Carboxymethyl Imidazolium Research Articles

Designing the anti-biofouling surface of an ultrafiltration membrane with a novel zwitterionic poly(aryl ether oxadiazole) containing benzimidazole

To enhance the anti-fouling performance of ultrafiltration (UF) membrane, a novel zwitterionic poly(aryl ether oxadiazole) containing benzimidazole (ZB-PAEO) was synthesized through a two-step process consisting of low-temperature polycondensation and quaternization, which contains two pairs of zwitterionic groups in one polymerization unit and the anti-bacterial imidazole groups. A series of ZB-PAEO membranes with different ZB-PAEO contents were fabricated by the phase inversion process, and their microstructure and performances were tested and characterized. The introduction of carboxymethyl imidazolium groups enhanced the membrane hydrophilicity, substantially strengthening the anti-fouling property and reducing irreversible fouling. Likewise, ZB-PAEO membranes exhibited outstanding anti-biofouling property due to the strong hydration shell formed by the combination of two pairs of zwitterions in a repeating unit with abundant water molecules and the anti-biofouling resistance of the carboxymethyl imidazolium groups. This zwitterionic modification method can be readily extended to various materials and membrane systems to upgrade the anti-fouling property and water permeability.

PH-Responsive Polyoxometalate-Based Supramolecular Hybrid Nanomaterials and Application as Renewable Catalyst for Dyes

Keggin-type polyoxometalate (POM), phosphotungstic acid (H3PW12O40), was encapsulated by an oppositely charged COOH-functionalized surface active ionic liquid (SAIL), N-decyl-N′-carboxymethyl imidazolium bromide ([N-C10, N′-COOH-Im]Br), with the assistance of an ionic self-assembly (ISA) process in an aqueous environment. The as-prepared POM/SAIL material possesses multiple active properties, including reversible pH-response and renewable catalyst for dye degradation. Specifically, the POM-based hybrid materials show a great enhancement in catalytic efficiency when it is employed in degradation of methyl orange (MO) in aqueous solution. Furthermore, the electrostatic repulsions between POM and the deprotonated SAIL may result in the pH-induced disassembly and assembly of the hybrid nanomaterials, which provides an expedient method to regenerate the catalytic activity. Therefore, the presented POM/SAIL hybrid materials are expected to improve the common poisoning issue of the traditional heterogeneous cata...

Rational Design of Multiple-Stimulus-Responsive Materials via Supramolecular Self-Assembly

In this report, multiple-stimulus-responsive materials were synthesized via supramolecular self-assembly. One-dimensional nanorods were constructed by the self-aggregation of 4-(phenyl-azo)benzoic acid (PBA) molecules in aqueous solution at pH 3.2. As the pH of the solution was increased to 6.5, these nanorods transformed into two-dimensional polygons. Upon UV irradiation, the as-prepared nanorods disappeared completely, and nanospheres were subsequently obtained. On the basis of the weak interactions between PBA and additive molecules, for example, N-alkyl-N′-carboxymethyl imidazolium bromide, β-cyclodextrin, and cetyltrimethylammonium bromide, materials with various morphologies were also fabricated by a surfactant-assistant self-assembly strategy. Noteworthy is that Salvia officinalis-shaped material is among them. To the best of our knowledge, this type of microstructured material has been rarely reported. In addition, slender fibers, sphere-like particles, and aggregates of spheres were also observed...

Efficient and selective removal of dyes using imidazolium-based supramolecular gels.

A supramolecular gel was constructed by using an imidazolium-based surfactant, N-cetyl-N'-carboxymethyl imidazolium bromide ([N-C16, N'-CO2H-Im]Br), in the DMSO/H2O binary solvent mixtures and investigated as an adsorbent for removing dyes from aqueous solution. The self-assembled gel displays a morphology of microplatelets stacked in bilayer units with interdigitated hydrocarbon tails, and the structure remains unchanged below the sol-gel transition temperature. The gel also exhibits a strong birefringence property and excellent mechanical strength. In particular, the gels show superior performance in removal of anionic dye molecules, for example, removing 80% of eosin Y within 10 min, The constructed gels also present excellent salinity tolerance, even when the concentration of NaCl is 1000 times higher than that of the dye, and can maintain their high efficiency after 25 cycles, indicative of their promise in water treatment.

Interaction between Zwitterionic Surface Activity Ionic Liquid and Anionic Surfactant: Na+-Driven Wormlike Micelles

The physicochemical properties of the mixed zwitterionic surface activity ionic liquid/anionic surfactant (N-alkyl-N'-carboxymethyl imidazolium inner salts/sodium dodecyl sulfate, [N-C(12), N'-CO(2)-Im]/SDS) at various molar ratios (R(1) = C([N-C(12),N'-CO(2)-Im])/(C([N-C(12),N'-CO(2)-Im]) + C(SDS)) were investigated by surface tension and steady-state fluorescence measurements. The results show that the mixed [N-C(12), N'-CO(2)-Im]/SDS system has a much lower cmc value and higher surface activity than individual surfactant. Compared with the mixed zwitterionic betaine surfactant/SDS system, the mixture studied exhibits a stronger synergism, i.e., more negative interaction parameters (β(m) and β(σ)). Through addition of NaCl, the wormlike micelles (WMs) could be formed in a [N-C(12), N'-CO(2)-Im]/SDS system. Steady and dynamic rheology was employed to characterize the WMs with different surfactant ratio (R(1)), NaCl concentration, and temperature. An optimal composition, viz., C(T) = 60 mM, R(1) = 0.45, and C(NaCl) = 0.10 M, was detected to form the strongest and longest wormlike micelles. Compared with the WMs formed by a traditional zwitterionic C(12) betaine/anionic surfactant mixture (e.g., laurylamidopropyl betaine/SDS), the WMs studied have a stronger network structure, which is expected to have potential applications in some fields, such as in nanomaterials synthesis, personal care products, and flooding liquid for tertiary oil recovery.

Surface adsorption and micelle formation of imidazolium-based zwitterionic surface active ionic liquids in aqueous solution

A novel class of zwitterionic surface active ionic liquids (SAILs), N-alkyl-N′-carboxymethyl imidazolium inner salts ([NCn, N′CO2Im], n=10, 12, 14), was synthesized. Their aggregation behavior in aqueous solution was investigated by surface tension, isothermal titration calorimetry, and steady-state fluorescence. Compared with the reported imidazolium-based cationic SAILs, 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br) and zwitterionic betaine surfactants, (CnH2n+1N(CH3)2CH2COO−), [NCn, N′CO2Im] exhibits significantly lower critical micelle concentration (cmc) and surface tension at cmc (γcmc) values. It is attributed to the incorporation of a deprotonated carboxylic group into the head group, which weakens the electrostatic repulsion between head groups and favors micellization. The micellar aggregation number of [NCn, N′CO2Im] is larger than that of [Cnmim]Br, while less than that of CnH2n+1N(CH3)2CH2COO−. Similar to the traditional zwitterionic surfactants, the surface activity and adsorption properties of [NC12, N′CO2Im] at air/water interface have a slight variation with temperature, pH, and ionic strength. This indicates that the present zwitterionic SAILs display the aggregation behavior much similar to zwitterionic surfactants, distinctly different from imidazolium-based cationic SAILs. Sets in low sensitivity to the environmental conditions, superior surface activity and unique physicochemical properties of ionic liquids, [NCn, N′CO2Im] can be exploited for utilizing as a potential substitute for conventional surfactants in certain fields.

Aggregation behavior of COOH-functionalized imidazolium-based surface active ionic liquids in aqueous solution

A series of novel COOH-functionalized imidazolium-based surface active ionic liquids (SAILs), N-alkyl-N′-carboxymethyl imidazolium bromide ([N-Cn, N′-CO2H-Im]Br, n=10, 12, 14), was synthesized. Their aggregation behavior in aqueous solution was investigated by surface tension and steady-state fluorescence measurements. From surface tension data, a group of micellization parameters was obtained. Compared with 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br) bearing the same hydrocarbon chain, [N-Cn, N′-CO2H-Im]Br exhibits considerably lower critical micelle concentration (cmc) and surface tension at cmc (γcmc), higher adsorption efficiency (pC20) and effectiveness of surface tension reduction (πcmc), indicating the incorporation of carboxyl group favors micelle formation. The average aggregation number (Nagg) values of [N-Cn, N′-CO2H-Im]Br, determined by fluorescence quenching method, are slightly different from those of [Cnmim]Br. The effect of temperature on the aggregation behavior of [N-C12, N′-CO2H-Im]Br was also studied. It is found that there exists a minimum cmc at nearly 38°C, which is higher than that of [C12mim]Br.