Synthesis and Characterization of Ionene-Polyamide Materials as Candidates for New Gas Separation Membranes
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.376
Synthesis and Characterization of Ionene-Polyamide Materials as Candidates for New Gas Separation Membranes Jason E. Bara,1,* Kathryn E. O’Harra,1 Marlow M. Durbin,1 Grayson P. Dennis,1 Enrique M. Jackson,2 Brian Thomas3 & Jamiu A. Odutola3 1 University of Alabama, Department of Chemical & Biological Engineering, Tuscaloosa, AL 354870203 USA
2
NASA Marshall Space Flight Center, Huntsville, AL 35812
3
Alabama A&M University, Department of Chemistry, Normal, AL 35762:
Abstract A new family of six ionenes containing aromatic amide linkages has been synthesized from ready available starting materials at scales up to ~50 g. These ionene-polyamides are all constitutional isomers and vary only in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) which are present in the polymer backbone. This paper details the synthesis of these ionenes and associated characterizations. Ionene-polyamides exhibit relatively low melting points (~150 oC) allowing them to be readily processed into films and other objects. These ionene-polyamide materials are being developed for further study as polymer membranes for the separations of gases such as CO2, N2, CH4 and H2.
INTRODUCTION Ionenes are defined as polymers that contain a ionic (typically cation) group directly within the polymer backbone.[1] Ionenes are distinctly different than ionomers which are polymers where the ionic moiety is present as a pendant to the backbone. Many commercial ionomers are anionic (e.g., salts of poly(acrylic acid) and poly(styrene sulfonic acid) although cationic ionomers are also well-known. Figure 1 presents a conceptual illustration of the differences between cationic ionenes and ionomers.
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Figure 1: Illustration depicting the differences between and ionomers (left) and ionenes (right). Reprinted with permission from Mittenthal, M. S.; Flowers, B. S.; Bara, J. E.; Whitley, J. W.; Spear, S. K.; Roveda, J. D.; Wallace, D. A.; Holler, R.; Martens, R.; Daly, D. T. Ionic Polyimides: Hybrid Polymer Architectures and Composites with Ionic Liquids for Advanced Gas Separation Membranes. Ind. Eng. Chem. Res. 2017, 56, 5055-5069. Copyright 2017 American Chemical Society.
The vast majority of ionenes reported in the literature have been formed via condensation polymerizations occurring via the Menshutkin between relatively tethered 3o amines or N-heterocyclic nucleophiles (i.e., Nu-R-Nu) and dihalides (i.e., X-R’-X, where X = Cl, Br or I).[1] In many examples, the natures of the R and R’ groups employed are simple alkyl, aromatic or oligo(ethylene glycol) linkages. Ionenes made in this manner typically suffer from multiple degradation mechanisms and relatively poor mechanical properties compared to conventi
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