Frequency Dependence of Dynamic Properties of Polyethylene Glycol Molecules on Oscillating Solid–Liquid Interface

Abstract

Frequency dependence of the resonant length of polyethylene glycol (PEG) on a solid–liquid interface oscillating at megahertz was studied by a quartz crystal microbalance (QCM). A QCM frequency and a number-average molecular weight (Mn) of PEG were changed systematically. This attempt revealed that, in all of the frequencies used, the series-resonant frequency shift, ΔF, of the QCM against the square root of the density-viscosity product of the PEG solutions was linear and had intercept. In addition, the systematical analysis made it clear that the ΔF slope was explainable by the Debye process, and the ΔF intercept became constant above the resonant length. These results led to the novel findings that the resonant length of the PEG molecules formed by physisorption was equal to that in the region of the viscous penetration depth and that the relationship between resonant length and QCM frequency was able to be explained by τ ∝ Mnν, where τ is a relaxation time of molecule and ν is a constant. In particula...