Self-healing, recyclable, thermally adaptive shape memory functional biopolymers based on multiple dynamic covalent bonds and hydrogen bonds derived from castor oil and vanillin

Abstract

The development of recyclable biopolymers from renewable resources is of great importance to sustainable development and environmental protection. Biopolymers not only provide a platform for achieving a friendly environment, but also reduce dependence on fossil fuel elements. In this study, a castor oil-based macromolecule prepolymer containing reactive isocyanate groups was firstly synthesized, and next a series of recyclable bio-polymers containing dynamic Diels–Alder bonds, imine bonds and hydrogen bonds were designed and fabricated by the introduction of furfural derivatives and vanillin. Dynamic covalent bonds and hydrogen bonds can bestow biopolymers with excellent comprehensive properties, including high self-healing efficiency, shape memory and reprocessability. Meanwhile, the formation of a reversible cross-linked network of hydrogen and dynamic bonds significantly improved the mechanical properties and endowed the biopolymers with self-healing capability. Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance indicate the successful preparation of the biopolymers. Thermal gravimetric analysis demonstrates that the materials as-prepared possess high thermal stability. Mechanical tests show that the materials have excellent mechanical properties with a maximum stress of 36.44 MPa. Surface scratches can be repaired at 120 °C for 5 minutes. The biopolymers also exhibit shape memory properties. This work will contribute to the development and study of functional self-healing biopolymers.