Comb-shaped guanidinium functionalized poly(ether sulfone)s for anion exchange membranes: Effects of the spacer types and lengths

Designing Highly Conductive Block Copolymer-Based Anion Exchange Membranes by Mesoscale Simulations

Hydroxide ion conductivity is a key aspect of anion exchange membranes and is mainly determined by the nanoscale membrane morphologies. Fundamental understanding of the structural and transport properties of membranes in terms of polymer architectures is crucial for future development of membrane-based applications. Using mesoscale simulations, this work predicts the mesostructure of the hydrated triblock copolymers; the designed polymers are composed of aromatic (polyphenylene oxide, PPO) or aliphatic (polystyrene-ethylene-butylene-styrene, SEBS) backbones, with cationic side chains being modified by hydrophobic or hydrophilic spacers. For PPO-based polymers, using octyl spacers creates a meshlike water network, yielding ion conductivity equal to 30.6 mS/cm at room temperature. For SEBS-based polymers, the nonmodified form is sufficient to produce ion-conducting pathways. Adding hydrophobic spacers further enhances the nanosegregation, and the membranes provide similar conductivity at a lower ion exchange capacity and water content. Adding hydrophilic spacers, however, has negative impacts on the ion transport. The side chains are in the stretched configurations, which sterically hinder the mobility of water and hydroxide ions. Such a resistance can be overcome by adapting multication side-chain designs, where large water channels are formed, yielding ion conductivity as high as 32.8 mS/cm.

Multiple Enhancement Effects of Crown Ether in Tröger's Base Polymers on the Performance of Anion Exchange Membranes

The development of anion exchange membranes (AEMs) is hindered by the trade-off of ionic conductivity, alkaline stability, and mechanical properties. Tröger's base polymers (Tb-polymers) are recognized as promising membrane materials to overcome these obstacles. Herein, the AEMs made from Tb-poly(crown ether)s (Tb-PCEs) show good comprehensive performance. The influence of crown ether on the conductivity and alkaline stability of AEMs has been investigated in detail. The formation of hydronium ion-crown ether complexes and an obvious microphase-separated structure formed by the existence of crown ether can enhance the conductivity of the AEMs. The maximum OH^- conductivity of 141.5 mS cm^-1 is achieved from the Tb-PCEs based AEM (Tb-PCE-1) at 80 °C in ultrapure water. The ion-dipole interaction of the Na⁺ with crown ether can protect the quaternary ammonium from the attack of OH^- to improve the alkaline stability of AEMs. After 675 h of alkaline treatment, the OH^- conductivity of Tb-PCE-1 decreases by only 6%. The Tb-PCE-1-based single cell shows a peak power density of 0.202 W cm^-2 at 80 °C. The prominent physicochemical properties are attributed to the well-developed microstructure of the Tb-PCEs, as revealed by TEM, AFM, and SAXS observations.

A facile approach to prepare crosslinked polysulfone-based anion exchange membranes with enhanced alkali resistance and dimensional stability

Novel anion exchange membranes with enhanced ion exchange capacity, dimensional stability and alkali stability were prepared by a facile synthesis method. Internal crosslinking networks in the resulting membranes were achieved by reacting chloromethylated polysulfone with 4,4′-trimethylene bis(1-methylpiperidine) (BMP), where BMP was used as both a quaternization reagent and crosslinker without requirement of post-functionalization. In order to evaluate the alkali resistance and dimension stability performance of the resulting membranes, the molar ratio of BMP in the resulting membranes was fixed at four different contents: 40%, 60%, 80% and 100%. The obtained membranes were accordingly denoted as CAPSF-N, in which N = 40, 60, 80 and 100, respectively. Due to the dense internal network structure and spatial conformation of the six-membered rings, the resulting CAPSF-N AEMs showed enhanced dimensional structures (at 60 °C, the water uptakes and swelling ratios of CAPSF-N were 8.42% to 14.84% and 2.32% to 5.93%, respectively, whereas those for the commercial AEM Neosepta AMX were 44.23% and 4.22%, respectively). In addition, after soaking in 1 M KOH solution at 60 °C for 15 days, the modified membranes exhibited excellent alkaline stability. The CAPSF-100 membrane showed the highest alkali stability (retained 85% of its original ion exchange capacity and 84% of its original OH⁻ conduction after the alkaline stability test), whereas the non-crosslinked APSF broke into pieces. Additionally, compared to the commercial Neosepta AMX membrane under the same test conditions, the desalination efficiency of CAPSF-100 was enhanced, and the energy consumption was lower.

Novel anion exchange membranes with enhanced ion exchange capacity, dimensional stability and alkali stability were prepared by a facile synthesis method.

Boosting the performance of an anion exchange membrane by the formation of well-connected ion conducting channels

Enlarging the discrepancies between hydrophilic/hydrophobic segments in the chemical structure of an ionomer proved to be an efficient strategy to induce the formation of a microphase-separated morphology of the resulting anion exchange membrane.

Facile fabrication of positively-charged helical poly(phenyl isocyanide) modified multi-stimuli-responsive nanoassembly capable of high efficiency cell-penetrating, ratiometric fluorescence imaging, and rapid intracellular drug release

High efficiency cell-penetrating helical chain functionalized polymeric micelles capable of co-delivery of cargoes and rapid release were reported.