The interaction forces between silica surfaces modified to different degrees of hydrophobicity were measured using colloidal probe atomic force microscopy (AFM). A highly hydrophobic silica particle was prepared with octadecyltrichlorosilane (OTS), and the interaction forces were measured against silica substrates modified to produce surfaces of varying hydrophobicity. The interaction forces between the highly hydrophobic particle and a completely hydrophilic silicon wafer surface fitted well to the DLVO theory, indicating that no additional (non-DLVO) forces act between the surfaces. When the silicon wafer surface was treated to produce a contact angle of water on surface of 40°, an additional attractive force that is longer ranged than the van der Waals force was observed between the surfaces. The range and magnitude of the attractive force increase with the contact angle of water on the substrate. Beyond the effect on the contact angle, the hydrocarbon chain length and the terminal groups of hydrophobic layer on the substrate only have a minor effect on the magnitude of the force, even when the substrate is terminated with polar carboxyl groups, provided the hydrophobicity of the other surface is high.

中文翻译：

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在不对称疏水表面之间测量疏水吸引力

使用胶体探针原子力显微镜（AFM）测量了改性为不同疏水度的二氧化硅表面之间的相互作用力。用十八烷基三氯硅烷（OTS）制备了高度疏水的二氧化硅颗粒，并测量了与改性的二氧化硅基材的相互作用力，该基材经过改性以产生疏水性不同的表面。高疏水性粒子与完全亲水的硅晶圆表面之间的相互作用力非常符合DLVO理论，表明表面之间没有其他力（非DLVO）作用。当处理硅晶片表面以使水在表面上的接触角为40°时，在表面之间观察到比范德华力更长的范围的附加吸引力。吸引力的范围和大小随水在基材上的接触角而增加。除了对接触角的影响外，即使基体被极性羧基封端，基体上的疏水链的烃链长度和疏水基团的末端基团对力的大小也只具有较小的影响，前提是基体的疏水性其他表面较高。