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 2p 1 2p cycloaddition.

Formation of supramolecular channels by reversible unwinding-rewinding of bis(indole) double helix via ion coordination

“…Subsequent hydrogenation reaction of indole-amides 9a − 9b gave the reduced products 10a − 10b in quantitative yield. The amine derivatives 10a − 10b were eventually coupled with freshly prepared isophthaloyl dichlorides 55 , 56 12a − 12b to furnish the desired compounds 1a − 1d in 82−86% yield. In order to synthesize the 1e derivative, the indole ester compound 6 was first converted into the iodo-indole ester derivative 13 through an iodination reaction, and subsequently coupled with 4- tert -butylphenyl boronic acid through the Suzuki coupling to furnish 4-tert-butylphenyl substituted indole ester 14 .…”