Field-cycling NMR relaxometry: the benefit of constructing master curves

Application of proton field‐cyclingNMRrelaxometry for studying translational diffusion in simple liquids and polymer melts

“…This leads to the possibility to construct master curves by shifting the individual NMR susceptibility data χ i ″ ( ω ) collected at different temperatures solely along the ω ‐axis until they overlap, provided that the NMR coupling constant does not significantly change with temperature . The application of FTS, which is well established in the field of rheology or dielectric spectroscopy (DS), is an important tool to effectively extend the still narrow frequency window of FC NMR relaxometry …”

“…However, recent FC NMR results demonstrate that intermolecular relaxation must not be ignored . Instead, it even dominates the total relaxation at low frequencies in systems such as viscous liquids and polymer melts and sometimes also in molecular crystals, here due to vacancy diffusion . Therefore, isotope dilution experiments that are usually performed to separate R 1,intra ( ω ) and R 1,inter ( ω ) are not essential for the determination of the translational diffusion coefficient D .…”

7Li NMR Studies of Short-Range and Long-Range Lithium Ion Dynamics in a Heat-Treated Lithium Iodide-Doped Lithium Thiophosphate Glass Featuring High Ion Conductivity

“…Under such circumstances, it is possible to construct susceptibility master curves by shifting the individual data at various temperatures along the frequency axes. This strategy proved to be useful to extend the dynamic range of FC relaxometry in studies of viscous liquids, − but may also be practicable for disordered electrolytes given the fact that a similar scaling was successfully applied to the frequency-dependent ionic conductivity σ­(ω) of these materials. , Figure shows the master curve obtained from the data of HT-LPSI at various temperatures. Owing to the extended dynamic range, the broadening of the susceptibility peak is particularly evident in the master curve representation.…”

“…This scaling procedure merely presumes the validity of the Arrhenius law; hence it yields valuable information about the shape of g ( E a ) in a wide energy range if succesfull. On the other hand, when the frequency–temperature superposition is obeyed, master curves can be constructed by horizontally shifting the individual susceptibilities at various temperatures. − Here, is used to indicate the shift procedure.…”

Glassy and Polymer Dynamics of Elastomers by 1H-Field-Cycling NMR Relaxometry: Effects of Fillers

“…1 H-field-cycling nuclear magnetic resonance (FC NMR) relaxometry is a very powerful technique for studying dynamic properties of polymers. − This technique measures the dependence of the proton longitudinal relaxation rate ( R 1 (ω) = 1/ T 1 (ω)) on the Larmor frequency ( ν or ω = 2π ν ), also called nuclear magnetic relaxation dispersion (NMRD) from 0.01 to 40 MHz using commercial FC NMR relaxometers; this range can be extended at higher frequencies by measuring R 1 with conventional high-field spectrometers, while frequencies down to 100 Hz can be reached with a home-built FC NMR relaxometer compensating the earth’s magnetic field. − The frequency–temperature superposition (FTS) principle, usually valid for polymers at temperatures above the glass transition ( T g ), , can also be adopted to build master curves joining NMRD data acquired at different temperatures; , with this assumption, dynamics can be investigated over seven to eight frequency decades. Since 1 H longitudinal relaxation arises from the modulation of intrachain and interchain dipole–dipole interactions by reorientations and translations of chain segments, NMRD curves reflect the spectrum of motions of 1 H– 1 H spin pairs in the sample.…”