Metathesis Synthesis,Self-assembly And Photoresponsive Property Of Homopolymer With A Confined Azobenzene Pendant

Polymer self-assembly is an important research field in polymer science,and the exploration and understanding of its basic laws is expected to have an impact on the development of many disciplines.Compared with the more complex but widely studied self-assembly of block copolymers,the use of homopolymers with simpler synthetic methods as self-assembly building blocks is less but more meaningful.This dissertation reveals the main chain structure and side chain ionic bonds of metathesis homopolymers by conducting basic research on the metathesis polymerization methodology of(ionized)azo olefin monomers and the construction of azo metathesis homopolymer self-assembly systems.The role and contribution of the effect on limiting the photo-induced cis-trans isomerization transformation of the azobenzene side group and improving the self-assembly ability of the homopolymer,and obtaining information about the structure and composition of the metathesized homopolymer,the photoisomerization of the azobenzene group is affected.Information on the correlation between the degree of confinement and the self-assembly behavior and assembly morphology of homopolymers.First,azobenzene groups were introduced onto norbornenimide monomers andα,ω-diene monomers,respectively,via ring-opening metathesis polymerization(ROMP)and acyclic diene metathesis(ADMET)Polymerization to obtain a series of homopolymers with different numbers of methylene groups attached to the azobenzene pendant groups,which undergo traditional trans→cis photoisomerization and cis→trans photoisomerization under UV and visible light irradiation.The recovery process has high efficiency and fast transformation rate,indicating that the photoisomerization process of the pendant azobenzene is not bound.The resultingπ-πinteractions are not sufficient to drive the self-assembly of this homopolymer,including ADMET polymers with well-defined backbone structures and precisely positioned branches.On this basis,pyridine ion groups were attached to the pendant groups of azo homopolymers,and the ionized olefin monomers and polymers were characterized by hydrogen nuclear magnetic resonance(~1H NMR)to confirm the accuracy of the structures;Gel permeation chromatography(GPC)tests also showed that the homopolymer had a controlled molecular weight and a relatively narrow molecular weight distribution;UV-Vis absorption spectroscopy(UV-Vis)confirmed the photoinduced trans-translation of the pendant azobenzene of the homopolymer→The cis-isomerization process is obviously bound,increasing the content of the trans-configuration in the photosteady state;DLS and TEM characterization results also show that the homopolymers can self-assemble into nanoaggregates.According to the difference in the main chain structure,the ionized ROMP homopolymer self-assembles to form spherical nanomicelles with extremely uniform size,and the size of the micelle can be regulated by changing the number of methylene spacers;the ionized ADMET homopolymer self-assembles Forming ring structures of uniform size,these ring nanostructures can be fused to form larger,stable ring assemblies with increasing homopolymer concentration;It can effectively weaken the electrostatic effect on the photoinduced trans→cis isomerization of azobenzene.The homopolymer self-assembles to form unstable spherical micelles,which gradually transform under UV light irradiation.aggregates in a fusiform structure.It shows that the electrostatic effect generated by the ionic bond of the side chain restricts the photoisomerization transformation of the side group azobenzene of the polymer under ultraviolet light irradiation,and the photosteady state maintains more trans configuration;on the other hand,it cooperates with the trans structure.The strongπ-πinteraction drives the self-assembly of homopolymers to form stable nanoaggregates.It can be seen that the control of the microstructure of the polymer chain by the metathesis polymerization method is the premise of ensuring the self-assembly of the homopolymer,and the enhancement of the non-covalent bond force and the high degree of synergy of the homopolymer itself are the key factors.