Investigating the compatibility of PEEK polymer for the fabrication of sample cells for use in muon spin spectroscopy

[摘要] Polyether ether ketone (PEEK) is a thermoplastic polymer with a wide range of applications due to its chemical inertness and thermal stability, and for these reasons sample cells for gas and liquid phase μSR have been constructed from PEEK. Muon levelcrossing resonance (μLCR) studies of PEEK revealed a broad, strong μLCR signal that, we hypothesize, is due to multiple overlapping resonances from the various muonium (Mu) adducts of PEEK. To investigate this, two monomer units from PEEK (4,4'-dihydroxybenzophenone and para-dimethoxybenzene) were studied in solution using transverse-field muon spin rotation (TF-μSR) and μLCR. Two different muoniated radicals were formed by Mu addition to 4,4/- dihydroxybenzophenone and one radical was formed in para-dimethoxybenzene. The μSR spectra were assigned by comparing the experimentally measured muon and proton hyperfine coupling constants with values calculated for the possible structures using Gaussian-09 software with the B3LYP functional and 6-31G basis set. Good agreement was found for cyclohexadienyl- type radicals formed by Mu addition to the benzene rings of the monomer units. We can also infer that these radicals are being formed in PEEK, and based on this we conclude that sample cells made of PEEK are unsuitable for many types of μSR experiment.

[发布机构] Department of Chemistry, Simon Fraser University, Burnaby; BC; V5A 1S6, Canada^1;Centre for Molecular and Materials Science, TRIUMF, Vancouver; BC; V6T 2A3, Canada^2;ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon; OX11 0QX, United Kingdom^3

[关键词] Chemical inertness;Muon spin rotation;Muon spin spectroscopy;Overlapping resonances;Polyether ether ketones (PEEK);Proton hyperfine couplings;Thermoplastic polymer;Transverse field