Search

Aqueous zinc ion hybrid capacitors (ZIHCs) hold great potential for large-scale energy storage applications owing to their high safety and low cost, but suffer from low capacity and energy density. Herein, pyridinic nitrogen enriched porous carbon (nPC) was successfully synthesized via the growth, subsequent annealing and acid etching of bimetal organic frameworks for high capacity and safe ZIHCs with exceptional rate capability. Benefiting from the mesopores for easy ion diffusion, high electrical conductivity enabled by in-situ grown carbon nanotubes matrix and residual metal Co nanoparticles for fast electron transfer, sufficient micropores and high N content (8.9 at%) with dominated pyridinic N (54%) for enhanced zinc ion storage, the resulting nPC cathodes for ZIHCs achieved high capacities of 302 and 137 mAh g−1 at 1 and 18 A g−1, outperforming most reported carbon based cathodes. Theoretical results further disclosed that pyridinic N possessed larger binding energy of −4.99 eV to chemically coordinate with Zn2+ than other N species. Moreover, quasi-solid-state ZIHCs with gelatin based gel electrolytes exhibited high energy density of 157.6 Wh kg−1 at 0.69 kW kg−1, high safety and mechanical flexibility to withstand mechanical deformation and drilling. This strategy of developing pyridinic nitrogen enriched porous carbon will pave a new avenue to construct safe ZIHCs with high energy densities.

Anion exchange membranes (AEMs) with high conductivity and superior stability against the attack from the strong alkali working medium are highly needed. The graphene oxide (GO) having the lamellar structure of about 1.5 nm in thickness was first modified with 1-(2-(dimethylamino)ethyl)-1H-tetrazole-5-thiol and followed by quaternization of the 2-(dimethylamino)ethyl group with (5-bromopentyl) trimethylammonium bromide. The quaternized graphene oxide (QGO) was doped into quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO) to fabricate the AEMs with comprehensive properties. The introduced QGO obviously changed the microphase structure of the membranes with more ion clusters for ion conduction according to the images taken by atomic force microscope. The prepared membrane doping with 0.25 wt% QGO reached a hydroxide conductivity of 75 mS cm−1 at 80 °C. Moreover, the prepared hybrid membranes exhibited improved alkaline stability, enhanced Young’s modulus of more than 600 MPa, and low methanol permeability in the 10−7 cm2 s−1 order of magnitude compared to the pristine QPPO membrane. Working as the radical scavenger, the introduced QGO endowed the hybrid membrane with conductivity retaining rate of about 84% after immersed in 2 M KOH solution at 60 °C for 360 h, while the pristine QPPO membrane retained its original conductivity of 56%.

Uniformly introducing inorganic additives into polymer matrix could effectively improve the properties of the polymer membranes. Herein, the ZrO2 nanoparticles containing a surfactant cetyltrimethylammonium bromide (CTAB), denoted as sZrO2, were synthesized and used as an additive to prepare anion exchange membranes (AEMs) based on 1-methylpyrrolidinium quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (MPPO). The presence of the surfactant effectively improved the compatibility of the inorganic filler and the polymer matrix according to the morphology analysis. Compared to those of the MPPO membrane, the conductivities and tensile strengths of the composite membranes increased by 10–29% and 38–63%, respectively, benefiting from the presence of the sZrO2 and the leave-in surfactant CTAB. A hydroxide conductivity of 88.7 mS cm−1 was achieved in water at 80 °C by the MPPO-1.0 wt%sZrO2 membrane. Moreover, 74.2% of its initial conductivity were retained after immersed the membrane in 1 M KOH at 80 °C for 408 h. This membrane-based single fuel cell exhibited a peak power density of 515.6 mW cm−2 at 60 °C by fueling with humidified H2 and O2 with 0.1 MPa back pressure. More characterizations on the structures of associated materials by using FT-IR, 1H NMR, TEM, and X-Ray Diffraction were made as well.

Metal nitrides with high theoretical capacities and exceptional electrical conductivities hold great potentials as high-rate anode materials for lithium ion batteries (LIBs), but suffer from severe pulverization and air instability of electrodes. Herein, we developed a general strategy for synthesizing few-layer graphene encapsulated transition metal nitride (e.g., Fe2N) nanoparticles confined in three dimensional (3D) ultrathin carbon nanosheet frameworks (denoted as Fe2N@CNFs) via the iron nitrate accelerated polyvinylpyrrolidone (PVP) blowing and subsequent in-situ nitridation process, as high-rate anode for LIBs. Benefiting from the well-confined Fe2N nanoparticles by graphene shells for alleviating structural pulverization and air sensitivity, and 3D carbon nanosheet porous frameworks for fast electrolyte ion diffusion and fast electron transport, the resulting Fe2N@CNFs anodes exhibited high reversible capacity of 587 mA h g−1 at 0.1 A g−1, and remarkable rate capacity of 215 mA h g−1 at high current density of 10 A g−1, outperforming most reported metal nitride electrodes. When coupled with carbon-coated LiFePO4 cathode, the resulting full LIBs still delivered an initial discharge capacity of 243 mA h g−1 at 0.1 A g−1. Therefore, this work will pave a new way for rational construction of a series of high-performance metal nitride electrodes for energy-related devices.

White space is an artistry concept widely used in Chinese painting and calligraphy. It conveys useful information for the readers while retaining certain imagination space for them. Inspired by this artistry, we probe into the white space designing in chemistry education and scientific training in colleges/universities. A few examples are illustrated for the utilization of white spaces in scientific knowledge teaching with detailed discussions. These include half-life time of dynamic studies, mathematical derivation of chemical calculations, equilibrium of chemical reactions and phases of thermodynamics, as well as data processing in scientific studies & developments. Designing white space in lectures/presentations aims to rhythmize the teaching process and to prevent fatigue from both the lecturer and students by cutting off lengthy talking. Moreover, leaving suitable white space in the teaching content may arouse the curiosity of students, stimulate the desire for their exploration, and therefore enrich their learning experiences. We herein propose the designing of appropriate white space in college chemistry education with pernitent examples to promote further discussions on this issue.

The organic-inorganic hybrid anion exchange membranes were prepared from quaternary triethylamonium functionalized poly(2,6-dimethyl-1,4-phenyleneoxide) (QPPO) and 3-glycidoxypropylthrimethoxysilane (GOPS) with different ratios. The obtained membranes are termed as QPPOx-Gy, where x and y are the mole ratios of triethylamine and the siloxane GOPS to the bromomethyl groups of the polymer, respectively. The resultant hybrid membranes are thermally stable up to 200 °C and exhibit a tensile stress of around 10 MPa. The incorporated GOPS endows the hybrid membranes with increased water uptake and conductivity due to the more hydroxyl groups containing in the hydrolytic networks of GOPS in the membranes. A conductivity of 46.0 mS cm−1 is achieved by the QPPO0.4-G0.55 membrane in water at 80 °C, which is about 20 mS cm−1 higher than the conductivity of the pristine QPPO0.4 membrane. In addition, the QPPO0.4-Gy hybrid membranes possess enhanced alkaline tolerance toward the attack of hydroxide ions. After soaked in 1 M KOH at 60 °C for 480 h, the hybrid membranes retained more than 16–22% of the initial conductivity compared to the pristine QPPO0.4 membrane.

Poly(vinylpyrrolidone) (PVP), as the low-cost and commercial material, exhibits superior phosphoric acid doping capability due to the presence of heterocycle and carbonyl groups in the repeat unit. However, it can’t be used as the high temperature polymer electrolyte membrane (HT-PEM) alone because of its significant hydrophilicity and poor mechanical stability. In the present work, polyethersulfone (PES), polysulfone (PSU), polyetherketone-cardo (PEK-c), polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-co-hexafluoropropylene) (PHFP), five kinds of engineering thermoplastics with excellent mechanical properties and chemical inertness, are chosen to prepare a series of PVP blend membranes by the polymer blending method in order to enhance the dimensional and mechanical stabilities of PVP based membranes. The influence of structures of enhanced polymers on properties of HT-PEMs was investigated systematically. PVP blend membranes with aromatic polymers (i.e. PES, PSU and PEK-c) exhibited decreased volume swellings, increased acid doping contents, superior conductivities and improved mechanical strengths, which determined that they are more suitable for electrolytes of fuel cell applications comparing with PVP/PVDF and PVP/PHFP membranes blended with aliphatic polymers.

Anion exchange membranes with star main chains or side chains were prepared by grafting the 1-butyl-2-methylimidazole and/or 1-aminopropyl-2-methyl-3-butylimidazolium hydroxide onto branched or linear poly(aryl ether ketone) polymers. In order to know the influence of the star structures on the physicochemical properties of the prepared membranes, comprehensive characterizations were made including ion exchange capacity, conductivity, mechanical property and alkaline stability. All the membranes exhibit conductivities of about 40 mS cm−1 at 60 °C and about 60 mS cm−1 at 80 °C, respectively. The durability of the membranes in alkaline medium was detected by monitoring the changes in conductivity, ion exchange capacity and contact angle with water. The results indicate that the introduced star structures of both main chains and side chains are effective to enhance the tensile strength and alkaline stability of the membranes. The membranes with star main chains exhibited a tensile stress at break of 45 MPa and retained a conductivity of 36.1 mS cm−1 at 60 °C after exposed to 1 M KOH at 80 °C for 300 h.

Possessing high ionic conductivity is required to polymer-based membrane electrolytes. However, it is a challenge to evaluate the conductivity based on the structure of the polymer membrane without any measurements. We present a deep learning protocol to predict the hydroxide ion (OH-) conductivity from chemical structure information of poly (2,6-dimethyl phenylene oxide)-based anion exchange membranes (AEMs) grafting with one kind of functional cationic group. The modeling process includes data collection and feature processing, functional cationic group identification, OH- conductivity prediction and scientific law extraction. The established model achieves 99.7% of accuracy for classifying various functional cationic groups. The prediction error in OH- conductivity is ± 0.016 S/cm for quaternary ammonium based AEMs, ± 0.014 S/cm for saturated heterocyclic ammonium based ones, and ± 0.07 S/cm for those possessing imidazolium cations. The proposed protocol is powerful to assist researchers in designing the AEMs with predictable OH- conductivity, and provides a new research paradigm of the AEMs preparation.

Novel high temperature proton exchange membranes, quaternized poly(aryl ether sulfone) (QPAES), were prepared using triethylamine (TEA) as quaternization reagent and (N,N-diethyl-3-aminopropyl) trimethoxysilane (EPMS) as the crosslinking agent, respectively. To improve the mechanical strength and dimensional stability of the membranes, the crosslinked structure of Si O Si network was formed by hydrolyzing siloxane groups of EPMS. Compared with the non-crosslinked membrane, the crosslinked PAES membranes displayed significantly enhanced mechanical properties, improved dimensional stabilities as well as high conductivities. The QPAES-10EPMS-90TEA membrane with a phosphoric acid doping level of 12.1 exhibited a tensile strength of 9.16 MPa at room temperature, and a conductivity of 74.8 mS cm−1 at 180 °C under no humidification conditions.

We employed four radical inhibitors to investigate their influences on the degradation of poly (4-vinylbenzyl chloride-styrene) based anion exchange membranes (AEMs) in alkaline solutions. It is found that the presence of the radical inhibitors could effectively restrain the nucleophilic attack of hydroxide ions to the AEMs according to the conductivity measurements, especially the one p -ethyl phenol (PEP), which could significantly protect the AEMs against the attack. More evidences including water uptake, swelling ratio as well as FT-IR analysis further proved this phenomenon by comparison those properties of the membranes before and after the stability test in 8 M KOH at 80 °C for 24 h. According to the 1 H NMR spectra, the quaternary ammonium groups of the AEMs were mainly degraded into tertiary amines in the hot alkaline solutions; while in the presence of PEP, this degradation was restrained and the quaternary ammonium groups maintained by reaction with PEP. Fenton test results further indicated that high oxidative stability of the AEMs benefited from the presence of a small amount of PEP, which could reduce the generation of the oxidants. Thus an inhibition reaction mechanism of the radical inhibitors preventing the AEMs from alkaline degradation is proposed.

Two trifunctional bromomethyls containing crosslinkers, 1,3,5-tris(bromomethyl)benzene (B3Br) and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene (Be3Br), are employed to covalently crosslink polybenzimidazole (PBI) membranes for the high temperature proton exchange membrane fuel cell. The presence of three bromomethyl groups in each crosslinker molecule is expected to create more free volume for acid doping while enhancing the adhesive strength of the PBI chains. In addition, the influence of the two crosslinker structures on the property of the crosslinked membranes is compared and analyzed. All the crosslinked PBI membranes exhibit longer morphology durability over the pristine PBI membrane toward the radical oxidation. Moreover, the crosslinked PBI membranes with the crosslinker Be3Br containing three ethyl groups display superior acid doping level, high conductivity and excellent mechanical strength simultaneously, over those with the crosslinker B3Br and the pristine PBI membrane. Single cell measurements based on the acid doped membrane with a crosslinking degree of 7.5% by Be3Br demonstrate the technical feasibility of the prepared membranes for high temperature proton exchange membrane fuel cells.

A 1-decyl-2-methylimidazole (DMIm) functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membrane is fabricated and employed to dope phosphoric acid (PA) for use as a high temperature proton exchange membrane. This kind of membrane displayed superior PA doping capability, but poor mechanical properties. In order to improve the dimensional and mechanical stabilities without sacrificing proton conductivities, a series of dual cross-linked membranes are prepared using the poly(styrene-vinylimidazole-divinylbenzene) (poly(St-VIm-DVB)) copolymer as a crosslinker. The reaction of vinylimidazole with benzyl bromide not only constructs a cross-linking network, but also endows the membranes with a PA doping capacity for proton conduction. The reticular polymer chain structure improves the mechanical properties of the membranes, especially at elevated temperatures. As an example, PPO-70%VIm-30%DMIm/180.1%PA achieves a high proton conductivity of 0.067 S cm−1 at 180 °C without humidification, while it displays suitable tensile strengths of 5.0 MPa and 2.1 MPa at room temperature and 120 °C, respectively. These membranes show great potential for use as an electrolyte in high temperature proton exchange membrane fuel cells.

The trade-off between proton conductivity and mechanical property is a critical issue to phosphoric acid (PA) doped high temperature proton exchange membranes (HT-PEMs) for using as the electrolytes in various devices. Uniformly introducing additives into polymer matrix is required for improvements on the properties of the polymer membranes. Herein, the hydrophilic and acidophilic octa-amino polyhedral oligomeric silsesquioxane (OA-POSS) is synthesized for using as a filler and a crosslinker concurrently to prepare HT-PEMs based on poly(aromatic ether sulfone) (PAES). The PA doped membrane with a crosslinking degree of 10% exhibits a proton conductivity of 97.4 mS cm−1 at 180 °C without humidifying, and an enhanced tensile stress of 8.5 and 2.4 MPa under ambient atmosphere and 110 °C, respectively, which are about 60% and 70% higher than those of the pristine quaternary ammonium PAES membrane. A peak power density of 461 mW cm−2 is achieved by the membrane at 200 °C by fueling the fuel cell with non-humidified H2 and O2 without backpressure. Comprehensive characterizations on the structure, PA doping level, anhydrous proton conductivity, as well as dimensional stability and PA retention ability of the prepared membranes are made.

The anion exchange membranes (AEMs) possessing a long-term alkaline stability is desired for use as the electrolyte in electrochemical devices. We prepared a series of AEMs with excellent stability and reasonable conductivity as well as acceptable mechanical properties by addition of antioxidants into quaternary ammonium modified poly(4-vinylbenzyl chloride-styrene). It is found that the synergy of hindered phenol and diphosphite antioxidants endowed the AEMs with superior resistance to the attack of both OH– ions and free radicals. The proposed membrane retained about 80% of the original conductivity after soaked in 2 M KOH aqueous solutions at 60 oC for 1300 h. The synergy effect of the dual antioxidants was investigated by Fenton tests and the fluorescence analysis. A peak power density of 526 mW cm−2 was achieved at 60 oC by the membrane-based single fuel cell fueling with humidified H2 and O2 without back pressure.

The chemical durability is a critical issue to proton exchange membranes (PEMs) for using as the electrolyte in proton exchange membrane fuel cells (PEMFCs). Herein, chemically stable membranes were prepared by grafting organic free radical scavengers (R) including 2-mercapto-1-methylimidazole (MIm), 3-mercapto-1,2,4-triazole (MTz) and 2-mercaptobenzimidazole (BIm) onto backbones of polyarylethersulfone (PAES), respectively. Having a phosphoric acid (PA) doping level of around 200 wt%, the PAES-MIm and PAES-MTz membranes exhibit, separately, anhydrous proton conductivities of 78.3 and 63.3 mS cm−1 at 180 °C, tensile stress at break of 7.8 and 9.4 MPa at room temperature, and a peak power density of 423 mW cm−2 and 358 mW cm−2 at 160 °C with a fuel cell fueling with non-humidified gases of H2 and O2. The properties of the prepared PAES-MIm and PAES-MTz membranes with and without performing the Fenton tests were all investigated on tensile stress, methanol permeability, anhydrous proton conductivity, and polarization curves of single fuel cells, respectively. The results indicate that the grafted free radical scavengers significantly enhanced the chemical stability and retarded the degradation of the PAES-R membranes. After suffered the Fenton test under harsh conditions (H2O2, 3 wt%, Fe2+, 4 ppm at 68 °C) for 60 and 100 h, a peak power density of 320 and 291 mW cm−2 is still achieved at 140 °C by the acid doped PAES-MIm membranes, respectively. Characterizations on the morphology by scanning electron microscope (SEM), and structure by Raman spectroscopy of the prepared membranes were made as well.

Two N3-substituted imidazoles 1,2-dimethylimidazole and 1-butyl-2-methylimidazole were chosen to functionalize poly(aryl ether ketone), respectively. The generated imidazolium cations could electrostatically react with sulfonate ions of the sulfonated poly(ether ether ketone) forming the ionic crosslinking structure of the membranes. The changes in crosslinking degree and the alkyl chain-length on N3 site of the imidazoliums could highly affect the properties of the anion exchange membranes (AEMs). The AEMs functionalized by 1-butyl-2-methylimidazole exhibited superior properties compared to those functionalized by 1,2-dimethylimidazole according to the tolerance tests of the AEMs towards hot alkaline solutions. After exposed to 1M KOH at 80°C for 200h, the 1-butyl-2-methylimidazole modified AEMs maintained the ion exchange capacity of above 85%, the conductivity of about 70%, and the tensile stress at break of around 80%, respectively. The hydrophile-lipophile balance of the polymer membranes was calculated and proposed to better understand the correlation between structures and properties of the AEMs. The degradation of the imidazolium functional groups of the AEMs under the attack of hydroxide ions was evidenced by FT-IR analysis.

17β‑estradiol (E2) and aquaporin 2 (AQP2) are associated with endometrial receptivity, and E2 directly regulates AQP2 expression in endometrial cancer cells. The present study aimed to investigate the role of AQP2 in embryo implantation. Normal endometrial samples were collected at the Women's Hospital (Hangzhou, China) from women seeking in vitro fertilization and embryo transfer; women with endometrial abnormalities were excluded from the study. Samples were categorized into early‑mid proliferative, late proliferative, early secretory, mid‑secretory and late secretory phase groups, according to the menstrual cycle. The mRNA and protein expression levels of AQP2 were assessed in normal human endometrium in response to E2 via reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. The effects of AQP2 on spheroid attachment were assessed using an in vitro co‑culture assay with small interfering (si)RNA against AQP2. The highest expression levels of AQP2 were observed in the late proliferative and mid‑secretory phases, with the lowest levels detected in the early proliferative and late secretory phases. In addition, treatment with 10‑9 or 10‑7 M E2 for 24 h upregulated AQP2 in the cultured endometrium. Knockdown of AQP2 by siRNA significantly decreased JAr spheroid attachment; however, this effect was significantly reversed when AQP2 siRNA‑transfected cells were treated with 10‑7 M E2. The results of the present study suggested that AQP2 expression levels in human endometrium may be mediated by estrogen, and low AQP2 expression levels may be a potential cause of impaired uterine receptivity.

Novel organic-inorganic composite membranes were prepared conveniently by compositing of carbon dots (CDs) possessing different hydrophilicity into the low cost blended polymers of polyvinylpyrrolidone (PVP) and polyethersulfone (PES). The hydrophilicity of the CDs arises from its surface hydrophilic groups, which could be adjusted by controlling the reaction temperature and duration time. A series of homogeneous composite membranes doping with different hydrophilic CDs of up to about 10 wt% were obtained. Comprehensive characterizations were made in order to know the influence of different hydrophilic CDs on the properties of the prepared membranes. It is found that the doped CDs could cause the change in microphase separation and benefit proton conduction of the composite membranes. The more doped CDs, the higher the conductivity. A highest conductivity of 0.086 S cm−1 was reached by a composite membrane doped with both hydrophilic and hydrophobic CDs. Moreover, the incorporated CDs brought on the changes in properties of the composite membranes including free volume, hydrophilicity, acid doping level and swelling. A single fuel cell test was made based on the CDs blended membrane and indicating its potential to be used as the membrane electrolyte in high temperature proton exchange membrane fuel cells.

It is found that free radicals of OH would be generated in KOH solutions at elevated temperatures according to the results of fluorescence analysis. Five kinds of radical inhibitors (tert-butylphenol-containing reagents, 4-amino-tempo, benzophenone, phenothiazine and N-phenyl-1-naphthylamine) were employed as the dopant, separately, to prepare anion exchange membranes (AEMs) based on poly(4-vinylbenzylchloride-styrene). The investigaions on the properties of the prepared AEMs indicate that more radicals might be produced during the degradation of the AEMs via chain propagation reactions. Moreover, the influences of the radical inhibitors on the degradation of the AEMs in 8 M KOH solutions at 80 °C are quite different although all these inhibitors could react with OH radicals. Therein the radical inhibitors o-, m-, p-tert-butylphenols could effectively enhance the chemical stability of the AEMs. However, when the phenol-containing inhibitors have a large substituent group in its benzene ring, the membranes tend to be brittle during the stability test.

A suitable microphase separation morphology has been demonstrated to be an efficient strategy to achieve high ionic conductivity with reasonable durability to anion exchange membranes (AEMs). Herein, hydrophilic oligomers of polyethylene glycols (PEGs) with different molecular weights were blended, separately, with poly(2,6-dimethyl-1,4-phenylene oxide) modified by 4,4-diethoxybutan-1-amine and 1-methylpiperidine (20PDM). The presence of hydrophilic PEGs facilitates the formation of the interconnected nano-channels in the AEMs for ion conduction according to the analysis results by both transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The membrane containing 2 wt% PEGs with a molecular weight of 2 kDa reaches a hydroxide conductivity of 97.2 mS cm−1 at 80 °C, which is 25 mS cm−1 higher than that the pristine 20PDM membrane possessing the same ion exchange capacity. A peak power density of 328 mW cm−2 is attained at 60 °C by the proposed membrane based single fuel cell fueling with humidified H2 and O2 with 0.1 MPa of back pressure. The chemical structure, water uptake and swelling as well as resistance to hot alkali solutions of the prepared membranes were investigated.

One critical issue to phosphoric acid (PA) doped high-temperature proton exchange membranes (HT-PEMs) is to balance the proton conductivity and mechanical properties for overall application performance in fuel cells. Addressing the issue, we prepare durable HT-PEMs having the dual crosslinking structure by employing poly(vinylimidazole-divinylbenzene-styrene) (poly(VIm-DVB-St)) copolymer as a crosslinker and using the poly (aromatic ether ketone) (PAEK) polymer containing four methyl groups as the host membrane matrix. The imidazole groups of poly(VIm-DVB-St) react with benzyl bromide groups of brominated PAEK for both the primary cross-linking network and high PA doping. The divinylbenzene crosslinked poly (styrene-co-vinylimidazole) network generates the secondary cross-linking structure. The formed reticular polymer chain structure brings on low swelling and high mechanical strength of the HT-PEMs. The fuel cell based on the acid doped PAEK41-85%VIm/233.0 PA shows a H2-air fuel cell peak power density of 306 mW cm−2 at 200 °C without back pressure, and a low degradation rate of 3.9 × 10−5 V h−1 during a period of 600 h under a constant current density of 200 mA cm−2 at 160 °C.

Imidazolium-type anion exchange membranes (AEMs) were prepared by functionalization of bromomethylated poly(2,6-dimethyl-1,4-phenyleneoxide) with six kinds of imidazole compounds, respectively, to investigate the correlation of the grafted imidazolium structure and the physicochemical properties of the membrane. The chemical structure of substituted groups in imidazolium cations would highly influence the ion exchange capacity, ionic conduction, mechanical strength, as well as stability in strong alkaline solutions of the AEMs. The membrane having C2-methyl and N3-butyl substituted groups in the imidazolium pendants exhibited superior properties among the prepared AEMs, i.e., an IEC of around 1.03 mmol g −1 , hydroxide ion conductivity of 42.5 mS cm −1 at 80 °C, and tensile strength at break of 15.0 MPa, respectively. In addition, this membrane showed high alkaline stability and no obvious decline in conductivity was observed after being exposed to 1 M KOH at 60 °C for 180 h.

Low cost poly(epichlorohydrin) (PECH) was modified with imidazolium groups to prepare high temperature proton exchange membranes. Chloromethyl groups in the structure of the PECH benefit its modification with no need for highly toxic and carcinogenic chloromethylation reagents. Both methylimidazole (MeIm) and triethoxysilylpropyldihydroimidazole (SiIm) were used to carry out the SN2 nucleophilic substitution for grafting the imidazolium groups onto the PECH. Meanwhile crosslinking of the modified PECH was achieved by forming a crosslinked silane network via the hydrolysis reaction of SiIm in an acid medium. Moreover, porous poly(tetrafluoroethylene) (PTFE) was used as the membrane matrix to enhance the mechanical strength of the fabricated membranes. The obtained PECH–SiIm–MeIm/PTFE membranes displayed phosphoric acid doping capacities of 110–170 wt% with low volume swelling ratios of less than 120%. Anhydrous proton conductivities of 0.010–0.063 S cm−1 were reached at elevated temperatures of 100–180 °C by the membranes with adequate mechanical strength. Fuel cell tests demonstrated the technical feasibility of acid doped PECH–SiIm–MeIm/PTFE membranes for high temperature proton exchange membrane fuel cells.

Quaternary imidazolium groups were grafted onto poly(aryl ether ketone) as both pendants and joints of crosslinking by using 1-methylimidazole and C2-substituted imidazole of 2-undecylimidazole in a certain mole ratio. Crosslinking of the imidazolium-functionalized poly(aryl ether ketone) was performed with three dibromoalkane crosslinkers having different alkyl chain-length in order to know the correlation of the structure and property of the crosslinked membranes meanwhile to enhance their mechanical strength. The obtained crosslinked membranes in hydroxide form showed a high tensile strength of about 20 MPa at room temperature with less swelling, and they were thermally stable up to around 230 °C according to the data of thermogravimetric analysis. All the crosslinked anion exchange membranes exhibited conductivities in purified water of higher than 0.010 S cm−1 at 25 °C, and over 0.040 S cm−1 at 80 °C, respectively. The durability of the membranes in alkaline medium was tested by monitoring the changes in conductivity, ion exchange capacity (IEC) and tensile strength at break, respectively. The results indicate that the anion exchange membrane crosslinked with a long alkyl spacer demonstrated high tolerance to the nucleophilic attack. In addition, the increase in the temperature could accelerate the degradation of the polymer membrane more than that increase in the concentration of the alkaline solution.

Long-term stability is desired for developing high temperature proton conducting membranes as electrolytes for clean energy conversion of fuel cells. To understand the correlation of the grafted imidazolium structure and the stability of the polymer, six kinds of imidazolium polysulfones were synthesized from various imidazole compounds and the chloromethylated polysulfone, as proved by 1H NMR and FT-IR spectra. Membranes with electron-withdrawing or long hydrophobic alkyl groups in the imidazolium pendants exhibited higher chemical stability than those with electron-donating short alkyl groups. After doping with phosphoric acid, the imidazolium polysulfone membranes showed acid doping levels of 8.2–13.0. The membrane with a long tail side-chain of decyl in the imidazolium pendant achieved the highest conductivity of 0.038 S cm−1 at 160 °C without humidifying. Based on this membrane, fuel cell tests demonstrated the technical feasibility as the high temperature proton exchange membrane electrolyte in fuel cells.

A novel type of high temperature proton exchange membrane (PEM) modified by hyperbranched polyamidoamine (HP) and reinforced by polytetrafluoroethylene (PTFE) was prepared by a facile route. Polymers of polyvinylchloride (PVC) and polyvinylpyrrolidone (PVP) were first blended with a mole ratio of 1.2 : 1. The blended polymers were then crosslinked by HP via the SN2 nucleophilic substitution reaction with mass ratios of HP to PVC up to 1 : 1. The alkaline amine-rich HP has high affinities with phosphoric acid (PA) molecules, which could bring on superior proton conductivity while sacrifice mechanical strength of the membranes. Hence the porous PTFE which could reduce the plasticizing effect of PA was introduced to balance the proton conductivity and the mechanical strength of the composite membranes. As a result, PA doped PTFE reinforce composite membrane which doped with 29 wt% HP exhibited a high proton conductivity of 0.154 S cm−1 at 160 °C without humidifying and an excellent tensile stress at break of 22 MPa under ambient atmosphere, which is much better than the PA doped pristine PVP-PVC composite membrane. A single H2/O2 fuel-cell demonstrated that a peak power density of 433 mW cm−2 was achieved at 180 °C by using PA doped PTFE reinforce composite membrane which doped with 29 wt% HP as the electrolyte with no humidification.

A high-strength anion exchange membrane with a full interpenetrating network (full-IPN) structure was prepared from quaternized chitosan (QCS), polyacrylamide (PAM) and polystyrene (PS). The influences of the component content of the membrane and crosslinking degree of the QCS on the mechanical properties, anionic conductivity as well as methanol permeability of the membranes were investigated. The results indicated that the full-IPN structure as well as the presence of the hydrophobic PS could improve the mechanical properties and decrease the methanol permeability of the membrane. Corresponding to the increase in the content of PAM/PS (the molar ratio of PAM/PS was 1:1) from 0 wt.% to 40 wt.% in the full-IPN membrane, the tensile stress was increased from 30.1 MPa to 43.9 MPa, the methanol permeability was decreased from 6.64 × 10 − 6 cm 2 s − 1 to 6.54 × 10 − 7 cm 2 s − 1 , respectively. Anionic conductivities of 6.00 × 10 − 3 –1.26 × 10 − 2 S cm − 1 were achieved at 80 °C for the obtained membranes. To the membranes with a QCS content of 60 wt.%, the conductivity and tensile stress of about 90% were maintained after soaking the membranes in 1 mol L − 1 KOH for 120 h, and a 10 mol L − 1 KOH for 50 h at room temperature, respectively.

Covalently cross-linked hexafluoropropylidene polybenzimidazole (F 6 PBI) was prepared and used to fabricate high temperature proton exchange membranes with enhanced mechanical strength against thermoplastic distortion. Three different epoxides, i.e. bisphenol A diglycidyl ether (R 1 ), bisphenol A propoxylate diglycidyl ether (R 2 ) and poly(ethylene glycol) diglycidyl ether (R 3 ), were chosen as the cross-linkers to investigate the influence of their structures on the properties of the cross-linked F 6 PBI membranes. All the cross-linked F 6 PBI membranes displayed excellent stability towards the radical oxidation. Comparing with the pure F 6 PBI membrane, the cross-linked F 6 PBI membranes showed high acid doping level but less swelling after doping phosphoric acid at elevated temperatures. The mechanical strength at 130 °C was improved from 0.4 MPa for F 6 PBI membrane to a range of 0.8–2.0 MPa for the cross-linked F 6 PBI membranes with an acid doping level as high as around 14, especially for that crosslinking with the epoxide (R 3 ), which has a long linear structure of alkyl ether. The proton conductivity of the cross-linked membranes was increased accordingly due to the high acid doping levels. Fuel cell tests demonstrated the technical feasibility of the acid doped cross-linked F 6 PBI membranes for high temperature proton exchange membrane fuel cells.

Simultaneously improving the proton conductivity and mechanical properties of a polymer electrolyte, especially to phosphoric acid doped membranes, is a challenge for the preparation of membrane materials in application in proton exchange membrane fuel cells. We prepared a novel composite membrane by introducing triazole functionalized graphene oxide into the polybenzimidazole for use as a high temperature proton exchange membrane. Increases in both proton conductivity and tensile strength were achieved by the composite membrane compared with the pure PBI membrane after doping with phosphoric acid. The triazole modified graphene oxide could disperse well in the polar organic solvent, which resulted in easy fabrication of the homogeneous membranes. The proposed material is a demonstration for designing and preparing inorganic composite polymer electrolytes with superior properties.

High temperature operation of proton exchange membrane fuel cells under ambient pressure has been achieved by using phosphoric acid doped polybenzimidazole (PBI) membranes. To optimize the membrane and fuel cells, high performance polymers were synthesized of molecular weights from 30 to 94 kDa with good solubility in organic solvents. Membranes fabricated from the polymers were systematically characterized in terms of oxidative stability, acid doping and swelling, conductivity, mechanical strength and fuel cell performance and durability. With increased molecular weights the polymer membranes showed enhanced chemical stability towards radical attacks under the Fenton test, reduced volume swelling upon the acid doping and improved mechanical strength at acid doping levels of as high as about 11 mol H3PO4 per molar repeat polymer unit. The PBI-78kDa/10.8PA membrane, for example, exhibited tensile strength of 30.3 MPa at room temperature or 7.3 MPa at 130 °C and a proton conductivity of 0.14 S cm–1 at 160 °C. Fuel cell tests with H2 and air at 160 °C showed high open circuit voltage, power density and a low degradation rate of 1.5 μV h–1 at a constant load of 300 mA cm–2.

A polybenzimidazole variant polymer containing hydroxyl pyridine groups, termed as OHPyPBI, was synthesized from 3,3′-diaminobenzidine tetrahydrochloride and 4-hydroxy-2,6-pyridinedicarboxylic acid. The thermal-oxidative stability of the OHPyPBI polymer was as high as that of poly[2,2′-( m -phenylene)-5,5′-bibenzimidazole] ( m PBI) according to the TGA data. The hydroxyl pyridine groups in the OHPyPBI structure resulted in high proton conductivities of the phosphoric acid doped OHPyPBI membranes. This is because the hydroxyl pyridine groups not only increased the acid doping level of the membranes, but also benefited the proton conduction, which was proved by the results of acid conductivities of the membranes with comparable acid doping levels. At an acid doping level of 8.6, i.e. 8.6 mol acids per molar repeat unit of the polymer, the OHPyPBI membrane exhibited a proton conductivity of 0.102 S cm −1 at 180 °C without humidifying. In addition, an improved tensile modulus at elevated temperatures was observed for acid doped OHPyPBI membranes. Fuel cell tests demonstrated the technical feasibility of acid doped OHPyPBI membranes for high temperature proton exchange membrane fuel cells.

Phosphoric acid doped polybenzimidazole membranes have been explored as proton exchange membranes for high temperature polymer electrolyte membrane fuel cells. Long-term durability of the membrane is of critical concern and has been evaluated by accelerated degradation tests under Fenton conditions. In this study effects of phosphoric acid and ferrous ions were investigated by measurements of the weight loss, intrinsic viscosity and size exclusion chromatography (SEC) of the polymer membranes. Ferrous ions resulted in, as expected, catalytic formation of peroxide radicals and hence the accelerated polymer degradation in terms of weight loss and molecular weight decrease. The presence of phosphoric acid as an inevitable dopant of the membranes, on the other hand, significantly impeded the membrane degradation by means of metal ion complexing, decreased pH, and acid–base interactions with the amino groups of the polymer. Fuel cell durability tests with contaminations of ferrous ions did show considerable performance degradation, however, primarily due to the catalyst deterioration rather than the membrane degradation.

Covalently cross-linked polymer membranes were fabricated from poly(aryl sulfone benzimidazole) (SO(2)PBI) and poly(vinylbenzyl chloride) (PVBCl) as electrolytes for high-temperature proton-exchange-membrane fuel cells. The cross-linking imparted organo insolubility and chemical stability against radical attack to the otherwise flexible SO(2)PBI membranes. Steady phosphoric acid doping of the cross-linked membranes was achieved at elevated temperatures with little swelling. The acid-doped membranes exhibited increased mechanical strength compared to both pristine SO(2)PBI and poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (mPBI). The superior characteristics of the cross-linked SO(2)PBI membranes allowed higher acid doping levels and, therefore, higher proton conductivity. Fuel-cell tests with the cross-linked membranes demonstrated a high open circuit voltage and improved power performance and durability.

The pathogenesis of stress urinary incontinence (SUI) is unclear. Aquaporins (AQPs) are a family of transmembrane proteins that transport water and small solutes, including glycerol, across cell membranes. AQPs have been demonstrated to serve a role in skin hydration, cellular proliferation, migration, immunity, wound healing and vascular remodeling in multiple organs. Furthermore, studies have confirmed that abnormal synthesis and degradation of collagens in extracellular matrix (ECM) remodeling contributes to SUI, by altering normal tissue architecture and mechanical properties. The authors previously demonstrated that AQP2 expressed in the human endometrium varies during the menstrual cycle. However, it is unknown whether AQP2 serves a role in the pathogenesis of SUI in the urethral supporting tissue. In the present study, AQP2 location and expression was examined in the anterior vaginal wall, and investigated the association between AQP2 and collagen I/III in female SUI. Western blotting, immunohistochemistry and immunofluorescence were used to measure AQP2 expression levels, and to reveal the location of AQP2 in the anterior vaginal wall, as well as fibroblasts in SUI and non‑SUI. The association between AQP2 and collagen I/III was subsequently investigated by AQP2‑small interfering RNA knockdown and overexpression 2 in fibroblasts. AQP2 expression in the anterior vaginal wall was significantly increased in women without SUI compared with those with SUI (P

Recent progress in the synthesis of polybenzimidazole (PBI) derivatives is summarized for application as high temperature polymer electrolyte membrane in fuel cells. Various designs in the polymer structure are described aiming at improvement of the membrane performance. The ways to produce PBI derivatives containing different functional groups, segments, or blocks of other macromolecules are classified as main-chain modification, copolymerization, and side-chain grafting. The synthetic routes and associated characterization methods particularly with respect to the polymer structures are also addressed.

A novel acid–base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i.e. methyl (MePSU), ethyl (EtPSU) and butyl (BuPSU) imidazoliums, as revealed by 1H NMR spectra. The imidazolium polysulfone membranes are then doped with phosphoric acid and used as a proton exchange membrane electrolyte in fuel cells. An acid doping level of about 10–11 mol H3PO4 per mole of the imidazolium group is achieved in 85 wt% H3PO4 at room temperature. The membranes exhibit a proton conductivity of 0.015–0.022 S cm−1 at 130–150 °C under 15 mol% water vapor in air, and a tensile strength of 5–6 MPa at 130 °C under ambient humidity. Fuel cell tests show an open circuit voltage as high as 0.96 V and a peak power density of 175–204 mW cm−2 at 150 °C with unhumidified hydrogen and air under ambient pressure.