Obtaining and Characterization of Hydrogels of Poly (Acid Acrylic-co-Acrylamide) Reinforced with Cellulose nanocrystals from Acacia farnesiana L. Willd (Huizache)

Abstract: In this work, cellulose nanocrystals (CNC) were obtained from the wood of Acacia far-nesiana L. Willd (huizache) by acid hydrolysis. These were used to reinforce polyacrylic acid-co-acrylamide (AAc/AAm) hydrogels synthesized in a solution process by in situ free radical photo-polymerization. The nanomaterials were characterized by atomic force microscopy and dynamic light scattering (DLS) and the residual charge on CNC; the nanohydrogels were characterized by infrared spectroscopy, scanning electron microscopy, swelling kinetics, and Young's modulus. The soluble grade cellulose presented 94.6% α-cellulose, 0.5% β-cellulose, and 2.7% γ-cellulose, a viscosity of 8.25 cp, and a degree of polymerization (DP) of 706. The CNC averaged 180 nm in length and 20 nm in width. In the nanohydrogels, it was observed that the Schott kinetic model was followed at times lower than 500 h; after that, the swelling kinetic behavior is linear. The re-sults show that the hydrogel swelling capacity depends on crosslinking agent and CNC concen-tration as the chemical and morphological CNC properties rather than a CNC source. The pres-ence of CNC decreases the swelling degree compared to hydrogels without CNC. Young's modu-lus increased with CNC presence and depended on CNC characteristics as crosslinking agent and concentration.