Modification of PET by Reactive Blending with Sulfonated Esters. II. Isothermal Crystallization Kinetics of PET-Ionomers

The thermal properties of PET-ionomers, obtained by reactive blending between PET and a monofunctional ester containing an ionic group (–SO₃Na), were studied using DSC, and results were compared with those of nonionic PET homopolymers. The presence of ionic groups located only at the chain ends induces significant modifications in the thermal behavior: the equilibrium melting temperature increases and the crystallization rate decreases with the ionic group content; moreover, the crystalline level remains high. All of these characteristics are interpreted as due to ionic associations between the sulfonated end groups, both in solid and in molten states, that cause an apparent increment in the molecular weight of ionomers. A confirmation of this simple molecular architecture is found in the growth regime analysis: the fold-surface free-energy values of ionomers do not vary compared to those of nonionic homopolymers, indicating that chain folding is not hindered by the presence of a complex network.     

Synthesis and properties of side-chain-type ion exchange membrane PEEK-g-StSO3Na for bipolar membranes

Side-chain-type ion exchange membranes (PEEK-g-StSO₃Na) were prepared by grafting poly (ether ether ketone) (PEEK) containing propenyl groups with sodium sulfonic styrene (StSO₃Na) and KH570. PEEK was synthesized by the aromatic nucleophilic polycondensation reaction of 4,4′-difluorobenzophenone, bisphenol A and diallylbisphenol A. The synthesized copolymers with the -SO₃Na group on the side chain of polymers possessed high molecular weights. The cross-linking reaction was carried out through a sol-gel reaction of the trimethoxysilane group. The copolymer membranes exhibited excellent mechanical properties due to their aromatic structure extending through the backbone and flexible StSO₃Na aliphatic chains. The ion exchange capacities (IECs) of the membranes ranged from 2.27 to 2.50 mmol g⁻¹ and the water content ranged from 107.2 to 126.1%, with both parameters increasing with StSO₃Na grafting degree. The H⁺ permeability of copolymer membranes increased with increasing IEC, reaching value above 0.3056 mol/L at 2 h, which is higher than that of Nafion^® 117 at the same measurement condition. They displayed reasonably high H⁺ permeability due to the higher acidity of benzoyl sulfonic acid group, the larger interchain spacing, which is available for water occupation, and the lower AC impedance of the bipolar membrane.     

The effects of backbone conformation on hydration and proton transfer in the ‘short-side-chain’ perfluorosulfonic acid membrane

Presented here is a first principles based molecular modeling investigation of the effects of conformational changes in the backbone on hydration and proton transfer in the short-side-chain perfluorosulfonic acid fuel cell membrane under minimal hydration conditions. Extensive searches for minimum energy structures (at the B3LYP/6-311G^⁎⁎ level) of the two pendant side chain polymeric fragment: CF₃CF(–O(CF₂)₂SO₃H)–(CF₂)₇–CF(–O(CF₂)₂SO₃H)CF₃ with from 4 to 7 explicit water molecules revealed that the perfluorocarbon backbone may adopt both an elongated geometry with all carbons in a trans configuration and also a folded conformation as a result of the hydrogen bonding of the terminal sulfonic acids with the water. Our calculations show that the fragments displaying the latter ‘kinked’ backbone possessed stronger binding of the water to the sulfonic acid groups and also effect proton dissociation with fewer water molecules. These calculations point to the importance of the flexibility of the backbone in the transport of protons for membranes with low water content.     

Charge carrier mobility in sulphonated and non-sulphonated Ni phthalocyanines: experiment and quantum chemical calculations

The objective of this interdisciplinary paper was to study theoretically and experimentally the electronic part of charge carrier transport in the class of sodium salts of sulphonated Ni phthalocyanine as candidates for p-type channels in organic field-effect transistors. These materials were selected because of their enhanced solubility as compared to their non-sulphonated counterparts. The values of the field-effect charge carrier mobility determined on the OFET structures using NiPc(SO₃Na)_x films were much higher than the charge carrier mobility obtained on the respective device prepared from non-substituted phthalocyanine. In order to explain differences between charge carrier mobility of sulphonated and non-sulphonated Ni phthalocyanines, quantum chemistry studies of molecular aggregates were performed. Quantum chemistry modeling of the semiconductive molecular systems is new and progressive – we highlighted factors at the molecular level which led to the enhancement of the charge carrier mobility in systems containing SO₃Na groups.     

The SO2 Stretching Vibrations in Some Metal Saccharinates: Spectra-Structure Correlations

The infrared spectra of a series of metal saccharinates (those of Na, Mg, Mn Fe, Co; Ni, Zn, Cd, Pb as well as mercury(II) saccharinate and chloromercury(II) saccharinate) were studied in the region of the antisymmetric and symmetric SO₂ stretching vibrations [v_as(SO₂) and v_s(SO₂) hereafter]. The results concerning the number of bands attributable to the abovementioned vibrations, their frequencies and intensities were correlated with the crystallographically determined type of metal-to-ligand bonding, on the one hand, and the number of the structurally different SO₂ groups, on the other.

It was shown that, irrespective on whether the sulphonyl oxygen atoms do or do not participate in bonding to the metal atom and/or in hydrogen bonding and irrespective on the type of the metal-to-saccharin bond (from covalent to purely ionic), the frequencies of both v_as(SO₂) and v_s(SO₂) modes are lower for the metal saccharinates than for saccharin itself, the effect being more pronounced in the case of the v_as(SO₂) bands.

As expected, the appearance of the spectra in the SO₂ stretching regions is rather strongly dependent on the values of the O-S-O angles. Thus, two rather different types of O-S-O angles exist in the structure of the covalently bonded saccharinate of mercury and of the ionic lead saccharinate (the values of these angles are 118.7 and 111.8 ° and 120.4 and 111.8 ° respectively) and two pairs of v_as(SO₂) and v_s(SO₂) bands are present in the spectra of these two compounds. On the other hand, the existence of only one type of SO₂ groups in the saccharinates of Mn and ClHg or the presence of SO₂ groups with very close O-S-O angles in the saccharinates of Na and Mg is manifested by the appearance of only a single pair of intense v_as(SO₂) and v_s(SO₂) bands in their spectra.     

Immobilization of RuS2 Nanoparticles Prepared in Reverse Micellar System onto Thiol-Modified Polystyrene Particles and their Photocatalytic Properties

RuS₂ nanoparticles, smaller than 3 nm in diameter, were prepared by H₂S gas injection into the AOT/isooctane reverse micellar solution containing RuCl₃ aqueous solution. The nanoparticle size was found to be independent of the W_o (water content) value of the reverse micellar system, as shown by TEM observation. The recovery and immobilization of the RuS₂ nanoparticles from reverse micelles onto thiol-modified polystyrene particles (PSt-SH) were successfully carried out, by the addition of PSt-SH into the reverse micellar solution under conditions of mild stirring. The resulting composites, PSt-RuS₂, showed photocatalytic activity for H₂ generation form aqueous solution containing 2-propanol and Na₂SO₃ as sacrificial electron donors.     

Electronic structure and spectral and luminescent properties of anti-HIV-active aminophenols

The method of intermediate neglect of differential overlap (INDO) with spectroscopic parameterization is used to calculate the electronic structure and the electronically excited states of substituted o-aminophenols comprising the SO₂ group. It is demonstrated that incorporation of this group into the 2-anilino-4,6-di-tretbutylphenol molecule leads to separation of the π-systems of phenyl rings forming the molecule. The intramolecular hydrogen bonds of various types and the SO₂ group change the charge redistribution between separate fragments of molecules thereby decreasing the donor properties of the phenyl fragments and the acceptor properties of the hydroxyl and amino groups. The influence of the SO₂ group on the absorption and fluorescence spectra is insignificant and consists in a small long-wavelength shift of the absorption band spectrum and insignificant changes of the band intensities. Due to a higher degree of deviation of the molecules from the planar structure after incorporation of this group, the intersystem crossing increases; therefore, the quantum fluorescence yield of sulfosubstitutes is insignificant.     

硫酸(氢)根吸附层对Pd(111)电极上甲酸氧化反应的影响研究

本文使用循环伏安法和电势阶跃法分别研究了添加和不添加Na₂SO₄的0.1 mol/LH₂SO₄+0.1 mol/LHCOOH溶液中Pd(111)电极上甲酸氧化反应(FAO)的动力学行为,并与同样条件下0.1 mol/LHClO₄中的动力学行为进行比较. 加入0.05 mol/L或者0.1 mol/LNa₂O₄后,在相同的电位下负向扫描的FAO电流比正向扫描的显著减小. 本文推测在(SO₄^*_ad)_m+[(H₂O)_n-H₃O⁺]或(SO₄^*_ad)_m+[Na⁺(H₂O)_n-H₃O⁺]吸附层相转变电势以正的电位, 这个吸附层的结构可能随着电位的增加或Na₂SO₄的加入变得更加致密和稳定. 因此,破坏或者脱附致密的硫酸(氢)根吸附层变得更加困难,使得FAO 动力学在较高电位和随后的负扫电位受到明显的抑制.     

Comprehensive evolution mechanism of SOx formation during pyrite oxidation

Pyrite (FeS₂) oxidation during coal combustion is one of the main sources of harmful SO₂ emission from coal-fired power plants. Density functional theory (DFT) study was performed to uncover the evolution mechanism of SO_x formation during pyrite oxidation. The results show that chemisorption mechanism is responsible for O₂, SO₂ and SO₃ adsorption on FeS₂ surface. The presence of formed oxidation layer (Fe₂O₃) weakens the interaction between O₂ molecule and FeS₂ surface. The adsorbed O₂ molecule easily dissociates into active surface O atom for SO_x formation. The dissociation reaction of O₂ is activated by 77.38?kJ/mol, and exothermic by 138.46?kJ/mol. Compared to the further oxidation of SO₂ into SO₃, SO₂ prefers to desorb from FeS₂ surface. The dominant reaction pathway of SO₂ formation from the oxidation of the outermost FeS₂ surface layer is a three-step process: surface lattice S oxidation, SO₂ desorption and replenishment of S vacancy by activated surface O atom. The elementary reaction of surface lattice S oxidation has an activation energy barrier of 197.96?kJ/mol, and is identified as the rate-limiting step. SO₂ formation from the further oxidation of bulk FeS₂ layer is controlled by a four-step process: bulk lattice S migration, lattice S oxidation, SO₂ desorption and surface O atom deposition. Migration of lattice S from bulk position to the outermost surface shows a high activation energy barrier of 175.83?kJ/mol. The deposition process of surface O atom is a relatively easy step, and is activated by 21.05?kJ/mol.     

Effects of subsurface Na,H and C on the bonding of carbon to nickel surfaces

This paper reports the results of a theoretical study of Na, H and C subsurface atomic species in nickel and demonstrates how these interstitial atoms influence the reactivity of the Ni(111) surface and the structure of carbon species adsorbed on the surface. The benzene molecule, C₆H₆, in planar and nonplanar geometries, is used to probe bonding at the surface. Adsorption energies are calculated by ab initio configuration interaction techniques modelling the surface as an embedded cluster. Adsorption energies of planar C₆H₆ at the most stable, three-fold, adsorption site are 18 kcal/mol for the Ni(111) surface, and 10, 19 and 44 kcal/mol in the presence of the Na, H and C interstitials, respectively. The energies required for the planar to puckered distortion are 99 kcal/mol on Ni(111), 69 kcal/mol with the Na interstitial, 83 kcal/mol with H, and 134 kcal/mol with C compared to 198 kcal/mol for distortion of C₆H₆ in the gas phase. The possible relevance of these results to the nucleation of diamond on nickel are discussed. The results indicate that subsurface Na stabilizes tetrahedrally bonded carbon subunits of the diamond structure while subsurface C may make it easier for the overlayer to revert to a planar graphite structure.     

Synthesis of silver nanoparticle in imidazolium and pyrolidium based ionic liquid reverse micelles: A step forward in nanostructure inorganic material in room temperature ionic liquid field

Two silver salts, silver tetrafluoroborate and silver trifluoromethanesulfonate were dissolved in two different room temperature ionic liquids (RTILs), 1-Butyl-3 methyl imidazolium tetrafluoroborate ([Bmim][BF₄]) and 1-Butyl-1 methyl pyrrolidinium trifluoromethanesulfonate ([Bmpy][Tfms]). Triton x-100 (TX-100) surfactant and cyclohexane as nonpolar medium are used to dissolve these RTILs to create reverse micellar system. Pure reverse micellar system is characterized by dynamic light scattering (DLS) measurement. These pure RTIL reverse micellar systems are used to prepare stable silver nanoparticle solution without using any other auxiliary solvent in the whole process.     

A nuclear magnetic resonance study of the phase transitions and electric quadrupole Raman processes of M5H3(SO4)4·H2O (M=Na, K, Rb, and Cs) single crystals

The spin–lattice relaxation times and spin–spin relaxation times for ¹H and M in M₅H₃(SO₄)₄·H₂O (M=Na, K, Rb, and Cs) single crystals grown using the slow-evaporation method were measured as functions of temperature. Two kinds of protons were identified in the M₅H₃(SO₄)₄·H₂O structure: acid protons and water protons. Our experimental results show that the acid and water protons in Cs₅H₃(SO₄)₄·H₂O are involved in phase transitions of this crystal, whereas neither type of proton is involved in the phase transitions of the other three crystal type (M₅H₃(SO₄)₄·H₂O; M=Na, K, and Rb). Moreover, the relaxation times for the M (=Na, K, and Rb) nuclei in these crystals were found to decrease with increasing temperature and can be described with (k=2). The T₁ results for M (=Na, K, and Rb) in M₅H₃(SO₄)₄·H₂O crystals can be explained in terms of a relaxation mechanism in which the lattice vibrations are coupled to the nuclear electric quadrupole moments.     

Electrical conductivity of binary sulphates of lithium sulphate

To engineer lithium sulphate based material with high ionic conductivity at lowest possible temperature, the electrical conductivity of binary sulphates of Li₂SO₄ with Na₂SO₄, K₂SO₄, MgSO₄, ZnSO₄ and Ag₂SO₄ has been measured in the temperature range from 513 K to 773 K. The results are interpreted on the basis of different phases present therein. Li₂SO₄:Ag₂SO₄(40:60) mol % has high ionic conductivity = 2.17×10^-3(ohm cm)^-1 at 606 K which could be utilized in power sources.     

Superacid Catalyst SO42-/ZrO2-La2O3 Prepared by Ultrasonic Co-precipitation and Low Temperature Aging

低温陈化超声波共沉淀法制得SO₄^2-/ZrO^2-La₂O₃前驱体, 经H₂SO₄处理, 在不同温度下焙烧得到纳米晶催化剂SO₄^2-/ZrO^2-La₂O₃;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性.     

Functionalization of carbon encapsulated iron nanoparticles

Carbon-encapsulated magnetic nanoparticles are a new class of materials where the core magnetic nanoparticle is protected from reactions with its environment by graphite shells. Having a structure similar to carbon nanotubes, these nanoparticles could be potentially functionalized using methods which are already applied to those structures. We present the effects of acidic treatments based on HCl, HNO₃, and H₂SO₄ on these nanoparticles highlighting the impact on their magnetic and surface properties. We show that acidic treatments based on HNO₃ can be successfully applied for the generation of carboxylic groups on the surface of the nanoparticles. Using methylamine as a model, we demonstrate that these functional groups can be used for further functionalization with amino-containing biomolecules via diimide-activated amidation.     

Structure,phase composition,and spectral luminescence properties of partially stabilized zirconium dioxide crystals doped with Yb<Superscript>3+</Superscript> ions

Investigation of partially stabilized zirconium dioxide crystals via transmission electron microscopy has revealed a developed twin structure therein. The following compositions of the above crystals have been selected for this study: 97.2 mol % ZrO₂–1.0 mol % Y₂O₃–1.8 mol % Yb₂O₃; 97.2 mol % ZrO₂–2.0 mol % Y₂O₃–0.8 mol % Yb₂O₃; 97.2 mol % ZrO₂–2.5 mol % Y₂O₃–0.3 mol % Yb₂O₃; and 96.3 mol % ZrO₂–3.4 mol % Y₂O₃–0.3 mol % Yb₂O₃. X-ray diffraction analysis of these crystals indicate the presence of transformable (t) and nontransformable (t') tetragonal phases. Optical spectroscopy measurements of ZrO₂–Y₂O₃–Yb₂O₃ crystals with tetragonal and cubic structures have highlighted in Yb³⁺-doped zirconium dioxide samples the formation of the optical centers of the Yb³⁺ ions is observed, whose crystal surrounding is similar to those in cubic zirconium dioxide crystals.     

In-situ observation of oxygen adlayer formation on Cu(110) electrode surfaces

In-situ atomic force microscopy (AFM) was used to image Cu(110) single crystals in aqueous solutions during the initial stages of oxidation. Images obtained in pH 2.5–2.7 HClO₄ and H₂SO₄ solutions revealed the growth of oxygen adlayers consisting primarily of [001] oriented chains. A majority of these chains (ca. 70%) were arranged in (2 × 1) and (3 × 1) structures. These chain structures were observed in the thermodynamically forbidden region of the pH-potential phase diagram, which indicates that stable oxygen adlayers develop prior to bulk oxide formation.     

Dose quality determined using ESR imaging

The differences in SO⁻₃ radical distribution produced in gadolinium (Gd)-doped glaserite (K₃Na(SO₄)₂) rod after irradiation with β-, γ-, or X-rays was investigated by an electron spin resonance (ESR) imaging method. In β- or X-irradiated samples, the SO⁻₃ radical distribution showed a steep gradient in the rod. In γ-irradiated samples, the distribution showed only a slight gradient in the rod. From these results, ESR imaging can not only detect the radiation direction and the absorbed dose, but can also be expected to distinguish the dose quality.     

Rheological Behavior of Some Cationic Polyelectrolytes

The rheological behavior of some cationic polyelectrolytes in aqueous solution is presented. The polyelectrolytes under study consist of polycations that have positive charges (N,N-dimethyl-2-hydroxypropylenammonium chloride) located along the main chain with or without nonpolar side chains (PCA₅D₁ and PCA₅, respectively). This investigation mainly considers the influence of oscillation frequency and temperature on their rheological behavior in salt-free aqueous solution at three polymer concentrations (c_p = 2%, 4%, and 6%) as well as in the presence of low molar mass salt (NaCl). The results indicate the main effect of these parameters was to modify the hydrophobic interactions between the side nonpolar groups of the modified polyelectrolyte. The comparison between the complex viscosity values, at the same polymer concentration, c_p = 4%, for PCA₅D₁ and PCA₅ shows higher values in the whole interval of temperatures under study and a pseudoplastic behavior at temperatures greater than 50°C for the former system.     

Isomorphism among commensurate and incommensurate high-temperature phases of A2BO4 compounds

The incommensurate and commensurate superstructures of K₂MoO₄, Rb₂WO₄ and K₂WO₄ are shown to have orthorhombic symmetry rather than the hexagonal symmetry, reported earlier. The structures belong essentially to the β-K₂SO₄ type. The β-K₂SO₄ structure can be regarded as a commensurate superstructure of the α-K₂SO₄ structure by doubling of the unit cell. In this sense β-K₂SO₄ and K₂MoO₄ have the same average structures. Rb₂WO₄ displays a lock-in transition at 681 K where the incommensurate distortion wave vector jumps from an incommensurate value to the value 0.5 which results in the β-K₂SO₄ type. The distortion wave vectors of the other compounds range from 0.25 to 0.5.