PREPARATION AND STRUCTURES OF THE POLYVINYL-CHLORIDE) POROUS MEMBRANES

Formation of membranes from a binary system, poly(vinyl chloride) and dimethylformamide, was studied. Phase separation during membrane formation was caused by absorption of aqueous vapor from the atmosphere. The membrane structure was closely related to the degree of phase separation. The membrane formation process was divided into three stages, i.e., an early stage, a transitional stage, and a late stage. By leaching the solution at the early stage, where the casting solution was still transparent, a membrane with a finger‐like structure was obtained. On the other hand, a network structure was obtained by leaching at the late stage which was dependent on the molecular weight and the concentration of poly(vinyl chloride). The membrane structure was predominantly controlled by the mobility of polymer molecules in the casting solution. Copyright © 1979 John Wiley & Sons, Inc.