Facile Recyclable Copper-mediated Atom Transfer Radical Polymerization Macroligand For Thermoregulated Phase Separable Catalysis

Thermoregulated phase separable catalysis(TPSC)is a versatile and elegant tool that has attracted considerable attention,especially in polymer chemistry for efficient separation of transition metal residues from their resultant polymers.However,TPSC,in its current state is made up of small organic ligands which coordinates with CuBr₂ form soluble ligand-catalyst complexes that are easily lost during recycling and reuse.Introducing copolymer poly(ionic liquids)(PILs)into the TPSC system provides a promising strategy to solve this problem owing to their relatively enormous size.By combining the advantages of atom transfer polymerization(ATRP),poly(ionic liquids)PILs and TPSC,in this thesis,two thermoregulated tetrapodal random copolymer macroligands(PNILL)having pendent side arms of ATRP ligand and poly(ethylene glycol)(PEG),and(PILLL)having pendant side arms of ATRP ligand,PEG and ionic liquid were designed and synthesized via free radical polymerization.The facile designs of PNILL and PILLL may be economical if they were adopted on a commercial scale.The two macroligands were characterized using ¹HNMR spectroscopy and their molecular weights determined by GPC.Preliminary tests conducted indicated that PNILL failed to meet one of the essential requirements of the biphasic system and hence could not be further applied in the TPSC system.This is because the optimal organic solvent pair selected,cyclohexane,precipitated PMMA in situ and was difficult to separate from the macroligand-catalyst complex.Meanwhile,PILLL coordinated with CuBr₂ to generate a macroligand-catalyst complex which was applied in TPSC via the(initiators for continuous activator regeneration)ICAR ATRP system.The newly constructed TPSC system was actually equipped with the advantages of an in situ simultaneous recycle of both the ligand and the transition metal catalyst by simply modulating the temperature of the polymerization process.The polymerization kinetics of the macroligand-catalyst complex system closely resembled the first-order kinetics with respect to time with monomer conversion nearly reaching as high as(>92%)and a narrow molecular weight distributions of(M_w/M_n?1.42).In addition,the catalytic recycling efficiency was relatively more than 94%after five recycling experiments while the residual transition metal in the polymeric solution was less than 2.1 ppm.