*2.3. Synthesis of Poly(o-anisidine)/BaSO4 Nanocomposite*

The preparation of the poly(*o*-anisidine)/BaSO4 nanocomposites was carried out by following the method of poly(*o*-anisidine) polymerization. Two solutions were prepared, which were designated as solution A and solution B. For solution A, 0.246 g of *o*-anisidine monomer was added in 20 mL of HCl (1 M), along with 0.026 g of the DDPA and BaSO4 nanoparticles. The load percentage of the BaSO4 nanoparticles was changed for different composites (1, 3, 5, 7, and 10), as shown in Table 1. Then, solution A was sonicated for 10 min and placed to stir in an ice bath. Additionally, 20 mL of HCl and 0.246 g of APS were combined to create solution B (1 M). After that, solution B was continuously stirred into solution A while being introduced dropwise in an ice bath. The mixture was stirred for 2 h and kept overnight for stabilization. The greenish suspension was obtained and we proceeded to the centrifugation. The material was separated and washed with distilled water three times. Then, the material was dried in an electric oven at 80 ◦C for 6 h [17]. Similarly, other composites were prepared by varying the percentage of the BaSO4 nanofiller according to the above method. Finally, the materials were collected and subjected to the characterization.

**Table 1.** Scheme for nanocomposite preparation.

