Kazuaki Suehiro

Structural studies of the high temperature form of trans-1,4-polybutadiene crystal

Abstract It is known that trans-1,4-polybutadiene shows a crystal transformation at about 76°C. The crystal structure of the high-temperature form of trans-1,4-polybutadiene has been studied by X-ray diffraction. The chain conformation of the high-temperature form is similar to that of the low-temperature form. Above the crystal transformation temperature, the CH2─CH2 bond remains trans, but the internal rotation angles around two CH2─CH bonds are decreased to 80° and −80° from 109° and −109°, respectively. The molecular chains, however, are considered to be in a considerably distorted state due to torsional oscillation about the C─C bonds. It is shown that the X-ray diffraction pattern of the high-temperature form can be explained by taking into account the rotational motion of the chain segments around the molecular axes.

Physical Properties of Polyurethane Blend Dope-Coated Fabrics

We investigate the effects of the cross-sectional structure of a polyester-type polyurethane (pu)/polyvinylchloride (pvc) blend dope-coated nylon fabric on moisture permeability. The waterproof coating is applied by a one-sided wet-coagulation process. The blending of hydrophobic pvc to hydrophilic pu forms a three-layered cross-sectional structure—a pvc-rich micronetwork, a porous pu-rich layer, and the nylon fabric. As the blend ratio of pvc to pu increases, the moisture permeability (mp) and dew condensation (dc) of the coated fabrics improve. Compared to the pu homopolymer, the mp value of a pu/pvc blend in a weight ratio of 4:1 increases 1.18 times to 492 g/m2·h (JIS A-1 method) and 1.16 times to 815 g/m2·h (JIS B-1 method), but the dc value decreases one-fourth to 4.60 g/m2 · h. This gradient three-layered cross-sectional structure contributes to vapor transport properties.

Atomic force microscopic observation of a dialkylmelamine monolayer on barbituric acid

A monolayer of 2-amino-4,6-di(dodecylamino)-1,3,5-triazine 1 transferred from barbituric acid solution onto a mica plate is observed by atomic force microscopy (AFM) to show regularly arrayed terminal methyl groups of 1 as a result of hydrogen-bond networking.

Morphology and molecular orientation and structure of Langmuir–Blodgett films of chlorophyll a studied by atomic force microscopy and UV–VIS and IR spectroscopies

Atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–VIS absorption and IR spectroscopies have been used to investigate the morphological and molecular structure of Langmuir–Blodgett (LB) films of the title compound (Chl-a). The AFM and SEM measurements reveal that the surface of the LB films are very smooth and consist of rigid and condensed monolayers. The tilt angle of the chlorin plane in a six-monolayer LB film of Chl-a has been calculated to be 35° between the normal of the chlorin plane and the substrate normal and 44° between the dipping direction and projection of the normal of the chlorin plane, from measurements of its polarized UV–VIS spectra. Band frequencies in the 1750–1400 cm −1 region of the IR spectra of one-, six- and ten-monolayer (ML) LB films of Chl-a suggest that Chl-a exists in a five-coordinated monomer in the films, irrespective of the number of monolayers. Comparison of IR transmission and reflection–absorption spectra of 6 ML LB films of Chl-a indicates that the chlorin plane and the ester and keto CO groups are tilted considerably with respect to the surface normal. LB films of pheophytine a (Phe-a) have also been studied for comparison. Comparison of the UV–VIS and IR spectra of the LB films of Chl-a and Phe-a show that pheophytinization occurs little in the LB films of Chl-a. High-performance liquid chromatography (HPLC) examination has supported this conclusion. All the experiments carried out in the present study suggest that Chl-a molecules in the LB films are oriented in an orderly manner with face-to-face packing of the chlorin rings.

Classification for molecular aggregation structure of monolayers on the water surface

Abstract The melting temperature, T m , and the crystalline relaxation temperature, Tα c , of palmitic acid and dipalmitoyl phosphatidylcholine monolayers on the water surface were evaluated by combination of two kinds of measurements: first, the subphase temperature, T sp , dependence of the monolayer modulus based on the surface pressure-area (π- A ) isotherm and second, the T sp dependence of the electron diffraction, ED patterns of their monolayers. On the basis of their characteristic temperatures of the monolayers, the aggregation structure of the monolayers which were transferred onto a hydrophilic SiO substrate at various surface pressures and T sp s was investigated by means of transmission electron microscopy. The π- A isotherm for the fatty acid monolayer on the pure water surface represented the aggregating process of isolated domains grown right after spreading a solution on the pure water surface. The fatty acid monolayer on the pure water surface was classified into a crystalline monolayer ( T sp T m ) and an amorphous one ( T sp > T m ). The crystalline monolayer was further classified into two types; crystalline domains were aligned along their crystallographic axes owing to an induced sintering at the interfacial region among monolayer domains by surface compression ( T sp Tα c ), while not for T sp > Tα c . In the case of the phospholipid monolayer, the monolayer was classified into a compressing crystallized monolayer ( T sp T m ) and an amorphous one ( T sp > T m ). The compressing crystallized monolayer is a monolayer in which crystallization was gradually induced at plateau region on the π- A isotherm by compression. Electron diffraction studies of arachidic acid monolayers in different dissociated states of hydrophilic groups revealed that formation of the compressing crystallized monolayer was attributed to an electrostatic repulsion among ionic hydrophilic groups. It was concluded that the aggregation structure of monolayers on the water surface was systematically classified into ‘the crystalline monolayer’, ‘the amorphous monolayer’ and ‘the compressing crystallized monolayer’, with respect to thermal and chemical (intermolecular repulsive) factors.

Control of molecular ordering in guanidinium-functionalized monolayer by carboxylate template molecules

Electron diffraction studies of a [(dioctadecyl)carbamoylmethyl]guanidinium toluene-p-sulfonate (DG) monolayer reveal that the regularity of the molecular arrangement and the size of crystalline domains are controlled through binding of aqueous α,ω-dicarboxylates with various spacer lengths.

Nanotribology of behenic acid monolayer and its aggregation state

Abstract The tribological properties of behenic acid monolayers in CS and L 2 phases were investigated on the basis of scanning probe microscopic observations. The lateral (friction) force of the monolayers in CS and L 2 phases increased consistently with applied force. The increment in CS phase comes from an increase in contact area between a probe and the monolayer owing to elastic deformation, while that in L 2 phase does from not only increase in contact area owing to plastic deformation but wear of the monolayer. The lateral force of the monolayer in CS phase was independent of the scan velocity. On the other hand, the monolayer in L 2 phase exhibited the scan velocity dependence of the lateral force. The difference in tribological properties of the monolayer is attributable to the static mechanical properties of elasticity and plasticity which are governed by the molecular packing in monolayer.

Morphological and optical studies for a multi component monolayer of cyanine dye and fatty acid

Abstract The aggregation state of a mixed monolayer of cyanine dye and fatty acid during compression was investigated on the basis of surface pressure–area isotherm measurements, atomic force microscopic observations and spectroscopic measurements. The mixed monolayer was in a miscible state at all surface pressure values. The domains were formed in a matrix region by compression, which is probably due to ordering of molecular conformation. Compression at a surface pressure higher than the plateau pressure causes regularization of stacking of cyanine rings, resulting in the formation of J-aggregates.

Structural studies on molecular complexes of polyethers. V. effects of chain length and end groups on formation and melting of deoxycholic acid-polyether complexes

Abstract Complexation behavior of deoxycholic acid was studied for poly(oxy-ethylene), poly(propylene oxide), poly(tetrahydrofuran), and several poly(oxyethylene) derivatives with various chain lengths. The complexes were obtained for poly(oxyethylene) with an average molecular weight greater than 200 (average degree of polymerization n = 4). In spite of very short ethylene oxide chains, poly(oxyethylene) monostearate and poly(oxyethylene) mono-p-nonylphenyl ether with n = 2 formed the complexes. The unit cells of all complexes corresponded to the orthorhombic crystal which is most commonly observed for the complexes with low molecular weight compounds. Dimension a in the complexes of poly(propylene oxide) and poly(oxyethylene) mono-p-nonylphenyl ether with n = 2 and 5 was larger than those in other complexes, while b and c did not differ much. Most of the complexes exhibited an increase in the melting points with increasing length of the polymer chains, while the melting points of poly(oxyethylene) monos...

Effect of binding state between hydrophilic and hydrophobic portions on aggregation structure of monolayer

Abstract The effect of molecular structure of anionic (2CnPOH (n=12, 16)) amphiphiles with dialkyl chains that bind with the hydrophilic group only through ether bond and cationic (2CnN+2C (n=18, 22)) amphiphiles with dialkyl chains that directly bind with the hydrophilic group without a spacer on aggregation structure of amphiphile monolayers was investigated on the basis of π-A isotherm measurement and electron diffraction (ED) analysis. π-A Isotherms of the 2C12POH and 2C18N+2C monolayers exhibited a plateau region, whereas those of the 2C16POH and 2C22N+2C monolayers did a sharp rise in surface pressure with decreasing surface area. ED analysis revealed that 2C12POH, 2C18N+2C and 2C22N+2C monolayers were in an amorphous state even at higher surface pressures. On the other hand, the 2C16POH monolayer was in a crystalline hexagonal state in which the degree of molecular aggregation is low. Noncrystallization of the 2C12POH, 2C18N+2C and 2C22N+2C monolayers and the low degree of molecular aggregation of the 2C16POH monolayer may be attributed to the molecular aggregation by distantness between dialkyl chains in their parallel alignment due to binding between the hydrophilic and hydrophobic portions without or through only one spacer.