Recyclable, self-healable and reshape vitrified poly-dimethylsiloxane composite filled with renewable cellulose nanocrystal

Traditional thermoset polymeric materials pose an enormous burden on the environment due to permanent covalent cross-links that make them difficult to reprocess or recycle. Herein, we describe the facile synthesis of recyclable, healable and reprocessable poly-dimethylsiloxane (PDMS)/cellulose nanocrystals (CNC) composites via engineering dynamic covalent bond (DCB) vinylogous urethane between the polymer-polymer and polymer-CNC. We successfully prepared the amine-modified CNC, evidenced by the analysis of FTIR, XPS and Element analysis , and its surface morphology as well as its size compared to the pristine one is not altered via XRD and TEM analysis . The DCBs are constructed not only between polymer chains, but also on the interface between polymer and CNC. Interestingly, the macromolecular cross-linker synthesized by RAFT polymerization significantly improves the mechanical properties of PDMS-based CNC vitrimer, without affecting its recycling and reprocessing properties. Remarkably, DCB vinylogous urethane endows this vitrimer good self-healing, reprocessing and recycling and this DCB can be effectively reshaped by the catalyst-free transamination of the vinylogous urethane through hot pressing or welding. It is emphasized that this macromolecular cross-linker containing β -keto acids obtained by RAFT polymerization can significantly broaden the application range for DCB vinylogous urethane. In general, this work could provide a facile approach to design and fabricate high performance renewable CNC based composites with excellent self-healing, reprocessing and recycling capabilities.