NMR APPROACH TO PROPERTIES OF POLYMERIC MEMBRANES - KINETICS OF MEMBRANE FORMATION

Nuclear magnetic resonance (NMR) is used to characterize properties of polyetherimide membranes obtained from a phase inversion process. At the end of the phase inversion and prior to the subsequent thermal tre atments, the membrane is made of a porous structure filled of solvent and nonsolvent molecules embedded in a concentrated polymer-solvent ma trix in the glassy state. The confinement of the small solvent and non -solvent molecules in the porous system leads to a restriction of thei r mobility. The kinetics of membrane formation is observed from NMR. I t is found that the penetration of non-solvent and the propagation of the glassy phase into the system obey simple diffusion laws. (C) 1993 John Wiley & Sons, Inc.