Optical properties of heterogeneous nanosystems based on montmorillonite clay mineral and 5CB nematic liquid crystal

The effect of montmorillonite (MMT) clay modification with surfactant cations on the electrooptical properties of the LC-clay nanocomposites consisting of MMT and 4-pentyl-4′-cyanobiphenyl (5CB) nematic liquid crystal was investigated depending on the composite preparation method. We showed that only composites consisting of MMT modified with organic surfactants (alkylbenzyldimethylammonium chlorides with alkyl chain length C14-C18) display electrooptical memory effect and contrast. Adding a polar additive (acetone) to the mixture during the composite preparation considerably improves the homogeneity of the composites and their electrooptical performance. Using IR and Raman spectroscopy methods it was shown that in the LC-organoclay composites mutual interaction between the components takes place, which results in alignment of the near-surface layers of both organic and inorganic components of the composite. Due to such interaction, these systems display electrooptical contrast and memory effect. The LC-clay composites consisting of organophobic Na-MMT do not display electrooptical effect because of the absence of interaction between the components, which is confirmed by the IR and Raman spectroscopy data.