Optical and mesomorphic properties characterisation of chiral liquid crystalline copolysiloxane exhibiting cholesteric and blue phases

Abstract

A series of liquid crystalline polymers (LCPs) have been synthesised by two cholesteric monomers M 1 , M 2 and a nematic monomer M 3 . The chemical structures and liquid crystalline properties of the monomers and polymers have been characterised by FTIR, 1 H-NMR, differential scanning calorimetry, thermogravimetric analyses, X-ray diffraction measurements and polarising optical microscopy. All LCPs show a high thermal stability with wide mesophase temperature ranges. For polymer P 1 bearing only cholesteric LC monomers component, it shows a cholesteric phase, whereas others display a blue phase besides a cholesteric phase. The formation of the blue phase is based on the structures of the polymers and the produced biaxial helix. The glass transition temperature and isotropic temperature of the polymers decrease on heating cycle with increasing the content of M 3 in the polymers. The specific rotation values of the polymers are temperature-sensitive. The reflection spectra of polymers P 1 -P 6 show that the maximum reflected wavelengths shift to long wavelength with increasing the content of M 3 in the polymer systems. The frequency and intensity of the bands change sharply at the temperature where cholesteric phase changes to blue phase, but they show a weak dependence on temperature in the blue phase.

Influence of chemical structure on the optical properties of new side-chain polymers containing cholesterol

“…The LC properties of cholesteric side-chains depend on the nature of the polymer backbone, the type of mesogen, the flexible spacer length, the arrangement of the C = O group and so on. [5][6][7][8][9][10] In addition, cholesteric polymers show good processability compared with low-molarmass cholesteric materials as well as long-term stability of the cholesteric mesogenic order at temperatures less than the glass transition temperature. Numerous researchers have investigated the possibility of sidechain cholesteric polymers with cholesterol in different alkylene spacers.…”

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

“…Chiral liquid crystals (LCs), including chiral smectic phase, [1][2][3][4][5][6] chiral nematic phase, [2,[5][6][7][8][9] cholesteric phase, [4,[10][11][12] blue phase [12][13][14][15] and so on, have attracted much interest because of their unique optical and electrical properties, such as the selective reflection of light, [3,5,7,8,12] thermochromism [16,17] and ferroelectricity. [1,6,18,19] Fluorinated LCs are a class of important LCs for their fascinating properties such as the high polarity, dielectric anisotropy, optical anisotropy and viscoelastic properties.…”