The important role of thermodynamic interaction parameter in the determination of theta temperature, dextran/water system

The interaction parameter chi was evaluated through the sum of the individu al values of enthalpy and entropy dilution parameters, chi (H) and chi (s), for different molecular weights of dextran samples. Subsequently, ((1/2) - chi) versus temperature relation yielded the theta temperature interpolate d to 316.5 +/- 0.3 K. Similarly, the dependence of second Virial coefficien t, A(2), On temperature was also studied from which another theta temperatu re was determined equal to 317.0 +/- 0.5 K. These two individual theta temp eratures evaluated via interpolation methods employing interaction paramete r and second virial coefficient were quite in accordance with that calculat ed as 317.2 +/- 0.6 K from intrinsic viscosity measurements achieved betwee n the temperature intervals of 25 degreesC and 43 degreesC for the same sys tem, previously. (C) 2001 Elsevier Science Ltd. All rights reserved.