Synthesis, Structure And Supramolecular Assembly Of Oligocyclic Polyesters

Cyclopolymers,as an important class of polymers,can form functionally diverse nanomaterials through molecular assembly for application in different disciplines.In this paper,a series of cyclic polyesters are designed and synthesized.The rigid components and soft ones appear alternately in these cyclomers,and the supramolecular monomers with different stereo structures are formed by the self-folding of rigid/soft units in the ring,and then different supramolecular aggregates are obtained by using the self-assembly properties between these units.Specifically:1.In the study,the ester groups were used as the soft component and the phenyl groups as rigid component.Applying the principle of topology,the soft components and the rigid ones are regarded as points and lines respectively.Five cyclic polyesters with different closures such as holes,caves and cavities are obtained with the help of the periodic alternation of these points and lines.Further,a larger molecular tunnel is obtained through intermolecular meshing based on cave-like cyclic polyesters.2.The topological structure and relative molecular assembly properties of the five cyclic polyesters were revealed from different angles by means of X-ray,NMR,MS and DFT theoretical calculation:(1)From the X-ray single crystal structure,the relationship between molecular space structure and the molecular assembly behavior and the number of repeating components in the ring can be clearly observed,and the structural parameters and intermolecular interaction modes of the cyclic polyester and aggregates can be extracted.(2)The degree of polymerization of cyclic polyesters can be effectively distinguished by H NMR,which can help to judge the topological form of these molecules.Due to the different size of the ring and the topological framework,the H signals of the skeleton and nodes have chemical shift in different degrees,which can be used as the basis for inferring the degree of aggregation.(3)From the MS results,in addition to confirming the molecular weight,the ionization results dominated by the addition of cyclic polyester plus Na~+(or K~+)can assist in inferring the inclusion properties of these molecules.The ring structure of the target molecules is easier to wrap foreign small molecules.(4)Density functional theory(DFT)calculation can give rich structural information such as bond parameters and molecular space.In this paper,the B3LYP+6-31G basis set is used to optimize the structure,compare it with the actual structure,and conduct topological structure analysis.Showing the importance of theoretical approaches in the study of cyclopolymer supramolecules.It can be seen that the increase of repeating components in the cyclomer forms rings with different sizes when the molecular chain is closed,forming topological structures from 2-D circular holes to 3-D holes and cages.New nanostructures can be obtained through supramolecular behaviors such as self-folding and self-assembly.This research provides experimental and theoretical basis for the design,synthesis and supramolecular application of cyclomers.This discovery provides a new insight for the construction of new nano materials.