Direct Observation of Surface Morphology and Surface Viscoelastic Properties of Polymeric Solids Based on Scanning Force Microscopy.

Abstract

Scanning force microscopy (SFM) was applied for the studies of the surface morphology and viscoelastic properties of polymeric solids. Surface morphology of polyethylene (PE) single crystals was studied by atomic force microscopy (AFM) and friction force microscopy (FFM). The AFM observation revealed the lozenge-shaped single crystals of PE with ridgy structure. The FFM experiment revealed that the frictional force on the same sector was dependent on the scanning direction against {110} for the PE single crystal prepared from fractionated HDPE with Mw=10k. On the other hand, the frictional force did not strongly depend on the scanning direction for the PE single crystal prepared from unfractionated PE with Mw of 520k. The FFM results revealed the regularity of chain folding on PE single crystal surface. Nano-mechanical properties of phase-separated polymer surface were imaged by scanning viscoelasticity microscopy (SVM), which has been developed by the authors. Images of dynamic viscoelasticity for both the immobilized (octadecyltrichlorosilane/fluoroalkylsilane) mixed monolayer and [polystyrene(PS)/poly(vinyl methyl ether) (PVME)] blend ultrathin film were presented. SVM could reveal the difference in dynamic viscoelasticity on the phase-separated polymer surface with a nanometer scale resolution.