Soft-segment-engineered Self-healing Polyurethane for High-performance Electrorheological Elastomers and Capacitive Sensors

Polyurethane (PU) holds promise as a matrix for electrorheological elastomers (EREs) because of its excellent mechanical properties; however, its high modulus often limits electrorheological (ER) efficiency. This study addresses this by tailoring the soft-segment architecture of PU to adjust its mechanical and dielectric properties, thus improving the ER response of the PU-based ERE. Dynamic covalent bonds have also been introduced to enable self-healing. Using poly(propylene glycol) (PPG), poly(tetramethylene glycol) (PTMG), and polycaprolactone (PCL) as the soft segments, we fabricated EREs with 20 wt% TiO₂. The resulting PPG-ERE exhibited an outstanding ER effect of 229.4% at 3 kV/mm, along with a high stretchability (1835% elongation) and tensile strength of 3.6 MPa. PTMG-ERE has the highest storage modulus of 1.43 MPa at 3 kV/mm and a relatively high tensile strength of up to 6.5 MPa, which is attributed to enhanced hydrogen bonding interactions among the regular PTMG segments. The PCL-ERE with the highest Young’s modulus resulted in the lowest ER efficiency of 48% because of its high crystallization tendency. The PPG-ERE also demonstrated efficient self-healing, recovering 79% of its mechanical strength after 12 h at room temperature. When applied in a capacitive pressure sensor, the PPG-ERE showed a fast response (220 ms) and recovery (90 ms), detecting forces as low as 3 N. This study provides a practical strategy for designing high-performance multifunctional EREs through soft-segment engineering and dynamic bonding.