Free energy between solid bodies

We now focus on the line x = 1/2 (0 line). The most striking feature is that in the free energy expansion of eq. (III.9) or eq. (IV.30) the term disappears. There remain, however, higher order terms and mainly (for not too large a 4>) the term. This situation is depicted in Fig. IV.9, where the solid lines represent polymer chains the dotted line represents a pair interaction (between two monomers which are very close) and is associated with the term. The dot with three arms represents a three-body interaction (i.e. the term). 

Let us assume at this point that the interfacial free energy, a, is the principal parameter responsible for the characterization of the interactions between the solid and the medium determined by their chemical composition. The following simplification allows one to obtain the relationship between the strength and the surface free energy of a solid body with a defect in the form of a microcrack. 

To discuss the adhesion between a liquid and a solid, consider separate cylindrical volumes of liquid (L) and solid (S) with unit cross-sectional areas (Fig. 4). If each of these bodies is cleaved in half, the work required in each case is equal to the difference in free energies before and after cleavage. This may be expressed as ... 

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