Supramolecular polymer with ring topological structure

"Structure determines nature and nature determines use", which is the principle that material researchers have been following Different molecular structures often lead to different molecular properties In the field of polymer, topological polymer is different from linear polymer because of its unique morphology Among them, the ring polymer is more special The ring polymer has no end group, so its intermolecular entanglement is less, and it has unique solution properties, hydrodynamic volume, refractive index, intrinsic viscosity and so on Moreover, these properties are not only reflected in synthetic materials, but also in organisms: the ring protein has stronger chemical stability and thermodynamic stability than the linear protein However, due to the design difficulties, few people can combine the ring topology with the supramolecular polymer Fig 1 A) molecular structure of two monomers; b) 2 Schematic diagram of the formation of cyclic supramolecular polymer (sp ring), spiral polymer (SP helical) and linear polymer (SP ext) (photo source: angel Chem Int ed.) recently, Shiki yagai, Chiba University, Japan Based on the previous research, the professor prepared a ring polymer with high polymerization stability and light response (Fig 1b) A barbituric acid substituted naphthalene derivative (Fig 1a, 2) has been synthesized by the authors This compound can form spiral supramolecular polymer SP helical under the control of thermodynamics Based on this study, the authors found that 2 can not only form the cyclic supramolecular polymer sp ring (Fig 1b, III), but also disintegrate into the linear polymer SP ext (Fig 1b, V) This achievement was published in angelw Chem Int ed (DOI: 10.1002 / anie 201811237) under the title of "photoresponsive circular polymer: topological trapand photoinduced ring opening reinforcement" Fig 2 A) schematic diagram of sp ring formed by light monomer 2; B-E) AFM diagram of solution in different time periods after adding MCH; F) tem diagram of cyclic supramolecular polymer (picture source: angel Chem Int ed.) the author first studied the phenomenon of supramolecular polymerization of 2 Due to the characteristics of 2, only about 50% of 2 in the solution can be transformed from trans to CIS in light (Fig 2a, I) However, the monomer in the solution did not aggregate immediately after the introduction of the bad solvent methylcyclohexane (MCH) into the solution (Fig 2b) With the extension of time, the cis-2 gradually converted to the trans-2, and then the monomer in the solution gradually gathered and showed obvious ring structure (Fig 2c-e) TEM images show that the sp ring formed by 2 has a regular hexagonal lattice structure (Fig 2f), and its average size is consistent with the polymer obtained by thermodynamics, which shows that the ring polymer monomer is a flower like hexamer formed by 6 trans-2 Then, from the point of view of topological structure, some properties of ring-shaped supramolecular polymer were studied The results show that the mechanical stability of sp ring is not only higher than that of linear polymer, but also higher than that of spiral SP helical (Fig 3, a-b) In the study of its elongation, the author found that sp ring can hold up to two cis-2 in each hexamer without destroying its ring structure (Fig 3, C-D) Fig 3 Mechanical stability and elongation of sp ring and SP helical (photo source: angel Chem Int ed.): the author obtained two polymers with different topological structure through different polymerization of one monomer, and one of them has high polymerization stability and light response Full text author: Shiki yagai, bimalendu Adhikari, Keisuke aratsu, and joyal Davis.