Entropy-Driven Design of Highly Impact-Stiffening Supramolecular Polymer Networks with Salt-Bridge Hydrogen Bonds

Abstract

Impact-stiffening materials that undergo a strain rate-induced soft-to-rigid transition hold great promise as soft armors in the protection of the human body and equipment. However, current impact-stiffening materials, such as polyborosiloxanes and shear-thickening fluids, often exhibit a limited impact-stiffening response. Herein, we propose a design strategy for fabricating highly impact-stiffening supramolecular polymer networks by leveraging high-entropy-penalty physical interactions. We synthesized a fully biobased supramolecular polymer comprising poly(α-thioctic acid) and arginine clusters, whose chain dynamics are governed by highly specific guanidinium-carboxylate salt-bridge hydrogen bonds. The resulting material exhibits an exceptional impact-stiffening response of ∼2100 times, transitioning from a soft dissipating state (21 kPa, 0.1 Hz) to a highly stiffened glassy state (45.3 MPa, 100 Hz) with increasing strain rates. Moreover, the material's high energy-dissipating and hot-melting properties bring excellent damping performance and easy hybridization with other scaffolds. This entropy-driven approach paves the way for the development of nextgeneration soft, sustainable, and impact-resistant materials.

An organic/inorganic hybrid soft material for supramolecular adhesion

“…Poly[ TA ] is a hard and fragile thermoplastic material that can be easily modified using various additives through covalent and/or supramolecular cross-linking. 15–19 The incorporation of functional chemicals endows poly[ TA ] with multiple amazing properties, such as self-healing, conductivity, elasticity, and adhesion properties. 20–24 To date, the majority of additives used in poly[ TA ] systems are restricted to organic compounds, including ionic liquids, fluorescent molecules, and natural acids/sugars.…”