Formation and structure of slightly anionically charged nanoemulsions obtained by the phase inversion concentration (PIC) method

Abstract

While nanoemulsions (10-200 nm) are not thermodynamically stable systems they can exhibit quite long term stability. In this paper oil/surfactant mixtures, containing diethylhexyl carbonate/ phenoxyethanol/parabens as oil and polyglyceryl-4 laurate/dilauryl citrate as surfactant, form nanoemulsions simply by dilution with water, i.e. by means of the phase inversion concentration (PIC) method. In order to study this highly interesting phenomenon an investigation at constant oil-tosurfactant (O/S) ratio was done by means of viscosity, conductivity, and UV/Vis-transmittance measurements. This phase study as a function of the dilution by water shows that at an intermediate water content a two-phase system of bicontinuous structure is formed, which exhibits a very pronounced viscosity and conductivity maximum shortly before the homogeneous nanoemulsion phase is reached. In the same region SANS shows a high degree of ordering of this bicontinuous structure. SANS and cryo-TEM investigations of the nanoemulsion regime show an increasing average size with dilution and, more interestingly, the presence of two populations with different average particle sizes around 10-15 nm and 25-40 nm. The relative proportion of each population depends on the amount of added water, leading to an average growth of the particle size with increasing dilution.

Structure and dynamics of nanoemulsions: Insights from combining dynamic and static neutron scattering

“…The normalized size distribution function f (R,x 1,2,...,i ) can be of any type but for our purposes we focused on a bimodal log-normal distributions, which has previously been shown to fit data from such systems [9]. The normalized log-normal distribution function is defined as…”

“…The investigated system is a multicomponent system, where we concentrate on the already well-studied nanoemulsion range [9]. In order to obtain detailed structural and dynamical information we studied this system by means of SANS and NSE using both the hydrogenated and deuterated oil (DEHC).…”

“…In a recent investigation [9] we studied the formation of nanoemulsions based on polyglyceryl-4 laurate/dilauryl citrate as surfactant and bis(2-ethylhexyl) carbonate-phenoxyethanolparabens as oil, which are long-time stable even without the addition of an osmotic agent. Below a concentration of surfactant-oil of 20 wt% metastable nanoemulsion droplets are formed with an average droplet radius of 20-40 nm.…”

“…Nanoemulsions are conventionally formed either by higher-energy input methods (high-pressure homogenization, ultrasonication, etc.) [1,2] but low-energy methods such as the phase inversion temperature (PIT) method [3][4][5] or the phase inversion concentration (composition) (PIC) method [6][7][8][9] have been employed increasingly in recent times. Especially the PIC method, where one obtains a nanoemulsion simply by diluting an appropriate surfactant-oil mixture with water is very attractive as it is a very mild method for obtaining nanoemulsions in a very simple fashion.…”

Enhancement of the Wettability and Lubrication of Shale Rock via Nanoemulsions

“…In this work, rock with a porosity of 11.6% and a permeability of 0.0001-1 mD was derived from Jimusaer dense oil reservoir [3][4][5][6][7]. The average density and viscosity of the crude oil were, respectively, 0.888 g/cm 3 and 73.45 mPa⋅s.…”