Hledat publikace

Ionic liquid polymer gel membranes based on poly(vinylidenefluoride-co-hexafluoropropylene)(p(VDF- HFP)) were prepare dby solvent casting from asolution in aceton e. The membranes contain from 20 wt% to 80 wt% of pure or mixed ionic liquids based on the imidazolium cation: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI])and 1-hexadecyl-3-methylimidazoliu mbis(trifluoro- methylsulfonyl)imide ([HdMIM][TFSI]).Both ionic liquids have the fluorinatedanion bis(trifluoromethyl- sulfonyl)imide, which should make them more compatible with afluoropolymermatrix, while the different tail lengths in the cation give significantlydifferent melting points. The thermal and mechanical properties of the blend membranes were evaluated and compared with the neat polymer. The perfor- mance of the membranes was tested in terms of pure gas permeability and selectivity, separation of lim- onene/carvone mixtures by pervaporation, and influence of alow water content in the feed on separation by the blended membrane. DSC analysis shows agradual decrease of the melting point of the gel and adecrease in the overall melting enthalpy with increasing IL content, whereas the melting enthalpy normalized for the polymer fraction shows an initial drop and then agradual increase. In the presence of the ionic liquid, the elastic modulus and break strength decrease dramatically, while the maximum deformation at firstincreases due to higher flexibilityof the plasticized polymer and then rapidly decreases above 40 wt% of IL as acon- sequence of the progressive decrease of the number of entanglements. The gas transport through the membranes prepare din this study was evaluated in the temperature range of 20–60 _C, which includes the melting point of the high temperat ure ionic liquid [HdMIM][TFSI]. These permeation measure ments show asignificantincrease of the permeability in the presence of the IL mixture, especially for carbon dioxide.