PHASE-SEPARATION PHENOMENA OF POLYSULFONE SOLVENT ORGANIC NONSOLVENT AND POLYETHERSULFONE SOLVENT ORGANIC NONSOLVENT SYSTEMS

The precipitation values (PVs) of several organic nonsolvents in polys ulfone (PSf)/solvent and polyethersulfone (PESf)/solvent systems were measured in temperatures ranging from 10 to 80-degrees-C by the direct titration method and compared with those of water in the same systems . The solvents used were N-methyl-2-pyrrolidone (NMP) and NN-dimethyla cetamide (DMAC); the organic nonsolvents employed were methanol, ethan ol, I-propanol, 1-butanol, 1-pentanol, ethylene glycol, and diethylene glycol as well as acetic acid and propionic acid. The compositions of nonsolvent, polymer, and solvent at the precipitation points for diff erent polymer concentrations up to 10 wt % were also determined at 30- degrees-C with respect to both the polymers and six nonsolvents presen ted. These results were used to obtain the polymer precipitation curve s in the polymer-solvent-nonsolvent triangular phase diagrams and to d etermine the theta composition of solvent-nonsolvent for a polymer. Th e results show that the precipitation value of nonsolvent in polymer/s olvent systems depends on both the nature of polymer, solvent, and non solvent used and the temperature. The effect of temperature on the pre cipitation value was observed to be dramatically different for differe nt polymer/solvent/nonsolvent systems. These results were explained on the basis of polar and nonpolar interactions of the polymer, solvent, and nonsolvent system. The results indicate that the precipitation va lues of the type presented in this paper not only give a relative meas ure of the nonsolvent tolerance of the polymer/solvent system involved and the strength of solvent and nonsolvent for the polymer, but also determine the relative location of the polymer precipitation curve in the triangular phase diagram. (C) 1993 John Wiley & Sons, Inc.