Membranes which allow fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton-exchange membrane (PEM) fuel cells (PEMFCs) and redox flow batteries (RFBs). Herein we report a new approach to designing solution-processable ion-selective polymer membranes with both intrinsic microporosity and ion-conductive functionality. Polymers are synthesized with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively charged subnanometer-sized confined ionic channels. The ready transport of protons and cations through these membranes, and the high selectivity towards nanometer-sized redox-active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell.

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Sulfonated microporous polymer membranes with fast and selective ion transport for electrochemical energy conversion and storage

A self-accelerating double-strain-promoted azide–alkyne cycloaddition reaction (DSPAAC) was used in the step polymerization for the first time. This produced a novel stoichiometric imbalance-promoted homogeneous step polymerization method using sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and various bis-azide compounds (N3-R-N3) as respective monomers. Because of the self-accelerating property of DSPAAC reaction, the novel step polymerization method could prepare high molecular weight polymers under stoichiometry imbalance condition with excess molar amounts of DIBOD to N3-R-N3. Based on the click property of DSPAAC reaction, the novel step polymerization could be efficiently performed in very mild reaction conditions such as in air at room temperature without requiring any metal catalyst or chemical stimulus. Under the present polymerization condition, the preparation of high molecular weight polymers from this novel method was accompanied by the formation of cyclic oligomers with a weight content a...

Self-Accelerating Click Reaction in Step Polymerization

We describe a straightforward synthetic strategy for a new family of functional poly(ester–amide)s (PEAs) with tertiary ester linkages via the Passerini multicomponent polymerization (Passerini-MCP) of a diacid (A2), 1,6-diisocyanohexane (B2), and four kinds of electron-deficient ketones. First, Passerini three-component reactions (Passerni-3CR) of hexanoic acid and tert-butyl isocyanide with nine kinds of ketones were investigated to evaluate the reactivities of these ketones toward Passerni-3CR. Four electron-deficient ketones, 1,1,1-trifluoroacetone (1), 1,1,1-trifluoroacetophenone (2), ethyl pyruvate (3), and 2,3-butanedione (4), were found to be excellent oxo-compounds for this Passerini-3CR. Then, the Passerini-MCP of A2 and B2 with 1, 2, 3, and 4 in CH2Cl2 was performed to generate polymers P1–P4 with tertiary ester linkages and different electron-withdrawing substituents. Polymer P5 was also prepared by the Passerini-MCP of A2 and B2 with phenylacetaldehyde (5) for comparison. Size exclusion chrom...

Functional Poly(ester–amide)s with Tertiary Ester Linkages via the Passerini Multicomponent Polymerization of a Dicarboxylic Acid and a Diisocyanide with Different Electron-Deficient Ketones

The preparation of polymers with an ultrahigh molecular weight (>106 g/mol; UHMW) is always a challenge for homogeneous step-growth polymerization. Herein, a unique homogeneous step-growth polymerization method was developed to prepare various UHMW polymers. In this approach, a double-strain-promoted azide–alkyne click reaction (DSPAAC) with a reactive intermediate was used as the polymerization reaction, and sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and bis-azide compounds with 2,6-diisopropylphenyl azide terminals were used as the monomer pairs. The DSPAAC reaction, with a reactive intermediate, facilitated this polymerization method to efficiently prepare UHMW polymers under convenient, stoichiometrically imbalanced conditions using a slight excess of DIBOD to bis-azide monomer. In addition, the click nature of the DSPAAC reaction facilitated this polymerization method to synthesize UHMW polymers under ambient conditions, requiring no catalysts. The resultant UHMW polymers presented strong fluor...

Step-Growth Polymerization Method for Ultrahigh Molecular Weight Polymers

A new, high-molecular-weight, aromatic fluorinated ladder polymer has been obtained by the superacid-catalyzed, nonstoichiometric, step polymerization of a xanthenediol with trifluoroacetone. The polymerizations carried out at room temperature in a mixture of trifluoromethanesulfonic acid (CF3SO3H, TFSA) with methylene chloride resulted in a polymer completely soluble in acetone, methylene chloride, chloroform, THF, methanol, DMF, NMP, and DMAC. The chemical composition of the ladder polymer has been confirmed by the complementary experimental and calculations studies of the 13C and 19F NMR spectra and the calculations of reaction pathways. It was also found that the growth of the fully fused-ring backbone polymer chain occurs in all three dimensions due to the formation of regioisomeric fragments. Appropriate films, for the determination of gas permeation coefficients, were obtained by casting. According to gas permeation experiments, the ladder polymer falls above Robeson’s 2008 updated upper bound for ...

A Highly Soluble, Fully Aromatic Fluorinated 3D Nanostructured Ladder Polymer

Novel, linear, high-molecular-weight single-strand heteroaromatic polymers and copolymers containing 9H-xanthene moieties in the backbone were synthesized by metal-free superacid-catalyzed stoichiometric and nonstoichiometric step-growth polymerizations of carbonyl compounds bearing electron-withdrawing substituents with bisphenols. The electrophilic aromatic substitution reactions of ketones with phenol fragments occur exclusively in ortho-positions to the hydroxy phenol group and followed by highly efficient cyclodehydration reaction of hydroxyl-containing intermediates to give corresponding substituted 9H-xanthene-2,7-diyl polymers. The polymerizations were performed at room temperature in the Bronsted superacid trifluoromethanesulfonic acid (CF3SO3H, TFSA) and in a mixture of TFSA with methylene chloride and nitrobenzene.

Fransico A. Ruiz-Trevino

Papers

Linear, Single-Strand Heteroaromatic Polymers from Superacid-Catalyzed Step-Growth Polymerization of Ketones with Bisphenols