Synthesis, Characterization And Property Of Azobenzene-based Copolypeptide

Polypeptide is a newly kind of biodegradable material since it has been concerned and studied widely from1970s. Similar to natural proteins, the architecture and composition of the polypeptides are synthesized from single or several kinds of amino acid or their derivatives connected with each other by amino bond. Because of its intra and inter molecular hydrogen bonding, polypeptides often present an a-helix or β-sheet secondary structure. The special composition as well as its unique structure endows these peptides with excellent properties. On one side, polypeptide could be a kind of substitution of natural protein to participate in the development of biological multifunctional materials, since they have good biodegradable and biocompatibility. On the other side, the rigid secondary structure of polypeptides significantly promotes the formation of more unique ordered structure. On the basis of its various aspects, these polypeptides have trenendous prospect in the area of functional materials and biomedicine.Azobenzene-Containing copolymers are photoresponsive because of the reversible trans-cis and cis-trans isomerizations of azobenzene chromophores caused by UV light or visble light irradiation, which triggers significant changes in the physicochemical properties of polymer materials. Thus, these materials are widely used due to their potential in various optical and optoelectronic applications such as grating diffraction, optical sensors, optical waveguide, optical information storage and so on.In this paper, a novel azobenzene-functionalized copolypeptide(MPEG-b-PELG-g-(M0APB6)nP, n=1,2,3) combined the rigid rod of a-helix or β-sheet in the peptide and the photoresponse of azobenzenes group were designed and synthesized via ring-opening polymerization (ROP) and Huisgen’s1,3dipolar cycloaddition (click chemistry). Their chemical structures were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1HNMR)、gel permeation chromatography analysis (GPC). The thermomechanical behavior of block copolymers were studied by exploiting differential scanning calorimetry (DSC). Result shows that block copolymers have no liquid crystalline, and the thermomechanical behavior is different from the azobenzene-containing side-chain liquid crystalline polymers. Furthermore, the photo-induced isomerization behavior of block copolymers in solution was investigated by UV-vis spectrometry to discuss the relationship between the secondary structures of peptide and the photosensitization of azobenzene chromophores. Also the slef-assembly of amphiphilic copolypeptide on a glass wafer vis Breath Figure has been discussed by means of scanning electron microscope (SEM) and atomic force microscopy (AFM). Research shows that the photoinduced motions of azobenzene chromophores caused by linear polarized light irradiation led to the shape deformation of the nano-aggregates and the honeycomb structure. Copolypeptide with rigid segments as skeleton, is expected to have great potential for application in the field of functional membrane polymer materials, biomedical materials, functional nanomaterials etc..