Photoactive, liquid-crystal line, hyperbranched benzylidene polyesters: Synthesis and characterization

A novel photoactive, liquid-crystalline, hyperbranched benzylidene polyester (PAHBP) was synthesized from a dilute solution of an A(2) photoactive monomer [bis(4-hydroxybenzylidene)-4-phenyl cyclohexanone] and a B-3 monomer (1,3,5-benzene tricarboxylic acid chloride) by the solution polycondensation method in the presence of pyridine as a condensing agent. PAHBP was thoroughly characterized by Fourier transform infrared, H-1 and C-13 NMR, ultraviolet-visible spectrometry, and gel permeation chromatography. The inherent viscosity of the polymer was 0.35 dL/g in tetrahydrofuran. The degree of branching was 0.53, which confirmed the branched architecture of the polymer. Furthermore, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy were used to examine the thermal stability and thermotropic liquid-crystalline properties of the hyperbranched polyester. The polymer exhibited a nematic mesophase over a wide range of temperatures. The photoreactivity of PAHBP was studied by photolysis under ultraviolet light. (c) 2005 Wiley Periodicals, Inc.