Effects of montmorillonite modification on optical properties of heterogeneous nematic liquid crystal – clay mineral nanocomposites

Abstract

Investigations of montmorillonite (MMT) clay mineral modification effects on electro‐optical properties of nanocomposites, based on the nematic liquid crystal 4‐pentyl‐4′‐cyanobiphenyl (5CB) and MMT have been carried out. Only the composite with MMT modified by an organic surface‐active substance, dioctadecyldimethylammonium chloride, has been shown to manifest electro‐optical memory effect and contrast. A polar dopant (acetone), added to the mixture, significantly increases composite homogeneity. Results of IR spectroscopy measurements lead to the conclusion, that there is a mutual influence of components on each other in organoclay systems, which appears as an alignment of near‐surface layers of both the organic and inorganic components of the composite. Due to such interactions these systems show electro‐optical contrast and memory effect. A composite with organophobic Na‐MMT does not show these electro‐optical properties, due to the absence of component interactions, as shown by IR spectroscopic data.

Acknowledgments

This work was carried out with financial support of the National Academy of Science Ukraine under the ‘Nanophysics and nanoelectronics’ program (NVC 89‐297‐23 project).