Ionic liquid-based aqueous biphasic systems (IL-based ABSs) offer a benign alternative process for conventional extraction systems with volatile organic solvents to separate biomass. Designing an IL-based ABS with excellent phase splitting ability, remarkable extraction efficiency, and good biocompatibility remains challenging. In this work, we report a series of novel ABSs using biocompatible ILs composed of long chain carboxylate anions and a cholinium cation that are all derived from biomass. This strategy introduced long alkyl chains into the anions, which not only significantly increased the hydrogen bond (HB) acceptor ability of the carboxylate anions through a remarkable electron-donating effect but also ensured good hydrophobicity for achieving better phase splitting. The developed IL-based ABS demonstrated a relatively broad biphasic area and extraordinary extraction efficiency for amino acids and bioactive compounds with distribution coefficients for tryptophan, phenylalanine, and caffeine of 58.5, 120 (120 was set as a maximum value for the partition coefficient because in some cases the concentration of the extracted material in the salt-rich phase was below the limit of detection), and 120, respectively, which were remarkably higher than those obtained in ABS with conventional ILs. This work shows that the long chain carboxylate anion is critical for the excellent extraction performance of the developed ABS and that their distribution coefficients increased with increasing anion alkyl chain lengths. In addition, liquid crystal structures were observed when the carbon number of the carboxylate anion of the ILs exceeded eight; thus, IL-based ABS with liquid crystal structures were reported for the first time.
Ionic liquid (IL)‐based aqueous biphasic systems (ABSs) provide a sustainable and efficient alternative to conventional liquid–liquid extraction techniques and can be used for the extraction, recovery, and purification of diverse solutes. However, the construction of a high‐performance ABS that has both excellent phase separation ability and extraction performance remains challenging. This study concerns the preparation of a family of novel ABSs based on poly(ionic liquid)s (PILs) with customized structure and controllable molecular weight for the extraction of bioactive compounds. Several tailor‐made PILs consisting of a hydrophobic backbone, hydrophilic imidazolium pendant groups and strong hydrogen bonding basic counteranions are prepared by reversible addition fragmentation chain‐transfer polymerization. The PILs have a perfect balance of hydrophobicity/hydrophilicity and functionality, affording outstanding phase separation, which was better than with either the IL monomer poly(1‐butyl‐3‐vinylimidazolium bromide ([BVIm]Br) or the normal free‐radical polymer P[BVIm]Br*. More importantly, PIL‐based ABSs exhibited unprecedented high partition coefficients for six bioactive compounds including tryptophan, phenylalanine, and caffeine, as well as high extraction yields. The performance of the PIL‐based ABSs could also be tuned by changing the molecular weight and anionic character of the PILs. This work shows that tailor‐made PIL‐based ABSs are a promising platform for bioactive compound extraction and provides significant clues for the design of new ABSs for various applications.
Lower critical solution temperature (LCST) behavior is a well-known thermo-response and materials with LCST behavior are attractive in nanostructured material applications. However, traditional LCST materials often sacrifice the uptake capacity of nanostructured materials to enable a good phase separation performance due to their inherent contradiction. Here, a novel aqueous LCST system based on a series of nanostructured long-chain carboxylate ionic liquids (LCC-ILs) was designed. The amphiphilic LCC-ILs, with a high density of hydration sites and hydrophobic nanodomains, exhibited sensitive thermoresponsive behavior within a wide LCST temperature (10–80 °C) and a high uptake capacity of nanostructured materials. A recorded high dispersion capacity of multiwalled carbon nanotubes (MWCNTs), up to 1.3 mg mL–1 was achieved as well as a good dispersion performance for reduced graphene oxide, and metal nanoparaticles. A deep understanding of the nanostructure of the LCST system was further revealed by detailed characterizations.
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