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

ABSTRACT 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.