Study On Synthesis Of Amphiphilic Copolymer And Its Self-assembling Behavior

The amphiphilic copolymer can self-assemble to form aggregates or micelles with core/corona structure. The aggregates have wide applications in many scientific and technical fields, such as biological simulation (vesicle), drugs-delivery system, synthesis of functional nanoparticles, extraction of oil and so on. The well-defined polymers with controlled molecular weights and narrow Macromolecules Weight Distribution (MWD) can be synthesized by Atom transfer radical polymerization(ATRP) in convenient codition, due to its versatility of monomers, simplicity in practice and its versatility of polymerization mode.In this paper, the polymer of MPEG-Br which end-group is bromide atom was synthesized by esterrification reaction with 2-bromo-2-methyl-propanoyl bromid and methoxypolyethyle-ne glycols. And then, the amphiphilic copolymer of MPEG-b-PSt with a low polydispersity and the length of PSt block is controlled was synthesized by ATRP with using MPEG-Br as initiator, cuprous bromide as catalyst and N, n,n',n',n-Pentamethyl diethylenetriamine(PMDE-TA)as ligand. The polymer was characterized by FTIR and GPC that the reaction fitted ATRP.The micelle aqueous solution of MPEG-b-PSt was prepared by using single-solvent dissolving method or dialyzing method. The critical micellar concentration(cmc) was investigated by conductivity. And the influence of concentration of MPEG-b-PSt, chain structure and temperature on the micellization behavior were investigated.At the same time, the morphoiogyies of micelles and interfacial tension were investigated by AFM observation mean and Automatic Spinning Drop Interface tentiometer. The experiment results showed that the self-assembling behavior of MPEG-b-PSt depends apparently on the microstructure of the macromolecules and the temperature. Under the same length of hydrophilic block MPEG, the copolymer with longer hydrophobic block PSt had lower critical micelle concentration, and at higher temperature, the copolymer had lower critical micelle concentration. The micelles had the morphology of akin to sphere with diameter ranging from 50 to 100nm and the small micelles would be join to form much more big spindle aggregates with the increase of the concentration of MPEG-b-PSt. The micelle aqueous solution of MPEG-b-PSt was able to decrease interfacial tension to some extent.