Rheology of Charge-Modified, Soft Phytoglycogen Nanoparticles

Phytoglycogen (PG) is a natural polysaccharide produced in the form of compact, 44 nm diameter, electrically neutral nanoparticles in the kernels of sweet corn. Its highly branched, dendritic structure and soft, compressible nature leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition, and biomedical formulations. To tailor the particles to specific applications, it is often desirable to modify their properties. We consider the effect of covalently attaching positively charged glycidyltrimethylammonium chloride (GTAC) chemical groups to PG on the rheology of the particles, focusing on the zero-shear viscosity of GTAC-modified PG dispersed in water at different concentrations C. Dispersions of GTAC-modified PG were significantly more viscous than those of native PG and showed a much steeper increase in the zero-shear viscosity with increasing C. Additionally, the viscosity of GTAC-modified PG dispersions was sensitive to the addition of salts and decreased significantly with added NaCl. These results show that electrostatic interactions have a significant effect on the strength of the interactions between the particles and suggest new applications for GTAC-modified PG.