Synthesis of azobenzene-containing polymers and investigation of their substituent-dependent isomerisation behaviour

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• 作者：Ulrike Georgi^a ; ^c ; Philipp Reichenbach^b ; Ulrich Oertel^a ; Lukas M. Eng^b ; Brigitte Voit^a ; ^c ; ^{voit@ipfdd.de}
• 关键词：Azobenzene ; Isomerisation kinetics ; Thermal cis&ndash ; trans-relaxation ; UV&ndash ; Vis spectroscopy ; Polymer-analogous reaction
• 刊名：Reactive and Functional Polymers
• 出版年：2012
• 期刊代码：92_13815148
• 类别：ch
• 出版时间：April, 2012
• 卷：72
• 期：4
• 页码：242-251
• 文件大小：629 K

摘要

A variety of 4,4鈥?substituted azobenzenes has been synthesised and the kinetics of the thermal cis-trans-relaxation of the substances was studied in detail in solution and embedded in a poly(methyl methacrylate) (PMMA) matrix by UV-Vis spectroscopy. Considerable differences in relaxation times were found for the various azobenzenes which interestingly could not be fully explained by simply comparing the substituents with regard to their electron-donating or -withdrawing nature. Any substituents, especially very polar ones, increase the thermal cis-trans-reaction rate. Some of the chromophores were covalently attached to a PMMA-copolymer and we found that this significantly slowed down the isomerisation kinetics compared to the embedding of low molar mass azobenzenes in a polymer matrix. But our study showed also that, even at room temperature, the thermal cis-trans-relaxation of 4,4鈥?substituted azobenzene chromophores can never be fully suppressed, but only slowed down.