The Synthesis And Characterization Of Hyperbranched Polypeptide

In this paper, four new hyperbranched AB2 monomers, N-3,5-diamino benzoyl dipeptide methanol ester were prepared. Polypeptides were prepared by direct polycondensations. End-capping reactions of the terminal amino groups were accomplished with 3,5-dinitrobenzoyl chloride. The structures of the intermediate and resulting polymers were confirmed by IR and 1H NMR. The degree of branch (DB) of all the polymers were calculated by 1H NMR, and DB are 0.69,0.68,0.46 and 0.71, respectively. Their glass transition temperatures (Tg) determined by DSC are between 56.9 and 77.4℃, and the polymers'Tg are higher after end-capping reactions because of the introduced rigid group. The thermal stability of Hyperbranched polypeptides were characterized by TGA, the decomposed temperatures(Td) are between 216.4 and 298.3℃, which shows all the polymers have well thermal stability. The inherent viscosities of the Hyperbranched polypeptides are between 0.0986 and 0.6209 dL.g-1, and because of the decrease of the hydrogen bonding, The inherent viscosities of the Hyperbranched polypeptides become lower after end-capping reactions. All the hyperbranched polypeptides have showed good solubility in DMF and other strong polar aprotic solvents solvents, which is the typical character of Hyperbranched polymers. The synthesis and investigation of polypeptides in this paper will bring more information to the investigation of Hyperbranched polymers and polypeptide.