LIQUID CRYSTALLINITY OF A BIOLOGICAL POLYSACCHARIDE - THE LEVAN WATER PHASE-DIAGRAM

Boundaries on the phase diagram for aqueous solutions of levan (a branched polymer of fructose) were located quantitatively by transmitted light measurements performed with a UV-visible spectrophotometer. Data were collected in the range 10-70-degrees-C; the minimum concentrations required for separation of a liquid crystalline phase and the minimum concentration required for a fully liquid crystalline solution were identified within this range. The liquid crystalline nature of the anisotropic phase was confirmed by transmitted polarized light microscopy. The boundaries of the biphasic region (separated isotropic and anisotropic phases) are parallel, and they have a positive slope, suggesting that phase separation is dictated by hard rod interactions and that conformational disorder decreases the rod axial ratio with increasing temperature.