ABSTRACT
Referring to eq. IV-17 and turning to the examples given in Table IV-2, the hydrophilic example (bottom row) describes the free energy of polar (AB) adhesion between material, 1 (a monopolar, electron-donating hydrophilic molecule) and water, w, and is shown as term V: + ⋅4 1( )γ γ w . In eq. IV-17 (repeated at the top of Table IV-2), term V has a positive value and therefore indicates a repulsive contribution. It is proportional to the free energy of hydration of entity 1 (cf. the third right hand term of eq. IV-18, which is the relevant term for an electron-donating monopolar entity 1), which at +127.8 mJ/m2 amply suffi ces to overcome the always-present hydrophobic attraction (term III) of –102 mJ/m2, leaving a net hydrophilic (AB) repulsion of +20.3 mJ/m2 (after also deducting a small van der Waals attraction). Being solely caused by the hydration of hydrophilic surfaces, the term “hydration forces” for its driving force is therefore entirely appropriate.
