Effect of functionalized multiwalled carbon nanotubes on the mechanical, swelling and viscoelastic properties of gum ghatti-cl-poly(NIPAm) hydrogels

Abstract

In this work, gum ghatti-cl-poly(NIPAm)/-o-MWCNT (GGNIPACNT) hydrogels were prepared via free radical polymerization technique. The synthesized hydrogels were characterized through FTIR analysis, which suggested the successful binding of -o-MWCNTs to the hydrogels. This study explored the influence of the content of oxidised multiwalled carbon nanotubes (-o-MWCNTs) on the rheological and mechanical properties of gum ghatti-cl-poly(NIPAm) hydrogels. To evaluate their rheological behavior and processibility, we mixed different concentrations of oxidised multiwalled carbon nanotubes (-o-MWNTs) in the hydrogel, and their rheological properties were measured using a cone and plate rheometer. It was found that with an increase in the aspect ratio or concentration of -o-MWNTs, -o-MWNT interactions became stronger, as indicated by the higher storage modulus G′, complex viscosity |η*|, and steady shear viscosity η. All hydrogels demonstrated shear thinning behavior and the nanotubes showed a statistically substantial arrangement in the direction of shear flow. The flow curves of the hydrogel samples displayed non-Newtonian behavior. The flow viscosity vs. shear rate profiles were calculated using the power law model, while flow shear stress vs. shear rate curves were evaluated by applying the Herschel–Bulkley model, where both the models were found to be the best fitting models. The frequency-dependent rheological behaviors of the nanocomposites in the linear viscoelastic region indicated that the storage modulus (G′), loss modulus (G′′), and complex viscosity (|η*|) increased with an increase in the content of -o-MWCNTs. The linear viscoelastic measurements showed that both the complex viscosity and moduli of the nanocomposites increased with an increase in the -o-MWCNT concentration. The results showed that the mechanical properties of the composite hydrogels were considerably enhanced with an increase in the content of -o-MWCNTs. Therefore, these hydrogels have potential applications in biomedical fields without the restrictions of water capacity and mechanical properties.