Unperturbed dimensions and the theta temperature of dextran in aqueous solutions

Intrinsic viscosity measurements were carried out on dextran samples (of different molecular weights) in aqueous solutions at 25, 28, 31, 34, 37, 40, and 43°C. The extrapolation methods were used for the data; they gave unperturbed dimensions, K0, of the chain. The unperturbed root-mean-square end-to-end distance 〈r2〉[STACK]1/20[ENDSTACK] calculated for the polymer samples in water indicate that the polymer coils are slightly contracted in this solvent as the temperature is increased. The long-range interaction parameter, B, was also determined. In aqueous dextran solutions, this showed a significant decrease in the long-range interactions between 25 and 43°C. The values of Θ = 317.82 and 316.57 K were obtained from the temperature dependence of the interaction parameter B in the Kurata–Stockmayer–Fixman and Berry equations. Calculated values were interpreted mainly on the basis of hydrogen-bond formation between polymer segments and dextran–water molecules in solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 871–876, 1999