CONTACT ANGLES AT THE SOLID-WATER INTERFACE

The study of polymer-water interfaces by contact angle methods can be accomplished directly at the polymer-water interface. Using two water-immiscible liquids or a liquid and a vapor, one can deduce the dispersion and polar components of the hydrated solid surface free energy and the solid-water interfacial free energy. The theory is presented and a numerical analysis procedure is developed to solve the equations in the general case. The special case of n-octane and air is also presented. Data and results are given for poly(hydroxyethyl methacrylate-methoxyethyl methacrylate) copolymers of varying composition and equilibrium water contents. The results show that the hydrophilic component dominates the polymer-water interfacial properties, even at relatively low hydrophilic component compositions. The method presented should be useful for the study of polymer-water interfaces, particularly for hydratable or mobile polymers which can reorient to equilibrate differently with a water environment than with the air or vapor environment commonly used in contact angle studies. © 1979 Academic Press, Inc.