Frequency-Adaptive Elastomers Through Cooperative Dynamics of Liquid-Crystalline Domains and a Rubber Matrix

Elastomers are highly suitable for components requiring conformal deformation under load, but their low modulus sensitivity to frequency limits the material's ability to resist dynamic damage. Here we report a phase-separated elastomer that remains compliant at low loading frequency and stiffens strongly at high frequency, while preserving elastic recovery. The elastomer comprises a carboxylated nitrile rubber (XNBR) matrix and dispersed liquid-crystalline (LC) domains. Under slow loading, the dispersed phase can relax local stress through mesogen reorientation. In contrast, the same domains become increasingly load-bearing under faster loading as this motion is constrained. As a result, the modulus of the phase-separated elastomer increases by 6.2-fold from 0.01 to 100 Hz, compared with about 2.2-fold for the neat XNBR. In addition to rate stiffening, the materials retain resilience, low hysteresis, and long-term dimensional stability, leading to significantly improved resistance to abrasive wear (77.4% reduction in mass loss), repeated impact (83.7% reduction in damaged ratio), and notch propagation (over 30 000 cycles) upon high-frequency loading, compared with the neat XNBR. These results show that cooperative dynamics between a recoverable rubber matrix and LC domains can provide a useful route to elastomers that combine compliance with adaptive mechanical protection.