Vanillin-based liquid crystalline polyimine thermosets and their composites for recyclable thermal management application

The development of bio-based thermosets with favorable mechanical properties, high glass transition temperature (Tg), and recyclability for thermal management applications remains a huge challenge. In this study, a trifunctional aldehydes monomer was prepared from vanillin followed by curing with two kinds of diamine for novel polyimine networks. The results showed that the polyimine networks cured with 4,4′-diaminodiphenyl methane demonstrated the liquid crystalline polyimine thermosets with a high Tg of 193 °C, a high tensile strength up to 84 MPa, and excellent thermal stability (the values of degradation temperature for 5 wt% weight loss, Td5 = 373 °C), while the polyimine networks cured with 4,4′-methylenebis(cyclohexylamine) demonstrated amorphous polyimine thermosets with inferior mechanical and thermos-physical performances, due to the crosslinked liquid crystal structure, the rigid benzene ring and the π-π stacking effect of the former. Furthermore, the polyimine nanocomposites were constructed by incorporating graphene nanoplatelets (GnPs) into these bio-based thermosets. With only 8 wt% GnPs, the nanocomposites showed a remarkable thermal conductivity of 1.8 W m−1 K−1. Interestingly, both the polyimine networks and their composites demonstrated complete recyclability in mild acid conditions owing to the existence of dynamical Schiff-base structures. The bio-based polyimines and nanocomposites reported here offer various advantages, including high mechanical properties and Tg, excellent thermal stability, remarkable thermal conductivity, and recyclability, which provides a new direction for the development of high-performance base composite networks.