Triplet-Sensitized Reactions of Some Main Chain Liquid-Crystalline Polyaryl Cinnamates

Document Type

Conference Proceeding

Publication Date



Chemistry and Biochemistry


Mathematics and Natural Sciences


Thin films of a liquid crystalline polyaryl cinnamate have been irradiated at (lambda) > 400 nm in the presence of ketocoumarin triplet sensitizers. The aryl cinnamate chromophore disappears upon irradiation with concomitant loss of solubility attributed to cross-linking by interchain cyclobutane photoproduct formation. Competing loss of sensitizer absorption also occurs during irradiation. Up to ca. 80% of the aryl cinnamate chromophores in amorphous films can be destroyed using high weight percentages (>= 5%) of sensitizer. At low concentrations of sensitizer (0.5 wt.%), approximately 80 cinnamate chromophores are photolyzed for each sensitizer molecule initially present, despite the competing photolysis of sensitizer during the course of irradiation. The ketocoumarins are insoluble in the glassy (frozen) nematic films of the polymer and thus are ineffective in sensitizing photolysis in this more organized phase.

Publication Title

Proceedings Volume 1774, Nonconducting Photopolymers and Applications