Department of Chemistry, University of Colorado Boulder, Boulder, CO, USA.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Nat Chem. 2021 Jul;13(7):660-665. doi: 10.1038/s41557-021-00686-2. Epub 2021 May 3.
Double helical conformation of polymer chains is widely observed in biomacromolecules and plays an essential role in exerting their biological functions, such as molecular recognition and information storage. It has remained challenging, however, to prepare synthetic helical polymers, and those that exist have mainly been limited to single-stranded polymers or short oligomeric double helices. Here, we report the synthesis of covalent helical polymers, with a high molecular weight, from the achiral monomer hexahydroxytriphenylene through to spiroborate formation. Polymerization and crystallization occurred simultaneously under solvothermal conditions to form single crystals of the resulting helical covalent polymers. Characterization by single-crystal X-ray diffraction showed that each crystal consisted of pairs of mechanically entwined polymers. No strong non-covalent interactions were observed between the two helical polymers that formed a pair; instead, each strand interacted with neighbouring pairs through hydrogen bonding. Each individual crystal was made up of helical polymers of the same handedness, but the crystallization process produced a racemic conglomerate, with equal amounts of right-handed and left-handed crystals.
聚合物链的双螺旋构象在生物大分子中广泛存在，对发挥其生物功能（如分子识别和信息存储）起着至关重要的作用。然而，制备合成的螺旋聚合物一直具有挑战性，而且现有的聚合物主要限于单链聚合物或短的寡核苷酸双螺旋。在这里，我们报告了通过手性单体六羟基三苯通过螺环硼酸盐形成来合成高分子量的共价螺旋聚合物。在溶剂热条件下，聚合和结晶同时发生，形成了所得螺旋共价聚合物的单晶。通过单晶 X 射线衍射进行的表征表明，每个晶体都由一对机械缠绕的聚合物组成。形成一对的两个螺旋聚合物之间没有观察到强的非共价相互作用；相反，每个链与相邻的对通过氢键相互作用。每个单晶由相同手性的螺旋聚合物组成，但结晶过程产生了外消旋混合物，其中等量的右旋和左旋晶体。
