Molecular Crystals and Liquid Crystals, Vol.529, 25-31, 2010
Synthesis and Characterization of Azobenzene-Functionalized Hyperbranched Polymers
Azobenzene functionalized hyperbranched polymers (HBAzPs) have been synthesized by polycondensation of 4,4'-di((2-hydroxyethoxy)azobenzene and 1,3,5-benzenetricarboxylic acid chloride in presence of triethylamine at room temperature through A2+B3 polymerization approach. The structure and properties of HBAzPs were characterized by 1H NMR, IR, GPC, DSC and UV-Visible spectrometry. Molecular weights as well as properties of HBAzPs were found to be greatly influenced by molar ratio of monomers, amount of triethylamine and monomer concentration. HBAzP solutions in THF showed absorbances at 356nm and 450nm corresponding to -* and n-* electronic transitions of azobenzene chromophores, respectively. A reversible trans-cis photoisomerization of HBAzPs was observed upon irradiation of UV and visible light.