Photolysis of poly(benzyl methacrylate)s and poly(benzyl acrylate)s in solution and films

Methacrylate and acrylate copolymers containing benzyl or I-phenylethyl gro ups and their monomeric model compounds were irradiated with a 254-nm light in CH2Cl2 and solid films. Low molecular weight and polymeric products wer e analyzed by gas chromatography (GC) and NMR spectroscopy, respectively, a nd main-chain scission efficiencies were determined by gel permeation chrom atography (GPC). The results indicate that the ester bond cleavage in the s ide chain produces alkyl radicals in the main chain, leading to main-chain scission and crosslinking. The higher stability of tertiary alkyl radicals formed in methacrylate polymers lead to the predominant main-chain scission in solution. On the other hand, acrylate polymers were less susceptible to photodegradation. The degradabilities of the polymer films reflected those of the polymer solutions, although crosslinking preferentially occurred. T he distinct effect of oxygen on the degradation was also observed in soluti on and films. (C) 2001 John Wiley & Sons, Inc.