Morphology and pervaporation performance of ionic liquid and waterborne polyurethane composite membranes

Separation of Benzene/Cyclohexane Mixtures by Pervaporation Using Poly (Ethylene-Co-Vinylalcohol) and Carbon Nanotube-Filled Poly (Vinyl Alcohol-Co-Ethylene) Membranes

Poly(ethylene-co-vinylalcohol) (E-VOH) and carbon nanotube-filled poly (vinyl alcohol-co-ethylene) (E-VOH/CNT) were used as membranes to separate benzene/cyclohexane mixtures by pervaporation technique. To reach this goal, E-VOH and E-VOH/CNT membranes were prepared by solvent casting method and characterized by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The swelling tests were used to study the mass transfer of the benzene/cyclohexane mixture and their pure components. The separation by pervaporation process was carried out at 25 °C in which the effect of CNTs incorporated into E-VOH matrix and the initial concentration of benzene in the feed on the permeate flux, j, and separation factor, β, performance was investigated. The results obtained were very promising, in which the integration of CNTs through E-VOH chains increased the absorption area and raised the flux to 740 g/m2∙h. The separation factor increased to 9.03 and the pervaporation separation reached an index of 5942.2 g/m2∙h for the azeotropic mixture during 3 h of the separation process. In contrast, for the unfilled E-VOH membrane, it was found that these parameters were a rise of 280 g∙m−2∙h−1, separation factor of 12.90 and pervaporation separation index of 3332.0 g/m2∙h, under the same conditions. Likewise, the calculation of the performance of the E-VOH/CNT membrane with regard to that of the unfilled membrane indicated 2.64 for the total flux and 0.70 for the separation factor. It was also revealed that the best compromise of the filled membrane in terms of total cumulative flux and separation factor is obtained for the feed containing the azeotropic mixture.

Heterogenized Imidazolium-Based Ionic Liquids in Pebax®Rnew. Thermal, Gas Transport and Antimicrobial Properties

Imidazolium-based ionic liquids (ILs) have interesting antimicrobial activity and their inclusion in a flexible film is ideal to take advantage of their properties in practical applications. Poly(ether-block-amide) (Pebax®Rnew) films were prepared by solution casting, loading two synthetized ILs (1-hexadecyl-3-methylimidazolium dimethyl-5-sulfoisophthalate [Hdmim][DMSIP], IL1 and 1-octyloximethyl-3-methylimidazolium hexafluorophosphate [OOMmim][PF6], IL2) up to 5 wt.%. The ILs were characterized by 1H NMR and MALDI-TOF spectroscopy. The films were investigated for miscibility, morphology, wettability, spectral properties and gas transport. The films display a good thermal stability (>200 °C). Differential scanning calorimetry (DSC) proves phase separation in the blends, that is consistent with FTIR analysis and with the island-like surface morphology observed in the micrographs. Gas permeability tests revealed that the IL-loaded films are dense and poreless, keeping the selectivity of the polymer matrix with a somewhat lessened permeability owing to the impermeable ILs crystals. The film antimicrobial activity, evaluated against Gram-negative and Gram-positive bacterial strains, was correlated to the structure of the incorporated ILs. The smaller IL2 salt did not modify the hydrophobic nature of the neat polymer and was readily released from the films. Instead, IL1, having a longer alkyl chain in the cation, provided a promising antimicrobial activity with a good combination of hydrophilicity, permeability and thermal stability.

Preparation and Characterization of Cellulose Acetate Propionate Films Functionalized with Reactive Ionic Liquids

1-(1,3-diethoxy-1,3-dioxopropan-2-ylo)-3-methylimidazolium bromide (RIL1_Br), 1-(2-etoxy-2-oxoethyl)-3-methylimidazolium bromide (RIL2_Br), 1-(2-etoxy-2-oxoethyl)-3-methylimidazolium tetrafluoroborate (RIL3_BF4) ionic liquids were synthesized. Subsequently, the dense cellulose acetate propionate (CAP)-based materials containing from 9 to 28.6 wt % of these reactive ionic liquids were elaborated. Reactive ionic liquids (RILs) were immobilized in CAP as a result of the transesterification reaction. The yield of this reaction was over 90% with respect to the used RIL. The physicochemical properties of resultant films were studied using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM), and thermogravimetric analysis (TGA). The RIL incorporation influenced the morphology of films by increasing their surface roughness with the rise of RIL content. The thermal stability of CAP-based membranes was dependent on the nature of the ionic liquid. Nevertheless, it was proven that CAP films containing RILs were stable up to 120-150 °C. Transport properties were characterized by water permeation tests. It was found that the type and the amount of the ionic liquid in the CAP matrix substantially influenced the transport properties of the prepared hybrid materials.