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首页> 外文期刊>Physics of fluids >Effect of polymer-coated gold nanoparticle stabilizers on drop coalescence
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Effect of polymer-coated gold nanoparticle stabilizers on drop coalescence

机译：聚合物涂层金纳米颗粒稳定剂对滴结的影响

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Polymer-coated gold nanoparticles (PGNPs) can be used as stabilizers in immiscible polymer blends, similar to block-copolymers (BCs). However, the PGNP gold cores increase the magnitude of the disjoining pressure (Pi), i.e., the van der Waals interaction for unit area, in the film between the drops, favoring coalescence. This might explain the counterintuitive 70% drainage time (t(d)) reduction for polymeric drops stabilized by PGNPs compared to those stabilized by BCs, as reported in recent flow-induced head-on collision experiments in extensional flow, despite PGNPs being more surface active. Knowledge of the mechanisms determining t(d) is fundamental for designing effective PGNP compatibilizers. Here, we performed a parametric study of those experiments via boundary integral simulations, treating PGNPs as surfactants and utilizing for the first time a disjoining pressure expression which includes the effect of interfacial PGNPs (Pi(PGNP)). In particular, we varied the PGNP concentration and core size in Pi(PGNP), the surface diffusivity (D-s) via the surface Peclet number, and the surface elasticity via the Marangoni number. Flow-induced coalescence was very sensitive to all three parameters. t(d) was reduced up to 60% for touching 3 nm core diameter PGNPs, increasing significantly the coalescence probability for drop sizes <5 mu m, but the soft coronas diminished this effect considerably. Thus, other causes, besides the enhanced Pi, had to be simultaneously present to explain the dramatic experimental t(d) reduction; the most likely is a D-s higher than its Stokes-Einstein relation estimate and the PGNP ligands being in a dry-brush regime, leading to entropic attraction between the drop interfaces. Published under license by AIP Publishing.
机译：聚合物涂覆的金纳米颗粒（PGNP）可用作不混溶的聚合物共混物中的稳定剂，类似于嵌段共聚物（BCS）。然而，PGNP金芯增加了在滴剂之间的薄膜中的脱充压力（Pi），即单位面积的范德瓦尔斯相互作用的幅度。这可能解释由PGNPS稳定的PGNP稳定的逆向70％的排水时间（T（d））减少与BCS稳定的那样，如近期流动引起的头部碰撞实验，尽管PGNP更具表面积积极的。确定确定T（d）的机制是设计有效PGNP兼容器的基础。这里，我们通过边界积分模拟进行了对这些实验的参数研究，将PGNP作为表面活性剂处理，并利用第一次进行界面PGNP（PI（PGNP））的抗衡性压力表达。特别地，我们通过PIE（PGNP）的PGNP浓度和核心尺寸，通过表面Peclet数和通过Marangoni数来实现表面扩散率（D-S）。流动诱导的聚结对所有三个参数非常敏感。触摸3nm核心直径PGNP的T（d）降低至60％，显着增加了下降尺寸<5μm的聚结概率<5 mu m，但软体冠状动脉显着减少了这种效果。因此，除了增强的PI之外，其他原因必须同时存在以解释戏剧性的实验性T（d）减少;最有可能的是D-S高于其斯托克斯 - 爱因斯坦关系估计，PGNP配体处于干式刷制方案，导致液滴界面之间的熵吸引力。通过AIP发布在许可证下发布。

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