Synthesis, Structure, and Phase Behavior of New Chiral Liquid-Crystalline Polysiloxanes Based on Mesogenic Menthyl Monomers

摘要

Six new chiral monomers (M-1-M-6) and their corresponding side chain polymers (P-1-P-6) containing menthyl groups were synthesized. The chemical structures Of M-1-M-6 were characterized with FTIR and H-1 NMR. The structure-property relationships of the monomers and polymers obtained are discussed. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction measurements. Some compounds containing menthyl groups formed mesophase when a flexible spacer was inserted between the mesogenic core and the menthyl groups by reducing the steric hindered effect. The monomers M-1, M-4, and M-5 did not reveal mesomorphic properties because of the weaker rigid core or the longer flexible terminal groups, whereas M-2, M-3, and M-6 all revealed cholesteric phase. Except P-4 and P-5, the homopolymers P-1-P-3 and P-6 showed a smectic A phase. In addition, melting, glass transition temperature, or clearing temperature increased, and the mesophase temperature range widened with increasing the rigidity of mesogenic core or decreasing the length of the flexible spacer. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 3016-3025, 2009