Optimizing the design of polyelectrolytes using Monte Carlo simulations

Monte Carlo calculations were performed to simulate ion diffusion through p olymer matrices. The parameters can be chosen so that a broad range of poly mer electrolytes can be modeled. The focus of the present study is optimizi ng conductivity in polyelectrolytes. A dynamic bond percolation model was e xtended to include local harmonic motion of covalently bound anions in poly electrolyte systems. Local motion of these anions facilitates cation escape from potential wells, and thus, improves overall conductivity, while maint aining a cation transference number of one. Simulations,how that ion correl ation has a significant effect on diffusion. Increasing the temperature or the dielectric constant of the medium reduces the dependence on ion interac tion. while increasing the density of ions in the polymer matrix increases the dependence. At high densities, physical blocking significantly interfer es with diffusion at all temperatures. The cation conductivity was found to maximize at a lower density in polyelectrolytes than in polymer-salt compl exes. (C) 2001 The Electrochemical Society.