Case of Temperature-Dependent van der Waals Forces

In most situations, the Hamaker constant A is virtually independent of temperature. There are some special cases, however, when A does become temperature-dependent. 

As one approaches the critical point for the liquid/vapor pair, the difference OiL decreases markedly and A becomes small. 

With a low-energy surface (a small), it is possible to have as low temperature. Upon heating, however, the density of the liquid decreases, which means that 6ll decreases as well. It then becomes possible to end up with 6ll In other words, the constant A changes sign 

We now study in greater detail the surface treatments discussed in section 1.2.3.2. The standard way to apply a surface treatment is to deposit an antagonistic layer serving as an intermediary between the solid and the liquid so as to alter and possibly even reverse the wettability characteristics of the solid. 

FIGURE 4.5. Energy P(e) for (a) bare glass (total wetting) and (b) silanized glass (partial wetting). 

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