Characterization of the conformation and comparison of shear and extensional properties of curdlan in DMSO

Abstract

Five samples of curdlan, a kind of bioactivated polysaccharide of 1,3-beta- d-glucan, ranging in molecular weight from 5.1 × 10 4 to 192 × 10 4, were used to determine their conformational parameters and molecular dimensions in DMSO at 25 °C. Mark–Houwink equation was established as [ η ] = 4.8 × 10 − 4 M w 0.65 . On the basis of unperturbed worm-like chain models, the molecular parameters were estimated as follows: molecular mass per unit contour length M L = 694 nm −1, persistence length q = 5.81 nm, molecular diameter d = 0.99 nm, and characteristic ratio C ∞ = 9.58 , these suggesting that this polysaccharide exists as a relatively extended flexible chain in DMSO. The molecular association and rheological properties of curdlan in DMSO were also investigated. Curdlan in DMSO is capable of forming three-dimensional weak network involving DMSO above a critical curdlan concentration due to the formation of polymer–DMSO polymer and polymer–polymer hydrogen bonds. The extensional viscosity characteristics of curdlan in DMSO in semi-dilute regime were determined and compared to the shear properties of the solutions.