Origins of solidification when a simple molecular fluid is confined between two plates

Abstract

A simple globular-shaped liquid (octamethylcyclotetrasiloxane, OMCTS) was placed between two rigid mica plates at variable spacings comparable to the size of this molecule and the linear shear viscoelasticity of the confined interfacial film was measured. Strong monotonic increase of the shear relaxation time, elastic modulus, and effective viscosity were observed as the spacing was decreased below about 10 molecular dimensions. The frequency dependence of the viscoelastic spectra measured at different film thicknesses appeared to scale with reduced variables. The data are inconsistent with the abrupt first-order transition, from bulk fluid to solid with decreasing film thickness, whose possibility has been hypothesized, and suggest a glasslike transition instead.