Formation–structure–performance correlation of thin film composite membranes prepared by interfacial polymerization for gas separation

Thin film composite (TFC) membranes for CO2/N2 separation were prepared by interfacial polymerization from N-Methyldiethanolamine (MEDA) and Trimesoyl chloride (TMC) on crosslinked polydimethylsiloxane (PDMS) coating polysulfone (PS) support membrane. The structural properties of TFC membrane surfaces were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffractometer (XRD). The relationships among the skin layer formation conditions, skin layer structure, and membrane separation performance were investigated. Results show that membranes with higher CO2 permeance and good CO2/N2 selectivity appeared to consist of thinner, more crosslinked, and less crystalline skin layer structures. Such high performance gas separation membranes were obtained by (1) increasing MEDA diffusivity and decreasing MEDA solubility in the organic solvent, and (2) reducing TMC concentration in organic phase and raising MEDA concentration in aqueous phase under the circumstances of forming an integrated skin layer. Furthermore, our results also indicate that crosslinking could enhance the CO2-induced plasticization resistance of the membranes. These findings have great theoretical significance for the controlled preparation of gas separation membranes.