School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
J Phys Chem B. 2010 Jan 28;114(3):1350-60. doi: 10.1021/jp910649a.
The phase behavior and self-assembled microstructures of a range of oligo(oxyethylene)-n-alkyl ether (C(i)E(j)) surfactants has been investigated in propylammonium nitrate (PAN), a room temperature ionic liquid. Micelles and single-phase microemulsions were all found to form at alkyl chain lengths from dodecyl to octadecyl, and lyotropic liquid crystals formed with hexadecyl chains or longer. Small-angle neutron scattering (SANS) shows that self-assembly occurs by solvophobic interactions driving the aggregation of the alkyl chains, but several results indicate that these are weaker in PAN than in water or ethylammonium nitrate, due chiefly to the hydrophobicity of PAN. Longer alkyl chains are needed for lyotropic liquid crystals to form, and higher surfactant concentrations are needed to form a single phase microemulsion. Conductivity shows these microemulsions to be weakly structured, and relatively insensitive to oil or surfactant molecular structure, unlike water-based systems. However, SANS contrast variation reveals a nanosegregation of oil from the alkyl tails of surfactants within the microemulsion, and may suggest a cosurfactant-like role for the propylammonium cation. Molecular areas within microemulsions and lamellar phases are larger than corresponding water- or ethylammonium nitrate-based systems due to the large molecular volume of the solvating PANs.
研究了一系列的聚氧乙烯-n-烷基醚（C(i)E(j)）表面活性剂在丙铵硝酸酯（PAN），一种室温离子液体中的相行为和自组装微观结构。在从十二烷基到十八烷基的烷基链长度范围内，均发现形成胶束和单相微乳液，并且具有十六烷基链或更长链的形成溶致液晶。小角中子散射（SANS）表明，自组装是通过疏溶剂相互作用驱动烷基链的聚集而发生的，但是有几个结果表明，这些相互作用在 PAN 中比在水或硝酸乙酯中弱，主要是由于 PAN 的疏水性。形成溶致液晶需要更长的烷基链，并且需要更高的表面活性剂浓度才能形成单相微乳液。电导率表明这些微乳液结构较弱，并且对油或表面活性剂分子结构的敏感性相对较低，与水基体系不同。然而，SANS 对比变化揭示了微乳液中油从表面活性剂的烷基尾部纳米分离，并且可能表明丙铵阳离子具有类似助表面活性剂的作用。由于溶剂化的 PAN 的大分子量，微乳液和层状相中的分子面积大于相应的基于水或硝酸乙酯的体系。
