Deciphering the viscoelastic properties of mussel-inspired metal-coordinate physical gels through the lens of tack testing

Erica Lai
Department of Materials Science and Engineering, PPSM, Massachusetts Institute of Technology


In recent years, researchers have incorporated mussel-inspired metal-coordinate crosslinks into various types of gels to improve their mechanical properties, particularly toughness and self-healing. However, not much is understood about how the linear viscoelastic properties of these gels dictate their tack properties. In this study, both rheological and tack tests are performed on metal-coordinate gels comprised of 4-arm PEG end-functionalized with histidine (His) that bind with Ni2+. Using the Ni2+-His ratio to control the functionalities and fractions of HisnNi2+ complex crosslinks present, we explore correlations between linear mechanical properties (i.e. plateau modulus, Gp, and characteristic relaxation time, τc) and tack behavior (i.e. peak stress, σmax, and energy dissipation per volume, EDV). Both σmax and EDV are strongly influenced by Gp and τc; the EDV after reaching σmax is additionally dependent on the wt%. These findings are consistent with the proposed molecular mechanics of the reversible HisnNi2+ crosslinks. With these insights, incorporating metal coordination into adhesive materials could provide condition-dependent control of adhesive properties.

Date of Talk: 

April 17, 2019