Knoben W, Besseling N A M, Stuart M A Cohen
Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
Langmuir. 2007 May 22;23(11):6095-105. doi: 10.1021/la062656x. Epub 2007 Apr 18.
In this paper, the investigation of surface forces in semidilute solutions of a nonadsorbing hydrogen-bonded reversible supramolecular polymer is described. Colloidal probe atomic force microscopy was used for direct measurement of depletion forces. Hydrodynamic drag on the AFM cantilever with the colloidal probe was measured both far away from and close to the planar substrate surface. The results indicate that the presence of the depletion layer causes slip at the surfaces with a large apparent slip length. Our analysis explains how the presence of slip enables the measurement of (relatively weak) depletion forces in solutions with a high viscosity by significantly reducing the hydrodynamic forces. The range and magnitude of the measured depletion forces are qualitatively in agreement with previous experiments and theoretical predictions. Due to the relatively large experimental error, no quantitative conclusions can be drawn. Depletion-induced phase separation of suspensions of stearylated silica particles was also observed. Phase separation becomes more pronounced with increasing polymer concentration.
本文描述了对一种非吸附性氢键可逆超分子聚合物的半稀溶液中表面力的研究。采用胶体探针原子力显微镜直接测量耗尽力。在远离和平行于平面基底表面的位置，均测量了带有胶体探针的原子力显微镜悬臂上的流体动力学阻力。结果表明，耗尽层的存在导致表面出现滑移，且表观滑移长度较大。我们的分析解释了滑移的存在如何通过显著降低流体动力学力，使得在高粘度溶液中能够测量（相对较弱的）耗尽力。所测得的耗尽力的范围和大小在定性上与先前的实验和理论预测一致。由于实验误差相对较大，无法得出定量结论。还观察到了硬脂酸化二氧化硅颗粒悬浮液的耗尽诱导相分离。随着聚合物浓度的增加，相分离变得更加明显。
