Determination of the nonsolvent--polymer interaction parameter X l3 in the casting solutions

摘要

A new method to determine the nonsolvent--polymer interaction parameter X l3 in the casting solutions was developed. With the measured intrinsic viscosities of the polymer in the mixed solvents with different concentrations, the nonsolvent--polymer interaction parameter X l 3 could be calculated by the application of the formalism proposed by Campos et al. The values of X l3 in membrane-forming systems of nonsolvent/Nmethyl-2-pyrrolidone (NMP)/polyethersulfone (PES) were obtained by the proposed method. The nonsolvents used were water, l-butanol and diethylene glycol (DegOH). The stronger the nonsolvent, the higher the va1ue of X l3. ln addition, the concentration of the nonsolvent at the binodal curve increased with decreasing X l3. The binodal curves for these membrane--forming systems predicted from the Flory--Huggins theory with X l3 obtained by the proposed method were consistent with measured cloud point curves, which confirmed that the method proposed here was reliable.