Abstract
Most of ion-exchange membranes are formed by polymerization of styrene and divinylbenzene and then the ion-exchange groups are introduced into the membranes. During the polymerization process, the phaseseparation takes place and it is considered that the formed morphology affects the performance of membrane remarkably. Usually rubber component is added to the mixture of styrene and divinylbenzene in order to improve the brittleness of the membrane and this may induce the phase separation. In this study, the structure development during polymerization of styrene and divinylbenzene in the existence of rubber was measured by a light scattering, an optical microscope and a transmission electron microscope. A peak in the light scattering profile appeared and regularly phase-separated morphology was observed by optical microscopy. These results mean that the phase-separation into polystyrene-rich phase and rubber-rich phase took place via spinodal decomposition mechanism (polymerization induced phase separation). It was also suggested that the phaseseparated morphology can be controlled by changes of polymerization speed and miscibility between polystyrene and rubber. The phase-separated morphology of membrane polymerized in the existence of foundation cloth which consisted of poly (vinyl chloride) was also observed. It was found that the domain size of phase-separated morphology was remarkably different between inside and outside of foundation cloth.
