Synthesis and characterization of novel nonlinear optical polyimide

Abstract

Nonlinear optical (NLO) polymers have attracted extensive attention because of their potential applications in integrated optical devices such as optical switching, frequency conversion and high-speed electro-optic (EO) devices. However, the stability and optical loss of currently used polymers limit their applications. It is very important to develop NLO polymers with better transparency and higher stability without sacrificing other properties. This study focused on the development of new side-chain NLO polyimides based on the novel fluoronitroaryl diaminoazobenzene chromophores and polyimide/silicon composites. The effects of the fluorine and the fluorine position in the chromophores on the structures and properties of the chromophores and polyimides were studied. The influences of the silicon network on the properties of the composite films were also investigated. Two novel fluorinated diaminoazobenzene chromophore monomers and their nonfluorinated analogues, which can be used for synthesis of side-chain NLO polyimide, were successfully synthesized. The new fluorinated diaminoazobenzene chromophore monomers have very good thermal stability and large hyperpolarizability. It was found that the incorporation of fluorine into the chromophore can lead to higher thermal stability. The fluorine position can lead to the different maximum absorption wavelength Xmax and thermal stability. Three series of novel NLO polyimides based on the fluorinated diaminoazobenzene chromophores and their analogue were successfully synthesized. All NLO polyimides possess high thermal stability, excellent transparency (km^: 298.5-355 nm) and large xix