Mechanical and swelling properties of polyacrylamide/polyacrylic acid composite hydrogels: The effects of network structure and carbon nanotube reinforcement

Abstract

The tensile elastic modulus and swelling of polyacrylamide/polyacrylic acid hydrogels was investigated to evaluate the effects of the gel structure (random copolymer and interpenetrating network) and reinforcement with multiwall carbon nanotubes (MWCNTs) on their mechanical properties. The tensile modulus of the interpenetrating network gels was significantly higher than that of random copolymer gels when compared at the same amount of swelling. This disparity can be explained by the difference in stiffness between the respective crosslinked polymers. The tensile modulus of both hydrogels increased when reinforced with MWCNTs, whereas the maximum amount of swelling decreased. The change in the mechanical and swelling properties after reinforcement with MWCNTs could be explained by the spatial distribution of hydrogen bonds between the MWCNT, acrylamide, and acrylic acid moieties.