Unperturbed dimensions and the theta temperature of dextran in ethylene glycol solutions

The unperturbed molecular dimensions of dextran samples (of different molecular weights) have been evaluated in ethylene glycol solutions from viscosity measurements at 25°C, 30°C, 35°C, 40°C and 45°C. The unperturbed dimension, K0, has been determined from extrapolation methods, i.e, Kurata–Stockmayer–Fixman (KSF), Berry and Inagaki–Suzuki–Kurata (ISK) equations. The hydrodynamic expansion factor, αη, as well as the unperturbed root-mean-square end-to-end distance, 〈r2〉01/2, found for dextran samples in ethylene glycol solutions, indicated that the polymer coils are contracted as the temperature is raised from 25°C to 45°C. The long-range interaction parameter, B, was also evaluated and a significant decrease is found for the dextran/ethylene glycol system between 25°C and 45°C. The theta temperatures, Θ, were determined as 328.53, 328.02 and 325.93 K from the temperature dependence of the interaction parameter, respectively.