Poly P-phenylene Research Articles

Freestanding Bipolar Membranes with an Electrospun Junction for High Current Density Water Splitting.

Freestanding bipolar membranes (BPMs) with an extended-area water splitting junction were fabricated utilizing electrospinning. The junction layer was composed of a mixed fiber mat that was made by concurrently electrospinning sulfonated poly(ether ether ketone) (SPEEK) and quaternized poly(phenylene oxide) (QPPO), with water splitting catalyst nanoparticles intermittently deposited between the fibers. The mat was sandwiched between solution cast SPEEK and QPPO films and hot-pressed to form a dense trilayer BPM with an extended-area junction of finite thickness, composed of QPPO nanofibers embedded in a SPEEK matrix with the catalyst nanoparticles interspaced between the two polymers. The composition, ion-exchange capacity, and catalyst type/loading in the junction were varied, and the water splitting characteristics of the membranes were assessed. The best BPMs fabricated in this work employed a graphene oxide catalyst and exhibited a low trans-membrane voltage drop of about 0.82 V at 1000 mA/cm2 in water splitting experiments with 0.5 M Na2SO4 and stable water splitting operation for 60 h at 800 mA/cm2.

Investigations on the Creation of Promising Antifriction Polymeric Materials Based on Thermally Resistant Thermoplastics

The present review highlights the results of tribological studies on highly thermally resistant partially crystalline (Victrex poly(ether ether ketone) and poly(phenylene sulfide)) and amorphous (poly(arylene ether ketone)s) thermoplastics, which are promising for the creation of new antifriction materials that would be able to operate reliably under extreme conditions.

Enhancing anion conduction stability of quaternized poly(phenylene) oxide‐based anion exchange membranes with ionic liquids modified carbon nanomaterials

Enhancing anion conduction stability of quaternized poly(phenylene) oxide‐based anion exchange membranes with ionic liquids modified carbon nanomaterials

(Invited) Catalyst Layers for Fluorine-Free Hydrocarbon PEMFCs

Electrochemical energy conversion devices such as fuel cells are crucial for the development of renewable, sustainable alternative energy vectors. The implementation of fuel cell technology is of particular interest in portable, transportation, and stationary energy conversion sectors. There are challenges that still impede fuel cell commercialization at scale: cost, performance, and durability of the membrane-electrode-assemblies (MEA)s that comprise fuel cell stacks. MEAs typically consist of catalyst layers (CL) coated on either side of a proton-exchange membrane (PEM), and gas diffusion layers (GDL) which control water management and reactant gas mass transport. The CL provides a path for proton, electron, and gas transport to (and from) the Pt catalyst surface. Commonly, a perfluorosulfonic acid (PFSA) ionomer, e.g., Nafion® is employed as both the proton exchange membrane (PEM) and ionomer. However, perfluorinated materials are not without challenges as their manufacture utilizes controlled substances and potentially environmentally hazardous chemical feedstocks, which add to their relatively high cost. In contrast, fluorine-free hydrocarbon-based analogues may be prepared from ubiquitous, readily available chemical feedstocks, and afford much-reduced gas permeability. In this presentation, highly performing (power densities of >1 W cm-2), sulfo-phenylated poly(phenylene)PPB-H+ solid polymer electrolyte will be reported as a complete substitute for incumbent PFSA materials in PEMFCs, serving both as the electrode catalyst binder, and membrane.

Effect of activation time on sulfur-doped porous carbon for efficient degradation of organic pollutants with persulfate

Metal-free catalysis by using carbonaceous materials has propelled to the forefront in investigation of persulfate (PS) activation for green degradation of aqueous organic pollutants. Herein, sulfur-doped porous carbons (S-AC) were feasibly produced by chemical activation of Poly (phenylene sulphide) with KOH as activator. The influences of activation time on the porous structure, sulfur doping level, and chemical functionality of the as-prepared carbons were investigated by various characterization means. The S-AC samples were employed as metal-free catalysts to activate PS for phenol removal. Experiments results demonstrated that sulfur doping enhanced the catalytic activity of S-AC, and the S-AC-2 sample prepared by carbonization activation of 2 h was demonstrated to be a promising alternative to common metal oxides and other advanced carbon-based materials. Moreover, the S-AC-2/PS system could efficiently degrade various organics, which can be a green material for wastewater treatment and environmental remediation. In addition, the effects of various reaction parameters on phenol removal were discussed. It was found that S-AC-2 still presented an outstanding performance in a wide pH range. Furthermore, the PS activation mechanism over S-AC-2 was investigated by a series of classical radical quenching tests, EPR and Linear Sweep Voltammetry.

Electrodeposited poly(phenylene oxide) suppresses anodic parasitic processes in carbon-based supercapacitor electrodes operating in an aqueous electrolyte

Aqueous electrolytes, when compared to organic electrolytes, are safer, cheaper and usually enable a higher capacitance and lower internal resistance. However, their narrow operational voltage window (ca. 1.2 V) limits the device's energy density and, as such, their current commercial use is limited. Poly(phenylene oxide) was electrodeposited on the surface of activated carbon electrodes and has been shown to decrease the anodic parasitic current. The impact on the cathodic parasitic current was minimal. Comparison of the polarisation curves obtained in 1 M Na2SO4 (aq) for coated and uncoated electrodes between 0.5 V and 1.1 V vs Ag|AgCl demonstrated a >66% decrease in the exchange current density of anodic processes (from 10.1 μA/cm2 to 3.4 μA/cm2). Assuming supercapacitor degradation is proportional to the parasitic faradaic current, this change in the anodic parameters enables a 31% increase in the upper positive potential when a maximum parasitic current density of 29 μA/cm2 is considered acceptable. When these coated electrodes were mounted as symmetrical coin cells and operated at an increased voltage window of 1.5 V (up from 1.2 V), gains in energy and power densities were from 2.2 Wh/kg to 4.6 Wh/kg and 159 W/kg to 465 W/kg, respectively.

Theoretical investigation of the structural, optoelectronic, and the application of waste graphene oxide/polymer nanocomposite as a photosensitizer

The negligence of used waste polymers often results in the waste of resources and constitutes serious environmental pollutants. Therefore, it becomes necessary to practically provide a means of converting these waste polymers to useful resources. For this purpose, the potential applicability of some selected waste polymers as the active photosensitizer material in dye-sensitized solar cells were exploited using density functional theory. In this research work, density function theory (DFT) is applied to investigate the interaction of graphene oxide (GO) with monomers of Polypyrrole (PPy), Poly (phenylene vinylene) (PPV), Poly(vinyl alcohol) (PVA), and Polyvinyl Pyrrolidone (PVP) polymers. The geometrical structures of the hybridized nanocomposites GO-PPy, GO-PPV, GO-PVA, and GO-PVP are fully optimized at wB97XD/6–311++G(d,p) computational method. All of the nanocomposites’ optoelectronic properties, the excitation type and the wavelengths, oscillator strengths, as well as the dominant transitions were calculated. Atoms-in-molecules (AIM) and natural bond orbital (NBO) analysis were used to analyze the strength and nature of the composites. The results of the ground state energy gap revealed that the hybridized nanocomposites are semiconducting in nature while the 3.7020 eV energy gap of the GO-PVA makes it the most stable among the various nanocomposites. The thermodynamic calculation of the various nanocomposites shows that the GO-PVA nanocomposite is highly endothermic among the various nanocomposites with free energy value of 353.71kcal mol−1. The results of the density of state (DOS) analysis show that the p-orbitals in all of the different nanocomposites had the highest density contribution to the frontier molecular orbitals, and are also found to dominate the anti-bonding states densities.

Insights into the luminescent properties of poly(phenylene sulfide)-grafted metal-organic framework (Tb–MOF–PPS) copolymers

In this study, a novel poly(phenylene sulfide)-grafted metal-organic framework (Tb–MOF–PPS) was fabricated. Initially, 2,5-dichloroterephthalic acid and TbCl3·6H2O were used as raw materials to synthesize the dihalogenated MOF (Tb–MOF) through ultrasound irradiation and hydrothermal methods. Subsequently, Tb–MOF was added at different mole proportions (2.5, 5, 7.5, and 10%) for the copolymerization of PPS, and a serial of Tb–MOF–PPS composites were successfully obtained. Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy proved that the Tb–MOF was covalently connected to PPS. The introduction of the Tb–MOF had no evident influence on the thermal properties of the composites. Additionally, the fluorescence characteristics revealed that the fluorescence excitation and emission spectra of the composites had a large redshift compared with that of PPS and possessed visible-light photoluminescence properties. These results indicate that the composites obtained can be used as optical sensors.

Nonconformal Particles of Hyperbranched Sulfonated Phenylated Poly(phenylene) Ionomers as Proton-Conducting Pathways in Proton Exchange Membrane Fuel Cell Catalyst Layers

Characteristic poor electrochemical kinetics, high ionic resistance, and high mass transport resistance within the catalyst layer (CL) are chief among parameters that cause poor performance of proton exchange membrane fuel cells (PEMFCs) utilizing hydrocarbon-based proton-conducting ionomers. Herein, the design and addition of nondimensionally swellable, nonconformal, hyperbranched sulfo-phenylated poly(phenylene) ionomer particles (HB-sPPT-H+) are reported to introduce a direct pathway for proton conduction in hydrocarbon ionomer-based CLs, resulting in an eight times reduction in ionic resistance of the CL, a 71% increase in catalyst mass activity, and a >90% increase in power at 0.6 V (H2/air) compared to state-of-the-art hydrocarbon ionomer-based CLs. The benefits of incorporating HB-sPPT-H+ ionomer particles are also shown when employed in perfluorosulfonic acid (PFSA) ionomer-based PEMFCs. These results dispel a commonly held conception that hydrocarbon ionomers possess limitations of gas permeability and electrochemical activity and open up previously unexplored avenues of ionomer development for nonfluorous, wholly hydrocarbon PEMFCs.

Photocatalytic membranes containing homocoupled conjugated microporous poly(phenylene butadiynylene) for chemical-free degradation of organic micropollutants

Polysulfone-based nanofiltration membranes containing homocoupled conjugated microporous poly(phenylene butadiynylene) (HCMP) were prepared via phase inversion to study the chemical-free degradation of organic micropollutants. The cumulative adsorptive-photocatalytic effect was higher for the membrane containing HCMP, M0.5HCMP (99%), compared to reference membrane, M0 (74%). Rhodamine B (RhB) rejections of 95% and 96% were found for M0 and M0.5HCMP membrane, respectively, with permeances of 6.91 L m−2 h−1 bar −1 and 2.15 L m−2 h−1 bar −1. The HCMP-containing membrane showed good stability in long-term activity testing after 8 cycles in the photocatalytic experiments.

A self-assembled nanostructure from an amphiphilic aromatic polyester containing siloxane and poly(phenylene oxide) in epoxy resin

A self-assembled nanostructure from an amphiphilic aromatic polyester containing siloxane and poly(phenylene oxide) in epoxy resin

Simultaneous improvement of anion conductivity and cell durability through the formation of dense ion clusters of F-doped graphitic carbon nitride/quaternized poly(phenylene oxide) composite membrane

Here, we present a series of organic-inorganic composite membranes using graphitic carbon nitride (gC 3 N 4 ) derivatives (porous (p-) gC 3 N 4 ) and F-doped porous (F-p-) gC 3 N 4 ) to improve the electrochemical properties and dimensional stability for anion exchange membranes (AEMs). The introduction of F-p-gC 3 N 4 onto a quaternized poly(phenylene oxide) (QPPO) matrix induced the expansion of the ion channel by promoting nanophase separation, and the composite membranes possess high ion conductivity (>142.1 mS cm −1 at 90 °C, i.e., 1.75 times as high as the pristine membrane) and suitable alkaline durability (>74% ion conductivity in 1 M KOH at 80 °C for 30 days) with enhanced dimensional change. Importantly, H 2 -O 2 fuel cell performance of QPPO/F-p-gC 3 N 4 -0.5 reached a maximum peak power density of 286.2 mW cm −2 at 60 °C. In addition, the QPPO/F-p-gC 3 N 4 -0.5-based membrane electrode assembly can be operated under 0.15 A cm −2 current density at 60 °C for 100 h. Thus, this strategy could be suitable for future work on AEM applications. • The F-doped porous gC 3 N 4 (F-p-gC 3 N 4 ) was prepared for anion exchange composite membranes. • The composite membrane showed superior ion conductivity of 142.1 mS cm −1 with suitable dimensional stability. • The ion conductivity of composite membrane was well-retained after alkaline stability >30 days in 1 M KOH at 80 °C. • The H 2 -O 2 fuel cell performance exhibited the highest peak power density of 286.2 mW cm −2 . • The prepared composite membrane exhibited long-term stability at 60 °C for 100 h.

Functionalization of Water-Soluble Conjugated Polymers for Bioapplications.

Water-soluble conjugated polymers (WS-CPs) have found widespread use in bioapplications ranging from in vitro optical sensing to in vivo phototherapy. Modification of WS-CPs with specific molecular functional units is necessary to enable them to interact with biological targets. These targets include proteins, nucleic acids, antibodies, cells, and intracellular components. WS-CPs have been modified with covalently linked sugars, peptides, nucleic acids, biotin, proteins, and other biorecognition elements. The objective of this article is to comprehensively review the various synthetic chemistries that have been used to covalently link biofunctional groups onto WS-CP platforms. These chemistries include amidation, nucleophilic substitution, Click reactions, and conjugate addition. Different types of WS-CP backbones have been used as platforms including poly(fluorene), poly(phenylene ethynylene), polythiophene, poly(phenylenevinylene), and others. Example applications of biofunctionalized WS-CPs are also reviewed. These include examples of protein sensing, flow cytometry labeling, and cancer therapy. The major challenges and future development of functionalized conjugated polymers are also discussed.

Synthesis of Giant Dendritic Polyphenylenes with 366 and 546 Carbon Atoms and Their High-vacuum Electrospray Deposition.

Dendritic polyphenylenes (PPs) can serve as precursors of nanographenes (NGs) if their structures represent 2D projections without overlapping benzene rings. Here, we report the synthesis of two giant dendritic PPs fulfilling this criteria with 366 and 546 carbon atoms by applying a “layer‐by‐layer” extension strategy. Although our initial attempts on their cyclodehydrogenation toward the corresponding NGs in solution were unsuccessful, we achieved their deposition on metal substrates under ultrahigh vacuum through the electrospray technique. Scanning probe microscopy imaging provides valuable information on the possible thermally induced partial planarization of such giant dendritic PPs on a metal surface.

Macromolecular Engineering and Additive Manufacturing of Polyisobutylene-Based Thermoplastic Elastomers. II. The Poly(styrene-b-isobutylene-b-styrene)/Poly(phenylene oxide) System.

This series of publications describes research rendering soft polyisobutylene (PIB)-based thermoplastic elastomers 3D printable by blending with rigid chemically compatible thermoplastics. The molecular structure, morphology, physical properties, and 3D printability of such blends have been systematically investigated. The authors' first report was concerned with the rendering of soft poly(styrene-b-isobutylene-b-styrene) (SIBS) 3D printable by blending with rigid polystyrene (PS). Here they report the macromolecular engineering of SIBS/polyphenylene oxide (PPO) blends for 3D printing. PPO, a rigid high-performance thermoplastic, is compatible with the hard PS block in SIBS; however, neither PPO nor SIBS can be directly 3D printed. The microphase-separated structures and physical properties of SIBS/PPO blends are systematically tuned by controlling blending ratios and molecular weights. Suitable composition ranges and desirable properties of SIBS/PPO blends for 3D printing are optimized. The morphology and properties of SIBS/PPO blends are characterized by an ensemble of techniques, including atomic force microscopy, small-angle X-ray scattering, and thermal and mechanical properties testing. The elucidation of processing-structure-property relationship of SIBS/PPO blends is essential for 3D printing and advanced manufacturing of high-performance polymer systems.

Optimized step‐growth polymerization of water‐insoluble, highly sulfonated poly(phenylene sulfone)

AbstractDue to its potential for fuel cell applications, the synthesis of sulfonated poly(phenylene sulfone) with an ion‐exchange capacity (IEC) of 2.78 mequiv g−1 (sPPS‐360) is optimized and the effect of increased molecular weight on mechanical properties studied. The synthesis comprises the step‐growth polymerization of sulfonated difluorodiphenylsulfone (sDFDPS) with thiobisbenzenethiol (TBBT), followed by an oxidation (via hydrogen peroxide). In the past, this procedure was marked by very low reproducibility and often limited achievable molecular weight. Sodium sulfate—a by‐product in the preparation of sDFDPS—is found to be retained throughout the monomer's established purification procedure via recrystallization from alcohol/water mixtures. The contamination is quantified by atomic absorption spectroscopy (AAS) and combustion analysis. At corrected monomer ratios, the preparation of sPPS‐360 is highly reproducible and a subsequent optimization of synthetic parameters yields a significant increase in number average molecular weight (typical Mn 15–30 kDa up to 154 kDa). Improved viscoelastic properties of optimized sPPS‐360s are evident in tensile tests at 30 %RH, better membrane‐forming properties and reduced water uptake (when submerged in water).

Poly(phenylene sulfonic acid)-expanded polytetrafluoroethylene composite membrane for low relative humidity operation in hydrogen fuel cells

A composite fuel cell membrane based on highly proton conductive, thermally crosslinkable poly(phenylene sulfonic acid) (cPPSA) copolymer is prepared by pore filling, to overcome the copolymer's poor mechanical characteristics. The membrane comprises a mechanically stabilizing scaffold from a commercial, expanded polytetrafluoroethylene (ePTFE) porous film, which is impregnated with cPPSA, followed by its thermal crosslinking. The membrane has a very high proton conductivity, 3.5 and 3.0 times higher that of a Nafion XL reference, at 80 °C and 40 %RH, and 90 %RH, respectively. Membrane-electrode assemblies fabricated with this membrane and commercial Pt/C-based electrodes (0.12 mgPt cm−2) are tested in hydrogen fuel cell with air and oxygen, at 80 °C. High power output and low gas crossover are observed. For example, with a 15 μm-thick cPPSA-ePTFE PEM, the maximum power density at 80 °C and 100 kPa backpressure, decreases by only 15%, from 1.00 W cm−2 to 0.85 W cm−2, when the RH of the hydrogen and air feeds are reduced from 100% to 30%. In comparison, a MEA with Nafion XL shows a significant, 52% loss, from 0.82 W cm−2 to 0.39 W cm−2, during similar reduction of fuel cell humidification.

Development of Planar Orientation in Polymer Processing

Abstract A critical discussion is presented of the development of planar orientations in various polymer processing operations. These include tubular blown film and subsequently drawn and multiply stretched blown films. The response of polyethylene, various nylons, poly(ethylene ter ephthalate), cellulose and poly(p-phenylene terephthalamide) are discussed.

One- and Two-Photon Activated Release of Oxaliplatin from a Pt(IV)-Functionalized Poly(phenylene ethynylene).

We report a water-soluble poly(phenylene ethynylene) (PPE-Pt(IV)) that is functionalized with oxidized oxaliplatin Pt(IV) units and its use for photoactivated chemotherapy. The photoactivation strategy is based on photoinduced electron transfer from the PPE backbone to oxaliplatin Pt(IV) as an electron acceptor; this process triggers the release of oxaliplatin, which is a clinically used anticancer drug. Mechanistic studies carried out using steady-state and time-resolved fluorescence spectroscopy coupled with picosecond-nanosecond transient absorption support the hypothesis that electron transfer triggers the drug release. Photoactivation is effective, producing oxaliplatin with a good chemical yield in less than 1 h of photolysis (400 nm, 5 mW cm-2). Photorelease of oxaliplatin from PPE-Pt(IV) can also be effected with two-photon excitation by using 100 fs pulsed light at 725 nm. Cytotoxicity studies using SK-OV-3 human ovarian cancer cells demonstrate that without photoactivation PPE-Pt(IV) is not cytotoxic at concentrations up to 10 μM in polymer repeating unit (PRU) concentration. However, following a short period of 460 nm irradiation, oxaliplatin is released from PPE-Pt(IV), resulting in cytotoxicity at concentrations as low as 2.5 μM PRU.

Electrode optimization for efficient hydrogen production using an SO2-depolarized electrolysis cell

The hybrid sulfur (HyS) cycle offers an alternative route to hydrogen and sulfuric acid production using the SO2-depolarized electrolysis (SDE) cell. This work reports the most efficient SDE operation to date at high sulfuric acid concentrations (∼60 wt%) achieved through the optimization of operating conditions and cell components. We observed that open porosity in the porous transport media (PTM) plays a significant role in SDE performance as it enables efficient acid removal from the catalyst layer. The combination of membrane electrode assembly (MEA) components, such as Sulfonated Diels Alder Poly (phenylene) (SDAPP) membranes and electrodes prepared using SGL 29BC PTM, and operating conditions (103.4 kPagauge at 125 °C) yielded electrolysis potentials <700 mV at 500 mA/cm2 and acid concentrations >60 wt%.