Synthesis and Swelling Behavior of pH-Sensitive Semi-IPN Superabsorbent Hydrogels Based on Poly(acrylic acid) Reinforced with Cellulose Nanocrystals

pH-sensitive poly(acrylic acid) (PAA) hydrogel reinforced with cellulose nanocrystals (CNC) was prepared. Acrylic acid (AA) was subjected to chemical cross-linking using the cross-linking agent MBA (N,N-methylenebisacrylamide) with CNC entrapped in the PAA matrix. The quantity of CNC was varied between 0, 5, 10, 15, 20, and 25 wt %. X-ray diffraction (XRD) data showed an increase in crystallinity with the addition of CNC, while rheology tests demonstrated a significant increase in the storage modulus of the hydrogel with an increase in CNC content. It was found that the hydrogel reached maximum swelling at pH 7. The potential of the resulting hydrogels to act as drug carriers was then evaluated by means of the drug encapsulation efficiency test using theophylline as a model drug. It was observed that 15% CNC/PAA hydrogel showed the potential to be used as drug carrier system.