Interpretation of the frequency transients accompanying the submersion of a polymer coated QCM quartz crystal in water

Abstract

10 MHz QCM quartz crystals, uncoated or coated with films of PMMA and/or PEO, were rapidly submerged into aqueous medium. The changes in these crystals’ resonance frequencies were recorded. In all cases after a few seconds crystal’s resonant frequency became constant at a value that depended upon whether the crystal was polished or etched and whether it was coated or uncoated with a polymer film. A blended polymer film composed of PMMA and PEO, when coated on a QCM crystal and then submerged in water showed a rapid frequency increase corresponding to the removal (leaching) of PEO from the film and creating a porous PMMA film whose pores were filled with water. The porosity of the leached film was determined.