Multi-scale energy dissipation behavior of sustainable polymer networks governed by dynamic bond strength and kinetics

초록

Efficient attenuation of stress waves across a broad frequency spectrum is a critical requirement for next-generation protective systems, yet conventional viscoelastic polymers remain fundamentally limited by narrow damping windows governed by their glass transition temperatures. Here, we demonstrate a strategy for achieving broadband energy dissipation by harnessing dynamic ionic crosslinking within sustainable, lipoic acid (LA)-based polymer networks. By tuning the crosslinking chemistry - comparing permanent covalent amide bonds (P) against a series of reversible primary (I-1), secondary (I-2), and tertiary (I-3) ammonium carboxylate ionic linkages - we elucidate the governing roles of bond strength and dynamics across regimes spanning quasi-static deformation to high-strain-rate shock loading (>10(6) Hz). Under extreme high-strain-rate conditions, we observe a clear decoupling between linear viscoelastic metrics (tan delta) and pressure attenuation, wherein energy dissipation is attributed to force-induced bond rupture rather than chain relaxation. The efficiency of this attenuation correlates with the thermodynamic bond strength: a lower activation threshold for bond scission facilitates more effective energy dissipation. Under quasi-static and low-strain-rate conditions, although covalent networks provide higher structural rigidity, the ionically crosslinked systems exhibit superior toughness and a damping capacity exceeding 50%, enabled by the rapid dissociation and re-association of sacrificial ionic junctions. In this strain-rate regime, the kinetic exchange rate of the ionic junctions, rather than their thermodynamic strength, primarily governs the mechanical and energy-dissipation behavior. This complementary control by bond strength and exchange kinetics allows the weaker, more dynamic networks to sustain an exceptionally broad effective damping window (tan delta > 0.3) from low frequencies to the ultra-high-frequency shock regime. These findings offer a robust framework for designing sustainable, self-healable elastomers capable of multi-scale vibration control and high-velocity impact protection.

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