Nanoemulsions Prepared by a Two-Step Low-Energy Process

Abstract

A simple low-energy two-step dilution process has been applied in oil/surfactant/water systems with pentaoxyethylene lauryl ether (C12E5), dodecyldimethylammonium bromide, sodium bis(2-ethylhexyl)sulfosuccinate, sodium n-dodecyl sulfate-pentanol, and hexadecyltrimethylammonium bromide-pentanol. Appropriate formulations were chosen for the concentrate to be diluted with water to generate oil-in-water (O/W) emulsions or nanoemulsions. For the system of decane/C12E5/water, bluish, transparent nanoemulsions having droplet radii of the order of 15 nm were formed, only when the initial concentrate was a bicontinuous microemulsion, whereas opaque emulsions were generated if the concentrate began in an emulsion-phase region. Nanoemulsions generated in the system decane/C12E5/water have been investigated both by dynamic light scattering (DLS) and contrast-variation small-angle neutron scattering (SANS). The SANS profiles show that nanodroplets exist as spherical core-shell (decane-C12E5) particles, which suffer essentially no structural change on dilution with water, at least for volume fractions phi down to 0.060. These results suggest that the nanoemulsion droplet structure is mainly controlled by the phase behavior of the initial concentrate and is largely independent of dilution. A discrepancy between apparent nanoemulsion droplet sizes was observed by comparing DLS and SANS data, which is consistent with long-range droplet interactions occurring outside of the SANS sensitivity range. These combined phase behavior, SANS, and DLS results suggest a different reason for the stability/instability of nanoemulsions compared with earlier studies, and here it is proposed that a general mechanism for nanoemulsion formation is homogeneous nucleation of oil droplets during the emulsification.

Preparation of D-limonene Oil-in-Water Nanoemulsion from an Optimum Formulation

“…The studies of emulsion and nanoemulsion range with small angle X-ray diffraction don t show any meaningful diffraction peaks due to weak diffraction. Further studies with small angle neutron diffraction will be used 7 .…”

“…The formation of smaller nanoemulsion involves homogenous nucleation of oil from bicontinuous microemulsion range upon dilution and mixing with water 7 . Hence, the smallest size nanoemulsion can be prepared from d-limonene / i-C13EO6 isopropanol , 1/1 at water fraction 60 , which is in pre-inverted bicontinuous microemulsion single phase.…”

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

“…This time span is considerably larger than the one required for the formation of doublets. The nanoemulsions studied were prepared by the phase inversion composition method [125,126,127,128], which basically consists in the sudden dilution of a pre-equilibrated system in the balance zone. The experimental determination of W as a function of the initial slope of the turbidity (τ) vs. time (t), is complemented with four theoretical models of the turbidity which depend on the average drop size and the flocculation rate.…”

Miniemulsion polymerization based on in situ surfactant formation without high-energy homogenization: effects of organic acid and counter ion

“…There are numerous reports describing miniemulsification techniques relying on catastrophic phase transitions occurring as a result of a change in temperature (phase inversion temperature method), 15,16 pressure, 17,18 pH, 19 ionic strength 20 or composition (emulsion inversion point method). 21,22 However, the application of such miniemulsification techniques to miniemulsion polymerization (as opposed to merely the miniemulsification process itself) has not been extensively investigated. [23][24][25][26] Low-energy miniemulsification can also be achieved by use of the so called in situ surfactant technique.…”