Kinetics Of RAFT Based Living Free Radical Polymerization And Application In Synthesis Of Complex Architecture Polymer

Living free radical polymerization is one of the fastest growing points in polymer chemistry recently, and it gets more attention in Reversible Addition-fragmentation chain Transfer (RAFT) mediated living free radical polymerization owing to its mild reaction conditions, its effectiveness in controlling molecular weight and polydispersity ,its suitable to a wide range of monomers as well as its capability of synthesizing well-defined polymers such as block, graft, and hyperbranched polymers. Due to the difficulty of synthesis dithioester, the research work has not been done deeper yet. In this work, a number of dithioesters had been synthesized .Both the sorts and concentrations of dithioester were put to investigate the kinetics of RAFT process. A new polymerizable dithioester(4-vinyl benzyl dithiobenzoate) was used to synthesize branched and hyperbranched polymers. The results were as follow: First, the kinetics of RAFT based polymerization had more effective with the different structures of dithioester (Z group), the electric charge could change the order of dithioester, then affected the stablility of dithioester. Attracting electron group decreased the rate, and pushing electron group accelerated polymerization. It was found that the concentration of RAFT agents could also affect the kinetics of RAFT free radical polymerization, which meant it should be corrected with originally mechanism.Second, a polymerizable dithioester acting as RAFT agent in styrene polymerization could get the controlling chain branched polystyrene. Post-treatment with amine and Zn/HAC, the primary chain length and its distribution were fit for controlled free radical polymerization. It was first found that the double molecular weight occurred when each two terminal mercapto groups of the resulting polymers coupled to form a persulfide bonds. It could be reduced with Zn/HAC. The copolymerization of styrene and polymerizable dithioester was investigated by FT-IR spectrum, monomer reactivity ratio r1and r2 were got from the experiment. The branched polystyrene could re-propagate with styrene and initiator, and higher molecular weight polymer occurred. The result showed that the primary chainwas also fit for living free radical polymerization after post-treatment. The synthesis of homopolymer with 4-vinyl benzyl dithiobenzoate in controlled free radical polymerization showed the hyperbranched polymer occurred , and when the conversion rising to gel point , it would present the network polymer. Synthesis of the Bis(thioacyl)disulfides, and the polymerization with it as RAFT agent showed that it had an inducement period and was controlled free radical polymerization. Adjusting the ratio of initiator and Bis(thioacyl)disulfides could accelerate the polymerization and avoid the inducement period.