Preparation and characterization of all organic NLO sol-gel materials based on amino azobenzene dyes

A series of NLO active chromophores based on amino azobenzene dyes have bee n synthesized by diazotization reaction. All organic NLO-active materials w ere obtained by introducing the chromophores into (hydroxymethyl)-benzoguan amine (HMBG) systems by a sol-gel process. All the sol-gel materials exhibi t excellent optical transparency. Morphology, thermal and optical propertie s of these polymers have been characterized. These NLO-active polymers can be classified into reactive systems and guest-host systems. In the reactive systems, the chromophores were condensed with HMBG in the sol-gel process. In the guest-host systems, the nonreactive chromophores were simply doped into HMBG matrix. A second harmonic coefficient, d(33), of 23.2 pm/V has be en obtained. Moreover, a systematic investigation of variation of chromopho ric chemical structures on NLO properties has been investigated. Covalent b onding effect between chromophore and benzoguanamine as well as steric effe ct are shown to greatly enhance the temporal stability for these NLO-active sol-gel systems.