PMMA or PEO in THF/H2O mixture: phase diagram, separation mechanism and application

The conditions for phase inversion and the desired phase separation mechani sm were selected by the phase behavior determined for the polymer/sol vent/ non-solvent. The mechanism of phase separation was investigated by light sc attering, from casting of homogeneous ternary solution (PMMA/THF/H2O). The liquid-liquid phase separation mechanisms via nucleation and growth (NG) ta ke place in this system. The growth constants K for different component con centrations were determined by intensity as a function of time at a chosen angle, and the high value was coincident with the experimental critical poi nt obtained by sol/gel ratio. The PEO/H2O/THF diagram was analyzed. The qua ternary homogeneous solution composition, close to the binodal curve, was e stimated from both phase diagram and the K value for casting or hexane coag ulation bath, and was obtained at the same order of magnitude as ternary sy stem. The membrane forming PMMA, with a small quantity of PEO, in coagulati on bath and air and water permeability for PMMA membrane, after removing th e PEO, was analyzed. (C) 2001 Elsevier Science B.V. All rights reserved.