Study On Synthesis And Fluorescent Properties Of Functional Polypeptide Block Copolymer

Synthetic polypeptide material is a kind of polymer material formed by connecting amide bonds in the internal structural units of the molecule.They have a similar chain structure as proteins,and have good biocompatibility and modifiability.The properties of this material can be changed through the regulation of the structure and type of its side chain groups.In this paper,we synthesized different polypeptide block copolymers by the ring opening polymerization?ROP?of NCA,and studied their structures,morphology and responsiveness.The structure and kinds of amino acid side chains of glutamic acid?Glu?and lysine?Lys?were regulated,and the polymerization of NCA was initiated by polyethylene glycol with amino group?PEG-NH₂?as the end group.The block copolymers with photo responsive,temperature sensitive and pH responsive properties were prepared by post modification.Then we studied their properties.1.The results shown that polyethylene glycol-block-polyglutamic acid glycol ester-block-polyglutamic acid o-nitropyrene[PEG-b-P?Glu-g-EG₂?-b-PNBG]could be formed a kind of hydrogel without light,and the hydrogel disintegrates after light exposure.Through the inversion method,the mass fraction of the polymer that can make the system gel is 4%.By heating at 80?for 12 h and adding different metal ions(Na⁺,Ag⁺,Zn²⁺,Ca²⁺,Cu²⁺,Fe³⁺),the secondary structure of the polymer cannot be changed quickly.The secondary structure of the polymer can only be changed by prolonging the placement time.At the same time,we have also obtained the result of the fluorescence intensity of the system after illumination.2.Anthracaldehyde-modified polyethylene glycol-block-polylysine-block-poly?N-octylglycine?[PEG-b-P?Lys-An?-b-PNOG]had obvious aggregation-induced emission?AIE?.The fluorescence intensity increases with the increase of water content in the solution and the extension of light time.In an acidic environment,the anthracene group on the side chain of the polymer molecule falls off.3.Tetraphenylvinylaldehyde-modified polyethylene glycol-block-polylysine PEG-b-P?Lys-TPEMA?had a strong aggregation-induced luminescence effect,as well as reversible pH response.The original appearance in the acidic environment was destroyed,and could be restored after adjusting the environment to alkaline.At the same time,it proves that in order to make the system have such reversible pH responsiveness,the presence of organic solvent is needed.