Fine-tuning the molecular structure of binaphthalene polyimides for gas separations

Abstract

A set of new stiff and contorted polyimides were prepared to systematically link polymer structure with gas separation properties. Seven novel bridged binaphthalene polyimides were synthesized for this purpose using commercial dianhydrides pyromellitic dianhydride (PMDA), biphenyl-tetracarboxylic acid dianhydride (BPDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). From these polyimides, freestanding membranes were prepared and tested on mixed gas CO2/CH4 and CO2/N2 separation performance. They were further characterized using WAXS and PALS and through the simulation of their free volume elements (FVEs) and gas separation properties. The binaphthalene polyimides had CO2/CH4 and CO2/N2 mixed gas selectivities of respectively 40 and 29 and mixed gas permeabilities of about 20 barrer for both gas mixtures.

2,2′‐Tethered Binaphthyl‐Embedded One‐Handed Helical Ladder Polymers: Impact of the Tether Length on Helical Geometry and Chiroptical Property

“…The average binaphthyl dihedral angles ($${\overline \theta }$$ in Figure 6) of poly‐ 5S C1 , poly‐ 7S C2 , and poly‐ 9S C3 increase with the tether length and are found to be ca. 57°, 66°, and 74°, respectively, which are roughly comparable to those of the recently reported 2,2'‐alkylenedioxy‐tethered 1,1′‐binaphthyl derivatives [10c,11d,e,13f] . All three ladder polymers have an ( M )‐handed macromolecular helicity due to the same axial chirality of the ( S )‐1,1′‐binaphthyl moieties, but differ in the helical geometries, including the helical pitch (2.6–2.9 nm), helical diameter (2.5–2.7 nm), and the number of repeating units per helical turn (2.9–3.4) as well as the groove structure.…”

Phthalide-containing poly(ether-imide)s based thermal rearrangement membranes for gas separation application

“…In order to increase the free volume of PI, some feasible methods have been proposed, including the introduction of bulky Cardo structure, triptycene group, large volume substituent and contorted linkage. [15][16][17][18][19][20] For instance, the introduction of bulky Cardo group can increase the interchain distance, reduce the interaction between molecular chains, and form more free volume, which is conducive to the transportation of gas molecules. Meanwhile, rigid macromolecular chains are always preferred for gas separation membranes to maintain high gas selectivity.…”

Preparation and gas separation performance of polyimide membranes endcapped with ionic liquid-type structures

“…5 Consequently, a great deal of attention has been focused on improving the selective permeability of polyimide membranes, including chemical or physical modifications. An important method for enhancing the performance of polyimide membranes is the adjustment of the monomer's chemical structure, such as by introducing a kink, [6][7][8] screw ring, 9,10 cardo, 11,12 side groups (-CF 3 ), 13,14 and bulky, [15][16][17] or changing the configurations of different spatial connections. 18 In telechelic polyimides, [19][20][21][22][23][24] the groups that can interact with the gas are attached to the two ends of the polymer's main chain, so the polymer has an end-capping effect.…”