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

Five samples of curdlan, a kind of bioactivated polysaccharide of 1,3-beta-d-glucan, ranging in molecular weight from 5.1 × 104 to 192 × 104, were used to determine their conformational parameters and molecular dimensions in DMSO at 25 °C. Mark–Houwink equation was established as [η]=4.8×10−4Mw0.65. On the basis of unperturbed worm-like chain models, the molecular parameters were estimated as follows: molecular mass per unit contour length ML = 694 nm−1, persistence length q = 5.81 nm, molecular diameter d = 0.99 nm, and characteristic ratio C∞=9.58C∞=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.