Photoinduced supramolecular chirality in side-chain liquid crystalline azopolymers
Photoinduced supramolecular chirality in side-chain liquid crystalline azopolymers
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DOI：
10.1039/b518269g
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发表时间：
2006-04
影响因子：
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通讯作者：
R. Tejedor;M. Millaruelo;L. Oriol;J. Serrano;R. Alcalá;F. Rodríguez;B. Villacampa
中科院分区：
文献类型：
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作者：
R. Tejedor;M. Millaruelo;L. Oriol;J. Serrano;R. Alcalá;F. Rodríguez;B. Villacampa
合成并表征了一系列侧链上含有光致异构化氰基偶氮苯基团的液晶均聚物。对这些聚合物的薄膜进行了加工，研究了它们在488 nm圆偏振光照射下的吸收光谱和圆二色谱响应。用UV-Vis光谱研究了偶氮苯单元的聚集倾向和光照对电子光谱的修饰。在圆偏振光的照射下，偶氮聚合物产生了光致圆二色反应，这表明H-聚集体中的偶氮苯发色团具有手性取向的超分子结构。光致超分子有序取决于聚合物的结构，即柔性间隔基团的玻璃化转变温度和长度，以及液晶相的性质。反手圆偏振光照射后，得到了相同的吸收光谱和反向圆二色谱，这是由于对映体超分子结构的光诱导所致。光诱导超分子手性的Tg以上热稳定性由聚合物结构决定。
A series of liquid crystalline homopolymers that have photoisomerizable cyanoazobenzene groups in the side chain has been synthesized and characterized. Thin films of these polymers have been processed in order to study the absorption spectra and circular dichroism responses after illumination with 488 nm circularly polarized light. The tendency of the azobenzene units to aggregate and the modification of the electronic spectra by illumination were studied by UV-vis spectroscopy. Illumination with circularly polarized light of the azopolymers gave rise to a photoinduced circular dichroism response, which suggests supramolecular structures with a chiral orientation of the azobenzene chromophores in H-aggregates. The photoinduced supramolecular order depends on the polymer structure, i.e., on the Tg and the length of the flexible spacer, and the nature of the liquid crystal phase. Identical absorption spectra and reverse circular dichroism spectra were obtained after irradiation with circularly polarized light of opposite handedness and this is due to the photoinduction of enantiomeric supramolecular structures. The thermal stability above Tg of the photoinduced supramolecular chirality is determined by the polymer structure.