Influence of Two Carboxylated Cellulose Derivatives on Mechanical Properties of Polyacrylamide Composite Hydrogels

The present study was performed aiming to understand the reinforcing and toughening effects of carboxylated cellulose derivatives with different aggregation structures and carboxylate contents on metal-coordinated composite hydrogels. Zr(IV)-coordinated polyacrylamide (PAM) composite hydrogels with high mechanical performance were fabricated via free radical polymerization of acrylamide (AM) in aqueous systems of TEMPO-oxidized cellulose nanofibers (CNF) or polyanionic cellulose (PAC), followed by posttreatment in 0.1 mol/L zirconyl chloride aqueous solution. The obtained hydrogels were characterized by FT-IR, SEM and compressive/tensile mechanics. The incorporation of CNF or PAC improves the hydrogen bonding interaction in PAM networks, strengthens the mechanics of composite hydrogels, and nanostructured CNF exerts higher effect than PAC at the same dosage. After treated with 0.1 mol/L ZrOCl2, the composite hydrogels behave obvious swelling, but their network structures become denser, and intertwined nanofibrils are found within PAC composited hydrogel networks. For mechanical properties, Zr(IV)-coordinated hydrogels demonstrate significant enhancement effect benefiting from strong Zr(IV)-COO- interactions. At the same amount, PAC plays a much higher role than CNF due to its higher carboxylate content, while the enhancement from CNF is slightly better than that from PAC at the similar carboxylate content. This research provides some implications for designing multivalent metal-coordinated hydrogels composited with carboxylated cellulose derivatives. © 2021, Editorial Board of Polymer Materials Science & Engineering. All right reserved.