Fluorenyl Ether Research Articles

The silica-doped sulfonated poly(fluorenyl ether ketone)s membrane using hydroxypropyl methyl cellulose as dispersant for high temperature proton exchange membrane fuel cells

Abstract The sulfonated poly(fluorenyl ether ketone)s (SPFEK) membranes doped with SiO 2 and dispersed by hydroxypropyl methyl cellulose (HPMC) were prepared and investigated for polymer electrolyte membrane fuel cells (PEMFCs) used at high temperature and low relative humidity (RH). The above membrane was prepared by solution dispersion of SPFEK and SiO 2 using HPMC as dispersant. The physio-chemical properties of the hybrid membrane were studied by means of scanning electron microscope (SEM), ion-exchange capacity (IEC), proton conductivity, and single cell performance tests. The hybrid membranes dispersed by HPMC were well dispersed when compared with common organic/inorganic hybrid membranes. The hybrid membranes showed superior characteristics as a proton exchange membrane (PEM) for PEMFC application, such as high ionic exchange content (IEC) of 1.51 equiv/g, high temperature operation properties, and the satisfactory ability of anti-H 2 crossover. The single cell performances of the hybrid membranes were examined in a 5 cm 2 commercial single cell at both 80 °C and 120 °C under different relative humidity (RH) conditions. The hybrid membrane dispersed by HPMC gave the best performance of 260 mW/cm 2 under conditions of 0.4 V, 120 °C, 50% RH and ambient pressure. The results demonstrated HPMC being an efficient dispersant for the organic/inorganic hybrid membrane used for PEM fuel cell.

Sulfonated poly(fluorenyl ether) membranes containing perfluorocyclobutane groups for fuel cell applications

This paper describes the preparation and electrochemical properties of new proton conducting polymer membranes, sulfonated poly(fluorenyl ether) membrane-containing perfluorocyclobutane (PFCB) moieties for fuel cell applications. The sulfonated polymers were prepared via thermal cyclodimerization of 9,9-bis(4-trifluorovinyloxyphenyl)fluorene and subsequent post-sulfonation using chlorosulfonic acid (CSA) as a sulfonating agent. The post-sulfonation reaction was carried out by changing the molar ratio of CSA/repeating unit of the polymer at room temperature for 5 h and the resulting sulfonated polymers showed different degrees of sulfonation (DS) and ion exchange capacities (IEC). With the increment of CSA content, the DS, IEC and water uptake of the sulfonated polymer membranes increased. Their proton conductivity was investigated as a function of temperature. The polymer membrane with an IEC value of 1.86 mmol/g showed a water content of 25% similar to Nafion-115's but showed higher proton conductivity than Nafion-115 over the temperature 25–80 °C. The polymer membrane with lower water uptake and higher IEC showed similar proton conductivity and methanol permeability to Nafion-115. These results confirmed that the sulfonated poly(fluorenyl ether)-containing PFCB groups could be a promising material for fuel cell membranes.

Poly(Arylene Ether)s with Sulfonic Acid Groups on the Backbone and Pendant for Proton Exchange Membranes Used in PEMFC Applications

AbstractSulfonated poly(aryl ether) (SPAE) and sulfonated poly(fluorenyl ether ketone) (SPFEK) are synthesized by post‐sulfonation and direct polymerization from the sulfonated monomer, respectively. Flexible and smooth proton exchange membranes (PEM) are readily obtained from both polymers, by casting from their 5% solution in N, N′‐dimethylacetamide (DMAC) at 60 °C. The thermal stability, mechanical strength, and single cell performance of the as‐prepared SPAE and SPFEK membranes in a PEM fuel cell (PEMFC) are investigated. The SPAE membrane shows a water uptake of 45% at 80 °C and a proton conductivity of 1.02 × 10–2�S cm–1, which is close to that of Nafion® 115, whereas the SPFEK membrane shows a water uptake of 49% at 80 °C and a proton conductivity of 5.37 × 10–3�S cm–1. These membranes exhibit a higher mechanical strength, and very good hydrolytic and oxidative stabilities because of their specially designed molecular structures. A single cell evaluation experiment demonstrates the superior cell performance of SPAE compared to that of SPFEK and Nafion® 115. These polymers may be a promising proton membrane material for PEM fuel cell applications.

Sulfonated poly(fluorenyl ether ketone) membrane prepared via direct polymerization for PEM fuel cell application

Sulfonated poly(fluorenyl ether ketone)s with inherent viscosity ranging from 0.68 to 0.93 dL/g were directly synthesized by aromatic nucleophilic polycondensation of bisphenol fluorene with various ratios of sulfonated difluorobenzophenone to difluorobenzophenone. The synthesized polymers were characterized by 1H NMR method and elemental analysis. The polymers were tested to be soluble in dipolar aprotic solvents such as DMAc, DMF and DMSO and can be readily cast into tough films. These films showed highly thermal degradation temperature, glass transition temperature and excellent water affinity as well as excellent proton conductivity. The polymers showed a promising proton membrane material for PEM fuel cell application.

Addition of 9-Diazofluorene to Unsubstituted and Chloro-Substituted 1,4-Benzoquinones. A Comparison with the Addition of Diphenyldiazomethane

Abstract Unsubstituted 1,4-benzoquinone (1a) reacted at the C=C double bond with 9-diazofluorene (9-DF) to give norcarene dione 2a and 4,7-dihydroxy-3H-indazole 4a. Similarly, the reaction of 2-chloro-1,4-benzoquinone (1b) with 9-DF yielded norcarene dione 2b and 4,7-dihydroxy-3H-indazole 4b, together with tricyclic dione 3b. 2,3-dichloro-1,4-benzoquinone (1c) and 9-DF produced norcarene dione 2c, 4,7-dihydroxy-3H-indazole 4c, and its fluorenyl ether 5c. Reactions of 2,5- and 2,6-dichloro- and trichloro-1,4-benzoquinones (1d, 1e, and 1f) with 9-DF provided norcarene diones 2d, 2e, and 2f and tricyclic diones 3d and 3e, respectively. On the other hand, tetrachloro-1,4-benzoquinone (1g) converted 9-DF into 9,9′-bifluorenylidene possibly via a 1:1 betaine intermediate arising from the C=O double bond addition. These results were markedly different from those of the previous diphenyldiazomethane reactions and are discussed in terms of structural changes of these diazoalkanes.