A multifunctional and sustainable poly(ionic liquid)-quaternized chitosan hydrogel with thermal-triggered reversible adhesion.

A quaternized chitosan (QCS)@poly(ionic liquid) (PIL) hydrogel adhesive was prepared by in-situ ultraviolet (UV)-induced copolymerization of 1-vinyl-3-butyl imidazolium bromide ([BVIm][Br]) and methacryloyloxyethyl trimethylammonium chloride (DMC) in QCS aqueous solution without using any crosslinkers, which was stably crosslinked by reversible hydrogen bonding together with ion association and exhibited excellent adhesion, plasticity, conductivity and recyclability properties. Moreover, its thermal/pH-responsive behaviors and intermolecular interaction mechanism of thermal-triggered reversible adhesion were discovered, meanwhile good biocompatibility, antibacterial properties, repeated stickiness and degradability were also proved. The results showed that the newly developed hydrogel could make various tissues, organic, inorganic or metal materials adhered tightly within 1 min; after 10 binding-peeling cycles, the adhesive strength to glass, plastic, aluminum and porcine skin still remained beyond 96 %, 98 %, 92 % and 71 % of the original, respectively. The adhesion mechanism involves ion dipole interaction, electrostatic interaction, hydrophobic interaction, coordination, cation-π interaction, H-bonding and van der Waals force. For above merits, the new tricomponent hydrogel is expected to be applied in biomedical field to achieve adjustable adhesion and on-demand peeling.

Ionic liquid@ß-cyclodextrin-gelatin composite membrane for effective separation of tea polyphenols from green tea.

A new kind of multi-component membrane was prepared by combining gelatin solution, porogen and an inclusion complex of ionic liquid (IL) and beta-cyclodextrin (ß-CD) in a simple physical manner for selective separation of tea polyphenols (TPs) from green tea crude extracts. After screening, it was found that the resulting membrane containing the IL of dicationic N-vinylimidazole proline salt ([VIm]2C3[l-pro]2) had the excellent performance for the enrichment of the target molecules. Then the newly-developed film was comprehensively characterized by scanning electron microscopy, conductivity, thermogravimetry and spectral analysis. Under pressure driving, the adsorption from an aqueous solution of a mixture of TPs and theophylline on IL@ß-CD-Gel membrane showed that the adsorption capacity for TPs was 303.45 mg/g with removal percentages of 94.38%. The experimental data fit well with pseudo-second-order model and Freundlich model. By using this composite material, a new technology of membrane separation for selective adsorption of TPs was finally established.

Systematic investigation for extraction and separation of polyphenols in tea leaves by magnetic ionic liquids.

BACKGROUND: Magnetic separation has become a mature industrial technique in many fields and its application in the food and agricultural fields is expected for further extension. Furthermore, there has been little application of magnetic ionic liquids in the preparation of bioactive products. In the present study, 0.8 mol L-1 C3 MIMFeCl4 in its aqueous solution was found to be ideal for the extraction of active constituents from tea leaves. After extraction, polyphenols, caffeine and ionic liquid were also satisfactorily separated from the crude extract by various easy operations. RESULTS: The average extraction efficiency of tea polyphenols could reach up to 185.38 g kg-1 and the recovery percent of the magnetic ionic liquid was 99.8% through an external magnetic field. The extraction process was more consistent with a pseudo-second order kinetic model. Moreover, C3 MIMFeCl4 had no effect on the stability of tea polyphenols, which was very different from ordinary ferric salt. The presence of magnetic ionic liquid had a positive effect on the antioxidant activity of the product. CONCLUSION: The developed method had a good performance for selective extraction together with separation of tea polyphenols and caffeine, which is expected in the preparation of more similar active components from food and agricultural resources as a useful multifunctional solvent. © 2018 Society of Chemical Industry.