Preparation, characterization and electro-optic properties of polyimide/SiO2 nanohybrid materials

A series of the polyimide-silica NLO nanohybrid materials were synthesized from 3,3´, 4,4´- Bisphenyltetracarboxylic (BPDA), 2,2-Bis(3-amino-4-hydroxyphen-yl) 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 contents in the hybrids were varied from 0 to 22.5/wt%. The prepared polyimide/silica hybrids were characterized by FT-IR, differential scanning calorimeter (DSC), 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) at 5% mass loss were in the range 215~364degC and 320~430degC, respectively. These results showed that these hybrid materials had excellent thermal stability. The hybrid solutions could be spin coated on the indium-tin-oxide (ITO) glass to form optical quality thin films. The electro-optic coefficients (gamma₃₃) at 832 nm for polymer poled were in the range of 21-50 pm/V and the values remained well (retained > 88% for more than 100 h). The experimental results suggest that the hybrid thin films have potential applications as passive films for optical devices.