Anion Exchange Composite Membranes Composed of Quaternary Ammonium-Functionalized Poly(2,6-dimethyl-1,4-phenylene oxide) and Silica for Fuel Cell Application

Anion exchange membranes (AEMs) with good alkaline stability and ion conductivity are fabricated by incorporating quaternary ammonium-modified silica into quaternary ammonium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO). Quaternary ammonium with a long alkyl chain is chemically grafted to the silica in situ during synthesis. Glycidyltrimethylammoniumchloride functionalization on silica (QSiO₂) is characterized by Fourier transform infrared and transmission electron microscopic techniques. The QPPO/QSiO₂ membrane having an ion exchange capacity of 3.21 meq·g^-1 exhibits the maximum hydration number (λ = 11.15) and highest hydroxide ion conductivity of 45.08 × 10^-2 S cm^-1 at 80 °C. In addition to the high ion conductivity, AEMs also exhibit good alkaline stability, and the conductivity retention of the QPPO/QSiO₂-3 membrane after 1200 h of exposure in 1 M potassium hydroxide at room temperature is about 91% ascribed to the steric hindrance offered by the grafted long glycidyl trimethylammonium chain in QSiO₂. The application of the QPPO/QSiO₂-3 membrane to an alkaline fuel cell can yield a peak power density of 142 mW cm^-2 at a current density of 323 mA cm^-2 and 0.44 V, which is higher than those of commercially available FAA-3-50 Fumatech AEM (OCV: 0.91 V; maximum power density: 114 mW cm^-2 at current density: 266 mA cm^-2 and 0.43 V). These membranes provide valuable insights on future directions for advanced AEM development for fuel cells.

Preparation and Characterization of Pore Filled Hybrid Composite Membrane Composed of Cation Exchange Materials and Polyethylene Support

This study investigated ion exchange membranes for application to seawater desalination processes. This can provide better energy efficiency than the conventional reverse osmosis process. In this experiment, the problem of decreasing ion exchange performance when the ion exchange composite membrane was prepared could be improved through nanoparticles. The nanoparticle added ion exchange hybrid membrane showed ion exchange capacity similar to that of the conventional pristine film. In addition, the polymer having a high ion exchange capacity has poor mechanical strength, but has excellent mechanical strength of 30 MPa or more by the introduction of a polyethylene support.

Electrochemical Performance Evaluation of Bipolar Membrane Using Poly(phenylene oxide) for Water Treatment System

This study describes the use of poly(phenylene oxide) polymer-based ion-exchange polymers, polystyrene-based ion-exchange particles and a porous support for fabricating bipolar membranes and the results of an assessment of the applicability of these materials to water splitting. In order to achieve good mechanical as well as good ion-exchange properties, bipolar membranes were prepared by laminating poly(phenylene oxide) and polystyrene based ion-exchange membranes with a sulfonated polystyrene-block-(ethylene-ran-butylene)-block-polystyrene) (S-SEBS) modified interface. PE pore-supported ion-exchange membranes were also used as bipolar membranes. The tensile strength was 13.21 MPa for the bipolar membrane which utilized only a cation/anion-exchange membrane. When ion-exchange nanoparticles were introduced for high efficiency, a reduction in the tensile strength to 6.81 MPa was observed. At the same time, bipolar membrane in the form of a composite membrane using PE support exhibited the best tensile strength of 32.41 MPa. To confirm the water-splitting performance, an important factor for a bipolar membrane, pH changes over a period of 20 min were also studied. During water slitting using CA-P-PE-BPM, the pH at the CEM part and the AEM part changed from 5.4 to 4.18 and from 5.4 to 5.63, respectively.

Preparation and Characterization of Various Poly(ether ether ketone) Containing Imidazolium Moiety for Anion Exchange Membrane Fuel Cell Application

In this study, various poly(ether ether ketone) were synthesized using three different monomers and the imidazolium group was introduced into synthesized poly(ether ether ketone)s by using substitution reaction. Synthesized polymers were used to prepare anion exchange membranes and to evaluate its properties. Thermal, chemical and structural properties were carried out using thermogravimetric analysis, nuclear magnetic resonance. The anion exchange membranes with different imidazolium moieties were characterized by several different analytical techniques such as water up take, ion exchange capacity, hydroxide conductivity for checking the possibility to apply the anion exchange membrane fuel cell. Consequently, results of characterization were studied to understand the correlation between stabilities of the membrane and functional group and polymer backbone structures. And we confirm membrane performance was improved by increasing imidazolium cation groups.

Amorphous Fluoropolymer Membrane for Gas Separation Applications

Amorphous fluoropolymers have been studied in the past few decades and received extensive attention due to their unique and useful properties. One of the remarkable properties of amorphous fluoropolymers is high fractional free volume (FFV), and they tend to retain large amounts of solvent inside their polymer chains. In this study, amorphous flouoropolymer membranes were employed to examine the influences of the residual solvent and drying condition on the thermal properties, gas permeation behavior, and structure change by the polymer chains. Thermal properties of the produced membranes were characterized by differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA) to verify the effects of residual solvent. The residual solvent content and the glass transition temperature (Tg) of amorphous fluoropolymer membranes prepared with both solvents decrease with increasing drying temperature. The effect of the thermal treatment method on the d-spacing between the polymer chains of the prepared membranes was investigated using X-ray diffraction (XRD). The d-spacing decreased with drying below the Tg whereas it drastically increased near the Tg because of chain relaxation. From these phenomena, the helium permeability of the membranes treated at 120 °C radically increased. However, the oxygen and nitrogen permeability decreased with decreasing residual solvent content. The glass transition range shifted to higher temperature, from 75 °C to 133 °C, depending on the reduced amount of residual solvent.