Synthesis And Characterization Of Spidroin Like Polymers

In this work, on the secondary structure level, a series of well-defined structure polymers, which had the similar secondary structure with spider silk proteins, were synthesized by the condensed polymerization of the functional oligopeptides and synthesized oligomers. These silk like polymers could be used as the materials for understanding the effect of chain folding models of fibroin and their three-dimensional order which be formed in the spinning process on the mechanical properties of silk fibers.Firstly, the functional oligopeptide monomers (M), containing the amino sequence [(Ala)₅] which derived from the crystal region of spider dragline silk, were synthesized with the traditional liquid-phase peptide synthesis method. Then the multiblock copolymers (PS-PEP2000, PEG-PEP 1000,PI-PEP2210 and PI-PEP5000) were obtained from the polymerization of the functional oligopeptides and oligomers (PS2000,PEG1000,PI2210 and PI5000)with the base as catalyst. These simulated polymers were the alternating copolymers formed by oligopeptide segment and oligomers segment instead of the pure protein.The silk like copolymers showed a poor solubility in common solvents, however, they could dissolve in the mixture of chloroform and chloroethanol, therefore, the intrinsic viscosity were detected in the mixture of chloroform and chloroethanol at 25 ℃, and the results showed that the molecular weight of these copolymers were higher(estimated to be 10⁴～10⁵). In addition, the glass transition of polymer PI-PEP2210 and PI-PEP5000 had enhanced apparently compared to the oligomers(PI2210,PI5000, respectively). Because of the thermal instability of the ureabond in molecular chain, all synthetic polymers began to degrade around 210-270℃, and had no melting point. The differences of thermal properties between the simulated polymers and animal silk protein were attributed to their different primary structures.The FT-IR, Raman, CP/MAS Solid-state ¹³C-NMR and Wide Angle X-ray Diffraction measurements on these silk like copolymers revealed that a major β-sheet conformation as well as other conformations coexisted in the polymers. The molecular chain of PS-PEP2000, PEG-PEP 1000, PIPEP2210 and PI-PEP5000 in (3-sheet conformation spontaneously aggregated into some ordered regions, and then fonned the crystals which be similar to that in natural silk which means the silk like copolymers had the similar solid-state structures with animal silk proteins. These results meant our design for the simulated synthesis of the silk-protein like polymers on the secondary structure level was feasible and successful.In addition, TEM and AFM were used to study the self-assembly behavior of the silk like material in the solid state, and results showed that the peptides of the copolymer could self-assembled to crystalline regions in this condition. The self-assembly behavior of the copolymers in solution also had been studied, the DLS and TEM results indicated that the copolymer micelle formed in the mixture of chloroform and chloroethanol(V/V=2/1).