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Kinetics of a photochromic reaction in a dibenzoazo crown ether in solution and in polymer matrices

✍ Scribed by Krzysztof Janus; Juliusz Sworakowski; Andrzej Olszowski; Aleksandra Lewanowicz; Józef Lipiński; Elżbieta Luboch; Jan Biernat

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
198 KB
Volume
9
Category
Article
ISSN
1616-301X

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✦ Synopsis

The kinetics of thermal cis-trans isomerisation of photochromic dibenzoazo 16-crown-4 ether was studied in several matrices (isooctane, polystyrene and pMMA samples fabricated in various ways) using UV-vis spectroscopy. The rate constants were found to be almost independent of the nature of the matrix and the method of its fabrication. The average activation energy of the isomerisation amounts to 9365 kJ mol À1 , the pre-exponential factor being of the order of 10 10 s À1 . The independence of activation energy on the matrix can be explained by taking into account the relatively small difference in the molecular volumes of the two isomers. In polymerised pMMA samples the decays were non-exponential, probably owing to a distribution of rate constants associated with a distribution of microenvironments of photoactive molecules.

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