Thermodynamic Criterion for Solubility

Solubility is achieved only if AG ix 0 the starting components (polymer and solvent) should have a higher free energy relative to that of 

If a nonsolvent such as methanol is gradually added to a homogeneous solution of a polymer in a good solvent (such as polystyrene in chloroform) the negative value of AG wiU decrease correspondingly, until the special situation of AG = 0 (i.e., = TA mix). called the (theta) 0-condition, 

---