The introduction of external CO₂ could reversibly convert tertiary amines into quaternary ammonium salts, enabling demulsification/emulsification switching of emulsions or latexes. However, CO₂-switchable oligomeric or low-molecular-weight polymeric surfactants are rarely researched. In this study, 2-(dimethylamino)ethyl methacrylate and stearyl methacrylate are chosen to synthesize a switchable oligomeric surfactant (OS). The conductivity of OS aqueous solution (0.2 wt%) increased from 14.0 to 329 μS cm⁻¹ by adding and removing CO₂, which proved a good performance of OS in response to the CO₂ stimulus. The most important finding was that the crude oil emulsion containing OS was reversibly degraded and re-formed by the alternate CO₂ and N₂ treatment. In contrast to that, the investigated PS latex system underwent apparent stratification after the N₂ bubbling, but it regained a homogeneous phase upon the N₂ bubbling. The particle size of PS latex varied between 245 nm and 130 μm, and zeta potential changed from −43.2 to −5.8 mV, which demonstrated that the PS latex stability might break and recover by addition and removal of CO₂. This work is expected to open a new window for the CO₂-stimulated reversible emulsification of emulsions or polymer latexes.

中文翻译：

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具有 CO2 可切换表面活性的低分子量聚合物

外部CO ₂的引入可以将叔胺可逆地转化为季铵盐，从而实现乳液或乳胶的破乳/乳化切换。然而，CO _{2 可}转换的低聚物或低分子量聚合物表面活性剂很少被研究。在这项研究中，选择甲基丙烯酸 2-（二甲氨基）乙酯和甲基丙烯酸硬脂酯来合成可转换的低聚表面活性剂 (OS)。通过添加和去除 CO ₂，OS 水溶液 (0.2 wt%) 的电导率从 14.0 增加到 329 μS cm ^-1，证明 OS 对 CO ₂具有良好的响应性能刺激。最重要的发现是含有 OS 的原油乳液被 CO ₂和 N ₂交替处理可逆地降解和重新形成。与此相反，所研究的PS乳胶体系中的正后行表观分层₂鼓泡，但它在N个重新获得均相₂鼓泡。PS胶乳的粒径在245 nm和130 μm之间变化，zeta电位从-43.2 mV变为-5.8 mV，这表明PS胶乳的稳定性可能因CO _{2 的}加入和去除而破坏和恢复。这项工作有望为 CO ₂刺激的乳液或聚合物胶乳的可逆乳化打开一扇新窗口。