The kinetics of the photo-rearrangement of pendant α-phenyl-o-nitrobenzyl ester groups in copolymers. polymer and solvent effects
✍ Scribed by Qin Qin Zhu; Hans Schupp; Wolfram Schnabel
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 237 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0014-3057
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✦ Synopsis
Copolymers of ~t -phenyl-o -nitrobenzylacrylate or a -methyl-o-nitrobenzyl acrylate with methyl methacrylate (denoted as CP--~tPoNBA-MMA and CP--~tMoNBA-MMA) and corresponding model compounds [a-phenyl-o-nitrobenzyl isobutyrate (ctPoNBI) and benzoate (ctPoNBB), and ~-methyl-o-nitrobcnzyl isobutyrate (~tMoNBI) and benzoate (~tMoNBB)] were irradiated in dilute solutions in various solvents with 20 nsec flashes of 347 nm light. The kinetics of the decay of nitronic acid formed during the flash were studied. Nitronic acid of compounds possessing phenyl in the ~t-position underwent the rearrangement more rapidly than that from compounds having methyl in the ~t-position. The extent of acceleration depended on the solvent in the order CH2C12 > benzene > CH3CN. In acetonitrile solution a kinetic polymer effect was found with CP--~tPoNBA-MMA: non-exponential decay of nitronic acid in the case of the copolymer and exponential decay in the case of the model compounds. This polymer effect is explained in terms of rather strong intramolecular interactions between phenyl groups of different repeating units leading to an augmentation of the accelerating action. In benzene and dichloromethane solution, the decay was exponential indicating the predominance of the interaction between solvent and phenyl over that between phenyl groups.