Investigations of the high-frequency dynamic properties of polymeric systems with quartz crystal resonators

Opportunities arising from the use of the rheometric quartz crystal microbalance (RheoQCM) as a fixed frequency rheometer operating at 15 MHz are discussed. The technique requires the use of films in a specified thickness range that depends on the mechanical properties of the material of interest. A regime map quantifying the appropriate thicknesses is developed, based on the properties of a highly crosslinked epoxy sample that is representative of a broad class of polymeric materials. Relative errors in the measured film properties are typically in the range of several percent or less and are minimized by using a power law model to relate the rheological properties at two different resonant harmonics of the quartz crystal. Application of the RheoQCM technique is illustrated by measuring the temperature- and molecular weight-dependent properties of polystyrene and poly(methyl methacrylate) in the vicinity of the glass transition.