Facile Control of Reversible Diels–Alder Polyester Networks from Biobased Furan Cross-Linkers and Aliphatic Bismaleimides

Abstract

The synthesis of biobased covalent adaptable networks (CANs) is becoming increasingly popular as a sustainable alternative to thermosetting polymers since they are both recyclable and less dependent on petroleum chemicals. However, biobased CANs centered on the Diels–Alder (DA) reaction typically comprise the aromatic N,N′-(4,4′-methylene diphenyl) bismaleimide (BMI), which is toxic. Here, we synthesize less harmful aliphatic bismaleimides with varying molar mass and biobased multifunctional furan cross-linkers via facile procedures that achieve high conversion. These materials were subsequently copolymerized to prepare a range of thermally reversible cross-linked aliphatic polyester CANs with high gel fractions (88–98%). Structure–property relationships were established, showing that the compositions of the furan cross-linker and bismaleimide controlled the thermal and mechanical properties of the networks, leading to dissociation temperatures up to 136 °C and tensile strengths up to 9.3 MPa. Moreover, network recyclability was demonstrated via compression molding under mild conditions with very good recovery of mechanical properties (>75%), and the materials also displayed rapid healing. This research provides a facile approach to the smart design of recyclable biobased aliphatic polyester Diels–Alder CANs without the use of BMI, while achieving network properties that are tunable via the structures of the aliphatic bismaleimides and biobased furan cross-linkers.