Role of molecular structure of monosaccharides on the viscosity of aqueous nanometric alumina suspensions

The effect of molecular structure of d-galactose, d-mannose, d-glucose, 2-deoxy-d-glucose and 3-O-methyl-d-glucose on the viscosity of aqueous alumina nanoparticle suspensions was investigated by rheological measurements. The viscosity was found to be dependant on the molecular structure of these hexopyranoses. The research reveals that the orientation of primary and quaternary hydroxyl groups in a pyranose ring plays a crucial role in dispersing properties of monosaccharides. Moreover, the most important is the mutual orientation of these hydroxyl groups. Monosaccharides with axial and equatorial orientation of hydroxyl groups at first (C1) and fourth (C4) carbon atom in pyranose ring decrease the viscosity more than monosaccharides with two axial hydroxyl groups in these positions. Due to the differences in molecular structure of saccharides resulting in different shape of molecules and different compatibility to the water structure, the saccharides differ in ability to disturb water layers around alumina particles.