Date of Award
Doctor of Philosophy (PhD)
Cellulose has gained increasing attention due to its abundance and renewability. Obtained through a strong acid hydrolysis treatment of cellulose microfibrils, cellulose nanocrystals (CNCs) stand out among all hierarchical cellulose structures with appealing mechanical and optical properties that have been utilized as a reinforcing nanomaterial for the advanced material design. The cellulose nanocrystal graphene oxide (CNC-GO) nanocomposite film has been developed and successfully applied in portable and bendable sensing optoelectronics, energy storage and electromagnetic pulse protection devices. New material phenomena have been observed through experimental characterizations, but they lack fundamental understanding due to the experimental limitations in nanoscale. Therefore, a systematic and theoretical study at atomic level is desired to address the key factors responsible for the associated material properties of the CNC-GO nanocomposite, especially at its interface.
We adopt molecular dynamics (MD) simulation techniques to investigate the role of the hydrogen bonds in the CNC-GO interface interaction with respect to the CNC slab orientation, the CNC slab thickness, the GO oxidation type, and the water content at the interface. The objective is to understand the role of hydrogen bonds at the CNC-GO interface in CNC morphological variations and the mechanical property enhancement. We systematically investigate (1) the crystallography of the CNC-GO nanocomposites and their lattice parameter variations for the suppression of (200) facet in the X-ray diffraction (XRD) spectrum; (2) the hydrogen bond formation, types and distributions of the CNC due to the CNC-GO interface interaction; and (3) the mechanical property variations due to the interface hydrogen bonding of the CNC-GO nanocomposites.
Through systematic molecular dynamics simulations of a set of simplified CNC-GO sandwich structures, the mechanism behind local (200) facet manipulation, as well as the global morphological variations, can be elucidated. It will shed light on the correlations between interface types and mechanical loading responses along with the interface water molecules for the mechanical performance enhancement. This research provides an understanding of intrinsically manipulating the CNC-GO interface and potentially engineering the cellulose based nanocomposite materials and mechanical properties for future advanced materials development.
Mao, Qian, "A Molecular Dynamics Study of the Cellulose-Graphene Oxide Nanocomposites: The Interface Effects" (2018). All Dissertations. 2554.