Carnachan Ross J, Bokhari Maria, Przyborski Stefan A, Cameron Neil R
Interdisciplinary Research Centre in Polymer Science and Technology, Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
Interdisciplinary Research Centre in Polymer Science and Technology, Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK and School of Biological and Biomedical Sciences, Durham University, DH1 3LE, UK.
Soft Matter. 2006 Jun 20;2(7):608-616. doi: 10.1039/b603211g.
Methods with which to tailor the morphology of polystyrene-based emulsion-templated (PolyHIPE) materials are presented. Increasing the temperature of the aqueous phase used to prepare the parent emulsion leads to an increase in average void and interconnect size in the resulting porous material. Additionally, the presence in the aqueous phase of small quantities of organic additives that are capable of partitioning between the two emulsion phases also affects the morphology of the porous material obtained. The additives examined were tetrahydrofuran (THF), methanol and poly(ethylene glycol) (PEG), all of which were found to increase the average void and interconnect diameters. It is suggested that THF and, to a lesser extent, PEG enhance Ostwald ripening, resulting in emulsion coarsening over time. Evidence for this was gleaned from NMR experiments to determine the rates of water diffusion in each emulsion. However, methanol was shown not to affect the rate of water diffusion. An alternative mechanism by which methanol could affect the emulsion stability is by depleting surfactant from the interface. However, higher levels of surfactant in emulsions containing methanol did not have a significant effect on morphology. To explain this, we suggest that methanol may result in depletion of surfactant from the emulsion interface, however additional surfactant serves not only to replace this depleted surfactant but also to increase the number of w/o micelles in the continuous phase. These facilitate transport of water between droplets, thus negating the effect of replacing the surfactant lost from the interface.
本文介绍了用于定制聚苯乙烯基乳液模板化（PolyHIPE）材料形态的方法。提高用于制备母乳液的水相温度会导致所得多孔材料的平均孔隙和互连尺寸增加。此外，水相中存在能够在两个乳液相之间分配的少量有机添加剂也会影响所得多孔材料的形态。所研究的添加剂为四氢呋喃（THF）、甲醇和聚乙二醇（PEG），发现所有这些添加剂都会增加平均孔隙和互连直径。据推测，THF以及程度稍低的PEG会增强奥斯特瓦尔德熟化，导致乳液随时间粗化。这一点的证据是通过核磁共振实验收集的，以确定每种乳液中水的扩散速率。然而，甲醇并未显示出会影响水的扩散速率。甲醇影响乳液稳定性的另一种机制可能是从界面耗尽表面活性剂。然而，含甲醇乳液中较高水平的表面活性剂对形态没有显著影响。为了解释这一点，我们认为甲醇可能导致乳液界面处表面活性剂的耗尽，然而额外的表面活性剂不仅用于替代这种耗尽的表面活性剂，还用于增加连续相中油包水胶束的数量。这些促进了液滴之间水的传输，从而抵消了替代从界面流失的表面活性剂的影响。
