Bis-pyrrolidone structures as versatile building blocks for the synthesis of bio-based polyesters and for the preparation of additives

In this work, three bis-pyrrolidone-based structures (BP) were synthesized combining dimethyl itaconate (DMI), the dimethyl ester derivative of itaconic acid, with various aliphatic diamines having a C4 to C12 carbon chain length with the aim of developing novel bio-based building blocks. All three BPs were obtained with a purity >93% and could further be used without performing any tedious purification step, therefore allowing an easy scalability of the synthesis on a 10 g scale. Their potential application was demonstrated in two key areas of modern polymer science: (1) the enzymatic synthesis of polyesters and (2) their use as poly(lactic acid) (PLA) additives. Firstly, the possibility of obtaining oligoesters by reacting the BP monomers with various aliphatic diols in a solventless reaction system and under mild conditions (T < 90 °C) was demonstrated thanks to the use of enzymatic catalysis. Linear oligoesters having mean average molecular weights between 1000 g mol−1 and 6100 g mol−1 and dispersity values <2 were successfully obtained. When applying the BP structures as PLA additives, the incorporation of a 10% w w−1 BP in the polyester matrix resulted in systems with an 8× increased elongation at break and a decrease in the glass transition temperature compared to the neat polymer matrix.