Water Solubilization Using Nonionic Surfactants from Renewable Sources in Microemulsion Systems

In this study the effect of temperature, NaCl and oils (hydrocarbons: C8–C16) on the formation and solubilization capacity of the systems of oil/monoacylglycerols (MAG):ethoxylated fatty alcohols (CEO20)/propylene glycol (PG)/water was investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C) and with varied NaCl solutions (0.5; 2; 11%). Electrical conductivity measurement, FTIR spectroscopy and the DSC method were applied to determine the structure and type of the microemulsions formed. The dimension of the microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of CEO20 has a strong influence on the shape and extent of the microemulsion areas. Addition of a nonionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of isotropic region did not change considerably depending on the temperature, NaCl solution and oil type. It was found that, depending on the concentration of the surfactant mixture, it was possible to obtain U-type microemulsions with dispersed particles size distribution ranging from 25 to 50 nm and consisting of about 30–32% of the water phase in the systems. The conditions under which the microemulsion region was found (electrolyte and temperature—insensitive, comparatively low oil and surfactant concentration) could be highly useful in detergency

Thermodynamics of superspreading

A simple model for calculation of the spreading coefficient of an aqueous surfactant solution on an apolar solid is proposed. The spreading coefficient is predicted to have two components: i) the van der Waals component, which is similar to the spreading coefficient of the alkane, making up the surfactant tail; and ii) the monolayer frustration component, dependent on the bending moduli and the spontaneous curvature of the surfactant. The frustration term is minimized at a negative spontaneous curvature. In order for a solution to spread, the van der Waals component of the spreading coefficient must be positive and larger than the monolayer frustration term. The spreading is facilitated by surfactants having very short and branched alkyl tails

Relaxation kinetics of an L-3 (sponge) phase

The kinetic response of an L-3 (sponge) phase formed in the C12E5-n-decane-brine system is studied using the Joule-heating temperature jump (JHTJ) technique. The equilibrium state of the spongelike membrane is instantaneously perturbed, and the kinetic response is monitored using a multi-angle light scattering setup. These measurements yield a time-dependent scattering intensity as a function of temperature, scattering vector q, and concentration. We observed a single-exponential relaxation characteristic time, tau(m). The q dependence of the scattering amplitude shows an Omstein-Zernike behavior, but we can identify two concentration regimes with respect to the relaxation behavior. For volume fractions Phi(m) = 0.20, there is no detectable q dependence of the relaxation times, while for samples with Phi(m) > 0.30, the relaxation times display the q(-2) dependence typical of a diffusive process and with relaxation times consistent with those found in dynamic light scattering. At the intermediate concentrations, there is a transition from the q-independent to the q(-2) dependence behavior. Analysis from each concentration regime reveals distinct differences in the dependence of tau(m) on temperature and concentration, with an extraordinarily strong concentration dependence of tau(m) (tau(m) approximate to Phi(-9)) in the low concentration regime and a temperature dependence corresponding to a formal Arrhenius activation energy of 720 kJ/mol or 275 kT