Thermo- and Solvent-Responsive Polymer Complex Created from Supramolecular Complexation between a Helix-Forming Polysaccharide and a Cationic Polythiophene
Thermo- and Solvent-Responsive Polymer Complex Created from Supramolecular Complexation between a Helix-Forming Polysaccharide and a Cationic Polythiophene
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DOI：
10.1021/ja1067349
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发表时间：
2010-10-06
影响因子：
15
通讯作者：
Shinkai, Seiji
中科院分区：
文献类型：
--
作者：
Shiraki, Tomohiro;Dawn, Arnab;Shinkai, Seiji
螺旋结构是生物体系和人工手性体系的关键结构组分之一。到目前为止，我们已经成功地制造了“紧”绝缘分子线组成的三股共螺旋结构，通过超分子包装的合成聚合物的螺旋形成多糖（speakophyllan）。在此，我们设计了一种新的改性多糖（Curoeg）与共轭聚合物（CP）形成一种“松散”的大分子复合物，允许响应外部刺激的结构变化。Cur-oeg与非手性阳离子聚噻吩（PT 1）形成螺旋复合物，有效共轭长度随温度变化，在85 ℃至5 ℃之间显示出从403 nm至482 nm的大吸收峰位移。根据共轭体系的变化，荧光和诱导圆二色性在温度控制下显示连续的光谱位移。在吸收和荧光中的颜色变化可以用肉眼观察到，并且在热循环下可逆地控制，这表明该系统具有“分子温度计”的功能。结果表明，诱导的热响应性与复合物中PT 1的螺旋构象的结构重排有关。此外，还发现了膜状态的另一种独特的响应性：即，当暴露于水或甲醇的蒸气时，膜颜色发生变化（汽色性），这是由于即使在膜状态下也会发生PT 1的结构变化。这些分子在溶液态和膜态的柔性运动可以应用于CP基智能传感器、极化材料、开关器件等的设计。
The helical structure is one of key structural components for both biological systems and artificial chiral systems. So far, we have succeeded in fabricating "tight" insulated molecular wires consisting of a triple-stranded cohelical structure formed through supramolecular wrapping of synthetic polymers by a helix-forming polysaccharide (schizophyllan). Herein, we have designed a new modified polysaccharide (Curoeg) to form a "loose" macromolecular complex with a conjugated polymer (CP) that allows structural changes in response to external stimuli. Cur-oeg forms a helical complex with an achiral cationic polythiophene (PT1), and the effective conjugation length is changed by temperature, showing a large absorption peak shift from 403 to 482 nm between 85 and 5 degrees C. According to the change in the conjugation system, the fluorescence and the induced circular dichroism show the continuous spectral shifts under temperature control. The color changes in the absorption and the fluorescence are detectable with observation by the naked eye and are reversibly controlled under thermal cycles, indicating that this system has the function of a "molecular thermometer". It is shown that the induced thermoresponsiveness is associated with structural rearrangement of the helical conformation of PT1 in the complex. Moreover, another unique responsiveness is discovered for the film state: that is, the film color is varied when it is exposed to the vapor of water or methanol (vaporchromism), resulting from the structural change of PT1 occurring even in the film state. These flexible molecular motions in both the solution state and the film state can be applicable to the design of CP-based smart sensors, polarized materials, switching devices, etc.