화학공학소재연구정보센터
Fluid Phase Equilibria, Vol.456, 140-150, 2018
Effect of head group on the aggregation behavior of surface active ionic liquids with aromatic counterions in aqueous solutions
Aggregate behavior of N-dodecyl-N-methylpyrrolidinium salicylate ([C(12)mpyrr][Sal]) and N-dodecyl-N-methylpiperidinium salicylate ([C(12)mpip][Sal]) in aqueous solution was systematically explored, respectively. Integrated the results of this work and relevant report on 1-dodecyl-3-methylimidazolium salicylate ([C(12)mim][Sal]), regulatory effect of head group in surface active ionic liquids (SAILs) with aromatic counterion on their self-assembly behavior was demonstrated. Both [C(12)mim][Sal] and [C(12)mpip][Sal] display lower cmc value compared to [C(12)mpyrr][Sal] which was verified by surface tension and electrical conductivity measurements. The reasons behind the observed differences may lie in the intramolecular p-p interaction between unsaturated ring head groups and aromatic counterions for the [C(12)mim][Sal] and more positive interaction energy between [C(12)mpip][Sal] and water molecules than [C(12)mpyrr][Sal] calculated from density function theory (DFT). Entropy was regarded as the thermodynamic driving force during micellization process of the two SAILs within the range of temperature studied. Similar to [C(12)mim][Sal], a hexagonal liquid crystalline phase (H-1) and a cubic liquid crystalline phase (V-2) appear sequentially with the increasing concentration of [C(12)mpyrr][Sal], whereas for [C(12)mpip][Sal], only a broad region of H-1 phase was observed. Small angle X-ray scattering (SAXS) patterns suggest that analogous to [C(12)mim][Sal], higher concentrations of [C(12)mpyrr][Sal], and [C(12)mpip][Sal] and lower temperature can lead to a closer alignment of SAIL molecules in the H-1 phase. The present work is expected to enrich the research contents on self-assembly behavior of SAILs and illuminate wide potential applications in nanomaterials, drug delivery and medicine release. (C) 2017 Elsevier B.V. All rights reserved.