Molecular structure modulated properties of azobenzene-substituted polydiacetylene LB films: Chirality formation and thermal stability |
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Authors: | Gang Zou Yali Wang Hideki Kohn Mitsumasa Iwamoto |
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Affiliation: | a CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, Key Laboratory of Optoelectronic Science and Technology in Anhui Province, University of Science and Technology of China, Hefei, Anhui 230026, PR China b Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan |
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Abstract: | Langmuir-Blodgett (LB) films of three novel azobenzene-substituted diacetylene monomers (DA1, DA2 and DA3) were fabricated and their optical and chiroptical properties were investigated in detail by ultraviolet-visible (UV-vis) spectra and circular dichroism (CD) spectra. Achiral DA1 molecules could form chiral LB films through overcrowded packing of the azobenzene moiety, while achiral DA2 and DA3 molecules not. When exposed to left-or right-handed circular polarized UV light (CPUL), striking left- or right-handed (opposite) CD signals for azobenzene chromophores and polydiacetylene chains were observed for the polymerized DA1 (PDA1) and DA2 (PDA2) LB films. However, DA3 LB films could hardly be polymerized in this case, and only striking opposite CD signals for azobenzene chromophores could be observed. It was demonstrated that the intermolecular steric hindrance and irregular arrangement of azobenzene chromophores were not favorable for the topo-polymerization and chirality formation of polydiacetylenes backbone. Further, the effects of thermal treatment on the supramolecular chirality of above three LB films were studied. Strong collective noncovalent interactions (π-π stacking) were believed to be responsible for the thermal stability of chiral supramolecular assemblies. |
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Keywords: | Supramolecular chirality Azobenzene-substituted polydiacetylene LB films |
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