Two-Dimensional Correlation Analysis of Polyimide Films Using Attenuated Total Reflection-Based Dynamic Compression Modulation Step-Scan Fourier Transform Infrared Spectroscopy

2007 ◽  
Vol 61 (8) ◽  
pp. 873-881 ◽  
Author(s):  
Yuji Nishikawa ◽  
Tatsuhiko Nakano ◽  
Isao Noda
Keyword(s):  
Dynamic Response ◽  
Intermolecular Interactions ◽  
Density Functional ◽  
Sequential Analysis ◽  
Dynamic Compression ◽  
Correlation Study ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Two Dimensional ◽  
Spectral Simulation

Attenuated total reflection (ATR)-based dynamic compression modulation two-dimensional (2D) correlation study of poly(p-phenylene biphenyltetracarboximide) film is carried out in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of imide I (C=O stretching mode) show three distinct correlation peaks located around 1777, 1725, and 1708 cm−1. The band at 1708 cm−1 is the lower wavenumber shift component of 1777 or 1735 cm−1 peaks and is attributed to the results from intermolecular interactions, according to the DFT analysis. The 1708 cm−1 band also shows the largest dynamic response, suggesting that these intermolecular interactions may enhance the dynamic response. The dynamic 2D IR correlation spectra in the region of imide II (C–N–C axial stretching mode) vibrations also show three correlation peaks located around 1335, 1355, and 1370 cm−1, although the imide II band is shown to consist substantially of one component by the DFT analysis. These multiple peaks may be attributed to the compression-induced wavenumber shift of the band in the backbone structures. The sequential analysis of 2D correlation data show that, upon applying the dynamic compression, the response of the backbone regions (imide II) occurs first, followed by that of the side-chain regions (imide I, C=O).

Two-Dimensional Attenuated Total Reflection Infrared and Near-Infrared Correlation Study of the Structure of Butyl Alcohol/Water Mixtures

2007 ◽  
Vol 61 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Dagmara Wojtków ◽  
Mirosław A. Czarnecki
Keyword(s):  
Near Infrared ◽  
Correlation Study ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Experimental Conditions ◽  
Oh Groups ◽  
Alcohol Water ◽  
Anharmonicity Constants

The effect of temperature on attenuated total reflection infrared (ATR-IR) and near-infrared (NIR) transmission spectra of pure butan-1-ol, butan-2-ol, 2-methyl-propan-1-ol, 2-methyl-propan-2-ol, and mixtures with a small water content (XH2O ≤ 0.1) have been examined. The spectra were analyzed using a two-dimensional (2D) correlation approach. Two kinds of correlation analysis were performed: IR–IR and NIR–NIR homo-correlation and IR–NIR hetero-correlation. Our results reveal that the addition of small to moderate amounts of water does not destroy the structure of alcohol. The presence of water stabilizes the structure of alcohols and this effect is more evident for sec-butanol and tert-butanol. The ATR-IR spectra provide information on the most associated species, whereas absorption of the smaller associates and the free OH group is hardly seen. On the contrary, in the NIR spectra the absorption of the free OH groups dominates. The ability of resolution enhancement in the hetero-correlation asynchronous spectra is reduced as compared to that in the homo-correlation spectra. On the other hand, peaks may appear in the hetero-correlation synchronous spectra that are not observed in the homo-correlation contour plots. The positions of the synchronous peaks were used for evaluation of anharmonicity constants. These values for the free OH group do not depend on the experimental conditions. In contrast, the anharmonicity constants for the bonded OH groups determined from the spectra of pure alcohols may significantly differ from those obtained from diluted solutions.

Polymorphism in two biologically active dihydropyrimidinium hydrochloride derivatives: quantitative inputs towards the energetics associated with crystal packing

2014 ◽  
Vol 70 (4) ◽  
pp. 681-696 ◽  
Author(s):  
Piyush Panini ◽  
K. N. Venugopala ◽  
Bharti Odhav ◽  
Deepak Chopra
Keyword(s):  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Density Functional ◽  
Crystal Packing ◽  
Lattice Energy ◽  
Biologically Active ◽  
Two Dimensional ◽  
Energy Calculations ◽  
X Ray ◽  
Fingerprint Plots

A new polymorph belonging to the tetrahydropyrimidinium class of compounds, namely 6-(4-chlorophenyl)-5-(methoxycarbonyl)-4-methyl-2-(3-(trifluoromethylthio)phenylamino)-3,6-dihydropyrimidin-1-ium chloride, and a hydrate of 2-(3-bromophenylamino)-6-(4-chlorophenyl)-5-(methoxycarbonyl)-4-methyl-3,6-dihydropyrimidin-1-ium chloride, have been isolated and characterized using single-crystal X-ray diffraction (XRD). A detailed comprehensive analysis of the crystal packing in terms of the associated intermolecular interactions and a quantification of their interaction energies have been performed for both forms of the two different organic salts (AandB) using X-ray crystallography and computational methods such as density functional theory (DFT) quantum mechanical calculations, PIXEL lattice-energy calculations (with decomposition of total lattice energy into the Coulombic, polarization, dispersion and repulsion contribution), the calculation of the Madelung constant (the EUGEN method), Hirshfeld and two-dimensional fingerprint plots. The presence of ionic [N—H]+...Cl−and [C—H]+...Cl−hydrogen bonds mainly stabilizes the crystal packing in both formsAandB, while in the case ofB·H2O [N—H]+...Owaterand Owater—H...Cl−hydrogen bonds along with [N—H]+...Cl−and [C—H]+...Cl−provide stability to the crystal packing. The lattice-energy calculations from both PIXEL and EUGEN methods revealed that in the case ofA, form (I) (monoclinic) is more stable whereas forBit is the anhydrous form that is more stable. The analysis of the `Madelung mode' of crystal packing of two forms ofAandBand its hydrates suggest that differences exist in the position of the charged ions/atoms in the organic solid state. TheR/E(distance–energy) plots for all the crystal structures show that the molecular pairs in their crystal packing are connected with either highly stabilizing (due to the presence of organicR+and Cl−) or highly destabilizing Coulombic contacts. The difference in crystal packing and associated intermolecular interactions between polymorphs (in the case ofA) or the hydrates (in the case ofB) have been clearly elucidated by the analysis of Hirshfeld surfaces and two-dimensional fingerprint plots. The relative contributions of the various interactions to the Hirshfeld surface for the cationic (dihydropyrimidinium) part and anionic (chloride ion) part for the two forms ofAandBand its hydrate were observed to be different.

Rheo-Optical Study of Polymers by Using Time-Resolved Soft-Pulse Compression Attenuated Total Reflection Step-Scan Fourier Transform Infrared Spectroscopy

2009 ◽  
Vol 63 (11) ◽  
pp. 1204-1210 ◽  
Author(s):  
Yuji Nishikawa ◽  
Tatsuhiko Nakano ◽  
Isao Noda
Keyword(s):  
Fourier Transform ◽  
Pulse Compression ◽  
Dynamic Compression ◽  
Pulse Frequency ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Type I ◽  
Type Ii ◽  
Time Resolved ◽  
2D Ir

A time-resolved soft-pulse dynamic compression attenuated total reflection (ATR) step-scan Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of polyethyleneterephthalate (PET) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx). Resonance features were observed in the dynamic compression ATR spectrum of PHBHx with 625 Hz soft-pulse frequency. In contrast, the dynamic compression ATR spectrum of PET showed no resonance features. The resonance feature of PHBHx was found at 1723 cm−1, which corresponds to the structural or morphological reorganization of a less ordered (Type II) crystalline form under compressive perturbation. The time-resolved evolution of infrared (IR) spectra was effectively analyzed by conventional generalized two-dimensional (2D) correlation analysis. The 2D-IR results indicate that the dynamic response of the well-ordered Type I crystalline state (1289 and 1261 cm−1) is faster than that of the Type II (1723, 1277, and 1228 cm−1). The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, and copolymers, and semicrystalline polymers.

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