Reprocessable, Lignin‐Derivable, Non‐Isocyanate Polyurethane Covalent Adaptable Networks With Complete Recovery of (Thermo)Mechanical Properties

Reprocessable covalent adaptable networks (CANs) offer potential improvements in polymer life‐cycle management, yet balancing mechanical strength with reprocessability remains a critical challenge. Herein, the inherent structural features of a lignin‐derivable precursor, bisguaiacol A (BGA), were leveraged to develop a stiff, non‐isocyanate polyurethane (NIPU) CAN with (thermo)mechanical and reprocessability performance comparable to a bisphenol A (BPA)‐based counterpart. The NIPU CANs were prepared by reacting either a BGA‐ or BPA‐derived cyclic carbonate (BGACC or BPACC) with a trifunctional amine and cystamine to form crosslinked networks containing dynamic disulfide bonds. The methoxy groups in the BGACC‐CAN enabled significantly faster stress relaxation (∼3–5 times) than the BPACC‐CAN, with no loss in creep resistance. Furthermore, the aromatic lignin‐derivable monomer produced a CAN with tensile strength (∼45 MPa) and modulus (∼1.7 GPa) comparable to the petroleum‐derived analog (tensile strength ∼40 MPa, modulus ∼1.5 GPa). These BGA/BPA‐based CANs showed complete recovery of crosslink densities and essential (thermo)mechanical properties (e.g., glass transition temperatures, thermal stabilities, tensile strengths, moduli) after four reprocessing cycles via compression molding at 130 °C for 45 min. Overall, the lignin‐derivable cyclic carbonate explored in this work serves as a promising building block to design sustainable NIPU CANs that achieve structural robustness and reprocessability.