US EPA

6155634 

Journal Article 

Photoreactions of poly(p-propionylstyrene) in solution 

Arct, J; Weir, NA; Whiting, K 

1991 

Yes 

European Polymer Journal
ISSN: 0014-3057 

27 

4 

423-428 

10.1016/0014-3057(91)90199-X 

http://www.sciencedirect.com/science/article/pii/001430579190199X
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Dilute solutions (2 × 10−3 M) of poly(para-propionylstyrene) were exposed to long-wave u.v. radiation (λ ⩾ 300 nm) under high vacuum at 25°C. Methane and ethane were formed, their quantum yields [< 10−4 mol(einstein)−1] being lower than those observed for the solid state photolysis. Both α-cleavage (Norrish Type I) and β-fission of the ethyl group are involved. Chain scission occurs more readily in solution; this effect was attributed to the decomposition (β-scission) of the tertiary radicals formed during photoreduction. Cyclization involving non-neighbouring tertiary radicals and cross-linking also occur. The presence of H-donors (isopropanol) reduces the extent of chain scission, and molecular weight increases due to cross-linking are then observed. Solvent quality plays an important role, the poorer solvent leading to a more tightly coiled polymer, in which intra-coil photoreduction is facilitated, and the rate of chain scission is increased.