Polymeric surfactants play a crucial role in the flocculation-assisted coalescence process due to their unique bridging effect. However, the steric hindrance induced by their large molecules severely impedes the coalescence of oil droplets. Herein, temperature-responsive polymeric surfactants (quaternary ammonium chitosan-g-PNIPAM, Q-g-PN) with thermally-modulated structure were designed by integrating thermal responsive moieties onto cationic chitosan. The as-prepared Q-g-PN exhibited enhanced oil-water separation efficiency through a thermally regulated flocculation-coalescence process. At low temperatures, the thermal-responsive Q-g-PN remains in a flexible hydrophilic extended state, facilitating the flocculation of dispersed oil droplets through bridging via electrostatic interaction. At high temperatures, the Q-g-PN structure collapses into a hydrophobic coil state, reducing steric hindrance and enhancing hydrogen bonding to asphaltenes, thus effectively promoting oil droplet coalescence. Bottle tests demonstrated that the demulsification performance of Q-g-PN could reach up to 94 % with the Q-g-PN concentration only of 0.001 wt% via the proposed temperature-regulated flocculation-coalescence process, which was further confirmed by investigating oil droplet behavior and phase transition of Q-g-PN during through molecular dynamic (MD) simulation of the reaction process. This work presents new insights into enhancing oil-water separation efficiency by regulating the flocculation-coalescence process through precise modulation of the molecular interactions between polymeric surfactants and emulsion droplets.

中文翻译：

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通过温度响应性阳离子聚合物表面活性剂进行热调节絮凝聚结过程，以增强原油-水分离


聚合物表面活性剂由于其独特的桥接效应，在絮凝辅助聚结过程中起着至关重要的作用。然而，它们的大分子诱导的空间位阻严重阻碍了油滴的聚结。本文通过将热响应部分集成到阳离子壳聚糖上，设计了具有热调制结构的温度响应性聚合物表面活性剂 （季铵壳聚糖-g-PNIPAM， Q-g-PN）。所制备的 Q-g-PN 通过热调节的絮凝聚结过程表现出更高的油水分离效率。在低温下，热响应型 Q-g-PN 保持柔性亲水扩展状态，通过静电相互作用通过桥接促进分散油滴的絮凝。在高温下，Q-g-PN 结构塌陷成疏水线圈状态，减少空间位阻并增强与沥青质的氢键，从而有效促进油滴聚结。瓶装试验表明，通过所提出的温度调节絮凝聚结过程，当 Q-g-PN 浓度仅为 0.001 wt% 时，Q-g-PN 的破乳性能可以达到 94%，通过分子动力学 （MD） 反应过程的分子动力学 （MD） 模拟研究 Q-g-PN 的油滴行为和相变进一步证实了这一点。这项工作通过精确调节聚合物表面活性剂和乳液液滴之间的分子相互作用，通过调节絮凝-聚结过程，为提高油水分离效率提供了新的见解。