Photoluminescent enhancement of polyesters via photocrosslinking

ABSTRACT A homologous series of soluble photoluminescent polyesters, namely poly{bis(4‐hydroxybenzylidene)acetone‐5‐(m‐alkyloxyisophthalate)}, PAI1‐PAI5 were designed and synthesized via polycondensation reaction. The branches of these polyesters consisted of flexible alkyloxy chains with different chain lengths in order to investigate their influence toward thermal stability as well as the photocrosslinking property. It was found that increasing length of the flexible chain would reduce the thermal stability of the polyesters. Irradiation of these polyesters under UV light induced photocrosslinking and showed fascinate enhancement in their photoluminescence property with greater emission intensity. This was evidenced visually from the transformation of a weak greenish blue emission to highly intense cloudy blue emission. The photocrosslinking system was further confirmed using spectroscopic methods. Morphology analysis using SEM showed that the photocrosslinked polyesters have a fiber‐like or thread‐like texture with more voids as compared to the virgin polyesters. This was because of the formation of cyclobutanes through photodimerization involving 2π + 2π cycloaddition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41504.