Industrial & Engineering Chemistry Research, Vol.59, No.22, 10705-10715, 2020
Facile Method to Fabricate Superstrong and Tough Poly(vinyl alcohol) Hydrogels with High Energy Dissipation
To enhance the intermolecular interaction of poly(vinyl alcohol) (PVA) hydrogels, after the freeze-thaw process, the primary formed PVA hydrogel was further annealed for a controlled time, followed by soaking in a CaCl2 aqueous solution. The evolution of a dual cross-linking bonding network structure in the hydrogels was studied, and it was found that the intermolecular hydrogen-bonding interaction was enhanced by the annealing process; the hydrogen-bond-component-abundant crystalline phase was formed, resulting in an increase in crystallinity and the crystalline domain size and a decrease in the crystalline domain distance. Thus, the formation of the dense network structure was accompanied by a perfect crystalline structure, significantly increasing the cross-linking density (V-e) and decreasing the pore size for the PVA hydrogels. After soaking in the CaCl, aqueous solution, a hydroxyl-Ca2+ coordination interaction was formed, leading to a much higher ue and a more compact network structure. As a result, the tensile strength and the fracture toughness of the PVA hydrogel with a dual cross-linking bonding reached 8.40 MPa and 14.16 MJ.m(-3), which were roughly 6- and 12-fold higher than those of the nonannealed PVA sample, respectively. Meanwhile, the dynamic nature of hydrogen bonds and Ca2+-hydroxyl coordination bonds imparted hydrogel with energy dissipation. This work provided a facile method to fabricate a superstrong and tough PVA hydrogel without the incorporation of toxic additives for application in the load-bearing biomedical area.