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Fatty acids such as oleic and stearic acids having a long hydrocarbon chain are known to exist as dimers in their melt and even in a non-polar solvent. In their melt the dimers arrange longitudinally and alternately to form clusters which resemble a smectic liquid crystal. The clusters determine the liquid properties of the fatty acids such as density, viscosity and fluidity. Then, do the dimers of fatty acid having a moderate-length hydrocarbon chain construct such the clusters? In the present study the dynamic molecular behavior and assembly structure of octanoic acid in its melt and also in CCl4 solution have been investigated by the X-ray diffraction, near infrared spectroscopy, 1H-NMR chemical shift, self-diffusion coefficient and 13C-NMR spin-lattice relaxation time measurements. From these results it has been revealed that the clusters of octanoic acid exist in its melt and also in CCl4 and that the clusters in the melt disintegrate with an increase in temperature. The dissociation profile of dimers of octanoic acid into monomers in CCl4 also has been clarified.

We have found for the first time the reentrant lamellar/onion (lamellar-onion-lamellar) transition with varying temperature under constant shear rate by using simultaneous measurements of shear stress and small-angle X-ray scattering (Rheo-SAXS) for a nonionic surfactant (C(14)E(5))/water system, which exhibits the lamellar phase in a wide temperature range from 15-75 °C. The onion state exists in a closed region in the temperature-concentration diagram at a constant shear rate. Temperature dependence of the lamellar repeat distance (d) at rest has also been measured at several concentrations. It is shown that the increase of d with increasing temperature is necessary for the existence of the lower transition. We have investigated the change in the lamellar orientation in the lamellar-to-onion and onion-to-lamellar transition processes near the upper and lower transition temperatures. For all four kinds of transition processes, the following change in the lamellar orientation is observed; lamellar state (oriented to the velocity gradient direction) ↔ further enhancement of the orientation to the velocity gradient direction ↔ enhancement of the orientation to the neutral direction ↔ onion state.

Ordinary fatty acids such as oleic, elaidic and stearic acids exist as their hydrogen-bonded dimers in their liquids and in non-polar solvents. Infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy have revealed that semi-fluorinated (SF) acids containing a perfluorooctyl group (C₈F₁₇) as a terminal segment exist also as hydrogen-bonded dimers, which are the units of inter- and intramolecular movements in their liquids and CCl₄. The dynamic molecular properties, such as self-diffusion coefficients and intramolecular movements of SF-oleic, SF-elaidic, and SF-stearic acids were compared with those of corresponding ordinary fatty acids (H-acids). From the high equilibrium spreading pressures (ESPs) for SF-acids compared with those for their corresponding H-acids, it was expected that the inter-acyl chain interaction is weaker for the SF-acid than for the H-acid: the SF-fatty acids should have higher molecular mobility than the corresponding ordinary H-acids in the liquid state. However, the self-diffusion coefficients obtained for SF-acids were smaller than those for the corresponding H-acids; the apparent activation energies for the self-diffusion process (translational movement) of SF-acids were larger than those for the corresponding H-acids. Namely, the motion of SF-acid molecules in a liquid phase is rather restricted compared with H-acid in spite of lower inter-acyl chain interaction of SF-acid. This unexpected result suggests that the molecular motion of SF-acid in a liquid phase is not directly governed by inter-acyl interaction, but may be interpreted as a reptation movement of an acid molecule, which is related to intramolecular movement. In fact, low intramolecular movements for SF-acid were confirmed by ¹³C-NMR T₁ measurements.

This paper discusses the molecular conformations and the liquid structures of triacylglycerols (TGs) and fatty acids in their melts. Three models for liquid state ordering have been proposed for TG melts to date: the smectic liquid crystal model, the nematic liquid crystal model, and the discotic model. To completely resolve the liquid structure of TGs, further research is required. However, some information on the molecular level has been obtained for fatty acids that are relatively simple compounds. The combination of various spectroscopic and thermodynamic measurements revealed that the hydrogen-bonded dimers of fatty acids are units of intermolecular and intramolecular movements in the liquids and in non-polar solvents. The dimers that construct the clusters resemble the smectic liquid crystal and determine the physicochemical properties of the liquid of the fatty acid. Cholesterol stabilizes the clusters, while ethanol destroys them. Self-diffusion and neutron diffraction measurements revealed that two kinds of fatty acids exist in their binary liquid mixture exist as the homodimers composed of same species.

The self-association of -methylacetamide (NMA), which is one of the most simple compound having a peptide bond, in various solvents such as carbon tetrachloride (CCl4), chloroform, dichloromethane, and acetonitrile was studied through the near-infrared (NIR) spectroscopic observation at various temperatures and concentrations. An analysis assuming a successive association processes for the NMA molecules was applied to the sharp 1470-nm band (the first-overtone band of NH stretching vibration mode attributed to free NH group of NMA monomer and partly to the free, terminal NH group of NMA aggregate); the mean association number for NMA in CCl4 increases with increasing concentration and decreases with increasing temperature. Comparisons of the association number of NMA in various solvents indicate that the degree of association is in the following order: chloroform ≒ dichloromethane acetonitrile. Interestingly, the association number of NMA in CCl4 is thought to be larger than that in its pure liquid.

The temperature dependence of the structure and dynamic properties of oleic acid γ and α phases has been studied by FTIR spectroscopy. By observing the characteristic bands due to the cis-olefin, c...

Phase behaviors of the binary mixtures composed of ethylene carbonate (EC) and aliphatic alcohols, ω-phenyl alcohols, and alkylbenzenes were investigated. In addition, heat of solution of EC into these organic solvents was measured. The EC/methanol and EC/ethanol systems gave homogeneous solution at the temperature above their liquidus lines, while the mixtures of EC and alcohols with longer alkyl chain showed a miscibility gap in a liquid phase and provided the monotectic-type phase diagram. The liquid–liquid phase separation region expanded with the increase in the alkyl chain length. A similar phase behavior was also observed for the mixtures of EC and alkylbenzenes. On the other hand, the EC mixtures with ω-phenyl alcohols showed no miscibility gap in a liquid phase at least up to 4-phenylbutan-1-ol which has C4 alkyl chain intervening between phenyl and hydroxyl groups. This result demonstrates that both of the hydroxyl and phenyl groups act to facilitate the mixing of aliphatic compounds with EC. The phase behavior of these EC mixtures was analyzed applying the modified regular solution model in which the pair interaction energy was regarded as free energy. The model calculation with the use of heat of solution of EC at infinite dilution as the pair interaction enthalpy reproduced well both of the experimentally obtained liquidus line and mutual solubility curve as well as monotectic point.

The dynamic behavior of liquid oleic and linoleic acids in ethanol has been explored by applying attenuated total reflectance (ATR) infrared (IR) spectroscopy. Fine spectral features are obtained with two-dimensional (2D) correlation spectroscopy. When the solution mixture was exposed to the open atmosphere, the complexes between the carboxylic acids and ethanol begin to dissociate and it starts the formation of dimers of the carboxylic acids. As the evaporation proceeds, the dimeric molecules undergo the self-assembling to form tightly packed quasi-smectic liquid crystal structure. The hetero-system 2D correlation spectra developed with two sets of time-dependent ATR–IR spectra of oleic and linoleic acids reveal that linoleic acid molecules aggregate faster as compared with oleic acid ones during the self-assembling mostly due to the difference in the number of the C C bonds.

A practical index to estimate physically or chemically meaningful convergence in self-modeling curve resolution (SMCR) is proposed. In SMCR, solutions for concentration profiles and pure component spectra are given by a sequential rotation of matrices, called alternating least square (ALS). A convergence guided by an error criterion based on the sum of squared residuals between original and reconstructed spectra brings a mathematically valid solution. However, a serious problem sometimes arises because such an error criterion can bring up an undesirable result which only satisfies purely mathematical constraint without realistic chemical or physical considerations. This situation can be seen as a kind of overfitting of a model to the original spectra. As a possible solution, an alternative error criterion based on global phase angle, which enables one to obtain chemically or physically meaningful convergence in ALS, is used. In the present study, a practical use of this error criterion is demonstrated with time-dependent IR spectra of mixture solution of oleic acid and ethanol. The result clearly reveals the optimal number of the iteration in ALS that provides a realistic model. This method may be a powerful tool of SMCR to balance both mathematically and physically meaningful information.

A quantitative index to reveal physical interactions between ethanol and carboxylic acids are derived by using self-modeling curve resolution (SMCR) kernel. SMCR is a family of chemometrics technique to deconvolute multi-component spectra into individual chemical species. By combining two-dimensional (2D) correlation spectroscopy and SMCR, a quantitative index called SMCR kernel is obtained to estimate the degree of synchronous and asynchronous correlations among chemical species. Relative relationships between ethanol and several carboxylic acids are derived from a series of SMCR kernel matrices of the binary mixture solutions. SMCR is applied to near-infrared (NIR) spectra of the mixture solutions, and several asynchronous kernel matrices are obtained. Comparison of the asynchronous kernel matrices reveals quantitative measure among hydrogen bonding of carboxylic acids strongly related to their molecular structures.

Comparison of the hydrogen bonding of racemic RS-1-monostearoylglycerol and chiral S-1-monostearoylglycerol in benzene was carried out through the NMR measurement. In addition, the concentration dependence of a chirality of S-1-monostearoylglycerol in hexane was studied though UV and circular dichroism (CD) measurements. The chemical shifts of OH protons of the S- and RS-1- monostearoylglycerols indicated that the hydrogen bonding between the R- and S-form molecules of RS-1-monostearoylglycerol is stronger than that between the S- and S-form molecules of S-1-monostearoylglycerol in the low concentration region and that the difference in the strength of hydrogen-bonding between them becomes small in the high concentration region. The chirality of the S-1-monostearoyglycerol in hexane decreased with increasing its concentration. This suggests that the association of chiral S-1-monoacylglycerol arising from its increasing concentration reduces the chirality of S-1-monostearoylglycerol.

Particle swarm optimization (PSO) combined with alternating least squares (ALS) is introduced to self-modeling curve resolution (SMCR) in this study for effective initial estimate. The proposed method aims to search concentration profiles or pure spectra which give the best resolution result by PSO. SMCR sometimes yields insufficient resolution results by getting trapped in a local minimum with poor initial estimates. The proposed method enables to reduce an undesirable effect of the local minimum in SMCR due to the advantages of PSO. Moreover, a new criterion based on global phase angle is also proposed for more effective performance of SMCR. It takes full advantage of data structure, that is to say, a sequential change with respect to a perturbation can be considered in SMCR with the criterion. To demonstrate its potential, SMCR by PSO is applied to concentration-dependent near-infrared (NIR) spectra of mixture solutions of oleic acid (OA) and ethanol. Its curve resolution performances are compared with SMCR with evolving factor analysis (EFA). The results show that SMCR by PSO yields significantly better curve resolution performances than those by EFA. It is revealed that SMCR by PSO is less sensitive to a local minimum in SMCR and it can be a new effective tool for curve resolution analysis.

It has been empirically known that cholesterol largely increases the viscosity of oleic acid. To clarify the mechanism of the effect of cholesterol on the intermolecular and the intramolecular (segmental) movements of oleic acid in the liquid state, we measured density, viscosity, IR, 1H NMR chemical shift, self-diffusion coefficient, and 13C NMR spin-lattice relaxation time for the liquid samples of oleic acid containing a small amount of cholesterol. Furthermore, the above measurements were also carried out for the samples of oleic acid containing a small amount of cholestanol, cholestane, cholesteryl oleate, ethanol, or benzene. Cholesterol, possessing one OH group and one double bond in its molecular structure, largely increased the viscosity and reduced the self-diffusion and the intramolecular movement of oleic acid. Cholestanol, possessing one OH group but not a double bond, and cholesteryl oleate, not possessing an OH group, also reduced the self-diffusion and the intramolecular movement; cholestane, not possessing an OH group, slightly reduced the self-diffusion and the intramolecular movements. In contrast with these sterols, ethanol and benzene reduced the viscosity and increased the self-diffusion and the intramolecular movements. In addition, cholesterol and ethanol, both having one OH group, promoted the upfield shift of the 1H NMR signal of the carboxyl group of oleic acid; IR difference spectra for the cholesterol/oleic acid system quite resemble those for the ethanol/oleic acid system. These results suggest that oleic acid makes a complex with cholesterol as well as with ethanol. On the basis of the formation of the complex, we have revealed the role and the functional mechanism of cholesterol to the intermolecular and the intramolecular movements of oleic acid in the liquid state.

Absorption and fluorescence spectra, fluorescence lifetimes, and steady-state and time-resolved fluorescence anisotropies were measured for 4-methyl-4'-cynanobiphenyl (1CB) and 4-hexyl-4'-cynanobiphenyl (6CB) in glycerol at various temperatures. The energies and intensities of the absorption and emission spectra for 1CB and 6CB were almost equally observed, and the fluorescence lifetimes around 1.0 ns were also almost equally obtained and did not depend on temperature. However, the time-resolved fluorescence anisotropies measured in glycerol solution indicated that the molecules of 1CB rotate more rapidly than those of 6CB: the rigid-sphere radii for 1CB and 6CB obtained by using the pulsed exciting light were evaluated as 1.3x10(-10) m (1CB) and 1.8 x 10(-10) m (6CB) in the low temperature region (2-10 degrees C), whereas those evaluated in the high temperature regions (20-60 degrees C for 1CB and 30-60 for 6CB) were 2.7 x 10(-10) m (1CB) and 3.6 x 10(-10) m (6CB). These radii evaluated in the high temperature region were in good agreement with those obtained by using steady-state exciting light, 2.9 x 10(-10) m (1CB) and 3.4x10(-10) m (6CB). It is noted that the increase of radius was observed across an intermediate temperature region (10-30 degrees C for 1CB or 10-40 degrees C for 6CB), and was more remarkable for 6CB than for 1CB. This implies that the movements of hexyl-chain are much more enhanced at high temperature, and are effectively reflected to the increase in radius of rotational diffusion. The changing phenomenon of movements of peripheral alkyl-chain in liquid-crystal molecules is important for the phase transition between liquid crystal and isotropic liquid phases: the changing to less vigorous movements of the alkyl-chain in 6CB is thought enough to contribute to the liquid-crystal formation of 6CB molecule.

Dimer structure and liquid structure of fatty acids in their binary mixtures such as decanoic acid (DA)/octadecanoic acid (SA) and DA/dodecanoic acid (LA) were studied through the measurements of self-diffusion coefficient (D), differential scanning calorimetry (DSC), density and viscosity. The obtained phase diagrams showed that DA and SA form a eutectic in the solid state but partly a solid solution in the SA-rich region; DA and LA form an incongruent-melting compound which forms a eutectic with DA. In the liquid mixture of DA and SA, the D of DA is larger than that of SA over the entire range of compositions and tends to approach the D of SA with increasing SA-mole fraction; the D of DA in the DA/LA system is also larger than that of LA especially in the LA-poor region and steeply approaches that of LA with increasing LA-mole fraction. These D values and phase diagrams were compared with those for the binary mixtures of n-alkanes (C14/C20, C19/C20 and C20/C24); it is concluded that the two kinds of fatty acids always form their individual homodimers in their liquid mixtures regardless of their compositions and temperatures.

Through near infrared spectroscopy and 13C-NMR spin-lattice relaxation time measurements it was revealed that the molecules of the normal fatty acids in the liquid state are strongly dimerized even at 363K by hydrogen bonding between their carboxylic groups. Thus, dimer molecules for the acids are the units in their intra- and intermolecular movements. The dynamic molecular and aggregate structures of the fatty acids (C8-C18) in the liquid state were estimated through the analyses of their self-diffusion coefficient D, viscosity η, molar volume and X-ray diffraction. The apparent hydrodynamic radius evaluated from D and η for the fatty acid was almost constant, irrespective of the hydrocarbon chain length. This suggests that only a longitudinal translation (translational movement along molecular axes) would be allowed for the dimer molecules of fatty acids. In addition, the distribution function curves obtained from the X-ray diffraction data suggest that, in the pure liquid state, rod-like fatty acid dimers highly aggregate in parallel and probably make clusters that would be randomly aligned.

The effects of cationic ions on the conformational properties of gellan gum in aqueous solutions with and without salts are studied using highly purified lithium, sodium, and potassium-type gellan gum samples by measuring the osmotic pressure, intrinsic viscosity, and circular dichroism (CD). The M n values of Li, Na, and K-gellan obtained at 45°C were nearly the same. The M n values of Na-gellan or Li-gellan obtained at 45°C in aqueous solutions with added salts were almost half or slightly less than half the value of that obtained at 28°C, respectively. The temperature dependence of θ 201 and ( η sp / c p )for Li, Na, and K-gellan solutions with and without added salts showed drastic changes at the transition temperatures. These results could be interpreted as the occurrence of the coil to double-helix transition and partial aggregation of helices at the transition temperatures on lowering temperature. In the aqueous solutions without added salts, the transition temperatures for Li, Na, and K-gellans determined by CD are almost coincident with those obtained from viscometry. The transition temperatures for Li, Na, and K-gellan solutions increased with increasing polymer concentration but almost independent of the chemical species of countercations. In the aqueous solutions with added salts, the transition temperature of Li, Na, and K-gellan depends not only on polymer concentration but also the concentration of added salt and the chemical species of countercations. The observed transition temperature for K-gellan solution with KCl is higher than that for the solutions of Li-gellan with LiCl and Na-gellan with NaCl.

Phase diagrams for binary mixtures of sterols such as 5-cholesten-3β-ol (I), 5α-cholestan-3β-ol (II), 5β-cholestan-3α-ol (III) and 5β-cholestan-3β-ol (IV) were studied. II is similar to I in its straight, plank-like skeletal structure and in the direction of OH moiety linking directly to the steroid ring. III is similar to IV in its bending skeletal structure and differs in the direction of OH moiety from I, II and IV. From phase diagrams for all of their binary mixtures, it became clear that in I/II and also in II/IV systems the molecules of each component are phase-separated from each other in the solid state and provide a eutectic mixture. In I/III, II/III and III/IV systems, two kinds of molecules whose OH moieties are in opposite directions to each other made a 1:1 compound. On the other hand, in I/IV system I and IV molecules made an incongruent melting (peritectic) compound, which was less stable and, before its melting, decomposed into solid I and a 1:1-molar-ratio solution of I and IV at 373 K.

We studied formation of chiral aggregates of optical active N-lauroyl-L-valine (L-LVA), N-lauroyl-L-glutamic acid (L-LGA) and methylester of L-LVA (L-LVMe) in various solvents such as acetonitrile, 1,4-dioxane, tetrahydrofuran and 1,2-dichloroethane through the measurements of circular dichroism (CD), NMR chemical shift of N-H proton and vapor-pressure osmometry (VPO). The above acylamino acids and L-LVMe showed CD bands at 212-215 nm, whose intensities depended on temperature. The CD bands have been believed to come from the formation of chiral aggregates. However, by means of NMR and VPO analyses, the acylamino acids and L-LVMe were found to be present mostly as monomers in relatively polar solvents such as acetonitrile, 1,4-dioxane and tetrahydrofuran. On the other hand, L-LVA in 1,2-dichloroethane forms chiral aggregates; the mean aggregation number of L-LVA increases with increasing in its concentration.

5α-cholestan-3β-ol (II) is similar to 5-cholesten-3β-ol (cholesterol) (I) except the absence of the Δ5 double bond, whereas 5β-cholestan-3α-ol (III) is remarkably different from I in its skeletal structure and in the direction of its OH moiety. Two-dimensional thermodynamic properties such as surface pressure-molecular area (π-A) relationship, equilibrium spreading pressure (ESP) and enthalpy of compression of monolayer at air-water interface were studied for these sterols. II shows similar π-A relationships to I, whereas III gives the different ones. ESP value, increasing with increasing temperature, followed the order of II>I>III. Enthalpy of elution, ΔHESP, from the crystals onto water surface at ESP and also enthalpy of compression, ΔHcomp, of the monolayers from π=0 to ESP were obtained from the temperature dependence of ESP and of π-A relationship, respectively. The sum of ΔHESP and −ΔHcomp, which means the two-dimensional enthalpy of fusion, is approximately proportional to the ordinary enthalpy of fusion. II and III molecules gave a 1:1 compound in the mixed monolayer on water surface as well as in solid state. The ESP value for the 1:1 compound was also determined.

Thermodynamic properties such as melting point, enthalpy of fusion, and heat capacity for 5-cholesten-3β-ol (I), 5α-cholestan-3β-ol (II), and 5β-cholestan-3α-ol (III) were studied. The values of the melting point and the enthalpy of fusion for I were slightly larger than those for II, whereas the values for III were smaller than those for I and II. The heat capacity for I was to some extent larger than that for II or III in solid and even in liquid states. II is similar to I in the overall skeletal structure and in the direction of the OH moiety linking directly to the steroid ring. In addition, the X-ray powder diffraction pattern for II resembled that for I, whereas the pattern for III differed from that for I. The phase diagram for I/II mixture indicated that the I and II molecules are phase-separated in the solid state and give a eutectic mixture. The phase diagram results connecting with the data for the melting point, the enthalpy of fusion, and the heat capacity suggest that the cohesive force of I is stronger than that of II in spite of the similarity of I to II in the molecular and stacking structures. On the other hand, the phase diagrams of I/III and II/III mixtures indicated that I and III molecules and II and III molecules, whose OH moieties are in opposite directions to each other, made a strong 1 : 1 compound.

The translational movement, the dynamical molecular conformation, and the aggregate structure in the liquid state for three kinds of cis-type unsaturated fatty acids (cis-6-, cis-9-, and cis-11-octadecenoic acids), trans-type unsaturated acid (trans-9-octadecenoic acid), and n-saturated acid (octadecanoic acid) have been studied through the measurements of density, self-diffusion coefficient, 13C NMR spin−lattice relaxation time, and X-ray diffraction. The magnitude of the self-diffusion coefficient, D, fell in sequence of cis-type unsaturated acids > trans-type acid > saturated acid below 350 K. Above 350 K the value of D for the trans-type acid rose to those for the cis-type acids. On the other hand, the density ρ for the acids also fell in the order of cis-type acids > trans-type acid > saturated acid; the order of the density is just opposite to that expected from the results of the self-diffusion coefficient and other physical properties such as melting point and heat of fusion. This discrepancy betw...

Two-dimensional (2D) near-infrared (NIR) correlation spectroscopy was used to study the temperature-induced changes in the hydrogen bonding of butan-1-(ol-d) and 2-methylpropan-2-(ol-d) in the pure liquid phase. The similarity between the 2D correlation spectra of both studied butanols and their nondeuterated analogues proves that the isotopic substitution in the hydroxyl group affects little the dynamic properties of the hydrogen bonding. This conclusion also confirms the heterospectral analysis, performed for the spectra of the deuterated samples and their nondeuterated counterparts. In the asynchronous spectra of 2-methylpropan-2-ol and its deuterated analogue, we identified new bands at 7040 and 5226 cm-1, respectively, which are probably due to an intramolecular effect. Moreover, a heterospectral asynchronous plot develops a peak at (5286, 7085), not seen in the homospectral 2D plots of butan-1-(ol-d) and butan-1-ol, giving rise to an additional resolution enhancement. This new peak reveals different...

The self-associations of butan-1-ol, butan-2-ol, and 2-methylpropan-2-ol ( tert-butanol) in the pure liquid state and in carbon tetrachloride solutions have been studied mainly through near-infrared spectroscopic observation at various temperatures. A new analysis assuming a successive association process for the alcohol molecules was applied to the sharp band around 1410 nm (the first-overtone band of the OH stretching vibration mode attributed to free OH monomer and partly to OH polymer); it became clear that the mean association number for each alcohol increases with increasing concentration and decreases with increasing temperature. Comparisons of the association numbers at various constant temperatures for the three kinds of alcohols show that the association abilities are on the order butan-1-ol > butan-2-ol > 2-methylpropan-2-ol.

The self-association of (R)-, (S)- and (RS)-butan-2-ol in their carbon tetrachloride solutions was studied through the mid-infrared (mid-IR) and near-infrared (NIR) spectroscopic observations. The mid-IR and NIR spectra for each chiral butan-2-ol were compared with those for the racemic (RS)-butan-2-ol. Although it has been reported that the hydrogen bonding among the chiral butan-2-ol molecules was stronger than that among the racemic ones, any distinguishable differences between the chiral and the racemic butan-2-ol in CCl4 solution or even in their pure liquid state were not observed both in their mid-IR and NIR spectra. A superior analytical method, assuming a successive association process for the alcohol molecules, was applied to the analysis of the sharp band at 3630 cm−1 (the OH-stretching vibration mode attributed to free OH-monomer) for the (R)-, (S)- or (RS)-butan-2-ol in CCl4. The mean association number 〈N〉 for each alcohol increased with increasing in concentration until 0.12 mol dm−3 and then becomes constant (about four). On the other hand, Zanker's plotting method, assuming an equilibrium between monomers and only one kind of polymer species, was also applied to the analysis of the above spectroscopic results; the association number n evaluated from the Zanker's method fairly agreed with the 〈N〉 value in the concentration region of 0.12–0.60 mol dm−3.

Near-infrared (NIR) spectra of n -, sec -, and tert -butanol in CCl 4 were measured over a temperature range of 10–60°C. The spectra obtained were analyzed by both spectroscopic analytical methods such as calculations of the difference spectra and the second derivatives, and chemometrics, namely partial least squares (PLS) regression. The present study aims at comparing the spectroscopic analytical methods with chemometrics in the analysis of NIR spectra of n -, sec -, and tert -butanols in CCl 4 . The three kinds of alcohol showed an intense band due to the first overtone of the OH stretching mode in the 7120–7030 cm −1 (1404–1422 nm) region. The calculations of the difference spectra and the second derivatives revealed that the above bands of n - and sec -butanol consist of three and four component bands, respectively, due to the rotational isomerism of the monomer, the OH group weakly hydrogen-bonded with CCl 4 , and the terminal free OH groups of the self-associated species. For tert -butanol, which does not have the rotational isomerism, the corresponding band splits into only two components. Temperature of the alcohols was predicted by use of PLS regression. The regression coefficients for the models predicting the temperature of the alcohols were almost identical with the difference spectra of the alcohols between 10 and 60°C. Both the regression coefficients and the difference spectra reflect strongly the changes in the hydrogen bonds of the alcohols.

The temperature-dependent near-infrared (NIR) spectral variations of n- and tert-butyl alcohols in the pure liquid state have been studied by generalized two-dimensional (2D) correlation analysis. ...

The first paper in a series devoted to self-association in neat butanols presents the results of two-dimensional (2D) near-infrared (NIR) correlation analysis of temperature-induced spectral variations of sec-butanol. By taking advantage of resolution enhancement in the 2D correlation spectra, it was possible to identify spectral features due to vibrations of the free and associated OH groups in the first-overtone region. On the basis of a few assumptions, band assignments of the various types of OH bonds have been proposed. The monomer band (near 7100 cm−1) can be resolved into three components; two of them are due to a rotational isomerism (7089 and 7116 cm−1), and the third one is attributed to the free terminal OH groups in linear polymers (7055 cm−1). The presence of the 7055 cm−1 band implies that the intensity of the monomer peak cannot be used as a measure of the concentration of the monomer species (except in very diluted solutions). Thus, previous estimations of equilibrium constants and thermodynamic parameters associated with hydrogen-bond dissociation have been subject to unacceptable error. At higher temperatures, a new band near 6550 cm−1 becomes visible. This band originates from bended OHO bond, mostly in the cyclic polymers. In order to obtain more detailed information on the complex mechanism of the thermal dissociation of hydrogen-bonded sec-butanol in the pure liquid phase, the entire experimental temperature range was divided into narrower ranges, and then 2D correlation analysis was performed for smaller data sets. It has been shown that the variations of population of the polymeric species and the cyclic dimers are faster than the corresponding changes for the monomers. At elevated temperatures an appreciable dissociation of the cyclic species takes place.

Rate constants of fluorescence quenching by SCN − and efficiencies of enhanced intersystem crossing and free radical generation in fluorescence quenching were measured for several aromatic fluorescencers in acetonitrile. The results indicate that the quenching mechanism depends on δG and the switchover of quenching mechanism from exciplex formation to long-distance electron transfer occurs at δG ≈ −1.1 eV. The large shift of the switchover δG from −0.4 eV for aromatic quenchers to −1.1 eV for SCN − can be accounted for the difference in molecular size between aromatic quencher and SCN − .

Fundamental properties such as micellar weight, critical micelle concentration and cloud point were determined for aqueous solutions of polyoxyethylene (20) sorbitan monooleate (POESO) and polyoxyethylene (n) oleyl ether [POEOE and POE (10) 0E for n=20 and 10, respectively] recently prepared from oleic acid of high (>99%) and low purity. HPLC analysis and measurement of hydroxy value were conducted to clarify the distribution of the oxyethylene chain. For POESO and POEOE, no significant correlation between the above properties and oleic acid purity could be found. For POE (10) OE, however, the cloud point was higher for greater purity. This was confirmed by the temperature dependence of light scattering intensity.

Fourier transform neur-infrared spectra of Z -9-octadecen-1-ol in CCl 4 solutions have been measured to determine the molar absorption coefficients for both the first and second overtones of an OH stretching mode of its monomer. At concentrations below 1.4 × 10 −2 M, the alcohol exists completely in its monomeric form, and from the absorbance-concentration plots, the molar absorption coefficients have been obtained to be 103 and 5.03 dm 3 mol −1 cm −1 for the integrated absorbances (band area) of the first and second overtones, respectively.

A device for the deposition of a radioactive Langmuir-Blodgett (LB) film was developed with the use of: (1) a modified horizontal lifting method, (2) an extremely shallow trough, and (3) a surface pressure-generating system without piston oil. It made a precious radioactive subphase solution repeatedly usable while keeping its radioactivity concentration as high as possible. Any large-size thin films can be prepared by just changing the trough size. Two monomolecular-layers of Y-type films of cadmium [ 3 H] icosanoate and 109 Cd icosanoate were built up as 3 H and 109 Cd β-sources for electron spectroscopy with intensities of 1.5 GBq (40 mCi) and 7.4 MBq (200 μCi), respectively, and a size of 65×200 mm 2 . Excellent uniformity of the distribution of deposited radioactivity was confirmed by autoradiography and photometry.

The integrated molar absorption coefficients of the first overtone of an OH stretching mode of free octanoic acid were determined through a series of FT-NIR measurements in a CCl 4 solution at different temperatures. A few methods of calculation of the molar absorption coefficient were applied; the results were compared and discussed. It was shown that not all of the methods can be applied for the calculation if the plot of Beer's law does not pass through the origin. The results clearly show that the integrated molar absorption coefficient is strongly temperature dependent; its value increases approximately 0.6 dm 3 mol −1 cm −1 per one degree and the use of a constant value of the coefficient through a temperature range may lead to significant errors.

When electrolyte solutions are fed into the desalting cells in an electrodialyzer and an electric current is passed across the membranes, the velocity or the electrolyte concentration of the solutions and electric current density usually change from place to place in the electrodialyzer. When the electrolyte concentration at the membrane/solution interface reaches zero at the outlet of the desalting cell in which the velocity and electrolyte concentration are the least, the average electric current density applied to the electrodialyzer corresponds to the limiting current density of the electrodialyzer. On the basis of such an idea, a limiting current density equation for an electrodialyzer is expressed by Eq. (18) in this report. The equation contains the thickness of the desalting cell a, the length of the flow pass in the cell l, electrolyte concentration at the inlet of the electrodialyzer C in, standard deviation σ of velocity ratio K introduced under the assumption that the frequency of desalting cells for the velocity ratio is equated by normal distribution, current density disuniformity coefficient at the limiting current density φlim and the constants in the limiting current density equation holding at the outlet of the desalting cell in which the velocity is the least; m and n. Using an electrodialyzer (effective membrane area; 15 dm2), we have shown that Eq. (18) is able to express the limiting current density of an electrodialyzer reasonably. Applying Eq. (18), the relationships between the limiting current density and electrodialytic conditions in the electrodialyzer or the dimensions of the electrodialyzer are discussed.

This paper demonstrates the usefulness of principal component analysis (PCA) in the study of the dissociation process of oleyl alcohol ( cis-9-octadecen-1-ol) as the pure liquid. Fourier transform near infrared (FT-NIR) spectra of the neat alcohol were measured over a temperature range of 6.5–90°C in the 11,500–6000 cm−1 region. The degree of dissociation of the alcohol was determined by the intensities of the first and second overtones of the OH stretching mode of the monomer. PCA on the obtained spectra were calculated over three different regions, the entire 11,500–6000 cm−1 region and the 11,500–9087 and 9087–6000 cm−1 regions. PCA clearly reveals that there exists a break point at around 45°C in the dissociation process of the alcohol.

This paper discusses the molecular conformations and the liquid structures of triacylglycerols (TGs) and fatty acids in their melts. Three models for liquid state ordering have been proposed for TG melts to date: the smectic liquid crystal model, the nematic liquid crystal model, and the discotic model. To completely resolve the liquid structure of TGs, further research is required. However, some information on the molecular level has been obtained for fatty acids that are relatively simple compounds. The combination of various spectroscopic and thermodynamic measurements revealed that the hydrogen-bonded dimers of fatty acids are units of intermolecular and intramolecular movements in the liquids and in non-polar solvents. The dimers that construct the clusters resemble the smectic liquid crystal and determine the physicochemical properties of the liquid of the fatty acid. Cholesterol stabilizes the clusters, while ethanol destroys them. Self-diffusion and neutron diffraction measurements revealed that two kinds of fatty acids exist in their binary liquid mixture exist as the homodimers composed of same species.

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 group's ═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.

The study of the infrared spectra of neat cis-9, cis-12-octadecadienoic acid in the liquid phase has been carried out over a temperature range of 31 to 110°C. In the region of 1710 cm−1 a strong absorption band accompanied by two weaker bands appears. The strong band is assigned to a C=O stretching vibration due to the dimeric form of the acid, and the weaker bands near 1750 and 1650 cm−1 are attributed to a C=O stretching vibration due to its monomer and to C=C stretching modes arising from both forms, respectively. The shape of the band envelope strongly depends on temperature. Making a curve fitting, one can determine spectral parameters of the individual bands, and from them it is possible to calculate the degree of dissociation of the acid. The obtained values of the degree of dissociation enable us to determine enthalpy (Δ H) and entropy (Δ S) for the process of dissociation of dimeric species into free molecules, and the results seem to be reasonable as compared with the literature data for other fatty acids.

Fourier transform near-infrared (FT-NIR) technique has been employed to determine the degree of dissociation and the thermodynamic parameters of octanoic acid in the liquid phase. FT-NIR absorption spectra of the acid over a temperature range of 15 to 92°C were recorded. From the spectra, intensities of the first overtone of the OH stretching mode due to the monomer form of the acid were extracted and were used to calculate the degree of dissociation and the thermodynamic parameters for the process of dissociation of dimeric octanoic acid into monomer species. In the 7400–6700 cm−1 region there appear many bands that are heavily overlapped; the attempts to apply curve-fitting and deconvolution algorithms to separate individual bands have failed. Here, a simple and reliable method of calculation of the intensities of the first overtone of the OH stretching mode due to the monomer is proposed. Also, an excellent procedure of determining the molar absorption coefficients (integrated and at peak position) through a series of measurements in CCl4 solution at very low concentrations is presented. The bands due to CH vibrations were eliminated in two ways; one way involved taking the concentration as a reference, and the other used the band area of the second overtone of the CH stretching modes as a reference. In the operation the spectrum of neat octanoic acid at 15.1°C was employed. The coefficients obtained by both methods are compared and discussed. The present studies indicate that both band areas and peak heights give results which are found to be in very good agreement.

A series of bipolar surfactants, ω-hydroxyalkyldimethyloctadecylammonium bromide {HADMOA( n ); ω-hydroxyalkyl chain length n = 10, 12, 14, 16, 18, 20} were synthesized and the monolayer behavior at the air-water interface was studied. The isotherms of the bipolar HADMOA(18) were compared with those for the monopolar counterpart DMDOA (dimethyldioctadecylammonium bromide). The effect of the ω-hydroxyalkly chain length was also examined. The results were as follows: (1) The monopolar DMDOA exhibits a solid condensed region while the bipolar HADMOA(18) exhibits only an expanded region. The monolayer of the HADMOA(18) collapses before a condensed state is achieved. (2) The isotherm of the bipolar HADMOA(18) is much less sensitive to temperature and to the ionic strength of the subphase than that of the monopolar DMDOA. (3) The general features of the monolayers of the other HADMOA( n ) ( n = 20, 16, 14, 12) are analogous to those of the HADMOA(18); i.e., the monolayers are of the expanded type, and collapse before a condensed state is achieved. (4) The above results can be explained by assuming that the HADMOA( n ) molecules in the monolayer take a "flat" conformation on the aqueous subphase where both the polar groups, {HOCH 2 - and N + (CH 3 ) 2 R,R ′ -}, are in contact with water and are never forced out from the interface by such experimental means as lateral compression, lowering the temperature, or increasing the ionic strength of the subphase.

Morphological study of thin-film systems of pure fullerene (C[sub 60]) and some other amphiphilic compounds adsorbed on glass plates was conducted on the electron microscopic scale. Each component in benzene was placed on the aqueous subphase of distilled water (pH 5.8) according to the Langmuir technique to form its thin film; the thin film was transferred onto one side of a glass-plate surface by the subphase-lowering method. Each film-adsorbed site was replicated with a plasma-induced polymerized naphthalene film. The glass plates thus surface-treated were gradually dipped into 5% fluoric acid solution in order to obtain their respective single replica stage films for transmission electron microscopic observation. For example, the replica image of the C[sub 60] thin-film was able to show numerous necklace-like patterns forming a two-dimensional network on the electron microscopic scale. This network structure provides the possibility of applicational utilities such as a superconductive thin-film. 22 refs., 9 figs.

Molecular interactions between benzene and hydrocarbons having six carbon atoms, such as hexane, cyclohexane and 1-hexene in their binary liquid mixtures were studied through the measurements of density, viscosity, self-diffusion coefficient, (13)C NMR spin-lattice relaxation time and (1)H NMR chemical shift. CH/pi attraction between hexane and benzene in their binary mixture was observed in a relatively benzene rich region, whereas a special attractive interaction was not observed between cyclohexane and benzene. On the other hand, 1-hexene and benzene in their binary mixtures were characteristic in their self-diffusion coefficient behaviors: 1-hexene more strongly attract benzene not only by the CH/pi attraction but also probably by the p/p interaction between the double bond in 1-hexene and the p-electron in benzene ring.