6533b82dfe1ef96bd1291dac

RESEARCH PRODUCT

Anisotropic Stick-slip friction of highly oriented thin films of poly(tetrafluoroethylene) at the molecular level

D. TrifonovaH. LeistH. LeistS. ForsterGyula J. VancsoG. Liu

subject

chemistry.chemical_classificationPressingMaterials scienceMechanical EngineeringMuscoviteNanotechnologySurfaces and InterfacesPolymerSlip (materials science)engineering.materialSurfaces Coatings and Filmschemistry.chemical_compoundchemistryMechanics of MaterialsMicroscopyengineeringTetrafluoroethyleneComposite materialThin filmAnisotropy

description

Lateral force microscopy (LFM) studies of poly(tetrafluoroethylene) (PTFE) films with molecular resolution are reported. Thin PTFE layers with a high degree of orientation were obtained by pressing and sliding a block of polymer on a clean, heated muscovite mica substrate. LFM nanographs obtained on these films by scanning at directions between ca. 40 and 90° with respect to the film orientation direction, i.e. with respect to the direction of the polymer chains, showed a “stick-slip” type frictional motion of the LFM probe tip at the molecular level. The friction force observed at constant load decreased with decreasing scan angles. Chain-chain packing distances obtained by LFM and contact-mode atomic force microscopy were the same to within the experimental error and had a value of 5.8 A. Dual-mode contact AFM/LFM imaging was also performed by scanning in the chain direction. Here LFM nanographs showed no distinct “stick-slip” phenomenon. The contact mode AFM images, however, exhibited clear molecular resolution with the expected chain-chain periodicity. The disappearance of the “stick” component in LFM scans performed in the chain direction was attributed to the smooth surface of PTFE on the molecular scale.

yearjournalcountryeditionlanguage
1996-10-01Tribology letters
10.1007/bf00173129https://doi.org/10.1007/bf00173129