Preparation and Electrophoretic Deposition of Nanocrystalline Cellulose in Aqueous Media

The objective of this research project is to investigate the use of electrophoretic deposition to separate cellulose nanoparticles in water systems. Cellulose nanoparticles were selected in view of the fact that their properties are similar to other nanomaterials that are not easily detectable by simple methods of characterization. Hence, this material can be used as a model material in the development of characterization techniques for materials previously difficult to characterize. Development and optimization of the synthesis of nanocrystalline cellulose were of particular importance to the scope of this thesis. Two popular methods of synthesizing nanocrystalline cellulose (NCC) were investigated: ball milling (mechanical), and acid hydrolysis (chemical). Upon comparison of NCC particles from both methods, acid hydrolysis proved to be the optimum process due to the narrower distribution of NCC particles, higher yields, and stability with respect to suspensions in aqueous phases. Successful narrowing of size distribution of particles prepared by acid hydrolysis was conducted via differential centrifugation. Maximum yields of 65% were obtained upon analysis of the freeze dried NCC particles. Size readings of the resultant particles were measured using a transmission electron microscope (TEM) and the dynamic light scattering method (DLS). The lengths of the NCC whiskers ranged from 70 nm--300 nm, and widths from 15 nm--30nm. Zeta potential and electrophoretic mobility of the final suspension were also measured using a Malvern Zetasizer resulting in average values of -45.3 mV and -3.55 micromcm/Vs respectively. Investigation of the zeta potential at different pHs indicated the increased stability of NCC particles at neutral and basic pHs in water.;Stable suspensions were then used in electrophoretic deposition experiments using pulsed direct current (DC). Substrate surfaces were examined using Atomic Force Microscopy to observe the surface coverage, infrared spectroscopy to detect the molecular structure of the deposited film, and energy dispersive spectroscopy for the elemental analysis of the deposited film. The resulting spectra were synonymous with cellulose. Weight analyses of substrates were also employed to determine the amount of deposited material on substrate surfaces.;The data indicates that acid hydrolyzed NCC particles are very stable in water, with their stability increasing from low to neutral pHs. In addition, electrophoretic deposition using pulsed DC is a viable way of depositing NCC particles in aqueous media onto anodic substrates for separation and characterization. This technology can be used to develop on-line separation of nanoparticles from water to facilitate direct detection of the nanoparticles.