Synthesis of nanocomposite hydrogels based on polyacrylamide and cellulose nanocrystal

Abstract

In this research, we employed a mussel-inspired strategy to the synthesis and characterization of nanocomposite hydrogels based on polyacrylamide (PAM) and cellulose nanocrystal. Nanocomposite hydrogel was prepared by freeradical polymerization of acrylamide and dopamine (DOPA) grafted carboxylated cellulose nanocrystal initiated by redox initiator potassium persulfate (KPS) and N, N´-methylene bisacrylamide (MBA) was employed as a crosslinking agent.Dopamine grafted carboxylatedcellulose nanocrystal has been incorporated into the polymer matrix (PAM) to produce a mechanically stable hydrogel. First, cellulose nanocrystal (CNC) was synthesized from a waste sawdust. The synthesized CNC was converted to carboxylated cellulose nanocrystal (CCN) by using selective oxidizing agent 2,2,4,4-tetramethyl-1-oxyalpiperidine (TEMPO) radical. Then we synthesized a CCN-DOPA material. In presence of coupling agent N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), the CCN was modified with dopamine (DOPA) bythe coupling reaction. Finally the synthesized CCN-DOPA was incorporated in cross-linked polyacrylamide (PAM) hydrogels. Incorporated CCN-DOPA in hydrogel produced nanocomposite hydrogel. The morphology of theresulting nanocomposite hydrogels, thermo-sensitive properties, and swelling behavior were investigated. The results indicated that CCN-DOPA-PAM hydrogel exhibited temperature sensitivity. The morphologies observed on the scanning electron microscopy (SEM) images supported that the added CCN-DOPA appeared to be an integral network of the hydrogels, which is responsible for the improved mechanical strength as we expected. In the swelling measurement the hydrogels exhibited appreciable water uptake and were moderately sensitive to temperature.