title: Polymer dynamics near the surface and in the bulk of poly(tetrafluoroethylene) probed by zero-field muon-spin-relaxation spectroscopy.
abstract: The results of many experiments on polymers such as polystyrene indicate that the polymer chains near a free surface exhibit enhanced dynamics when compared with the bulk. We have investigated whether this is the case for poly(tetrafluoroethylene) (PTFE) by using zero-field muon-spin-relaxation spectroscopy to characterize a local probe, the F-Mu(+)-F state, which forms when spin-polarized positive muons are implanted in PTFE. Low-energy muons (implantation energies from 2.0 to 23.0 keV) were used to study the F-Mu(+)-F state between ∼ 23 and 191 nm from the free surface of PTFE. Measurements were also made with surface muons (4.1 MeV) where the mean implantation depth is on the order of ∼ 0.6 mm. The relaxation rate of the F-Mu(+)-F state up to ∼ 150 K was found to be significantly higher for muons implanted at 2.0 keV than for higher implantation energies, which suggests that the polymer chains in a region on the order of a few tens of nanometers from the free surface are more mobile than those in the bulk.
authors.affiliation: Centre for Molecular and Materials Science, TRIUMF, Vancouver, British Columbia, Canada V6T 2A3 and Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Iain
authors.initials: I
authors.lastname: McKenzie
authors.affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Zaher
authors.initials: Z
authors.lastname: Salman
authors.affiliation: School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, United Kingdom.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Giblin
authors.affiliation: Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Yun Yu
authors.initials: YY
authors.lastname: Han
authors.affiliation: Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Leach
authors.affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Elvezio
authors.initials: E
authors.lastname: Morenzoni
authors.affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Prokscha
authors.affiliation: Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Suter
mesh_terms: D003198:Computer Simulation; D058266:Dielectric Spectroscopy / Q000379:methods*; D008422:Materials Testing; D008651:Mesons; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry; D011138:Polytetrafluoroethylene / Q000737:chemistry*; D013113:Spin Labels; D013499:Surface Properties
chemical_list: D011108:Polymers; D013113:Spin Labels; D011138:Polytetrafluoroethylene