Fully-biobased Monomers Containing Monopyrrolidone Ring Towards the Synthesis of Renewable Polyesters with High Tg and Hydrolyzable Closed-loop Recycling

The development of fully bio-based polyesters with distinguished performance and facile chemical closed-loop recycling in aqueous environment still faces a challenge. Herein, a series of N-substituted pyrrolidone carboxylic acid monomers (xPCA) were synthesized from renewable itaconic acid (IA) with six amino acids with solvent-free and water-catalyzed conditions. xPCA was polymerized with ethylene glycol to prepare biobased six homopolyesters with number average molecular weights (Mn) up to 37.8 kDa. These polyesters exhibited high glass-transition temperatures (Tg) in the range of 47.8-106.2 ℃. Among these, L-tryptophan imparts the highest Tg (106.2 ℃) due to the addition of the indole heterocycle, which was higher than that of most of the commercial polyesters, such as polyethylene terephthalate (PET). In addition, these amorphous polyesters display excellent UV shielding properties with UV shielding cut-off values up to 241-323nm. The pyrrolidone structure improves the hydrophilicity of the polyester, thereby promoting the chemical cycle using deionized water at 80 ℃ as the solvent and low-toxicity zinc acetate as the catalyst. The recovered monomer can be polymerized again to obtain the original polyesters, which still retains its original properties. In addition, this polyester exhibits significant tolerance to common organic solvents and possesses long-term stability in water. Overall, this series of fully bio-based polyesters realizes the greening of the whole chain from raw material synthesis, product preparation to recycling treatment.