Polymeric Liquid Layer Densified by Surface Acoustic Wave

TL;DR

This study demonstrates that high-frequency surface acoustic waves can densify polymer liquid films, reducing their thickness and heterogeneity, and making their dynamics more uniform, as shown through ellipsometry and fluorescence microscopy.

Contribution

It introduces a novel method of using high-frequency SAW to densify and homogenize thin polymeric liquid films, with detailed experimental validation.

Findings

SAW decreases film thickness and increases refractive index.

SAW retards molecular rotational motion within the film.

SAW reduces dynamical heterogeneity in the polymer film.

Abstract

With the application of surface acoustic wave (SAW) of 39.5 MHz to a model polymer liquid film,polyisobutylene, deposited on the solid substrates, the liquid film is densified, proved by the decrease of film thickness and the increase of refractive index, measured by ellipsometry. Rotational motion of fluorescent probes doped inside the liquid film, measured by polarization-resolved single molecule fluorescence microscopy, is retarded and the dynamical heterogeneity is reduced. It is demonstrated that the application of SAW of high frequency makes the thin polymeric liquid film densified and more dynamically homogeneous.