Flexible Bioinspired Ternary Nanocomposites Based on Carboxymethyl Cellulose/Nanoclay/Graphene Oxide

Nacre is a prime example of a natural nanocomposite and an ideal motivation for nacre-mimetic materials. Natural nacre is a ternary nanocomposite made of aragonite platelets/chitin nanofibrils/protein and exhibits a combination of high tensile strength, stiffness, and toughness. Inspired by nacre, we developed ternary-bioinspired nanocomposites based on sodium carboxymethyl cellulose (CMC)/nanoclay platelets (SUM)/graphene oxide (GO) nanosheets via a water-borne evaporation-induced self-assembly technique. Structural characterizations of the layered nanocomposite films were done by FE-SEM, EDS, FTIR, RAMAN, XRD, and XPS. The mechanical properties of the nanocomposites were studied using a universal tensile tester, and the thermal behavior was analyzed using TGA. These ternary nacre-mimetics demonstrate high strength and flexibility via synergistic toughening from nanoclay platelets and graphene oxide as well as efficient interfacial stress transfer. The best synergistic improvement was obtained with CMC/SUM/GO-II ternary nanocomposite exhibiting a tensile strength, Young's modulus, and toughness of 105 ± 12 MPa, 9.4 ± 0.3 GPa, and 6.2 ± 1.3 MJ/m3, respectively. These reported values are much superior to those of their corresponding binary (CMC/SUM and CMC/GO) nanocomposites as well as other previously reported un-cross-linked polymer/nanoclay or polymer/GO binary layered nanocomposites. Moreover, the tensile strength and toughness of CMC/SUM/GO-II nanocomposites are simultaneously 1.3 and 3.5 times higher as compared to natural nacre. In terms of functionality, these nanocomposites have shown shape-persistent, fire-blocking, and self-extinguishing properties. Hence, our study provides useful guidelines for designing and constructing future high-performance ternary-bioinspired materials, which can be applied as self-standing, ecofriendly, strong, and flexible materials for various applications like aerospace, flexible electronics, structural, and barrier materials.