ETH-Zürich, Non-Metallic Inorganic Materials, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland.
J Colloid Interface Sci. 2011 Jan 15;353(2):512-8. doi: 10.1016/j.jcis.2010.09.087. Epub 2010 Oct 20.
The hydrophilic character of aluminum oxide surfaces may be altered through coating such surfaces with carboxylic acids. The initially hydrophilic nature of the solid substrate changes towards a less hydrophilic character as the bulk concentration and the chain length of the acids increases. The acids employed in this work (propionic, valeric and enanthic) show a certain affinity to the liquid-gas, solid-liquid and solid-gas interfaces, being the relative adsorption on them competitive. The adsorption behavior of these carboxylic acids is experimentally investigated combining pendant drop tensiometry, contact angle measurements on α-Al(2)O(3) polycrystalline ceramics and adsorption on particles in aqueous suspensions, as a function of the hydrocarbon chain length of the acids and their bulk concentration, at pH equal to the acids' pKa. The hydrophilic character of the coated alumina decreases with the acids concentration upon a certain concentration beyond that, it increases. The minimum of hydrophilicity is reached right before bi-layer arrangements on the adsorption pattern of the acids on the solid substrates take place.
氧化铝表面的亲水性可以通过在表面涂覆羧酸来改变。随着酸的体相浓度和链长的增加，固体基底最初的亲水性会向疏水性转变。在这项工作中使用的酸（丙酸、戊酸和己酸）对气-液、固-液和固-气界面具有一定的亲和力，它们在这些界面上的相对吸附是竞争的。通过悬滴张力计、α-Al(2)O(3)多晶陶瓷上的接触角测量以及在水溶液悬浮液中的颗粒上的吸附，实验研究了这些羧酸的吸附行为，作为羧酸的烃链长度和其体相浓度的函数，在 pH 值等于酸的 pKa 时。在一定浓度之后，涂层氧化铝的亲水性随着酸浓度的增加而降低，在超过一定浓度之后，它会增加。在固体基质上酸的吸附模式发生双层排列之前，亲水性达到最小值。
