Bordyuh H. Electrooptical and nonlinear-optical properties of lyotropic ionic liquid crystals with electrochromic admixtures

This work presents the results of experimental studies of structural, electrooptical and nonlinear-optical properties of lyotropic ionic liquid crystals (LILC) with soluted electrochromic admixtures of viologens. It is determined that LILC of potassium caprylate with viologen admixtures form double-layer Smectic A phase which is characterized by electrostatic interlayer of metal cations, water and negatively charged oxygen atoms between alkyl chains. It is found, that viologen admixtures (2-4 % by weight) are harmonically built into liquid crystal matrix without breaking its order. At the same time LILC arrange viologen molecules. It is shown that LILC-viologen composites obtain electrochromic properties inherent to viologens, which produce coloured radical cations and dimers while reducing. The presence of radical cations and dimers is fixed by optical absorption spectra. It is established that under the action of an electric field samples of LILC-viologen form bi-layer structure consisting of a liquid crystal layer and an absorptive layer of viologen redox products (radical cations and dimers). A dynamic grating recording was realized and studied in bi-layer LILC-viologen cells. It is determined that recording takes place in the coloured layer of viologen redox products. The possible mechanism of grating recording in LILC-viologen cells is suggested and lies in reversible photoconversion between dimers and radical cations of viologens under the action of laser irradiation.