Deodorizing Performance of Cellulose Nanowhisker-Reactive Dye Adducts as Pigment Inks for Dyeing and Inkjet Printing

In this study, cellulose nanowhiskers (CNWs) were covalently grafted with Sumifix Brilliant Red (BR), which is a reactive dye for cellulose. The reaction of BR with CNWs obtained via hydrochloric acid hydrolysis or those obtained using sulfuric acid hydrolysis (labeled SCNWs) readily proceeded to yield BR-grafted nanowhiskers (BRCNWs or BRSCNWs, respectively). The surface hydroxyl groups on BRCNWs were further modified via sulfation using 50% H₂SO₄, phosphorylation using a urea–phosphoric acid mixture, carboxylation by adding succinic anhydride, or oxidation with 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO). Except TEMPO oxidation, all modification reactions successfully introduced surface anionic groups, such as sulfate, phosphate, and carboxyl groups. These anionic groups were quantified using conductometric titration, and the obtained values corresponded to their degrees of dispersion. Because the surface anionic groups could capture gaseous ammonia, the freeze-dried nanowhiskers exhibited a significant deodorizing performance against ammonia. Subsequently, the BR-grafted nanowhiskers were inkjet-printed onto cotton or cotton/polyester fabrics or directly applied as a dye via immersion. With their nanosized dimensions, BR-grafted nanowhiskers could effectively adhere onto cotton fabrics, resulting in successful dyeing and printing. The resulting dyed and printed fabrics exhibited similar deodorizing performances, demonstrating the promising utilization of BR-grafted nanowhiskers as functional pigments to provide deodorization.