Crab‐Molting‐Inspired In Situ Stiffening of Growing Dynamic Polymer Networks

ABSTRACT Crab molting is an interesting growing process involving in situ stiffening of the crosslinked exoskeleton. Inspired by this, we propose a post‐forming stiffness regulation strategy for crosslinked polymer materials that enables in situ mechanical enhancement through a “dissociation followed by reinforcement” process. A covalently crosslinked poly(oxime‐urethane) network was constructed based on aromatic isocyanate‐oxime chemistry, wherein oxime‐urethane dynamic bonds undergo reversible dissociation under humid conditions, generating free active groups that simulate the softening stage of molting. Subsequent introduction of aliphatic diisocyanates enables covalent reconstruction with these reactive groups, leading to network reinforcement and modulus enhancement. This growth process increases the Young's modulus by an order of magnitude (12–121 MPa) and prolongs the stress relaxation time from 14.5 to 178.5 s, indicating significantly improved network stability. The resulting polymer exhibits enhanced energy dissipation and recovery after a 24 h relaxation period following cyclic loading. Furthermore, this strategy demonstrates advantages in composite construction: the initially soft matrix facilitates conformal contact with reinforcing components such as carbon fibers, while subsequent in situ enhancement improves composite puncture resistance by 56% compared to the non‐enhanced counterpart. This molting‐inspired approach provides a paradigm for growing polymer materials that combine exoskeleton‐like stability with the ability to modulate stiffness during service life.