Surface-assisted photoalignment control of lyotropic liquid crystals. Part 2. Photopatterning of aqueous solutions of a water-soluble anti-asthmatic drug as lyotropic liquid crystals

摘要

The photocontrol of the alignment of aqueous solutions of an anti-asthmatic drug, disodium chromoglycate (DSCG), as a lyotropic liquid crystal (LLC), was performed by irradiation of a thin film of (4-phenylazophenyl methacrylate) with linearly polarised light. The addition of a non-ionic surfactant to the LLC is a necessary condition to performing the alignment photocontrol because of the generation of nematic phase. The orientational direction of molecules of the drug was perpendicular to the electric vector of the actinic light, suggesting that columnar supramolelcular aggregates composed of stacked DSCG molecules aligin in parallel with the long molecular axis of photooriented azobenzene chromophores, which lies in an orthogonal position with respect to the electric vector of the light. A general guideline for the photoalignment control of LLC is discussed on the basis of the results for DSCG and for a water-soluble dye, C.I. DIrect blue 67, reported in Part 1 of the series.