Thermal cis‐trans isomerization and photofading of some azo dyes in poly(ethylene terephthalate) matrices: A kinetic study

Abstract

Abstract The thermal cis‐trans isomerization of azo dyes X C 6 H 4 N=NC 6 H 4 N(C 2 H 5 ) 2 (where X is H, OCH 3 , CN, and NO 2 ) in poly(ethylene terephthalate) matrices, below the glass transition temperature, and in dibutylphthalate solutions has been studied kinetically in the temperature range 20–60°C. Kinetic behavior in the polymer is characterized by two or three simultaneous first‐order processes with similar activation enthalpies. These processes reflect an unequal distribution of “tie‐molecules,” “folds,” and “cilia” in the amorphous region of the polymer. Lightfastness of the dyes in poly(ethylene terephthalate) films has been investigated. Polymer morphology strongly affected the photofading, but no significant influence was observed in the kinetic experiments.