Block copolymer membranes based on polyetheramine and methyl-containing polyisophthalamides designed for efficient CO2 separation

A series of block copolymer membranes was designed using polyetheramine (PEA) and methyl-containing polyisophthalamides (MPA) for the separation of carbon dioxide (CO2)/methane (CH4) gas mixtures. PEA consists of abundant ethylene oxide units, which show good affinity with CO2, and MPA consists of methyl (Me) substituents, which can increase the fractional free volume of block copolymer membranes. The Me substituents were introduced into MPA via polymerization from isophthaloyl dichloride (IPC), 2,5-dimethyl-1,4-phenylenediamine (DPD), and 4,4′-bis(3-aminophenoxy)diphenyl sulfone (BADS). Therefore, the CO2 solubility and diffusivity in the membranes could be improved by tailoring the PEA/MPA mass ratio and BADS/DPD mole ratio, respectively. The membrane with a PEA/MPA mass ratio of 6/4 and a BADS/DPD mole ratio of 1/10 exhibited optimum CO2 separation performance with a CO2 permeability of 629 Barrer and CO2/CH4 selectivity of 23 at 2 × 105 Pa and 25°C.