Paul Alison, Griffiths Peter C, Rogueda Philippe G
School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
J Pharm Pharmacol. 2005 Nov;57(11):1383-7. doi: 10.1211/jpp.57.11.0002.
The adsorption behaviour of low molecular weight poly(ethylene glycol) (PEG 600) and poly(vinyl pyrrolidone) (PVP K25) to silica particles has been investigated at room temperature (21 degrees C) in the partially fluorinated solvent 2H,3H-perfluoropentane (HPFP). PVP (absorbed amount, Gamma = 12 mg g(-1)) was found to adsorb more strongly than PEG (Gamma = 4 mg g(-1)). Both of these values were higher than observed in water. In a further distinction to the aqueous case, where PVP displaces PEG from the interface, no competitive adsorption effects were observed between these two polymers in HPFP, with the adsorbed amounts of each polymer being unchanged by the presence of the other. The stability of silica suspensions in HPFP was primarily dependent on the presence of PVP; PEG/silica systems were unstable, but PVP/silica and PEG/PVP/silica systems formed stable suspensions. All suspensions were destabilized by the addition of small (0.15 wt%) amounts of water. The observations made in this work would point to a flocculation phenomenon due to the addition of water, and not Ostwald ripening. The mechanism of this destabilization is likely to be water acting as a flocculation bridge between particles.
在室温（21摄氏度）下，于部分氟化溶剂2H,3H - 全氟戊烷（HPFP）中研究了低分子量聚乙二醇（PEG 600）和聚乙烯吡咯烷酮（PVP K25）对二氧化硅颗粒的吸附行为。发现PVP（吸附量，Γ = 12 mg g⁻¹）比PEG（Γ = 4 mg g⁻¹）吸附更强。这两个值均高于在水中观察到的值。与水相情况的另一个区别在于，在水相中PVP会将PEG从界面取代，而在HPFP中这两种聚合物之间未观察到竞争吸附效应，每种聚合物的吸附量不受另一种聚合物存在的影响。二氧化硅悬浮液在HPFP中的稳定性主要取决于PVP的存在；PEG/二氧化硅体系不稳定，但PVP/二氧化硅和PEG/PVP/二氧化硅体系形成稳定的悬浮液。所有悬浮液通过添加少量（0.15 wt%）的水而失稳。这项工作中的观察结果表明，失稳是由于添加水导致的絮凝现象，而非奥斯特瓦尔德熟化。这种失稳的机制可能是水作为颗粒之间的絮凝桥起作用。
