*2.2. Cationic Modification of Microcrystalline Cellulose (MCC)*

Microcrystalline cellulose was soaked in a 10% sodium hydroxide solution with a solid to liquid ratio of 1 to 10 (1 g/10 mL) at 25 ◦C for 24 h, whose purpose was to swell cellulose so that CHPTA could enter the cellulose. Then the MCC suspension was centrifuged at 3000 rpm for 10 min and neutralized with diluted hydrochloric acid. After centrifugation, the MCC was dried in an oven at 60 ◦C for 48 h and subsequently ground into powder.

A 30 g sample of the MCC powder was dispersed in 600 mL of deionized water and 9.87 g sodium hydroxide was added while stirring at room temperature for 30 min. The cationic etherifying agent was then gradually added with continuous stirring and the molar ratio of sodium hydroxide to CHPTA was fixed at 1.2:1. The reaction mixture was stirred for 5 h at 65 ◦C and the resultant suspension was centrifuged at 5000 rpm for 10 min to obtain the precipitate. The precipitate was suspended in deionized water to remove CHPTA, then dried and ground into powder. The modified MCC is referred to as MD-MCC.
