A novel method of preparing ultrathin poly(ether block amide) membranes

摘要

This work deals with a new method of preparing ultrathin poly(ether block amide) 2533 membranes based on spontaneous spreading of a solution of the block copolymer on a water surface. The casting solution used comprised of the copolymer dissolved in a solvent blend (isopropanol-butanol, weight ratio 3:1). During the solution spreading, solvent exchange with water occurs which induces polymer precipitation, thereby forming a thin membrane floating on the water surface. The spreading process is accompanied by evaporation of solvent due to its volatility, but the solvent-nonsolvent exchange is primarily responsible for polymer desolvation during membrane formation. The formation of a uniform and defect-free membrane was found to be determined by the solvent system, polymer concentration in the casting solution and temperature. Substantially defect-free membranes as thin as 0.3 μm were prepared. The membranes were tested for gas permeation, and it was shown that the membranes could be used for CO_2/N_2 and O_2/N_2 separations that are relevant to greenhouse gas emission control. At 25 ℃ and a feed pressure of 345 kPa, a carbon dioxide permeance of 350 GPU and a CO_2/N_2 permeance ratio of 35 were obtained with a 0.7 μm thick poly(ether block amide) membrane.