Chiral structures can be seen everywhere in nature, ranging from cosmic nebula to snail and morning glory vine. For a long time, chemists have been using chiral phenomena to construct chiral structures at different scales and endow them with unique biological and catalytic properties. At the molecular level, there are structures with both toroidal and chiral characteristics, such as cycloalkanes with chiral carbon, which show boat or chair conformation; In topology, the Mobius ring with peculiar properties is also a structure with both toroidal and chiral characteristics. However, as far as we know, the hierarchical structure with both toroidal and chiral characteristics at the nano scale has not been reported.
Recently, our group has made discoveries in the preparation of chiral toroidal nanostructures. The study found that a binary system of poly(γ- Benzyl-l-glutamate) (PBLG) homopolymer and poly(γ- The binary system of benzyl-l-glutamate) - block polyethylene glycol (PBLG-b-PEG) block copolymer was self-assembled in solution to form hierarchical nanostructures of helical toroids with uniform size and controllable chirality. By adjusting the blending ratio of block copolymer and homopolymer, it is found that the toroidal structure is formed by homopolymer assembly. Further studies show that the formation of the chiral toroids is a successive two-step self-assembly process: first, the polypeptide homopolymers self-assemble to form uniform toroidal structure, and then the block copolymers self-assemble on the homopolymer toroids and result in helical surface patterns.
It is worth noting that the surface helical patterns of the chiral toroids formed by the self-assembly of PBLG-b-PEG / PBLG system is a right-handed chirality (Fig. a). Using PBDG-b-PEG with opposite chiral polypeptide blocks for self-assembly, chiral toroids can also be obtained, but the surface helical patterns are left-handed chirality (Fig. b); However, if PBDG-b-PEG and PBLG-b-PEG block copolymers are uesd to co-assemble with PBLG homopolymer, toroidal structures with achiral surface patterns can be obtained (Fig. C). The research work first reported the construction of chiral toroidal hierarchical structures at the nano scale, which further deepened the understanding of curve-confined self-assembly and the regulation law of curve chirality, and provided a reference for the construction of various complex hierarchical nanostructures.
The work was completed by Pengfei Xu, a doctoral student of materials, and Gao Liang, a young scholar, under the guidance of Professor Chunhua Cai and Professor Jiaping Lin. The related work was published in Angew. Chem. Int. Ed. (DOI: 10.1002/anie.202004102). under the title of Helical Toroids Self-Assembled from a Binary System of Polypeptide Homopolymer and Its Block Copolymer and has been selected as hot paper.
Original link：https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202004102