Fabrication and Characterization of Hydrogels From NaOH ‐Dissolved Lignocellulose and Carboxymethyl Cellulose

Abstract

Carboxymethyl cellulose (CMC) has been developed as a renewable material for highly absorbent hydrogels, but excessive swelling and insufficient network stability have limited its practical applications. Here, organosolv bamboo pulp containing approximately 20 wt% residual lignin was directly dissolved in aqueous sodium hydroxide (NaOH) and incorporated into CMC hydrogels without the need for cellulose purification or nanofibrillation. Composite hydrogels with different CMC/lignocellulose ratios were subsequently fabricated through epichlorohydrin crosslinking. The resulting hydrogels had high gel fractions of 88%–91%, while their water absorption ranged from 73 to 172 g/g. Rheological analysis revealed that increasing the lignocellulose content enhanced the initial network stiffness, whereas the 1:1 CMC/lignocellulose formulation exhibited the greatest resistance to deformation, reaching a maximum stress of 513 Pa at a strain of approximately 4990%. After swelling, the lignocellulose‐rich hydrogels retained a higher storage modulus, confirming the contribution of lignocellulose to network stability. Thermal analysis further showed that the maximum decomposition temperature increased from 295°C for LC‐25 to 348°C for LC‐100. Collectively, these results demonstrate that incorporating NaOH‐dissolved lignocellulose can improve the network stability of CMC hydrogels while preserving their high water‐absorption capacity.