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

The unperturbed molecular dimensions of dextran samples (of different molec ular weights) have been evaluated in ethylene glycol solutions from viscosi ty measurements at 25 degrees C, 30 degrees C, 35 degrees C, 40 degrees C a nd 45 degrees C. The unperturbed dimension, K-o, has been determined From e xtrapolation methods. i.e, Kurata-Stockmayer-Fixman (KSF), Berry and Inagak i Suzuki-Kurata (ISK) equations, The hydrodynamic expansion factor, alpha(e ta), as well as the unperturbed root-mean-square end-to-end distance, [r(2) ](o)(1/2), found for dextran samples in ethylene glycol solutions, indicate d that the polymer coils are contracted as the temperature is raised From 2 5 degrees C to 45 degrees C. The long-range interaction parameter. B, was a lso evaluated and a significant decrease is found for the dextran/ethylene glycol system between 25 degrees C and 45 degrees C. The theta temperatures , Theta, were determined as 328.53, 328.02 and 325.93 K from the temperatur e dependence of the interaction parameter, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.