Abstract
Films made from blends of poly(styrene) (PS) and poly(vinylacetophenone) (PVAP) (up to 12% mol PVAP) were exposed under high vacuum to long wave u.v. radiation ( λ > 300nm). Spectral changes (phosphorescence, NMR and i.r. indicated that PVAP was photolysed: the nature of gaseous products (in order of abundance, methane, carbon monoxide, ethane and acetaldehyde) confirmed that PVAP was undergoing a Norrish Type I decomposition. There was also evidence of photoreduction, OH absorptions appearing in the i.r. The blended films undergo cross-linking but the insoluble material formed after about 10hr contains little carbonyl. The effects of PVPA concentration and molecular weight on the rate of product formation were also investigated. Experiments with poly(α-D-styrene) confirmed that methyl radicals were abstracting H atoms at the α-position in PS. The implications of such reactions in the initiation of photo-oxidation by polymeric ketonic species are discussed.
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