In situ FT-IR spectroscopy study on the conformational changes of quenched isotactic polypropylene during stepwise heating

The conformational changes of quenched isotactic polypropylene (iPP) during stepwise heating have been carefully studied by in situ Fourier-transform infrared (FT-IR) spectroscopy. Analysis of the corresponding spectra shows that the mechanism of the extension of short helix into long one happens. Furthermore, it is easier for short helix at 998 cm⁻¹ band to extend into long one than that of short helix at 973 cm⁻¹ band. Meanwhile, for the higher order regularity band at 841 cm⁻¹, the melting-recrystallization seems to occur. However, the number of the higher order regularity band at 1220 cm⁻¹ hardly remains change, which shows the limited increment of the higher order regularity band for quenched iPP in the whole heating process. In summary, two proposed mechanisms, the extension of short helix into long one and the melting-recrystallization of the long helix, happen during stepwise heating, which may give us new insights on the mesomorphic-to-monoclinic phase transition mechanism of quenched iPP from a molecular structure viewpoint.     

Theoretical and experimental infrared spectra of hydrated and dehydrated sulfonated poly(ether ether ketone)

Time-dependent FT-IR spectra of sulfonated poly(ether ether ketone) during dehydration show diminishing 1081 cm⁻¹ and 1023 cm⁻¹ band intensities concurrent with the emergence and shifting of bands at 1362 cm⁻¹ and 898 cm⁻¹. Animations of density functional theory calculated normal modes enable assignment of the 1081 cm⁻¹ and 1023 cm⁻¹ bands as group modes that include a sulfonate exchange site with C_3v local symmetry, while the 1362 cm⁻¹ and 898 cm⁻¹ bands are assigned as group modes that include an associated sulfonic acid with no local symmetry (C₁). In contrast to analogously assigned Nafion group mode bands, the SPEEK C_3v and C₁ bands coexist throughout the entire dehydration–hydration cycle, suggesting the presence of associated and dissociated exchange sites in SPEEK at all states-of-hydration. This supports a morphological model for SPEEK featuring branched hydrophilic domains and dead-end aqueous confines.     

Photoelectrochemical characterization of the synthetic crednerite CuMnO<Subscript>2</Subscript>

High quality crednerite CuMnO₂ was prepared by solid state reaction at 950 °C under argon flow. The oxide crystallizes in a monoclinically distorted delafossite structure associated to the static Jahn–Teller (J–T) effect of Mn³⁺ ion. Thermal analysis showed that it converts reversibly to spinel Cu _x Mn_3−x O₄ at ~420 °C in air and further heating reform the crednerite above 940 °C. CuMnO₂ is p-type, narrow semiconductor band gap with a direct optical gap of 1.31 eV. It exhibits a long-term chemical stability in basic medium (KOH 0.5 M), the semi logarithmic plot gave an exchange current density of 0.2 μA cm⁻² and a corrosion potential of ~−0.1 V_SCE. The electrochemical oxygen insertion/desinsertion is evidenced from the intensity–potential characteristics. The flat band potential (V _fb = −0.26 V_SCE) and the holes density (N _A  = 5.12 × 10¹⁸ cm⁻³) were determined, respectively, by extrapolating the curve C ⁻² versus the potential to the intersection with C ⁻²  = 0 and from the slope of the Mott–Schottky plot. From photoelectrochemical measurements, the valence band formed from Cu-3d wave function is positioned at 5.24 ± 0.02 eV below vacuum. The Nyquist representation shows straight line in the high frequency range with an angle of 65° ascribed to Warburg impedance originating from oxygen intercalation and compatible with a system under mass transfer control. The electrochemical junction is modeled by an equivalent electrical circuit thanks to the Randles model.     

Novel PEO-based solid composite polymer electrolytes with inorganic–organic hybrid polyphosphazene microspheres as fillers

Novel solid-state composite polymer electrolytes based on poly (ethylene oxide) (PEO) by using LiClO₄ as doping salts and inorganic–organic hybrid poly (cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) microspheres as fillers were prepared. Electrochemical and thermal properties of PEO-based polymer electrolytes incorporated with PZS microspheres were studied. Differential scanning calorimetry (DSC) results showed there was a decrease in the glass transition temperature of the electrolytes and the crystallinity of the samples in the presence of the fillers. Maximum ionic conductivity values of 1.2 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.5 × 10⁻⁴ S cm⁻¹ at 80° were obtained and lithium ion transference number was 0.29. Compared with traditional ceramic fillers such as SiO₂, the addition of PZS microspheres increased the ionic conductivity of the electrolytes slightly and led to remarkable enhancement in the lithium ion transference number.     

Investigation of N<Subscript>2</Subscript>-fixation on polyaniline electrodes in methanol by electrochemical impedance spectroscopy

The ac response of polyaniline thin films on platinum electrodes was measured at different dc potentials during the N₂-fixation in methanol + LiClO₄ electrolyte with 0.03 mol L⁻¹ H₂SO₄ for the first time. The optimum film thickness was found to be 1.5 μm, N₂-pressure 50 bar and an optimum electrolysis potential of −0.12 V (NHE). The diffusion coefficients for N₂ into the polymer film was found to be (5 ± 2)×10⁻⁹ cm² s⁻¹.     

An infrared absorption study of autoxidized methyl linoleate

Summary A study has been made of the infrared absorption spectra of autoxidized methyl linoleate in samples ranging from PV 1 to PV 940 m.e./kg. Principal changes occur in the frequency range 3400–3550 cm⁻¹ where bonded−OH groups absorb and at 1650–1775 cm⁻¹ where >c=0 groups absorb. Two maxima were observed in oxidized samples in the −OH absorption range: one sharp and distinct at 3467–70 cm⁻¹ which increased in intensity with increase in PV and a broad band which increased with increasing PV until it resolved into a true maximum at 3430 cm⁻¹. Reduction of typical oxidized samples with KI reagent resulted in disappearance of the 3430 cm⁻¹ band and appearance of a new band above 3500 cm⁻¹. The band at 3430 cm⁻¹ was attributed to −OOH groups associated by hydrogen bridging. The band at 3467 cm⁻¹ and the band appearing above 3500 cm⁻¹ were attributed to −OH groups, the band at the higher frequency resulting directly from reduction of a hydroperoxide. Absorption due to ketone and aldehyde carbonyl groups appeared only as an indefinite shoulder on the band due to the ester carbonyl. These were resolved by using the intensity of the sample with PV 1 as I_o and that for the oxidized samples as I. A plot of Log I_o/I then revealed three maxima. These indicate the presence of two and possibly three carbonyl containing substances other than the ester carbonyl in autoxidized methyl linoleate. Absorption in the two critical frequency ranges of fractions of autoxidized methyl linoleate eluted from an adsorption column correlate with interpretations made from ultraviolet absorption studies of the same substances. This paper reports research undertaken in cooperation with the Quartermaster Food and Container Institute for the Armed Forces and has been assigned number 211 in the series of papers approved for publication. The views or conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or indorsement of the Department of the Army. Presented at the Fall Meeting of the American Oil Chemists’ Society, New York, Nov. 17, 1948.     

P(VDF-HFP)-based micro-porous composite polymer electrolyte prepared by in situ hydrolysis of titanium tetrabutoxide

A micro-porous composite polymer electrolyte (MCPE) was prepared in situ by adding TiO₂ nanoparticles from the hydrolysis of titanium tetrabutoxide to a solution of poly(vinylidenefluoride-co-hexafluoropropylene) [P(VDF-HFP)] copolymer. The prepared microporous polymer films (MCPFs) were characterized by scanning electronic microscopy, X-ray diffraction, thermogravimetric analysis, FT-IR and electrochemical interface resistance. After the addition of TiO₂ nanoparticles the polarity of CF₂ groups in the polymer chains and the crystallinity of the MCPFs decreased. When the composite polymer film contained 8.5 wt% of TiO₂ nanoparticles the MCPE exhibited excellent electrochemical properties such as high ionic conductivity, up to 2.40 × 10⁻³ S cm⁻¹ at room temperature.     

Electrical properties of poly(vinyl alcohol) (PVA) based on LiFePO<Subscript>4</Subscript> complex polymer electrolyte films

Li ion conducting polymer electrolyte films were prepared based on poly(vinyl alcohol) (PVA) with 5, 10, 15, 20, 25 and 30 wt% lithium iron phosphate (LiFePO₄) salt using a solution-casting technique. X-ray diffraction (XRD) was used to determine the complexation of the polymer with LiFePO₄ salt. Differential scanning (DSC) calorimetry was used to determine the melting temperatures of the pure PVA and complexed films. The maximum ionic conductivity was found to be 1.18 × 10⁻⁵ S cm⁻¹ for (PVA:LiFePO₄) (75:25) film, which increased to 3.12 × 10⁻⁵ S cm⁻¹ upon the addition of propylene carbonate (PC) plasticizer at ambient temperature. The Li⁺ ion transport number was found to be 0.40 for (PVA: LiFePO₄) (75:25) film using AC impedance and DC polarization methods. Dielectric studies were performed for these polymer electrolyte films in the frequency range of 10 Hz to 10 MHz at different temperatures. The activation energies of the complexed films were calculated from the dielectric loss tangent spectra and were found to be 0.35, 0.30, 0.27 and 0.28 eV. The cyclic voltammogram (CV) curves of (PVA: LiFePO₄) (75:25)+PC film exhibited higher specific capacities than those for other films.     

Preparation and electrochemical performance of gel polymer electrolytes with a novel star network

Well-defined star shaped polymers with α-Cyclodextrin (α-CD) core linking PMMA-block arms were synthesized by atom transfer radical polymerization (ATRP). Gel polymer electrolytes (GPEs) were prepared by encapsulating electrolyte solution of 1 mol L⁻¹ of LiClO₄/EC-PC (volume 1:1) into the obtained star shaped polymer host. The ionic conductivity of the GPEs and the cycling characteristics of LiCoO₂/GPEs/Graphite cell were studied by electrochemical impedance spectroscopy and charge-discharge testing, respectively. The results indicate that the GPEs have a high ionic conductivity up to 1.63 × 10⁻³ S cm⁻¹ at room temperature and exhibit a high electrochemical stability potential of 4.5 V (vs. Li/Li⁺). The discharge capacity of LiCoO₂/GPEs/Graphite cell is about 98% of its initial discharge capacity after 20 cycles at 0.1 C rate. Discharge capacity of the model cell with GPEs is stable with charge-discharge cycling.     

Preparation of a PVA/HAP composite polymer membrane for a direct ethanol fuel cell (DEFC)

A novel PVA/Hydroxyapatite (HAP) composite polymer membrane was prepared by the direct blend process and solution casting method. The characteristic properties of the PVA/HAP composite polymer membranes were investigated using thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-Raman spectroscopy and the AC impedance method. An alkaline direct ethanol fuel cell, consisting of an air cathode with MnO₂ carbon inks based on Ni-foam, an anode with PtRu black on Ni-foam, and the PVA/HAP composite polymer membrane, was assembled and investigated. It was found that the alkaline direct ethanol fuel cell comprising of a novel cheap PVA/HAP composite polymer membrane showed an improved electrochemical performance in ambient temperature and air. As a result, the maximum power density of the alkaline DEFC, using a PtRu anode based on Ni-foam (10.74 mW cm⁻²), is higher than that of DEFC using an E-TEK PtRu anode based on carbon (7.56 mW cm⁻²) in an 8M KOH + 2M C₂H₅OH solution at ambient temperature and air. These PVA/HAP composite polymer membranes are a potential candidate for alkaline DEFC applications.     

Synthesis, Characterization, Conductivity, Band Gap, and Thermal Analysis of Poly-[(2-mercaptophenyl)iminomethyl]-2-naphthol and Its Polymer–Metal Complexes

Oxidative polycondensation reaction conditions of [(2-mercaptophenyl)iminomethyl]-2-naphthol (2-MPIM-2N) were studied using oxidants such as air and NaOCl in an aqueous alkaline medium between 40 °C and 90 °C. The structure of poly-[(2-mercaptophenyl)iminomethyl]-2-naphthol (P-2-MPIM-2N) was characterized by ¹H- ¹³C NMR, FT-IR, and UV–Vis spectroscopy, size exclusion chromatography (SEC), and elemental analysis. At optimum reaction conditions, the yield of P-2-MPIM-2N was found to be 78 and 82% for air and NaOCl oxidants, respectively. From SEC measurements, the number-average molecular weight (M _n ), weight-average molecular weight (M _w ) and polydispersity index (PDI) of P-2-MPIM-2N are 2900, 3500 g mol⁻¹ and 1.207; 2200, 2500 g mol⁻¹ and 1.136, for air and NaOCl oxidants, respectively. Polymer–metal complexes were synthesized by the reaction of P-2-MPIM-2N with Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and electrochemical band gaps (E^￠_g E^{\prime}_{g} ) of 2-MPIM-2N and P-2-MPIM-2N were −5.97, −2.66 and 3.31 eV and −5.82, −2.68 and 3.14 eV, respectively. The conductivity of polymer and polymer–metal complexes were determined in the solid state. Conductivity measurements of doped and undoped Schiff base polymer and polymer–metal complexes were carried out at room temperature and atmospheric pressure by the four-point probe technique using an electrometer. The conductivities of the polymer and polymer–metal complexes increased when iodine was used as doping agent.     

Long-term behavior of oil-based varnishes and paints I. Spectroscopic analysis of curing drying oils

The curing of drying oils at 60°C has been investigated by Fourier transform infrared spectroscopy and Fourier transform Raman analysis of linseed oil and poppyseed oil. In the first step, hydroperoxides are formed (broad vibration band centered around 3425 cm⁻¹) with concomitant conjugation and cis-trans isomerization of the double bonds (disappearance of cis bands at 3011 and 716 cm⁻¹, appearance of trans conjugated and trans nonconjugated bands at 987 and 970 cm⁻¹). The subsequent decomposition of hydroperoxides in the presence of oxygen leads to the formation of alcohols (nitrite band at 779 cm⁻¹ after nitrogen monoxide treatment), aldehydes (bands at 2810 and 2717 cm⁻¹ in gas phase), ketones (saturated and unsaturated at 1720 and 1698 cm⁻¹, respectively), carboxylic acids (saturated and unsaturated acid fluorides identified at 1843 and 1810 cm⁻¹ after SF₄ treatment), and peresters or γ-lactones (near 1770 cm⁻¹). A rapid decrease in the double-bond concentration is recorded when curing continues, and the formation of epoxides, characterized by a vibration band at 885 cm⁻¹, is observed. Thermolysis experiments have suggested the proposal of a reaction of addition of peroxyl radicals on the conjugated double bonds as a probable mechanism. This mechanism explains both the rapid disappearance of conjugated double bonds and the formation of epoxides as intermediate products observed in the initial step of curing.     

One-Dimensional Hydrogen-Bonded Polymer from Hexaazamacrotetracyclic Nickel(II) Complex and trans-1,4-Cyclohexanedicarboxylate Ligand

The reaction of [Ni(L)](ClO₄)₂·2H₂O (L) = 1,3,10,12,16,19-hexaazatetracyclo[17,3,1,1^12.16,0^4.9]tetracosane) with trans-1,4-cyclohexanedicarboxylic acid (H₂-chdc) produces a 1D hydrogen-bonded polymer with formula [Ni(L)(H-chdc⁻)₂] (1). This polymer complex has been characterized by X-ray crystallography, spectroscopy and magnetic susceptibility. The crystal structure of 1 shows a distorted octahedral coordination geometry about Ni with two secondary and two tertiary amines of the macrocycle and two oxygen atoms of the H-chdc⁻ ligand at the trans position. Electronic spectrum of 1 exhibits a high-spin octahedral environment. The magnetic behavior of 1 reveals a very weak antiferromagnetic interaction with J values of −0.66(2) cm⁻¹ .     

Effect of Composition on Electrical and Optical Properties of Thin Films of Amorphous GaxSe100?x Nanorods

We report the electrical and optical studies of thin films of a-Ga _x Se_100−x nanorods (x = 3, 6, 9 and 12). Thin films of a-Ga _x Se_100−x nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-Ga _x Se_100−x nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (σ₀) is of the order of 10¹ Ω⁻¹ cm⁻¹, which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration.     

Infrared Study of Benzene Hydrogenation on Pt/SiO2 Catalyst by Co-adsorption of CO and Benzene

FT-IR spectra of the co-adsorption of benzene and CO have been performed to identify the preferred adsorption sites of hydrogen and benzene on a Pt/SiO₂ catalyst for hydrogenation of benzene. Results of CO adsorbed on atop sites on Pt/SiO₂ includes: an α peak at 2091 cm⁻¹, a β peak at 2080 cm⁻¹ and a γ peak at 2067 cm⁻¹ indicating three kinds of adsorption sites for dissociative hydrogen on Pt/SiO₂. The site of lowest CO stretching frequency offers stronger adsorbates–metal interaction for benzene and hydrogen. Hydrogen binding on the site of lowest CO stretching frequency before benzene adsorption significantly enhances the reaction rate of benzene hydrogenation.     

Formation and Migration of NCO Species on Ag/SiO2 Catalyst

The adsorption of HNCO has been investigated on Ag/SiO₂ catalyst by means of FTIR spectroscopy. Adsorption of HNCO on the reduced sample at 190 K produced an absorption band at 2,170 cm⁻¹ attributed to NCO bonded to Ag. Annealing the adsorbed layer under continuous degassing, the 2,170 cm⁻¹ band gradually attenuated and at the same time a spectral feature at 2,300 cm⁻¹ due to Si–NCO developed. From these spectral changes it was inferred that NCO bonded to Ag spilt over onto silica.     

Hollow Sodium Tungsten Bronze (Na0.15WO3) Nanospheres: Preparation, Characterization, and Their Adsorption Properties

Abstract  

We report herein a facile method for the preparation of sodium tungsten bronzes hollow nanospheres using hydrogen gas bubbles as reactant for chemical reduction of tungstate to tungsten and as template for the formation of hollow nanospheres at the same time. The chemical composition and the crystalline state of the as-prepared hollow Na_0.15WO₃ nanospheres were characterized complementarily, and the hollow structure formation mechanism was proposed. The hollow Na_0.15WO₃ nanospheres showed large Brunauer–Emment–Teller specific area (33.8 m² g⁻¹), strong resistance to acids, and excellent ability to remove organic molecules such as dye and proteins from aqueous solutions. These illustrate that the hollow nanospheres of Na_0.15WO₃ should be a useful adsorbent.     

Polymeric ionic liquid membranes as electrolytes for lithium battery applications

A new kind of polymeric ionic liquid (PIL) membrane based on guanidinium ionic liquid (IL) with ester and alkyl groups was synthesized. On addition of guanidinium IL, lithium salt, and nano silica in the PIL, a gel PIL electrolyte was prepared. The chemical structure of the PIL and the properties of gel electrolytes were characterized. The ionic conductivity of the gel electrolyte was 5.07 × 10⁻⁶ and 1.92 × 10⁻⁴ S cm⁻¹ at 30 and 80 °C, respectively. The gel electrolyte had a low glass transition temperature (T _g ) under −60 °C and a high decomposition temperature of 310 °C. When the gel polymer electrolyte was used in the Li/LiFePO₄ cell, the cell delivered 142 mAh g⁻¹ after 40 cycles at the current rates of 0.1 C and 80 °C.     

FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites

Adsorption of N₂ on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm⁻¹ (2255.4 cm⁻¹ after adsorption of ¹⁵N₂). With decreasing equilibrium pressure the complexes tend to loose one N₂ ligand, thus forming linear species characterized by an IR band at 2336.8 cm⁻¹ (2258.7 cm⁻¹ after adsorption of ¹⁵N₂). All species disappear completely after evacuation. Co-adsorption of N₂ and CO revealed that the dinitrogen complexes are formed on Na⁺ cations. The changes in the concentrations of the linear and geminal N₂ species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls. This revised version was published online in July 2006 with corrections to the Cover Date.     

Carbon Subsulphide Polymer (C3S2) X Formation by Arcing Carbon disulphide with the Submerged Carbon Arc

Summary Arcing of liquid carbon disulphide between graphite electrodes at − 80 °C produces elemental sulphur, carbon subsulphide (C₃S₂) having the structure S=C=C=C=S, and three other molecular species whose structure remains unassigned. The results were obtained by liquid chromatography (HPLC) equipped with a diode array detector. No polyynes were detected by HPLC although they form in other solvents by arcing graphite electrodes. It has been proposed that carbon subsulphide is obtained from the interaction between carbon monosulphide (C=S) formed from the plasmalysis of CS₂ with C₂ vapour released by the graphite electrodes. C₃S₂ has been identified in the arced CS₂ solution from its characteristic FT-IR absorption bands at 2059 and 1019 cm⁻¹. During warm-up from − 80 °C to room temperature, the red CS₂ solution with C₃S₂ becomes dark brown and a polymeric product, polycarbon subsulphide (C₃S₂) _X , separates. This polymerization reaction was followed spectroscopically for the first time showing that the disappearance of the characteristic C₃S₂ FT-IR bands are accompanied by the appearance of typical carbon subsulphide polymer bands. The FT-IR spectrum of the polymeric product confirms that it is essentially composed by (C₃S₂) _X , although (CS₂) _X polymer is also identified as minor component. The FT-IR spectrum of the polymeric product does not appear significantly different from the spectra of the polymeric products obtained from photolysis, radiolysis, and sonolysis of CS₂. The thermal behaviour of the polymeric product obtained from arcing CS₂ has been studied by differential scanning calorimetry in static air. No melting point and other transitions are detected until 536 K; at 543 K a sharp exothermal transition occurs. An erratum to this article can be found at