Many natural hydrogels, show remarkable properties with Young’s moduli up to 100 MPa and fracture energies up to 9000 J m-2. Although advances in the synthesis of tough hydrogels have been made -especially by the usage of organic double-networks- most of them suffer from low stiffness. Exchanging one of the organic phases in a double network with an inorganic one can improve the mechanical properties and create stiff hydrogels, which are a viable and recommended choice for membrane technologies and stimuli-responsive materials. We could achieve water-swollen organic/inorganic double network hydrogels with tunable Young’s modulus (up to 440 MPa) and high toughness (up to 1300 J m-2) by homogeneously embedding enzymes in polymer hydrogels and enzyme-induced mineralization. The increased stiffness can be explained by the isotropic and homogeneous growth of percolating, amorphous calcium phosphate structures inside the water-swollen network. One key factor for the formation of a percolated inorganic phase within a hydrogel is the precipitation of the inorganic salt in its amorphous form. In order to broaden this concept towards new ultrastiff hydrogels, the enzyme-induced formation of amorphous calcium carbonate was addressed by incorporation of crystallization inhibitors into urease-loaded hydrogels. This leads to homogenous and controlled growth of amorphous calcium carbonate nanostructures inside the hydrogel, resulting in new double-network composite hydrogels with high stiffness and toughness.

Ultrastiff and tough organic/inorganic double network hydrogels

2019 Spring National Meeting

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