Nuclear magnetic relaxation study of poly(propylene oxide)complexed with lithium salt

DSC and solid state NMR characterization of hydroxyethylcellulose/polyether films

“…The correlation times for the cation motion calculated above room temperature (t % 1.0±3.0 Â 10 À9 s) are close to those found for PEO/LiClO 4 ([O/Li] = 8) and for wood pulps 17 and slightly lower than those found for PPO/ LiClO 4 . 13,15 This result indicates that the relative mobility of the cation in the polymer electrolyte HEC/ DPEO/LiClO 4 is comparable to those observed in PEO±Li based polymer electrolytes.…”

“…Similar behaviour was reported for 7 Li T l À1 in PPO±salt ®lms, where the T l À1 maximum was observed at higher temperature compared to analogous PEO. 15 The activation energy calculated from the linear slope of the 1 H T l À1 curve on the low temperature side of the maximum in HEC/DPEO is E % 0.23 eV, which is slightly smaller than the activation energy reported for the amorphous component of pure PEO (E % 0.29 eV). 11 To compare the mobility of the polymer chains of the pure PEO and HEC/DPEO we estimated the correlation time for the chain motion responsible for proton relaxation.…”

“…In Fig 5 it is possible to observe that the relaxation rate reaches the expected maximum at T % 360 K. The 7 Li (I = 32) relaxation rates in solid electrolytes are mainly governed by two mechanisms: (i) quadrupolar relaxation due to coupling between the nuclear quadrupole moment and¯uctuating electric-®eld gradients created in the vicinity of the nucleus, and (ii) the dipole relaxation produced by¯uctuating interactions between nuclear magnetic moments ( Li) and heteronuclear ones between the Li nuclei and the protons of the polymer chain ( 7 Li± 1 H) will be the subject of further studies using NMR decoupling techniques. 13,15,16 The activation energy extracted from the linear slope of 7 Li T l À1 on the low temperature side of the rate maxima (0.25 eV) is of the same order as the value obtained in the polymer complex PEO/LiClO 4 ([O/Li] = 8), E = 0.28 eV. 13 The E values for 7 Li T l relaxation in the LiClO 4 -based solid polymer electrolytes lie in the range 0.2±0.3 eV.…”

Effect of salt concentration on the glass transition temperature and ionic conductivity of poly(ethylene glycol)-polyurethane/LiClO4 complexes

“…So the T g characterizing the segmental mobility in the amorphous phase of a polymer matrix is an important factor in determining the ionic conductivity for polymer electrolytes. [13][14][15] Generally, the T g 's of polymer-salt complexes increase with the addition of salt due to the formation of transient cross-linking between polymer chains via the coordinated interaction between polymer chains and salt. However, at high salt concentrations the decrease in T g (or increase in chain mobility) of complexes may arise from the increased d spacing due to the electrostatic repulsion between anions, and from the decreased interaction between polymer chains and salts owing to the formation of ion pairs and/or higher order ion aggregates.…”

Frequency-swept pulse sequences for 19F heteronuclear spin decoupling in solid-state NMR

“…Another experimentally important situation is the simultaneous presence of 1 H and 19 F. For isolated (or very dilute) H-X-F pairs, offset-robust decoupling on 1 H only may be sufficient for good resolution [63]. For systems that are abundant in both 1 H and 19 F, however, triple resonance experiments need to be performed in order to decouple both nuclides [64][65][66][67][68][69][70][71]. We have also not looked at polymers in this work, as these are conceptually different from rigid organic solids, and are known to respond differently to RF decoupling [70][71][72][73][74][75][76].…”