Designing a robust recyclable tricopolymer poly(ionic liquid) macroligand for copper-mediated atom transfer radical polymerization in non-aqueous biphasic systems

Abstract

Thermoregulated phase separable catalysis (TPSC) in its current state involves small organic ligands that coordinate with CuBr₂ to form ligand–catalyst complexes that are easily lost during recycling and reuse. Introducing copolymer poly(ionic liquids) (PILs) into TPSC systems appears to be a promising strategy to solve this problem owing to their relatively large sizes. Herein, a thermoregulated substituted random tricopolymer poly(ionic liquid) macroligand (PILLL) with pendant side chains of an ATRP ligand, poly(ethylene glycol) (PEG) and alkylammonium ionic liquid was designed and synthesized in a facile fashion. The macroligand coordinated with CuBr₂ to generate a macroligand–catalyst complex (PILLL/CuBr₂) was applied in TPSC as an initiator for a continuous activator regeneration (ICAR) ATRP system. This newly constructed TPSC system was endowed with the advantages of in situ separation of polymers coupled with the simultaneous recycling of both the macroligand and transition metal catalyst by modulating the temperature of the polymerization process from 25 °C to 70 °C and reversing it to 25 °C. Furthermore, after performing ten recycling experiments, the catalytic recycling efficiency was still relatively high (>95%) with narrow molecular weight distributions (M_w/M_n ≤ 1.31), while the residual transition metal in the polymeric solution was lower than 2.4 ppm.