Collaborative Phase Separation Induced by Double Noncovalent Dynamic Crosslinkers in Polyurethane for Supertoughness and Triboelectric Generator Electrode

Abstract

It is a huge challenge to overcome the trade-off among mechanical property, solvent resistance and recyclability by regulating the phase separation size and spatial distribution. Herein, a strategy of two noncovalent dynamic crosslinkers is employed to address it. By simultaneously introducing Adipic dihydrazide (AD) as hydrogen bonding crosslinker and 4,4'-Bis(hydroxymethyl)-2,2'-bipyridine (BPY) as complexation crosslinker, collaborative phase separation topology of polycaprolactone-based polyurethanes is obtained upon similar composition. Different from the large and sparse phase separation topology of PU with single crosslinker, the collaborative phase separation topology is characterized by the smaller size and spacing. This microstructure simultaneously with proper crosslinking and nanodomain reinforcement not only augment its tensile strength but also significantly increases its energy-dissipating. Consequently, the optimal elastomer (A5B5-Zn) achieves a high tensile strength of 37.77 MPa, an exceptional toughness of 504.5 MJ/m3, ultrahigh fracture energy of 248 kJ/m2, nearly 6 times that of counterpart. The high AD hydrogen bonding combined with PCL crystallization also improves this PU solvent resistance deteriorated by BPY coordination bonding as far as possible. Additionally, its ionic conductivity of 22.6 mS/m makes it elastic electrode. The assembled single-electrode triboelectric nanogenerators demonstrate rapid response (~5 ms) and a high-power density of 76.56 mW/m2, capable of driving wearable electronics. This work elucidates the mechanism of collaborative phase separation induced by two noncovalent dynamic crosslinkers, providing a flexible pathway for designing super-tough functional elastomers.