(16c) Self-Healing Hydrogels with High Toughness through Ionic Crosslinking | AIChE

(16c) Self-Healing Hydrogels with High Toughness through Ionic Crosslinking

Authors 

Henderson, K. J. - Presenter, Northwestern University
Otim, K. - Presenter, Northwestern University
Zhou, T. C. - Presenter, Northwestern University
Shull, K. R. - Presenter, Northwestern University


The ability to tailor the molecular-scale dissipation mechanism of crosslinked polymer hydrogels is of significant interest for fabricating tough synthetic alternatives to biological materials. One conceivable method is the extension of ionic crosslinking in an acrylic triblock copolymer hydrogel. The polymer architecture consists of symmetric, hydrophobic poly(methyl methacrylate) endblocks and a hydrophilic poly(methacrylic acid) midblock. These materials spontaneously form bridged, spherical micelles upon appropriate solvent exchange with Young's moduli on the order of 1 kPa. Upon ionic crosslinking with divalent cations (Zn, Ca), the solvated midblock of the polymer chain forms metallic complexes that serve as dynamic, pseudo-covalent linkages that significantly alter the mechanical response of the material. The modulus increases by 2-3 orders of magnitude depending on pH, solution concentration, and cation identity. Tensile testing and compressive indentation tests indicate not only a favorable increase in material toughness but also a considerable degree of recoverable energy dissipation upon successive loading not witnessed in many other toughening mechanisms.