Electrocapillary wave studies of oligomeric ethers: Poly(dimethylsiloxane) and poly(ethylene glycol)

Abstract

With the aid of a technique that induces electric field-generated capillary waves on polymeric liquid surfaces and the resulting wave propagation characteristics detected by an optical diffraction method, we examined the surface tension and steady shear viscosity of low molecular weight poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEG) at different temperatures. The surface tension values are in quite good agreement with those reported in the literature, whereas the shear viscosity values are not as accurate, though they agree within 7% with those determined by a capillary viscometer. The temperature dependences of the surface tensions of both are in agreement with the literature. On the other hand, they differ in their molecular weight dependences, though PDMS shows a small difference due to its relatively small molecular weight, but the PEG slope was in good agreement in spite of its low molecular weight due to its hydrogen bonding. PDMS and PEG show different mode behaviors at high frequency and low temperature because of the overdamped mode appearance for PEG.