Synthesis and Characterization of Benzylidene and Azobenzene Based Photochromic Liquid-Crystalline Polymers DEVASWITHIN JAYALATHA RATHINAM BALAMURUGAN

Abstract: Two series of novel thermotropic main chain liquid crystalline polymers containing photocross-linkable chalcone and photoisomerizable azobenzene moieties were synthesized from bis[4-(m-hydro-xyalkoxy)benzylidene]cycloalkanones [m = 6,8,10] with 4,4-azobenzene dicarbonylchloride. The chemi-cal structure of the monomers and polymers were confirmed by spectral techniques. The mesophase prop-erties were investigated using hot stage optical polarized microscopy and differential scanning calorimetry. All the polymers exhibited liquid crystalline properties. The thermogravimetric analysis data revealed that the polymers were stable up to 220 C and underwent two-stage decomposition. Photocrosslinking prop-erty of the polymers was investigated using UV spectroscopy. The cyclopentanone containing polymers showed faster photocrosslinkability than that of their cyclohexanone counterpart. In addition to the pho-tocrosslinkability of cycloalkanone units, the azo moiety displayed E-Z (trans-cis) isomerization in the polymer backbone