Polystyrene in chlorinated solvents

Polystyrene [211, 279, 615, 1244, 1358, 1739, 2163, 2285-2290] and poly(a-methylstyrene) [211] dissolved in chlorinated solvents such as CHCI3, CHjCl, or CCI4 or doped as a film in CCI4 [2120] undergo rapid chain scission under UV irradiation. 

The main chain scission degradation of polystyrene in CHCI3 is caused by solvent radicals, which abstract hydrogen from polymer molecules. Solvent radicals may be formed by an energy transfer from the excited phenyl groups in polystyrene  

An alternative mechanism may involve the formation of a charge-transfer (CT) complex [279], which absorbs radiation and forms an exciplex between the excited phenyl group and a solvent molecule, which further dissociates into radicals or ions [279, 2083, 2084]  

It has been shown that chlorine radicals (Cl ) can abstract hydrogen from polystyrene in degassed chlorine-containing solutions. As result of these reactions conjugated double bonds (—C=C—) with n = 2-5 form [2163, 2285, 2290]  

The rate of the photo-oxidative degradation of polystyrene in halomethanes increases in the order methylene chloride chloroform carbon tetrachloride, i.e. it increases with increasing electron affinity of the solvent [279]. Photodegradation of poly(a-methylstyrene) in carbon tetrachloride by 

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