Rheology of polysaccharide systems

Abstract

The transport properties and, specifically, the rheological behavior of real and complex materials such as polysaccharide systems can be significantly affected by several factors, mainly related to molecular and supermolecular features. Most of these factors are common to all polymeric systems, as they have universal character; others are peculiar to carbohydrate polymers. If we bear in mind the concepts discussed in §1.4, we can easily imagine for polysaccharides a variety of structural conditions much wider than that generally observed for synthetic polymers. On both molecular and supermolecular scales, polysaccharides possess special characteristics that reflect specific behavior so that different classes of materials can be identified.Let us consider the molecular scale first: at this level, the polymer backbone and its related features, such as its length in solution, shape, stitfuess and the eventual presence of ionizable groups, playa major role in determining the macroscopic properties of the system, including its rheology. Many of these molecular parameters correlate among themselves (e.g. chain stitfuess and length); others must be combined with external factors such as, for instance, the characteristics of the solvent medium. These latter may, in turn, exert an influence on the conformation adopted by the macromolecule in the medium itself, as well as on the possibility of forming supermolecular structures. In other words, changes in ionic strength, the nature of counterions, temperature or other solvent parameters may induce a conformational transition, thus modifying the hydrodynamic resistance of the macromolecule to flow. Also, if the polymer concentration is high enough, the variations described above may promote structural changes at a supermolecular level and, accordingly, modifications in the rheological behavior. Before leaving this brief comment on solvent characteristics we must mention the viscosity although, R. Lapasin et al. (eds.), Rheology of Industrial Polysaccharides: Theory and Applications

Rheological study of xanthan and locust bean gum interaction in dilute solution

“…In this study, the slope value of LBG alone was greater than unity. In dilute regimes, slope values greater than unity have been reported to be associated with random coil conformation (Lapasin & Pricl, 1995) or entanglement (Morris et al, 1981). In dilute regimes, slope values less than 1 have been reported to be associated with rod-like conformation (Lai & Chiang, 2002).…”

“…The data did not fit with the linear regression model. Lapasin and Pricl (1995) reported that neutral polysaccharides (i.e., LBG) exhibited linear plots of lower slope, whereas ionic polysaccharides (i.e., xanthan) displayed a sharp increase of the slope, possibly due to expanded coil dimensions and electrostatic repulsion between chain segments. Pals and Hermans (1952) reported that g sp C increased rapidly at greater dilutions in sodium pectate without salts.…”

An in situ gelling system for bone regeneration of osteochondral defects

“…The geometry used for the tests was a cross-hatch plate device (Haake PP35 TI: diameter = 35 mm), in order to reduce the extent of the wall slippage phenomena [22].…”

Solution Properties of Combretum Glutinosum (Habeil) Gum

“…where the υ constant used for this study equal 1.3 (Lapasin, R., et al, 1995). Table 1 shows the solubility of Gum Habeil increased with the solvent basicity directly, the high solubility of gum solution in sodium carbonate due to calcium ion depletion.…”

“…Standard methods were used to prepare soluble part, and deacetylated gum solutions (Le Cerf, D., et al, 1990, Lapasin, R., & Pricl, S., 1995.…”