Synthesis And Characterization Of Polypeptide/Polypeptoid Block Copolymers

Polypeptides and polypeptoids material have good biocompatibility and biodegradability.Their block or random copolymers combine the advantages of both and have potential applications in the field of biomedicine.Herein,block copolymers based on polypeptides and polypeptoids material were prepared by NCA ring-opening polymerization,and their secondary structures,solution properties and responsiveness were studied.The effects of temperature and pH on the properities of the copolypeptides solution were investigated.The dissertation includes the following sections:1.Two-domensional supramolecular assemblies from p H-responsive poly?ethyl glycol?-b-poly?_L-glutamic acid?-b-poly?N-octylglycine?triblock copolymers:polyethylene glycol amine?PEG-NH₂,Mn=2000?was used as macroinitiator,and BLG-NCA and Oct-NNCA were used as monomers to synthesize triblock copolymers with p H-responsivity and amphiphilicity through sequential ring-opening polymerization?ROP?.The triblock copolymer can directly dissolve in water.They can self-assemble into nanodisc and nanosheet-like morphology in aqueous solution.Reversible transformation was observed.Studies have shown that the dominant driving force of the self-assembly in aqueous solution is the hydrophobicity of PNOG instead of crystallinity;the morphology of the assembly changes from nanodiscs to nanosheets not noly depend on the pH of the solution,but also the ratio of PGA/PNOG blocks.Regarding,the molecular weight has no significant effect on this transition.2.Synthesis and characterization of thermo-responsive block copolymers based on polypeptide/polypeptoid:We used hexylamine as an initiator and?-propargyl-_L-glutamic acid N-carboxyl anhydride?PLG-NCA?and(N-octyl glycine anhydride?Oct-NNCA?was used as monomers to synthesize thermo-responsive block copolymers??PPLG-g-EG₃?-b-PNOG?by gradual ring-opening polymerization.¹H NMR confirmed the chemical structure of the polymers.GPC results showed that the molecular weight distribution of the polymer was narrow.The CD results showed that the polymer adopts?-helix conformation at room temperature and the?-helix content were decreases as the temperature rises.The TEM results show that the self-assembly morphology of the polymer in aqueous solution is affected not only by temperature but also by the ratio of blocks.