A novel trimethyl-substituted carboxyl-containing polyimide was synthesized by a one-pot high temperature polycondensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,5-diamino-2,4,6-trimethylbenzoic acid (TrMCA). The polyimide (6FDA-TrMCA) displayed Brunauer-Emmett-Teller (BET) surface area of 260 m 2 g-1 demonstrating intrinsic microporosity in contrast to the related low-free volume COOH-functionalized polyimide 6FDA-DABA. Compared to the non-functionalized 6FDA polyimide analog made from 2,4,6-trimethyl-m-phenylenediamine (TrMPD)also known as 6FDA-DAM-carboxyl functionalization in 6FDA-TrMCA resulted in reduced surface area, lower fractional free volume, and tighter average chain spacing. Gas permeabilities of 6FDA-TrMCA were typical of functionalized polyimides of intrinsic microporosity (PIM-PIs). For example, at 2 atm and 35 °C, 6FDA-TrMCA showed pure-gas H 2 and CO 2 permeability of 193 and 144 barrer coupled with H 2 /CH 4 and CO 2 /CH 4 selectivity of 61 and 45, respectively. Notably, in mixed-gas permeation tests with an equimolar CO 2-CH 4 mixture at 12 atm CO 2 partial pressure, 6FDA-TrMCA demonstrated performance located on the 2018 mixed-gas upper bound with a CO 2 permeability of ~ 98 barrer and CO 2 /CH 4 permselectivity of 38. As the first reported COOH-functionalized PIM-PI homopolymer, 6FDA-TrMCA revealed excellent resistance against CO 2-induced plasticization at least up to a CO 2 partial pressure of 15 atm covering the range of typical wellhead CO 2 partial pressures (5-10 atm).

We synthesized a series of rigid ladder-type diamines from readily available bromoanilines and norbornadiene in one step using facile catalytic arene-norbornene annulation (CANAL). Polycondensation of CANAL ladder diamines with 4,4'-(hexafluoroisopropylidene) diphthalic anhydride led to a series of microporous polyimides with different degrees of rotational freedom around the imide linkages. CANAL-PIs exhibited good solubility in a wide range of organic solvents, high thermal stability with decomposition temperature above 450 °C, high Brunauer-Emmett-Teller surface areas of ~ 200 -530 m 2 g -1 , and abundant micropore volume with variable pore size distributions. Mechanically robust membranes can be easily formed from CANAL-PIs and gave high gas permeabilities and moderate gas-pair selectivities. CANAL-PIs had higher permeability and similar permselectivity to analogous PIs synthesized from Tröger's base and carbocyclic Tröger's base diamines under identical test conditions. CANAL-PIs also exhibited relatively slow physical aging. These favorable properties and performance make microporous polymers based on CANAL ladder motifs promising membrane materials for gas separation.

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Two intrinsically microporous polyimides (PIM-PIs) were synthesized by the polycondensation reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,3,3′,3′-tetramethylspirobisindane-6,7,6′,7′-tetracarboxylic dianhydride (SBI) with a newly designed ohydroxyl-functionalized Troger's base diamine, 1,7-diamino-6H, 12H-5,11-methanodibenzo[1,5]diazocine-2,8-diol (HTB). Both amorphous PIM-PIs were soluble in aprotic solvents and showed excellent thermal stability with onset decomposition temperature of ∼380 °C. SBI-HTB displayed a higher CO 2 permeability (466 vs 67 barrer) than 6FDA-HTB but a significantly lower selectivity for CO 2 /CH 4 (29 vs 73), H 2 /CH 4 (29 vs 181), O 2 /N 2 (4.6 vs 6.0), and N 2 /CH 4 (1 vs 2.5). 6FDA-HTB displayed the highest gas-pair permselectivity values of all reported OH-functionalized PIM-PIs to date. The high permselectivity of 6FDA-HTB resulted primarily from exceptional diffusion selectivity due to strong size-sieving properties caused by hydrogen bonding between the proton of the hydroxyl group and the nitrogen atoms in the tertiary amine of the Troger's base (O−H•••N).

An electrospun nanofibrous adsorbent with micro-, meso- and macropores and surface area of 565 m2 g−1 was developed for the rapid removal of crude oil from seawater.

Synthesis and characterization of a microporous 6FDA-polyimide made from a novel carbocyclic pseudo Tröger's base diamine: Effect of bicyclic bridge on gas transport properties,

dianhydride (CTB2), were made and used for the synthesis of soluble polyimides of intrinsic microporosity with 3,3′-dimethylnaphthidine (DMN). The polyimides CTB1-DMN and CTB2-DMN exhibited excellent thermal stability of ∼500 °C and high BET surface areas of 580 and 469 m 2 g −1 , respectively. A freshly made dione-substituted CTB2-DMN membrane demonstrated promising gas separation performance with O 2 permeability of 206 barrer and O 2 /N 2 selectivity of 5.2. A higher O 2 permeability of 320 barrer and lower O 2 /N 2 selectivity of 4.2 were observed for a fresh CTB1-DMN film due to its higher surface area and less tightly packed structure as indicated by weaker charge-transfer complex interactions. Physical aging over 60 days resulted in reduction in gas permeability and moderately enhanced selectivity. CTB2-DMN exhibited notable performance with gas permeation data located between the 2008 and 2015 permeability/selectivity upper bounds for O 2 /N 2 and H 2 /CH 4 .

Two organo-soluble polyimides were synthesized by reaction of alicyclic bicyclo[2.2.2]­oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BC) or 1,4,7,8-tetrabromobicyclo[2.2.2]­oct-7-ene-2,3,5,6-tetracarboxylic anhydride (BCBr4) with 3,3,3′,3′-tetramethyl-1,1′-spirobisindane-5,5′-diamino-6,6′-diol (SBIDA). BC–SBIDA and BCBr4–SBIDA showed thermal stability of up to ∼420 and 352 °C and displayed microporosity as indicated by Brunauer–Emmett–Teller surface areas of 191 and 243 m2 g–1, respectively. The polyimides were solution-processable in polar organic solvents and exhibited strong mechanical properties with tensile modulus of 1.15–1.4 GPa, tensile strength of 27–28 MPa, and elongation at break of 2–4%. Introducing alicyclic moieties disturbs the delocalization of π-electrons across the polyimide backbone that reduces formation of charge transfer complexes (CTCs) leading to formation of colorless and transparent polyimide films. A fresh film sample of the bromine substituted BCBr4–SBIDA showed oxygen permeability of 31 barrer and oxygen/nitrogen selectivity of 5.9. Long-term physical aging of BCBr4–SBIDA over 365 days resulted in decrease of O2 permeability to 17 barrer with a simultaneous boost in O2/N2 selectivity to 6.6, which demonstrated highly competitive performance compared to commercially available polymers for air separation.