Flexible Interfacial Anchoring via Titanate Coupling Agent Enables Enhanced Dielectric and Electromechanical Actuation Performance in BaTiO3/TPU Nanocomposites

Incorporating high-permittivity ceramic nanofillers is an effective strategy to enhance the dielectric constant via interfacial polarisation, thereby boosting the electromechanical sensitivity of dielectric elastomer actuators (DEAs). However, filler agglomeration due to surface energy mismatch deteriorates material properties and weakens actuation capabilities. To address this challenge, we propose a ‘flexible interfacial anchoring’ strategy distinct from conventional rigid modification. KR38S coupling agents are covalently anchored onto BaTiO 3 nanoparticles via condensation reaction. Unlike hyperbranched modification requiring a thick polymer coating and topological interlocking, the long dioctyl chains of KR38S achieve a dual function: hydrophobic alkyl segments form an isolation layer that mitigates interfacial voids and charge traps, while flexible chains entangle with TPU polyether soft segments, creating a compliant cushion layer dynamically interconnected with the matrix. Benefiting from improved dispersibility and compatibility, the dielectric properties of the composites were substantially enhanced. The breakdown strength increased from 154.5 kV/mm for pristine TPU to 213.2 kV/mm for 5 wt% mBT/TPU, and the 10 wt% composite achieved an actuation displacement of 3.03 mm at 46.2 kV/mm, compared to 0.69 mm for pristine TPU at 29.2 kV/mm. This study provides a facile route to high-performance DEAs for soft robotics, flexible electronics, and intelligent wearables.