ON THE FORMATION AND STRUCTURE OF SELF-ASSEMBLING MONOLAYERS .3. TIME OF FORMATION, SOLVENT RETENTION, AND RELEASE
ON THE FORMATION AND STRUCTURE OF SELF-ASSEMBLING MONOLAYERS .3. TIME OF FORMATION, SOLVENT RETENTION, AND RELEASE
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DOI：
10.1016/0021-9797(86)90114-1
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发表时间：
1986-08-01
影响因子：
9.9
通讯作者：
SAGIV, J
中科院分区：
文献类型：
--
作者：
GUN, J;SAGIV, J
FTIR光谱（在ATR模式）和接触角的测量被用来确定一些代表性的疏油单分子膜的形成的特征时间尺度上产生的极性固体通过自发吸附从有机溶液，并调查mechanis溶剂掺入到这样的组织膜在其形成和随后的释放。低能量表面的吸附，不润湿的散装液体吸附物的更一般的问题，也得到解决，与目前的观察与nonalcoholopholic单层涂层的表面上的溶剂保留。两个两亲物/固体系统和两种饱和烃溶剂被选择用于这项研究，与不同的模式结合到表面和溶剂和两亲物分子之间的不同几何关系的目的提供的例子。离子结合（花生酸/硒化锌）被发现，以产生几乎完整的单层内immersoin时间不超过15秒，而需要几分钟的形成涉及共价结合到表面（正十八烷基三氯硅烷/硅）的完整的单层。溶剂纳入其形成过程中的膜促进溶剂和非极性部分的两亲物之间的几何匹配，如所观察到的差异之间的正十六烷和二环己基在这方面。大多数溶剂通常被挤出膜的内核，并被两亲物取代，完成了后者的紧凑和连续的单层。然而，在一些研究的系统中，发现不同量的溶剂从本体液相分离后保留在外部单层表面的顶部。液体保留在这样的非粘性表面上似乎涉及在膜中的微观缺陷位点处的粘附。它是，最后，表明，高qualtiy，无溶剂的单分子膜可以通过从有机溶液中的吸附，提供溶剂和两亲物之间的几何匹配是避免和两亲物能够不可逆地结合到表面被采用。
FTIR spectroscopy (in the ATR mode) and contact angle measurements are used to determine the characteristic time scales of formation of some representative oleophobic monolayers produced on polar solids by spontaneous adsorption from organic solutions, and to investigate the mechanis of solvent incorporation into such organized films during their formation and its subsequent release. The more general question of adsorption of low-energy surfaces, not wetted by the bulk liquid adsorbate, is also addressed, in connection with the present observations of solvent retention on surfaces coated with nonwettable oleophobic monolayers. Two amphiphile/solid systems and two saturated hydrocarbon solvents were selected for this study, with the purpose of providing examples for different modes of binding to the surface and different geometrical relationships between solvent and amphiphile molecules. Ionic binding (arachidic acid/ZnSe) is found to yield practically complete monolayers within immersoin times not longer than 15 s, whereas several minutes are required for the formation of complete monolayers involving covalent binding to the surface (n-octadecyltrichlorosilane/Si). Solvent incorporation into the films during their formation is facilitated by geometrical matching between the solvent and the non polar portion of the amphiphile, as indicated by the observed differences betweenn-hexadecane and bicyclohexyl in this respect. Most of the solvent is usually squeezed out of the inner core of the film and replaced by amphiphile, with the completion of a compact and continuous monolayer of the latter. However, in some of the studied systems, variable amounts of solvent were found to be retained on top of the outer monolayer surface after its separation from the bulk liquid phase. Liquid retention on such nonwettable surfaces appears to involve adhesion at microscopic defect sites in the film. It is, finally, demonstrated that high qualtiy, solvent-free monolayers may be obtained by adsorption from organic solutions, provided geometrical matching between solvent and amphiphile is avoided and amphiphiles capable of irreversible binding to the surface are employed.