Properties of Liquid Crystalline Elastomer Foams

TL;DR

This study explores how controlled foaming in liquid crystalline elastomers enhances their damping properties through microstructural interphase engineering, offering a new approach for high-performance impact-absorbing materials.

Contribution

It demonstrates that low bubble volume fractions in LCE foams create interfacial effects that significantly increase damping, providing a novel microstructural method to improve soft solid damping performance.

Findings

Maximum damping occurs at low bubble volume fractions (~5%.

Damping enhancement is due to mesogenic interphase formation around microspheres.

LCE foams retain mechanical integrity under impact, unlike conventional foams.

Abstract

We investigate how controlled foaming alters the mechanical dissipation of liquid crystalline elastomers (LCEs). Using thermal expandable microspheres, we generate homogeneous foams with precisely tuned bubble volume fractions up to 13% and compare their behaviour with non-mesogenic silicon analogues. We show that microsphere expansion induces a particle-centred mesogenic interphase arising from local elastic distortion and preferential alignment of mesogenic units at the inclusion surface. At low bubble volume fraction (0.5 to 5%), these interfaces remain spatially isolated and produce a pronounced no-monotonic enhancement of damping, with the loss factor reaching tan-delta=0.2 even in the isotropic regime. At higher loading, interphase overlaps and mechanical constraints suppress this effect, and the dissipation returns towards baseline elastomeric values. Large-strain tensile tests and impact experiments exhibit the same non-monotonic trend, demonstrating that low density LCE forms achieve the highest mechanical energy absorption per unit mass. Compared with conventional high porosity polymer foams used for acoustic damping, these materials retain sufficient mechanical integrity to sustain impact loads, establishing a microstructural route to engineer high-performance damping in soft solids.