Preparation of high water-absorbing hydrogel based on grafted micro/nano cellulose

Abstract

An absorbent hydrogel with high-permeable solution resistance was prepared by free radical polymerization and crosslinking, by the process of micro/nano cellulose grafting with acrylic acid (AA) and 2-acrylamide-2-methyl propyl sulfonic acid (AMPS). Imbibition swelling curves revealed that absorbency of the hydrogel reached 70.2, 483.9, and 436.7 g/g in 0.9 wt% sodium chloride solution, 3 wt% urea solution, and rainwater, respectively. Fourier transform infrared results confirmed that acrylic acid (AA) and 2-acrylamide-2-methyl propyl sulfonic acid (AMPS) were grafted onto the micro/nano cellulose surface and the fiber structure persisted. Analysis with a confocal laser scanning microscope showed many pores on the polymer’s surface. Roughness became larger after grafting, which was conducive to water absorption capacity. Scanning electron microscopy (SEM) results showed that the main morphology of micro/nano cellulose did not change. BET results showed the presence of mesopores and macropores, which made the absorbent hydrogel highly permeable, allowing the internal and external absorbent groups to absorb water. H NMR confirmed that the cellulose was grafted with water-absorbent groups. In addition, lamellar structure and porous network morphology showed graft reaction occurred on the surface of micro/nano cellulose. The hydrogel has potential for agriculture and forestry, including in desertified and self-irrigated areas.