Properties of Liquid Crystalline Elastomer Foams.

We investigate how controlled foaming alters the mechanical dissipation of liquid crystalline elastomers (LCEs). Using thermally expandable microspheres, we generate homogeneous foams with precisely tuned bubble volume fractions up to ∼13%, and compare their behavior with non‑mesogenic silicone analogues. We show that microsphere expansion induces a particle‑centered mesogenic interphase, arising from local elastic distortion and preferential alignment of mesogenic units at the inclusion surface. At low bubble volume fractions (≈0.5%-5%), isolated interphases produce a pronounced enhancement of intrinsic viscoelastic loss. Under impact loading, the optimum shifts to moderate bubble fractions because transient compression also engages bubble deformation, pad compliance, and structural integrity. At higher loadings, interphase overlap and mechanical constraint suppress this effect, and the dissipation returns toward baseline elastomeric values. Large‑strain tensile tests and impact experiments exhibit the same non‑monotonic trend, demonstrating that low‑density LCE foams 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.