Enhanced mechanical performance of xylan-based composite hydrogel via chain extension and semi-interpenetrating networks

Improving the mechanical performance of hemicellulose-based hydrogel is an enormous challenge. Here, we propose a new strategy to achieve the hemicellulose-based hydrogels with superior mechanical performance through chain extension and semi-interpenetrating polymeric networks (semi-IPN). Xylan, known as the main type of hemicelluloses in angiosperms, is successfully modified to increase molecular weight by reductive amination reaction, overcoming the major limitation of brittleness. Then, the chemical network is obtained by graft copolymerizing acrylic acid (AA) with cross-linking agent N,N '-methylenebisacrylamide (MBA) in the presence of chain extended xylan (CEX). With the further introduction of ferric ions, a physical network is constructed via metal-ligand interactions. Such a xylan-based semi-IPN hydrogel shows excellent mechanical properties with a fracture tensile stress of 1.4 MPa, compression stress of 0.59 MPa, and the elongation at break of 1136%. In addition, the hydrogel also exhibits fine water absorbency (213.6 g/g) and high electrical conductivity (4.76 x 10(-3) S/m). We anticipate that the resultant xylan-based semi-IPN hydrogels will open up a new approach for the design of high performance hemicellulose-based soft materials.