Showing papers on "Fourier transform infrared spectroscopy published in 1996"
01 Jan 1996
TL;DR: Theoretical analyses of the Amide I Infrared Bands of Globular Proteins (H. Torii & M. Tasumi) were carried out in this article, where the authors used the Fourier Transform Infrared Spectroscopy of Enzyme Systems (J. Cohen and R. Hochstrasser).
Abstract: Theoretical Analyses of the Amide I Infrared Bands of Globular Proteins (H. Torii & M. Tasumi). Fourier Transform Infrared Spectroscopy of Enzyme Systems (J. Alben). Light--Induced Fourier Transform Infrared Difference Spectroscopy of the Primary Electron Donor in Photosynthetic Reaction Centers (E. Nabedryk). Equipment: Slow and Fast Infrared Kinetic Studies (F. Siebert). Ultrafast Infrared Spectroscopy of Biomolecules (B. Cohen & R. Hochstrasser). Infrared Spectroscopy of Nucleic Acids (J. Liquier & E. Taillandier). Fourier Transform Infrared Spectroscopy in the Study of Hydrated Lipids and Lipid Bilayer Membranes (R. Lewis & R. McElhaney). Fourier Transform Infrared Spectroscopic Studies of Cell Surface Polysaccharides (K. Brandenburg & U. Seydel). Fourier Transform Infrared Spectroscopy of Biomembrane Systems (P. Haris & D. Chapman). What Can Infrared Spectroscopy Tell Us About the Structure and Composition of Intact Bacterial Cells? (D. Naumann, et al.). Biomedical Infrared Spectroscopy (M. Jackson & H. Mantsch). New Trends in Isotope--Edited Infrared Spectroscopy (H. Fabian, et al.). Index.
687 citations
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TL;DR: In this paper, transparent and crack free thin films of ZnO have been deposited on fused silica, soda glass, silicon wafers and KBr single crystals using the sol-gel technique.
314 citations
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TL;DR: It is suggested that a combination of second-derivative and curve-fitting analysis of the ν1, ν3 phosphate contour allows the most reproducible evaluation of these spectra.
Abstract: Fourier Transform infrared spectroscopic analysis of maturing, poorly crystalline hydroxyapatite (HA) formed from the conversion of amorphous calcium phosphate (ACP) at constant pH or variable pH show only subtle changes in the v1, v3 phosphate absorption region (900 cm-1-1200 cm-1). This region is of interest because it can be detected by analysis of mineralized tissue sections using FT-IR microscopy. To evaluate the subtle spectral changes occurring during the maturation, second derivatives of the spectra were calculated. HA formed at constant pH showed little or no variation in the second derivative peak positions with bands occurring at 960 cm-1, 985 cm-1, 1030 cm-1, 1055 cm-1, 1075 cm-1, 1096 cm-1, 1116 cm-1, and 1145 cm-1. These bands can be assigned to molecular vibrations of the phosphate (PO4(3-)) moiety in an apatitic/stoichiometric environment of HA. In contrast, during the early stages of maturation of the HA formed at variable pH, second derivative peak positions occurring at 958 cm-1, 985 cm-1, 1020 cm-1, 1038 cm-1, 1112 cm-1, and 1127 cm-1 shifted in position with maturation, indicating that the environment of the phosphate species is changing as the crystals mature. Peaks at 1020 cm-1, 1038 cm-1, 1112 cm-1, and 1127 cm-1 were attributable to nonstoichiometry and/or the presence of acid phosphate-containing species. This concept was supported by the lower Ca:P molar ratios measured by chemical analysis of the synthetic material made at variable pH. Using the second derivative peak positions as initial input parameters, the v1, v3 phosphate region of the synthetic HAs prepared at constant pH were curve fit. X-ray diffraction patterns of these same materials were also curve fit to calculate the changes in crystallinty (size/perfection) in the c-axis 002 reflection as well as the 102, 210, 211, 112, 300, 202, and 301 planes. Linear regression analysis showed that the changes in the percent area of the underlying bands at 982 cm-1, 999 cm-1, 1030 cm-1, 1075 cm-1, 1096 cm-1, 1116 cm-1, and 1145 cm-1 were correlated with changes in crystallinity in one or more of the reflection planes. It is suggested that a combination of second-derivative and curve-fitting analysis of the v1, v3 phosphate contour allows the most reproducible evaluation of these spectra.
299 citations
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TL;DR: Chitosan films were acylated under heterogeneous conditions in methanol with acetic and hexanoic anhydrides and characterized by proton nuclear magnetic resonance, elemental analysis, and multiple internal reflective Fourier transform infrared spectroscopy as discussed by the authors.
Abstract: Chitosan films were acylated under heterogeneous conditions in methanol with acetic and hexanoic anhydrides and characterized by proton nuclear magnetic resonance, elemental analysis, and multiple internal reflective Fourier transform infrared spectroscopy. The disappearance of the NH2 vibrational band at 1590 cm-1, the appearance of the amide II band at 1555 cm-1, and the relatively low intensity of the ester band at 1735 cm-1 showed that acylation at the surface was site-selective for the amino (N) functionalities. Furthermore, N-acylation at the surface region appeared complete within 1 h. The acylated chitosan films were fractionated in aqueous acetic acid for compositional analysis. Acetylation of chitosan films for 3 h gave 52% of aqueous acetic acid insoluble chitin (outer film region) and 48% unreacted chitosan. In contrast, 3 h hexanoylation reactions resulted in 99% aqueous acetic acid soluble product. Thus, film N-acetylation was more rapid than N-hexanoylation. Moreove...
251 citations
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TL;DR: In this article, a set of solvents, propylene carbonate (PC), ECC−dimethyl carbonate mixtures, and 1,3-dioxolane, were investigated with respect to the effect of storage time.
Abstract: Li electrodes prepared in situ in solutions and then stored in them for different periods were studied by X-ray photoelectron spectroscopy (XPS) including depth profiling performed by argon sputtering followed by XPS. A set of solvents, propylene carbonate (PC), ethylene carbonate (EC)−dimethyl carbonate (DMC) mixtures, and 1,3-dioxolane, and a set of salts, LiAsF6, LiBF4, LiPF6, LiN(SO2CF3)2, and LiC(SO2CF3)3, were investigated with respect to the effect of storage time. The results of this study were compared with previous studies of Li electrodes in the same solutions by in situ and ex situ Fourier transform infrared spectroscopy. Basically, the results thus obtained are in line with the previous studies. The Li surface chemistry is dominated by solvent reactions. However, all the above salt anions are also reduced to form insoluble species which also contribute to the build-up of the surface films (e.g., the salt anions of the type MFy- (M = As, P, B) are reduced to LiF and species of the LixMFz type)...
239 citations
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TL;DR: From the results of this study it is suggested that 600 degrees C is probably the best annealing temperature to obtain a better characterization and understanding of the coating.
227 citations
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TL;DR: In this paper, thin films of the cubic spinel Co{sub 3}O{sub 4} were prepared by the sol-gel route from a Co(II) sulfate precursor using a dip-coating technique.
Abstract: Thin films of the cubic spinel Co{sub 3}O{sub 4} were prepared by the sol-gel route from a Co(II) sulfate precursor using a dip-coating technique. The films (50 to 60 nm thick) were deposited on indium-tin oxide glass substrates with a single dipping. The electrochromic properties of the films were studied in an aqueous alkaline electrolyte (0.1 M LiOH) using cyclic voltammetry (CV) and in situ UV-vis spectroelectrochemistry. The intermediate oxide products that appeared during cycling at current peak potentials were analyzed by x-ray diffraction (XRD) and ex situ Fourier transform infrared (FTIR) reflection-absorption spectroscopy performed at near-grazing incidence angle conditions (NGIA). High hydration of the spinel structure enables complex redox processes to take place inside the structure or on the surface of the film when potential cycling is performed. Vibrational bands characteristic of the formation of CoO, Co(OH){sub 2}, and hydrated Co{sub 3}O{sub 4} phases have been assigned and discussed according to the results obtained from ex situ NGIA FTIR, CV, and XRD studies. The change in transmittance ({lambda} = 634 nm) between bleached and colored states for single-dipped films was 25%, and for electrochromic efficiency ({eta}) was approximately 25 cm{sup 2}/C.
196 citations
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TL;DR: In this article, Fourier transform infrared spectroscopy was used to identify five-membered cyclic an hydride intermediates formed under the curing conditions of polycarboxylic acids.
Abstract: Multifunctional polycarboxylic acids have been used as nonformaldehyde cross linking agents for cotton fabrics to replace the traditional N-methylol reagents. Ester ification of cotton cellulose by seventeen aliphatic and aromatic polycarboxylic acids is studied using Fourier transform infrared spectroscopy. Five-membered cyclic an hydride intermediates formed under the curing conditions are identified on cotton fabrics treated with these acids. Only those polycarboxylic acids that form cyclic an hydride intermediates esterify cotton cellulose. Formation of the cyclic anhydride intermediates and esterification of cotton cellulose take place in the same curing tem perature regions. The infrared spectroscopy data also indicate that the second carboxyl group in a bifunctional carboxylic acid is not able to esterify cotton cellulose effectively. Therefore, we can conclude that a polycarboxylic acid esterifies cotton cellulose through the formation of a cyclic anhydride intermediate. The infrared spectroscopy ...
181 citations
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TL;DR: In this article, the conformation of gelatin during the gel melting process is monitored by Fourier Transform infrared spectroscopy, and the viability of this methodology for studying gelation is established.
162 citations
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TL;DR: In this article, three monothiolated cyclodextrinthiol derivatives with different spacers between the cylindrical cavity and the thiol group were synthesized and characterized.
Abstract: Several different cyclodextrinthiol derivatives have been immobilized on gold surfaces through a chemisorption process to form films which exhibit significantly different features. Three monothiolated cyclodextrin derivatives with different spacers between the cyclodextrin cavity and the thiol group and a mixture of multithiolated cyclodextrins were synthesized and characterized. Chemisorption of these compounds onto gold surfaces gave films which were investigated by Fourier transform infrared (FTIR) spectroscopy, time-of-flight mass spectrometry, contact angle measurements, plasmon surface polariton (PSP) spectroscopy, and cyclic voltammetry. It was found that the chemical structure of each cyclodextrin derivative had a strong influence on the molecular architecture in the resulting films, and in particular on the orientation of the cyclodextrin torus. Models were developed to describe the molecular arrangement in the films.
159 citations
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TL;DR: In this paper, a fiber-optics-based Fourier transform infrared (FOB-FTIR) spectroscopy was used for in situ monitoring of input partial pressures of organometallic precursors.
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TL;DR: The most important structure modifications appeared between 300 and 400 °C, and they are characterized by the decrease of intensities of C O and C C C bands and the formation of alkyl bands as discussed by the authors.
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TL;DR: Fluorescence quenching experiments confirmed that MgATP-induced changes are to be found in the tertiary structure of the enzyme.
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TL;DR: Fourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of beta-lactoglobulin under various physicochemical conditions as mentioned in this paper.
Abstract: Fourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of beta-lactoglobulin under various physicochemical conditions. The effects of pH (3-9), NaCl (0-2 M), and lactose, glucose and sucrose (100-500 g/l) in the temperature range 25-100 degrees C on the conformation sensitive amide I band in the i.r. spectrum of beta-lactoglobulin in D2O solution were examined. The 1692 cm-1 band in the amide I band profile had not been definitively assigned in previous studies of the i.r. spectrum of beta-lactoglobulin. The decrease in this band at ambient temperature with time or upon mild heating was attributed to slow H-D exchange, indicating that it was due to a structure buried deep within the protein. The disappearance of the 1692 cm-1 band on heating was accompanied by the appearance of two bands at 1684 and 1629 cm-1, assigned to beta-sheets. The 1692 cm-1 band was therefore attributed to a beta-type structure. beta-Lactoglobulin showed maximum thermal stability at pH 3 and was easily denatured at pH 9. On denaturation, the protein unfolded into more extensive random coil structures at pH 9 than at pH 3. After 10 h at pH 9 (25 degrees C), beta-lactoglobulin was partly denatured. Heating to 60-80 degrees C generally resulted in the loss of secondary structure. At all pH values studied, two new bands at 1618 and 1684 cm-1, characteristic of intermolecular beta-sheet structure and associated with aggregation, were observed after the initial denaturation. Differential scanning calorimetry studies indicated that the thermal stability of beta-lactoglobulin was enhanced in the presence of sugars. The Fourier transform i.r. results obtained provide evidence that sugars promoted the unfolding of beta-lactoglobulin via multiple transition pathways leading to a transition state resisting aggregation.
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TL;DR: In this paper, the combination of electrochemistry in the absence of liquid electrolyte with internal reflectance FT-IR spectroscopy was accomplished using a simple two-electrode sandwich-type cell in which a crystalline germanium served both as a working electrode and an infrared transparent element.
Abstract: Interfacial oxidation and reduction of Prussian Blue (PB), KFeIII[FeII(CN)6]·nH2O (n ≈ 10), powder were probed in situ with Fourier transform infrared attenuated total reflection (FT-IR/ATR) spectroscopy. The combination of electrochemistry in the absence of liquid electrolyte with internal reflectance FT-IR spectroscopy was accomplished using a simple two-electrode sandwich-type cell in which a crystalline germanium served both as a working electrode and an infrared transparent element. Application of sufficiently large potential differences to sandwich electrodes led to oxidation and reduction of PB at opposing interfaces. The spectra, which were monitored by difference, clearly show changes in the cyanide stretching frequency range upon oxidation and reduction.
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TL;DR: In this paper, the authors performed laboratory measurements of NO2 absorption cross-section using a Fourier transform spectrometer at 2 and 16 cm-1 (0.03 and 0.26 nm at 400 nm).
Abstract: New laboratory measurements of NO2 absorption cross-section were performed using a Fourier transform spectrometer at 2 and 16 cm-1 (0.03 and 0.26 nm at 400 nm) in the visible range (380–830 nm) and at room temperature. The use of a Fourier transform spectrometer leads to a very accurate wavenumber scale (0.005 cm-1, 8×10-5 nm at 400 nm). The uncertainty on the new measurements is better than 4%. Absolute and differential cross-sections are compared with published data, giving an agreement ranging from 2 to 5% for the absolute values. The discrepancies in the differential cross-sections can however reach 18%. The influence of the cross-sections on the ground-based measurement of the stratospheric NO2 total amount is also investigated.
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TL;DR: This work finds that the observed band profile can be reproduced with very small random variation on the phi, psi of tropomyosin, and believes that the shift to lower frequency is due to additional hydrogen bonding of the solvent accessible backbone CO groups to water.
Abstract: The Fourier transform infrared (FTIR) spectra of several coiled-coil proteins have been shown to possess unusual features in the amide I‘ region. Band maxima occur in the vicinity of 1630 cm-1, with component bands at higher frequency. This is well below the observed band at 1650 cm-1 found in standard α-helical polypeptides such as poly-l-alanine. Normal mode calculations on models of the coiled-coil structure have been performed to investigate this issue. We find that the observed band profile can be reproduced with very small random variations on the φ,ψ of tropomyosin. We believe that the shift to lower frequency is due to additional hydrogen bonding of the solvent accessible backbone CO groups to water.
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TL;DR: In this article, an indium antimonide (InSb) focal-plane array detector and a commercially available step-scan Fourier transform infrared spectrometer (FTIR) were used to generate image contrast in sections of monkey brain tissue and relate these data to specific lipid and protein fractions.
Abstract: We demonstrate a new mid-infrared and near-infrared imaging approach which is ideally suited to microscopic applications. The method employs an indium antimonide (InSb) focal-plane array detector and a commercially available step-scan Fourier transform infrared spectrometer (FTIR). With either a KBr or a CaF2 beamsplitter, images from 1 to 5.5 μm (10,000–1818 cm-1) can be rapidly acquired with the use of all the available pixels on the detector. The spectral resolution for each image is easily varied by changing the number of acquired images during the interferometer scan. We apply this technique to noninvasively generate image contrast in sections of monkey brain tissue and to relate these data to specific lipid and protein fractions. In addition, we describe several computational methods to highlight the spatial distributions of components within a sample.
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TL;DR: In this paper, the structure and bond formation in the SiCN films were discussed in terms of the present results, and the properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X-ray photoelectron, and Auger electron spectrographs.
Abstract: Silicon–carbon–nitrogen alloys have been deposited by electron cyclotron resonance plasma chemical vapor deposition. Nitrogen, methane, and argon diluted silane have been used as precursor gases. The properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X‐ray photoelectron, and Auger electron spectroscopy. The structure and bond formation in the SiCN films is discussed in terms of the present results.
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TL;DR: In situ attenuated total reflection Fourier transform infrared spectroscopy was employed in proposing possible surface reaction mechanisms during plasma enhanced chemical vapor deposition of SiO2 from a mixture of SiH4, O2, and Ar in a helical resonator plasma reactor as discussed by the authors.
Abstract: In situ attenuated total reflection Fourier transform infrared spectroscopy was employed in proposing possible surface reaction mechanisms during plasma enhanced chemical vapor deposition of SiO2 from a mixture of SiH4, O2, and Ar in a helical resonator plasma reactor. Infrared spectra taken during the oxide deposition revealed that the oxide surface is covered with OH when the deposition is conducted with a low SiH4 to O2 ratio (≪1). Both associated hydroxyls (SiOHassoc) and isolated hydroxyls (SiOHisol) were detected on the surface during growth. Two kinds of OH attached to Si exist on the surface: weakly bound OH that thermally desorb at 250 °C and strongly bound OH that desorb under ion bombardment. The thermal removal of weakly bound OH does not lead to SiO2 formation, but the ion‐assisted removal of strongly bound OH by Ar+ ion bombardment results in oxide growth via the reaction 2SiOH(s)+Ar+→Si–O–Si(s)+H2O(g)+Ar+. Experiments undertaken to delineate the possible heterogeneous reaction paths between...
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TL;DR: In this article, the post-synthetic incorporation of titanium in the borosilicate SSZ-33 and the direct synthesis of an aluminum-free titanium-containing zeolite Beta (Ti-Beta) are reported.
Abstract: The post-synthetic incorporation of titanium in the borosilicate SSZ-33 and the direct synthesis of an aluminum-free titanium-containing zeolite Beta (Ti-Beta) are reported. These materials are characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), FT-Raman, and diffuse reflectance ultraviolet (DR-UV) spectroscopies. The molecular sieves are shown to catalyze the epoxidation of various olefins using aqueous hydrogen peroxide as the oxidant. The physicochemical properties as found by the characterization methods are correlated to the catalytic data and the results compared to a high quality sample of TS-1. The modified SSZ-33 samples contain titanium primarily in the form of isolated tetrahedrally coordinated Ti atoms, although some extra-framework Ti is observed by Raman and DR-UV spectroscopies. Ti-Beta samples show no evidence of extra-framework titanium. For the epoxidation of cis -cyclooctene, the Ti-Beta catalysts give quantitative conversion to epoxide, and both the Ti-Beta and Ti-SSZ-33 catalysts are able to epoxidize substrates too large to be oxidized by TS-1.
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TL;DR: In this paper, a broad blue photoluminescence band with nanosecond decay times gradually appears when heavily oxidized porous silicon is stored in ambient air for prolonged periods.
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TL;DR: In this paper, a pulsed multiplex cavity ring down (CRD) spectrometer was proposed for the detection of molecular oxygen using the Fourier transform (FT) spectrum.
Abstract: We present a pulsed multiplex absorption spectrometer in which the sensitivity of the cavity ring down absorption detection technique is combined with the multiplex advantage of a Fourier Transform spectrometer. A description of the Fourier transform cavity ring down (CRD) spectrometer—substantiated with first experimental results on the atmospheric band of molecular oxygen—is given. It is shown that as in the case of normal CRD spectroscopy, the measurement is independent of light intensity fluctuations provided the spectral intensity distribution of the light source is known and is constant during the measurement.
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TL;DR: Evidence that DPPC analogs with ether-linked hydrocarbon chains spontaneously form chain-interdigitated gel phases at low temperatures clearly indicate that the properties of lipid bilayers can be substantially altered by small changes in the chemical structures of their polar/polar interfaces, and highlight the critical role of the interfacial region as a determinant of the structure and organization of lipid assemblies.
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TL;DR: In this paper, the chemical and structural evolution of hydroxyapatite thin films produced by sol-gel synthesis is characterized by ion beam analysis, X-ray diffraction, and Fourier transform infrared spectroscopy.
Abstract: Chemical and structural evolution of hydroxyapatite thin films produced by sol-gel synthesis is characterized by ion beam analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. Formation of the hydroxyapatite structure began at 500°C ; no other phases were observed at higher temperatures. Elimination of residual organics was observed in the form of the disappearance of excess oxygen, hydrogen and carbon. Crystal size increases with increasing anneal temperature ; spectroscopy indicates the formation of highly crystalline films. The analytical methods chosen provide insight into subtle chemical and structural changes which occur in films produced by this synthetic route.
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TL;DR: Fourier transform infrared spectroscopy (FT-IR), surface-enhanced Raman spectroscopic (SERS), and nuclear magnetic resonance (NMR) (1H, 13C, and 31P) have been applied to the study of fractions of humic acids in Irish peat as discussed by the authors.
Abstract: Fourier transform infrared spectroscopy (FT-IR), surface-enhanced Raman spectroscopy (SERS), and nuclear magnetic resonance (NMR) (1H, 13C, and 31P) have been applied to the study of fractions of humic acids in Irish peat. Owing to the high fluorescence of these materials, no Raman spectra have been obtained, up to now, for the characterization of humic acids. The SERS technique was employed for the first time in the study of these complex substances, demonstrating that very valuable information about the aromatic groups and the spacial conformation of these macromolecules in water solution can be obtained. The combined use of these techniques has evidenced an increase of oxygenated groups in those fractions containing humic acids with low molecular weight. The presence of a greater number of carboxylate and phenolic groups can explain the high concentration of metals and phosphate ions found in these fractions.
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TL;DR: In this article, the structure and relative strength of the interactions between metal sulfonate and amide groups in blends of lightly sulfonated polystyrene ionomers and an N-methylated polyamide, poly(N,N-dimethylethylene sebacamide), and low molecular weight model complexes were characterized.
Abstract: Electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR), and solid-state 15N nuclear magnetic resonance (15N-NMR) spectroscopies were used to characterize the structure and relative strength of the interactions between metal sulfonate and amide groups in blends of lightly sulfonated polystyrene ionomers and an N-methylated polyamide, poly(N,N‘-dimethylethylene sebacamide), and low molecular weight model complexes. The metal sulfonate groups, which aggregate in the neat ionomer, were dispersed by the polyamide in the blend as a consequence of a complexation that involved the sulfonate cation and both the carbonyl oxygen and the amide nitrogen of the polyamide. The FTIR and 15N-NMR spectra were consistent with a 2pz electron redistribution model for the complex, in which electrons migrate from the nitrogen to the metal ion through the carbonyl group. The sulfonate anion did not appear to particpate in the complex, but it remained in the vicinity of the metal cation. The strength of the ion−...
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TL;DR: In this paper, the layer by layer growth of Al 2 O 3 from trimethylaluminium (TMA) and water vapour by atomic layer epitaxy (ALE) has been studied on porous large surface area silica.