Synthesis And Self-assembly Of Amphiphilic Graft Block Copolymer Molecular Brushes

Polymer molecular brushes with unique molecular structures(such as huge molecular weight,single molecular operation,main-chain rigidity etc.)have a wide ranges of the prospective applications in nanoscience,biomedical and other fields and have become a hot research topic in polymer science.On the other hand,polypeptides not only possess good biocompatibility and biodegradability,but also can form different kinds of the second conformation structures(such as alpha helices,beta sheets,etc.).Polypeptides can assemble into many novel and unique assembled structures(such as vesicle,fiber,disc and super helix structure,etc.)and be widely applied in the fields of biological medicine,biomineralization and genetic engineering.The polypeptide molecular brush can be constructed into a same system by the combination of the advanced properties of polymer brushes and polypeptides,and be helpful to expand the polymer brush research and its application ranges,and can also satisfy some special applications.At the same time,it is also possible to selectively modify the molecular structures of polypeptide brushes and some functional groups are introduced into the polypeptide brushes to expand the fields of application.In the dissertation,a series of polypeptide brushes were synthesized by the combination techniques of RAFT polymerization and ring-opening polymerization,and their chemical structures were fully characterized.Their self-assembly behaviors were studied systematically and the assembly mechanisms were explored.Also,the preliminary study on the gold nanoparticle loading was carried out.The main work includes two parts as following:The contents of the first part are as follows:first of all,poly(glycidyl methacrylate)s(PGMA)with different polymerization degree were prepared by RAFT polymerization,and the polymers with hydroxyl groups,PGMA-OH,were obtained through opening ring reaction,and the polymer brushes PGMA-g-PLA were prepared by using PGMA-OH to initiate D,L-lactide monomer polymerization.Secondly,N-alpha-fluorenylmethoxycarbonyl-N-epsilon-Boc-L-lysine(Fmoc-Lys(Boc)-OH)was introduced into the terminal group through the side chain modification method and the polymer brushes with side terminal amino(-NH2)can be obtained by removal of the protective groups t-butyloxycarbonyl(Boc).Finally,polypeptide molecular brushes PGMA-g-(PLA-b-PLys(Cbz/Fmoc)were prepared through a-amino acid carboxyl-N-anhydride(NCA)ring opening polymerization of monomers NCA-Lys(Cbz)and NCA-Lys(Fmoc)and their chemical structures were characterized in detail by the combination technologies of NMR,IR and GPC.By solution self-assembly method,the self-assembly behaviors of the polypeptide molecular brushes were studied,and the effects of external factors(solvent,concentration,moisture etc.)on the self-assembly morphology were explored and different assembled structures including leaf-shaped structure,porous micelles can be obtained.In order to further expand its application,polypeptide brush/gold nanoparticle hybrid materials were prepared through loading polymers to the surface of gold nanoparticles using in-situ method and the principles of changeable morphologies in different solvents were more discussed,which will provide a reference for the practical application of this kind of materials.The contents of the second part are as follows:firstly,polymer brushes PGMA-g-PLA containing PLA side chains were synthesized by a similar synthetic route to the above.Secondly,2-methyl-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid was introduced onto the side chain end group of PGMA-g-PLA by the esterification reaction and the macromolecular chain transfer agents PGMA-g-PLA-CTPA were obtained.Finally,polymer brush PGMA-g-(PLA-b-PEGMA)with poly(glycidyl methacrylate)(PGMA)as the main chain and poly(lactide)and poly(Poly(ethylene glycol)methyl ether methacrylate)as block copolymer side chains was prepared through RAFT polymerization using 2,2'-azobisisobutyronitrile(AIBN)as the initiator to initiate the monomer Poly(ethylene glycol)methyl ether methacrylate(EGMA)(Mn=293 g/mol)polymerization and their chemical structures were fully characterized.The poly(polyethylene glycol methacrylate)possesses temperature sensitivity,and the effects of different temperatures(10?,20? and 30?)on the assembled shape structures were explored in more detail,and different aggregates including nanorods,nanofibers and porous vesicles and other assembly structure were obtained.