Biomimetic stiffness modulator driven by bi-mode hydrogen bond locking mediated nano-heterogeneous aggregation

The ability to dynamically adjust mechanical stiffness is crucial for materials requiring adaptive responses. However, simultaneously achieving broad-range reversible modulus regulation, high toughness, and robust impact resistance remains a significant challenge. Herein, inspired by the stiffness modulation mechanisms in biological systems, we developed a bi-mode biomimetic stiffness modulator (BSM) with reversible modulus transition, high toughness, and impact-resistant properties. The BSM has a comb-like molecular configuration structure with a hydrophobic main chain and hydrophilic side chains. This unique design enables a bi-mode soft–stiff transition, mediated by hydrogen bond locking and nano-heterogeneous aggregation. When exposed to polar or nonpolar molecules, the hydrophilic and hydrophobic segments are selectively locked. This leads to the formation of nano-heterogeneous aggregation microdomains and a substantial improvement in mechanical properties. This strategy allows the modulus to reversibly increase by 9.9 times, while still maintaining ultrahigh toughness (254.44 MJ m −3 ) and exceptional impact resistance. Moreover, the soft-stiff transition of bi-mode BSM is fully reversible and it can be thermally recycled and remediated with negligible property loss. The bi-mode BSM demonstrates excellent functionality in the smart protection of automotive windows and wearable electronics from harsh conditions and serious impacts. Bi-mode BSM provides a new molecular design paradigm for high-performance modulators in flexible electronics and protective systems.