Synthesis and characterization of novel semi-IPN nanocomposite hydrogels based on guar gum, partially hydrolyzed poly(acrylamide), and pristine montmorillonite

A range of new semi-interpenetrating polymer network (semi-IPN) nanocomposite hydrogels based on guar gum (GG)/partially hydrolyzed poly(acrylamide) (HPAm)/sodium montmorillonite (NaMMT) were synthesized in an aqueous solution by an in situ simultaneous cross-linking reaction between partially hydrolyzed polyacrylamide chains and chromium acetate as an ionic cross-linker in the presence of GG. Interactions occurring in the resulting hydrogels and examining the structure and morphologies of the prepared hydrogels were studied by various techniques such as TGA, DMA, FTIR, XRD, and SEM. The effects of GG/PAm weight ratio, cross-linking agent, and MMT nanosheets ratios were investigated and reaction variables optimized in response to hydrogel swelling properties. The morphological investigation revealed that MMTs were well dispersed in the nanocomposite matrix. The rheological analysis showed that the storage modulus of the semi-IPN nanocomposite hydrogels slightly raised with MMT addition up to 0.5 wt%, but it increased when the clay content was further growing. The equilibrium water absorbency of the semi-IPN gels in tap water and synthetic oil reservoir water slightly decreased as the concentration of the GG and MMT increased. The incorporation of MMT up to 1 wt% provided an improvement in the swelling capacity and further addition of it decreased the water uptake because of the participation in the cross-linking reaction, which enhanced the cross-linking density. Owing to the introduction of MMT, the nanocomposite hydrogels displayed higher resistance against syneresis in synthetic oil reservoir water as compared with unfilled hydrogels that is a desirable characteristic. The results indicated the novel MMT-based semi-IPN nanocomposite hydrogels can be potentially suitable for the chemically improved oil recovery area.