New Materials for Gas Separation Applications: Mixed Matrix Membranes Made from Linear Polyimides and Porous Polymer Networks Having Lactam Groups

A set of mixed matrix membranes (MMMs) has been prepared by incorporating a triptycene-isatin porous polymer network (PPN) to three aromatic polyimides (one commercial, Matrimid, and two synthesized by us: 6FDA-6FpDA and 6FDA-TMPD) covering a wide range of performances for gas separation. The triptycene-isatin PPN is a highly microporous network having a high CO2, uptake and high chemical and thermal stability. The good compatibility between the components (PPN content of 15 and 30% w/w) was supported by the increase in the glass transition temperature of MMMs relative to the pure polyimide membranes. The addition of the PPN particles improved the permeability of all the gases tested, by increasing diffusivity and, in some cases, gas solubility. The improvements were particularly noticeable in Matrimid-based MMMs, where gas permeability increased by 700%, whereas CO2/N-2 and CO2/CH4 ideal selectivities decreased by a mere 4% and 12%, respectively.