Intrinsic viscosity‐molecular weight relationships for dextran

Abstract

Intrinsic viscosities of dextrans of known branching ratio were measured in water formamide, and in a water‐methanol mixture at two temperatures. Weight‐average molecular weights (sedimentation equilibrium) ranged from 1.1 × 104 to 1.7 × 106. A model for the hydrolyzed dextran molecule was assumed. Using the methods of Zimm and Stockmayer, the g factor calculated from this model was compared with the g factor obtained from the intrinsic viscosity‐molecular weight data through the use of the Flory‐Fox theory (g = ratio of squares of radii of gyration of branched to unbranched polymer). The calculated branch lengths required to make consistent the g factors obtained by two different routes were of the same order of magnitude as those found by classical organic chemical methods for other dextran preparations. The intrinsic viscosity‐molecular weight relation at 25°C. in water for linear dextran was predicted from the data. It is suggested that investigations of branched polymers of known constitution be carried out by these methods.

Preferential Solvation of Dextran in Water–Ethanol Mixtures

“…This behavior is similar to that in 40.5% aqueous methanol solution obtained by Wales et a!. (the broken line in Figure 3), 22 and indicates that the dextran chains in solution become more closely packed with increasing molecular weight and decreasing solvent power. The values of 1(2 ° and the partial specific volume, v2 °, in an aqueous solution, the compressibility of solute molecule, K2 , and the amount of bound water, w ( =n,v1) estimated from eq 2 are tabulated in Table I.…”

Rheological and microstructural properties of the chia seed polysaccharide

“…These values are comparable to that of fenugreek gum (16 dL g −1 ) [18] but much lower than for xanthan (87.5 dL g −1 ) [19]. Furthermore, the values are substantially higher than those of microbial and plant polysaccharides with similar functionality including levan (0.14-0.38 dL g −1 ) [14,20,21], dextran (∼1 dL g −1 ) [14,17], gum Arabic (0.18 dL g −1 ) [22], guar gum (12 dL g −1 ) [23] and locust bean gum (12.5 dL g −1 ) [24]. The high intrinsic viscosity of CSP indicates an open and relatively flexible structure with high solubility in water.…”

“…The viscosity of polysaccharides depends on the molecular size, intermolecular interaction, structural configuration of the molecules and the nature of the solvent used [17]. Usually, the viscosity increases with the increase in solid concentration due to enhanced interaction between neighbouring chains.…”

Interaction of nonionic dextrans with silver bromide hydrosols

“…However, because of the smaller size of dextran molecules in the methanol-water solvent (Table 2; also Refs. 28,29,30), the coagulation maximum appears at higher polymer concentration. In the presence of dextrans of lower molecular weights or in less concentrated sols somewhat more electrolyte is needed for sol destabilization than what remains in solution as a result of silver halide precipitation from AgNOa and KBr.…”