Porous double network gels with high toughness, high stretchability and fast solvent-absorption.

Using the freeze-drying method, we fabricated porous double network gels with high toughness, high stretchability and fast solvent-absorption. When the freezing temperature was -20 °C and the freezing time was 24 hours, pores with diameters around 300 μm could form in the gel. When the freezing temperature was lowered to -196 °C and the freezing time was reduced to 10 minutes, monodisperse pores with diameters around 15 μm could form in the gel. We found out that both porous gels fabricated under different conditions could absorb solvent much more and much faster than a nonporous gel. Furthermore, we found that the rupturing strain, stiffness and strength of the porous double network gels were all comparable to the nonporous double network gel when containing the same amount of solvent. The unique combination of the mechanical properties of the porous double network gels might motivate new explorations of gels in practical applications.