All eight 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylates (3, 4) containing terminal photoreactive coumarin chromophores show strong fluorescence intensities at room temperature in dimethyl sulfoxide (DMSO) and CH2C12. After irradiation with 350 nm light for 2 h, the fluorescence characteristics of the dicarboxylates reveal their photopolymerization paths. On irradiation of the unsubstituted dicarboxylates (3) in DMSO, singlet excited state excimers are formed, leading to syn head-to-head coumarin dimer configuration. However, for all dicarboxylates in CH2Cl2, the dimerization of the coumarin chromophore proceeds via a triplet excited state in the presence of benzophenone to form the anti-configuration photoproducts. Further confirmations of the reaction mechanism are made by kinetic studies. At high concentration, photopolymerization of 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylate (4c) obeys zero-order and first-order kinetics for coumarin chromophore and benzophenone, respectively. This is a powerful proof of the proposed mechanism of a triplet excited state reaction.
|Number of pages||10|
|Journal||Journal of Polymer Science, Part A: Polymer Chemistry|
|Publication status||Published - 1997 Jan 1|
All Science Journal Classification (ASJC) codes
- Polymers and Plastics
- Organic Chemistry
- Materials Chemistry