The present study is about the foaming and defoaming properties of the CO₂-switchable surfactant N,N-dimethyltetradecylamine (C₁₄DMA) and its advantages compared with the non-switchable counterpart tetradecyltrimethylammonium bromide (C₁₄TAB). In the absence of CO₂, C₁₄DMA is a water insoluble organic molecule without any surface activity thus being unable to stabilize foams. In the presence of CO₂, the head group becomes protonated which transforms the water insoluble molecule into a cationic surfactant. Comparing the surface properties and foamability of C₁₄DMA and C₁₄TAB one finds a very similar behavior. However, the foam stabilities differ depending on the gas. Foaming the two-surfactant solutions with CO₂ leads to very unstable foams in both cases. However, foaming the two surfactant solutions with N₂ reveals the switchability of C₁₄DMA: while the volume of foams stabilized with C₁₄TAB hardly changes over 1600 s, the volume of foams stabilized with C₁₄DMA decreases significantly in the same period of time. This difference is due to the fact that the surface activity, that is, the amphiphilic nature, of C₁₄DMA is continuously switching off since CO₂ is displaced by N₂ thus deprotonating and deactivating the surfactant.

中文翻译：

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CO2可转换表面活性剂的起泡和消泡性能

本研究是关于 CO ₂可转换表面活性剂 N,N-二甲基十四烷基胺 (C ₁₄ DMA) 的发泡和消泡性能及其与不可转换的对应物十四烷基三甲基溴化铵 (C ₁₄ TAB) 相比的优势。在没有CO ₂的情况下，C ₁₄ DMA 是一种不溶于水的有机分子，没有任何表面活性，因此不能稳定泡沫。在 CO ₂存在下，头部基团质子化，将水不溶性分子转化为阳离子表面活性剂。比较 C ₁₄ DMA 和 C _{14的表面性能和发泡性}TAB one 发现了一个非常相似的行为。然而，泡沫稳定性因气体而异。用CO ₂使双表面活性剂溶液起泡在两种情况下都会导致非常不稳定的泡沫。然而，用 N ₂使两种表面活性剂溶液起泡揭示了 C ₁₄ DMA 的可转换性：虽然用 C ₁₄ TAB 稳定的泡沫体积在 1600 秒内几乎没有变化，但用 C ₁₄ DMA 稳定的泡沫体积在同一时期显着减少时间。这种差异是由于 C _{14 DMA 的表面活性，即两亲性质，由于 CO 2}被 N ₂置换而不断关闭。从而使表面活性剂去质子化和失活。