Living Radical Polymerization With Inhibitors And Iodine And Novel Homogeneous Initiator CAN

The thesis consists of three parts: Effect of inhibitors on radical polymerization and atom transfer radical polymerization (ATRP) of MMA; Degenerative transfer radical polymerization (DT) of MMA with I₂ as a transfer agent and AIBN/I₂ system in situ initiated ATRP of MMA; Ceric ion homogeneous redox systems for polymerization of vinyl monomers and effect of HMPA on polymerization.1. The living characteristic of inhibitions for radical polymerization was studied. It was found that both the conversion and the initiating efficiency of methyl methacrylate (MMA) polymerization system were decreased in the presence of small amounts of addition inhibitions 2,4,6-trinitrophenol (TNP) or Benzoquinone (BQ), the system exhibited some retardation characteristics; at the same time, the molecular weights of obtained polymers was small and the molecular weight distributions (MWD) was narrow, it was suggested that this polymerization system exhibited some "living"/controlled radical polymerization characteristics. However, chain transfer inhibitions such as 4-methoxylphenol (4-MP) and hydroquinone (HQ) cannot acquire the similar results. 'H NMR was used to characterize the structures of resultant polymers and the mechanism was also investigated.Effect of a series of inhibitors as additives on atom transfer radical polymerization (ATRP) of MMA with FeCl2/PPh3 as the catalyst system was studied, including TNP, 4-MP, HQ and nitrobenzene (NB). It was found that TNP was the only efficient additive for ATRP among these inhibitors. In the presence of small amounts of TNP, the polymerization proceeded rapidly after induction period, and gave the polymers with controlled molecular weights and narrow MWD. The initiating efficiency of the modified catalyst system with TNP increased. The mechanism was proposed and confirmed by the end group analysis of the polymer.2. Degenerative transfer radical polymerization (DT) of MMA was achieved using iodine (I2) as a transfer agent and 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. After a short induction period the conversion increases with time and the molecular weights of the polymers increased linearly with the conversion and the MWD of obtained polymers were relatively narrow (Mw/Mn<1.5). The influence of the concentration of I2 and temperature on the polymerization was studied. *H NMR spectrum for the reaction solution of I2 with AIBN in toluene, I2 with MMA and the polymerization system of MMA/AIBN/I2 in 20/1/0.6 molar ratio at 90°C was measured respectively. The results indicated that h reacted with AIBN at 90 °C to give the corresponding iodide (CH3)2(CN)C-I, which was supposed to act as a transfer agent. The end groups of (CH3)2(CN)C- and -CH2(CH3)(COOCH3)C-I were detected indicating I2 and iodides formed in situ mediated DT polymerization. The end group of -Cft=CCH3COOCH3 from the elimination of iodo-terminated PMMA was also existed, which indicated iodo-terminated chain was unstable and sensitive to moisture and light. It was suggested that all the polymerization reactions should performed in dark.AIBN/12/toluene system was used as the initiator in the ATRP of MMA. With CuBr/MAs-DETA as catalyst, after a short induction period the conversion increases with time and the molecular weights of the polymers increased linearly with the conversion and the MWD of obtained polymers were relatively narrow (Mw/Mn=1.13-1.32). PMDETA as ligand results a short induction period and a rapid polymerization but broadens the MWD (Mw/Mn= 1.23-1.48). The influence of solution and the concentration of initiator on the polymerization were studied. 'H NMR spectrum for the production of initiator reaction solution indicated that h reacted with AIBN at 90 °C to give the corresponding iodide (CH3)2(CN)C-I, which was supposed to act as both initiator of ATRP and chain transfer agent of DT polymerization. The end group analysis of PMMAsuggested the polymerization is initiated by dimethyl isobutyronitrile radicals formed from the redox reaction of (CH3)2(CN)C-I with CuBr/Ligand. 3. A homogeneous redox initiator system with eerie ammonium nitrate (CAN) in N,N-dimethyl-formamide(DMF) was reported in this paper. CAN/DMF homogeneously initiated solution polymerization of methyl acrylate (MA), ethyl acrylate (EA), Butyl acrylate (n-BA), 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA) and styrene (St) etc. It was found that the polymerization rate was fast at low temperature (even at 0°C) for MA and EA, and increased with temperature. CAN/DMF system can not initiate vinyl acetate (VAC) perhaps an organic redox reaction was occurred.HMPA was added to the polymerization system as a coordination agent, which enhanced the polymerization rate of MMA in lower temperature (40 °C), the similar acceleration results were observed in polymerization of MA and St. Effects of the HMPA concentration and temperature on polymerization were discussed in detail. 'H NMR was used to characterize the structures of resultant polymers and the mechanism was also investigated. This redox syetem provided a new homogeneous initiator for polymerization of vinyl monomers in organic phase.