Unexpected irregular structures of poly(itaconic acid) prepared in Deep Eutectic Solvents

Poly(itaconic acid) (PIA) was synthesized by persulfate initiated free-radical polymerization of ternary Deep Eutectic Solvents (DES) containing equimolar amounts of itaconic acid (IA) as hydrogen-bond donor, quaternary ammonium salt, namely choline chloride (CC) or tetraethylammonium chloride (TEAC) as hydrogen-bonds acceptors, and water as the initiator solvent. The syntheses were carried out at 65 °C for 2 h, and polymers produced were purified by dialysis and by treatment on strong cation exchange resin. The microstructures of the polymers were analysed using 1H, 13C and 1H–13C HSQC NMR spectroscopy. The unexpected methylene and methine groups resulting from decarboxylation and/or branching as well as choline ester moieties were detected as irregular structures in PIA synthesised in IA-TEAC and IA-CC DES, respectively.