Preparation Of Amphiphilic Block Copolymers And Their Application In The RAFT Emulsion Polymerization Method

Amphiphilic block copolymer, as a kind of functional polymer material, is widely applied in the surface modification, biomedical materials, nano reactors, etc. due to its advantages of surface activity, forming micelle by self-assembling in selective solvent, providing the required reaction sites for emulsion polymerization. As the development of the living/controlled radical polymerization technology, it provides some technical supports to prepare the preparation of a clear structure, molecular weight and narrow molecular weight distribution of controlled block copolymers. RAFT free radical polymerization is a kind of living/controlled radical polymerization technology, which has some advantages, such as mild reaction conditions and preparing block and star structure copolymer etc. In this paper, we prepared the amphiphilic block copolymer by RAFT polymerization technology to investigate its surface performance, and then applied the amphiphilic block copolymer in emulsion polymerization reaction.We synthesized S-1-dodecyl-S’-(a,a’-dimethyl-a"-acetic acid) trithiocarbonate (MTTCD), taking MTTCD as chain transfer reagent, regulating the RAFT polymerization of acrylic acid, characterizing the product structure through the FT-IR,’H-NMR and GPC. We studied the polymerization Kinetics of RAFT to investigate the influence of polymerization temperature, n (AA):n(AIBN) and n(AA):n(MTTCD) on the polymerization reaction. The results stated that polymerization rate reduces in the decreasing reaction temperature, with ratio increases of n(AA):n(AIBN), or with ratio increases of n(AA):n(MTTCD). Polymerization of AA/MTTCD system was quasi-first order reaction. The molecular weight distribution index in1.03-1.13of the obtained products showed that the reaction was well controlled. Then we got a PAA-b-PMA two block copolymer characterized by FT-IR,’H-NMR and GPC structure in the RAFT polymerization of methyl acrylate (MA) which took PAA-MTTCD as macromolecular RAFT reagent. We also studied the MA extender chain polymerization kinetics. And the results showed that the polymerization to MA/PAA-MTTCD system was quasi-first order reaction, and the molecular weight distribution index of the products was in1.10-1.50, which proved that the reaction was well controlled.We studied advantages of foaming, emulsion, and surface activity of the PAA-b-PMA aqueous solution and compared with that of sodium dodecyl benzene sulfonate (SDBS). The results stated that emulsifying properties of the copolymer was better than that of SDBS, but the foaming ability and the ability to reduce the surface tension were inferior to that of SDBS.We applied the PAA-b-PMA made of RAFT polymerization in emulsion polymerization of butyl acrylate (BA), and investigate the affection of factors to the performance of emulsion polymerization process and the emulsion. The results stated that adding acetone was in favor of the block copolymer emulsion. When added n(NaHCO3):n(-COOH)=2:1, KPS dosage was0.7%of the monomer, PAA-b-PMA dosage was3.0%of monomer, the emulsion polymerization could be stable. In addition, we also studied the effects of block copolymer in different length to emulsion polymerization, which showed that the emulsion polymerization effect was relatively better when joining with21AA unit and18MA unit of the structure to the block copolymer B.