光学活性螺旋聚(3,5-二取代苯乙炔):构象调控、手性传递与自组装

Optically Active Helical Poly(3,5-disubstituted phenylacetylene):Conformation Regulation,Chirality Transfer,and Self-assembly

聚苯乙炔衍生物是重要的动态螺旋聚合物,具有丰富可调的螺旋构象,在手性识别、对映体拆分、不对称催化、多通道传感、圆偏振发光等领域的潜在应用正受到越来越多的关注.本文总结了近年来笔者在聚(3,5-二取代苯乙炔)研究中取得的主要进展,包括:cis-cisoid螺旋构象的形成条件、影响因素与调控规律,手性双重传递模式与可调控的手性放大规律,有趣的自组装行为和超分子结构.最后,对螺旋聚苯乙炔衍生物手性功能材料今后的研究作了展望.

Poly(phenylacetylene)(PPA)derivatives are important dynamic helical polymers with rich and adjustable helical conformations,which have received ever-increasing attention due to their potential applications in the fields of chiral recognition,enantiomeric resolution,asymmetric catalysis,multi-channel sensor,circularly polarized luminescence,etc.This feature article summarizes the recent research progress of our group on poly-(3,5-disubstituted phenylacetylene),including the influencing factors and regulation rules of cis-cisoid helical conformation,a novel doublet chirality transfer(DCT)mode,the adjustable chiral amplification,as well as its interesting self-assembly behavior.By introducing intramolecular hydrogen bonding or n→π^(*)interactions,ciscisoid helix can be obtained and stabilized in solution,the formation of which can be tuned by changing the size of pendant groups,solvents,additives,and temperature,etc.Based on this disubstitution structure,a new model of doublet chirality transfer is put forward,which can be used to design various PPA functional materials and attenuate the possible antagonism.To achieve a good DCT,high cis structure of main chain,and strong intramolecular hydrogen bonds are indispensible.Different chiral amplifications in a single copolymer system,normal and abnormal"sergeants-and-soldiers"effects,can be achieved by tuning the conformational transition between cis-cisoid and cis-transoid helices,which can be well-explained by using the modified Ising model.Moreover,interesting self-assembly behavior including the self-assembly of amphiphilic rod-rod block copolymers and the conformational transition-induced self-assembly are observed in poly(3,5-disubstituted phenylacetylene).For the former,by modulating the composition of block copolymers,water contents,and initial copolymer concentration,the aggregates can transform from the spherical micelles to the worm-like micelles,multi-arm worm-like micelles,and vesicles.For the latter,hydrogen bonds driven conformation autoregulation and sol-gel transition are achieved for PPA homopolymer.The self-assembly structures can sequentially evolve from vesicles to nanobelts to helical strands during the process of conformational transition for PPA block copolymers.Finally,the future research directions of poly(3,5-disubstituted phenylacetylene)as chiral functional materials are prospected.