Prediction of the second critical micelle concentration of aqueous tween and span solutions via CPA EoS: Application of the quantitative theory in growth of wormlike micelles

Abstract

A new combination of previously established molecular-thermodynamic methods was offered in conjunction with the Cubic Plus Association (CPA) equation of state (EoS) for the assessment of the second critical micelle concentration (SCMC), and curvature parameters in aqueous solutions of non-ionic surfactants encompassing Tween 80, Tween 60, Span 80, and Span 60. This combination will yield a quantifiable examination that adheres to creating the micelles resembling worms, enabling the optimization of critical curvature parameters, as well as the prediction of the SCMC. This previously well-known model is reliant upon theoretical components, including chain conformation, headgroup-steric effects, and interfacial tension pertaining to the energy of micelle-free systems. So, the optimized curvature parameters obtained because of these forces can be used as the input of CPA EoS to independently count the association interactions and predict the SCMC for the first time. For the aforementioned surfactants, the first critical micelle concentration (FCMC) data was previously used to modify five pure parameters of the CPA EoS. Consequently, applying the adjusted parameters, the SCMC of noted aqueous solutions has been predicted reasonably using CPA EoS.