Correlating Polymer Viscoelastic Properties with Friction Measures by Scanning Probe Microscopy
Jon A. Hammerschmidt1, Greg Haugstad2, Bahram Moasser1, Richard R. Jones3 and Wayne L. Gladfelter1
1Department of Chemistry,
University of Minnesota, Minneapolis, MN 55455
2Center for Interfacial Engineering, University of Minnesota, 187 Shepherd Labs, Minneapolis, MN 55455
3Sterling Diagnostic Imaging, Staton Road, Brevard, NC 28712
Scanning probe microscopy (SPM) was used to image as well as quantitatively characterize the viscoelastic character of polymer films through the use of frictional force measurements. Measurements on several polymer systems, which vary in morphology, structure, and hydrophilicity, displayed an increase in friction at specific scan velocities. The velocity dependence on friction is attributed to molecular relaxations occurring within the polymer surface caused by energy imparted, over the contact area, by the probe tip. Determination of the frequency of imparted energy suggested a correlation between bulk viscoelastic relaxations, measured by traditional dynamic mechanical and dielectric techniques, and friction measured by SPM. The ability to further image this frictional dissipation, on the tens of nanometers scale, is also demonstrated.