Surface dynamics of a freely standing smectic-A film

TL;DR

This paper provides a theoretical analysis of surface fluctuations in freely standing smectic-A liquid crystal films, identifying two main dynamic modes and suggesting experimental methods to measure material properties.

Contribution

It introduces a comprehensive theoretical model including viscous hydrodynamics and predicts how light scattering can reveal key material coefficients.

Findings

Identification of undulation and peristaltic modes as dominant surface fluctuations.

Demonstration that light scattering experiments can measure viscosity and elastic coefficients.

Comparison of theoretical power spectrum with existing experimental data.

Abstract

A theoretical analysis of surface fluctuations of a freely standing thermotropic smectic-A liquid crystal film is provided, including the effects of viscous hydrodynamics. We find two surface dynamic modes (undulation and peristaltic). For long wavelengths and small frequencies in a thin film, the undulation mode is the dominant mode. Permeation enters the theory only through the boundary conditions. The resulting power spectrum is compared with existing experiments. It is also shown that feasible light scattering experiments on a freely standing smectic-A film can reveal viscosity and elastic coefficients through the structure of the power spectrum of both the undulation and peristaltic modes.