PROPERTIES OF FILMS OF ADSORBED FLUORINATED ACIDS
PROPERTIES OF FILMS OF ADSORBED FLUORINATED ACIDS
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DOI：
10.1021/j150513a011
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发表时间：
1954-01-01
影响因子：
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通讯作者：
ZISMAN, WA
中科院分区：
文献类型：
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作者：
HARE, EF;SHAFRIN, EG;ZISMAN, WA
用物理吸附法在铂表面制备了全氟丁酸、戊酸、己酸、辛酸、癸酸和月桂酸的单分子膜。然后通过接触角测量来表征它们对一些选定液体的润湿性能。随着酸链长度的增加，观察到接触角有规律但很小的增量。因此，尽管全氟月桂酸单分子膜提供了迄今报道的最低能量表面，但即使是非常短的酸的膜也比其他类型的表面（包括先前研究的氟化聚合物）显着更不透明。对于较短链的酸，单层形成很快;然而，两种最长链的酸需要吸附表面和酸溶液之间逐渐更长的接触时间才能形成具有最大接触角的单层。全氟酸单分子膜的显着的液体排斥性是由于存在一个暴露的平面富含全氟甲基。长链酸的电子衍射检查揭示了与此解释一致的分子取向。包括几个新的API烃类的表面张力数据异常pure.In最近的一份报告中，我们描述了非常大的接触角，几乎所有的液体在表面上形成的一个紧密堆积的吸附单层的全氟癸酸。2全氟月桂酸和四种低级同系物的出现使研究酸链长度对拒液性能的影响成为可能。这一系列酸中的较高成员应作为更紧密堆积的单层吸附，因此表现出更大的液体排斥性（或更大的接触角）。然而，由于较低的成员更容易获得，因此了解使用它们会导致多少液体排斥性损失是有趣的。此外，对全氟月桂酸膜的电子衍射分析可望提供有关吸附分子结构和取向的补充信息。
Monohiolecular films of perfluorinated butyric, valeric, caproic, caprylic, capric and lauric acids were prepared by physical adsorption on platinum from theirsolutions in organic solvents. Their wetting properties for a number of selected liquids were then characterized by contact angle measurements. Regular but small increments in the contact angles were observed with increasing acid chain length. Thus, althoughperfluorolauric acid monolayers provided the lowest energysurface yet reported, films of even the very short acids were significantly more non-wettable than other types of surfaces, including the fluorinated polymers studied earlier. For the shorter chain acids, monolayer formation was rapid; the two longest chain acids, however, required progressively longer periods of contact between the adsorbing surface and the acid solution for com-pletion of a monolayer exhibiting maximum contact angle. The remarkable liquid-repellency of the perfluoroacid monolayers is caused by the presence of an exposed plane rich in perfluoromethyl groups. Electron diffraction examination of the longer chain acids reveals a molecular orientation consistent with this explanation. Included are surface tension data for several new API hydrocarbons of exceptional purity.In a recent report we described the remarkably large contact angles of nearly all liquids on the surface formed by a close-packed adsorbed mono-layer of perfluorodecanoic acid. 2 The recent avail-ability of perfluorolauric acid and four lower homologs made possible the investigation of the effect of acid chain length on these liquid-repellent properties. A higher member of this series of acids should adsorb as a more closely packed monolayer and hence exhibit greater liquid repellency (or larger contact angles). Since the lower members are more available, however, it was interesting to learn how much loss of liquid repellency would result from their use. In addition, electron diffraction examination· of films of perfluorolauric acid was expected to provide supplementary information on the structure and orientation of the adsorbed mole-cules.