Aromatic Polybenzimidazoles on the Basis of 4,4′-Diphenylmethane Diisocyanate and Bis(arylene)hydroxamic Acids

Aromatic polybenzimidazoles are synthesized via cyclopolycondensation of bis(arylene)hydroxamic acids with 4,4′-diphenylmethane diisocyanate and the structure of polymers is confirmed by the data of elemental analysis, IR and PMR spectroscopy. The properties of the obtained polymers are comparable to the characteristics of aromatic polybenzimidazoles prepared via the conventional scheme on the basis of о-phenylenediamines and dicarboxylic acids.     

N-substitution of polybenzimidazoles: Synthesis and evaluation of physical properties

Series of N-substituted polybenzimidazoles (PBI) were synthesized using selective alkyl groups with varying bulk and flexibility, viz., methyl, n-butyl, methylene trimethylsilane and 4-tert-butylbenzyl. PBI-I based on 3,3′-diaminobenzidine (DAB) and isophthalic acid and PBI-BuI based on DAB and 5-tert-butyl isophthalic acid were chosen for N-substitution. Structural characterizations of substituted polymers by FT-IR and ¹H NMR revealed elimination of hydrogen bonding. Evaluation of their physical properties revealed that N-substitution rendered better solvent solubility in common organic solvents, more open polymer matrix, but reduced thermal properties in comparison to their respective parent PBI. 4-tert-butylbenzyl, methylene trimethylsilane or n-butyl group substituted polymers were soluble even in chlorinated solvents (CHCl₃ and TCE). Substantial variations in gas permeability of inert gases, He and Ar and attractive P_He/P_Ar selectivity, especially after methyl group substitution depicted potential of these materials for gas separation.     

Polyheteroarylenes based on 2,3,7,8-tetraaminodibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxin and aromatic polyfunctional carboxylic acids

Polynaphthoylene benzimidazole and polybenzimidazole were obtained via polycondensation of 2,3,7,8-tetraaminodibenzo-p-dioxin with aromatic di- and tetracarboxylic acids in polyphosphoric acid. From a solution of polynaphthoylene benzimidazole in methanesulfonic acid a heat-resistant fiber with high tensile strength was obtained. Aromatic polybenzimidazoles are promising materials for producing membranes of medium-temperature fuel cells.     

New benzimidazole-2-yl-substituted polybenzimidazoles: Synthesis, properties, and hydrodynamic characteristics

The synthesis of novel benzimidazole-2-yl-substited polybenzimidazoles and initial compounds has been described. The polymers are studied by FTIR spectroscopy, TGA, and TMA. The hydrodynamic properties of macromolecules are investigated by translational diffusion and viscometry in 96% H₂SO₄; the molecular characteristics of the polymers are determined. Positive temperature dependences for intrinsic viscosities of the polymers are obtained. The polymers under study possess high hydrolytic stability with respect to sulfuric acid solutions up to 150°C and high thermal stability in the bulk. The TGA data correlate with the chemical structure of the polymers. The new polybenzimidazoles may be used as materials for the production of medium-temperature proton-conducting membranes.     

Synthesis of polybenzimidazoles with sulfonic acid groups

2-Sulfoterephthalic acid (STA) and disulfoisophthalic acid (DSIA) were synthesized through the sulfonation and the oxidation of m- and p-xylene. The polycondensation reactions of STA and DSIA with aromatic tetraamines gave polybenzimidazoles which contained one or two sulfonic acid groups for each repeating unit. The polymer obtained was soluble in sulfuric acid, some organic solvents, and aqueous strong alkaline solution. The polymers were stable up to 400°C, but they gave polybenzimidazoles above 400°C by eliminating sulfonic acid groups, instead of ring closure.     

Synthesis and characterization of novel polybenzimidazoles containing 4-phenyl phthalazinone moiety

A novel series of homo- and copoly(phthalazinone benzimidazole)s were synthesized from various stoichiometric mixtures of 4-(4-(4-(4-carboxyphenoxy)phenyl)-1-oxophthalazin-2(1H)-yl)benzoic acid (CPPBC) and isophthalic acid (IPA) with 3,3′-diaminobenzidine (DAB) by solution polycondensation in polyphosphoric acid (PPA). The structures of the obtained polymers were characterized by FT-IR and ¹H NMR. The obtained polybenzimidazoles were found to be soluble in aprotic polar solvents such as N-methyl-2-pyrolidinone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO) and m-cresol, without the addition of inorganic salts. The inherent viscosities of the polybenzimidazoles were in the range of 1.10–2.05 dL/g. All of the polymers show amorphous nature as evaluated by WAXD. These polymers have high glass transition temperatures (T_gs) in the range of 398–408 °C. Thermogravimetric analysis exhibit that these polybenzimidazoles containing 4-phenyl phthalazinone moiety have excellent thermal stability with the temperatures for 5% and 10% weight loss of the polymers ranging from 516 to 594 °C and 560 to 672 °C, respectively.     

Synthesis and properties of new polybenzimidazoles and N-phenyl polybenzimidazoles with flexibilizing spacers on the polymer backbone

Several new polybenzimidazoles (PBIs) and N-phenyl PBIs were synthesized by high temperature solution polycondensation techniques. Three different tetramine hydrochlorides and one N-phenyl tetramine hydrochloride were condensed independently with p-phenylenedioxydiacetic acid (PDDA), 2,2′-[isopropylidene bis(p-phenyleneoxy)] diacetic acid (bisacid A₂) and 2,2′-[sulfonyl bis(p-phenyleneoxy)] diacetic acid (bisacid S) in polyphosphoric acid (PPA) at high temperatures. The polymers were obtained in 55–65% yield with inherent viscosities in the range 0.58–0.96 dL/g. Four model benzimidazoles (MBI) were also synthesized to confirm the formation of polybenzimidazoles. The PBIs and MBIs were characterized by infrared spectroscopy and elemental analysis. The properties of the polymers such as solubility, density, crystallinity, and thermal, thermoxidative, and isothermal stabilities were studied.     

Synthesis and characterization of thermally stable sulfonated polybenzimidazoles

A series of sulfonated polybenzimidazoles (sPBI-IS) with controlled sulfonation degrees (SDs) were synthesized from various stoichiometric ratio mixtures of 5-sulfoisophthalic acid monosodium salt (SIPN), 4,4′-sulfonyldibenzoic acid and 3,3′-diaminobenzidine by solution copolycondensation in poly(phosphoric acid). The resulting sulfonated polymers were characterized by means of FTIR, ¹H NMR and GPC, in addition to TGA and DMA. The number-average molecular weights (M_n) of the sPBI-IS are in the range of 45,500-64,000, and the polydispersity indices (M_w/M_n) vary from 1.9 to 2.4. The synthesized sPBI-IS samples present good solubilities in polar aprotic solvents and they are easy to form the transparent, flexible and tough films by solution casting. These polymer membranes show excellent thermal stabilities and dynamic mechanical properties. The thermal stability of the sodium form sPBI-IS remarkably increases with increasing SD. However, the acidic form sPBI-IS presents less thermal stability than the non-sulfonated sample (sPBI-IS0). The onset decomposition temperature (T_d) and the glass-transition temperature (T_g) of the acidic form sPBI-IS70 are 439 °C and 196 °C, respectively. The sulfonated membranes show higher storage moduli and loss moduli than sPBI-IS0. The resulting sPBI-IS membranes with high hygroscopicity show potential application as the high temperature proton exchange membrane in fuel cell.     

Syntheses and characterization of poly(benzimidazolyl) thiaxanthones

Novel polybenzimidazoles containing thiaxanthone heterocyclic units were synthesised from 2,7-thiaxanthonedicarboxylic acid-5,5′-dioxide and 2,8-thiaxanthonedicarboxylic acid-5,5′-dioxide and two aromatic tetramine hydrochlorides by PPA solution polycondensation in 60–70% yield. Two model compounds, 2,7-bis(2-benzimidazolyl)thiaxanthone-5,5′-dioxide and 2,8-bis(2-benzimidazolyl)thiaxanthone-5,5′-dioxide, were prepared and characterized by spectral methods. The polybenzimidazoles have inherent viscosities in the range 1.13–1.50 dL/g and decomposition temperatures of 495–560°C. The effect of thiaxanthone units on polymer properties are discussed.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.     

耐高温含氟磺化聚苯并咪唑的合成及表征

采用5-磺酸钠间苯二甲酸、双(苯甲酸)六氟丙烷与3,3',4,4'-四氨基联苯在多聚磷酸中通过共缩聚反应, 合成了一系列磺化度(定义为100个重复单元中所含的磺酸基个数, SD)可控的含氟磺化聚苯并咪唑(sPBI), 并利用红外光谱、核磁共振、凝胶色谱和热失重分析等手段对其结构、分子量与热稳定性进行了表征, 还考察了其溶解性和成膜性. 结果表明, sPBI的数均分子量(M_n)为61300～86000, 多分散指数介于1.96～2.34之间, 并且sPBI具有良好的成膜性和优异的热稳定性能, 其5%和10%热失重对应温度均随着SD的增加而有所提高, 在SD为70%时分别为549和576 ℃. 此类聚合物在质子交换膜材料方面具有一定的应用前景.     

Synthesis and investigation of polybenzimidazoles containing alkyl substituents in aromatic nuclei

Polybenzimidazoles have been synthesized from 3,3′-diamino-5,5′-dimethylbenzidine, 3,3′,4,4′-tetraamino-5,5′-dimethyldiphenylmethane, bis(3-amino-4-methylamino)phenylmethane, bis(3-amino-4-methylamino-5-methyl)phenylmethane, and diphenyl esters of adipic, sebacic, isophthalic, and terephthalic acids and 4,4′-dicarboxydiphenyl oxide by solid-phase polyheterocyclization. Properties of the polybenzimidazoles have been studied. The polymers have high thermal stability. They are soluble in a number of organic solvents and give strong, elastic films. Solubility and thermal stability of polybenzimidazoles is determined by the methyl group position in the polymeric chain. The influence of other alkyl substituents on properties of polybenzimidazoles have been investigated. The polymer structure has been studied by infrared and PMR spectroscopy and elemental analysis.     

Thermodynamic and adsorption properties of semiinterpenetrating polymer networks based on polybenzimidazoles and polyaminoimide resin

Thermodynamic characteristics of adsorption of organic compounds on semiinterpenetrating networks based on polybenzimidazoles and polyaminoimide resin with different compositions were studied at small coverages using inverse gas chromatography. The following characteristics were determined: adsorption equilibrium constants (specific retention volumes) of substances of different classes (n-alkanes, aromatic hydrocarbons, ethers, ketones, alcohols, and nitrogen- and halogen-containing compounds), appropriate changes in differential molar internal energy and Helmholtz potential, and changes in standard molar entropy of the sorbates. The contributions of the molecular fragments to the heat of adsorption were calculated. The adsorption properties of the semiinterpenetrating networks based on polybenzimidazoles and polyaminoimide resin differ from those of the starting polymeric materials and their physical mixtures with the similar composition. Unlike graphitized thermal carbon black (nonspecific adsorbent), the network and starting materials manifest the specific properties (electron-donating and electron-accepting). The difference in the thermodynamic characteristics of adsorption on the semiinterpenetrating polymeric networks with different compositions is determined by the size and geometry of interphase regions.     

Siloxane-modified heterocyclic polymers

Fully aromatic, siloxane-modified polybenzimidazoles and polybenzoxazoles were prepared by a single-stage melt polymerization and characterized. These polymers, which have good solubility in pyridine and N-methylpyrrolidinone, undergo thermooxidative decomposition above 300°C. Model compounds for these two classes as well as polypyromellitimides were also prepared.     

Superstructure of hollandite KxMg(8+x)/3Sb(16−x)/3O16 (x≈1.76)

Single crystals of K_xMg_(8+x)/3Sb_(16−x)/3O₁₆ (x≈1.76) with a hollandite superstructure were grown. Ordering schemes for guest ions (K) and the host structure were confirmed by the structure refinement using X-ray diffraction intensities. The space group is I4/m and cell parameters are a=10.3256(6), c=9.2526(17)Å with Z=3. Superlattice formation is primarily attributed to the Mg/Sb occupational modulation in the host structure. Mg/Sb ratios at two nonequivalent metal sites are 0.8977/0.1023 and 0.1612/0.8388. Two types of the cavity are seen in the tunnel, where parts of K ions deviate from the cavity center along the tunnel direction. Probability densities for K ions in the two cavities are different from each other, which seems to have arisen from the Mg/Sb modulation.     

Synthesis and crystal structure of Bi6.4Pb0.6P2O15.2: A new polymorph in the series Bi6+xM1−xP2O15+y

Bi_6.4Pb_0.6P₂O_15.2 is a polymorph of structures with the general stoichiometry Bi_6+xM_1−xP₂O_15+y. However, unlike previously published structures that consist of layers formed by edge sharing OBi₄ tetrahedra bridged by PO₄ and TO₆ (T=transition metal) tetrahedra and octahedra the title compound's structure is more complex. It is monoclinic, C2, a=19.4698(4) Å, b=11.3692(3) Å, c=16.3809(5) Å, β=101.167(1)°, Z=10. Single-crystal X-ray diffraction data were refined by least squares on F² converging to R₁=0.0387, wR₂=0.0836 for 7023 intensities. The crystal twins by mirror reflection across (001) as the twin plane and twin component 1 equals 0.74(1). Oxygen ions are in tetrahedral coordination to four metal ions and the O(BiPb)₄ units share corners to form layers that are part of the three-dimensional framework. Eight oxygen ions form a cube around the two crystallographically independent Pb ions. Pb-O bond lengths vary from 2.265(14) to 2.869(14) Å. Pairs of such cubes share an edge to form a Pb₃O₂₀ unit. The two oxygen ions from the unshared edges are part of irregular Bi polyhedra. Other oxygen ions of Bi polyhedra are part only of O(BiPb)₄ units, and some oxygen ions of the polyhedra are also part of PO₄ tetrahedra. One, two, three and or four PO₄ moieties are connected to the Bi polyhedra. Bi-O bond lengths ?3.1 Å vary from 2.090(12) to 3.07(3) Å. The articulations of Pb cubes, Bi polyhedra and PO₄ tetrahedra link into the three-dimensional structure.     

Über das System BaFe1−xRuxO3−y

In the system BaFe_1?xRu_xO_3?y three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0-0.75) with hexagonal BaTiO₃ structure (6H; sequence (hcc)₂), a Ru-rich phase (x = 0.9) of hexagonal 4H type (sequence (hc)₂), and the pure Ru compound BaRuO₃ with rhombohedral 9R structure (sequence (hhc)₃). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich oxygen-deficient compounds) to good, metal-like conduction (Ru-rich compounds with complete oxygen lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors.     

Structural studies of carbene complexes: The crystal structure of the secondary carbene complex RuI2[CHN(CH3)(p-CH3C6H4)](CO)(CN-p-CH3C6H4)(P(C6H5)3)

Crystal and molecular structures of the title compound have been determined from a three-dimensional X-ray analysis using diffractometer data. The crystals are triclinic, space group P$\text{1}$, with Z = 2 in a unit cell of dimensions a = 11.640(1), b = 10.9139(8), c = 16.587(2) Å, α = 87.983(5), β = 99.670(6), λ = 62.250(5)°. Full matrix least squares refinement has given a final R-factor of 0.043 for 2726 reflections for which I > 2σ(I).The crystal structure consists of discrete molecules of neutral complex together with water molecules which are hydrogen bonded into pairs [O ? O separation 2.60 Å]. 0The (H₂0)₂ units do not hydrogen bond to any other atoms. The ruthenium coordination is octahedral with trans carbene and isocyanide, cis iodides, and cis phosphine and carbonyl ligands. The Ru-donor distances are 2.776(2) [I trans to -PPh₃], 2.782(1) [I trans to -CO], 2.342(4) [PPh₃], 1.855(15) [CO], 2.046(15) [C(carbene)], and 1.998(16) Å [C(isocyanide)]. The bond lengths are discussed in terms of the trans effects of the ligands. The C(carbene)-N distance is 1.26(2) Å and the Ru—C(carbene)—N angle is 141.5(5)°.     

Tl1−xNaxNb2PO8 and Related Compounds, Isostructural with Ca0.5+xCs2Nb6P3O24

Compounds A_2/3A′_1/3M₂XO₈ (A=Tl, Rb, Cs; A′=Na, Ag; M=Nb, Ta; X=P, As) have been synthesized using the ceramic method. The sodium and potassium compounds (A= Na and K) have been prepared by an ion exchange reaction starting from their thallium analogues. These materials are isotypic with Tl_1−xNa_xNb₂PO₈ (x=0.21) the structure of which has been determined by using X-ray single-crystal data. The space group is R32, the cell constants are a_H=13.369(2), c_H=10.324(3) Å and z=9. This compound is isostructural with Ca_0.5+xCs₂ Nb₆P₃O₂₄. Its three-dimensional framework [Nb₂PO₈]_n, built up from NbO₆ octahedra and corner-sharing PO₄ tetrahedra, delimits tunnels running along c_H and cavities accommodating Tl⁺ and Na⁺ cations, respectively. The K_2/3Na_1/3Nb₂PO₈ structure, refined using X-ray powder data, showed that K⁺ cations are spread like the Tl+ ones over many sites, but more excentred from the tunnel axis. The isotypy of these compounds is also revealed by the similarity of the infrared and Raman spectra. The nonlinear optical study showed a behavior similar to that of the KDP for all the compounds. The ionic conductivity measurements gave high activation energies and low conductivity values for these materials.     

Pb2.85Ba2.15Fe4SnO13: A new member of the AnBnO3n−2 anion-deficient perovskite-based homologous series

Pb_2.85Ba_2.15Fe₄SnO₁₃, a new n=5 member of the anion-deficient perovskite based A_nB_nO_3n−2 (A=Pb, Ba, B=Fe, Sn) homologous series, was synthesized by the solid state method. The crystal structure of Pb_2.85Ba_2.15Fe₄SnO₁₃ was investigated using a combination of neutron powder diffraction, electron diffraction, high angle annular dark field scanning transmission electron microscopy and Mössbauer spectroscopy. It crystallizes in the Ammm space group with unit cell parameters a=5.7990(1) Å, b=4.04293(7) Å and c=26.9561(5) Å. The Pb_2.85Ba_2.15Fe₄SnO₁₃ structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110](1?01)_p crystallographic shear (CS) planes. The corner-sharing FeO₆ octahedra at the CS planes are transformed into edge-sharing FeO₅ distorted tetragonal pyramids. The octahedral positions in the perovskite blocks between the CS planes are jointly taken up by Fe and Sn, with a preference of Sn towards the position at the center of the perovskite block. The chains of FeO₅ pyramids and (Fe,Sn)O₆ octahedra of the perovskite blocks delimit six-sided tunnels at the CS planes occupied by double chains of Pb atoms. The compound is antiferromagnetically ordered below T_N=368±15 K.