MOLECULAR-DYNAMICS AND INFRARED-SPECTRA OF NASCN DISSOLVED IN THE SOLVENT MACROCYCLE 15-CROWN-5 AND POLYETHYLENE OXIDE DIMETHYL ETHER-250

NaSCN dissolved in liquid 15-crown-5 (15C5) at 25 degrees C has been s tudied by audio frequency electrical conductivity and by infrared spec troscopy (''CN stretch mode'' or antisymmetrical stretch of the SCN- a nion). Analysis of the conductance data by the Fuoss-Onsager theory (c oncentration range (6-80) x 10(-4) M) indicates that the electrolyte i s unassociated. This conclusion is corroborated by infrared spectra de scribed by a single Gaussian-Lorentzian band centered at similar to 20 58 cm(-1) for electrolyte concentrations vp to similar to 0.1 M. The m olecular dynamics of the above systems have been studied by ultrasonic and UHF relaxation spectroscopy over the similar to 1 to 600 MHz freq uency range. At 25 degrees C the solute relaxation centered at similar to 10 MHz is that of a pseudo-first-order kinetic process. It is attr ibuted to a Na+-15C5 interaction. The microwave dielectric spectrum of a 15CS-NaSCN solution in the frequency range 0.3-130 GHz is described by a Cole-Davidson distribution function, as was feasible for the mic rowave dielectric spectrum of the 15C5 solvent determined previously. The molar refraction R calculated from sodium doublet refractive indic es has also been determined. The above experiments have been repeated with NaSCN dissolved in the acyclic polyethylene oxide dimethyl ether polymer of average molar mass 250 g mol(-1) (PEG-250). The electrolyte appears to be heavily associated in the acyclic polymer in contrast t o the case of 15C5 solvent. Thus, 15C5 may find use as a solvent in el ectrolyte-polymer batteries. Because of the practical importance of so me Li+ salts in batteries, some of the above investigation has been re peated for LiSCN in 15C5 and compared with the NaSCN in 15C5 results.