| Autor: |
Chesnokov, S., Cherkasov, V., Abakumov, G., Mamysheva, O., Chechet, Yu., Nevodchikov, V. |
| Zdroj: |
Russian Chemical Bulletin; Dec2001, Vol. 50 Issue 12, p2366-2371, 6p |
| Abstrakt: |
o-Benzoquinones initiate radical polymerization of methacrylates under visible light irradiation in the presence of tertiary amines. Spectral sensitivity of the initiating system coincides with absorption bands of o-benzoquinone attributed to the S(π→π*) (λmax ≈ 400 nm) and S( n→π*) (λmax ≈ 600 nm) transitions. The amine radicals (Am·) initiating polymerization are generated by the photoreduction of Q in the presence of AmH from the triplet radical pair 3(QH·, Am·). The yield of Am· depends on the difference between the volumes of substituents in the 3 and 6 positions of the quinoid ring and is maximal for symmetrically substituted o-benzoquinones. For a series of derivatives of symmetrical 3,6-di- tert-butyl- o-benzoquinone, the rate of photopolymerization of α,ω-bis(methacryloyloxyethyleneoxycarbonyloxy)ethyleneoxyethylene (OCM-2) in the presence of N, N-dimethylaniline is determined by the free energy (Δ Ge) of electron transfer from the amine to photoexcited o-benzoquinone. The Δ Ge value includes the energies of oxidation of the amines and reduction of the o-quinones and the energy of the 0→0 transition of the triplet excited state of o-benzoquinones, which are equal to their redox potentials. The photopolymerization rate is maximal for Δ Ge ≈ 0. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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