Synthesis and characterization of α-methylstilbene- and azobenzene-based thermotropic liquid crystalline polymers

A series of combined liquid crystalline poly(bis-4,4'-oxy-alpha-methylstilbene-4-substituted (X) phenylazo-4'-phenyloxydecylphosphate ester)s bearing photoreactive mesogenic units were synthesized. FTIR and H-1 NMR spectroscopy confirmed the structures of these polymers. The inherent viscosities of the polymers were found to be in the range 0.45-0.65 dL g(-1). Polarizing optical microscopy (POM) exhibited birefringent liquid crystalline melt properties. The thermal properties of all of the polymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The photochemical properties of these polymers were studied by UV-visible and fluorescence spectroscopy. The influence of the photoinduced E-Z (trans-cis) isomerization of the various terminal substituents of the side-chain azobenzenes was investigated. The kinetics of the photoisomerization process reveal the switching times for the conversion between the trans- and cis- forms of the azobenzene units. The photo-optical properties of these polymers exhibited layered smectic phases and showed good photoinduced properties in their mesomorphic states. (c) 2005 Society of Chemical Industry.