Molecular motion of tri-n-butyl ammonium picrate + polypropylene glycol solutions as studied by dielectric and Kerr-effect techniques

Abstract

Dielectric and dynamic Kerr-effect studies have been made over the equivalent frequency range 10^–2 to 10⁵ Hz for solutions of tri-n-butyl ammonium picrate in polypropylene glycol as solvent. Three molecular weights of solvent, 400, 1025 and 2025, were used. Two dielectric processes were observed for all solutions and are due to solvent (high frequency process) and solute (low frequency process). Only the solute process was observed in the dynamic Kerr-effect experiments since these solvents have rather small Kerr-constants. A comparison of the data from both techniques indicate: (i) that the solute motions are essentially uncoupled in time-scale from the solvent motions, (ii) that solvent motions occur by the well-known structural-relaxation mechanism and (iii) that the solute motions resemble those for small-angle rotational diffusion.