*3.1. Synthesis of Hydrogels Modifying the Amount of Cross-Linker, Initiator, and CNF*

Upon freeze-drying, the hydrogels had a granular texture and were slightly light brown. The nanocomposites synthesized with CNF had a slightly translucent appearance and, when freeze-dried, had granular characteristics and were light brown. Table 3 lists the reaction yields, water absorption, and effective cross-link density of the cross-linked structure of the 12 synthesized hydrogels.

**Table 3.** Characterization results of the synthesized hydrogels: the reaction yields, water absorption, and effective cross-link density of the cross-linked structure of the 12 synthesized hydrogels.


The responses to the variations in the factors in the experimental design are explained below.
