Synthesis And Properties Of Amphiphilic Graft Copolymer SPS-g-PEG

Amphiphilic graft copolymer has unique solution properties, self-assembly characteristics, surfactants characteristics and so on. The synthesis and study of amphiphilic graft copolymer material show an important significance. In this dissertation, a new amphiphilic graft copolymer was synthesized by syndiotactic polystyrene (sPS) as a hydrophobic material and polyethylene glycol (PEG) as a hydrophilic material, its molecular structure, micellization behavior, hydrophilicity and staining properties were studied. The main contents are as follows:Heterogeneous Friedel-Crafts acylation of highly stereoregular syndiotactic polystyrene (sPS) was used to synthesize bromoacetylated sPS (BMPsPS) as a main chain first and then synthesizing amphiphilic graft copolymer of sPS-g-PEG by the Williamson etherification through grafting PEG. FTIR,1H-NMR results indicated that the acetylation reaction can be well controlled and carried out to get a high acetylation degree up to43.48%; The functional sPS was achieved by Williamson etherification which was successfully synthesized by grafting onto three different molecular weights of PEG; The DSC analysis showed that the thermal performance of BMPsPS changed, such as the Tg and Tc increased compared to sPS, the crystallization behavior of sPS-g-PEG was further improved.Self-assembly of amphiphilic graft copolymer of sPS-g-PEG in selective solvents was studied in detail. Based on the intrinsic fluorescence characteristics of syndiotactic polystyrene, the CMC values of sPS-g-PEG600, sPS-g-PEG1000and sPS-g-PEG2000in aqueous medium were determined to be0.155mg/L,0.199mg/L and0.20mg/L by fluorescence spectroscopy respectively, which were much lower than the CMC value of small molecule surfactants and suggested that sPS-g-PEG self-assembled micelles were very stable, and the CMC values increased with the increase of the molecular weight of PEG This was due to the increase of the hydrophilic segment and the decrease corresponding of the hydrophobic segments will diminish their mutual aggregation, leading the polymer to form micelles in higher concentrations. The particle size and morphology of sPS-g-PEG600micelles in aqueous solution at different annealing temperature (25℃-130℃) were studied by SEM, the micelles aggregated spherical micelles at low temperature, while aggregated square micelles at high temperature, and the particle size was increased with temperature rise and remained unchanged until high temperature. The influence of the hydrophilic graft chain length on the micelle particle size was investigated further. SEM studies showed that the size of the micelles formed from sPS-g-PEG (Mn of PEG is600,1000and2000, respectively) increased with the increase of molecular weights of PEG in side chain and the aggregates of square micelles, in the case of the same polymer concentration and annealing temperature conditions, but the size of the micelles increased little. Because that sPS formed the core and PEG formed the shell of the micelle in the selective solvent to PEG, so the size of the micelles increased little with the increase of molecular weights of PEG. Changing of the temperature of solvent evaporation, annealing time and the mice liar concentration, sPS-g-PEG was found to self-assemble into polymer micelles with co-exist of micelles and micellar aggregates, and then form rod-like, dendritic, wheat-like, tree form aggregates. The AFM studies also showed that the micelle solution of sPS-g-PEG was two-phase with the obvious "core-shell" structure and the aggregates of square micelles with low polydispersity.The application of amphiphilic graft copolymer of sPS-g-PEG as macromolecular surface modifier was studied and the hydrophilicity of the copolymer was measured by the surface contact angle method. sPS-g-PEG as macro molecular surface modifier was added in the syndiotactic polystyrene molding, the contact angle of sPS/sPS-g-PEG decreased with the increase of the surface energy of the contact surface; the concentration and enrichment of polyether chain in the surface layer increased constantly with the increase of molecular weight of PEG and graft degree of PEG in the macromolecular surface modifier of sPS-g-PEG, so the contact angle of sPS/sPS-g-PEG decreased, the surface energy and the hydrophilicity increased. The influence of dye adsorption time and adsorption temperature on dyeing properties of sPS-g-PEG was studied preliminary by the experiment of adsorption of rhodamine6G. Under the dye adsorption temperature of60℃, the dye adsorption capacity of Rhodamine6G in sPS-g-PEG increased rapidly with the extension of the dyeing time during the primary stage of staining, after which it growed slow down with continued increase of dyeing time, the adsorption of rhodamine6G in sPS-g-PEG600, sPS-g-PEG1000, sPS-g-PEG2000reached equilibrium when the staining time reached6h,4h,3h, respectively. And the dye adsorption capacity also increased significantly with the increase of molecular weight of PEG. In addition, the dye adsorption capacity increased with the increase of dyeing temperature. Take sPS-g-PEG2000for example, the dye adsorption capacity had been unchanged basically when the temperature reaches60℃, which indicate the dye adsorption reach equilibrium.