**2. Materials and Methods**

### *2.1. Materials*

CNF was obtained by oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) [29]. The synthesis was performed using a cellulose sample from Norweigan spruce wood, according to the procedure described by Dax et al. [30]. The suspension used in this study had a concentration of 10.79 mg g−1. Through conductometric titration analysis, it was determined that the CNF contained 0.96 mmol COO− per gram of fiber.

[2-(acryloyloxy)ethyl]trimethylammonium chloride (ClAETA) solution (80 wt% in water; Aldrich, St. Louis, MO, USA), *N*,*N*-methylene-bis-acrylamide (MBA) (99%; Aldrich, St. Louis, MO, USA), ammonium persulfate (APS) (98%; Aldrich, St. Louis, MO, USA), NaOH (Merck, St. Louis, MO, USA), HNO3 (70%, Merck, St. Louis, MO, USA), HCl (36 v%; Merck, St. Louis, MO, USA), MO (85 vol% dye content; Sigma-Aldrich, St. Louis, MO, USA), and demineralized diethyl ether (99%, Merck, Milwaukee, WI, USA) were purchased and used in this study.
