Poly(1,12-dodecylene 5,5′-isopropylidene-bis(ethyl 2-furoate))-based sulfonated copolyesters: Effect of ionic groups and long chain aliphatic spacer on their thermo-mechanical properties, hydrodegradability and liquid water sorption

Poly (1,12-dodecylene 5,5′-isopropylidene-bis(ethyl 2-furoate)) has recently been introduced to the polymer field as an exceptionally flexible polyester derived from bio-based and cost-effective monomers. A partially sulfonated version of this polymer is prepared in this study by copolymerization with sulfonated isophthalic acid. A series of sulfonated bisfuranic-aromatic copolyesters PDDbF_XSI_Y, containing up to 50 mol% of sulfonated moieties was synthesized, for the first time, using the 1,12-dodecandiol as a comonomer. Their chemical structure was investigated by FTIR and NMR (¹H and ¹³C) spectroscopy. In terms of properties, these copolyesters showed high thermal stability (c.a. T_d,_max ≥ 350 °C), a low glass transition temperature and they were found to be amorphous up to 20 mol% of the sulfonated unit content. Hydrodegradability tests on PDDbF_XSI_Y films carried out under alkaline conditions revealed highly stable materials even with increasing amount of sulfonated units. In addition, the films exhibit good liquid water sorption, which increases as the amount of sulfonated groups decreases, following the opposite trend of previously reported sulfonated bisfuranic-aromatic copolyesters prepared using short-aliphatic chain diols. These properties are obviously related to the concurrently incorporation of a dodecylene chain and sulfonated groups in the same backbone, making it possible to generate new hydrolytically stable bisfuran-based polymers with a sorption feature.