Abstract
A new type of thermotropic liquid-crystalline photosensitive supramolecule was fabricated by ionic self-assembly of polyelectrolyte and functional unit azobenzene ionic liquid crystal (azo-ILC). It was found that the thermal and phase behaviors can be modulated by changing of the spacer length (4, 6, or 12 methylene units designated PAZO4, PAZO6, and PAZO12, respectively). Highly ordered liquid-crystalline structure with a lamellar morphology of different d-spacing was observed. The photoinduced orientation of azobenzene groups in thin films of the obtained ionic-bonding supramolecules was studied by polarized UV−vis and FTIR. Under the irradiation of pulsed laser, very effective induction of optical anisotropy with the preferred direction perpendicular to the pulsed polarization was observed. Typically, the maximum in-plane orientation order (S) of −0.93 for PAZO12 at maximum absorbance was achieved after irradiation and subsequent anneal at its liquid-crystalline temperature. It was found that the maximum S can be increased by increasing the clearing temperature of the photosensitive material. These results may provide guidelines for the design of effective photoinduced anisotropic materials. Furthermore, uniform alignment control of low-molecular-weight liquid crystals on the oriented supramolecular films was achieved.
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