K.J. Adamic

Ionic conductivity in solid, crosslinked dimethylsiloxane‐ethylene oxide copolymer networks containing sodium

The preparation of an ion‐conducting elastomeric solid based on a dimethylsiloxane‐ethylene oxide copolymer complexed with a sodium salt is described. 23Na nuclear magnetic resonance measurements reveal the presence of both bound and mobile sodium species throughout the temperature range −120 to 100 °C. Electrical conductivity measurements over a similar temperature range are found to be consistent with the configurational entropy model for transport, with a T0 parameter about 50 °C below the ‘‘central’’ glass transition temperature Tg.

NMR, DSC and electrical conductivity studies of MEEP complexed with NaCF3SO3

Abstract 23 Na NMR, electrical conductivity, and DSC studies have been carried out on MEEP complexed with NaCF 3 SO 3 . All results are similar to those for other amorphous ion conducting polymers. Specifically, the NMR spectrum associated with mobile Na + ions exhibits motional narrowing above the glass transition temperature, and activation energies deduced from both T 1 and linewidth measurements reflect localized motion of the actions. The electrical conductivity exhibits the usual non-Arrhenius behavior. However, using previous data for PDMS-EO complexes, it is shown that the VTF or WLF equations are only approximate as the parameters depend upon the temperature range. This sheds light on several discrepancies in the literature.

Complex impedance and multifrequency 23Na NMR study of poly (propylene oxide) complexed with NaB (C6H5)4

Abstract Complex impedance and multifrequency 23 Na nuclear magnetic resnoance (NMR) measurements on a poly (propylene oxide): sodium tetraphenylborate, PPO 8 NaB(C 6 H 5 ) 4 , solid polymer electrolyte, with a composition of eight ether oxygens per sodium, are reported. The NMR linewidths are found to be second-order quadrupole broadened, thus indicating low site-symmetry for the Na + ions. The title compound exhibits some interesting differences in properties compared to other PPO-Na salt complexes, including an anomalously low value of the stretched exponential parameter s se (obtained in fits to electric modulus data), an unusually high glass transition temperature ( T g =306 K), and sub- T g line narrowing of lower frequency 23 Na resonances. This last phenomenon is attributed to strong interaction between the Na + ions and their large [B(C 6 H 5 ) 4 ] - counterions caused by the localization of the [B(C 6 H 5 ) 4 ] - anions in weak interactions with the polymer chains which, in turn, leads to the elevated glass transition temperatures.

High Pressure Conductivity and NMR Investigation of Siloxane-Based Polymer Electrolytes

Abstract Variable temperature and pressure conductivity and 23Na nuclear magnetic resonance (NMR) measurements of several siloxane-based polymers complexed with NaCF3SO3 are reported. The conductivity exhibits V.T.F. behavior of the type commonly observed in amorphous polymer electrolytes, and activation volumes (29.9 cm3/mol at 313K for one sample) typical of these materials. The NMR linewidths associated with mobile Na+ ions exhibit motional narrowing above Tg in a manner similar to other Na-polymer electrolytes. The pressure dependence of the 23Na linewidth is consistent with a 10-15 K/kbar increase in Tg.

Conductivity, DSC, FTIR, and NMR studies of poly(vinyl acetate) complexed with Alkali metal salts

Abstract Electrical conductivity, differential scanning calorimetry, and nuclear magnetic resonance studies have been carried out on poly(vinyl acetate) after the addition of various lithium salts. In the case of lithium triflate, the resultant polymer is poly(vinyl alcohol). Relatively large conductivites are observed after initial preparation, but these decrease with time when the material is in vacuum. The conductivities exhibit approximately Arrhenius behavior and increases with salt concentration. In addition to the conductivity, NMR, FTIR, and DSC results are presented. All results are interpreted in terms of the model of Wissbrun and Hannon where water is the solvating species.

Nmr Studies of Polymer Electrolytes

The results of several investigations of solvent-free polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted by the authors and other groups are reviewed. 23 Na NMR spectra of a wide variety of amorphous polymer electrolytes are characteristic of the second-order quadrupole broadened central ± 1/2 transition with a distribution of quadrupole couplings. The temperature dependence of the linewidth is similar across a wide range of materials, and highlights the importance of polymer segmental motions above the glass transition temperature to ion mobility. Strong cation-anion interactions in poly(propylene oxide) complexes are indicated by measurements of mobile ion concentrations and, in some cases, the observation of salt precipitation at elevated temperature.