Shen Amy Q, Wang Danhong, Spicer Patrick T
Mechanical and Aerospace Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, and Complex Fluids Group, Procter and Gamble Co., West Chester, Ohio 45069, USA.
Langmuir. 2007 Dec 18;23(26):12821-6. doi: 10.1021/la7013946. Epub 2007 Nov 14.
The emulsion templating of ordered colloidal microsphere assemblies by Manoharan et al. involves a consolidation process where dispersed phase fluid is transported from droplets into a continuous phase. Consolidation can be approximated as a diffusion process with moving boundaries. The kinetics of consolidation are investigated here by following droplet shrinkage with time as a prelude to understanding rate effects on assembly structure. Consolidation kinetics are influenced by liquid diffusivity, the number of colloidal particles in a droplet, and the surfactant concentration. While surfactant exhibits little effect well below its critical micelle concentration (CMC) value, it significantly slows consolidation above the CMC. For a specific continuous phase (i.e., silicone oil and fluorinated silicone oil), with proper scalings, the droplet size shrinks with time following a power law independent of droplet diameter, surfactant concentrations, and particle number concentration. The power law exponent varies from 1/2 to 2/3 with different continuous oil phases as a result of concentration and interfacial effects. This study leads to an improved understanding of colloidal microstructure development at interfaces that can be applied in novel materials synthesis and drug delivery areas.
马诺哈兰等人提出的有序胶体微球组装体的乳液模板法涉及一个固结过程，在此过程中，分散相流体从液滴传输到连续相中。固结可近似为一个具有移动边界的扩散过程。本文通过跟踪液滴随时间的收缩情况来研究固结动力学，以此作为理解速率对组装结构影响的前奏。固结动力学受液体扩散率、液滴中胶体颗粒的数量以及表面活性剂浓度的影响。当表面活性剂浓度远低于其临界胶束浓度（CMC）值时，其影响很小，但在高于CMC时，它会显著减缓固结过程。对于特定的连续相（即硅油和氟化硅油），在适当的尺度下，液滴尺寸随时间以幂律形式收缩，该幂律与液滴直径、表面活性剂浓度和颗粒数浓度无关。由于浓度和界面效应，幂律指数随不同的连续油相在1/2到2/3之间变化。这项研究有助于更好地理解界面处胶体微观结构的形成，这可应用于新型材料合成和药物递送领域。
