Physically Motivated Direct Non-Iterative Calculation of Surface Free Energy from Contact Angle Measurements with a Single Wetting Liquid: 1. Derivation and Demonstration of Utility

The estimation of surface free energy (SFE) of a solid is a major issue in (bio)material and (bio)interfacial research. Here we show how combining Neumann and Gerson equations of state allows calculation of SFE and Girifalco-Good parameter (characterizing the interaction between the solid and the wetting liquid) analytically (in closed form) and in physically motivated fashion solely from the surface tension of the wetting liquid and its contact angle with the solid surface. This is significant enhancement compared to the traditional iterative solving of the equations of state or to their empirical fitting by high order polynomials. It is shown that the values of SFE calculated in closed-form fashion are in excellent agreement with the iteratively calculated ones and can open convenient opportunity for direct non-iterative computation of number of surface chemistry parameters.