Synthesis, Characterization and non-linear optical properties of polyimide and polyimide/silica hybrid materials

Anon-linear-optical (NLO) chromophore molecule and polyimide (PI) were synthesized. The chemical structures were characterized by 1H NMR and elemental analysis. Then, a polyimide/silica NLO hybrid material with covalent links between the inorganic and the organic networks was synthesized using polyimide, 3-aminopropyltriethoxysilane (APTES) as a coupling agent between the organic and inorganic phases, and the hydrolyzate of tetraethyl ortho-silicate (TEOS) by the sol-gel process. FTIR and 29Si nuclear magnetic resonance spectroscopy were used to characterize the structure of the hybrid. The results revealed that Q³, Q⁴ and T³ were the major microstructural elements in forming a three-dimensional network structure. The particle size and crystallinity were investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) exhibited the glass transition temperature (T_g) and the decomposition temperature (T_d) of 5% mass loss in polyimide and hybrid material at 244°C and 344°C, 352°C and 447°C, respectively. A reflective electro-optic (EO) modulator using this polyimide or hybrid was fabricated. The electro-optic (EO) coefficients 33 of the polyimide and hybrid in the EO modulator were determined to be 28 and 22 pm/V (poling voltage of 3.8 kV, 205°C) at 832 nm by an attenuated-total- reflectance (ATR) method and the values retained >94% for more than 100 h at 205°C. The results show that polyimide and hybrid may be useful as EO modulator.