Fabrication of high-performance mixed-matrix membranes via constructing an in-situ crosslinked polymer matrix for gas separations

Abstract

• A binaphthyl-ether tetramine was designed using to form an in-situ crosslinked polymer matrix. • Desirable interfacial morphology and uniform dispersion of TiO 2 were obtained in MMMs. • Overall gas separation properties of MMMs containing 5–23 wt% of TiO 2 were maintained. In this work, a b i n aphthyl-ether t etr a mine (BNTA) monomer was designed, synthesized, and reacted with 6FDA to form an in-situ crosslinked polyimide (6FDA-BNTA). Then, novel mixed-matrix membranes (MMMs) were prepared by incorporating the titanium dioxide (TiO 2 ) nanoparticles into the 6FDA-BNTA polymer matrix to fabricate TiO 2 /6FDA-BNTA MMMs for gas separations. The desirable interfacial morphology and uniform dispersion of TiO 2 were obtained due to the nano-confinement effect and stronger hydrogen bond interactions between TiO 2 and 6FDA-BNTA when compared with these of their linear analogues as polymer matrixes. The pristine 6FDA-BNTA membrane and MMMs containing 5–23 wt% of TiO 2 had good mechanical properties, which possessed tensile strengths in the range of 65.2–116.6 MPa and elongation at break of 4.8–7.8%. Gas transport results further revealed that the overall performances of TiO 2 /6FDA-BNTA MMMs were maintained with the increasing of the TiO 2 loading content. Specifically, 6FDA-BNTA MMMs with TiO 2 loading of 23 wt% exhibited the highest gas permeability (e.g. PCO 2 = 376.2 Barrer, PO 2 = 76.3 Barrer) and moderate selectivity (e.g. αCO 2 /N 2 = 24.3, αO 2 /N 2 = 4.9), locating near the Robeson 2008 upper bounds very closely for O 2 /N 2 , H 2 /N 2 , and CO 2 /CH 4 gas pairs. This facile approach, aiming at improving the incompatibility between two phases via constructing an in-situ crosslinked polymer matrix, provides a new insight for rational design of high-performance MMMs.