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

Ultrasonic characterization of ultrasound contrast agents

The main constituent of an ultrasound contrast agent (UCA) is gas-filled microbubbles. An average UCA contains billions per ml. These microbubbles are excellent ultrasound scatterers due to their high compressibility. In an ultrasound field they act as resonant systems, resulting in harmonic energy in the backscattered ultrasound signal, such as energy at the subharmonic, ultraharmonic and higher harmonic frequencies. This harmonic energy is exploited for contrast enhanced imaging to discriminate the contrast agent from surrounding tissue. The amount of harmonic energy that the contrast agent bubbles generate depends on the bubble characteristics in combination with the ultrasound field applied. This paper summarizes different strategies to characterize the UCAs. These strategies can be divided into acoustic and optical methods, which focus on the linear or nonlinear responses of the contrast agent bubbles. In addition, the characteristics of individual bubbles can be determined or the bubbles can be examined when they are part of a population. Recently, especially optical methods have proven their value to study individual bubbles. This paper concludes by showing some examples of optically observed typical behavior of contrast bubbles in ultrasound fields

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