Bio-Based and Chemically Recyclable Vitrimers from Poly(lactide) and Isosorbide Diglycidyl Ether

Abstract Bio-based and chemically recyclable vitrimer networks were synthesized from star-shaped poly(lactic acid) (PLA) oligomers and isosorbide diglycidyl ether (DGEIs). Hydroxyl-terminated 4- and 6-arm PLA oligomers were functionalized with carboxylic acid end-groups to improve reactivity with DGEIs. Crosslinking in the presence of Zn(OAc)2 at 180 °C yielded homogeneous thermoset films with high gel fractions (>90%). Rheological and DSC analyses demonstrated temperature-dependent curing kinetics and rapid network formation. Mechanical testing revealed high stiffness in the GPa range with relatively low elongation at break, consistent with a highly crosslinked PLA-based thermoset architecture. Dynamic mechanical analysis and stress relaxation experiments confirmed vitrimeric behavior governed by thermally activated transesterification reactions, with Arrhenius-type dependence of relaxation processes (Tv ≈ 110−115 °C, Ea ≈ 130−140 kJ mol−1, characteristic relaxation times on the order of tens of minutes at 180 °C). Beyond the primary vitrimeric response, the materials exhibited functional reprocessability: fractured samples could be successfully re-molded by hot pressing at elevated temperature, partially recovering mechanical integrity, in agreement with dynamic network rearrangement. In addition, shape memory and thermally induced shape recovery experiments demonstrated efficient programming and recovery at 90 °C, with high recovery ratios (>90%) maintained over multiple cycles. Surface wettability and stability studies highlighted differences between 4-arm and 6-arm architectures, while hydrolytic degradation experiments showed faster mass loss for 6-arm networks, particularly under alkaline conditions, consistent with higher solvent accessibility. Chemical recycling under alkaline hydrolysis enabled recovery of monomeric species, and proof-of-concept composite experiments demonstrated simultaneous recovery of both polymer matrix components and reinforcing carbon fibers. Overall, these results establish a fully bio-based vitrimer platform combining mechanical robustness, dynamic reprocessability, shape memory functionality, controlled degradability, and chemical recyclability.