Biobased Unsaturated Polyester Resins Modified with Thiophene-2,5-dicarboxylic Acid

High Resolution Image Download MS PowerPoint Slide This study reports the first example of biobased unsaturated polyesters incorporating thiophene-2,5-dicarboxylic acid (ThDCA) as rigid structural units and their application in styrene-free thermosetting systems. The polyesters were synthesized using itaconic anhydride (IAn) as the source of unsaturation. Although IAn is known to isomerize into nonreactive citraconate species, this side reaction was negligible under the applied conditions, preserving reactive C═C double bonds essential for efficient cross-linking. Formulations in biobased dimethyl itaconate, serving as a reactive diluent and alternative to styrene, were successfully cured, confirming that incorporation of ThDCA does not hinder the curing process. The cured materials exhibited flexural strength up to 124.7 ± 15.4 MPa. Systematic variation of diol units in the polyester backbone enabled precise tuning of mechanical properties, with the diethylene glycol-based system showing the most favorable balance between strength and flexibility.