Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel; The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
Department of Applied Physics, University of Granada, E-18071 Granada, Spain.
J Colloid Interface Sci. 2017 Nov 1;505:692-702. doi: 10.1016/j.jcis.2017.06.036. Epub 2017 Jun 13.
A successful methodology for obtaining hybrid films which allow thermal triggering and continuous, irreversible, control of their hydrophilicity/hydrophobicity nature was developed. Two types of poly(dimethylsiloxane)-silica (PDMS@SiO) films were prepared for that purpose: A hydrophilic film in which the thermal treatment causes an irreversible gradual increase of hydrophobicity; and a hydrophobic film that turns more hydrophilic upon thermal treatment. The opposite directionality of the change is dictated by the film substrate, on which the same hybrid is deposited. In both cases the thermal treatment induced a phase separation which caused the change in hydrophobicity. The magnitude of change in hydrophilicity/hydrophobicity is continuously controllable in both types of films by either the temperature or heating time. The films were characterized before and after heating by a variety of methods, including contact angle (CA) measurements with the sessile drop and the tilting plate methods, and by X-ray photoelectron spectroscopy (XPS) analysis. A thorough kinetic study was carried out, following the progress of the changes in the wettability property of the surfaces. The kinetics analyses proved that the changes in the wettability in all cases are due to phase separation processes, the directionality of which is determined by the treatment of the substrate on which the films are deposited. By monitoring the change of wettability (ΔCA) at various temperatures, an Arrhenius plot was obtained from which the activation energy and Arrhenius pre-exponential factor for the phase separation were derived, corroborating the proposed mechanism. To the best of our knowledge, this is the first use of phase separation behavior of a hybrid film in order to apply irreversible, thermally controllable change of surface wettability, tailored to proceed in opposite directions, and the first kinetic study of such a process.
成功开发了一种获得杂化膜的方法，该方法允许通过热触发和连续、不可逆地控制其亲水性/疏水性。为此目的制备了两种类型的聚二甲基硅氧烷-硅（PDMS@SiO）薄膜：一种亲水性薄膜，其热处理导致疏水性不可逆逐渐增加；以及一种疏水性薄膜，其在热处理时变得更亲水。变化的相反方向由沉积相同杂化膜的基底决定。在这两种情况下，热处理诱导了相分离，从而导致了疏水性的变化。通过温度或加热时间，这两种类型的膜都可以连续控制亲水性/疏水性变化的幅度。通过各种方法对加热前后的薄膜进行了表征，包括接触角（CA）测量，使用固着液滴和倾斜板方法，以及 X 射线光电子能谱（XPS）分析。进行了详细的动力学研究，跟踪表面润湿性变化的进展。动力学分析证明，在所有情况下，润湿性的变化都是由于相分离过程引起的，其方向性由沉积膜的基底的处理决定。通过监测在不同温度下的润湿性变化（ΔCA），获得了阿伦尼乌斯图，从中推导出相分离的活化能和阿伦尼乌斯指数前因子，证实了所提出的机制。据我们所知，这是首次利用杂化膜的相分离行为来应用不可逆、热可控的表面润湿性变化，且可针对相反方向进行定制，并且首次对这种过程进行了动力学研究。
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