FTIR studies of chitosan acetate based polymer electrolytes

Polymer electrolytes have been a focus of the scientific community for a quarter century. They extend the realm of traditional solid-state ionics from hard materials to include soft materials and, in doing so, pose issues both fundamental (e.g., how are structure and transport defined in a concentrated electrolyte with an immobile solvent?) and technological (e.g., how can polymer ionics be used to construct electrochemical devices such as sensors, batteries, and fuel cells?)

Polymer Electrolytes: Ionic Transport Mechanisms and Relaxation Coupling

The symmetric stretch modes for the anions in poly(propylene glycol) (PPG) complexed with NaCF3SO3 and LiClO4 at an ether oxygen of alkali metal cation ratio of 16:1 have been studied as a function of the molecular weight of PPG and temperature using Raman spectroscopy. The splitting of these modes has been analyzed in terms of ‘‘free’’ anions and ion pairs. We have observed that the number of ion pairs increases with increasing molecular weight and increasing temperature. The effect is greater in the PPG–NaCF3SO3 complex than in the PPG–LiClO4 complex. We have found a simple exponential relationship for the number of free anions in a master‐plot representation using a shift factor T* which increases with increasing molecular weight. These results are discussed in terms of the entropy and energetics of polymer–salt systems.

Ion pairing effects in poly(propylene glycol)–salt complexes as a function of molecular weight and temperature: A Raman scattering study using NaCF3SO3 and LiClO4

Molecular dynamics (MD) simulations of PEO/LiI melts at 363 and 450 K for the ether oxygen (EO)/LiI compositions 48:1, 15:1, and 5:1 have been performed. An explicit atom quantum-chemistry-based force field developed in our previous work was used. The Li+ cation environment from our MD simulations was found to be in good agreement with neutron diffraction isotopic substitution (NDIS) experiments performed on the EO/Li = 5:1 system. Cation complexation was found to be strongly temperature dependent. The Li+ cations have a tendency to be coordinated by six or more contiguous EO from a single chain at the lower temperature (363 K), but as temperature increases, coordination by shorter contiguous ether oxygen atom sequences becomes increasingly probable. The number of “free” ions was found to decrease with increasing temperature, consistent with results from Raman spectroscopy experiments on similar polymer electrolyte systems. The strong temperature dependence of the cation environment indicates the importan...

Molecular Dynamics Simulations of Poly(ethylene oxide)/LiI Melts. 1. Structural and Conformational Properties

Raman scattering measurements have been carried out on poly(propylene oxide) complexed with NaCF3SO3 salt of concentration O:M=30:1 (where O:M is the PO:Na ratio) over a temperature range of 186–360 K in order to study ion–ion associations of the dopant salt and their temperature dependence. Splitting of the symmetric stretching mode of the CF3SO−3 anion into a double band was observed and attributed to the existence of different environments of the anions. A two‐component band analysis led to the identification of coexisting dissociated free ions and ion pairs, suggested to be in contact. Below the glass transition temperature, Tg, the intensity of the mode corresponding to the free ions was more or less constant with temperature; the amount of free ions in the glassy state was found to be about 84% of the total salt concentration. Above Tg the amount of dissociated free ions decreased rapidly with temperature in an Arrhenius‐type behavior. The resulting reduction of the number of charge carriers has lit...

Raman spectroscopic study of ion–ion interaction and its temperature dependence in a poly(propylene‐oxide)‐based NaCF3SO3 –polymer electrolyte

Ion pairing in polymer electrolytes; A comparative Raman study of NaCF3SO3 complexed in poly(propylene-glycol) and dissolved in acetonitrile

In the present study of ion conducting polymers we demonstrate how light scattering can be used to obtain information about the elastic properties and the local intrachain mobility, which are essential characteristics of a high performance polymeric solid electrolyte. Brillouin scattering has been applied in studies of sodium triflate (NaCF3SO3)–poly(propylene glycol) (PPG) complexes of concentrations O:M=5:1, 8:1, and 16:1, where O:M is the backbone oxygen to sodium ratio. From the spectra sound velocity and absorption data were obtained. The acoustic data reveal structural relaxation processes associated with local translational (and orientational) intrachain motions of the polymer segments. The characteristic relaxations times τ were determined and found to be strongly dependent on the concentration of the dopant salt. This is because the dissociated ions act both as crosslinks betwen polymer chain segments and as ‘‘free’’ ions available for conduction. Therefore, as the concentration of dissociated io...

J. Sandahl

Papers

Ion pairing in polymer electrolytes; A comparative Raman study of NaCF3SO3 complexed in poly(propylene-glycol) and dissolved in acetonitrile

Elastic and dynamic properties of polymer electrolytes: A Brillouin scattering study of poly(propylene glycol)–NaCF3SO3 complexes

Sound velocity, local intrachain flexibility and structural relaxation in MSCN-poly(propylene glycol) complexes; A Brillouin scattering study