Construction Of Thermo-regulated Phase Separable Catalysis (TPSC) Aget Atrp System Based On Thermo-regulated Ionic Liquids

As one of the reversible-deactivation radical polymerization(RDRP) methods, activators generated by electron transfer for atom transfer radical polymerization(AGET ATRP) has been a milestone since it was developed by Matyjaszewski’s group in 2005. It provides a more convenient and facile way to synthesize well-defined polymers with pre-designed molecular weight and narrow molecular weight distribution. However, the residual metal catalyst in resultant polymers colors/pollutes the products, which further limits the application of ATRP in an industrial scale. To deal with such problem and take advantages of ionic liquids, we introduced the concept of thermo-regulated phase separable catalysis(TPSC) based on thermo-regulated ionic liquids into an AGET ATRP system, which fully facilitates to take advantages of homogeneous catalysis and heterogeneous separation of TPSC and to easily separate catalyst from polymers in situ and subsequently recycle the catalyst efficiently.System I: Herein, TPSC-based AGET ATRP system was established using styrene as the model monomer, Cu Cl2·2H2O, tris(2-pyridylmethyl)amine(TPMA), ethyl 2-bromoisobutyrate(EBi B) and glucose as the catalyst, ligand, initiator and reducing agent, respectively. A thermo-regulated ionic liquid, [CH3(OCH2CH2)16N+Et3][CH3SO3-](MPEG750NIL), the mixed solvent of toluene and n-heptane were also needed. In the polymerization, the mixture homogenizes and the polymerization proceeds under homogeneous conditions at reaction temperature(100 oC). And the system separates into a biphasic system composed of ionic liquid phase containing catalyst complex and organic phase containing polymers upon cooling to room temperature after polymerization. By simple decanting, the bottom ionic liquid phase containing catalyst complex can be recovered and reused easily and the copper catalyst could be reused for 5 times with negligible loss of catalytic activity. Besides, the polymerizations proceeded in a living fashion with controlled molecular weights and narrow molecular weight distributions, which was further evidenced by MALDI-TOF MS, polymerization kinetics and chain-extension experiments. We also successfully applied TPSC-based AGET ATRP to the polymerizations of methyl methacrylate, methyl acrylate and butyl acrylate, which indicated a wide range of monomers could be used in this TPSC-based AGET ATRP system.System II: To prevent the ligand losing and to recover the catalyst and ligand at the same time, we connected the ligand to ionic liquid by covalent bonding. Herein, we synthesized two kinds of thermo-regulated ionic liquids, which contained ligand at one of the end of the chain, and applied them to TPSC-based AGET ATRP systems. One ionic liquid was abbreviated Py-PEONIL, which contained PEO units in its main chain and the other was Py-PPEGMAIL, containing PEG units in its side chain. The experimental results indicated that the ionic liquid Py-PEONIL had a good control to methyl methacrylate but poor control to styrene, and unfortunately we have not found a suitable organic solvent to form homogeneous phase catalysis system with Py-PEONIL at reaction temperature(100 oC). As for the ionic liquid Py-PEGMAIL, it had a good control to the polymerization of styrene and it could form homogeneous phase catalysis system with the mixed toluene and heptane at reaction temperature(100 oC). However, it couldn’t separate well after polymerization and the polymerization rate was slow.