A previous paper by our group concluded that to distinguish between the wettability of different particles, heat of immersion is the best method as opposed to the Washburn or sessile drop method. In this paper, heats of immersion of three different particles with three different wettabilities are measured at different temperatures to examine one critical assumption concerning the temperature dependence of the heat of immersion. In addition, surfactants are added to the water and the effect of surfactant concentration on the heat of wetting is measured. One particularly noteworthy aspect of the current study is that some measurements were made at pressures higher than atmospheric with no more difficulty than measurements made at atmospheric pressure.

The previous paper showed that, for certain particles, the relationship used by us and others between heat of wetting and contact angle gave impossible values for certain surfaces. In this thesis, the derivation of that expression is re-examined and certain assumptions are highlighted. Because of issues with the assumptions, we conclude that using heat of immersion to quantify wetting is perfectly appropriate, but without measurement of the values of liquid-solid interfacial energy with temperature, conversion to the contact angle is likely not appropriate. Keywords – nanoparticles, wettability, silica, heat of immersion, contact angle