Reprocessable Vanillin‐Based Schiff Base Vitrimers: Tuning Mechanical and Thermomechanical Properties by Network Design

Abstract

AbstractBio‐based polymer building blocks derived from abundant biomass represent a promising class of monomers for the synthesis of sustainable high‐performance polymers. Lignin‐derived vanillin is used as a bio‐based, aromatic molecular platform for chemical modifications. The use of vanillin aldehyde derivatives as monomers with different alkyl chain length, cured with bio‐based and less‐toxic di‐ and triamines, leads to covalent adaptable Schiff base networks and thus enables sustainable and thermally reprocessable high‐performance materials without using highly toxic amines. A process is presented to prepare homogeneous films of crosslinked materials that are thermally reprocessable while maintaining their mechanical performance. The network structures, mechanical properties, and thermal stability of the obtained polymeric sheets are characterized in detail. By systematically adjusting the composition of the network building blocks, the mechanical properties could be varied from tough materials with a high elastic modulus of 1.6 GPa to materials with high flexibility and elastomeric behavior with an elongation at break of 400%. Furthermore, the stress–relaxation behavior of stoichiometric and nonstoichiometric Schiff base vitrimers is investigated. The combination of bio‐based building blocks and the degradability of Schiff base networks under acidic conditions resulted in sustainable, environmentally friendly, chemically and thermomechanically recyclable vitrimers with self‐healing and shape‐memory properties.