Abstract
Polyimide membranes have been widely investigated in gas separation applications due to their high separation abilities, excellent processability, relatively low cost, and stabilities. Unfortunately, it is extremely challenging to simultaneously achieve both improved gas permeability and selectivity due to the trade-off relationship in common polymer membranes. Diamine modification is a simple strategy to tune the separation performance of polyimide membranes, but an excessive loss in permeability is also generally observed. In the present work, we reported the effects of diamine type (i.e., non-fluorinated and fluorinated) on the physicochemical properties and the corresponding separation performance of a modified membrane using a commercial Matrimid® 5218 polyimide. Detailed spectroscopic, thermal, and surface analyses reveal that the bulky fluorine groups are responsible for the balanced chain packing modes in the resulting Matrimid membranes compared to the non-fluorinated diamines. Consequently, the modified Matrimid membranes using fluorinated diamines exhibit both higher gas permeability and selectivity than those of pristine Matrimid, making them especially effective for improving the separation performance towards H2/CH4 and CO2/CH4 pairs. The results indicate that the use of fluorinated modifiers may offer new opportunities to tune the gas transport properties of polyimide membranes.
Highlights
Membrane-based gas separation has drawn significant interest as an energy-efficient process to supplement or alternate the conventional thermally-driven separation methods such as distillation and thermal/pressure-swing adsorption [1,2]
Given that the reaction occurs the investigated solid-state environment, the of a Matrimid membrane bythe p-phenylenediamine (p-PDA, to equal to DA0 in this work) diffusion of diamines across polyimide film is expected be sterically constrained, by comparing liquid-phase methanol-swelling-induced post-treatment protocols which increases as the stericand hindrance increases as the reaction occurs [31,38,39]. They concluded that the Matrimid membrane modified by methanol-swelling protocol exhibited poor solvent resistance due to the surfacesurface due to their difficulties permeating through the polymer chains, which causes limlimited reaction on though the membrane surface with the ited reactivity even the existence of compared methanol assists theliquid-phase diffusion of protocol diaminesthat by induced the crosslinking of at thethe entire membrane, including the inner side
We explored the effects of fluorinated diamines in modified Matrimid® 5218 membranes, which is a representative commercial polyimide
Summary
Membrane-based gas separation has drawn significant interest as an energy-efficient process to supplement or alternate the conventional thermally-driven separation methods such as distillation and thermal/pressure-swing adsorption [1,2]. Among a myriad of polymer candidates, such as polymers adopted in commercialized membrane systems (e.g., polysulfone, polyethersulfone, cellulose acetate, and silicon rubber) [10], polyimide has been of interest for decades [11] This is because aromatic polyimides generally exhibit high diffusivity selectivity, desirable physical properties, and outstanding thermal/chemical stabilities, which are mainly attributed to their rigid backbone structure [12,13,14]. It was revealed that the fluorinated analogs exhibit higher gas permeability than their hydrocarbonbased control groups, as governed by the accelerated diffusion of gas molecules through the greater extent of void space induced by bulky fluorine groups Considering all these issues, we first report the role of fluorinated diamines in the modified polyimide membranes with a focus on the combined effects of bulky fluorine moiety and diamine-induced crosslinking. The structural properties were examined in detail to elucidate the unique gas transport properties of modified membranes using fluorinated diamines
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
