Fumitoshi Kaneko

Double-layered polytypic structure of the B form of octadecanoic acid, C18H36O2

Two bimolecular layers forming a double-layered polytypic structure exist in a repeating unit along the stacking direction. The acyl chain inclines toward the ab plane by 27 o and the direction of the inclination is turned by 180 o at every stacking of bimolecular layers. One bimolecular layer has essentially the same structure as that of the ordinary single-layered type of the E form

Crystalline complex of syndiotactic polystyrene with poly(ethylene glycol) dimethyl ethers.

It has been clarified that syndiotactic polystyrene (sPS) forms co-crystalline structures with polyethylene glycol dimethyl ethers (PEGDMEs) with molecular weights ranging from 178 to 1,000 g·mol(-1) through a guest exchange procedure assisted by a plasticizing agent. The PEGDME molecules are incorporated into the spaces between sPS polymer sheets consisting of (T(2)G(2))(2) helices. The results of X-ray diffraction and gravimetric measurements suggest that one or less molecules are included per unit cell for PEGDME with average molecular weight of 1,000 g·mol(-1), which indicates the possibility that longer polymeric molecules can be introduced into sPS lattices with multiple site occupation.

Complexation of Syndiotactic Polystyrene with 12‐Crown‐4

Solid-state complexation of syndiotactic polystyrene (sPS) with a crown ether compound, 1,4,7,10-tetraoxa-cyclododecane (12-crown-4), took place when a film of sPS/chloroform clathrate was subjected to a guest exchange procedure assisted with a plasticizing agent. The new guest 12-crown-4 molecules were incorporated into the crystalline region of the sPS film, without causing a large conformational change of host sPS helices. X-ray diffraction and thermogravimetric investigations showed that sPS/12-crown-4 complex had a clathrate complex structure which contained four 12-crown-4 molecules per unit cell. IR and Raman data suggested that 12-crown-4 took a C(i) -type conformation in the sPS complex phase.

Vibrational spectroscopic study on polymorphism of erucic acid and palmitoleic acid: γ1→α1 and γ→α reversible solid state phase transitions

Abstract The infrared and Raman spectra of four polymorphic phases (α, α1, γ and γ1) of erucic acid ( cis -13-docosenoic acid) and those of two polymorphic phases (α and γ) of palmitoleic acid ( cis -9-hexadecenoic acid) were investigated. The γ and γ1 phases of erucic acid were analyzed on the basis of crystal structures determined by us. There were large spectral differences between γ and γ1 phases, which could be ascribed to the differences in the conformation of cis -olefin groups and the subcell structure. Two types of reversible solid state phase transitions (γ→α and γ1→α1 transitions) were followed by the infrared and Raman spectra. It was concluded that the mechanism of the γ→α phase transition of erucic and palmitoleic acids is essentially the same as that of oleic acid previously reported by us [ J. Phys. Chem. 90 , 6371 (1986)], i.e. this phase transition is of order-disorder type accompanied by a conformational disordering at the methyl-terminal chain. Spectral changes on the γ1→α1 transition suggested that a similar structural change took place during this transition but there were large structural differences between α and α1.

X-ray and vibrational spectroscopic study on polymorphism of trielaidin

Abstract Polymorphism of trielaidin C 3 H 5 (OCOC 17 H 33 ) 3 , which is a typical monoacid trans-unsaturated TAG, has been studied with X-ray diffraction and vibrational (IR and Raman) spectroscopy. It is clarified that the β phase changes the conformation around trans-CC bond depending on its crystallization conditions. As for the internal rotation angle of CC bonds next to trans-CC bond, the β phase grown from a hexane solution shows a significant deviation from the standard skew or skew′ conformation, which was found in the β phase grown from a methanol–chloroform–toluene mixed solution. Contrary to the ordered molecular structure of the β phase, the α phase grown from a melt at high supercooling has a disordered structure at the glycerol backbone. The polymethylene chain between trans-CC bond and ester linkage is also conformationally disordered in the α phase.

Solid-state low temperature→middle temperature phase transition of linoleic acid studied by FTIR spectroscopy.

Temperature-dependent FTIR spectra of linoleic acid were measured over a temperature range of -80 to -30 °C to explore solid-state low-temperature (LT) → middle-temperature (MT) phase transition of linoleic acid. Band assignments were made mainly for the 900-760 cm(-1) region, where the bands due to cis-olefin groups ═C-H out-of-plane mode and the progression bands due to CH(2) rocking-CH(2) twisting modes are expected to appear. The structural evolutions during the LT → MT phase transition of linoleic acid were investigated by analyzing the progression bands with the simple-coupled oscillator model to elucidate the features of acyl chain influenced with two cis-C═C bonds linked through one CH(2) group. Structure changes in the LT → MT transition of linoleic acid were compared with those in the γ → α transition of oleic acid. It has been found that the former is rather localized around the cis-diene group, while the latter occurs in the larger portion between the cis-olefin group to the methyl end. It is also suggested that the conformational change in the cis-olefin group on the LT → MT transition is on a lesser scale than that on the γ → α transition.

Polarized infrared attenuated total reflection spectroscopy for three‐dimensional structural analysis on long‐chain compounds

Two simple techniques using single‐crystal specimens in polarized infrared attenuated total reflection (ATR) spectroscopy were developed for structural studies of molecular crystals, in particular of long‐chain compounds. The first technique relates to a rotatory change of sample setting around the normal of the sampling plane of an internal reflection element (IRE) in the p‐polarized ATR measurement. This is a simple method to distinguish whether a transition moment is parallel to a certain crystal face. The inclination manner of hydrocarbon chains constructing an orthorhombic polyethylene subcell can be easily determined. Another technique relates to the employment of intermediate polarizations between p and s settings of incident infrared radiation, which allows three‐dimensional structural analysis. The evanescent electric field is estimated for a simple model system. Linearly polarized incident radiation generates an elliptical electric field in a specimen. By combining a rotatory change of sample se...

Complexation of Syndiotactic Polystyrene with Crown Ethers: 12-Crown-4, 15-Crown-5 and 18-Crown-6

Solid-state complexation of syndiotactic polystyrene (sPS) with three crown ether compounds, 1,4,7,10-tetraoxacyclododecane (12-crown-4, 12c4), 1, 4, 7, 10, 13-pentaoxacyclopentadecane (15-crown-5, 15c5), and 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane (18-crown-6, 18c6) took place when a film of sPS/chloroform clathrate was subjected to a guest exchange procedure assisted by a plasticizing agent. The new guest molecules were incorporated into the crystalline region of the sPS film, without causing a large conformational change of the host sPS helices. X-ray diffraction and thermogravimetric measurements showed that sPS forms co-crystalline structures with 12c4 and 15c5 presented four guest molecules per unit cell, whereas little information about the lattice dimension was obtained for sPS/18c6 because no X-ray reflections appeared in the low-angle region. IR spectroscopic and X-ray diffraction investigation suggested that the (010) uniplanar orientation of the starting sPS/chloroform clathrate was preserved during the course of guest exchange. The comparison of IR spectra between a crown ether in the liquid and crystalline states and its corresponding sPS complex showed that the crown ether incorporated into the host sPS lattice was in a conformational state similar to its liquid state, which was a mixture of two or more different conformers. It was suggested from IR and Raman spectral data that sPS/12c4 complex contained a high percentage of the Ci type conformer found in crystalline 12c4. It was inferred that the larger the molecular ring, the higher its flexibility, which leads to the lower conformational correlation of crown ether between the crystalline state and the sPS complex.

Development of a micro-FT-IR system for three-dimensional structural studies

Abstract The oblique transmission method is a simple and effective technique of infrared (IR) spectroscopy for obtaining three-dimensional structural information on solid states. In order to apply this technique to tiny specimens, an IR microscope for oblique transmission measurement was developed. A newly designed optical system enabled oblique irradiation of high irradiance from any direction of incidence. A band pass filter was introduced into this spectrometer to improve the spectrum in the region of low irradiance. In the trial measurement using a single crystal of stearic acid, the obtained spectra were well consistent with its crystal structure.

MOLECULAR AMD CRYSTAL STRUCTURES OF LIPIDS AND RELATED COMPOUNDS

Abstract Molecular-level structures of lipids and related organic long-chain compounds were investigated by means of vibrational spectroscopic and X-ray diffraction methods. Various spectroscopic techniques applicable to structural studies of lipid systems were developed. Various types of solid-state phase transformations were found in even- and odd-numbered saturated fatty acids and their molecular mechanisms were considered. Crystal structures of some modifications of a series of cis-mono-unsaturated fatty acids were determined by the three-dimensional X-ray analysis and new types of molecular conformation as well as of subcell arrangement of the cis-mono-unsaturated acyl chains were found. An order-disorder type phase transformation accompanied with a partial melting at the interface of the molecular layers was found in some modifications of cis-mono-unsaturated fatty acids. Molecular conformations and crystal structures of the polymorphs of methyl oleate and triglycerides containing an oleoyl chain at...