Application of CH4/N-2 separation based on poly(styrene-b-isoprene-b-styrene) (SIS)-poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-co-PMHS) crosslinked membrane

This work involves the preparation and characterization of poly(styrene-b-isoprene-b-styrene)-poly(di-methylsiloxane-co-methylhydrosiloxane) (SIS-c-PDMS-co-PMHS) crosslinked membranes towards CH4/N-2 separation. SIS-c-PDMS-co-PMHS was synthesized via a simple hydrosilylation reaction with various PDMS-co-PMHS contents. The structure of crosslinked membranes was investigated by Fourier transform infrared spectroscopy, indicating the degree of hydrosilylation reaction. The morphology of sample membranes was observed in detail by means of Scanning Electron Microscope analysis. Thermodynamic stability and the crosslinked behavior of crosslinked membranes were explored by thermogravimetric analysis and Soxhlet extraction experiments. Furthermore, single gas (CH4, N-2) permeability was measured using the time-lag method. The CH4 permeability of crosslinked membranes with 70 wt% PDMS-co-PMHS could reach 503 Barrer at 25 degrees C and 1 bar, which is significantly greater than that of SIS (25.9 Barrer), while the CH4/N-2 ideal selectivity hardly changed. Notably, CH4 permeability further improved by 77.6% (893.4 Barrer) as the temperature increased to 55 degrees C. For the CH4/N-2 (50/50 vol%) mixed gas, the SIS-c-PDMS-co-PMHS-70 sample membrane exhibited ideal gas separation performance relative to that of the pure SIS membrane (CH4: 447.4 vs. 24.2 Barrer, N-2: 188.1 vs. 9.46 Barrer).