Yoon RH, Flinn DH, Rabinovich YI
Center for Coal and Minerals Processing, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061-0258
J Colloid Interface Sci. 1997 Jan 15;185(2):363-70. doi: 10.1006/jcis.1996.4583.
An atomic force microscope (AFM) was used to measure surface forces between a glass sphere and a silica plate. When the measurements were conducted between untreated surfaces, a "short-range" hydration force with decay lengths of 0.4 and 3.0 nm was observed. When the surfaces were hydrophobized with octadecyltrichlorosilane (OTS), on the other hand, long-range hydrophobic forces with decay lengths in the range of 2-32 nm were observed. The force measurements were conducted between surfaces having similar and dissimilar hydrophobicities so that the results may be used for deriving an empirical combining rule. It was found that the power law force constants for asymmetric interactions are close to the geometric means of those for symmetric interactions. Thus, hydrophobic force constants can be combined in the same manner as the Hamaker constants. A plot of the power law force constants versus water contact angles suggests that the hydrophobic force is uniquely determined by contact angle. These results will be useful in predicting hydrophobic forces for asymmetric interactions and in estimating hydrophobic forces from contact angles.
使用原子力显微镜（AFM）测量玻璃球与二氧化硅板之间的表面力。在未处理的表面之间进行测量时，观察到衰减长度为0.4和3.0 nm的“短程”水化力。另一方面，当表面用十八烷基三氯硅烷（OTS）疏水化时，观察到衰减长度在2 - 32 nm范围内的长程疏水力。在具有相似和不同疏水性的表面之间进行力测量，以便结果可用于推导经验组合规则。发现不对称相互作用的幂律力常数接近对称相互作用的幂律力常数的几何平均值。因此，疏水力常数可以与哈梅克常数以相同的方式组合。幂律力常数与水接触角的关系图表明，疏水力由接触角唯一确定。这些结果将有助于预测不对称相互作用的疏水力，并从接触角估计疏水力。
