Water sorption and cation-exchange selectivity of a perfluorosulfonate ion-exchange polymer

Abstract

may be possible to predict the extent of stacking of purines and pyrimidines in aqueous solutions from retention data. Futher work is now being carried out to examine these postulations.

Modeling the electrical impedance response of ionic polymer transducers

“…From experimental testing it is seen that this prediction counters the physical data that have been measured for the IPT. To address this discrepancy, the results of Yeager et al 41,42 were used to incorporate the temperature dependent variations in the diffusion coefficient d. These results demonstrated that the changes in d outweighed those of T, causing the high frequency impedance of the model to decrease with temperature, a result that agrees with experimental studies. The series of experimental studies conducted in this research also support and validate the proposed model.…”

“…These experiments indicate that the IPT's high frequency resistance actually decreases with a rise in temperature, contrary to the predictions of the model. To account for this discrepancy we revisit our model, incorporating interactions between the ambient temperature T and the diffusion coefficient d. Yeager et al 41,42 conducted several experimental studies that looked at the self-diffusion coefficient of Na + and Cs + through Nafion™ as a function of the ambient temperature. Yeager et al found that the diffusion coefficient had a strong dependence on temperature for each of the counterions considered.…”

“…Some of the initial work performed in this area was conducted by Yeager et al 41,42 who investigated the selfdiffusion properties of Nafion™ as a function solution temperatures. From their experimental work Yeager et al found that the ion mobility declines with temperature, resulting in lower diffusion coefficients at lower temperature scales.…”

“…The impedance model is initially tuned to the baseline response by fixing the temperature to T = 298 K and tuning the diffusion coefficient d and permittivity to match the experimental response. From this initial fit, the temperature is defined by the experimental conditions and the diffusion coefficient is scaled following the relationship prescribed by Yeager et al, 42 and illustrated in Fig. 11͑a͒.…”

Introduction

“…Counterions with large hydration energies increase water uptake, as do low equivalent weights. It is interesting that up to 50% more water is taken up if the materials are boiled in water, compared to room temperature equilibration, and that this increased water is permanently retained after coo ling (15). Increases in water sorption are accompanied by decreases in elec trical resistance and tensile strength, as might be expectedQ2).…”