Temperature Dependence of Contact Angle

The surface tension of liquids, yy, decreases with increasing temperature, and if we assume that the surface tension term related to a solid is much less affected by a temperature 

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Since this method is broadly useful, and since it has proved to be particularly suitable for measuring the temperature dependence of contact angles (4.25-291, we describe the apparatus in detail, including the temperature control system. The essential parts of the equipment (Fig. 4) are the following ... 

FIG. 4 Apparatus for measuring the temperature dependence of contact angles, based on the optical measurement of the capillary rise of the liquid at a vertical plate. 

A rather different procedure lies in a testing of the temperature dependence of contact angle. From the second law equations, (9fV0T)p = - and F = - TS, one finds, in combination with... 

With respect to purely thermodynamic tests of the Young and Dupre equation, a study of the temperature dependence of contact angles, combined with calorimetric and surface area measurements, offers some promise. This would provide a classical second law test. 

TEMPERATURE DEPENDENCE OF CONTACT ANGLES OF LIQUIDS ON POLYMERIC SOLIDS. 

Jones, J. B., and Adamson, A. W. 1968. Temperature dependence of contact angle and of interfacial free energies in the naphthalene-water-air system. J. Phys. Chem. 72 646. 

Petke, D., and Ray, B. R. 1969. Temperature dependence of contact angles of liquids on polymeric sohds. J. Colloid Interface Sci. 31 216. 

Heat of immersion, one of these indirect approaches, is a measure of the wettability of the powder immersed into a liquid (58). It is defined as the heat evolved per square centimetre of powder immersed in a liquid. The heat of immersion is a measurable quantity and can be related, in principle, to contact angles. However, it is not only related to the contact angle, but also to the temperature-dependence of the contact angle. In view of this complication, this method is not generally effective because the temperature-dependence of contact angles will not normally be known unless the contact angle itself is already known. Therefore, only relative and semi-quantitative information is provided from this method. 

In the third section, two additional matrix materials are Introduced, benzophenone and blbenzyl. However, this is not done through measurements of the temperature dependence of contact angles as in the first section above, but through the solidification front technique Itself, using particles of known surface tension as probes. 

Figure 1.7. Dependence of contact angle on the metal droplet radius for Pb on vitreous carbon at a temperature close to the melting point of Pb. The horizontal line identifies the macroscopic contact angle. Data from work reported in (Chizhik et al. 1985).

Volyak LD, Stepanov VG, Tarlakov YV (1975) Temperature dependence of the angle of contact of water and water-d2 on quartz and sapphire. Zh Fiz Khim 49 2931-3133 Walker DS, Moore FG, Richmond GL (2007) Vibrational sum frequency spectroscopy and molecular dynamics simulations of the carbon tetrachloride-water and 1,2-dichloromethane-water interfaces. J Phys Chem C 111 6103-6112... 

Figure 6.1 Temperature-dependent water contact angle for surfaces grafted with PNiPAAm (filled square) and with copolymers with an increasing molar content of n-butyl methacrylate (open circle, open square, filled circle).

Early transport measurements on individual multi-wall nanotubes [187] were carried out on nanotubes with too large an outer diameter to be sensitive to ID quantum effects. Furthermore, contributions from the inner constituent shells which may not make electrical contact with the current source complicate the interpretation of the transport results, and in some cases the measurements were not made at low enough temperatures to be sensitive to 1D effects. Early transport measurements on multiple ropes (arrays) of single-wall armchair carbon nanotubes [188], addressed general issues such as the temperature dependence of the resistivity of nanotube bundles, each containing many single-wall nanotubes with a distribution of diameters d/ and chiral angles 6. Their results confirmed the theoretical prediction that many of the individual nanotubes are metallic. 

Fig. 8 Ambient temperature dependence of the change in water contact angle on a highly hydrophilic HO2 surface in the dark...

The accuracy and reproducibility of this method is such that, for example, the solid-solid phase transition of cholesterol acetate at 40 C has been detected by means of the temperature dependence of the contact angle of water 26], The discontinuity in the contact angle curve was about 0.3 of arc. For water on siliconized glass plates, the deviations of individual points in the plot of contact angle versus temperature were found to be about 0.1 128). in good agreement with the error limits estimated above. 

The case of contact angles of solutions is more difficult, but offers more scope for thermodynamic predictions that would be in principle verifiable. In addition to temperature-dependence studies, it is now possible to make independent determinations of changes in y yo and y with solution composition and hence of the expected changes in contact angle. 

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