Novel Wholly Aromatic Sulfonated Poly(arylene ether) Copolymers Containing Sulfonic Acid Groups on the Pendants for Proton Exchange Membrane Materials

A Sulfonated All-Aromatic Polyamide for Heavy Metal Capture: A Model Study with Pb(II)

Polyelectrolytes are widely used in heavy metal removal, finding applications as coagulants and flocculants. We compare the heavy metal removal capability of a water-soluble sulfonated semirigid polyamide, poly(2,2'-disulfonyl-4,4'-benzidine isophthalamide) (PBDI), with that of a well-known random-coil polymer, poly(sodium 4-styrenesulfonate) (PSS). Using lead (Pb(II)) as a model contaminant, both polymers precipitate out from solution at ~500 mg/L Pb(II) in water. The ability to remove Pb(II) from water was quantified using adsorption isotherms and fitted with Langmuir and Freundlich adsorption models. The sorption of Pb(II) by PSS fit the Langmuir model with a high degree of correlation (0.976 R2), but the sorption of Pb(II) by PBDI could not be accurately predicted using the Langmuir or Freundlich model. The sorption of Pb(II) by PBDI and PSS was compared by normalizing sorption by the number of sulfonate groups of each polymer and the ion exchange capacity (IEC), found by titration. We find that PBDI removes a greater amount of Pb(II) per gram of sorbent compared to PSS, 410 mg/g vs 260 mg/g, respectively, which cannot be accounted for by differences in IEC or number of sulfonate groups. Our findings confirm that the positioning of the sulfonate groups and the rigidity of the polymer backbone play an important role in how Pb(II) coordinates to the polymer prior to precipitating out from solution.

Synthesis and investigation of sulfonated poly(p-phenylene)-based ionomers with precisely controlled ion exchange capacity for use as polymer electrolyte membranes

To achieve precise control of sulfonated polymer structures, a series of poly(p-phenylene)-based ionomers with well-controlled ion exchange capacities (IECs) were synthesised via a three-step technique: (1) preceding sulfonation of the monomer with a protecting group, (2) nickel(0) catalysed coupling polymerisation, and (3) cleavage of the protecting group of the polymers. 2,2-Dimethylpropyl-4-[4-(2,5-dichlorobenzoyl)phenoxy]benzenesulfonate (NS-DPBP) was synthesised as the preceding sulfonated monomer by treatment with chlorosulfuric acid and neopentyl alcohol. NS-DPBP was readily soluble in various organic solvents and stable during the nickel(0) catalysed coupling reaction. Sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (S-PPBP) homopolymer and seven types of random copolymers (S-PPBP-co-PPBP) with different IECs were obtained by varying the stoichiometry of NS-DPBP. The IECs and weight average molecular weights (M_ws) of ionomers were in the range of 0.41–2.84 meq. g⁻¹ and 143 000–465 000 g mol⁻¹, respectively. The water uptake, proton conductivities, and water diffusion properties of ionomers exhibited a strong IEC dependence. Upon increasing the IEC of S-PPBP-co-PPBPs from 0.86 to 2.40 meq. g⁻¹, the conductivities increased from 6.9 × 10⁻⁶ S cm⁻¹ to 1.8 × 10⁻¹ S cm⁻¹ at 90% RH. S-PPBP and S-PPBP-co-PPBP (4 : 1) with IEC values >2.40 meq. g⁻¹ exhibited fast water diffusion (1.6 × 10⁻¹¹ to 8.0 × 10⁻¹⁰ m² s⁻¹), and were comparable to commercial perfluorosulfuric acid polymers. When fully hydrated, the maximum power density and the limiting current density of membrane electrode assemblies (MEAs) prepared with S-PPBP-co-PPBP (4 : 1) were 712 mW cm⁻² and 1840 mA cm⁻², respectively.

Poly(p-phenylene)-based sulfonated polymers with well-controlled IECs were synthesized via a three-step procedure including preceding sulfonation of precursor monomers.

High-Performance Semicrystalline Poly(ether ketone)-Based Proton Exchange Membrane

A novel semicrystalline poly(ether ketone) (PEK)-based proton exchange membrane (semi-SPEK-x) has been developed. Through a one-step sulfonation and hydrolysis, a poly(ether ketimine) precursor transforms into PEK and ion-conducting groups are introduced. With an ion-exchange capacity ranging from 1.49 to 2.00 mequiv g^-1, the semi-SPEK-x polymers exhibit a semicrystalline feature in both dry and hydrated states. Owing to the semicrystalline domains inside the polymer, the obtained membrane exhibits low water uptake and low volume swelling ratio. More importantly, the semicrystalline structure lowers methanol permeability and, consequently, improves the overall performances of direct methanol fuel cells.

Hexafluoroisopropylidene based sulfonated new copolytriazoles: investigation of proton exchange membrane properties

A series of novel sulfonated polytriazole copolymers (PTFOSH-XX) was successfully prepared by the click reaction of 4,4′-(perfluoropropane-2,2-diyl)bis((prop-2-ynyloxy)benzene (TF), 4,4′-diazido-2,2′-stilbene disulfonic acid disodium salt (SAZ) and 4,4′-diazidodiphenyl ether (OAZ). The copolymers were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed high mechanical, thermal and oxidative stability and low swelling. The phase separated morphology of the membranes was confirmed from transmission electron microscopy (TEM). The membranes showed proton conductivity as high as 110 and 122 mS cm−1 at 80 and 90°C, respectively depending on the polymer repeat unit structure.

Synthesis and characterization of poly(arylene ether ketone)s with 3,6-diphenyl-9H-carbazole pendants using C–N coupling reaction

3,6-Diphenyl-9 H-carbazole pendants are grafted herein to poly(arylene ether ketone)s (PAEKs) via the Ullmann C–N coupling reaction. To the best of our knowledge, this is the first time that PAEKs containing a carbazole pendant (Cz) have been synthesized through the Ullmann C–N coupling reaction. The high molecular weights of PAEK-Cz (PAEKs with 3,6-diphenyl-9 H-carbazole pendants) are inherited from their precursors, owing to the high reactivity of their monomers. The obtained PAEK-Cz- x polymers exhibit good solubility in most common organic solvents and excellent thermal stabilities, with the 5% weight loss temperatures for all products being above 598°C under a nitrogen atmosphere. The glass transition temperatures are all above 199°C and can be controlled by adjusting the feed ratio of monomers. The polymer membranes obtained by the casting method are tough and thus have strong potential for practical applications.

Approach to high proton/vanadium selectivity in an ionic exchange membrane via a hyperbranching design

High H⁺/V selectivity was achieved for the ion exchange membrane due to specially designed hyperbranching structure and intermolecular force.

High fluorescence intensity poly(aryl ether ketone)s containing tetraphenylethylene moieties: preparation, characterization and fluorescent properties

PAEK with tetraphenylethylene groups and relationships between fluorescence intensity and temperature.

Synthesis and properties of sulfonated poly(arylene ether ketone sulfone) copolymer

A series of novel sulfonated poly(arylene ether ketone sulfone)s copolymer (SPAEKS- x) were synthesized by polycondensation reaction of commercial 2,2-bis(4-hydroxyphenyl)propane, 4,4′-dichlorodiphenylsulfone, 4,4′-dihydroxydiphenylether, and 3,3′disulfonate-4,4′-difluorobenzophenone. The degree of sulfonation was realized by controlling quantities of the sulfonated monomer. The structure of SPAEKS- x was confirmed by proton nuclear magnetic resonance and Fourier transform infrared instrument. The tough, flexible, and transparent films of SPAEKS- x were obtained by solution casting. These membranes with desired ion-exchange capacity (IEC) values showed good thermal stability and mechanical properties. The proton conductivity of SPAEKS- x with the IEC of 1.44 meq. g−1 is very close to that of Nafion 117 in a temperature range from 20°C to 100°C. SPAEKS- x copolymers, which combine the advantages of the sufficiently high proton transport conductivity and enhanced physical properties, will be the potential alternative materials to Nafion for proton exchange membrane fuel cell.

Synthesis and properties poly(arylene ether sulfone)s with pendant hyper-sulfonic acid

A novel poly(arylene ether sulfone)s with pendant multiple sulfonic acid groups on aromatic side chains was prepared by graft method, they displayed high proton conductivity and good dimensional stability.

Synthesis and properties of comb-shaped poly(arylene ether)

A novel comb-shaped fluorinated poly(arylene ether) (cs-FPAE) was prepared from a difluoride monomer, 4-(2,6-difluorobenzoyl)diphenyl ether, with commercial 4,4′-(hexafluoroisopropylidene) diphenol by nucleophilic polycondensation reaction. The number-average molecular weight and polydispersities of cs-FPAE were in the range of 11,000–25,000 and 1.9–2.5, respectively. The refractive index (1.4667–1.5644) and birefringence (0.005–0.02 at 1550 nm wavelength) of spin-coated polymer films were determined using the prism-coupling method.

Triple-layer sulfonated poly(ether ether ketone)/sulfonated polyimide membranes for fuel cell applications

A series of triple-layer membranes were prepared based on a sulfonated polyimide (SPI) and a traditional sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. Compared with the single-component membranes (pure SPI and SPEEK), the multicomponent membranes exhibited better comprehensive performance. Interestingly, the triple-layer membranes possessed improved mechanical properties, lower water uptake, and swelling ratio than those of the corresponding blend membranes. When the contents of SPI were 30 and 40%, the triple-layer membranes even had lower methanol permeability (3.42 and 2.61 × 10−7 cm2 s−1, respectively) than that of the pure SPI membrane (3.51 × 10−7 cm2 s−1). The proton conductivity of the triple-layer membranes was in the range of 0.117–0.149 S cm−1 at 100°C. All the results suggest that the triple-layer membranes have sufficiently excellent performance to be applied in fuel cells.

Synthesis and preparation of sulfonated hyperbranched poly(aryl ether ketone)–sulfonated linear poly(aryl ether ketone) blend membranes for proton exchange membranes

A novel series of sulfonated hyperbranched poly(aryl ether ketone)s (S-HPAEKs) was synthesized based on different post-sulfonation reactions of fluoro-terminated hyperbranched poly(aryl ether ketone). Moreover, the blend membranes of S-HPAEKs with sulfonated linear poly(aryl ether ketone) (S-LPAEK) (S-HPAEK/S-LPAEK) were prepared for proton exchange membrane. All the blends could be cast into tough membranes. The structure of S-HPAEKs was characterized and the thermal stability, water uptake, and proton conductivity of S-HPAEK/S-LPAEK membranes were investigated. The results showed that S-HPAEK/S-LPAEK membranes possessed good thermal stability, better water uptake, and good proton conductivity compared with the S-LPAEK membrane, and their properties depended on the ion exchange capacity and the content of S-HPAEK in the blend membranes.

Preparation of carboxylated/sulfonated poly(arylene ether ketone)s for proton exchange membranes

Derived from a hydroquinone monomer, a series of poly(arylene ether ketone)s containing ethyl benzoate pendants were first prepared as starting materials via aromatic nucleophilic substitution polycondensations. Sulfonated analogues could be obtained by simply stirring the obtained polymers in 95–98% sulfuric acid at room temperature. Following this, poly(arylene ether ketone)s bearing both carboxyl and sulfonic acid groups were prepared through a hydrolysis reaction of the ester groups on the above sulfonated polymers. The properties, including thermal, oxidative and dimensional stability, water absorption, mechanical properties, proton conductivity and methanol crossover of both sulfonated and sulfonated/carboxylated polymers were well investigated. It was found that some membranes exhibited good properties for proton exchange membranes.