Dynamic properties of the polyethylene glycol molecules on the oscillating solid-liquid interface.

The dynamic properties of polyethylene glycol (PEG) molecules on the solid-liquid interface oscillating at MHz were investigated using the quartz crystal microbalance (QCM). The number-average molecular weights (M(n)) of the PEG molecules were systematically varied over 4 orders of magnitude. This study makes it clear that the series-resonant frequency shift, ΔF, of the QCM against the square root of the density-viscosity product of the PEG solution is linear and has the intercept. Moreover, systematical analysis reveals that the ΔF slope rapidly decreases with M(n) and that the ΔF intercept becomes constant above 4.0×10(3) g mol(-1). As a result, those reveal that the resonant length of the PEG molecule moving with the oscillating plate of 9 MHz is 54.2 Å. We also find that the behaviors of ΔF due to M(n) are mainly caused by the length of the PEG molecule.