Double-Network Formation and Mechanical Enhancement of Reducing End-Modified Cellulose Nanocrystals to the Thermoplastic Elastomer Based on Click Reaction and Bulk Cross-Linking

Abstract

In addition to being a renewable nanomaterial, cellulose nanocrystals (CNCs) exhibit a high specific modulus and are widely used as a reinforcing phase (filler) to improve the mechanical performance of polymeric materials. In these composite systems, the filler–matrix, filler–filler, and matrix–matrix interactions are critical factors that govern the mechanical properties of the composites. Inspired by the idea of combining these three interactions, we design a novel composite system of reducing an end-modified CNC-enhanced thermoplastic elastomer [styrene–butadiene–styrene copolymer (SBS)] with click reaction and bulk cross-linking. The strong linkage between the nanocrystals and SBS (filler–matrix) is first achieved by the thiol–ene click reaction induced by UV irradiation in the liquid compounding process, accompanied by the preservation of surface hydroxyl groups on nanocrystals and therefore the formation of a stable percolation network (filler–filler). The matrix–matrix network is further constructe...