Unperturbed molecular dimensions and the theta temperature of dextran in dimethylsulfoxide (DMSO) solutions

Summary The unperturbed molecular dimensions of dextran samples have been determined in dimethylsulfoxide (DMSO) solutions from intrinsic viscosity measurements at different temperatures. The unperturbed dimension parameter, K_o, has been calculated from extrapolation methods.The unperturbed root-mean-square end-to-end distance, 2>_o ^1/2, found for the polymer samples in DMSO solutions, indicate that the polymer coils are contracted. This distance varies from 3.25 × 10⁻⁷ cm to 2.94 × 10⁻⁷ cm for the sample T 40 and from 8.28 × 10⁻⁷ cm to 7.48 × 10⁻⁷ cm for the sample T 500, in the chosen solvent as the temperature is raised from 25°C to 45°C. In the system of dextran/DMSO, the long-range interaction parameter, B, was also determined and a significant decrease is observed between 25°–45°C. The theta temperatures, Θ, were obtained as Θ= 327.25 K, Θ= 327.41 K and Θ= 323.38 K from the temperature dependence of the interaction parameter in Kurata-Stockmayer-Fixman, Berry and Inagaki-Suzuki-Kurata equations, respectively. Received: 19 January 1998/Revised version: 9 June 1998/Accepted: 10 June 1998