Photoreactions of poly(p-propionylstyrene) in solution

✍ Scribed by Neil A. Weir; J. Arct; Kenneth Whiting

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 439 KB
• Volume: 27
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(91)90199-x

✦ Synopsis

Dilute solutions (2 x 10 -3 M) of poly(para-propionylstyrene) were exposed to long-wave u.v. radiation (2 ~> 300 rim) under high vacuum at 25°C. Methane and ethane were formed, their quantum yields [<10-4mol(einstein) -I] being lower than those observed for the solid state photolysis. Both s-cleavage (Norrish Type I) and fl-fission of the ethyl group are involved. Chain scission occurs more readily in solution; this effect was attributed to the decomposition (~-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.