Synthesis and characterization of a series of smectic liquid crystalline elastomers



A series of new smectic and cholesteric liquid crystalline elastomers was prepared by graft polymerization of mesogenic monomer with the chiral and nonmesogenic crosslinking agent using polymethylhydrosiloxane as backbone. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (1H-NMR). The mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction measurements (XRD). M1 showed smectic (SB, SC, SA) and nematic phases during the heating and the cooling cycles. Polymer P0 and elastomer P1 exhibited smectic B phase, elastomers P2–P5 showed smectic A phase, P6 and P7 showed cholesteric phase, and P8 displayed stress-induced birefringence. The elastomers containing less than 15 mol % M2 displayed elasticity and reversible phase transition with wide mesophase temperature ranges. Experimental results demonstrated that the glass transition temperatures decreased first and then increased; melting temperatures and the isotropization temperatures and the mesophase temperature ranges decreased with increasing content of crosslinking unit. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 498–506, 2005