Alkylbenzene sulfonates are one of the most important synthetic surfactant families, considering their wide applicability, cost-effectiveness, and overall consumption levels. Nevertheless, their low salt tolerance (especially divalent ion contents) prevented their wider applications such as enhanced oil recovery in high salinity reservoirs. Here, using experiments and atomistic molecular dynamics simulations, we demonstrated that the high salinity colloidal stability of alkylbenzene sulfonates can be dramatically increased by mixing with zwitterionic cosurfactants in oil-swollen micelles. By mixing with cosurfactants we had two important observations. (1) The polydispersity of surfactant mixture oil-swollen micelles were largely decreased due to the less rigid oil/water interfaces with mixed surfactants, which formed fewer but larger uniform micelles. (2) Strong dehydration of sulfonates due to the shielding from protruding more extended zwitterionic cosurfactants at the oil/water interfaces. Both observed molecular assembly characteristics triggered by the cosurfactants effectively reduced the total exposures of sulfonates to water phase that may form divalent ion bridging and large aggregates, and thus increased their high salinity colloidal stability. Lastly, it was observed that the dehydration of sulfonates was the highest at flat oil/water interfaces (very large oil-swollen micelles), which justified that adding trace amount of mineral oils may boost the high salinity colloidal stability even further.

中文翻译：

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油溶胀胶束中表面活性剂混合物的分子组装：对高盐度胶体稳定性的影响。

烷基苯磺酸盐是最重要的合成表面活性剂系列之一，考虑到它们的广泛适用性，成本效益和总体消费水平。然而，它们的低耐盐性（特别是二价离子含量）阻止了其更广泛的应用，例如在高盐度储层中提高了采收率。在这里，使用实验和原子分子动力学模拟，我们证明了在油溶胀的胶束中与两性离子助表面活性剂混合可以大大提高烷基苯磺酸盐的高盐度胶体稳定性。通过与辅助表面活性剂混合，我们得到了两个重要的观察结果。（1）由于混合表面活性剂的刚性较低的油/水界面，表面活性剂混合油溶胀胶束的多分散性大大降低，形成较少但较大的均匀胶束。（2）由于屏蔽了油/水界面处突出的更伸张的两性离子辅助表面活性剂，因此磺酸盐强烈脱水。两种观察到的由辅助表面活性剂引发的分子组装特性均有效地减少了磺酸盐对水相的总暴露，这可能形成二价离子桥连和大聚集体，从而提高了它们的高盐度胶体稳定性。最后，观察到磺酸盐的脱水在平坦的油/水界面（很大的油溶胀的胶束）处最高，这证明添加微量矿物油可以进一步提高高盐度胶体稳定性。（2）由于屏蔽了油/水界面处突出的更伸张的两性离子辅助表面活性剂，因此磺酸盐强烈脱水。两种观察到的由辅助表面活性剂引发的分子组装特性均有效地减少了磺酸盐对水相的总暴露，这可能形成二价离子桥连和大聚集体，从而提高了它们的高盐度胶体稳定性。最后，观察到磺酸盐的脱水在扁平油/水界面（非常大的油溶胀胶束）处最高，这证明添加微量矿物油可以进一步提高高盐度胶体稳定性。（2）由于屏蔽了油/水界面处突出的更伸张的两性离子辅助表面活性剂，因此磺酸盐强烈脱水。两种观察到的由辅助表面活性剂引发的分子组装特性均有效地减少了磺酸盐对水相的总暴露，这可能形成二价离子桥连和大聚集体，从而提高了它们的高盐度胶体稳定性。最后，观察到磺酸盐的脱水在扁平油/水界面（非常大的油溶胀胶束）处最高，这证明添加微量矿物油可以进一步提高高盐度胶体稳定性。两种观察到的由辅助表面活性剂引发的分子组装特性均有效地减少了磺酸盐对水相的总暴露，这可能形成二价离子桥连和大聚集体，从而提高了它们的高盐度胶体稳定性。最后，观察到磺酸盐的脱水在扁平油/水界面（非常大的油溶胀胶束）处最高，这证明添加微量矿物油可以进一步提高高盐度胶体稳定性。两种观察到的由辅助表面活性剂引发的分子组装特性均有效地减少了磺酸盐对水相的总暴露，这可能形成二价离子桥连和大聚集体，从而提高了它们的高盐度胶体稳定性。最后，观察到磺酸盐的脱水在扁平油/水界面（非常大的油溶胀胶束）处最高，这证明添加微量矿物油可以进一步提高高盐度胶体稳定性。