Multifunctional Initiator-mediator Combos: Synthesis And Application In Living Radical Polymerization

In this thesis, three dual functional reagents which acted as initiator and mediator simultaneously were designed and synthesized. Then, the application of these reagents in corresponding controlled/“living” radical polymerization were studied. The current research provided an efficient way to simplify the polymerization components, which would evidently benefit for reducing possible side reaction caused by the complicated components as well as achieving precise control of the polymer structure. The detailed investigations were summarized as follows:Firstly, a dual functional reagent named N2 which containing both the thermal azo initiator group and bromine based ATRP initiator group was synthesized. The atom transfer radical polymerization(ATRP) of methyl methacrylate(MMA) was investigated by using N2 as both the initiator and reducing agent. The results showed that polymers with defined structures and controllable molecular weights as well as narrow molecular weight distributions were obtained. The polymerization of MMA using N2 as dual functional reagent has been proved as a typical living radical polymerization. Polymers with determined end group structure were obtained which was demonstrated by 1H NMR spectroscopy and MALDI-TOF MS spectrum. Besides, N2 can be applied in the living radical polymerization of other methyl acrylate monomers, such as t BMA and DMAEMA. Both of copper and iron based catalyst system could be used. The concentration of copper catalyst could even be reduced to ppm level(~ 10 ppm). The possible polymerization mechanism was proposed as a modified ICAR ATRP process according to the polymerization behavior and structure analysis. The application of current dual functional reagent showed benefit for simplifying ICAR ATRP components with comparable controllability for polymerization.Then, a dual functional reagent named X7 that containing both the thermal azo initiator group and xanthate group was synthesized. Reversible addition-fregmentation chain transfer(RAFT) polymerization of vinyl acetate(VAc) was investigated in the presence of X7. The polymerization of VAc was conducted smoothly in the presence of X7 which was acted as both the initiator and chain transfer agent at 60 o C. The polymerization behavior was proved similar to that of the traditional RAFT polymerization of VAc, while simplified the polymerization system, thus typical living radical polymerization in a low monomer conversion(< 50 %). However, it was not well controllable under a high monomer conversion(> 50 %) for the molecular weight distribution of obtained polymer was a little wide(> 1.4), although the relative molecular weight of the obtained polymer increased linearly with the monomer conversion. The structure of polymers were chararacterized by 1H NMR spectroscopy and MALDI-TOF MS spectrum.Finally, a dual functional reagent(X6) containing two trithiocarbonate groups and an azo initiator group has been used in synthesis of multiblock copolymers and cyclic polymers. At 60 o C, the multiblock copolymers of styrene and methacrylate, as well as the n-butyl acrylate and tert-butyl acrylate multiblock copolymers were synthesized successful y through RAFT polymerization in the presence of X6 which acted as both the initiator and chain transfer agent in one pot. The block numbers of n-butyl acrylate and tert-butyl acrylate multiblock copolymers could even have been reached upto 13. It showed great benefit for improving the efficiency of the synthesis of multiblock copolymers in the presence of X6 without the addition of any external initiator during the copolymerization. Besides, the synthesis of cyclic polymers in this system were explored primitively.