Rapid synthesis of macroporous graphene oxide/poly(acrylic acid-co-acrylamide) nanocomposite hydrogels with pH-sensitive behavior by frontal polymerization

Abstract

Macroporous pH-sensitive graphene oxide (GO)/poly(acrylic acid-co-acrylamide) (PAA) nanocomposite hydrogels were prepared by frontal polymerization (FP) using a solvent mixture composed of DMF and a small quantity of GO water solution as a heat conductive medium. A flat frontal can be obtained. The high temperature on the propagating front evaporated water to produce many vapor bubbles, which were trapped into the hydrogel matrix and consequently formed a macroporous structure (i.e. diameter ca. 120 μm). The increase in the concentration of GO solution led to an increase in front velocity (V_f) and the highest front temperature (T_max). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that GO nanosheets were crosslinked into the PAA hydrogel. Scanning electron microscope (SEM) analysis illustrated that the size of pores in GO/PAA nanocomposite hydrogels highly depended on the concentration of GO solution. The macroporous structure of nanocomposite hydrogels had a significant influence on the pH-sensitive swelling behaviors of the nanocomposite hydrogels. The highest compressive strength of the GO/PAA nanocomposite hydrogel can reach 44.9 MPa.