Solvent effects on polysaccharide conformation

Polymers are widely used in solution to provide structure and function, e.g., colloidal stability, delivery of actives, viscoelasticity, to a variety of products. Underlying these functions are inter- and intra-molecular interactions that depend greatly on the type of solvent used. We consider here the dilute solution viscosity of a common polysaccharide, dextran, in various solvents (water, formamide, dimethylsulfoxide, ethanolamine). The intrinsic viscosity of dextran T500 doubles as the solvent changes from water to ethanolamine. The observed effects on the polymer conformation are discussed in terms of intermolecular interactions and are correlated with a number of solvent properties, including dipole moment, surface tension, empirical parameter of solvent polarity E-T(N), and Hansen solubility parameters. The data discussed here intimate that hydrogen bonding is the most important contributor to the solubility of dextran in the examined solvents. The excellent solvent power of ethanolamine can be ascribed to its capacity to act as both hydrogen bond donor and acceptor. (C) 2009 Elsevier Ltd. All rights reserved.