A critique of the mathematical coherence of acid base interfacial free energy theory

Acid/base theory has, over the last decade or so, been developed to describ e interfacial free energies, or tensions, in wetting theory. An approach pu t forward by van Oss and co-workers, involving van der Waals/Lifshitz and L eu-is electron acceptor/donor contributions to surface/interfacial free ene rgies, has often been employed. The present study considers use of this the ory for evaluating surface data for various polymeric surfaces employing kn own, characterized liquid probes for obtaining contact angle data. Results are analyzed using extended matrix analyses, originally proposed for treati ng the dispersive/polar interpretation of wetting results, and good agreeme nt with literature values is obtained. By "inverting'' the system, i.e., by treating the known solids as probes and rederiving surface data for liquid s, inconsistencies are found to arise. Results for wetting of the same poly mers and mica, using a two-liquid system (n-octane/water), are exploited to attempt to rederive the surface characteristics of water. Again, serious i ncoherence is manifest. Despite the conceptual interest of acid/base theory , clearly the mathematical formulation is presently inadequate. (C) 1999 Ac ademic Press.