Largely enhanced water responsive sensitivity of ENR composites by simultaneously introducing cellulose nanocrystals and fibrillar silicate

In this study, water-responsive elastomer nanocomposites were designed and prepared by simultaneously introducing cellulose nanocrystals (CNCs) and fibrillar silicate (FS) into epoxidized natural rubber (ENR) via latex compounding followed by in-situ drying and filming. The simultaneous presence of CNCs and FS reduces the dense packing of both FS and CNCs because the initial dispersion of FS and CNCs in the latex is homogeneous and mutually separated, and the interaction between FS and CNCs is weaker than that between CNCs. More importantly, the longer FS forms network framework, and some of the shorter CNCs are assembled with FS through hydrogen bonding interaction, forming the much stronger network in CNC/FS/ENR composites. As a result, CNCs and FS show a synergistic effect on the water-responsive sensitivity. Among various ENR composites with the same volume fraction of fillers, 2CNC/4FS/ENR composite exhibits the strongest network, and its storage modulus and reversible water responsive sensitivity are approximately 11.5 times and 3 times that of 6CNC/ENR composite, respectively.