“…The peak at 973 cm –1 was attributed to –CH 3 rocking and C–C chain stretching. Additionally, a series of absorption peaks of moderate intensity (1170, 998, 841, and 809 cm –1 ) between 1300 and 800 cm –1 can be ascribed to the presence of helical arrangement of PP molecular chains, which correspond to the absorption peaks of isotropic polypropylene . In the case of the SM sample, new characteristic peaks appear at 1027, 1178, 1622, 1709, and 3425 cm –1 , corresponding to OSO asymmetrical stretch, OSO symmetrical stretch, CC stretch, CO stretch, and O–H vibration, respectively, further indicating the presence of oxygen-containing functional groups and cross-linking by the sulfonation process. , Figure S1a shows the XPS patterns of the waste mask and sulfonated samples, where the two peaks at 284.9 and 532.6 eV correspond to C 1s and O 1s, respectively.…”