Deciphering How the Viscoelastic Properties of Mussel-Inspired Metal-Coordinate Transiently Cross-Linked Gels Dictate Their Tack Behavior.

In recent years, researchers have incorporated mussel-inspired metal-coordinate cross-links into various types of gels to improve their mechanical properties, particularly toughness and self-healing. However, not much is understood about how the linear mechanical properties of these gels dictate their tack properties. In this study, we use shear rheology and tack tests to explore correlations between linear viscoelastic properties (i.e., plateau modulus, G_p, and characteristic relaxation time, τ_c) and tack behavior (i.e., peak stress, σ_max, and energy dissipation per volume, EDV) of transiently cross-linked hydrogels comprised of histidine-functionalized 4-arm PEG coordinated with Ni²⁺. By using the Ni²⁺-histidine ratio and polymer wt % of the transient networks to control their viscoelastic properties, we demonstrate a strong dependence of σ_max on G_p and τ_c. The observed correlation between network dynamics and mechanics under tensile load is in good quantitative agreement with a theoretical framework for σ_max, which includes the linear viscoelastic properties as parameters. EDV is also influenced by G_p and τ_c, and the EDV after reaching σ_max is additionally dependent on the polymer wt %. These findings are consistent with previously proposed molecular mechanics of reversible His_xNi²⁺ cross-links and provide us with new insights into the correlations between bulk mechanics and adhesive dynamics of gels with transient metal-coordinate cross-links.

Duke Scholars

Author Bavand Keshavarz Thomas Lord Department of Mechanical Engineering and Materia ...