FRACTIONAL HEATING DIFFERENTIAL SCANNING CALORIMETRY - A TOOL TO STUDY ENERGETICS AND KINETICS OF SOLID-STATE REACTIONS IN PHOTOACTIVE SYSTEMS WITH DISTRIBUTED PARAMETERS

The technique of differential scanning calorimetry (DSC), used in meas urements of thermal effects accompanying solid-state chemical reaction s, can be regarded as a thermally stimulated method. Model calculation s demonstrate the applicability of the DSC technique in determining pa rameters controlling the kinetics of solid-state reactions. In particu lar, it has been shown that the fractional heating technique can be su ccessfully used to analyse DSC curves in case of distributions of kine tic parameters. The method was employed to obtain information about th e parameters controlling a thermally driven reaction following UV illu mination of photoactive 1-methyl-2,4,4,6-tetraphenyl-1,4-dihydropyridi ne. Two peaks on DSC curves were distinguished, probably corresponding to different processes associated with reactions responsible for the bleaching of the coloured material. The activation energy and the pre- exponential factor of at least one of them were determined. (C) 1998 E lsevier Science B.V. All rights reserved.