2.2.1. Pectin–Chitosan Polyelectrolyte Complexes in Water: PC15 W, PC11 W, PC51 W

To prepare the 1:5 pectin/chitosan composite (PC15 W), the 2 wt % chitosan solution was prepared by dissolving chitosan (ca. 2 g) into 98 g of acetic acid (2 wt %), and the pectin solution was prepared by dissolving of pectin (ca. 1.37 g) into 68.6 g of deionized water to make a 2 wt % solution. In a 150 mL beaker, 50 g of the 2 wt % chitosan solution was mixed with 10 g of the pectin 2 wt % solution at 23 ◦C with a magnetic stirrer at 1000 rpm overnight. The mixture was neutralized with 1M NaOH (*aq*) 12 h after the mixing step until pH 7 to yield a suspension of pectin–chitosan particles. The pectin–chitosan composite precipitate was filtered by a vacuum pump with Whatman 42 ashless filter paper and washed with deionized water, where the filtrate reached a low conductivity (35 μS/cm). The final products were air-dried for 48 h. Procedures for making PC11 W and PC51 W were similar to the previous procedures to obtain the PC15 W products, except the relative amount of pectin and chitosan was varied to achieve the different weight ratios accordingly.

2.2.2. Sonication-Assisted Synthesis of Pectin–Chitosan Composites in DMSO: PC15 S DMSO, PC11 S DMSO, and PC51 S DMSO

To prepare PC15 S DMSO, pectin (ca. 1.5 g) and chitosan (ca. 7.5 g) were dispersed in DMSO (200 mL). The pectin and chitosan mixture in DMSO was sonicated for 10 min. After cooling, the brown-dark pectin/chitosan composites were filtered and dried in the fume hood at 23 ◦C. The preparation of the PC11 S DMSO and PC51 S DMSO composites were similar to the above except that pectin (ca. 2 g and 7.5 g) and chitosan (ca. 2 g and 1.5 g) were suspended in DMSO (200 mL).
