Mechanical Strong and Recyclable Rubber Nanocomposites with Sustainable Cellulose Nanocrystals and Interfacial Exchangeable Bonds

Rubber is a strategically important polymeric material because of its high extensibility and resilience. However, traditional cross-linked rubber is difficult to be reprocessed or recycled due to the permanent covalent cross-linking, which puts a huge burden on the environment. Herein, we report a covalently cross-linked yet reprocessable carboxylated styrene butadiene rubber (CSBR) nanocomposite which is reinforced and cross-linked by epoxy-modified tunicate cellulose nanocrystals (TCNCs). The epoxy modification of TCNCs improves the dispersibility and the interfacial interactions with the matrix, thus improving the mechanical properties of the nanocomposites. In addition, exchangeable ester bonds are formed at the rubber–filler interface, and the network topology can be rearranged via the transesterification reactions. Therefore, the materials can be reprocessed and recycled under the evaluated temperatures. In particular, by introducing metal coordination bonds to construct a dual dynamic network in the system, the mechanical properties of the nanocomposites can be further improved without compromising the recycling and reprocessing performance.