Contact angle measurements and contact angle interpretation .1. Contact angle measurements by axisymmetric drop shape analysis and a goniometer sessile drop technique
Contact angle measurements and contact angle interpretation .1. Contact angle measurements by axisymmetric drop shape analysis and a goniometer sessile drop technique
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DOI：
10.1021/la9608021
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发表时间：
1997-05-14
期刊：
影响因子：
3.9
通讯作者：
Neumann, AW
中科院分区：
文献类型：
--
作者：
Kwok, DY;Gietzelt, T;Neumann, AW
用轴对称液滴形状分析法（ADSA）和传统测角仪技术分别测定了13种液体在两种含有极性基团的共聚物（聚丙撑-alt-N-（正丙基）马来酰亚胺）和聚丙撑-alt-N-（正己基）马来酰亚胺）上的低速动态接触角和静态前进接触角。在用于测量接触角的前一种技术（在三相接触线的非常低的速度下）的情况下，对于某些固-液体系观察到非常复杂的接触角响应。在特定情况下，发生滑动和粘附接触角行为，其中接触角在恒定三相接触半径下稳定地增加多达35度，并且随后由于三相接触线中的突然跳跃而急剧减小。因此，谨慎是必要的，在决定是否可以使用实验接触角来解释表面能量与杨氏方程，以及是否违反的基本假设，在所有的表面能量的方法的固体-液体系统。结果表明，如果省略不确定的接触角测量，这些共聚物的γ（LV）cos θ的值与γ（LV）在非极性表面已经众所周知的模式中平滑地变化。测角仪和ADSA接触角测量结果显示，对于具有恒定接触角的固-液体系基本相同。在使用测角器测量接触角的滑动/粘附机构的特定情况下，观察到的静态前进角对应于整个滑动/粘附行为的最大角度，如通过自动轴对称液滴形状分析记录的。因此，传统的测角仪测量可能会产生有意义和无意义的接触角的混合，没有标准来区分两者。
Low-rate dynamic contact angles and static advancing contact angles of 13 liquids were measured, respectively, by axisymmetric drop shape analysis (ADSA) and a conventional goniometer technique, on two copolymers, poly(propene-alt-N-(n-propyl)maleimide) and poly(propene-alt-N-(n-hexyl)maleimide); both have polar groups. In the case of the former technique for measuring contact angles (at very low velocity of the three-phase contact line), very complex contact angle responses were observed for some solid-liquid systems. In a specific case, slip and stick contact angle behavior occurs where the contact angle increases steadily by as much as 35 degrees at constant three-phase contact radius and subsequently decreases sharply due to a sudden jump in the three-phase contact line. Thus, circumspection is necessary in the decision whether or not the experimental contact angles can be used to interpret surface energetics in conjunction with Young's equation and whether the solid-liquid systems violate the basic assumptions made in all surface energetics approaches. It was shown that if one omits the inconclusive contact angle measurements, the values of gamma(lv) cos theta change smoothly with gamma(lv) for these copolymers in a pattern already well-known for nonpolar surfaces. Goniometer and ADSA contact angle measurements were shown to be essentially identical for solid-liquid systems which have constant contact angles. In the specific case of the slip/stick mechanism using a goniometer for the contact angle measurements, the observed static advancing angle corresponds to the maximum angle of the entire slip/stick behavior, as registered by the automated axisymmetric drop shape analysis. Thus, conventional goniometer measurements may produce a mixture of meaningful and meaningless contact angles, with no criteria to distinguish between the two.