Particle aggregation mechanisms in ionic liquids.
Particle aggregation mechanisms in ionic liquids.
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DOI：
10.1039/c4cp00804a
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发表时间：
2014-04
期刊：
影响因子：
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通讯作者：
I. Szilágyi;T. Szabó;A. Désert;G. Trefalt;Tamás Oncsik;M. Borkovec
中科院分区：
文献类型：
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作者：
I. Szilágyi;T. Szabó;A. Désert;G. Trefalt;Tamás Oncsik;M. Borkovec
采用时间分辨光散射技术研究了亚微米和纳米级聚苯乙烯乳胶粒子在室温离子液体及其水溶液中的聚集行为。聚集率被发现以系统的方式随IL-水摩尔比而变化。在水侧，聚集速率最初很小，但随着IL含量的增加而迅速增加，并达到平台值。这种行为类似于简单的盐，并且可以通过双层和货车范德华力的竞争来合理化，正如Derjaguin，朗道，Verwey和Overbeek（DLVO）的经典理论所推测的那样。在IL侧，聚集再次减慢。两个通用的机制可以被确定为负责在离子液体中的稳定，即粘性稳定和溶剂化稳定。粘性稳定化在高粘性离子液体中是重要的，因为它源于由于粘性液体中扩散的阻碍而导致的扩散控制聚集的减缓。溶剂化稳定化机制是系统特异性的，但可以导致离子液体中聚集速率的显著减慢。这种机制是有关的排斥溶剂化力，是由于层的IL接近的表面在IL的操作。这两种稳定机制被怀疑是通用的，因为它们都发生在不同的离子液体中，并且对于表面功能和尺寸不同的颗粒。
Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperature ionic liquids (ILs) and in their water mixtures by time-resolved light scattering. The aggregation rates were found to vary with the IL-to-water molar ratio in a systematic way. At the water side, the aggregation rate is initially small, but increases rapidly with increasing IL content, and reaches a plateau value. This behaviour resembles simple salts, and can be rationalized by the competition of double-layer and van der Waals forces as surmised by the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). At the IL side, aggregation slows down again. Two generic mechanisms could be identified to be responsible for the stabilization in ILs, namely viscous stabilization and solvation stabilization. Viscous stabilization is important in highly viscous ILs, as it originates from the slowdown of the diffusion controlled aggregation due to the hindrance of the diffusion in a viscous liquid. The solvation stabilization mechanism is system specific, but can lead to a dramatic slowdown of the aggregation rate in ILs. This mechanism is related to repulsive solvation forces that are operational in ILs due to the layering of the ILs close to the surfaces. These two stabilization mechanisms are suspected to be generic, as they both occur in different ILs, and for particles differing in surface functionalities and size.