Synthesis Of Water-Soluble RAFT Agents And Their Use In Controlled Polymerization Of Aqueous Monomers

Controlled/“living”free radical Polymerization is one of the most important research area in Polymer chemistry and polymer preparation, to both academic and Practical researchers in recent years. Reversible Addition Fragmentation chain Transfer (RAFT) radical polymerization has got much attention since its discovery. Due to its many merits such as diversity of monomers, mild condication and diversity of polymerization mothed, together with its guarantee to great efficiency of polymerization, RAFT polymerization has been the focus of“living”/controlled polymerization. But so far, the synthesis of water-soluble chain transfer agent(CTA) and the RAFT polymerization of water-soluble monomers initiated with ultraviolet radiation in aqueous solution at ambient temperature are few reports. In this research, two water soluble RAFT agents, namely 2-(4-cyano-4-(diethylcarbonothioylthio) penta- noyloxy)-N-ethyl- N,N-dimethy lethanaminium bromide(CDPEDB),2-(4-cyano-4- (dodecylthio carbonothioylthio) pentanoyloxy)-N-ethyl- N,N- dimethyl-ethananminium bromide(TTC), were synthesized and applied to the water and ultraviolet radiation initiated RAFT polymerization of water-soluble monomers. At the same time, the effects of monomer concentration, polymeric time, ratio of monomer and chain transfer agent on PDI were observed.The result showed that CDPEDB can be used as a good CTA to controll the polymerization initiated with ultraviolet radiation in water of DMAAm and AM. The living polymerization characteristics were evidenced by narrow molecular weight distribution, linear increase of molecular weight with increasing conversion, well-controlled molecular weight, and first-order polymerization kinetics. It was also found that the molecular weight is the main factors to the PDI, the bigger of the molecular weight, the wider of the PDI.TTC is of good controll of the RAFT polymerization in water solution for NIPAAm and DMAAm by the evidence of linear increase of molecular weight with increasing conversion. The results showed that steric and leaving ability of groups are the main factor infecting the controlling of CTA. The RAFT polymerization of NIPAAm and DMAAm in the presence of TTC showed that the simpler system and more moderate monomer activity were in favor of RAFT agent to control molecular weight and PDI. Polymer with higher molcular weight often meant wider PDI. It was also found that CTA was selective to monomer. TTC revealed stronger ability in controlling polymerization of NIPAAm than DMAAm in the water solution RAFT polymerization.In this research, the effects of dosage of CTA, the ratio of CTA to monomer, concentration of monomer in water, time and temperature of polymerization on PDI were also observed. Furthermore, several amphiphilic polymers such as PDMAAm-b-PS, PS-b-PAA and PAA-b-PBA were synthesized by RAFT polymerization of St and BA using macromolecular chain transfer agents, which were prepared by RAFT polymerization of DMAAm and AA in the presence of CDPEDB and TTC.