Ion and polymer mobility in flexible comb polymer electrolytes

Ion conductivity in comb polymer electrolytes was studied both computationally and experimentally. The theoretical methods include Monte Carlo simulations of ion diffusion using a lattice gas model. The experimental methods include the synthesis and characterization of comb polysiloxane polymer electrolytes. Within each approach, polyelectrolytes and polymer-salt complexes were investigated.; Monte Carlo calculations were performed to simulate local harmonic motion of covalently bound anions in polyelectrolyte systems. The simulations show that local motions of the anions increase cation conductivities towards those of analogous polymer-salt complexes while maintaining a cation transference number of one. Increasing the temperature or the dielectric constant of the medium reduces the dependence of cation conductivity on anion motion, while increasing the density of ions in the polymer matrix increases this dependence. The cation conductivity was found to maximize at a lower ion density in polyelectrolytes than in polymer-salt complexes. The ion density at which the cation conductivity reaches a maximum was found to be independent of temperature for systems in which polymer viscosity is independent of temperature.; Novel bifunctionalized comb polysiloxane polyelectrolytes were synthesized where the anion is attached to the end of a highly perfluorinated etheric sidechain. Oligoether sidechains provide amorphous cation coordination sites. Room temperature conductivity of these materials reaches a maximum of 2.5 × 10−6 S/cm at 0.030 Li:EO (Lithium to etheric oxygens). The glass transition temperature at this cation concentration is 203 K. Addition of etheric macrocycles increases conductivity less than it does in similar materials that utilize sterically hindered anions rather than weakly basic anions; thus, ion pairing appears to be reduced in the materials presented here.; Polymer-salt complexes with perfluoroalkyl and oligoether sidechains, or oligoether sidechains alone, were prepared with lithium triflate. The conductivity maximizes at a cation concentration over two times higher than that for the maximum conductivity in analogous polyelectrolytes. The presence of the perfluoroalkyl sidechain decreases conductivity. For all of the polyelectrolytes and polymer-salt complexes described here, the cation concentration at which the conductivity reaches a maximum exhibited a viscosity-based temperature dependence described by the isothermal form of the VTF equation.