Scan-Induced Patterning in Glassy Polymer Films: Using Scanning Force Microscopy to Study Plastic Deformation at the Nanometer Length Scale
Ronald H. Schmidt,1 Greg Haugstad,*2 and Wayne L. Gladfelter*1
1Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, and 2IT Characterization Facility, University of Minnesota, 100 Union Street SE, Minneapolis, Minnesota 55455
Environmental scanning force microscopy was used to investigate the temperature and rate dependence of the scan-induced formation of bundles in a thin polystyrene film. The spacing of the bundles increased monotonically with temperature, and this increase exhibited a cusp near the bulk glass transition temperature of polystyrene. The roughness of the patterns (which is proportional to the wave amplitude) and the rate of roughening with repeated raster scans both exhibited a maximum value at slightly higher temperatures. Thus, the temperature dependencies of the wavelength and the surface roughness are qualitatively and quantitatively different. An Arrhenius model was used to describe the temperature and rate dependencies of the relaxations. The activation energies derived from these two independent analyses were found to be very similar to the value for the R relaxation in bulk samples.