Simultaneous Living Radical Polymerization With Different Mechanism

Recently, on the basis of the fundamental principle and idea , a series of living radical polymerization have been proceeded simultaneously .1. A novel simultaneous normal and reverse initiation ATRP (SRNI-ATRP)In comparison with nomal ATRP, no reduced transition-metal complex was used as catalyst; with RATRP no ordinary initiator such as AIBN was used as initiator, the polymerizations of MMA in the presence of oxidized transition-metal complex (CuCl2·2H2O/PMDETA, FeCl3·6H2O/MA5-DETA) as catalyst and ethyl-2-bromoisobutyrate(EbiB), metyl-2- bromo-propionate(MBP), as initiator were carried out. The molecular weight distribution of the resulting polymer was rather narrow (Mw/Mn =1.10-1.20) and the system showed good controllability. So it can be considered as a novel simultaneous reverse and normal initiate atom transfer radical polymerization (SRNI-ATRP).In SRNI-ATRP, a litter of AIBN is necessary for initiating polymerization, meanwhile in the novel SRNI-ATRP, a few radical generated from the hot-polymerization of MMA at 90℃replacing AIBN reacted with the oxidized-transition-metal complex, and resulted reduced-transition-metal complex, so as to build a radical transfer equilibrium, the ATRP was proceeded. 2. Simultaneous Reverse Iodine Transfer Polymerization/Reverse Atom Transfer Radical Polymerization (RITP/RATRP) of methyl methacrylate(MMA)In comparison with the ATRP system, the RATRP system overcome the two major drawbacks: the toxicity of the halide species RX and the unstability of reduced- transition-metal complex catalyst in air, but with rather broader distribution of the resulting polymers. The RATRP can easily proceed in solvent and emulsion. RITP is one of the simplest living radical polymerization and can carry out in the presence of iodine after a long induction period. RATRP are composed of monomer, AIBN and transition-metal complex whereas RITP are composed of monomer, iodine and AIBN, in view of the similarity, it is convenient to improve RATRP with adding iodine into the polymerization system, or improve RITP with the oxide transition-metal complex.The mechanism of simultaneous RITP/RATRP is shown as follows: the polymerization can be devided into five reactions: when the system is heated, the free radical is generated from decomposition of AIBN [1], a part of that firstly reacts in situ with iodine to produceα-iodoisobutyrontrile [2]. There is a longer induction period, which is calculated by AIBN decomposition kinetics, when there is no high-oxidation state transition metal halide complex. The radical reacts with high oxidation state transition metal complex to build the atom transfer equilibrium when RATRP is proceeded at the same time [3], resulting low oxidation state transition metal halide complex is oxidized by iodine [4]. The induction period is shortened and to accelerate the polymerization rate of MMA. The growing free radical reacts with iodide to set up a chain transfer equilibrium [5], which is so-called RITP polymerization. 3.The effect of ligand with living H on ATRPConsidering DETA has five living H and the MA5-DETA is a good ligand, the effect of ligand with different numer of living H on ATRP is studied. It is found that the polymerization is greatly effected by ligands with different number of living H when DCT is used as the initiator, CuCl as catalyst, and MAn-DETA (n = 0-5) as the ligand respectively: to accelerate the polymerization rate, to change the average molecular weight of resulting polymers. When DETA and MA3-DETA is added into the polymerization system respectively, the molecular weight of the resulting polymer is five and three times of that without adding DETA, MA3-DETA . The molecular weight of the resulting polymer with DETA is twice than the resulting polymer without MA3-DETA. The reaction of remained terminal–Cl with living H of DETA, MA3-DETA may be the cause of the phenomenon. A new reaction of terminal of resulting polymer for ATRP may be found.