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

The interaction parameter χ was evaluated through the sum of the individual values of enthalpy and entropy dilution parameters, χH and χS, for different molecular weights of dextran samples. Subsequently, ((1/2)−χ) versus temperature relation yielded the theta temperature interpolated to 316.5±0.3 K. Similarly, the dependence of second virial coefficient, A2, on temperature was also studied from which another theta temperature was determined equal to 317.0±0.5 K. These two individual theta temperatures evaluated via interpolation methods employing interaction parameter and second virial coefficient were quite in accordance with that calculated as 317.2±0.6 K from intrinsic viscosity measurements achieved between the temperature intervals of 25°C and 43°C for the same system, previously.