methacrylate) (PMMA) and polystyrene (PS) where PSP blocks were reported to be present near their chain ends. Presence of PSP block does not drastically affect their thermal stabilities. The average concentrations of PSP blocks in PMMA–b-PSP and PSP–PS–PSP, determined by 1H-NMR, DSC, TG and GPC were in reasonably good agreement, and it is related to the extent of PSP decomposition in methyl methacrylate and styrene. The molecular weight and yield of the polymers, obtained with PSP, were always higher and lower, respectively, compared to simple peroxides in all the monomers except in AA where they are roughly comparable, and this was attributed to the differences in the concentration of the primary radicals formed during irradiation.