Pebax thin film composite membranes for CO2 separation with the assistance of plasma treatment and Pluronic®F127 impregnation

Poly(dimethyl siloxane) (PDMS), as the gutter layer of multilayer composite membranes, could effectively avoid pore penetration of the selective layer. However, its inherent hydrophobicity is not conducive to the coating of selective layer materials. In this study, plasma treatment and Pluronic (R) F127 impregnation were used to improve the hydrophilicity of PDMS. Then Pebax (R) (30R51, 1657, and 2533) was used as selective layer materials for their excellent gas permeability and ideal separation factor to prepare thin film composite (TFC) membranes for CO2 separation. The hydroxyl groups were formed on PDMS by plasma treatment, while the hydrophilic PEO blocks were introduced by Pluronic (R) F127 impregnation, both of which changed their surface microstructure and composition, thus improving the hydrophilicity of PDMS. Their contact angle decreased from 98.44 degrees of the original PDMS to 79.40 degrees and 91.70 degrees, respectively. The increase in hydrophilicity of PDMS facilitated the preparation of defect-free TFC membranes and increased gas ideal separation factor. After adjusting the spin-coating speed to optimize the interaction between Pebax solution and PDMS, the CO2 permeance of PAN/S184-P/P30R51 and PAN/S184-S/P30R51 improved to 291.2 GPU and 448.3 GPU at 5000 rpm, respectively, and showed CO2/N-2 ideal separation factor of 41.3 and 33.8, respectively. Particularly, CO2 permeance of PAN/S184-S/P2533 increased to 659.4 GPU at 5000 rpm, while maintaining CO2/N-2 ideal separation factor of more than 20, which demonstrated the preparation of an ultra-thin selective layer.