Research On Organic Electro-optical Materials Based On Cross-linking Reaction/intermolecular Hydrogen Bondin

Compared with traditional inorganic second order nonlinear optical（NLO）materials,organic second order nonlinear optical materials have many advantages in terms of bandwidth,dielectric constant,half-wave voltage,electro-optical（EO）coefficient,machinability and material cost.Organic nonlinear optical materials have been extensively studied for decades due to their potential applications in computing,telecommunications,detection,functional photonic crystal construction,and terahertz generation.Currently,polarization efficiency and long-term stability are the biggest obstacles limiting the application of organic NLO materials.At the molecular level,these problems are mainly caused by the strong dipole-dipole molecular interaction between the D-π-A structure of NLO chromophore.Many polymer material systems have been developed to try to overcome this force and obtain stable and high electro-optical properties of materials,such as host-guest system,main chain polymer,side chain polymer,binary chromophore system,etc.Recently,self-crosslinking system and self-assembly system have attracted wide attention.The pure chromophore in these two systems can be self-assembled or self-crosslinked to form a single molecular glass film,which is expected to achieve polymer materials with high chromophore load density and high electro-optical coefficient,as well as good stability.Based on the above considerations,this paper uses aniline structure as the electron donor,isoflurone as the electron bridge,Trifluoromethane-phenyl-tricyanofuran（CF₃-TCF）as the electron acceptor for the structure design of chromophore molecules,through the introduction of appropriate functional groups on the donor and bridge to obtain chromophore with different functions,and made glass film to obtain high electro-optical activity of electro-optical materials,specific work is as follows:1)Two different functional groups that can undergo D-A cross-linking reaction are introduced into the donor and bridge step by step,and three chromophore groups A1,A2 and A3 are synthesized,all of which can be self-crosslinked into a single molecule film.Their thermal stability and optical properties before and after self-crosslinking were investigated by ultraviolet-visible absorption spectrum,thermogravimetric analysis（TGA）,differential scanning calorimetry（DSC）and density functional theory calculation（DFT）.The experimental results show that they all have high electro-optical coefficients.After self-crosslinking,the r33values of A1,A2 and A3 are increased from 223 pm/V,240 pm/V and 246 pm/V to 253 pm/V,273 pm/V and 280 pm/V respectively.Especially,the thermal stability of chromophore was significantly improved after self-crosslinking,and Tg was increased from about 70°C to 185°C,165°C and 158°C respectively.2)Three chromophore B1B2B3 were synthesized by introducing benzene and/or fluorobenes into the aniline double donor and bridge.Ar H-Ar F interaction in this system requires the mixing of the two chromophore,and their pure chromophore system can also form a film alone.The thermal stability and optical properties before and after self-crosslinking were studied by UV-VIS absorption spectroscopy,thermogravimetric analysis,differential scanning calorimetry and density functional theory.The experimental results show that the self-assembly effect of Ar H-Ar F helps to significantly improve the electro-optic properties of the material.The electro-optic coefficients of B1B2B3 are 176 pm/V,145 pm/V and 198 pm/V,respectively.In the self-assembled hybrid film,the electro-optic coefficients of 1:1:B1:B2 and 1:2B2:B3reached 355 pm/V and 326 pm/V,respectively.