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The Free Energy Landscape of Cellulose Nanocrystal Adhesion and Its Effect on Composite Strength

Sinan Keten (Northwestern University), Shawn Mishra ()

Materials Design and Biomimetic Material Concepts

Tue 2:40 - 4:00

Barus-Holley 158

Biopolymer based composites offer tremendous potential as sustainable, bionspired materials that have high mechanical performance and low cost. Cellulose nanocrystals can be extracted from a variety of sources such as plants and tunicates, and have high axial moduli, greater than that of even Kevlar. Additionally, their low density, transparency and an easily functionalized surface offer new capabilities for their use in nanocomposites and thin films. The interplay between the surface of the cellulose nanocrystal (CNC) fillers and the matrix plays a crucial role through interface and interphase effects that are challenging to capture with continuum modeling approaches. In this study, we use a non-equilibrium statistical mechanics approach combined with all-atom molecular dynamics simulations to determine the landscape of the cohesive energy between two CNC surfaces and between CNC and a polymer matrix. This cohesive energy gives a measure of the fracture strength per unit area at these interfaces, allowing for the prediction of the mechanism of failure and hydrogen bond cooperation. Analyses comparing tensile and shear deformations show strong dependence of the mechanical response on loading geometry. Our investigations provide new insight into CNC interfaces and pave the way for optimizing the shape and size of the CNC to generate functional nanocomposites and thin films with attractive mechanical properties.