New thermochromic liquid-crystalline polymer: Synthesis and phase behavior

A series of new thermochromic side-chain liquid-crystalline polymers were prepared. The chemical structures of the resulting monomers and polymers were characterized by element analyses, FTIR, 1H-NMR, and 13C-NMR. Their mesogenic properties were investigated by differential scanning calorimetry, thermogravimetric analyses, polarizing optical microscopy, and X-ray diffraction measurements. The influence of the content of dye groups on phase behavior of the polymers was discussed. The polymers P 1-P3 showed smectic phase, and P4-P7 revealed cholesteric phase. The polymers containing less than 30 mol % of the dye groups showed good solubility, reversible phase transition, wider mesophase temperature ranges, and higher thermal stability. Experimental results demonstrated that the clearing temperature and mesophase temperature ranges decreased with increasing the concentration of the dye groups. © 2005 Wiley Periodicals, Inc.