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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Phototriggered Fluorescence Color Changes in Azobenzene-Functionalized Conjugated Polymers
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Phototriggered Fluorescence Color Changes in Azobenzene-Functionalized Conjugated Polymers

机译：偶氮苯官能化共轭聚合物的光触发荧光颜色变化

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摘要

We report fluorescence studies of phototriggered changes in spectral position and shape for two azobenzene-functionalized poly(p-phenylenevinylene) derivatives,poly(2-methoxy-5-(4-phenylazophenyl-4'-( 1,10-dioxy-decyl))-1,4-phenylenevinylene) (MPA- 10-PPV) and poly(2-hexyloxy-5-(4-phenylazophenyl-4'-( 1,10-dioxydecyl))-1,4-phenylenevinylene) (HPA-10-PPV).Upon trans -> cis azobenzene photoisomerization,small (ca.1 nm) blue shifts in spectral position are observed for MPA-10-PPV in 100% toluene,a good solvent for this polymer.These shifts are reversed upon visible irradiation and can be cycled many times.To probe the dependence of these shifts on initial polymer conformation,a dichloromethane-methanol cosolvent study was performed in which the solvent quality was decreased incrementally to induce a reduction in polymer coil dimensions.Unirradiated dichloromethane solutions of both MPA-10-PPV and HP A-10-PPV showed a red shift and reduction in quantum yield with increasing methanol concentration as expected based on literature results for other poly(p-phenylenevinylene) derivatives.These changes have been attributed to a dramatic conformational collapse by others and occur for these azo polymers over the 30-60% (v/v) methanol range.While little or no light-induced spectral shifting was observed at low (<=20%) and high (>=70%) methanol concentrations,significant spectral shifts were observed for both polymers upon azobenzene photoisomerization in solutions with 30-60% methanol,the same range over which the polymer undergoes collapse to a highly coiled state.The largest shifts are visible to the eye,with a 65:35 (v/v) dichloromethane-methanol solution of HPA-10-PPV showing yellow-orange fluorescence when the azobenzenes are trans,green fluorescence when they are cis,and yellow-orange again after the azobenzenes are returned to the trans state.We attribute these color changes to a reversible UV-phototriggered expansion of polymer coil dimensions that occurs as a result of trans -> cis azobenzene side chain isomerization and provide temperature data to support this conclusion.
机译：我们报道了两个偶氮苯官能化的聚对苯撑亚乙烯基衍生物，聚（2-甲氧基-5-（4-苯基偶氮苯基-4'-（1,10-二氧-癸基） ）-1,4-亚苯基亚乙烯基）（MPA-10-PPV）和聚（2-己氧基-5-（4-苯基偶氮苯基-4'-（1,10-二氧癸基））-1,4-亚苯基亚乙烯基）（HPA- 10-PPV）。在反式->顺式偶氮苯光异构化后，在100％甲苯（该聚合物的良好溶剂）中观察到MPA-10-PPV的光谱位置出现小幅度（约1 nm）蓝移。为了探测这些变化对初始聚合物构象的依赖性，进行了二氯甲烷-甲醇助溶剂的研究，在该研究中，溶剂质量逐渐降低，从而导致聚合物卷材尺寸减小。随着甲醇浓度的增加，MPA-10-PPV和HP A-10-PPV均显示出红移并降低了量子产率根据其他聚对苯撑亚乙烯基衍生物的文献结果，预期得到这种处理，这些变化归因于其他化合物的显着构象崩溃，并且这些偶氮聚合物在30-60％（v / v）的甲醇范围内发生。在低浓度（<= 20％）和高浓度（> = 70％）的甲醇中几乎观察不到或没有光诱导的光谱偏移，在30-60％的甲醇溶液中偶氮苯光异构化后，两种聚合物均观察到显着的光谱偏移。肉眼可以看到最大的位移，当HPA-10-PPV的65:35（v / v）二氯甲烷-甲醇溶液显示黄色橙色荧光时，则可看到该位移。偶氮苯是反式的，当它们是顺式时是绿色的荧光，在偶氮苯返回到反式状态后又是黄橙色的。我们将这些颜色变化归因于可逆紫外线引发的聚合物线圈尺寸的膨胀，这是由于反式->顺式偶氮苯侧链异构化并提供温度数据来支持这一结论。

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