(Photosensitive Polymers VII) Mechanism of Photosensitized Curing Reaction of Cinnamoylated Polymers

(感光性 高分子에 關한 硏究 VII) Cinnamoylated Polymers의 光增感 硬化反應機構

  • Kim, Kwang-Sup (Dept. of Chemical Engineering, College of Engineering, Seoul National University) ;
  • Shim, Jyong-Sup (Dept. of Chemical Engineering, College of Engineering, Seoul National University)
  • 김광섭 (서울大學校 工科大學 化學工學科) ;
  • 심정섭 (서울大學校 工科大學 化學工學科)
  • Published : 19661200

Abstract

The multistep mechanism of photosensitized curing reaction cinnamoylated photosensitive polymer is proposed from the energy level diagram of cinnamic acid and sensitizer, and from the fact that excess of sensitizer brings the sensitivity to a limiting value etc. Various factors which have effects on the ability of sensitizer are also discussed. The mechanism involves following steps: activation to the first excited singlet states of cinnamoyl group(C) and sensitizer(S) by their absorption of photon, their intersystem crossing to the lowest triplet state, bimolecular internal quenching by formation of excimer of sensitizer, triplet excitation energy transfer and intermolecular addition between cinnamoyl group in ground state and that in triplet state. The rate equation derived from this mechanism is $-\frac{d[C]}{dt} = \frac{K_1[C]}{K_2 + [C]}[\frac{I^c_{abs}}{K_3 + [S]} + \frac{K_4[C]}{(K_5 + [C])(K_6 + [S])}(I^s_{abs} + \frac{K_7I^c_{abs}[S]}{K_8 + [S]})]$ where $I^c_{abs}\;and\;I^s_{abs}$: the rates of absorption of photon by cinnamoyl group and sensitizer $K_n$: Constants. It is proved with the cinnamate of poly(glyceryl phthalate)(PGC) in the absence of sensitizer using the infrared analytical method and successfully applied for the experimental data reported on the effects of the degree of cinnamoyl esterification and the concentration of sensitizer upon the sensitivity.

Keywords

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