Tavana H, Lam C N C, Grundke K, Friedel P, Kwok D Y, Hair M L, Neumann A W
Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, ON M5S 3G8, Canada.
J Colloid Interface Sci. 2004 Nov 15;279(2):493-502. doi: 10.1016/j.jcis.2004.06.090.
Well-measured contact angles with different solid-liquid systems fall approximately on smooth patterns when plotted versus liquid surface tension. However, there are deviations of 1 degrees -3 degrees , which are outside the error limits. It is the purpose of this paper to elucidate the reasons for such deviations. Two types of liquids were selected for advancing contact angle measurements on Teflon AF 1600 coated surfaces: a series of n-alkanes ranging from n-hexane to n-hexadecane and five liquids consisting of bulky molecules, octamethylcyclotetrasiloxane (OMCTS), methyl salicylate, tetralin, cis-decalin, and octamethyltrisiloxane (OMTS). It was found that contact angles of the liquids with bulky molecules fall on a perfectly smooth curve corresponding to a solid surface tension of 13.64 +/- 0.1 mJ/m2. However, contact angles of n-alkanes deviated from this curve by up to 3 degrees in a complicated fashion. The observed trend suggests that more than one mechanism is responsible for the deviations. Substrate-induced rearrangement of liquid molecules in the close vicinity of the surface in the case of long-chain n-alkanes and adsorption of vapor onto the solid surface in the case of short-chain n-alkanes are the most likely explanations. The results suggest that liquids with bulky molecules appear to be suitable for contact angle measurements to characterize energetics of polymeric surfaces.
当与液体表面张力作图时，不同固液体系的精确测量接触角大致呈平滑模式。然而，存在1度至3度的偏差，超出了误差范围。本文旨在阐明这种偏差的原因。选择了两种类型的液体用于在涂覆有特氟龙AF 1600的表面上进行前进接触角测量：一系列从正己烷到正十六烷的正构烷烃以及由大分子组成的五种液体，八甲基环四硅氧烷（OMCTS）、水杨酸甲酯、四氢化萘、顺式十氢化萘和八甲基三硅氧烷（OMTS）。发现具有大分子的液体的接触角落在对应于固体表面张力为13.64±0.1 mJ/m²的完美平滑曲线上。然而，正构烷烃的接触角以复杂的方式偏离该曲线多达3度。观察到的趋势表明，不止一种机制导致了这些偏差。对于长链正构烷烃，表面附近液体分子的底物诱导重排以及对于短链正构烷烃，蒸汽在固体表面的吸附是最有可能的解释。结果表明，具有大分子的液体似乎适合用于接触角测量以表征聚合物表面的能量学。
