Zielińska Katarzyna, Campbell Richard A, Zarbakhsh Ali, Resmini Marina
Department of Chemistry and Biochemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
Phys Chem Chem Phys. 2017 Jul 5;19(26):17173-17179. doi: 10.1039/c7cp02979a.
We have used neutron reflectivity (NR) measurements in combination with dynamic light scattering (DLS), surface tension and ellipsometry, to study the adsorption behaviour at the air/water interface of N-isopropylacrylamide-based nanogels as a function of concentration. The data provide clear evidence that the nanogels are adsorbed at the interface in a strongly deformed shape and forming a multi-layer where the thickness increases with nanogel concentration in the bulk. The combination of surface characterisation techniques and bulk studies indicate that interfacial film formation is preferred over bulk aggregation. This observation at the air/water interface supports the Derjaguin prediction, that a sphere's interaction with a plane (the thick adsorbed nanogel layer at interface) is much larger than nanogel-nanogel (sphere-sphere) association in the bulk. These findings, in particular the changes in conformations and the thick layer adsorption at the interface as a function of concentration, impact significantly on a number of applications for which nanogels are currently being investigated. These results contribute to the understanding of the behaviour of soft colloids at the interfaces.
我们结合动态光散射（DLS）、表面张力和椭偏仪，利用中子反射率（NR）测量，研究了N-异丙基丙烯酰胺基纳米凝胶在空气/水界面的吸附行为随浓度的变化。数据提供了明确的证据，表明纳米凝胶以强烈变形的形状吸附在界面上，并形成多层结构，其厚度随本体中纳米凝胶浓度的增加而增加。表面表征技术和本体研究的结合表明，界面膜的形成优于本体聚集。在空气/水界面的这一观察结果支持了Derjaguin的预测，即球体与平面（界面处厚的吸附纳米凝胶层）的相互作用远大于本体中纳米凝胶-纳米凝胶（球体-球体）的缔合。这些发现，特别是构象变化和界面处厚层吸附随浓度的变化，对目前正在研究纳米凝胶的许多应用有重大影响。这些结果有助于理解软胶体在界面处的行为。
