Infrared intensity in dielectric media by an electrostatic model

A change in an infrared intensity in dielectric media is treated by an electrostatic model. The basic model is originally formalized for a dipolar liquid. The model is satisfactorily applied to the infrared intensity of the C-H stretching of chloroform, which changes 22 times large in the liquid state at -43 degrees C as in the gaseous state. A change in the infrared intensity in lithium ammonium tartrate, where a ferroelectric phase transition takes place, is analyzed on the basis of a local polarization above T(c) or a spontaneous polarization below T(c), deducing important quantities on a phase transition. A difference in the infrared intensity of the C-Br stretching of 1,10-dibromodecane between the urea clathrate and the crystalline state is analyzed by evaluating electric fields due to bond moments and oscillating dipoles. These analyses confirm the mechanism of the change in the absolute infrared intensity, which originates from an electrostatic interaction with an electric field applied to a molecule or a functional group closely related to a normal mode.     

An investigation on a broad infrared band with the maximum at approximately 1300 cm(-1) in magnesia cement,phase 3

In magnesia cement, phase 3, a broad and strong infrared band was observed with the maximum at approximately 1300 and 1050 cm(-1) in the H and D systems, respectively. To clarify the origin of the 1300 cm(-1) band the temperature dependency of the infrared spectra of the H system was observed and the spectra analyzed on the basis of a strong vibrational coupling of the OH stretching with lattice modes. The fitting was quite well, giving rise to the origin of the 1300 cm(-1) band of the OH stretching.     

Infrared spectra of 1 -monopalmitin- or 1-monostearin-water systems in the gel phase

The infrared spectra of 1-monopalmitin- or 1-monostearin-water systems in the gel phase were observed at room temperature. In both systems the infrared intensities of the bands parallel and perpendicular to the paraffin chain are relatively reduced and enhanced, respectively, on going from the crystalline phase to the gel phase. These spectral changes are explained in terms of the interaction among oscillating dipoles, which is sensitive to the morphology change from the three-dimensional crystalline phase to the two-dimensional lipid bilayers. The non-planar lipid bilayers are proposed for the gel phase in monopalmitin-water systems with x > or = 35 (x: wt.% water).     

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid-state 17O NMR spectroscopy and ab initio MO calculations

The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated.     

Non-classical control of solid-state aggregation-induced enhanced circularly polarized luminescence in chiral perylene diimides

Organic fluorescent molecules are gaining importance because of their potential applications in many devices. Optically active N,N′-bis((1R)-1-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-1-BNP] and N,N′-bis((1R)-2-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-2-BNP] and their antipode, [(S,S)-1-BNP and (S,S)-2-BNP], emit aggregation-induced enhanced (AIEnh) circularly polarized luminescence (CPL) on both a solid organic polymer film (poly(methyl methacrylate)) and solid inorganic KBr pellet. An opposite chirality is essential for generating CPL of inverted sign. However, a pair of enantiomeric organic molecules may not always be easy to prepare. Interestingly, the chiral perylene fluorophores synthesized in this study can emit both positive and negative AIEnh-CPL in the solid state, depending on their position on the naphthylene groups. In addition, no CPL was observed in these compounds from their dilute solutions.     

Crystal structure of 1,10-dibromodecane and its infrared intensity in a urea clathrate and in the crystal

The crystal structure of 1,10-dibromodecane belongs to the monoclinic system and the space group is P2(1)/c with lattice dimensions of a = 5.4574(3) A, b = 5.2814(4) A, c = 21.088(1) A and beta = 92.897(2) degrees and zeta = 2. Infrared spectra of 1,10-dibromodecane in a urea clathrate and in the crystal were observed to investigate the effect of molecular interaction on infrared intensity. The infrared intensity of the CH(2) waggings in the crystalline state is 1.5-1.9 times stronger on the relative basis than that in a urea clathrate, whereas those of CH(2) stretching, CH(2) rocking and CH(2) bending are almost the same in both states. The former enhancement is explained in terms of increase in the bond moment of the C(alpha)H(2) group on the basis of crystal structure and the electrostatic model. The relative intensity of two CH(2) asymmetric stretching changes between the two states. This is also analyzed by the use of the electrostatic model.     

Infrared intensity of 1-monolaurin-water systems in the gel phase

The infrared spectra of 1-monolaurin-water systems, where KSCN is added as the intensity standard, were observed and the infrared intensity of the bands due to acyl groups measured relatively to that of the CN stretching. The infrared intensities of the bands parallel and perpendicular to the paraffin chains decrease and increase, respectively, on going from the crystalline 1 phase to the gel phase, confirming that these intensity changes result from the long-range interaction among oscillating dipoles. The infrared spectra with no CH2 rocking and the splitting of the CH2 rocking are also discussed with the same interaction model.     

Infrared intensity and morphology of l-monolaurin-water systems

The infrared spectra for some metastable states in 1-monolaurin water systems were observed at room temperature, where the relative intensity of bands due to paraffin chains changed considerably, especially in the CH2 rockings, which disappear in some cases. It is considered that the spectral changes result from the morphology change on going from the crystal to the liquid crystal, smectic B phase, so-called gel phase, which consists of the lipid bilayers with ordered paraffin chains alternating with water layers. The model for explaining the intensity change is proposed on the basis of the interaction among oscillating dipoles.     

Synthesis and characterization of postsulfonated poly(arylene ether sulfone) diblock copolymers for proton exchange membranes

Sulfonated poly(arylene ether sulfone) diblock copolymers were studied through the postsulfonation process. Two kinds of hydrophobic oligomers with a molecular weight of 20 kDa were prepared in advance as block sequences and then coupled together to obtain diblock copolymers. One oligomer was synthesized from bis(4‐hydroxyphenyl) sulfone (BHPS) and 4,4′‐difluorodiphenyl sulfone (DFDPS), which was thought to be incapable of postsulfonation. The other oligomer was synthesized from hydroquinone (HQ) and 4,4′‐dichlorodiphenyl sulfone (DCDPS), which successfully proceeded to a hydrophilic sequence as a result of sulfonation onto the HQ moiety after the coupling reaction. Consequently, a diblock copolymer with high molecular weight was obtained; although its intrinsic viscosity was too low to form a tough membrane because of its high rigidity and high crystallinity. Therefore, the use of decafluorobiphenyl (10F) as a termination reagent was investigated with the aim of achieving higher coupling reactivity and a kinky property. As a result, a sulfonated diblock copolymer was successfully obtained with sufficient molecular weight and intrinsic viscosity to form the membrane, as well as with adequate thermal properties. It was observed that proton conductivity, water uptake, and the water diffusion coefficient increased with higher ion exchange capacity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 700–712, 2009     

Vibrational study on structural transitions of potassium pelargonate CH3(CH2)7CO2K

Anhydrous potassium pelargonate (KC9) undergoes four thermal transitions from room temperature to 450 degrees C. A normal mode analysis was made for the molecule in phase I at room temperature and the molecule was considered to have an all-trains conformation. With increasing temperature, partial melting of the alkyl chains occurred in phase II and complete melting was observed in phase III, as confirmed by vibrational spectra. In addition, orientational disorder of the carboxylate groups was suggested in phase II. This transition behavior of potassium pelargonate was compared with the behavior of nonane and pelargonic acid.