Strain Analysis of a Chiral Smectic A Elastomer

TL;DR

This paper investigates the molecular packing and domain behavior of a strained chiral smectic A liquid crystal elastomer, revealing preserved smectic order under strain and modeling its mechanical response.

Contribution

It provides the first detailed analysis showing smectic domain order preservation and introduces a nonlinear elastic model for domain rotation under strain.

Findings

Smectic domain order remains intact under strain.

Reorientation, not loss, of molecular order occurs orthogonal to strain.

A nonlinear elastic model describes domain rotation.

Abstract

We present a detailed analysis of the molecular packing of a strained liquid crystal elastomer composed of chiral mesogens in the smectic A phase. X-ray diffraction patterns of the elastomer collected over a range of orientations with respect to the X-ray beam were used to reconstruct the three-dimensional scattering intensity as a function of tensile strain. For the first time, we show that the smectic domain order is preserved in these strained elastomers. Changes in the intensity within a given scattering plane are due to reorientation, and not loss, of the molecular order in directions orthogonal to the applied strain. Incorporating the physical parameters of the elastomer, a nonlinear elastic model is presented to describe the rotation of the smectic-layered domains under strain, thus providing a fundamental analysis to the mechanical response of these unique materials.