Synthesis and characterization of bi-functional photorefractive hyperbranched polyisophthalesters

A series of novel bi-functional photorefractive (PR) hyperbranched polyisophthalesters (HPIPEs) with pendant end carbazolyl and azo groups, acting as photoconductors and electro-optic (EO) chromophores, respectively, were synthesized by modifying the HPIPE with N-hydroxyethyl carbazole and 4-(p-nitrophenylazo) (N-ethoxyl-N-methyl)aniline. These obtained PR polymers were then characterized by UV-vis and IR spectrum, H-1-NMR, elemental analysis, gel permeation chromatography (GPC) measurements and thermal analysis. As expected, due to their three-dimension molecular structures, the lower glass transition temperatures (21-49degreesC) were obtained in the absence of plasticizers, which provide a necessary free volume for the EO chromophores reorientation. The acceptable thermal stability, as well as the degradation temperatures of 205-260degreesC, was also determined by thermogravimetric analysis (TGA). The two-beam coupling experiments of HPIPE-25Azo theoretically containing 25% azo end groups showed that a high gain coefficient of 59cm(-1) was obtained at the applied electric field of 80 V mum(-1). Copyright (C) 2004 John Wiley Sons, Ltd.