Improving the mechanical performance of P(N-hydroxymethyl acrylamide/acrylic acid/2-acrylamido-2-methylpropanesulfonic acid) hydrogel via hydrophobic modified nanosilica

Hydrogels with high mechanical strength are essential for its most industrial applications. In this work, the hydrophobic SiO2 nanoparticles (M-SiO2 NPs) modified with octadecyltrimethoxysilane were used as physical crosslinker to toughen the mechanical properties of hydrogels. The solution of monomers containing M-SiO2 NPs, N-hydroxymethyl acrylamide (NHAM), acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), was polymerized to prepare a P(NHAM/AA/AMPS)-based composite hydrogel without any chemical cross-linker. The composition and microstructure of the hydrogel were carefully studied with Fourier transform infrared spectroscopy and scanning electron microscopy. The mechanical properties of the hydrogel were investigated through compressive and tensile tests. Dynamic swelling tests were carried out at different pH values (1.0-12.0) and salinity (2000-20,000 mg/L) to study the acid resistance, alkali resistance, and salt resistance of the hydrogel. The obtained results showed that the hydrogel exhibited excellent mechanical performance, which was attributed to the unique 3D network formed by the hydrogen bond between M-SiO2 NPs and polymer as well as the hydrophobic association effect between the hydrophobic chains of M-SiO2 NPs. Furthermore, the hydrophobic association effect was enhanced when contacting with salt, acid, and alkali solutions, thus endowing the hydrogel with intensified salt resistance and wider acid-base adaptability range.

Automated summary

This study investigated the effect of modified SiO2 nanoparticles on the mechanical properties of hydrogels. The results showed that the hydrogel exhibited excellent mechanical performance and strong acid-base resistance.