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1. Synthesis and Performance of 6FDA-Based Polyimide-Ionenes and Composites with Ionic Liquids as Gas Separation Membranes

   https://doi.org/10.3390/membranes9070079  

   O’Harra, Kathryn; Kammakakam, Irshad; Devriese, Emily; Noll, Danielle; Bara, Jason; Jackson, Enrique (July 2019, Membranes)

   null (Ed.)

   Three new isomeric 6FDA-based polyimide-ionenes, with imidazolium moieties and varying regiochemistry (para-, meta-, and ortho- connectivity), and composites with three different ionic liquids (ILs) have been developed as gas separation membranes. The structural-property relationships and gas separation behaviors of the newly developed 6FDA polyimide-ionene + IL composites have been extensively studied. All the 6FDA-based polyimide-ionenes exhibited good compatibility with the ILs and produced homogeneous hybrid membranes with the high thermal stability of ~380 °C. Particularly, [6FDA I4A pXy][Tf2N] ionene + IL hybrids having [C4mim][Tf2N] and [Bnmim][Tf2N] ILs offered mechanically stable matrixes with high CO2 affinity. The permeability of CO2 was increased by factors of 2 and 3 for C4mim and Bnmim hybrids (2.15 to 6.32 barrers), respectively, compared to the neat [6FDA I4A pXy][Tf2N] without sacrificing their permselectivity for CO2/CH4 and CO2/N2 gas pairs. 

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2. Self‐healing imidazolium‐based ionene‐polyamide membranes: an experimental study on physical and gas transport properties

   https://doi.org/10.1002/pi.5802  

   Kammakakam, Irshad; O'Harra, Kathryn_E; Dennis, Grayson_P; Jackson, Enrique_M; Bara, Jason_E (March 2019, Polymer International)

   ABSTRACT A new series of six imidazolium‐based ionenes containing aromatic amide linkages has been developed. These ionene‐polyamides are all constitutional isomers varying in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) along the polymer backbone. The physical properties as well as the gas separation behaviors of the corresponding membranes have been extensively studied. These ionene‐polyamide membranes show excellent thermal and mechanical stabilities, together with self‐healing and shape memory characteristics. Most importantly, [TC‐API(p)‐Xy][Tf₂N] and [IC‐API(m)‐Xy][Tf₂N] membranes (TC, terephthaloyl chloride; API, 1‐(3‐aminopropyl)imidazole; Xy, xylyl; Tf₂N, bis(trifluoromethylsulfonyl) imide; IC, isophthaloyl chloride), where the amide and xylyl linkages are attached at para and meta positions, exhibit superior selectivity for CO₂/CH₄and CO₂/N₂gas pairs. We also demonstrate the transport properties and diverse applicability of our newly developed ionene‐polyamides, particularly [TC‐API(p)‐Xy][Tf₂N], for various industrial applications. © 2019 Society of Chemical Industry 

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3. Understanding the effects of backbone chemistry and anion type on the structure and thermal behaviors of imidazolium polyimide‐ionenes

   https://doi.org/10.1002/pi.5825  

   O'Harra, Kathryn_E; Kammakakam, Irshad; Bara, Jason_E; Jackson, Enrique_M (May 2019, Polymer International)

   Abstract Advancements in the performance and properties of ionenes can be achieved via rational molecular design strategies which combine structural elements of ionic liquids (ILs) and high‐performance polymers. The use of imidazole‐amine molecules with asymmetric reactivity has enabled the synthesis of new bis(imidazole) diimide monomers which are then polymerized via the Menshutkin reaction, followed by anion exchange to various molecular species well known in the IL literature. In this work, three types of imidazolium polyimide‐ionene backbones were synthesized starting from 1‐(3‐aminopropyl)imidazole and pyromellitic dianhydride (PMDA) or 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) or from 1‐(4‐aminophenyl)imidazole and 6FDA, with these monomers then reacted withpara‐dichloroxylene. The Cl⁻anions on the resultant ionenes were then exchanged with one of six molecular anions yielding a total of 18 distinct polymer compositions. The functional groups present within the cationic backbone as well as the anion type were observed to strongly influence both the thermal and organizational properties of these new ionenes. © 2019 Society of Chemical Industry 

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4. Molecularly engineering polymeric membranes for H₂ / CO₂ separation at 100–300 °C

   https://doi.org/10.1002/pol.20200220  

   Hu, Leiqing; Pal, Sankhajit; Nguyen, Hien; Bui, Vinh; Lin, Haiqing (July 2020, Journal of Polymer Science)

   Abstract Over the last two decades, polymers with superior H₂/CO₂separation properties at 100–300 °C have gathered significant interest for H₂purification and CO₂capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H₂/CO₂separation and the advantages of high‐temperature operation (such as improved solubility selectivity and absence of CO₂plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H₂and CO₂, including functional polymers (such as polybenzimidazole) and engineered polymers by cross‐linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size‐sieving or H₂‐sorptive nanofillers with attractive H₂/CO₂separation properties. 

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5. Designing Imidazolium Poly(amide-amide) and Poly(amide-imide) Ionenes and Their Interactions with Mono- and Tris(imidazolium) Ionic Liquids

   https://doi.org/10.3390/polym12061254  

   O’Harra, Kathryn E.; Noll, Danielle M.; Kammakakam, Irshad; DeVriese, Emily M.; Solis, Gala; Jackson, Enrique M.; Bara, Jason E. (June 2020, Polymers)

   null (Ed.)

   Here we introduce the synthesis and thermal properties of a series of sophisticated imidazolium ionenes with alternating amide-amide or amide-imide backbone functionality, and investigate the structural effects of mono(imidazolium) and unprecedented tris(imidazolium) ionic liquids (ILs) in these ionenes. The new set of poly(amide-amide) (PAA) and poly(amide-imide) (PAI) ionenes represent the intersection of conventional high-performance polymers with the ionene archetype–presenting polymers with alternating functional and ionic elements precisely sequenced along the backbone. The effects of polymer composition on the thermal properties and morphology were analyzed. Five distinct polymer backbones were synthesized and combined with a stoichiometric equivalent of the IL 1-benzyl-3-methylimidazolium bistriflimide ([Bnmim][Tf2N]), which were studied to probe the self-assembly, structuring, and contributions of intermolecular forces when IL is added. Furthermore, three polyamide (PA) or polyimide (PI) ionenes with simpler xylyl linkages were interfaced with [Bnmim][Tf2N] as well as a novel amide-linked tris(imidazolium) IL, to demonstrate the structural changes imparted by the inclusion of functional, ionic additives dispersed within the ionene matrix. This work highlights the possibilities for utilizing concepts from small molecules which exhibit supramolecular self-assembly to guide creative design and manipulate the structuring of ionenes. 

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