Atom Transfer Radical Polymerization With Ionic Liquids As Solvent

Atom transfer radical homopolymerizations of methyl methacrylate, acrylonitrile and their block polymerization with ionic liquids（ILs）as solvents have been performed successfully.The catalyst system is CuBr and pentamethyldiethylenetri- amine（PMDETA）and the initiator is ethyl-2-bromopropionate（EPN-Br）.The polymerization kinetics and structure of the resulted polymers have been investigated in detail.First,the atom transfer radical polymerization of methyl methacrylate was investigated.From the FTIR and ¹³C NMR analysis,it is confirmed that the chemical structure of PMMA synthesized in ILs is similar to the one obtained in conventional solvents while the stereostructure is of higher isotactic configuration when ILs are used.The sequence distribution follows Beraoullian statistics.The polymerization of MMA follows the first order kinetics in ionic liquids with the molecular weight increasing linearly with the elevation of conversion. The polydispersity is influenced by the temperature,the reaction ingredients ratios and can be controlled within 1.10 to 1.50.Compared to acetonitrile,IL not only can elevate the polymerization rate but also can increase the molecular weights.However,a great deviation of the molecular weights for the resulted products from the theoretical values is observed.The apparent energy of activation(△E_a^app)for this system is calculated to be 6.95kJ/mol,which indicates that the polymerization activity of MMA is so strong that some non-living polymerizations exist during the polymerization process.For the first time,the atom transfer radical polymerization of acrylonitrile in ILs is also investigated.The chemical structure of PAN synthesized in[bmim]Cl is identical with that obtained in DMF but the isotactic configuration is higher than that obtained in DMF.The polymerization of AN displays a first order kinetics in ILs and the molecular weight not only increases linearly with the increase of conversion but also agrees reasonably well with the theoretical molecular weight.The polydispersity is as low as 1.15.The apparent activation energy is calculated to be 38.31kJ/mol.Compared to ATRP of MMA,the ATRP of AN shows the living polymerization feature thoroughly.On the base of polymerization of MMA and AN,the atom transfer radical block polymerization of methyl methyacrylate and acrylonitrile is investigated using PAN-Br as initiator with[bmim]Cl as solvent.The proposed product of PAN-b-PMMA with no homopolymers is synthesized successfully.It is clear that the initiation efficiency of PAN-Br is higher than EPN-Br.From the FTIR and ¹³C NMR analysis,it is confirmed that the polymer is indeed PAN-b-PMMA.It configures the similarity isotactic configuration with PMMA homopolymer and the The sequence distribution also follows Bernoullian statistics.The apparent activation energy is calculated to be 26.68kJ/mol.It is concluded that ATRP is selectable for the monomer in ionic liquids.For the ATRP with [bmim]Cl as solvent,acrylonitrile is more preferable than methyl methacrylate.Furthermore,the catalyst and ligand are recycled with ILs through simple deposition,extraction and distillation.After separation,the content of residual copper in the polymer is low to 2.9×10^-3%.The recycled ILs,catalyst and ligand are resued effectively for more than 4 times without any obvious decline in conversion,molecular weights and producing polymers with low polydispersities.