| The surface activity of amphiphilic polymer in solution depends on its morphology, which is closely related to its architecture, chemical composition, molecular weight and other factors. According to the need, people can synthesize many amphiphilic polymers with different molecular weight, different activity groups and different architectures, by choosing different monomers, initial reaction conditions, and so on. Recently, the synthesis of amphiphilic polymers with high surface activity and high molecular weight is still the emphases of the research all over the world, which can be gained through the designing different composition of hydrophilic groups and hydrophobic groups.Comb-shaped polymer is a special kind of graft polymers, having great research and application value. The comb-shaped polymer with polyoxyethylene chain can be widely used in many fields, such as adhesive, anti-protein biological surface, chromatography equipment, lubrication agent, surfactant and polymer compatibilization agent. So far, there are three kinds of method to synthesize comb-shaped polymers:"grafting onto","grafting from","grafting through". One of the advantages of the"grafting through"is that the length of the main chain and the side chain can be controlled, and the polymer has narrow molecular weight distribution, if the comb-shaped polymers are synthesized by a"controlled"/living polymerization approach combined with graft through.Because of its broad application of monomers, mild reaction condition, easy to operate, and other advantages, ATRP has attracted considerable attention among many"controlled"/living radical polymerization methods.In this paper, monomethoxy-capped oligo(ethylene glycol) methacrylate OEGMA (Mn = 300,475) and Poly(ethylene glycol)methyl ether methacrylate (PEGMA) (Mn = 1100), were chosen as polymerization monomers. The comb-shaped polymers with polyoxyethylene chain were synthesized by ATRP, with narrow molecular weight distribution and clear structure. And their molecular weight of main chain and side-chain can be controlled.Firstly, OEGMA was used as the reaction monomer. As it is liquid at room temperature, the comb-shaped polymer POEGMA was synthesized by ATRP solution polymerization and ATRP bulk polymerization. When water was used as the solvent in the solution polymerization reaction, the reaction system was homogeneous and reacted quickly. Once the initiator was added, the reaction started immediately. Then the system became more and more viscous and it became difficult to stir. When the reaction time got to two hours, the conversion of the reaction had reached more than 85﹪.However, with the rapid increase of the viscosity, there might appear gel phenomenon occasionally, which might impacted the experimental result. The comb-shaped polymers POEGMA synthesized by these two methods both had very narrow molecular weight distribution, and these two polymerizations both had"controlled"/living features. But compared with the solution polymerization system, the reaction speed was slow and the conversion was smaller. Then PEGMA was used as the reaction monomer, and synthesized P (PEGMA) by ATRP solution polymerization method. The impact of the ratio of CuBr / bpy on the process was also studied here. It is found that under the same condition, both reactions had "controlled" / living features, whether the ratio of CuBr / bpy in the system was1:1 or 1:3. But compared with the reaction with the ratio of 1:1, the product in the reaction with the ratio of 1:3 had larger number average molecular weight. It is thought that is related to the effect of the dosage of the ligand in ATRP non-homogeneous system. In the non-homogeneous system, as the dosage of the ligand increased, the solubility of the CuBr in the toluene increased. So that can quicken the speed of the exchanging between the activity growth link and the dormancy, improve the polymerization rate and larger the number average molecular weight of the product.Secondly, P(PEGMA) was synthesized by the reverse ATRP solution polymerization method, and the impact of the solvent on the process was inspected. It was found that under the same conditions, when the mixture of water and THF(v/v= 1:1) was used as the solvent, the reaction system was homogeneous, but it became non-homogeneous when toluene was used as the solvent. Both of these two reactions had"controlled"/ living features, but the product of the toluene system had larger molecular weight and narrower molecular weight distribution. In our opinion, it may be due to the polar of the mixed solvents, which may cause some side reaction, such as the removal of HX.Finally, the amphiphilic comb-shaped polymer P(PEGMA)-b-PSt was synthesized by two consecutive ATRP solution polymerizations. The molecular weight of its main chain and side-chain were controlled and the molecular weight distribution was very narrow. The polymerization also had good"controlled"/living features. The self-assembly behavior of the P(PEGMA)-b-PSt in the aqueous solution was also studied, and its morphology was observed through the TEM. It was found that it can be self-assembled into uniform nano-sized spherical micella particles in the aqueous solution, which has a core of PSt and a shell of PEG ,and the size was about 60-100 nm. |
