Synthesis, Characterization and Non-linear Optical Properties of Polyimide and Polyimide/Silica Hybrid Materials

Anon-linear-optical (NLO) chromophore molecule and polyimide (PI) weresynthesized. The chemical structures were characterized by 1H NMR andelemental analysis. Then, a polyimide/silica NLO hybrid material with covalentlinks between the inorganic and the organic networks was synthesized using polyimide,3-aminopropyltriethoxysilane (APTES) as a coupling agent between the organic andinorganic phases, and the hydrolyzate of tetraethyl ortho-silicate (TEOS) by the sol-gelprocess. FTIR and 29Si nuclear magnetic resonance spectroscopy were used tocharacterize the structure of the hybrid. The results revealed that Q^3, Q^4 and T^3 werethe major microstructural elements in forming a three-dimensional network structure.The particle size and crystallinity were investigated using transmission electronmicroscopy (TEM) and X-ray diffraction (XRD). The differential scanning calorimeter(DSC) and thermal gravimetric analysis (TGA) exhibited the glass transitiontemperature (Tg) and the decomposition temperature (Td) of 5% mass loss in polyimideand hybrid material at 244°C and 344°C, 352°C and 447°C, respectively. A reflectiveelectro-optic (EO) modulator using this polyimide or hybrid was fabricated. Theelectro-optic (EO) coefficients 33 of the polyimide and hybrid in the EO modulator weredetermined to be 28 and 22 pm/V (poling voltage of 3.8 kV, 205°C) at 832 nm by anattenuated-total-reflectance (ATR) method and the values retained 94% for more than100 h at 205°C. The results show that polyimide and hybrid may be useful as EOmodulator.