School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, Seoul 08826, Republic of Korea.
Cosmax R&I Center, Building E, Pangyo Innovalley, 255 Pangyo-ro, Bundang-gu, Seongnam 13486, Korea.
J Colloid Interface Sci. 2023 Sep 15;646:311-319. doi: 10.1016/j.jcis.2023.05.005. Epub 2023 May 8.
Eco-friendly processes that are emerging around the world require mass production of low-energy, low-cost nanoemulsions. The process involving the high-concentrated nanoemulsions and diluting them with a large amount of solvent can certainly save the cost; however, not much detailed research has been conducted on the stability mechanism and rheological characteristics of high-concentrated nanoemulsions.
In this study, we produced nanoemulsions via the microfluidization (MF) process, comparing their dispersion stability and rheological characteristics with macroemulsions across various oil and surfactant concentrations. Droplet mobility and dispersion stability depended on these concentrations, with Asakura-Osawa-type attractive depletion considering interparticle interaction's role in stability changes. We investigated nanoemulsions' long-term stability based on turbidity and droplet size changes over four weeks, proposing a stability diagram showing four different states depending on emulsification conditions.
We explored the microstructure of emulsions under varying mixing conditions, observing their effects on droplet mobility and rheological properties. We monitored changes in rheology, turbidity, and droplet size over 4 weeks, establishing stability diagrams for macro- and nanoemulsions. The stability diagrams revealed that the stability of emulsions are sensitively dependent on the droplet size, concentrations, surfactant cocentrations and the strcture of coexistent phases in case of macroscopic segregation are significantly different depending on the droplet sizes. We identified their respective stability mechanisms and discovered the relationship between stability and rheological properties for highly concentrated nanoemulsion.
世界各地正在出现的环保工艺需要大规模生产低能量、低成本的纳米乳液。通过高浓度纳米乳液并大量稀释溶剂的工艺肯定可以节省成本；然而，对于高浓度纳米乳液的稳定性机制和流变特性，并没有进行太多详细的研究。
在这项研究中，我们通过微流化（MF）工艺生产了纳米乳液，比较了它们在不同油和表面活性剂浓度下的分散稳定性和流变特性与宏观乳液的差异。液滴的迁移率和分散稳定性取决于这些浓度，考虑到颗粒间相互作用对稳定性变化的影响，采用了 Asakura-Osawa 型吸引力耗散。我们根据浊度和粒径变化研究了纳米乳液在四周内的长期稳定性，提出了一个稳定性图，根据乳化条件显示了四种不同的状态。
我们探索了不同混合条件下乳液的微观结构，观察它们对液滴迁移率和流变性质的影响。我们监测了流变学、浊度和粒径在 4 周内的变化，为宏观和纳米乳液建立了稳定性图。稳定性图表明，乳液的稳定性对粒径、浓度、表面活性剂共浓度以及共存相结构高度敏感，而宏观分相的稳定性则显著取决于粒径。我们确定了它们各自的稳定性机制，并发现了高浓度纳米乳液的稳定性与流变性质之间的关系。
