Swelling and mechanical behavior of nanoclay reinforced hydrogel: single network vs. full interpenetrating polymer network

Abstract

Despite the various uses of hydrogels, one of their weaknesses is the poor gel strength. To overcome this restriction, the current study has focused on simultaneously employing an interpenetrating polymer network (IPN) structure and nanocomposite hydrogels. Through this approach, the influence of nanofiller in the single network and IPN hydrogel properties was also studied in detail. For this purpose, a novel full interpenetrating polymer network (IPN) hydrogel nanocomposite based on 2-acrylamido-2-methylpropane sulfonic acid (AMPS)/acrylic acid (AA)–sodium acrylate (AANa) was synthesized in two steps through a facile solution polymerization with incorporation of modified bentonite (MBE) as nanofiller. The prepared modified nanoplatelets, MBE, were characterized by XRD and FT-IR. The effect of MBE content on the chemical structure of single network and full IPN hydrogels was studied by FT-IR, XRD and DSC. The obtained swelling capacity for these IPN hydrogel nanocomposites was generally decreased by incorporation of MBE nanosheets. So that the lowest water absorbency (about 25 g/g) was obtained for the nanocomposite hydrogels containing 10 wt% of MBE. Moreover, rheological method and tensile test were used to investigate the mechanical properties of hydrogels. The results indicated that by increasing the MBE content in the IPN hydrogel network, the storage modulus of the prepared nanocomposite showed a totally different behavior compared to that of single network hydrogel. It is worth noting that IPN hydrogel containing only 1 % nanoclay showed the highest Young’s modulus in comparison to that of other prepared hydrogels. On the other hand, the highest elongation (about 600 %) was observed for MBE-free IPN hydrogel matrix. Thus, fascinating elastic responses and full recovery after a few minutes of unloading indicate that the synthesized IPN nanocomposite hydrogel exhibits admissible mechanical strength, which makes it a promising candidate for various applications.