Microstructure and optical properties of nematic and cholesteric liquid crystals doped with organo-modified platelets

• Published in: Journal of molecular liquids Vol. 267; pp. 279 - 285
• Main Authors: Bulavin, L.А., Lisetski, L.N., Minenko, S.S., Samoilov, A.N., Klepko, V.V., Bohvan, S.I., Lebovka, N.I.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2018
• Subjects: Cholesteric; Laponite® platelets; Liquid crystal colloids; Optical density; Organomodified; X-ray diffraction; X-ray diffraction; Organomodified; Liquid crystal colloids; Cholesteric; Laponite® platelets; Optical density
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2017.12.078

The nematic (5CB) and cholesteric (the mixture of 5CB with chiral M5) liquid crystals (LC) doped with organo-modified inorganic platelets Laponite® (LO) were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), microscopic image analysis, and optical density measurements. Cetyl-trimethylammonium-bromide (CTAB) was used as an organo-modifier and “cold” and “hot” methods were applied for obtaining of LOc and LOh samples, respectively. The data of DSC and XRD for nematic 5CB+LO compositions evidenced the presence of strong interactions between 5CB molecules and LO platelets and the better exfoliation for LOc as compared with LOh platelets. Microscopic structure, optical density and selective reflection for cholesteric compositions evidenced the strong integration of LOc platelets inside LC medium. The observed optical behavior reflects combination of initial perturbation of cholesteric matrix by LOc particles and initiation of formation of topological defects at small concentration of LOc, C<0.1%, as well as the partial trapping of LOc by large scale oily streaks at higher concentrations, C≥0.1%.
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•Nematic and cholesteric liquid crystal (LC) colloids doped with organo-modified Laponite® (LO) were studied.•Organo-modified platelets were obtained by “cold” (LOc) and “hot” (LOh) methods.•Data of DSC and XRD evidenced the presence of strong interactions between LC and LO platelets.•LOc platelets were better exfoliated in LC structures than LOh platelets.•Partial trapping of LOc by cholesteric oily streaks at high concentrations of LOc, C≥0.1%, was observed.