| World is boundless, colorful and full of variety of life forms, and polypeptide is the basis of all life phenomena. In recent years, the synthetic polymer materials are connected to the polypeptides by chemical bonds to form polypeptide hybrid block polymers (polypeptide molecular chimeras), and polypeptide hybrid block polymers have drawn much attention, which due to their complex self-assembly and phase behaviors making available a variety of nonclassical morphologies and hierarchical superstructures in bulk and in solution. The exploration of these structures has a very important meaning of life.Poly(y-benzyl L-glutamate)(PBLG) is a unique polypeptide material, and it has the characteristics of stable a-helix secondary structure and chirality. The hydrogen bonds based on C=O and-NH make the PBLG chains to form a-helix structure, a rigid rod-like structure. Polystyrene (PS) is a common polymer material, which presents a flexible coil structure. We used N-carboxylic acid anhydrides (NCA) living polymerization to synthesize a rigid-flexible diblock copolymer polystyrene-b-poly (y-benzyl L-glutamate)(PS-b-PBLG),and their thermal properties and liquid crystal properties were investigated. Due to the wide difference between the two block components, the microphase separation behaviors can be observed, and PS-b-PBLG can form periodically ordered structures. This thesis focused on the phase separation structures of PS-b-PBLG, and PS92-b-PBLG81and PS271-B-PBLG724were the samples to study their phase separation structures in different solvent, and we found polypeptide chains folded in various degree. Moreover, we found the folding of the polypeptide chains resulted in the changes of self-assembly morphologies. The main content of this thesis listed as below:Synthesis and characterization of PS-b-PBLG:The second chapter details the N-carboxylic acid anhydride method (NCA) to synthesize a series of PS-b-PBLG samples, using the primary amino-ended polystyrene (PS-NH2) as the macroinitiator to initiate the benzyl ester of glutamic acid-NCA (BLG-NCA) polymerization. The composition, molecular weight and molecular weight distribution of PS-b-PBLG were characterized by’H nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC), and their thermal properties were investigated by differential scanning calorimetry (DSC); also, its liquid crystal properties were investigated by the polarized optical microscopy (POM), we found that the sample PS241-b-PBLG724showed a spherulitic texture not the smectic texture stripes or knit-like texture as report.Phase-separated structures of PS92-b-PBLG81film:The third chapter details the wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) on the sample PS92-b-PBLG81films casting form1,1,2,2-Teteahydrofuran (TCE), N, N-dimethyl formamide(DMF),1,2-dichloroethane (EDC), anisole, and1,4-dioxane (DIO). We found PS92-b-PBLG81formed a periodic layered structure in the shear-oriented solid films, a-helical segments arranged in hexagonal packing, the folding of a-helix occured in EDC,and the periodic length of layer structure changed. However, a-helix chains did not fold in TCE.Self-assembled structure of PS271-b-PBLG724film and the solvent effects: The fourth chapter details the research by transmission electron microscopy (TEM) and atomic force microscopy (AFM) on PS271-b-PBLG724(ΦPBLG=0.83) films casting from TCE and EDC. The TEM results showed the PS271-b-PBLG724formed alternating zigzag in the thin film casting from TCE, and the morphology appeared stripes morphology due to the folding of a-helix chain in EDC. Furthermore, through the measure of AFM,it is still difficult to examine the lamellar phase separation structures or the corresponding periodic length seen in the TEM. This shows that there may be other special morphologies on the surface of the films. This AFM results also provided a part of the relevant information.In this thesis, we synthesized a rod-coil block hybrid polypeptide: polystyrene-b-poly (y-benzyl L-glutmate)(PS-b-PBLG), and we investigated their self-assembled structures in different films casting from different solvents. Due to the wide difference between the two block components, PBLG chain is rigid like rod, and the PS chain is flexible like coil, so the microphase separation behaviors can be observed, and PS-b-PBLG forms periodically ordered structures in TCE and EDC. We found the polypeptide chain’s rigidity is affected by the casting solvents and the folding of a-helix results in the changes of their self-assembly morphology. In addition, the ordered phase separation morphologies can not be observed in the films casting from DIO and anisole. We guessed the solvents may have priority for the two block components. |
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