具有枝状结构二阶非线性光学高分子的研究进展

Recent Advances in Second Order Nonlinear Optical Polymers with Dendritic Structure

树状分子是指一类结构高度支化的大分子或高分子化合物,其独特的三维纳米球形结构、分子内空腔以及大量富集的表面基团,可产生诸多特殊且有趣的功能及光物理性质,在化学、生物和材料等领域获得了广泛的关注和研究.本文主要综述了我们课题组在具有枝状结构二阶非线性光学高分子方面的研究进展,重点介绍了如何通过合理分子设计,发展不同类型枝状拓扑结构以有效提高材料的综合性能,并展望了该领域的今后发展趋势.

Dendritic molecules are a class of highly branched macromolecules and/or polymers having a three-dimensional, nanosized globular architecture with intramolecular cavity and numerous surface functional groups. These unique structural features can endow dendritic molecules with a lot of particular and interesting functionalities and photophysical properties, making them very attractive in many areas including chemistry, biology, materials, and so on. In the past 30 years, organic/polymeric second-order nonlinear optical（NLO） materials have been widely investigated due to their great potential in telecommunications, computing, terahertz generation, detection, and many other photonic applications. So far, one of the major challenges encountered in this field is how to translate high molecular nonlinearities（μβ） of chromophores into large macroscopic material nonlinearities（i.e. second harmonic generation coefficient, d33） efficiently, due to the strong intermolecular dipole-dipole interactions between chromophore moieties, which can make their poling induced noncentrosymmetric alignment a daunting task. According to the site-isolation principle, the dendritic structure has been well-recognized as the next generation molecular topology to modify chromophores into the ideal spherical shape that can minimize the dipole-dipole interactions significantly to improve the poling efficiency. From 2006, our group has done many systematic researches in this field with an attempt to better understand the structure-properties relationship of NLO polymeric materials. In this review, after a brief introduction of dendritic molecules and second order nonlinear optics, we will summarize our recent research work on second order NLO polymers with dendritic structure, including high generation dendrimers, hyperbranched polymers and dendronized hyperbranched polymers（a new polymer model combining hyperbranched polymer and dendrimer）. We mainly focus on the discussion how to rationally design and tailor the topological structures of the dendritic NLO polymers that can significantly enhance their comprehensive material performance through several molecular design strategies such as ＂suitable isolation group＂, ＂isolation chromophore＂ and the Ar-ArFself-assembly. Finally, a short outlook for future opportunities in advancing this field is also presented.