Liquid crystal photoalignment using new photoisomerisable Langmuir-Blodgett films

We present optical alignment studies of pure nematic liquid crystals using photoisomerisable Langmuir-Blodgett (LB) alignment layer. Monolayers of azobenzene-containing molecules exhibiting long lifetime for cis isomer are transferred on glass substrates using the Langmuir-Blodgett deposition technique. The anchoring produces homeotropic texture and the strength of this anchoring is increasing with increasing number of monolayers from 1 to 7. The exposition of the cells with UV light the spectrum of which corresponds to the absorption band of the dye in the trans conformation induces strong realignment of the LC molecules via the trans-cis photoisomerization process and the regulation of the film orientation by LCs. Such reorientation occurs mainly in the plane perpendicular to the polarization plane of the excitation.