The confinement of PVP in AOT microemulsions: Effect of water content and PVP concentration regime on electrical percolation phenomenon

Abstract

Water in oil microemulsions have actually been regarded as nanometric colloids of great importance in the encapsulation industry. The present work focused mainly on the impact of water and Polyvinilpyrrolidone (PVP) confined in the water/Sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/isooctane microemulsion system on the percolation phenomenon. Firslty, a viscometric study on PVP in a diluted and semi-diluted regime showed a significant reduction in its structural and dimensional parameters (intrinsic viscosity [η] and PVP blob sizeξ) with higher temperature (above 318 K). The aggregation of PVP chains have also been observed. Furthermore, electrical measurements conducted on 5 microemulsions with different water content revealed a critical value of water to AOT molar ratio W0,c=waterAOT from which the percolation begins. This was explained by the variation of micellar size and shape with the addition of water. A major variation of this critical value is emphasized with the PVP confinement. Thereafter, the variance in PVP confined concentration (from dilute to semi-dilute regime) showed the effects of concentration on percolation parameters. Temperature-induced percolation decreased with the addition of PVP. The activation energy of percolation presents a great increase in the presence of PVP, emphasizing the growth of charges exchanged between the droplets. The application of scale laws near the percolation threshold has underlined the accelerating role of PVP in the percolation process.