Hybird Membrane with High Proton Conductivity and Selectivity Based on SPEEK for Direct Methanol Fuel Cells

Composite membranes based on sulfonated silica/sulfonated poly(ether ether ketone)(SPEEK) were prepared by means of sol-gel method so as to gain a high conductivity and reasonable methanol permeability.The sulfonated silica is generated in situ via the hydrolysis of sulfonated 3-anminopropyl triethoxysilane(KH550) synthesized newly from 3-aminopropyl triethoxysilane and 1,4-butane sultone.The membrane with a silica mass fraction of 5% exhibits a conductivity of 0.187 S/cm at 80 °C and a methanol coefficient with 9.72×10-7 cm2/s.The composite membranes show improved condutive ability and better selectivity that can be promisingly used in direct methanol fuel cell.     

Sulfonated polyimides containing 1,2,4-triazole groups for proton exchange membranes

A series of sulfonated polyimide copolymers as novel proton exchange materials were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride(NTDA), sulfonated diamine based on pyridine group and diamine containing N-phenyl-1,2,4-triazole moiety. Flexible, transparent and tough membranes with high thermal stability and good mechanical properties were obtained. They exhibited good stability in boiling water and Fenton's reagent at 80 °C. More interestingly, a nonlinear relationship between proton conductivities of the resulting membranes and the degree of sulfonation(DS) was observed. The membrane with 50% DS exhibited the maximum proton conductivity, which was due to the combinational contributions of sulfonic acid and N-pheny-1,2,4-triazole groups. Thus, the N-phenyl-1,2,4-triazole moiety in this study not only can depress water absorption but also increase proton conductivity, especially at low DS.     

Synthesis and Characterization of Sulfonated Polyphosphazene-graft-Polystyrene Copolymersfor Proton Exchange Membranes简

A novel series of polyphosphazene-grafl-polystyrene （PP-g-PS） copolymers were successfully prepared by atom transfer radical polymerization （ATRP） of styrene monomers and brominated poly（bis（4-methylphenoxy）phosphazene） macroinitiator. The graft density and the graft length could be regulated by changing the bromination degree of the macroinitiator and the ATRP reaction time, respectively. The PP-g-PS copolymers readily underwent a regioselective sulfonation reaction, which occurred preferentially at the polystyrene sites, producing the sulfonated PP-g-PS copolymers with a range of ion exchange capacities. The resulting sulfonated PP-g-PS membranes prepared by solution casting showed high water uptake, low water swelling and considerable proton conductivity. They also exhibited good oxidative stability and high resistance to methanol crossover. Morphological studies of the membranes by transmission electron microscopy showed clear nanophase-separated structures resulted from hydrophobic polyphosphazene backbone and hydrophilic polystyrene sulfonic acid segments, indicating the formation of proton transferring tunnels. Therefore, these sulfonated copolymers may be candidate materials for proton exchange membranes in direct methanol fuel cell （DMFC） applications.     

A facile method for preparation of cardo poly(aryl ether sulfone) bearing pendent sulfoalkyl groups as proton exchange membranes

A series of cardo poly(aryl ether sulfone) copolymers bearing pendent sulfonic acid groups(SPES-X) have been prepared by a facile chemical graft method. The structure was confirmed by 1H-NMR spectra. The side-chain-type SPES-X membranes show significantly reduced swelling behavior and excellent mechanical properties as well as appropriate proton conductivity compared to the main-chain-type sulfonated polymers with similar ion exchange capacity(IEC) value. Moreover, they show methanol permeability in the range of 0.6 × 10-7-5.7 × 10-7 cm2/s which is lower than that of Nafion 117. All the results indicate that the SPES-X membranes are promising candidates for the direct methanol fuel cells.     

SYNTHESIS AND PROPERTIES OF SULFONATED POLY(ETHER KETONE)S CONTAINING 3,5-DIMETHYL PHTHALAZINONE MOIETIES AS PROTON EXCHANGE MEMBRANE MATERIALS

Sulfonated poly（ether ketone）s containing 3,5-dimethyl phthalazinone moieties（SPPEK-DMs）with different degrees of sulfonation（DS）were synthesized via direct polycondensation from 4-（3,5-dimethyl-4-hydroxyphenyl）-2,3- phthalazinone,4,4’-difluorobenzophenone and 3,3’-disulfonate-4,4’-difluorobenzophenone.The chemical structure of SPPEK-DMs was characterized by FTIR and ¹H-NMR.Thermal stability of SPPEK-DMs was characterized by the thermogravimetric analysis.The membranes prepared from SPPEK-DMs exhibited ion exchange capacities（IEC）ranging from 0.93 mmol·g^-1to 1.86 mmol·g^-1.Water uptake,swelling,oxidative stability and methanol permeability of SPPEKDMs membranes were investigated.SPPEK-DMs membranes exhibited high oxidative stability.The methanol permeability values of SPPEK-DMs membranes were in the ranee 5.15×10^-8-6.61×10^-7cm s,which was much lower than those of Nafionl 17.The proton conductivity of SPPEK-DM40 membranes was 1.1×10^-2Scm^-1at 70℃.     

Synthesis and characterization of a novel polymer electrolyte based on acrylonitrile/N-[4-(aminosulfonyl)phenyl]acrylamide copolymers

<正>Acrylonitrile/N-[4-(aminosulfonyl)phenyl]acrylamide(AN/ASPAA) copolymers were synthesized and used as a host of lithium ion conducting electrolytes.The composition,molecular weight and molecular weight distribution of AN/ASPAA copolymers were determined,and the influence of copolymer composition on the glass temperature of AN/ASPAA copolymers and the ion conductivity of electrolytes were investigated.The molecular weights of AN/ASPAA copolymers were lower than those of AN and ASPAA homopolymers due to the cross-termination reaction.The glass temperatures of AN/ASPAA copolymers increased as the molar fraction of ASPAA units in copolymers increased.The lithium ion conductivities of the polymer electrolytes increased initially as the molar fraction of ASPAA units in copolymers increased,and a maximum conductivity was achieved when the molar fraction of ASPAA in the copolymer was 16.8%.     

Preparation and evaluation of crosslinked sulfonated polyphosphazene with poly(aryloxy cyclotriphosphazene) for proton exchange membrane

Several crosslinked proton exchange membranes with high proton conductivities and low methanol permeability coefficients were prepared, based on the sulfonated poly[(4-fluorophenoxy)(phenoxy)] phosphazene(SPFPP) and newly synthesized water soluble sulfonated poly(cyclophosphazene)(SPCP) containing clustered flexible pendant sulfonic acids. The structure of SPCP was characterized by fourier transform infrared spectroscopy(FTIR) and ~1H NMR spectra. The membranes showed moderate proton conductivities and much lower methanol permeability coefficients when compared to Nafion 117. Transmission electron microscopy(TEM) results indicated the well-defined phase separation between the locally and densely sulfonated units and hydrophobic units, which induced efficient proton conduction. In comparison with SPFPP membrane, the proton conductivities, oxidative stabilities and mechanical properties of crosslinked membranes remarkably were improved. The selectivity values of all the crosslinked membranes were also much higher than that of Nafion 117(0.74×10~5S· s/cm~3). These results suggested that the c SPFPP/SPCP membranes were promising candidate materials for proton exchange membrane in direct methanol fuel cells.     

SYNTHESIS AND CHARACTERIZATION OF ORGANSOLUBLE POLYIMIDE AND COPOLYIMIDES FROM ALICYCLIC DIANHYDRIDE

A kind of highly organsoluble polyimide and copolyimides were successfully synthesized from bicyclo（2.2.2）-oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride （BCDA）, the commercial diamine 4,4＇-methylenedianiline （MDA） and the designed diamine 4,4＇-methylenebis-（2-tert-butylaniline） （MBTBA）. The polyimide from BCDA and MBTBA is highly soluble in conventional low boiling point solvents （such as chloroform, tetrahydrofuran） at room temperature. But the solubility of the copolyimides in conventional solvents decreased with the molar ratio of MBTBA and MDA decreased. When the molar ratio of MBTBA and MDA was larger than 7/3, the copolyimides can be soluble in low boiling point solvents at room temperature to form a transparent, flexible, tough film by solution casting. When the molar ratio of MBTBA and MDA was between 7/3 and 1/9, they can only be soluble in hot dipolar aprotic solvents （such as DMF, NMP etc.） and form films too. The copolyimide was only soluble in m-cresol when the molar ratio of MBTBA and MDA was lower than 1/9. The number-average molecular weights of the soluble copolyimides were larger than 5.8 × 1064 g/mol by GPC and their polydispersity indices were higher than 1.4. Only one glass transition temperature of these copolyimides was detected around 400℃ by DMA. The copolyimides did not show appreciable decomposition up to 430℃ in N2.     

Novel organosoluble polyimide based on an asymmetric bis(ether amine): 3, 4′-Bis(4-aminophenoxy)-benzophenone

A new kind of asymmetrical ether diamine,3,4’-bis（4-aminophenoxy）benzophenone（BABP）,was synthesized from the nucleophilic substitution reaction of 4-chloronitrobenzene and 3,4’-dihydroxybenzophenone in the presence of potassium carbonate,followed by catalytic reduction with SnCl₂-6H₂O and concentrated hydrochloric acid.The prepared diamine was employed in the preparation of a novel polyimide containing asymmetrical diaryl ether segments via the polycondensation of it with BTDA by a two-step method.The resulting polyimide exhibits excellent solubility,film-forming capability and high thermal resistance.     

Immobilization and Properties of Lipase from Candida rugosa on Electrospun Nanofibrous Membranes with Biomimetic Phospholipid Moities

Reported here is a protocol to fabricate a biocatalyst with high enzyme loading and activity retention, from the conjugation of electrospun nanofibrous membrane having biomimetic phospholipid moiety and lipase. To improve the catalytic efficiency and activity of the immobilized enzyme, poly（acrylonitrile-co-2-methacryloyloxyethyl phosphorylcholine）s（PANCMPCs） were, respectively, electrospun into nanofibrous membranes with a mean diameter of 90 nm, as a support for enzyme immobilization. Lipase from Candida rugosa was immobilized on these nanofibrous membranes by adsorption. Properties of immobilized lipase on PANCMPC nanofibrous membranes were compared with those of the lipase immobilized on the polyacrylonitrile（PAN） nanofibrous and sheet membranes, respectively. Effective enzyme loading on the nanofibrous membranes was achieved up to 22.0 mg/g, which was over 10 times that on the sheet membrane. The activity retention of immobilized lipase increased from 56.4% to 76.8% with an increase in phospholipid moiety from 0 to 9.6%（molar fraction） in the nanofibrous membrane. Kinetic parameter Km was also determined for free and immobilized lipase. The Km value of the immobilized lipase on the nanofibrous membrane was obviously lower than that on the sheet membrane. The optimum pH was 7.7 for free lipase, but shifted to 8.3-8.5 for immobilized lipases. The optimum temperature was determined to be 35 ℃ for the free enzyme, but 42-44℃ for the immobilized ones, respectively. In addition, the thermal stability, reusability, and storage stability of the immobilized lipase were obviously improved compared to the free one.     

Sulfonated Polyetherimide and Its Membranes

Polyetherimide(PEI) was sulfonated by chlorosulfonic acid for the first time. The sulfonated products were characterized by FT-IR, DSC, ion exchange capacity and water sorption measurement. The hydrophilicity of PEI was improved by the sulfonation. The PEI was blended with the sodium salt from of sulfonated PEI(SPEI) to prepare microporous membranes. The morphologies of the membranes were studied with Scanning Electron Microscope (SEM).     

Determination of Critical Parameters of Carbon Dioxide ＋ Butyraldehyde System with Different Compositions

Supercritical carbon dioxide（SC-CO2 ） is considered in green chemistry as a substitute for conventional solvents in chemical reactions due to its environmentally benign character. Recently we have reported the homogeneous hydroformylation of propylene in supercritical carbon dioxide（ SC-CO2 ） , which is an example of this kind of application of carbon dioxide. The determination for the critical parameters of carbon dioxide ＋ butyraldehyde mixtures is necessary for this reaction design which is the focus of the present paper. The critical parameters of the binary systems were determined via the static visual method at a constant volume with the molar fraction of butyraldehyde ranging from 1.0% to 2. 2% and the pressure ranging from 5 to 10 MPa. The experimental results show that the critical pressure and temperature increased with increasing the molar fraction of butyraldehyde. The bubble（dew） temperatures and the bubble （dew） pressures for the binary systems were also determined experimentally. The p-T Figures at different compositions of the binary systems were described. In addition, the critical compressibility factors Zc of the binary systems at different concentrations of n-butyraldehyde were calculated. It was found that the critical compressibility factor values of the binary systems decreased with increasing the molar fraction of n-butyraldehyde in the experimental range.     

Preparation and Properties of Hybrid Silane-crosslinked Sulfonated Poly(aryl ether ketone)s as Proton Exchange Membranes

A series of novel organic-inorganic hybrid proton-conducting electrolyte membranes with silane-crosslinked sulfonated poly(aryl ether ketone)(SC-SPAEK) networks was prepared via a simple procedure that includes solution casting and acid treatment. The organosilicon pendants of the silane-grafted SPAEK, which were expected to serve as coupling and crosslinking agents, were found to play a key role in the homogenous dispersion of inorganic particles and improved the performance of hybrid membranes. The hybrid membranes exhibited enhanced proton conductivity, and SC-SPAEK/TiO2-4 showed an extremely high proton conductivity of 0.1472 S/cm at 100℃. The crosslinked hybrid membranes also demonstrated good chemical resistance, oxidative stability, and mechanical properties. The crosslinked hybrid membranes with excellent comprehensive performance may be a promising material for proton exchange membrane fuel cells.     

SYNTHESIS AND CHARACTERIZATION OF HYBRID PROTON CONDUCTING MEMBRANES OF POLY（VINYL ALCOHOL） AND PHOSPHOMOLYBDIC ACID

Hybrid proton conducting membranes of poly（vinyl alcohol） （PVA） and phosphomolybdic acid （PMA） were prepared by solution casting method. The effect of PMA doping and PVA crosslinking density on the membrane properties and proton conductivity were investigated. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of glutaraldehyde （GA） was characterized by IR spectroscopy. Proton conductivity of the membranes increases with an increase in concentration of the doped PMA and also with an increase in crosslinking density of the membranes. Proton conductivity results indicate that a significant amount of PMA was maintained in the membranes even after several hours of immersion in water. A maximum conductivity of 0.0101 S cm^-1 was obtained for the membrane with 33.3 wt% PMA and crosslinking density of 5.825 mol%. X-ray diffraction studies were carried out to investigate the influence of PMA doping and crosslinking density on the nature of the membranes. These properties make them very good candidates for polymer electrolyte membranes for direct methanol fuel cell application.     

A Novel Diamine, 4＇-Phenyiphenyi 4-（3＂, 5＂-Diaminobenzoyioxy）- benzoate and Longer Side-chain Polyimide

This is a part of our systematic research work on polyimides with mesogenic unit side chain. In this study, a new 4＇-phenylpbenyl 4-（3＂,5＂-diaminobenzoyloxy）benzoate and polyimide were synthesized, and characterized by FTIR, ^1H-NMR, inherent viscosity, mechanical properties, and solubility measurements. The diamine composed with mesogenic unit aryl ester groups and bipbenyl group with longer L/D ratio, was synthesized by two key steps. Firstly, the hydroxy group of 4-hydroxybenzoic acid was protected by acetoxy group for avoiding self- polymerization of 4-hydroxybenzoic acid, and then selectively hydrolyzed after esterification of carboxyl. Secondly, a selective catalysis hydrogenation was adopted to prevent the aryl ester from deoxidation. Based on this diamine, a novel polyimide was prepared by polycondensation of 4＇-phenylphenyl 4-（3＂, 5＂-diaminobenzoyloxy）benzoate and 4-aminophenyl ether（ODA） with 4, 4＇-oxydiphthalic anhydride（ODPA） in N-methyl-2-pyrrolidone （NMP）. The resulting polyimide with longer side chain showed better solubility and more regular structure. Its inherent viscosity is lower than that without side chains, but its modulus and strength not only maintained, even improved.     

Synthesis and characterization of novel sulfonated polyimide containing phthalazinone moieties as PEM for PEMFC

A novel sulfonated diamine monomer,1,2-dihydro-2-(3-sulfonic-4-aminophenyl)-4-[4-(4-aminophenoxy)-phenyl]phthalazin- 1-one(S-DHPZDA),was successfully synthesized by direct sulfonation of diamine 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4- aminophenoxy)-phenyl]-phthalazin-1-one(DHPZDA).A series of sulfonated polyimides(SPIs),which can be used as the material of the proton exchange membrane(PEM)for the proton exchange membrane fuel cell(PEMFC),were prepared from 1,4,5,8- naphthalenetetracarboxylic dianhydride(NTDA),S-DHPZDA,and nonsulfonated diamines DHPZDA.The structure of the monomer and polymers were characterized by FT-IR and~1H NMR.The solubility of the S-DHPZDA-based SPIs has been improved due to the induction of the phthalazione moiety.The SPIs membranes have high thermo-stability,predominant swelling resistance with high ion exchange capacity.     

Properties of Phosphoric Acid Doped Poly（benzimidazole/sulfone/siloxane/amide）/Sulfonated Polystyrene/Silica Nanoparticle-based Proton Exchange Membranes for Fuel Cells

New siloxane and sulfone containing poly(benzimidazole/sulfone/siloxane/amide)(PBSSA) has been prepared for the formation of hybrid membranes(PBSSA/PS-S/SiNPs) with sulfonated polystyrene(PS-S) and 0.1 wt%-2 wt% silica nanoparticles(SiNPs). Field emission scanning electron micrographs showed good dispersion of filler, formation of dense nanoporous honeycomb like structure and uniform ionic pathway in these hybrids. The porous membrane structure was responsible for the fine water retention capability and higher proton conductivity of the new hybrids. Increasing the amount of nanoparticles from 0.1 wt% to 2 wt% increased the tensile stress of acid doped PBSSA/PS-S/SiNPs nanocomposites from 65.7 MPa to 68.5 MPa. A relationship between nanofiller loading and thermal stability of the membranes was also experientially studied, as the glass transition temperature of phosphoric acid doped PBSSA/PS-S/SiNPs nanocomposites increased from 207 °C to 215 °C. The membranes also had higher ion exchange capacity(IEC) around 2.01 mmol/g to 3.01 mmol/g. The novel membranes with high IEC value achieved high proton conductivity of 1.10-2.34 S/cm in a wide range of humidity values at 80 °C which was higher than that of perfluorinated Nafion 117 membrane(1.1 × 10-1 S/cm) at 80 °C(94% RH). A H2/O2 fuel cell using the PBSSA/PS-S/SiNP 2(IEC 3.01 mmol/g) showed better performance than that of Nafion 117 at 40 °C and 30% RH.     

Studies on synthesis and property of novel acid-base proton exchange membranes

Sulfonated poly(phthalazinone)s (SPPENK, SPPESK and SPPBEK) were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide (PEI) as the basic compounds, casting from their N-methylpyrrolidone (NMP) solution directly onto clean glass plates at 60℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity (IEC).     

Measurement and Correlation of the Ionic Conductivity of Ionic Liauid-Molecular Solvent Solutions

The ionic conductivity of the solutions formed from 1-n-butyl-3-methylimidazolium tetrafluoroborate （[Bmim][BF4]） or 1-n-butyl-3-methylimidazolium hexafluorophosphate （[Bmim][PF6]） and different molecular solvents （MSs） were measured at 298.15 K. The molar conductivity of the ionic liquids （ILs） increased dramatically with increasing concentration of the MSs. It was found that the molar conductivity of the IL in the solutions studied in this work could be well correlated by the molar conductivity of the neat ILs and the dielectric constant and molar volume of the MSs.     

Preparation of polyimide/BaTiO3/Ag nanocomposite films via in situ technique and study of their dielectric behavior

Triphase polyimide nanocomposite films were fabricated using barium titanate （BaTiO3） with high dielectric constant and silver （Ag） with high conductivity as fillers. In situ method was utilized to obtain the homogeneous dispersion of nanoparticles. The in situ polymerization of polyimide precursor-poly（amic acid） was performed in the presence of BaTiO3 particles. Silver compound 1,1,1-trifluoro-2,4-pentadionato silver（I） was added into the BaTiO3 containing poly（amic acid） solution to achieve silver nanoparticles via in situ self metallization technique. The thermally induced reduction converted silver （I） to metallic silver with concomitant imidization of poly（amic acid） to polyimide. Both BaTiO3 and silver nanoparticles were uniformly dispersed in the polyimide substrate. The dependence of dielectric behavior on the BaTiO3 and Ag contents was studied. The incorporation of small amount of silver nanoparticles greatly increased dielectric constant of composite films.