Synthesis And Properties Of Polypeptide Based Copolymers

As one of the basic components of protein and life, peptide has attracted muchattention in recent years. In this thesis we focused on the synthesis of a series ofglutamate polypeptides based copolymers, as well as the properties of polypeptidessynthesized and the effect of secondary structure of polypeptide on the properties ofcopolymers. We described here the relation between secondary structures ofpolypeptides and 2-Dimensional and 3-Dimensional self-assembly properties ofcopolymers. The self-assembly character of polyglutamate based copolymers wassystematically studied by direct visualization methods such as AFM, TEM, and SEM.Model analysis was proposed on any self-assembly phenomena observed, and therelation between properties and copolymers was clearly expressed. The main contentof this thesis is listed as below:Synthesis polypeptide based eopolymers. A series of poly(γ-stearyl L-glutamate)(PSLG) based copolymers was synthesized by ring-open polymerization of aminoacid NCA, which was initiated by hydrophilic polymer such as amine terminated PEG.Some specific properties would be found derived from these novel molecularstructures of PSLG-b-PEG copolymers. The amine terminated PEG was synthesizedfrom hydroxyl PEG by tosylation and the classic phthalimide-hydrazine procedure.We studied the micellization of PSLG-b-PEG contained copolymers by in-situsynthesis method also.Self-assembly of PEG-b-PSLG eopolymers in solvents. The self-assembly ofamphiphilic copolymers is one of the attractive topic of macromolecular physics. Aseries of studies on the synthesis and property of amphiphilic copolymers were carriedout these years, and great works have been done by Eisenberg's group on this area. Ithas been extensively investigated about 2D self-assembly on the surface of solventand 3D self-aggregate in solutions of PEG-b-PBLG these years. We focused ourinvestigation on the 3D self-aggregation of PEG-b-PSLG di-and triblock copolymersby TEM, SEM, and DLS etc. Vesicular like aggregates of PEG-b-PSLG were found in organic mixed solvents, and the self-assembly mechanism of PEG-b-PSLG wassystematically analyzed along with a designed model.Epitaxial array of PEG-b-PSLG eopolymers on HOPG. Watanabe andcoworkers investigated the 2D self-assembly of poly(γ-L-glutamates) with longn-alkyl side chains on graphite, and demonstrated their epitaxial array phenomena byAFM. PEG-b-PSLG di- and triblock copolymers exhibited the epitaxial array onHOPG guided by the interaction of PSLG and HOPG too, with PEG aggregatedsurround or above the parallel aligned PSLG. There is no distinct difference between2D array with variance of sample concentrations, while the 2D aggregates shapes onthe HOPG surface changing from submonolayer island into monolayer with theincreasing of sample concentration. There should be nanorods or ring-shapedaggregates on the monolayer of copolymer with even higher solution concentration.Sample preparing methods, such as castingor spin coating, carried out no diverse on2D array of copolymers on HOPG. A model of PEG-b-PSLG epitaxial array onHOPG was designed on the bases of our experiments.Investigation of copolypeptide organogel. A Novel copolypeptide(poly(γ-stearyl L-glutamate)-b- poly(γ,-benzyl L-glutamate)) (PSLG-b-PBLG) has beensynthesized, and it could 1D self-assemble into thermal reversible organogel intoluene. There is some visual diverse of those gels, for example, both the gels ofPBLG/toluene and PSLG/dodecane were opacity, while the PSLG-b-PBLG/tolueneexhibited transparency. PSLG-b-PBLG/toluene gel demonstrated fibrilla structureunder investigation of AFM, TEM, and SAXS. Nanoribbon structure was found withdrop-casting PSLG-b-PBLG/toluene (0.2 wt %) solution on mica by AFM observation.Nanoribbon-like model of PSLG-b-PBLG/toluene gel was proposed by all of theresults ofAFM, TEM, and SAXS.