Measurement of the loss tangent of a thin polymeric film using the atomic force microscope

An atomic force microscope was used to measure the loss tangent, tan δ, of a pressure-sensitive adhesive transfer tape as a function of frequency (0.01 to 10 Hz). For the measurement, the sample was oscillated normal to the surface and the response of the cantilever resting on the polymer surface (as measured via the photodiode) was monitored. Both oscillation amplitude and phase were recorded as a function of frequency. The atomic force microscopy measurement gave the same frequency dependence of tan δ as that measured by a dynamic shear rheometer on a film 20 times thicker. The results demonstrate that the atomic force microscope technique can quantitatively measure rheological properties of soft thin polymeric films.