Polysulfones Grafted with Poly(vinylphosphonic acid) for Highly Proton Conducting Fuel Cell Membranes in the Hydrated and Nominally Dry State

Superprotonic Conductivity by Synergistic Blending of Coordination Polymers with Organic Polymers: Fabrication of Durable and Flexible Proton Exchange Membranes

Creation of an efficient and cost-effective proton exchange membrane (PEM) has emerged as a propitious solution to address the challenges of renewable energy development. Coordination polymers (CPs) have garnered significant interest due to their multifunctional applications and moldability, along with long-range order. To leverage the potential of CPs in fuel cells, it is essential to integrate microcrystalline CPs into organic polymers to prepare membranes and avoid grain boundary issues. In this study, we designed and synthesized CPs containing imidazole and sulfonate moieties via gel-to-crystal transformation. The integration of CPs into the PVDF-PVP matrix resulted in superprotonic conductivity in the order of 10-2 S cm-1 at room temperature (30 °C) and 98 % RH. The proton conductivity achieved with CP-integrated composite membrane was 4.69×10-2 S cm-1 at 80 °C and 98 % RH, the highest among all CP/MOF-integrated PVDF-PVP membranes under hydrous conditions. The excellent compatibility of CPs with PVDF-PVP produced highly flexible membranes with superior mechanical, chemical, and thermal stability. About 25 times higher proton conductivity value was achieved with membrane, compared to intrinsic CPs, at RT and 98 % RH. Thus, we present a cost-effective CP-integrated mixed-matrix membrane with superprotonic conductivity and long-term durability for cutting-edge fuel cell development.

Fast proton conductors for low humidity: hydrophilic sulfonated and phosphonated polysilsesquioxanes with Al-O-P crosslinks

Proton-conducting polysilsesquioxane oligomers with core-shell structures consisting of hydrophilic silica-rich cores surrounded by an organic layer with sulfonic and phosphonic acid groups were synthesized. They were crosslinked by mixing with phosphoric acid and aluminum ions to form a hydrophilic Al-O-P framework. The resulting polymers were clear, uniform, flexible, and exhibited a high proton conductivity above 100 °C in non-humidified low-humidity air (∼22 mS cm-1 at 120 °C and ∼1%RH) because of their high sulfonic acid concentration and high water retention capability.

Hydrocarbon Ionomeric Binders for Fuel Cells and Electrolyzers

Ionomeric binders in catalyst layers, abbreviated as ionomers, play an essential role in the performance of polymer-electrolyte membrane fuel cells and electrolyzers. Due to environmental issues associated with perfluoroalkyl substances, alternative hydrocarbon ionomers have drawn substantial attention over the past few years. This review surveys literature to discuss ionomer requirements for the electrodes of fuel cells and electrolyzers, highlighting design principles of hydrocarbon ionomers to guide the development of advanced hydrocarbon ionomers.

Spotting Trends in Organocatalyzed and Other Organomediated (De)polymerizations and Polymer Functionalizations

Organocatalysis has evolved into an effective complement to metal- or enzyme-based catalysis in polymerization, polymer functionalization, and depolymerization. The ease of removal and greater sustainability of organocatalysts relative to transition-metal-based ones has spurred development in specialty applications, e.g., medical devices, drug delivery, optoelectronics. Despite this, the use of organocatalysis and other organomediated reactions in polymer chemistry is still rapidly developing, and we envisage their rapidly growing application in nascent areas such as controlled radical polymerization, additive manufacturing, and chemical recycling in the coming years. In this Review, we describe ten trending areas where we anticipate paradigm shifts resulting from novel organocatalysts and other transition-metal-free conditions. We highlight opportunities and challenges and detail how new discoveries could lead to previously inaccessible functional materials and a potentially circular plastics economy.

Anhydrous Proton Transport within Phosphonic Acid Layers in Monodisperse Telechelic Polyethylenes

Polymers bearing phosphonic acid groups have been proposed as anhydrous proton-conducting membranes at elevated operating temperatures for applications in fuel cells. However, the synthesis of phosphonated polymers and the control over the nanostructure of such polymers is challenging. Here, we report the straightforward synthesis of phosphonic acid-terminated, long-chain aliphatic materials with precisely 26 and 48 carbon atoms (C₂₆PA₂ and C₄₈PA₂). These materials combine the structuring ability of monodisperse polyethylenes with the ability of phosphonic acid groups to form strong hydrogen-bonding networks. Anhydride formation is absent so that charge carrier loss by a condensation reaction is avoided even at elevated temperatures. Below the melting temperature (T_m), both materials exhibit a crystalline polyethylene backbone and a layered morphology with planar phosphonic acid aggregates separated by 29 and 55 Å for C₂₆PA₂ and C₄₈PA₂, respectively. Above T_m, the amorphous polyethylene (PE) segments coexist with the layered aggregates. This phenomenon is especially pronounced for the C₂₆PA₂ and is identified as a thermotropic smectic liquid crystalline phase. Under these conditions, an extraordinarily high correlation length (940 Å) along the layer normal is observed, demonstrating the strength of the hydrogen bond network formed by the phosphonic acid groups. The proton conductivity in both materials in the absence of water reaches 10^-4 S/cm at 150 °C. These new precise phosphonic acid-based materials illustrate the importance of controlling the chemistry to form self-assembled nanoscale aggregates that facilitate rapid proton conductivity.

Stereo- and Regioselective cis-Hydrophosphorylation of 1,3-Enynes Enabled by the Visible-Light Irradiation of NiCl2(PPh3)2

Described herein is a stereo- and regioselective cis-hydrophosphorylation reaction of the internal alkyne of 1,3-enynes that accesses various 1,3-dienes in good isolated yields. The visible-light irradiation of NiCl₂(PPh₃)₂ allows the generation of highly reactive nickel(II)-phosphorus species that subsequently migrate into the internal alkyne of the 1,3-enynes and protonate the resulting vinyl nickel species, leading to various phosphinoyl 1,3-butadienes under mild reaction conditions.

Synergistically integrated phosphonated poly(pentafluorostyrene) for fuel cells

Modern electrochemical energy conversion devices require more advanced proton conductors for their broad applications. Phosphonated polymers have been proposed as anhydrous proton conductors for fuel cells. However, the anhydride formation of phosphonic acid functional groups lowers proton conductivity and this prevents the use of phosphonated polymers in fuel cell applications. Here, we report a poly(2,3,5,6-tetrafluorostyrene-4-phosphonic acid) that does not undergo anhydride formation and thus maintains protonic conductivity above 200 °C. We use the phosphonated polymer in fuel cell electrodes with an ion-pair coordinated membrane in a membrane electrode assembly. This synergistically integrated fuel cell reached peak power densities of 1,130 mW cm^-2 at 160 °C and 1,740 mW cm^-2 at 240 °C under H₂/O₂ conditions, substantially outperforming polybenzimidazole- and metal phosphate-based fuel cells. Our result indicates a pathway towards using phosphonated polymers in high-performance fuel cells under hot and dry operating conditions.

Transition metal-free and regioselective vinylation of phosphine oxides and H-phosphinates with VBX reagents

A series of phosphine oxides and H-phosphinates were vinylated in the presence of the iodine(iii) reagents vinylbenziodoxolones (VBX), providing the corresponding alk-1-enyl phosphine oxides and alk-1-enyl phosphinates in good yields with complete chemo- and regioselectivity. The vinylation proceeds in open flask under mild and transition metal-free conditions.

Rare earth metal-mediated ring-opening polymerisation of cyclic phosphoesters

An efficient polymerisation of cyclic phosphoesters using a rare-earth metallocene as a catalyst is described, giving biodegradable polyphosphonates and polyphosphates.

Poly(vinylidene fluoride) Containing Phosphonic Acid as Anticorrosion Coating for Steel

Vinylidene fluoride (VDF)-based copolymers bearing pendant phosphonic acid function for potential application as anticorrosion coatings were synthesized via free radical copolymerization of VDF with a new phosphorus containing 2-trifluoromethacrylate monomer, (dimethoxyphosphoryl)methyl 2-(trifluoromethyl)acrylate (MAF-DMP). MAF-DMP was prepared from 2-trifluoromethacrylic acid in 60% overall yield. Radical copolymerizations of VDF with MAF-DMP initiated by tert-amyl peroxy-2-ethylhexanoate at varying ([VDF]₀/[MAF-DMP]₀) feed ratios led to several poly(VDF-co-MAF-DMP) copolymers having different molar percentages of VDF (79-96%) and number-average molecular weights (M_n's) up to ca. 10 000 g mol^-1 in fair yields (47-53%). Determination of the composition and microstructure of all the synthesized copolymers was done by ¹H and ¹⁹F NMR spectroscopies. The monomer reactivity ratios of this new VDF/MAF-DMP pair were also determined (r_VDF = 0.76 ± 0.34 and r_MAF-DMP = 0 at 74 °C). The resulting poly(VDF-co-MAF-DMP) copolymers exhibited high melting temperature (162-171 °C, with respect to the VDF content), and the degree of crystallinity reached up to 51%. Finally, the pendant dimethyl phosphonate ester groups of the synthesized poly(VDF-co-MAF-DMP) copolymer were quantitatively hydrolyzed, giving rise to novel phosphonic acid-functionalized PVDF (PVDF-PA). In comparison to hydrophobic poly(VDF-co-MAF-DMP) copolymers (the water contact angle, WCA, was 98°), the hydrophilic character of the PVDF-PA was found to be surprisingly rather pronounced, exhibiting low WCA (15°). Finally, steel plates coated with PVDF-PA displayed satisfactory anticorrosion properties under simulated seawater environment.

Synthesis and self-assembly of carbamoylmethylphosphonate acrylamide-based diblock copolymers: new valuable thermosensitive materials

We report the synthesis by RAFT polymerization of well-defined diblock copolymers bearing carbamoylmethylphosphonate moieties which proved to sorb gadolinium. These poly(diethyl-6-(acrylamido)hexylcarbamoylmethylphosphonate-b-acrylic acid) (P(CPAAm6C-b-AA)) copolymers were able to self-assemble as a function of temperature, above their cloud point value.

Validating the alkene and alkyne hydrophosphonylation as an entry to organophosphonates

The hydrophosphonylation of terminal alkenes and alkynes by H-phosphonates affords Markovnikov and/or anti-Markovnikov adducts depending on the catalyst (a metal or a radical initiator) and the reaction conditions.