Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada.
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada.
J Colloid Interface Sci. 2021 Apr;587:510-521. doi: 10.1016/j.jcis.2020.10.064. Epub 2020 Oct 21.
Traditionally, double emulsions are produced in the presence of both oil-soluble and water-soluble surfactants in sequential droplet formation settings or unique fluidic designs. Micelles, assemblies of surfactants in liquid mediums, can generate single emulsion droplets without requiring input energy. We hypothesize that the synergy between nanoparticles in one phase, and micelles in the other phase can spontaneously generate double emulsions. Nanoparticles can become surface-activated by adsorbing surfactants and form the second type of emulsions from the initially emulsified phase by micelles.
We design a thermodynamically-driven emulsification platform where double emulsions are spontaneously formed as soon an aqueous nanoparticle dispersion is placed in contact with an oleic micellar solution. Confocal and cryogenic-scanning electron microscopies are utilized to characterize structure and intensity of emulsions at various concentrations of silica nanoparticle and Span micelles. The rate of particle surface activation and emulsification and the amount of water intake are quantified using dynamic light scattering, dynamic interfacial tension, and density measurements.
Nanoscale water droplets nucleate in the oil in form of swollen micelles. Over time, nanoparticles form a water-shell encapsulating the swollen-micelle rich oil phase. The gradual surfaceactivation of nanoparticles is key in self-double emulsification and controlling the emulsion intensity. We build on this new discovery and design a novel system for double emulsification. Incorporating nanoparticles into spontaneous emulsification systems opens novel routes for designing emulsion-based materials.
传统上，在顺序成滴设置或独特的流体设计中，同时存在油溶性和水溶性表面活性剂来生产双重乳液。胶束是液体介质中表面活性剂的聚集，可以生成单乳液滴，而不需要输入能量。我们假设，一个相中纳米粒子之间的协同作用和另一个相中胶束之间的协同作用可以自发地生成双重乳液。纳米粒子可以通过吸附表面活性剂而成为表面活化剂，并通过胶束从最初乳化的相中形成第二类型的乳液。
我们设计了一种热力学驱动的乳化平台，只要将水性纳米粒子分散体置于油酸胶束溶液中，就会自发形成双重乳液。利用共焦和低温扫描电子显微镜来表征在不同浓度的二氧化硅纳米粒子和 Span 胶束下乳液的结构和强度。使用动态光散射、动态界面张力和密度测量来定量测量粒子表面活化和乳化的速率以及水的摄入量。
纳米级的水滴在油中以溶胀胶束的形式成核。随着时间的推移，纳米粒子形成了一个水壳，包裹着富含溶胀胶束的油相。纳米粒子的逐渐表面活化是自双重乳化和控制乳液强度的关键。我们基于这一新发现设计了一种新型的双重乳化系统。将纳米粒子纳入自发乳化系统为设计基于乳液的材料开辟了新途径。
