Water-like ammonium-based ionic liquids for lipase activation and enzymatic polymerization

Novel dual-functionalized ammonium-based hydrophobic ionic liquids (ILs) have been synthesized by mimicking the water structure to carry both ether group (hydrogen-bond acceptor) and tert-alcohol group (hydrogen-bond donor). These ammonium-type ionic solvents exhibit the advantage of lower viscosities (as low as 129 mPa sat 30 degrees C) than the imidazolium analogue ( similar to 300 mPa sat 30 degrees C); more importantly, these water-like media are highly compatible with immobilized Candida antarctica lipase B (Novozym 435) in terms of producing high transesterification activities (1.5-fold higher than that in tert-butanol, and slightly higher than that in diisopropyl ether) and higher thermal stability than that in tert-butanol. To demonstrate the utilization of this new solvent system, enzymatic ring-opening polymerization (ROP) of epsilon-caprolactone using these water-like ILs as co-solvents was carried out to synthesize polyesters, achieving high molecular mass M-w (up to 18,000 Da) and high yields (up to 74 %).