Nonlinear Optical Polymer Films Based on Sol-Gel Derived Polysilsesquioxane with Pendant Chromophoric Subunits Embedded in Size-matched Pores

Abstract

Two new hybrid nonlinear optical (NLO) polymeric films have been fabricated from the corresponding monomers, α, ω-bis(trimethoxysilyl)-1,4-dipropoxybenzenes bearing one or two moieties of pendant groups of N-(4)-nitrophenol-(L)-prolinol (NPP) on the spacer respectively by molecular design and “in-situ poling and sol-gel” process. These films are of enhanced thermal stability, extended temporal stability and higher second harmonic generation (SHG) susceptibilities. Their d33 values are 2.0 × 10−8 esu and 3.2 × 10−8 esu., respectively. These properties can be ascribed to the molecule-level embedment of NPP moieties in size-matched pore of the polysilsesquioxanes and fixation of the orientation of the poled chromophore given by the pore formed after the alignment of NPP moieties. The structures and morphologies of the two polymeric films investigated by XRD, FT-IR, DSC, TGA, AFM, etc. show a close correlation with the SHG properties.