Polarized Infrared Spectroscopy Research Articles

The Effect of Epoxidation on Strain-Induced Crystallization of Epoxidized Natural Rubber.

The effect of epoxidation on strain-induced crystallization (SIC) of epoxidized natural rubber (ENR) and mechanism are studied with synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) and polarized infrared spectroscopy (P-IR). WAXD results reveal that appropriate epoxidation, for example, ENR-25 epoxidized with ≈25% isoprene units, can unexpectedly enhance the SIC of natural rubber (NR), resulting in the improvement of tear resistance. On the other hand, exorbitant epoxidation, for example, ENR-40 epoxidized with ≈40% isoprene units, depresses the SIC and weakens the mechanical properties of NR remarkably. P-IR studies reveal that epoxidation can promote the orientation of chain segments along the stretching direction, which plays a determining role on SIC of NR. Accordingly, hierarchical multiscale schematic models are proposed. This insight into epoxidation on SIC of ENR strongly suggests that ENR with appropriate epoxidation degree is a promising candidate material for the fabrication of high-performance engineering rubber products.

Structure and stability of N–H complexes in single-crystal ZnO

Zinc oxide (ZnO) is semiconductor with a wide band gap of 3.4 eV. It continues to gain more attention not only for its versatile use in industry but also its potential for further application in electronics, optics, spintronics, and transparent circuits. Many of these applications require p-type ZnO. Nitrogen substituting for oxygen is a possible acceptor for such applications. In this paper, we report a study of nitrogen-hydrogen (N–H) complexes grown into single-crystal ZnO, using seeded chemical vapor transport in an ammonia ambient. An infrared (IR) absorption peak arising from N–H complexes was observed at 3150.6 cm−1 at liquid-helium temperatures. The assignment of this peak was confirmed by nitrogen and hydrogen isotope substitution. Polarized IR spectroscopy shows that the N–H dipole is oriented at an angle ∼114° to the c axis, in agreement with previous first-principles calculations. To probe the stability of the N–H complexes, samples were annealed in air, oxygen, and argon. Samples annealed in oxygen at 725 °C showed a significant increase in resistivity, due to outdiffusion of hydrogen and compensation by nitrogen acceptors.

Coordination of water molecules with Na+ cations in a beryl channel as determined by polarized IR spectroscopy

Subtle variations of frequencies in the infrared (IR) absorption spectra of beryl have been predicted based on the coordination between extra-framework cations and water molecules in two orientations (referred to as type I and type II) trapped within the channel. In this study, the polarized IR spectra of hydrated synthetic beryl and natural beryl were measured to clarify the relationships between the frequencies of the absorption bands and the coordination states of type II water. Na+ was assumed to be the predominant cation coordinated to type II water in our samples, as determined by chemical analyses. These measurements revealed a clear quantitative linear relationship in absorbance between bands at 3,602 and 1,619 and at 3,589 and 1,631 cm−1. On the basis of experimental and theoretical studies, we assigned these pairs of bands to the ν1 and ν2 modes of doubly coordinated type II H2O and to singly coordinated type II H2O, respectively. These assignments were supported by IR measurements of annealed natural beryl. We also conducted dehydration studies of natural beryl, in which two observed dehydration peaks, at 600 and 750°C, suggested the dehydration of type I and type II water, respectively.

Photocatalytic Decomposition of an Alkylammonium Cation in a Langmuir−Blodgett Film of a Titania Nanosheet

The formation of inorganic-organic hybrid films of a titania nanosheet and an amphiphilic alkylammonium cation has been investigated, and the photocatalytic decomposition of the alkylammonium cation in the film has been pursued. When a solution of the amphiphilic alkylammonium salt (octadecylammonium chloride: ODAH+ Cl-) was spread on an interface between the air and a titania nanosheet suspension, the negatively charged nanosheets were adsorbed onto the floating monolayer of ODAH+ to form a hybrid monolayer. The hybridization was confirmed by pi-A isotherm measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. Multilayered films were fabricated in a layer-by-layer way by transferring the hybrid monolayers onto glass plates. Areas per ODAH+ cation in the films were estimated from the infrared (IR) spectra of the films, but these areas were smaller than those estimated from the pi-A isotherm curves. The orientation of the alkyl chain of ODAH+ in the hybrid film was determined by means of polarized IR spectroscopy. The alkyl chains were tilted 41 +/- 1 degrees and 47 +/- 1 degrees from the surface normal for the films prepared from the 8 and 20 ppm (ppm = mg dm(-3)) suspensions, respectively. Together with X-ray diffraction data of the films, the structure of the hybrid film was discussed. When the films were illuminated with a UV light, the absorption intensities due to the alkyl chain of ODAH+ decreased exponentially, indicating the photocatalytic decomposition of ODAH+ by the titania nanosheets in the films. Deviation from the exponential trend in the decomposition rate was observed in the initial period for the hybrid films prepared from the suspensions at low concentrations. Interestingly, the layered structure of the hybrid film was disturbed significantly after the ODAH+ cations were decomposed.

The Structure of Hydrous Species in Nominally Anhydrous Minerals: Information from Polarized IR Spectroscopy

Hydrogen is a major constituent in a wide variety of minerals in the Earth’s crust. Usually H is bonded to oxygen forming H2O molecules or OH− groups. In rare cases, H3O+, H3O2− and H5O2+ units are also formed. The occurrence of NH4+, CHx, etc. in minerals will not be considered here. Hydrogen occurs stoichiometrically in hydrous compounds such as hydrates (e.g., gypsum), (oxy)hydroxides (e.g., goethite), and in many rock-forming silicates (e.g., micas), as well as in nonstoichiometric major amounts in microporous minerals such as zeolites and clay minerals, which are of considerable economic and ecologic importance. Hydrogen also occurs as a minor or trace constituent in minerals that by definition (and by their formulae) do not contain hydrogen at all, i.e., the so-called nominally anhydrous minerals (NAMs). NAMs include common rock-forming minerals in the Earth’s crust (e.g., quartz, feldspars) and upper mantle (e.g., olivine, pyroxene and garnet), but also high- P and high- T phases (e.g., wadsleyite, ringwoodite, and majorite garnet) stable in the mantle transition zone (410–660 km depth). The aim of the present chapter is to review the use of polarized infrared (IR) spectroscopy as it applies to detecting traces of hydrogen in minerals and to characterizing its speciation and structural environment in nominally anhydrous minerals. The basic theoretical background will be supplemented by a number of examples from recent research. It is important to note that many of the concepts described here for NAMs can also be applied to synthetic compounds of importance in the materials sciences. ### The importance of hydrous species in NAMs Hydrogen may be incorporated as defects in nominally anhydrous minerals of the Earth’s mantle. Due to the large volume of rock in the Earth’s mantle, even trace concentrations of H …

Polarized infrared spectroscopy of photo-oriented 2-fluoroethanol in solid argon: Mechanism of the mode-specific isomerization

Single photon infrared (IR) photoisomerization of 2-fluoroethanol isolated in solid argon creates selectively photooriented reactant and product distributions. The IR dichroism resulting from polarized excitation of each of six different bands in the CH stretching region, the OH stretching band, and the ν(OH)+τ(OH) combination band is reported. Each irradiation imparts a dichroism to the spectrum of both the G′g reactant and the Tt product isomers. Analysis of this dichroism shows that during isomerization the CH2F end of the molecule remains essentially stationary in the solid; the photoisomerization occurs primarily by internal rotation of the CH2O and OH groups. New vibrational mode assignments in the CH stretching region and a confirmation of a C2 pseudosymmetry in the Gg isomer are also derived from this analysis. These results demonstrate the general efficacy of this novel application of polarized IR spectroscopy.

ChemInform Abstract: POLARIZED INFRARED SPECTROSCOPY OF MATRIX‐ISOLATED DIMETHYLSILYLENE AND 1‐METHYLSILENE

Chemischer InformationsdienstVolume 15, Issue 19 Physical Organic Chemistry ChemInform Abstract: POLARIZED INFRARED SPECTROSCOPY OF MATRIX-ISOLATED DIMETHYLSILYLENE AND 1-METHYLSILENE C. A. ARRINGTON, C. A. ARRINGTONSearch for more papers by this authorK. A. KLINGENSMITH, K. A. KLINGENSMITHSearch for more papers by this authorR. WEST, R. WESTSearch for more papers by this authorJ. MICHL, J. MICHLSearch for more papers by this author C. A. ARRINGTON, C. A. ARRINGTONSearch for more papers by this authorK. A. KLINGENSMITH, K. A. KLINGENSMITHSearch for more papers by this authorR. WEST, R. WESTSearch for more papers by this authorJ. MICHL, J. MICHLSearch for more papers by this author First published: May 8, 1984 https://doi.org/10.1002/chin.198419046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue19May 8, 1984 RelatedInformation

Complexes of Polyethylene Oxide with Guanidine Hydrochloride and with Phenobarbital. Preliminary Structural Studies by Differential Scanning Calorimetry, Polarized Infrared Spectroscopy and X-Ray Fiber Photography

The complexes of polyethylene oxide (PEO) with guanidine hydrochloride and with phenobarbital were subjected to differential scanning calorimetry (DSC), polarized infrared (IR) spectroscopy and X-ray fiber photography, confirming the formations of the complexes and discussing the structures of PEO molecules in the complexes in comparison with PEO-urea complex or original samples of PEO. The formations of the complexes of PEO with urea, with guanidine hydrochloride and with phenobarbital were confirmed by DSC curves of physical mixtures of the respective original components. It may be concluded on the basis of the results by X-ray fiber photography that the three dimentional structure regarding the fiber identity period are different among ordinary PEO, PEO-guanidine hydrochloride complex and PEO-phenobarbital complex. The polarized IR spectroscopy informed that PEO molecule in PEO-guanidine hydrochloride complex may have a structure not so different from the 72 helix in the ordinary PEO. It was assumed that PEO molecule in PEO-phenobarbital complex is more distorted than that in PEO-guanidine hydrochloride complex in comparison with intact one, as the fiber identity period was considered to consist of one chemical unit.

Characterization of Uniaxially Drawn Polyethylene Terephthalate by Polarized Infrared Spectroscopy

Characterization of Uniaxially Drawn Polyethylene Terephthalate by Polarized Infrared Spectroscopy