Physico‐Chemical Studies on Microemulsion: Effect of Cosurfactant Chain Length on the Phase Behavior, Formation Dynamics, Structural Parameters and Viscosity of Water/(Polysorbate‐20 + n‐Alkanol)/n‐Heptane Water‐in‐Oil Microemulsion

Abstract

The pseudo-ternary water-in-oil microemulsion system, comprising water/polyoxyethylene sorbitan monolaurate (Polysorbate-20) ? n-alkanol/n-heptane, have been studied by phase manifestation, method of dilution, viscosity and dynamic light scattering measurements. Polysorbate-20, in combination with equal mass of cosurfactants (of varying chain length, from n-butanol to n-octanol) were used in studying the systems in the temperature range 303-323 K. Appearance of turbidity was noted visually, which indicated the attainment of immiscibility or phase separation; a clear dependence of the different phases on cosurfactant chain length was noted. By employing the method of dilution, associated thermodynamic parameters for the formation of water-in-oil microemulsion droplets were derived. Different associated structural parameters were derived through further computation of the data derived from the method of dilution. Unusual behavior of Polysorbate-20, compared to the conventional ionic surfactants, was noted. Viscosity measurements, as carried out with different compositions and temperatures, revealed the temperature and water pool size dependency of the microemulsion systems. Viscosity data did not follow the same trend during heating and the cooling process, due to the condensation effect. This phenomenon was further confirmed by dynamic light scattering measurements.

Combined phase behavior, dynamic light scattering, viscosity and spectroscopic investigations of a pyridinium-based ionic liquid-in-oil microemulsion

“…IL or n-heptane was then progressively added using a Hamilton (USA) microsyringe under constant stirring. 49,50 The whole process was carried out in a controlled temperature bath (298 AE 0.1 K). The phase boundary was detected by the appearance of turbidity.…”

“…Temperature was controlled to within AE0.05 K using a built-in Peltier heating-cooling device. The instrument actually measures the diffusion coefficient (D) from which the diameter of the microemulsion droplet (d) was determined according to Stokes-Einstein's formalism: 49,50…”

Physico-Chemical Studies on the Interaction of Bacterial Polysaccharide- Surfactant Aggregates with Special Reference to their Hydrodynamic Behavior

“…Viscosity was measured at different shear rates for different SPS-surfactant concentrations. Zero shear viscosity was determined from the intercept of the plot of apparent viscosity vs. shear rate 44,45 . Temperature was controlled at 298 K using a thermostatic water bath with an accuracy of 0.1 K.…”

Optimizing Delivery Characteristics of Curcumin as a Model Drug via Tailoring Mean Diameter Ranges of Cellulose Beads

“…Among various microemulsion systems, the water-in-oil (W/O) microemulsion system with a low water ratio is more favourable due to its ability to synthesize smaller, well-dispersed, and uniform micrometer-sized particles with the help of an appropriate surfactant to stabilize the microdroplets [19,20]. Due to the nature of the microelmusion system, nonionic and nontoxic surfactants such as Span 80 or Tween 80 are the preferred choices [21,22].…”

“…The W/O microemulsion has been extensively used in various fields such as biomaterials synthesis and chemical engineering, with the surfactant monolayer providing stabilization by prohibiting direct contacts between water and oil, as well as by reducing the interfacial tension between the two immiscible 2 International Journal of Polymer Science phases. Effective dispersion of the aqueous phase in the oil phase leads to the formation of uniform microemulsion droplets which, in turn, help to maintain the shape and size of particles formed [20,23]. On the other hand, the nanoprecipitation (or solvent displacement) process could be used for the fabrication of cellulose particles of desirable particle size distributions via manipulating the synthesis parameters [24].…”