Edwards Chelsea E R, Zhang Hongyi, Wang Ginny, Helgeson Matthew E
Materials Research Laboratory, University of California, Santa Barbara, California 93106-9010, United States.
Department of Chemical Engineering, University of California, Santa Barbara, California 93106-9010, United States.
Langmuir. 2025 Apr 8;41(13):8510-8523. doi: 10.1021/acs.langmuir.4c04201. Epub 2025 Mar 25.
We report the single-step formation and stability of protocell-like, core-shell coacervate droplets comprising a polyelectrolyte-rich shell and a solvent-rich vacuole core from the poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) system. These double emulsion (DE) coacervate droplets coexist with single emulsion (SE) droplets, suggesting a kinetic mechanism of formation. We use high-throughput microscopy and machine learning to classify droplet morphologies across various final compositions (polyelectrolyte ratios and salt concentrations) and processing routes (mixing rate and thermodynamic path). We find that DE droplets form preferentially over SE droplets at a wide range of compositions using a slow injection mixing rate. DE droplet formation is enhanced at lower salt (NaCl) levels and near 1:1 charge stoichiometry, showing a preference for polycation excess. DE droplets are stable to the micron scale and retain their core-shell structure even after coalescence. Nevertheless, they are metastable; direct observations of various coarsening phenomena suggest that they are primarily stabilized by the viscoelasticity and high viscosity of the polymer-rich shell. Overall, the scalable, simple mixing process used herein offers a novel mechanism to produce multiphase coacervate droplets that is orthogonal to existing routes, which require either dropwise synthesis or thermodynamic tuning.
我们报道了由聚（烯丙胺盐酸盐）（PAH）和聚（丙烯酸）（PAA）体系形成的类似原始细胞的核壳凝聚层液滴的单步形成及其稳定性，该液滴由富含聚电解质的壳和富含溶剂的液泡核组成。这些双重乳液（DE）凝聚层液滴与单重乳液（SE）液滴共存，这表明了一种形成的动力学机制。我们使用高通量显微镜和机器学习对各种最终组成（聚电解质比例和盐浓度）和加工路线（混合速率和热力学路径）下的液滴形态进行分类。我们发现，在广泛的组成范围内，使用缓慢注入混合速率时，DE液滴比SE液滴更优先形成。在较低的盐（NaCl）水平和接近1:1的电荷化学计量比时，DE液滴的形成会增强，表明更倾向于聚阳离子过量。DE液滴在微米尺度上是稳定的，即使在聚结后仍保持其核壳结构。然而，它们是亚稳态的；对各种粗化现象的直接观察表明，它们主要通过富含聚合物的壳的粘弹性和高粘度而稳定。总体而言，本文使用的可扩展、简单的混合过程提供了一种新颖的机制来生产多相凝聚层液滴，这与现有的路线正交，现有的路线要么需要逐滴合成，要么需要热力学调节。
