DIRECT MEASUREMENT OF INTERFACIAL INTERACTIONS BETWEEN SEMISPHERICAL LENSES AND FLAT SHEETS OF POLY(DIMETHYLSILOXANE) AND THEIR CHEMICAL DERIVATIVES
DIRECT MEASUREMENT OF INTERFACIAL INTERACTIONS BETWEEN SEMISPHERICAL LENSES AND FLAT SHEETS OF POLY(DIMETHYLSILOXANE) AND THEIR CHEMICAL DERIVATIVES
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DOI：
10.1021/la00053a033
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发表时间：
1991-05-01
期刊：
影响因子：
3.9
通讯作者：
WHITESIDES, GM
中科院分区：
文献类型：
--
作者：
CHAUDHURY, MK;WHITESIDES, GM
在空气中以及在水和甲醇的混合物中测量弹性体聚（二甲基硅氧烷）（PDMS）的小（1-2 mm）半球形透镜与该材料的平板接触时产生的变形。 在空气中的测量以两种方式进行：作为外部负载的函数，以及在零负载下，但在透镜的尺寸变化。 在液体中的测量在零负荷下进行，并且改变液体混合物的组成。 利用约翰逊、肯德尔和罗伯茨的理论对这些实验数据进行了分析，得到了PDMS表面在空气和液体介质中的粘附功。 在水和甲醇的混合物中，随着甲醇浓度的增加，PDMS表面之间的相互作用强度降低。 即使在纯甲醇中也存在小的相互作用。 用Young方程分析了由这些测量得到的PDMS-液体界面的界面自由能（γ-sl），以及这些液体在PDMS上的接触角。 该分析提供了聚合物的表面自由能（γ-sv）的估计值，其与从在空气中进行的测量获得的值和使用Good-Girifalco-Fowkes方程从PDMS上的非极性液体的接触角的分析估计的值两者一致。 本研究还开发了化学改性PDMS表面的方法，从而控制其性能。 的化学衍生的聚（二甲基硅氧烷），在透镜和平板的形式，进行类似于用于未改性的PDMS的负载变形测量。 这些功能化的PDMS表面在接触变形中表现出滞后，而未改性的PDMS没有检测到滞后。 这种滞后现象的起源目前尚不清楚。 在固-固界面处的滞后现象的观察与理解对这些表面的粘附有关。
The deformations resulting on contacting small (1-2 mm) semispherical lenses of elastomeric poly-(dimethylsiloxane) (PDMS) with the flat sheets of this material were measured in air and in mixtures of water and methanol. The measurements in air were carried out in two ways: as a function of external loads, and under zero load but with variations in the sizes of the lenses. The measurements in liquids were carried out under zero load and varied the composition of the liquid mixtures. These experimental data were analyzed by using a theory of Johnson, Kendall and Roberts to obtain the works of adhesion between PDMS surfaces in the air and liquid media. The strength of interaction between PDMS surfaces decreased in mixtures of water and methanol as the concentration of methanol increased. A small interaction persisted even in pure methanol. The interfacial free energies (gamma-sl) of the PDMS-liquid interfaces obtained from these measurements, together with the contact angles of these liquids on PDMS, were analyzed by using Young's equation. This analysis provided an estimate of the surface free energy of the polymer (gamma-sv) that was consistent both with the value obtained from measurements made in air and with the value estimated from the analysis of the contact angles of nonpolar liquids on PDMS using the Good-Girifalco-Fowkes equation. This research also developed ways to modify the surface of PDMS chemically and thus to control its properties. The chemically derivatized poly(dimethysiloxanes), in the form of lenses and flat sheets, were subjected to load-deformation measurements similar to those used for unmodified PDMS. These functionalized PDMS surfaces exhibited hysteresis in contact deformations, whereas no hysteresis was detected for unmodified PDMS. The origin of this hysteresis is not clear at present. The observation of hysteresis at solid-solid interfaces is relevant to understanding adhesion to these surfaces.