Preparations of PDMS-grafted Aromatic Copolyamide Membrane Exhibiting High Durability and Processability

Abstract

The syntheses of siloxane-grafted polyamides were carried out by a macromonomer method, in order to develop a highly permeable and durable membrane material for pervaporation. A novel compounds, 3 ,5-bis(4-aminophenoxy)benzyloxypropyl-terminated polydimethylsiloxane (BAPB-PDMS), and 3,5-bis(4-amino-3-methylphenoxy)benzyloxypropyl-terminated polydimethylsiloxane (BAMPB-PDMS), were synthesized as macromonomers, which consisted of different PDMS segment lengths. The polycondensation of BAPB-PDMSs or BAMPB-PDMSs with terephthaloyl chloride yielded the desired siloxane-grafted polyamide copolymers, PA-g-PDMS and MPA-g-PDMS, respectively. The copolymer membranes were prepared by solvent casting method, and the gas permeability and pervaporation property of these membranes were evaluated. PA-g-PDMS was insoluble in any solvents after the copolymer was dried in vacuo, however, MPA-g-PDMS was soluble in solvents, such as tetrahydrofuran, chloroform and dichloromethane. Therefore, MPA-g-PDMS exhibited the higher processability than PA-g-PDMS. The gas permeability coefficients of these copolymer membranes were increased as increase of PDMS segment length, and these values of MPA-g-PDMS were slightly higher than those of PA-g-PDMS containing the same PDMS segment length. From the results of pervaporations of the dilute aqueous solutions of organic solvents, it was found that both of PA-g-PDMS and MPA-g-PDMS exhibited the excellent permselectivity toward several organic solvents, such as alcohols, acetone, tetrahydrofuran, chloroform, dichloromethane and benzene with a high and stable permeation.