<span style="font-size:11.0pt;mso-bidi-font-size: 14.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US; mso-bidi-language:HI" lang="EN-US">Synergistic interactions in W/O microemulsions containing imidazolium based C₁₂mimBr and sodium lauryl sulfate</span>

Abstract

The physicochemical properties and synergistic effects of W/O microemulsion systems containing imidazolium based surfactant, 1-dodecyl-3-methylimidazolium bromide (C₁₂mimBr)-sodium lauryl sulfate (SLS)/ alcohol/alkane/5% NaCl solution at different molar ratios of water-to-surfactant (ω₀) are studied. The W/O microemulsions are formed at the molar fractions of SLS-to-C₁₂mimBr+SLS (X_SLS) ranges of 0.0-0.3 and 0.7-1.0. The synergism between C₁₂mimBr and SLS can be seen from the values of <i>X</i>_{_{<img src='http://www.niscair.res.in/jinfo/avalue.gif' border=0>}}(mole fraction of alcohol in the oil phase), X_{_{<img src='http://www.niscair.res.in/jinfo/ivalue.gif' border=0>}}(mole fraction of alcohol in the interfacial layer) and -<i>G</i>_{_{<img src='http://www.niscair.res.in/jinfo/o.gif' border=0>}}_→<i>i</i> (the standard free energy change of transferring alcohol from the continuous oil phase to the interfacial layer). The increase in the values of <i>X</i>_{_{<img src='http://www.niscair.res.in/jinfo/avalue.gif' border=0>}} and X_{_{<img src='http://www.niscair.res.in/jinfo/ivalue.gif' border=0>}}, and the decrease in -<i>G</i>_{_{<img src='http://www.niscair.res.in/jinfo/o.gif' border=0>}}_→<i>i</i> values with ω₀ is attributed to the increasing hydrophilicity of the microemulsions. By increasing the carbon chain lengths of the alcohol molecules, or by increasing the salt concentrations, the values of <i>X</i>_{_{<img src='http://www.niscair.res.in/jinfo/avalue.gif' border=0>}} and X_{_{<img src='http://www.niscair.res.in/jinfo/ivalue.gif' border=0>}} decrease, whereas that of -<i>G</i>_{_{<img src='http://www.niscair.res.in/jinfo/o.gif' border=0>}}_→<i>i</i> increases for the W/O microemulsions containing the mixed surfactants. On the other hand, the effect of the alkane carbon chain lengths is exactly the effect of the alcohol carbon chain lengths on the these parameters.