Theoretically yes. But practically? The melting point depression depends on the melting enthalpy, the mole fraction of the solute, and the nonideality of the solution. The chi parameter influences the latter. But as you are using a polydisperse material, you may have to find out how much of it is really crystalline or in a glass state, melting takes place over a temperature range, and you may have to find out the molar mass distribution of your material before you can “isolate” the solution nonideality from the other effects. This does not sound very practical.

Usually chi is calculated from the temperature of the liquid–liquid phase split, which is directly related to solution nonideality.

But you can answer your question yourself by performing DSC runs on your polymer with different solvents. If you see a significant difference, there is a chance to obtain chi from the DSC traces.

This looks make sense, thank you verymuch Ulrich. In fact I was thinking of this, and have already tried different solvent systems, and the good news is that there is a significant difference but how find chi, this is the controversial issue. Do you think I can use the pure PVDF equilibrium temp. As To, or I need to find it for my PVDF?

Thanks again and I really appreciate it if you can give me your opinion about this issue.

Cheers

Ra'id