Fig. 1: Design and synthesis of DiMPU elastomers utilizing a low-entropy-gain-driven toughening strategy.
a Energy dissipated during the cyclic loading and unloading process. Mechanical work (W) is divided into irreversibly dissipated energy (E1) and stored elastic energy (E2). b Thermodynamic explanation for the entropy-driven toughening mechanism. Because of the entropy rise (ΔS > 0) during the dissociation of non-covalent bonds, Gibbs free energy (ΔG) is inversely proportional to ΔS. Consequently, a lower entropy gain will result in a higher energy input for bond rupture, thus enhancing energy dissipation during polymer elongation (assuming comparable enthalpy changes for the dissociation of identical coordination bonds in analogous geometries). c The diverse metal-pyrazole coordination architectures with higher disorder exhibit a lower entropy increase during stretching, thereby suppressing entropy-gain compensatory effects. d Schematic illustrating the synthesis of DiMPU-Cu elastomers and their molecular structures. PTMG poly(tetramethylene ether) glycol, HMDI hydrogenated methylene diphenyl diisocyanate.
