Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan.
J Phys Chem B. 2012 Feb 16;116(6):1758-64. doi: 10.1021/jp207443s. Epub 2012 Feb 6.
The molecular dynamics of a polyaniline/β-cyclodextrin inclusion complex (PANI/β-CD IC) and its relation with optical properties were investigated using high-resolution solid-state (13)C nuclear magnetic resonance (NMR) and optical absorption spectroscopies. UV-vis measurements revealed a π-π* absorption peak of a PANI film that had a 10 nm blue-shift by inclusion of β-CD, indicating that π-conjugation of PANI was shortened in the IC. Temperature dependent analysis of (13)C NMR spectra and spin-lattice relaxation times (T(1C)) revealed that the inclusion induced acceleration of the twisting motion of the PANI chain. Moreover, two twisting motions attributed to different torsional angle modes were observed following Arrhenius plots of T(1C) measurements, and the twisting frequency and angle increased above -25 °C. These results suggest that the β-CD inclusion weakens the intermolecular π-π interaction and enhances the accompanying twisting motion, consequently leading to a blue-shift of UV-vis absorption.
采用高分辨率固态（13）C 核磁共振（NMR）和光学吸收光谱研究了聚苯胺/β-环糊精包合物（PANI/β-CD IC）的分子动力学及其与光学性质的关系。紫外-可见测量显示，β-CD 包合后，PANI 薄膜的π-π*吸收峰发生了 10nm 的蓝移，表明 IC 中 PANI 的π 共轭缩短了。（13）C NMR 光谱和自旋晶格弛豫时间（T（1C））的温度依赖性分析表明，包合诱导了 PANI 链扭曲运动的加速。此外，根据 T（1C）测量的 Arrhenius 图观察到两种归因于不同扭转角模式的扭曲运动，并且扭曲频率和角度在-25°C 以上增加。这些结果表明，β-CD 包合削弱了分子间的π-π 相互作用，并增强了伴随的扭曲运动，从而导致 UV-vis 吸收的蓝移。
