Synthesis and characterization of bis (4-maleimidophenyl) fluorene and its semi interpenetrating network membranes with polyether imide (Ultem® 1000)

A semi-interpenetrating network (semi-IPN) of bis (4-maleimidophenyl) fluorene (cardo-BMI) and polyether imide (PEI, Ultem® 1000) was prepared. The structure of bis (4-maleimidophenyl) fluorene and the corresponding semi-IPNs was determined by nuclear magnetic resonance and Fourier transform infrared spectroscopy, respectively. The thermal properties of the cardo-BMI and semi-IPNs were evaluated by thermogravimetry and differential scanning calorimetry. The semi-IPNs exhibited thermal stability up to 480 °C. The morphology of the semi-IPNs was evaluated by scanning electron microscopy. Asymmetric membranes were prepared from the semi-IPN material by the wet phase inversion method. The pure gas permeation properties of the PEI and semi-IPN membranes were evaluated for oxygen (O2), nitrogen (N2), carbon dioxide (CO2) and methane (CH4) by the constant pressure and variable volume method at an absolute feed pressure of 0.69 MPa at 22 °C. The CO2/N2 selectivity of 39.2 ± 3.0 with a CO2 permeance of 18.3 ± 4.0 GPU of semi-IPN membrane was higher than the PEI membranes (selectivity 21.6 ± 4.1 and CO2 permeance 0.5 ± 0.1 GPU). The highest CO2/CH4 selectivity of the semi-IPN membrane was 49.3 ± 3.5 compared to 37 for a PEI dense film. Among the semi-IPN membranes, those with 5 wt% cardo-BMI exhibited better performance than the 1% and 10%