Molecular Entanglement and Interface Locking by Inorganic Sub-nanowires for Concurrent Mechanical and Piezoelectric Reinforcement in Polymer Composites

Abstract

The inherent trade-off between mechanical robustness and piezoelectricity in flexible poly(vinylidene fluoride) (PVDF) has long limited its practical applications. This work introduces calcium–polyoxometalate sub-nanowires (Ca–POM SNWs) into the PVDF matrix, overcoming this limitation via molecular entanglement and sub-nanoscale interface locking. Within the PVDF matrix, Ca–POM SNWs form a 3D interpenetrating network, enhancing the elastic modulus by 180% and toughness by 619%. During electrospinning, electric field-induced alignment of Ca–POM SNWs creates a periodic architecture that, together with non-covalent interactions, locks PVDF chains into the piezoelectric β-phase, raising its content from 43.6% to 97.9% and the piezoelectric coefficient (d₃₃) by 195%. This synergy also yields anisotropic fibrous membranes with high modulus and toughness. The concurrent mechanical and piezoelectric reinforcement by SNWs-mediated molecular entanglement and interface locking represents a breakthrough beyond the capability of conventional nanofillers. Integrated as a sensor array in a smart insole and combined with machine learning, the PVDF/Ca–POM composite achieves 100% accuracy in classifying six different human motion states, showing promise for early detection and dynamic monitoring of diabetic foot ulcers. This study establishes a new approach to high-performance piezoelectric composites through sub-nanometer-level interfacial engineering.

Keywords

Inorganic sub-nanowire / Molecular entanglement / Interface engineering / Mechanical property / Piezoelectric property

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Funding

National Natural Science Foundation of China(22172194)

Natural Science Foundation of Shandong Province(ZR2025MS178)

RIGHTS & PERMISSIONS

Donghua University, Shanghai, China