Correlation of nanowear patterns to viscoelastic response in a thin polystyrene melt

The response of a thin-film polystyrene melt to a raster-scanned scanning f orce microscope tip was investigated. At high temperatures the scanning pro cess induced intricate pattern formation whose quantitative characteristics were compared at different temperatures and scan rates. The dependence of the patterns on temperature and scan rate was consistent with time-temperat ure superposition as described by the Williams-Landel-Ferry (WLF) equation. WLF analysis implies an increased glass transition temperature derived fro m elevated pressure beneath the tip. The latter provides an estimate of the radius of the affected film region near the tip.