Biomimetic Self-Assembly Behavior And Mechanism Of "Isomer" Homopolypeptides Poly (?-Phenylethyl-L-Aspartate) And Poly (?-Benzyl-L-Glutamate)

Synthetic polypeptides,which have the same main chain as proteins,can form the same secondary structure as proteins,and are often used as template materials for conformational transformation and biomimetic research.The repeat units of poly(?-phenylethyl-L-aspartate)homopolypeptide(PPLA)and poly(?-benzyl-L-glutamate)homopolypeptide(PBLG)with similar structure are "isomers" to each other,but their helical conformation stability is different.In this thesis,PPLA and PBLG were synthesized by using N-carboxyanhydride(NCA)ring-opening polymerization(ROP),and the biomimetic self-assembly behavior of the two was explored through the solution self-assembly method,and the assembly mechanism was clarified.On the other hand,the self-assembly behavior of poly(?-benzyl-L-aspartate)homopolypeptide(PBLA)with similar structure and its block copolymer was also preliminarily investigated.The specific research contents are as follows:First,PPLA with different polymerization degrees were synthesized by ROP method.their self-assembly behavior was investigated by solution self-assembly method.It was found that its assembly structure is similar to the viral capsid,and the self-assembly process follows the nucleation-growth mechanism of viral assembly.PPLA first aggregates to form subunits,and then the subunits fuse to each other to form nucleation.After that,the subunits continue to accumulate and grow on the nucleus until the complete capsid-like nanoshell is formed.The process is controllable and the intermediates are easy to capture.In addition,the morphology and phase diagrams of the nanoshell were constructed,which proved that the assembly conditions of the nanoshell were similar to those of the virus.Finally,the molecular compliance of polypeptide plays an important role in subunit fusion by circular dichroism(CD),wideangle X-ray scattering(WAXS)and Fourier Transform Infrared Spectrometer(FTIR)characterization.Since virus research is mainly limited by the difficulty of detecting theoretical intermediates in experiments,the polypeptide self-assembly model is expected to serve as a template for virus research and provide research ideas for programmable biomimetic materials.Second,The ROP method was used to synthesize PBLG with different degrees of polymerization,and the solution self-assembly method similar to the previous chapter was used to study it.It was found that PBLG with low degree of polymerization(DP)can also self-assemble to form a capsid-like nanoshell,and PBLG with high DP is difficult to form this structure due to its strong rigidity.In addition,helix appeared on the surface of the assembly of PBLG with high DP.CD and FTIR showed that the PBLG had a second conformational inversion,which resulted in the occurrence of chiral transfer.Finally,CD further proved that the interchain shrinkage of PBLG with high DP would lead to morphological changes.Finally,PBLA and PBLA-P2 VP block copolymer were prepared via ROP,ATRP and click chemistry,etc.The structure was confirmed by NMR and GPC characterization,and preliminary self-assembly research was carried out.It is found that the type of good solvent has a great influence on the morphology of the PBLA assembly.PBLA-b-P2 VP can self-assemble to form a helix with chiral transfer.