High-molecular-weight poly(propylene carbonate) (PPC) [number-average molecular mass (Mn): 80 000–100 000] is readily alcoholized into PPC macrodiols in the presence of 1,2-propanediol (PDO), 1,4-butanediol (BDO), or 1,6-hexanediol (HDO). The high-molecular-weight PPC and small amount of diols, such as PDO, BDO, or HDO, were stirred at elevated temperatures to convert the extremely viscous high-molecular-weight polymer to low-molecular-weight macrodiols with gel permeation chromatography-measured Mn of about 3000 Da. The chopping reaction of the high-molecular-weight PPC was studied in detail, such as the influences of the catalyst residue, the kinds of alcoholysis agents, reaction temperature, and time. The reaction mechanism of alcoholysis is proposed according to the experimental results. The results indicate that the presence of a trace residue of zinc catalyst (Zn-G-III) in PPC, excess diol feeding, and higher temperature can accelerate the alcoholysis. Moreover, different diols can produce different PPC macrodiols with varying end-capping. Finally, polycarbonate ether urethane can be successfully synthesized using as-synthesized PPC macrodiols and poly(propylene glycol) (Mn ≈ 3000) as the soft segment and 4,4′-diphenylmethane diisocyanate or BDO as the hard segment. The full evaluation for the synthesized PPC macrodiols demonstrates their potential applications in the polyurethane industry.Topics: Mechanical properties; Polyesters; Polyoxyalkylenes; Solvolysis; Thermal properties;

•Nafion-[PDDA/ZrP]n with nacre-like nanostructures was fabricated by LbL method.•The lamellar structure and Donnan exclusion suppress vanadium ion permeability.•Nafion-[PDDA/ZrP]3 exhibits higher performance in VRFB than pristine Nafion.A novel self-assembled composite membrane, Nafion-[PDDA/ZrP]n with nacre-like nanostructures was successfully fabricated by a layer-by-layer (LbL) method and used as proton exchange membrane for vanadium redox flow battery applications. Poly(diallyldimethylammonium chloride) (PDDA) with positive charges and zirconium phosphate (ZrP) nanosheets with negative charges can form ultra-thin nacre-like nanostructure on the surface of Nafion membrane via the ionic crosslinking of tightly folded macromolecules. The lamellar structure of ZrP nanosheets and Donnan exclusion effect of PDDA can greatly decrease the vanadium ion permeability and improve the selectivity of proton conductivity. The fabricated Nafion-[PDDA/ZrP]4 membrane shows two orders of magnitude lower vanadium ion permeability (1.05 × 10−6 cm2 min−1) and 12 times higher ion selectivity than those of pristine Nafion membrane at room temperature. Consequently, the performance of vanadium redox flow batteries (VRFBs) assembled with Nafion-[PDDA/ZrP]3 membrane achieved a highly coulombic efficiency (CE) and energy efficiency (EE) together with a very slow self-discharge rate. When comparing with pristine Nafion VRFB, the CE and EE values of Nafion-[PDDA/ZrP]3 VRFB are 10% and 7% higher at 30 mA cm−2, respectively.Download high-res image (237KB)Download full-size image

To eliminate capacity fading effects due to the loss of sulfur in cathode materials for lithium–sulfur batteries (LSBs), a polymer of poly(1,3-diethynylbenzene) (PAB) with good solubility was synthesized by an oxidative coupling reaction. This polymer can be instantaneously carbonized into highly conductive carbon, which can then be used as both an immobilizer host and conductivity enhancer for sulfur cathodes. The cathode material of S/PAB-C was prepared via a rapid dissolution–precipitation method combined with an in situ and instantaneous carbonization process to obtain 3D graphene-like PAB-C with an artificial honeycomb-like morphology. Benefitting from this particular design, the S/PAB-C cathode with an optimal content of 75% sulfur exhibits excellent discharge–charge performance, which shows initial discharge capacities of 1449 mA h g−1 at 0.1C and 1087 mA h g−1 at 0.5C, and retains a stable capacity of 900 mA h g−1 after 500 cycles with a high retention of 82.6% at 0.5C. The strategy which utilizes instantaneous carbonization of PAB and an in situ sulfur trapping process offers a new way to enhance the cycling stability and enriches the architectural design of LSBs. To the best of our knowledge, this is the first report about the brand new methodology to in situ synthesize highly conductive carbon for application in LSBs.

Biodegradable films of poly(propylene carbonate)/poly(vinyl alcohol)-thermoplastic polyurethane [PPC/(PVA-TPU)] ternary blends were successfully prepared by melting blending method. The mechanical properties of poly(propylene carbonate) blown film were greatly improved by blending PPC with PVA-TPU. In order to afford the melt processing of PVA, the PVA-TPU binary blend was firstly prepared using thermoplastic polyurethane as a polymeric plasticizer. The rheological behavior, mechanical properties and morphology of these blends were studied. Considering its melt viscosity and thermally processing temperature, the PVA-50%TPU, as a modifier, was blended with PPC to prepare PPC/(PVA-TPU) ternary blend. SEM observation revealed a basic one-phase morphological structure with very good interfacial adhesion between the extremely blurred PPC and PVA-TPU two components. Meanwhile, the miscibility of the ternary components was verified by only one glass-transition temperature obtained from DMA tests. The tensile strength and tear strength of PPC/(PVA-TPU) blown films were determined at different temperatures. The results demonstrate that the mechanical properties of PPC/(PVA-TPU) films were enhanced dramatically at low temperature when compared with neat PPC. At room temperature, PPC/30 %(PVA-50%TPU) blown film exhibited a tensile strength of 26 MPa, and an elongation at break of 484.0 %. Its tear strength in the take-up direction is 124.1 kN/m, and the one in machine direction is 141.9 kN/m. At a low temperature of 0 °C, PPC/30 %(PVA-50%TPU) exhibited a tensile strength of 40.7 MPa and tear strength of 107 kN/m, which are 153 % and 142 % of those of neat PPC respectively. The blending of PPC with the PVA plasticized with TPU provides a practical way to extend the application of the new biodegradable polymer of PPC in the area of blown films.

Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides (LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH (OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A series of poly(propylene carbonate) (PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient (OP) and water vapor permeability coefficient (WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.

Novel hierarchically porous carbon materials with very high surface areas, large pore volumes and high electron conductivities were prepared from silk cocoon by carbonization with KOH activation. The prepared novel porous carbon-encapsulated sulfur composites were fabricated by a simple melting process and used as cathodes for lithium sulfur batteries. Because of the large surface area and hierarchically porous structure of the carbon material, soluble polysulfide intermediates can be trapped within the cathode and the volume expansion can be alleviated effectively. Moreover, the electron transport properties of the carbon materials can provide an electron conductive network and promote the utilization rate of sulfur in cathode. The prepared carbon–sulfur composite exhibited a high specific capacity and excellent cycle stability. The results show a high initial discharge capacity of 1443 mAh g–1 and retain 804 mAh g–1 after 80 discharge/charge cycles at a rate of 0.5 C. A Coulombic efficiency retained up to 92% after 80 cycles. The prepared hierarchically porous carbon materials were proven to be an effective host matrix for sulfur encapsulation to improve the sulfur utilization rate and restrain the dissolution of polysulfides into lithium–sulfur battery electrolytes.Keywords: biopolymers; carbon−sulfur composites; cyclical stability; electron conductivity; hierarchically porous carbon materials; lithium−sulfur batteries

•Amphoteric ion exchange membrane synthesized by direct polymerization for VRBs.•Vanadium ion permeability was suppressed by introducing quaternary ammonium groups.•AIEM-20% has the highest selectivity and columbic efficiency of 88.1% at 50 mA/cm2.Novel sulfonated poly (fluorenyl ether ketone) with pendant quaternary ammonium groups (SPFEKA) was successfully synthesized by one-pot copolymerization of bis(4-fluoro-3-sulfophenyl)sulfone disodium salt, 4,4′-difluorobenzophenone, bisphenol fluorene and 2,2′-dimethylaminemethylene-9,9′-bis(4-hydroxyphenyl) fluorene (DABPF). The chemical structures were confirmed by FT-IR, and 1H NMR. The thermal properties were fully investigated by TGA. The synthesized copolymers SPFEKAs are soluble in aprotic solvents, and can be cast into membranes on a glass plate from their N,N′-dimethylacetamide (DMAc) solution. A new kind of amphoteric ion exchange membrane (AIEM) was obtained by immersed SPFEKA into 1 M sulfuric acid. The proton conductivities of these membranes are comparable to the most reported sulfonated polymers under the same conditions. The permeability of vanadium ions in vanadium redox flow battery (VRB) was effectively suppressed by introducing quaternary ammonium groups for Donnan exclusion effect. AIEM-20% possess a only 4.4% vanadium ion permeability of Nafion 115. Cell performance tests showed that the VRB assembled with AIEM-20% shows the highest coulombic efficiency (CE) at the current density of 50 mA/cm2, because of its lowest VO2+ permeability. In conclusion, these ionomers could be promising candidates for ion-exchange membranes for VRB applications.

•LbL/porous-SPFEK composite membrane was prepared by a facile approach.•The pore was produced by introducing imidazole followed by extraction removing.•The pores introduced into the membrane can make the proton conductivity increased.•The LbL bilayers can reduce vanadium ions diffusion of the composite membranes.•VRB-SPFEK-20.7imidazole-(PDDA/PSS)8 showed the highest CE of 92.5% at 30 mA cm−2.By the solution casting method, a novel porous membrane has been prepared for VRB by doping sulfonated poly(fluorenyl ether ketone) (SPFEK) with imidazole, and then imidazole was washed out by extraction with solution. The proton conductivity of porous membrane increased with increasing the content of imidazole, but proton/vanadium ion (H/V) selectivity decreased. Layer-by-layer (LbL) technique was used to improve the porous membrane with high selectivity. Moreover, the performance of VRB using SPFEK-20.7imidazole-(PDDA/PSS)8 membrane which is doped with 20.7 wt.% content of imidazole and then removed imidazole, and then deposited with eight LbL bilayers exhibits the highest columbic efficiency (CE) of 92.5% at 30 mA cm−2.

Sulfonated poly(fluorenyl ether ketone) (SPFEK) membranes have been first modified by layer-by-layer (LbL) self-assembly of positively charged polyelectrolyte PDDA (poly(diallyldimethylammonium chloride)) and negatively charged PSS (poly(sodium styrene sulfonate)). The membranes were investigated as an ion exchange membrane for vanadium redox flow batteries (VRBs). The permeability of the vanadium ions in VRBs was effectively suppressed by depositing the LbL thin film on the SPFEK membrane. The permeability decreased with increasing the number of PDDA/PSS bilayers. For the membrane with two self-assembly bilayers of PDDA/PSS, 50% and 10% of vanadium ion permeability of a pristine SPFEK and Nafion 117 membranes can be afforded, respectively. Moreover, the oxidative stability of the PDDA/PSS-SPFEK composite membrane is improved remarkably compared with the pristine one. Consequently, the performance of VRBs using the PDDA/PSS-SPFEK composite membrane exhibits the highest coulombic efficiency (CE) of 82.1% at 30 mA cm−2 and the longest duration stability in the self-discharge test.

A tris-cyclometalated iridium(III) complex [Ir(DMP)3] containing 2,6-dimethoxy phenol and an ancillary ligand was successfully prepared and used in the fabrication of organic light-emitting diodes (OLEDs). The absorption, emission, cyclic voltammetry and thermostability of the complex were systematically investigated. The structure of this complex was also characterized using single crystal X-ray diffraction analysis. Its crystal shows a cubic structure. Our device exhibits a yellow emission at 576 nm with a maximum luminescence efficiency of 10564 cd m−12 at a voltage of 7 V and a current density of 118 mA cm−2 respectively. The maximum quantum efficiency is 8.7% at 5.93 mA cm−2. The Commission Internationale de l′Eclairage (CIE) coordinates were (0.49, 0.50) at a 2 wt% doping concentration and show typical rectifying diode characteristics in the ITO/PEDOS:PSS/PVK:PBD:Ir(DMP)3/TPBI/Ba/Al device.

A composite proton exchange membrane containing electrospun nanofibers shows excellent oxidative stability and high proton conductivity as well as an extremely low activation energy of 1.30 kJ mol−1.

A novel Cu–Fe bimetal supported catalytic system was prepared and applied to the direct dimethyl carbonate (DMC) formation from methanol and CO2. The prepared catalysts were characterized by means of temperature-programmed reduction (TPR), X-ray powder diffraction (XRD), laser Raman spectra (LRS), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Metallic Cu, Fe and oxygen deficient Fe2O3−x (0 < x < 3) were formed during the reduction and activation step. The supported Cu–Fe bimetal catalysts exhibited good catalytic activity and high stability for the direct DMC formation. Under the reaction conditions at 120 °C and 1.2 MPa with space velocity of 360 h−1, the highest methanol conversion of 5.37% with DMC selectivity of 85.9% could be achieved. The high catalytic performance of the Cu–Fe bimetal catalysts in the DMC formation could be attributed to the interaction of base sites functioned by metallic Cu and Fe with acid sites provided by oxygen deficient Fe2O3−x (0 < x < 3) in the activation of methanol and CO2. The moderate concentration balance of acid and base sites was in favor of DMC formation.

A novel dihydroxyl monomer bearing 18 electron rich phenyl rings were synthesized and polymerized with other monomers bearing electron deficient phenyl rings to give dense and selective sites in macromolecules for post-sulfonation, which was successfully conducted in ClSO3H/CH2Cl2 solution at room temperature in a subsequential step. The chemical structures were confirmed by 1H NMR and FT-IR spectra. The ionic exchange capacity (IEC) was controlled to be from 0.65 to 1.21 mequiv g−1 to afford considerable proton conductivity. Distinct phase separation was observed in the resulting membranes from SAXS profiles. The SPAEK-5 with an IEC of 1.21 mequiv g−1 gave better proton conductivity than Nafion 117 at all tested temperatures under 100% relative humidity. The membranes exhibited an exceeding stability when immersing in Fenton's reagent (3 wt.% H2O2 + 2 ppm FeSO4) at 80 °C. These properties make them promising candidates for electrochemical applications.

A series of starch acetates (SAs) with different degrees of substitution (DS) were prepared by chemically converting the hydroxyl group of natural cornstarch (NS) into an acetyl group. Biodegradable poly (propylene carbonate) (PPC) was melt blended with these SAs in a Haake mixer. The morphologies, mechanical and thermal properties of PPC/SA and PPC/NS blends were investigated. PPC/SA (DS < 0.88) showed better tensile property and impact strength than those of PPC/NS. Scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR) revealed strong interfacial adhesion between the SA fillers and PPC matrix. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the addition of SA led to improved thermal stability of the blend. Among all the samples prepared, the PPC/SA (DS = 0.51) has the optimal mechanical and thermal properties. The methodology described here represents a promising approach for the production of cost competitive biodegradable polymer blends.Highlights• Starch acetate (SA) acts as reinforcement fillers for poly (propylene carbonate) (PPC). • Strong interfacial adhesion existed between SA and PPC. • Incremental enhancement in mechanical properties was dramatically obtained for PPC/SA (DS < 0.88) blend. • The introduction of SA led to the improvement in the thermal stability of PPC matrix.

High-molecular-weight bulky-block poly(fluorenyl ether thioether ketone)s were successfully synthesized by a two steps one-pot protocol using N,N′-dimethy-S-carbamate masked dithiols for vanadium redox flow battery (VRB) application. The followed sulfonation procedure gave birth to novel sulfonated block poly(fluorenyl ether thioether ketone)s (SPFETKs) with controlled ionic exchange capacities (IEC). Membranes with proton conductivities higher than (IEC > 1.66 mequiv. g−1) or comparable to (IEC < 1.66 mequiv. g−1) that of Nafion117 membrane were achieved. The VO2+ permeabilities of SPFETKs membranes were much lower than that of Nafion117 membrane. The thermal properties, mechanical properties, oxidative stability, water uptake, proton conductivity, VO2+ permeability and cell performance were investigated in detail.

High-molecular-weight poly(arylene thioether ketone) (PTK) and poly(arylene thioether ketone ketone) (PTKK) polymers were successfully synthesized by one-pot polymerization of N,N′-dimethy-S-carbamate masked dithiols with activated dihalo compounds, followed by post-sulfonation using chlorosulfonic acid as the sulfonation agent in dichloromethane solution to give the production of sulfonated poly(arylene thioether ketone) (SPTK) and sulfonated poly(arylene thioether ketone ketone) (SPTKK) with appropriate ion-exchange capacities. The chemical structures were confirmed by 1H NMR, FT-IR and elemental analysis (EA). The thermal properties were fully investigated by TGA-IR. The synthesized SPTK and SPTKK polymers are soluble in aprotic solvents such as N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide and dimethyl sulfoxide, and can be cast into membranes on a glass plate from their DMAc solution. The proton conductivities of these membranes are comparable to Nafion117 membranes under the same conditions. Cell performance tests showed that the vanadium redox flow batteries (VRBs) assembled with SPTK and SPTKK membranes possessed higher Coulombic efficiencies than VRBs assembled with Nafion117 membranes at the current density of 50 mA cm−2, because of their one-order-of magnitude lower VO2+ permeabilities. In conclusion, these ionomers could be promising candidates as proton-exchange membranes for vanadium redox flow battery (VRB) applications.

In order to develop novel membranes for vanadium redox flow battery (VRB) with low self-discharge rate and low cost, sulfonated poly(fluorenyl ether ketone) (SPFEK) was synthesized directly via aromatic nucleophilic polycondensation of bisphenol fluorene with 60% sulfonated difluorobenzophenone and 40% difluorobenzophenone. The SPFEK membrane shows the lower permeability of vanadium ions. The open circuit voltage evaluation demonstrates that the SPFEK membrane is superior to Nafion 117 membrane in self-discharge test. Both energy efficiencies (EE) and power densities of the VRB single cell based on the SPFEK membrane are higher than those of the VRB with Nafion 117 membrane at the same current densities. The highest coulombic efficiency (CE) of VRB with SPFEK membrane is 80.3% while the highest CE of the VRB with Nafion 117 membrane is 77.0%. The SPFEK membrane shows the comparative stability to Nafion 117 membrane in VO2+ electrolyte. The experimental results suggest that SPFEK membrane is a promising ion exchange membrane for VRB.

A series of novel organic–inorganic hybrid membranes with special microstructure, based on sulfonated poly (fluorenyl ether ketone) ionomer (SFPEK, IEC = 1.92 mequiv. g−1) and SiO2 or sulfonic acid group containing SiO2 (SiO2–SO3H), has been successfully designed and prepared for vanadium redox flow battery (VRB) application. The SiO2–SO3H is synthesized by co-condensation of tetraethoxysilane and γ-propyl mercaptotrimethoxysilane via sol–gel process to control the same IEC with neat SPFEK. The hybrid membranes are prepared by simply adding the inorganic particles into the SPFEK solution in N,N′-dimethylacetamide, followed by ultrasonic dispersion, casting and profiled temperature drying process. The morphology is examined by SEM-EDX which is applied to the top surface, bottom surface and cross-section of the hybrid membranes. The water uptake, oxidative stability, thermal property, mechanical property, proton conductivity, VO2+ permeability and single cell performance are investigated in detail in order to understand the relationship between morphology and property of the membranes. All the hybrid membranes show dramatically improved proton selectivity at 20 °C and 40 °C when compared with Nafion117. The VRB assembled with the SPFEK/3%SiO2 and SPFEK/9%SiO2 membranes exhibit higher coulombic efficiency and average discharge voltage than the VRB assembled with the SPFEK membrane at all the tested current densities.

A series of sulfonated block poly(ether ether ketone)s with different sulfonic acid group clusters were successfully synthesized by nucleophilic displacement condensation. Membranes were accordingly cast from their DMSO solutions, and fully characterized by determining the ion-exchange capacity, water uptake, proton conductivity, dimensional stabilities and mechanical properties. The experimental results showed that the main properties of the membrane can be tailored by changing the cluster size of sulfonic acid groups. The membrane of block-7c(40) has good mechanical, oxidative and dimensional stabilities together with high proton conductivity (5.09 × 10−2 S cm−1) at 80 °C under 100% relative humidity. The membranes also possess excellent thermal and dimensional stabilities. These polymers are potential and promising proton conducting membrane material for PEM full cell applications.A series of sulfonated block poly(ether ether ketone)s with different sulfonic acid group clusters were successfully synthesized and characterized.

A composite proton exchange membrane containing electrospun nanofibers shows excellent oxidative stability and high proton conductivity as well as an extremely low activation energy of 1.30 kJ mol−1.

A novel dihydroxyl monomer bearing 18 electron rich phenyl rings were synthesized and polymerized with other monomers bearing electron deficient phenyl rings to give dense and selective sites in macromolecules for post-sulfonation, which was successfully conducted in ClSO3H/CH2Cl2 solution at room temperature in a subsequential step. The chemical structures were confirmed by 1H NMR and FT-IR spectra. The ionic exchange capacity (IEC) was controlled to be from 0.65 to 1.21 mequiv g−1 to afford considerable proton conductivity. Distinct phase separation was observed in the resulting membranes from SAXS profiles. The SPAEK-5 with an IEC of 1.21 mequiv g−1 gave better proton conductivity than Nafion 117 at all tested temperatures under 100% relative humidity. The membranes exhibited an exceeding stability when immersing in Fenton's reagent (3 wt.% H2O2 + 2 ppm FeSO4) at 80 °C. These properties make them promising candidates for electrochemical applications.

To eliminate capacity fading effects due to the loss of sulfur in cathode materials for lithium–sulfur batteries (LSBs), a polymer of poly(1,3-diethynylbenzene) (PAB) with good solubility was synthesized by an oxidative coupling reaction. This polymer can be instantaneously carbonized into highly conductive carbon, which can then be used as both an immobilizer host and conductivity enhancer for sulfur cathodes. The cathode material of S/PAB-C was prepared via a rapid dissolution–precipitation method combined with an in situ and instantaneous carbonization process to obtain 3D graphene-like PAB-C with an artificial honeycomb-like morphology. Benefitting from this particular design, the S/PAB-C cathode with an optimal content of 75% sulfur exhibits excellent discharge–charge performance, which shows initial discharge capacities of 1449 mA h g−1 at 0.1C and 1087 mA h g−1 at 0.5C, and retains a stable capacity of 900 mA h g−1 after 500 cycles with a high retention of 82.6% at 0.5C. The strategy which utilizes instantaneous carbonization of PAB and an in situ sulfur trapping process offers a new way to enhance the cycling stability and enriches the architectural design of LSBs. To the best of our knowledge, this is the first report about the brand new methodology to in situ synthesize highly conductive carbon for application in LSBs.