This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
PBICondensation. en Scheme of polycondensation of ' 'tetraaminobiphenyl with isophtalic acid yielding polybenzimidazole PBI own Spiperon Condensation polymerization
Page 2023 Free-images.com. All images are Public Domain