By utilizing the alcoholysis nature of boronate bonds, the CF/PBNR composites can be fully recycled at room temperature in ethanol solvent without sacrificing the mechanical properties.
Mechanical robustness and network reconstruction have
always been
paradoxical in dynamically cross-linked polymers. It is highly desirable
to consider polymer architecture while studying chemical bond dissociation
to acquire reversible cross-linking networks with high performance.
Herein, a versatile dynamic covalent bond, e.g., a conjugated and
hindered urea bond (CHUB), and its dissociation chemistry are reported.
Benefiting from the dual effects of conjugation and steric hindrance,
CHUB displayed significant and highly tunable reversibility with respect
to the polymer network design. Three kinds of dynamically cross-linked
networks with widely tuned properties were developed, including the
pristine polyurea network, expanded polyurea network containing epoxy
cores, and networks both cross-linked with traditional and dynamic
covalent bonds. The aromatic, stiff backbone of CHUB ensured dynamically
cross-linked networks with a considerable glass transition temperature
and outstanding mechanical properties. By tuning the ratio of CHUBs
with respect to conventional covalent cross-linking points, dynamically
cross-linked polymers with good creep resistance were also obtained.
The CHUB with both a rigid backbone and high reversibility thus effectively
expanded the scope of dynamic covalent bonds and provided efficient
routes to catalyst-free, easy-to-synthesis, and efficient renewable
networks that are beneficial for theoretical study or practical applications.
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