Synthesis, characterization and electro-optic properties of polyimide/silica hybrid via sol-gel technique

A series of the polyimide-silica NLO hybrid materials were synthesized from 4,4'-(Hexafluoroisopropylidene)-diphthalic Anhydride (6FDA), 2,2-Bis(3-amino-4-hydroxyphenyl) hexafluoropropane (6FHP), nonlinear optical (NLO) molecule 4-(N-2-Hydroxyethyl-N-methylamino)-4'-[(6-nitroben-zothiazol-2-yl)diazenyl]azobenzene (HNBDA), coupling agent APTES and hydrolysate of TEOS via sol-gel process. The TEOS content in the hybrid films was varied from 0 to 22.5wt%. The prepared polyimide/silica hybrids were characterized by IR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Transmission Electron Microscope(TEM), X-ray diffraction(XRD) etc. The glass transition temperature (T-g) and the decomposition temperature (T-d) were in the range 216 similar to 366 degrees C and 321 similar to 438 degrees C respectively for materials. These results show that these hybrid materials had an excellent thermal stability. The electro-optic coefficients (gamma(33)) at the wavelength of 832 nm for polymer thin films poled were in the range of 21 similar to 35 pm/V and the values remained well (retained >85% for more than 100 h). The experimental results suggest that the hybrid thin films have potential applications as passive films for optical devices.