Institut National de Recherche et d'Analyse Physico-Chimique, Pôle Technologique de Sidi Thabet, 2020 Sidi Thabet, Tunisia.
Langmuir. 2012 Dec 21;28(51):17597-608. doi: 10.1021/la303469j. Epub 2012 Dec 12.
Double emulsions of the W/O/W type are compartmented materials suitable for encapsulation and sustained release of hydrophilic compounds. Initially, the inner aqueous droplets contain an encapsulated compound (EC), and the external phase comprises an osmotic regulator (OR). Over time, water and the solutes dissolved in it tend to be transferred from one aqueous compartment to the other across the oil phase. Water transfer being by far the fastest process, osmotic equilibration of two compartments is permanently ensured. Since the transport of the EC and OR generally occurs at dissimilar rates, the osmotic regulation process provokes a continuous flux of water that modifies the inner and outer volumes. We fabricated W/O/W emulsions stabilized by a couple of amphiphilic polymers, and we measured the inward and outward diffusion kinetics of the solutes. The phenomenology was explored by varying the chemical nature of the OR while keeping the same EC or vice versa. Microscope observations revealed different evolution scenarios, depending on the relative rates of transfer of the EC and OR. Structural evolution was mainly determined by the permeation ratio between the EC and the OR, irrespective of their chemical nature. In particular, a regime leading to droplet emptying was identified. In all cases, evolution was due to diffusion/permeation phenomena and coalescence was marginal. Results were discussed within the frame of a simple mean-field model taking into account the diffusive transfer of the solutes.
W/O/W 型的双乳液是一种分隔材料，适合于亲水性化合物的封装和缓释。最初，内部水相液滴包含被包封的化合物（EC），外部相包含渗透压调节剂（OR）。随着时间的推移，水和溶解在其中的溶质倾向于从一个水相隔间通过油相转移到另一个水相隔间。由于水的转移是迄今为止最快的过程，因此两个隔间的渗透平衡可以永久保证。由于 EC 和 OR 的传输通常以不同的速率发生，因此渗透压调节过程会引发持续的水流，从而改变内外体积。我们制备了由一对两亲聚合物稳定的 W/O/W 乳液，并测量了溶质的向内和向外扩散动力学。通过改变渗透压调节剂的化学性质而保持相同的 EC 或反之亦然，我们探索了这种现象学。显微镜观察揭示了不同的演变情景，这取决于 EC 和 OR 的转移相对速率。结构演变主要取决于 EC 和 OR 之间的渗透比，而与它们的化学性质无关。特别是，确定了一个导致液滴排空的区域。在所有情况下，演变都是由于扩散/渗透现象引起的，聚并作用可以忽略不计。结果在考虑溶质扩散转移的简单平均场模型框架内进行了讨论。
