Strengthening-Durable Trade-Off and Self-Healing, Recyclable Shape Memory Polyurethanes Enabled by Dynamic Boron–Urethane Bonds

Addressing the demand for integrating strength and durability reinforcement
in shape memory polyurethane (SMPU) for diverse applications remains a
significant challenge. Here a series of SMPUs with ultra-high strength,
self-healing and recyclability, and excellent shape memory properties through
introducing dynamic boron–urethane bonds are synthesized. The introducing
of boric acid (BA) to polyurethane leading to the formation of dynamic
covalent bonds (DCB) boron–urethane, that confer a robust cross-linking
structure on the SMPUs led to the formation of ordered stable
hydrogen-bonding network within the SMPUs. The flexible crosslinking with
DCB represents a novel strategy for balancing the trade-off between strength
and durability, with their strengths reaching up to 82.2 MPa while also
addressing the issue of durability in prolonged usage through the provision of
self-healing and recyclability. The self-healing and recyclability of SMPU are
demonstrated through rapid dynamic exchange reaction of boron–urethane
bonds, systematically investigated by dynamic mechanical analysis (DMA).
This study sheds light on the essential role of such PU with self-healing and
recyclability, contributing to the extension of the PU’s service life. The findings
of this work provide a general strategy for overcoming traditional trade-offs in
preparing SMPUs with both high strength and good durability.