Study On The Synthesis And Properties Of Electro-optic Materials With Lateral Hydrogen Bonds

The Organic second-order nonlinear optical (NLO) materials have attracted considerable attention due to their potential applications in the fields of information storage, electro-optic modulator, and optical signal processing and so on. And they are becoming the key materials in the future photon era of information transmission. The optical properties of these materials are derived from molecules or groups which contain nonlinear optical activities (that is chromophore), so the crucial challenge is to design and synthesize NLO chromophore with high EO efficiency. Through the great efforts of scientists for decades, a great number of NLO chromophores with large values of β have been developed. It is still the biggest challenge to design the high efficent chromophore to maximize the nonlinear optical effect of the material and meanwhile maintain the good stability. In recent years, many superamolecular materials with NLO activity obtained by self-assembly through non-covalent interactions have been reported. The introduction of the non-covalent bond plays a significant role in optimizing the NLO materials as expected.In this paper, the recent progress in the NLO materials, especially the materials containing non-covalent interaction, was reviewed. In order to improve electro-optic (EO) coefficient and stability, a series of novel NLO chromophores with lateral hydrogen bonding sites was designed and synthesized. The interaction of intermolecular hydrogen bonding and EO properties were also studied.The structures of chromophores were characterized by1NMR, MS, Elementary analysis, IR and UV-vis. Their structures and the interaction of lateral hydrogen bonds were confirmed. The solutions of chromophores were coated on ITO conductive glass by using spin-coating, the films were poled through corona poling. The chromophore orientation degree was determined by testing the ultraviolet absorbance of the thin films before and after polarization, according to the formula:Φ=1-A1/A0(Φ is orientation degree, Ao is the absorbance before polarization, A1is the absorbance after polarization). It was proved that the orientation degree of sample3and sample4obtained by self-assembly through hydrogen bonding are about3-4times than sample1and sample2of the doped system. After a period of time, the result obviously display the relaxation of sample3and sample4are less than sample1and sample2, and the polarization orientation degree of sample4remained at more than90%after2months due to more intermolecular hydrogen bonding interaction. The EO coefficient r33of polarized thin films, which chromophores of NLO-1, NLO-2, NLO-3and NLO-4respectively doped with APC, is11pm/V、10pm/V、23pm/V、20pm/V，the EO coefficient r33of PU is21pm/V, and the EO coefficient r33of superamolecular systems, which are made of NLO-3、NLO-4by intermolecular hydrogen bonding interaction, is31pm/V、34pm/V. These results showed that hydrogen bonding interaction can effectively improve the EO coefficient and stability.Finally, the research work was summarized. The application of organic second-order nonlinear optical materials and the future research work were also prospected.