"Structure and Dynamics of Aqueous Dispersions of Highly-Branched Monodisperse Phytoglycogen Nanoparticles"
Phytoglycogen is a natural, monodisperse, dendrimeric nanoparticle that can be isolated from corn. Formed from glucose monomers, these particles are highly hydrophilic, leading to a number of advantageous properties such as high water retention, low viscosity, and extraordinary stability in water. In this thesis, we use neutron scattering to study the structure and dynamics of aqueous dispersions of phytoglycogen to better understand and exploit the intimate relationship between water and phytoglycogen. Small angle neutron scattering measurements allowed us to determine the radius of the phytoglycogen nanoparticles (17.4 ± 1.6 nm), establish the inter-particle spacing as a function of concentration, and obtain an estimate of the hydration of the particles (nH = 15.8 per monomer). These measurements indicated a particle of uniform density, with no indication of molecular crowding up to a concentration of 22.4% w/w. This result is consistent with the observation of low viscosity of phytoglycogen dispersions at lower concentrations. Quasielastic neutron scattering measurements provided detailed information regarding the dynamics of water in these dispersions, showing that the translation of the hydration water was subdiffusive and providing an additional value for the hydration of the particles (nH = 13.9 ± 2.3 per monomer). These results indicate that the number of water molecules associated with the phytoglycogen particles per monomer is comparable to that of free glucose units. When considered as a particle, there are approximately 1.9 million water molecules associated with each phytoglycogen nanoparticle (150%-175% of its own mass).
Dr. Hermann Eberl, Chair (Department of Mathematics and Statistics)
Dr. John Dutcher, Advisory Committee (Department of Physics)
Dr. De-Tong Jiang, Advisory Committee (Deparment of Physics)