Thermoregulated Liquid/liquid Biphasic Catalysis In ATRP

In this thesis, thermoregulated liquid/liquid biphasic catalysis was applied in atomtransfer radical polymerization (ATRP) to achieve homogeneous polymerization,separating metal catalyst from the product and recycling the catalyst. Firstly, effect ofsolvents for atom transfer radical polymerization using activators generated by electrontransfer (AGET ATRP) were investigated in monophasic solvent, which is benefit forfurther study of liquid/liquid biphasic system. Secondly, thermoregulated phase-transfercatalysis (TRPTC) was successfully applied in AGET ATRP system and it achievedhomogeneous catalysis, successful separation and recycling of a catalyst complex frompolymer products via the phase-transfer characteristics of a thermo-responsivemonofunctional ligand in aqueous organic biphasic system. Finally, the strategy ofthermoregulated phase-separable catalysis (TPSC) was applied to initiators for continuousactivator regeneration ATRP (ICAR ATRP) and catalyst complex was reused by separatingthe two different layers easily.System I: AGET ATRP of styrene (St) and methyl methacrylate (MMA) in bulk and indifferent solvents were investigated using FeCl.36H2O as the catalyst, ascorbic acid sodiumsalt (AsAc-Na) as the reducing agent, and tetrabutylammonium bromide (TBABr) as theligand. It was found that the Mn,GPCvalues of the resultant polymers increase with themonomer conversion and are close to their corresponding theoretical ones and themolecular weight distributions of the polymers keep low. The living features of theobtained polymers were verified by chain end analysis and chain-extension experiments.Polymerization in THF show three advantages compared with that in bulk and toluene1)shortening the induction period;2) enhancing the polymerization rate;3) having a bettercontrollability.System II: The concept of TRPTC for an aqueous–organic biphasic system wasapplied in Cu(II)-mediated ATRP of MMA. Herein, AGET ATRP was used to establishthe TRPTC-based AGET ATRP system using2-cyanoprop-2-yl1-dithionaphthalate (CPDN) as an alkyl pseudohalide initiator, CuBr2as the catalyst and ascorbic acid (AsAc)as the reducing agent. It used a thermo-responsive ligand, which enabled the transfer of thecatalyst complex into the organic phase from the aqueous phase upon heating, thusachieving homogeneous polymerization; and the catalyst complex could retransfer into theaqueous phase from the organic phase thereby realizing the separation and recycling of thecatalyst complex upon cooling. Well-defined PMMA with controlled molecular weight andnarrow molecular weight distribution could be obtained by TRPTC-based AGET ATRP.Furthermore, the polymerization of MMA could be successfully carried out even when theamount of catalyst was reduced to the ppm level. The features of controlled/“living”radical polymerization of MMA were verified by chain end analysis and chain-extensionexperiments.System III: The strategy of thermo-regulated phase-separable catalysis (TPSC) wasapplied to Cu(II)-mediated ATRP of MMA in a p-xylene/PEG-200biphasic system. ICARATRP was used to establish the TPSC-based ICAR ATRP system using TPMA as a ligand,EBPAas an initiator, CuBr2as a catalyst and AIBN as a reducing agent. By heating to70oC,unlimited miscibility of both solvents was achieved and the polymerization can be carriedout under monophasic conditions, then on cooling to25oC, the mixture separated into twophase again. Catalyst complex stayed in PEG-200phase while the obtained polymersstayed in p-xylene phase and the catalyst can removed from the result polymers byseparating the two layers easily and reused again.