Artificial lignification of a cellulose microfibril-based hydrogel and resulting effect on tensile properties

Abstract This study examined the influence of lignin dehydrogenation polymer (DHP) deposition on the morphology and properties (e.g., tensile property, thickness, and water content) of cellulose microfibril-based gels. Cellulose microfibrils were isolated from wood powder and a stable hydrogel with a layered structure after treatment with 8% (w/v) NaOH were produced. Gels were artificially lignified of by repeated immersion in an ethanol solution containing lignification agents (coniferyl alcohol, horseradish peroxidase, and H 2 O 2 ) and evaporating the ethanol under vacuum. The use of ethanol allowed DHPs to penetrate the gel, and the deposition of DHPs was achieved by evaporating ethanol under reduced pressure. With increase in the number of lignification cycles to 10, the thickness and water content of the microfibril gels decreased and the ratio of DHP to cellulose, elastic modulus, and tensile strength increased. These results indicate that the elastic modulus of the gels improved not only because of the decrease in water content, but also because of the constrained motion of the microfibril network due to of DHP deposition. The reported artificially lignified cell wall model will help improve the understanding of how lignification contributes to the mechanical strength of plant cell walls.