A Novel Double Network Hydrogel with High Swelling and Mechanical Properties.

In this investigation, we report double network (DN) hydrogels having high mechanical strength at their swollen state. Such a double network hydrogel is consisting of PVA-borax double strand in which P(AM-HEMA) crosslinked network was embedded by in-situ polymerization. Both the swelling property and tensile strength of the hydrogels (in their swollen state) depends on the composition of the hyrogels. The equilibrium swelling ratio was achieved as high as 1272% for a sample where AM/HEMA=100/0 was taken in the second network (no HEMA). The compositional ratio of AM and HEMA in forming double network has also distinct influence on the mechanical properties of the hydrogels. The tensile strength values for DN hydrogels having 80 wt% water content were measured to be 21.77kPa, 31.47 kPa and 32.21 kPa for the DN hydrogels having AM/ HEMA weight ratio 67/33, 50/50 and 25/75 (PVA-borax content being constant). Elongation of more than 200% was also achieved in such a DN hydrogel. The results obtained in this system of DN hydrogels having PVA-borax network are comparable with those reported for other systems. The high mechanical properties of such hydrogels can be attributed to the reinforcing influence of PVA-borax complex crosslinking onto the P(AM-HEMA) networks. [ABSTRACT FROM AUTHOR]