Synthesis And Characterization Of Novel Block Copolypeptides And Their Properties

Polypeptides with good biocompatibility and biodegradability can be synthesized from one single or several kinds of amino acid or their derivatives. Due to strong hydrogen bonding, some secondary structures such as alpha helix and beta folding can be formed in polypeptides. Owing to the alpha helix or beta folding, polymers based on polypeptides can assemble into more ordered aggregates, which have great application prospect in the field of tissue function materials. In order to expand the application range of the polypeptide compounds, a series of novel functional block copolypeptides with OEG dendrimers or azobenzene groups were synthesized by a combination technology of "Click chemistry" and ring-opening polymerization reaction. The structures and properties were characterized and studied.Firstly, a series of novel copolypeptides (mPEG-b-PELG-g-Gn (n=1,2)) were designed and synthesized. The copolypeptides mPEG-b-PCELG were synthesized by ROP reaction, using mPEG-NH2 as an initiator. Then, the OEG dendrimers Me-Gl-Propargyl or Me-G2-Propargyl with excellent performances of solubility and biocompatibility were grafted to the polypeptides by azido reaction and "Click chemistry" reaction. The chemical structures of copolypeptides were characterized by Magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and infrared spectra (IR). Variable temperature UV-Vis spectra were used to study thermoresponsive behaviors of the polymers in water. On the other hand, host-guest complex hydrogels with different microstructures were prepared from block copolypeptides with alpha CD. The performances and formation mechanism of the hydrogels were researched by transmission electron microscopy (TEM), scanning electron microscope (SEM), advanced rotational rheometer and X-ray diffraction (XRD).In the second part, the copolypeptides (mPEG-b-PELG-g-MOAPB6) containing azobenzene side groups were synthesized by "Click chemistry" reaction and ring-opening polymerization reaction, and self-assembly and photoresponsive properties were explored. Different self-assembled morphologies can be obtained via changing the water content in the polymer solution, and photoresponsive properties of the aggregates were studied. The results obtained from TEM and SEM showed that morphologies of the aggregates were varied from the solid sphere to spherical vesicles, and then to irregular vesicle with the water increase of water. At the same time, the photoisomerization of micelles was studied by ultraviolet-visible spectra. The spherical vesicles were used to encapsulate two kinds of fluorescent materials, and the optically controlled release was studied in UV irradiation by fluorescence spectra and fluorescence microscope.