圆偏振光在手性聚合物合成与结构调控中的应用

手性是自然界中普遍存在的有趣现象之一,在生命体中手性大分子特有的不对称结构在维持生命过程、新陈代谢和进化等面均起着决定性作用.受此启发,合成具有新型结构的光学活性聚合物,研究其独特的物理化学性质和功能已成为当今高分子领域研究的热点.左旋和右旋的圆偏振光已被广泛应用于氨基酸衍生物的不对称光合成、光分解和去消旋化反应,以及诱导含有偶氮苯或三苯胺等特定功能基团的超分子组装体或无机纳米粒子形成稳定螺旋结构.本文详细地介绍了圆偏振光辐照在手性聚合物合成与螺旋结构调控中的应用,初步揭示了圆偏振光的作用机制以及优势,归纳总结了已取得的研究进展,并对圆偏振光在手性聚合物合成与结构调控中的应用及发展进行了简单的评述和展望.

Synthesis of Optically Active Polymer and Structural Modulation Using Circularly Polarized Light

Helical conformation is a representative secondary structure of biomacromolecules such as DNA and proteins in nature,and plays an important role in the metabolism of organisms.Partially inspired by such natural biological helices,considerable studies have been conducted on the design and synthesis of polymers with stable helical conformations in recent decades.The objectives of these researches are not only to mimic the structure and function of biological helices,but also to widen their applications in many fields,as helical polymers can display optical activity based solely on their main-chain helical conformation.In the past decades,various helical polymers,including polythiophene,polypyrrole,polyaniline and polydiacetylene (PDA),have been synthesized through asymmetric polymerization,which can proceed if chiral monomers,dopants or catalysts are involved,or if some external chiral influence is present.One such external influence is circularly polarized light (CPL),which is inherently chiral and has been regarded as one source for the origin of homochirality in nature.Left-and right-handed CPL have been applied in asymmetry photochemical reactions including photosynthetic or photolytic,and modulated the helical structure in supramolecular assemblies of azobenzene-containing compounds and inorganic nanoparticles.In this paper,CPL-triggered enantio-selective synthesis of optically active polymers,including helical polydiacetylene,chiral coordination polymers,chiral linear and hyperbranched polymers,are reviewed for the great efforts done towards the understanding of the mechanism of CPL-triggered enantio-selective polymerization,and the applications of CPL to induce chiral packing structure into azobenzene-containing polymers,polyfluorene and photo-responsive ketone-containing polymers.The enantioselective interaction between CPL and the enantiomers possibly played a key role in above asymmetric photo-polymerization reactions and the helical structural modulation.The unique features,the advantages of CPL-triggered enantio-selective synthesis of chiral polymers as well as modulation of the helical structure,and the involved mechanism are simply revealed.The progress up to now is summarized and a short prospect concerning the development of CPL triggered asymmetry photo-synthesis and structural modulation have been also provided.