Kim Sunhyung, Hyun Kyu, Moon Joo Yong, Clasen Christian, Ahn Kyung Hyun
Department of Chemical Engineering, KU Leuven, University of Leuven , W. de Croylaan 46, B-3001 Heverlee, Belgium.
Langmuir. 2015 Feb 17;31(6):1892-900. doi: 10.1021/la504578x. Epub 2015 Feb 5.
We study the mechanism of depletion stabilization and the resultant microstructure of aqueous suspensions of nanosized silica and poly(vinyl alcohol) (PVA). Rheology, small-angle light scattering (SALS), and small-angle X-ray scattering (SAXS) techniques enable us to analyze the microstructure at broad length scale from single particle size to the size of a cluster of aggregated particles. As PVA concentration increases, the microstructure evolves from bridging flocculation, steric stabilization, depletion flocculation to depletion stabilization. To our surprise, when depletion stabilization occurs, the suspension shows the stabilization at the cluster length scale, while maintaining fractal aggregates at the particle length scale. This sharply contrasts previously reported studies on the depletion stabilization of microsized particle and polymer suspensions, which exhibits the stabilization at the particle length scale. On the basis of the evaluation of depletion interaction, we propose that the depletion energy barrier exists between clusters rather than particles due to the comparable size of silica particle and the radius gyration of PVA.
我们研究了纳米二氧化硅和聚乙烯醇（PVA）水悬浮液的耗尽稳定化机制及其产生的微观结构。流变学、小角光散射（SALS）和小角X射线散射（SAXS）技术使我们能够在从单个颗粒尺寸到聚集颗粒簇尺寸的广泛长度尺度上分析微观结构。随着PVA浓度的增加，微观结构从桥连絮凝、空间稳定、耗尽絮凝演变为耗尽稳定。令我们惊讶的是，当发生耗尽稳定时，悬浮液在簇长度尺度上表现出稳定性，而在颗粒长度尺度上保持分形聚集体。这与先前报道的关于微米级颗粒和聚合物悬浮液耗尽稳定化的研究形成鲜明对比，后者在颗粒长度尺度上表现出稳定性。基于对耗尽相互作用的评估，我们提出由于二氧化硅颗粒尺寸与PVA的回转半径相当，耗尽能垒存在于簇之间而非颗粒之间。
