Synthesis Of Copolypeptides And Their Controlled Self-assemblies

Various nanostructures including spherical micelles, vesicles, cylinders and toroids from amphiphilic block copolyers through self-assembly have attracted more and more attention over the past few decades. These assembled nanostructures are not only of academic interest but also possess potential applications in many fields, such as microelectronics, catalysts, photoelectric materials, etc. among the amphiphilic block copolymer self-assemblies, polypeptide-based self-assembly have two characteristics. Firstly, polypeptide segments can adopt various conformations including α-helix and β-sheet, which have a significant influence on the self-assembly behavior of copolypeptides in solution. Secondly, polypeptides have excellent biocompatibility and degradability in comparison with other common polymers. Therefore, polypeptidebased self-assemblies can be applied into bio-related fields, such as tissue engineering, drug and gene delivery, and mimicking bio mineralization, etc. Here, a series of polypeptides such as homopolymers, amphiphilic copolymers and polymer-brush were synthesized, and their self-assembly behavior were researched, the properties of the nanoparticle-coating polypeptide were explored. The main contents are as follows:(1) PBLG and PEG-b-PBLG block copolymers were synthesized by the ring-opening polymerization (ROP). Their self-assembly behavior and the formation mechanism were explored in details, various aggregate structures including micelles, disk-like micelles, vesicles can be achieved and polypeptides are used as a template to mimick biomineralization(2) Two different polypeptide segments to form a zwitterionic diblock copolymer poly(L-lysine)-b-poly(L-glutamic acid) (PLL-b-PLGA) were synthesized by sequential ring-opening polymerization of the corresponding R-amino acid N-carboxyanhydrides.Their self-assembly behavior and the formation mechanism were explored in various PH, various aggregate structures including rod-like micelles, vesicles bonded to each other and flake-like micelles can be achieved. And the polymer possessing amine (-NH2) and carboxyl (-COOH) to stabilize gold nanoparticles by the approach of two-step ligand-exchange, in-situ and UV reduction of HAuCl4.(3) A combination of ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization were used to prepare polypeptide brushes (Ply(Cbz)-b-(Ply-g-PEGMA)). Their self-assembly behavior and the formation mechanism were explored in various temperature, various aggregate structures including flake-like micelles, long rod-like micelles and vesicles can be achieved. And the polymer possessing trithiocarbonate to stabilize gold nanoparticles by the approach of two-step ligand-exchange.