Study On The Preparation And Properties Of Novel Second-Order Nonlinear Optical Polymeric Films

Recently, various novel and high performance second-order nonlinear optical(NLO) organic polymer materials, owing to their wide application in electro-optical(E-O) modulated devices and advantages superior to inorganic materials, have beenprepared and investigated by numerous scientists. It is still considered to be achallenge for researchers to prepare novel polymer lattices with macroscopicallynon-centrosymmetric structure and in which chromophoric dipolar moleculesarranged with orientation.In this dissertation, a promising methodology for fabricating high thermallystable organic second-order NLO thin films containing low molecular weightchromophoric (LMWC) molecules was sustained by the electric field-inducedlayer-by-layer assembly. The new LMWC molecule but-2-enedioic acidmono-[2-({4-[4-(2-carboxy-2-cyano-vinyl)-phenylazo]-phenyl}-methyl-amino)-eth-yl]ester(BCPE) was first designed and synthesized successfully, which possessestwo negative groups at both ends and still retains the molecular polarity afterionized. Under the dc electric field, the density of the oriented chromophores BCPEdeposited on the substrate is increased largely and upon the UV irradiation,accompanied with the transition of the ionic bonds between the layers to covalentbonds, the resulting NLO films possess excellent environmental stability and highthermal stability (the resulting films can retain 92 % of the polar order up to 200°C), which may rival the properties of the latest poled polymer films forelectro-optic devices.