Masaru Matsugami | National Institute of Technology, Kumamoto College (original) (raw)
Papers by Masaru Matsugami
Journal of Molecular Liquids, 2007
Alkali chlorides (MCl, M = Li + , Na + , and K + ) -induced phase separation of acetonitrile-wate... more Alkali chlorides (MCl, M = Li + , Na + , and K + ) -induced phase separation of acetonitrile-water mixtures at 298 K has been investigated. Phase diagrams of acetonitrile-H 2 O-MCl systems have shown that phase separation of the mixtures occurs at lower salt concentration in the order of NaCl b KCl b LiCl. Phase separation of acetonitrile-D 2 O-MCl systems takes place in the same order as the acetonitrile-H 2 O-MCl ones, but the D 2 O systems are separated at lower concentration of each salt than the H 2 O systems. To clarify phase separation of acetonitrile-water-MCl mixtures at a mesoscopic scale, small-angle neutron scattering (SANS) experiments have been made on acetonitrile-D 2 O-MCl mixtures before phase separation as a function of salt concentration. The SANS results in terms of the Ornstein-Zernike correlation length have suggested that D 2 O clusters are more easily evolved with increasing salt concentration in the order of NaCl N KCl N LiCl, which is in agreement with the order of phase separation. Based on the present results, mechanisms of LiCl-, NaCl-, and KCl-induced phase separation of acetonitrile-water mixtures have been discussed.
Journal of the Ceramic Society of Japan, 2007
Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-diox... more Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-dioxane, have been investigated at the molecular level by means of small-angle neutron scattering SANS and NMR relaxation. It has been shown that the organic solvent and water molecules are inhomogeneously mixed each other at the molecular level, although their mixtures are homogeneous at the macroscopic scale. Thus, both organic solvent clusters and water clusters coexist in the mixtures. The present investigation has also revealed that the microinhomogeneity of acetonitrile-water and 1,4-dioxane-water mixtures is gradually enhanced by cooling or adding salts toward phase separation. Based on the results, the effect of microinhomogeneity for solvent mixtures on chemical reactions was considered.
Journal of Molecular Liquids, 2007
At 279, 287, 298, and 307 K the heterogeneity of acetonitrile–water mixtures in a range of aceton... more At 279, 287, 298, and 307 K the heterogeneity of acetonitrile–water mixtures in a range of acetonitrile mole fraction xAN from 0.2 to 0.6 has been evaluated in terms of Ornstein–Zernike correlation length, concentration and density fluctuations, and Kirkwood–Buff parameters obtained from small-angle neutron scattering (SANS) experiments. At 298 K the correlation lengths for CH3CN–D2O (D=2H) and CD3CN–H2O mixtures have shown that
In the previous study, we investigated the cation recognition by 12-crown-4 ether with the 3D-RIS... more In the previous study, we investigated the cation recognition by 12-crown-4 ether with the 3D-RISM theory [Ikuta, Y. et al., Chem. Phys. Lett., 2007, 433, 403], and showed the applicability of the theory to the problem. The results show that a 12-crown-4 ether recognizes Li + and Mg 2+ . 18-crown-6 ether is widely used in comparison with 12-crown-4 ether. In this study, we calculated three-dimensional distributions of water as well as cations (Li + , K + , Mg 2+ , Ca 2+ ) inside and outside 18-crown-6 ether in aqueous solutions of electrolytes. A 18-crown-6 ether recognizes not only Li + and Mg 2+ but also K + and Ca 2+ . K + is dehydrated in the host cavity whereas other cations are hydrated. It is found that a hydration structure, as well as cation size, is important for the molecular recognition by crown ether.
Journal of Physical Chemistry B, 2006
Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire... more Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire mole fraction range of EG, 0 e x EG e 1, have been clarified by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), and small-angle neutron scattering (SANS) techniques. The DSC curves obtained have shown that the EG-water solutions over the range of EG mole fraction 0.3 e x EG e 0.5 are kept in the supercooling state until ∼100 K, and those in the range of 0.6 e x EG e 0.8 are vitrified, and those in the ranges of 0 < x EG e 0.2 and 0.9 e x EG < 1 are crystallized. The radial distribution function (RDF) for pure EG obtained from the LAXS measurements has suggested that a gauche conformation of an EG molecule is favorable in the liquid. The RDFs for the EG-water solutions have shown that the structure of the binary solutions moderately changes from the inherent structure of EG to the tetrahedral-like structure of water when the water content increases. The SANS intensities for deuterated ethylene glycol (HOCD 2 CD 2 OH) (EGd 4 )-water solutions at x EG ) 0.4 and 0.6 have not been significantly observed in the temperature range from 298 to 173 K, showing that EG and water molecules are homogeneously mixed. On the other hand, the SANS intensities at x EG ) 0.2 and 0.9 have been strengthened when the temperature decreases due to crystallization of the solutions. On the basis of all the present results, a relation between thermal properties of EG-water binary solutions and their mixing states clarified by the LAXS and SANS measurements has been discussed at the molecular level.
The Journal of Physical Chemistry B, 2008
Differential scanning calorimetry (DSC) has been performed on aqueous mixtures of three diols, wh... more Differential scanning calorimetry (DSC) has been performed on aqueous mixtures of three diols, which involve a linear carbon chain, HO-(CH 2 ) n -OH (n ) 3, 4, and 5), over the whole mole fraction range of diols. The DSC results have shown the alkyl chain parity for the freezing process of the aqueous mixtures: aqueous mixtures of 1,3-propanediol (PrD) and 1,5-pentanediol (PeD) are kept in the supercooled state or vitrified over a wide mole fraction range, while those of 1,4-butanediol (BuD) are easily crystallized. The structure of PrD-water mixtures has been elucidated by using the large-angle X-ray scattering (LAXS) technique. It has been suggested that the structural change of PrD-water mixtures occurs at PrD mole fractions of x PrD ) 0.4 and 0.8: in the range of x PrD e 0.4 where the tetrahedral-like structure of water predominates, in the range of 0.4 < x PrD < 0.8 where both PrD and water structures coexist, and in the range of x PrD g 0.8 where the inherent structure of PrD is mainly formed. 17 O and 1 H NMR relaxation measurements have been made on aqueous mixtures of ethylene glycol (EG, n ) 2), PrD, and BuD to clarify the dynamics of H 2 17 O and diol molecules. The 17 O NMR relaxation rates have suggested that the rotational motion of water molecules is gradually retarded in the diol-water mixtures with increasing diol content and that the restriction of the motion is more remarkable in the order of EG < PrD < BuD. On the basis of all the results, together with comparison with those of methanol-water, ethanol-water, and 1-propanol-water mixtures previously reported, the mixing state of diol-water mixtures has been discussed at the molecular level.
The Journal of Chemical Physics, 2014
The density fluctuation of water in the supercritical region was investigated theoretically using... more The density fluctuation of water in the supercritical region was investigated theoretically using the reference interaction site model theory combined with the Kovalenko-Hirata closure relation, the so-called RISM-KH theory. The density fluctuation was evaluated by the numerical differentiation of density with respect to pressure at constant temperature. The density fluctuations plotted against density show finite maxima along a line slightly off from the critical isochore, in accordance with experimental results. The microscopic structures of water on both regions that were separated by the line were investigated by analyzing the site-site radial distribution functions. The analysis clearly indicates that the structure is determined by the two effects featuring liquid states: the packing or volume exclusion effect and the screening of the Coulomb interaction or the hydrogen bond, both becoming more important at higher densities. An interplay of the two effects creates maxima of the density fluctuation in the supercritical region of water.
Analytical Sciences, 2013
It has been established that poly(benzyl methacrylate) in a room-temperature ionic liquid, 1-ethy... more It has been established that poly(benzyl methacrylate) in a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mIm(+)][TFSA(-)]), exhibits lower critical solution temperature (LCST)-type phase separation. In this work we investigated the solvation structure of benzyl methacrylate monomer in the ionic liquid by using high-energy X-ray diffraction with the aid of a molecular dynamics simulation. It was found that the C2mIm cation orderly distributes above and below a benzyl group within benzil methacrylate (BnMA), while the TFSA anion distributes around the equatorial position of the benzyl group where no cation distribution is found, with a weak interaction between TFSA and BnMA. The relationship between specific solvation and the LCST phase separation mechanism was considered at the molecular level.
Phys. Chem. Chem. Phys., 2015
Molecular dynamics simulations of equimolar mixtures of glymes (triglyme and tetraglyme) and Li[T... more Molecular dynamics simulations of equimolar mixtures of glymes (triglyme and tetraglyme) and Li[TFSA] (lithium bis(trifluoromethylsulfonyl)amide) show that the glyme chain length affects the coordination geometries of Li(+), which induces the changes in interactions between the [Li(glyme)](+) complex and [TFSA](-) anions and diffusion of ions in the equimolar mixtures.
Physical chemistry chemical physics : PCCP, Jan 11, 2015
Certain molten complexes of Li salts and solvents can be regarded as ionic liquids. In this study... more Certain molten complexes of Li salts and solvents can be regarded as ionic liquids. In this study, the local structure of Li(+) ions in equimolar mixtures ([Li(glyme)]X) of glymes (G3: triglyme and G4: tetraglyme) and Li salts (LiX: lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]), lithium bis(pentafluoroethanesulfonyl)amide (Li[BETI]), lithium trifluoromethanesulfonate (Li[OTf]), LiBF4, LiClO4, LiNO3, and lithium trifluoroacetate (Li[TFA])) was investigated to discriminate between solvate ionic liquids and concentrated solutions. Raman spectra and ab initio molecular orbital calculations have shown that the glyme molecules adopt a crown-ether like conformation to form a monomeric [Li(glyme)](+) in the molten state. Further, Raman spectroscopic analysis allowed us to estimate the fraction of the free glyme in [Li(glyme)]X. The amount of free glyme was estimated to be a few percent in [Li(glyme)]X with perfluorosulfonylamide type anions, and thereby could be regarded as solvate ...
Journal of Molecular Liquids, 2007
Alkali chlorides (MCl, M = Li + , Na + , and K + ) -induced phase separation of acetonitrile-wate... more Alkali chlorides (MCl, M = Li + , Na + , and K + ) -induced phase separation of acetonitrile-water mixtures at 298 K has been investigated. Phase diagrams of acetonitrile-H 2 O-MCl systems have shown that phase separation of the mixtures occurs at lower salt concentration in the order of NaCl b KCl b LiCl. Phase separation of acetonitrile-D 2 O-MCl systems takes place in the same order as the acetonitrile-H 2 O-MCl ones, but the D 2 O systems are separated at lower concentration of each salt than the H 2 O systems. To clarify phase separation of acetonitrile-water-MCl mixtures at a mesoscopic scale, small-angle neutron scattering (SANS) experiments have been made on acetonitrile-D 2 O-MCl mixtures before phase separation as a function of salt concentration. The SANS results in terms of the Ornstein-Zernike correlation length have suggested that D 2 O clusters are more easily evolved with increasing salt concentration in the order of NaCl N KCl N LiCl, which is in agreement with the order of phase separation. Based on the present results, mechanisms of LiCl-, NaCl-, and KCl-induced phase separation of acetonitrile-water mixtures have been discussed.
Journal of the Ceramic Society of Japan, 2007
Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-diox... more Mixing states for aqueous solutions of water-miscible organic solvents, acetonitrile and 1,4-dioxane, have been investigated at the molecular level by means of small-angle neutron scattering SANS and NMR relaxation. It has been shown that the organic solvent and water molecules are inhomogeneously mixed each other at the molecular level, although their mixtures are homogeneous at the macroscopic scale. Thus, both organic solvent clusters and water clusters coexist in the mixtures. The present investigation has also revealed that the microinhomogeneity of acetonitrile-water and 1,4-dioxane-water mixtures is gradually enhanced by cooling or adding salts toward phase separation. Based on the results, the effect of microinhomogeneity for solvent mixtures on chemical reactions was considered.
Journal of Molecular Liquids, 2007
At 279, 287, 298, and 307 K the heterogeneity of acetonitrile–water mixtures in a range of aceton... more At 279, 287, 298, and 307 K the heterogeneity of acetonitrile–water mixtures in a range of acetonitrile mole fraction xAN from 0.2 to 0.6 has been evaluated in terms of Ornstein–Zernike correlation length, concentration and density fluctuations, and Kirkwood–Buff parameters obtained from small-angle neutron scattering (SANS) experiments. At 298 K the correlation lengths for CH3CN–D2O (D=2H) and CD3CN–H2O mixtures have shown that
In the previous study, we investigated the cation recognition by 12-crown-4 ether with the 3D-RIS... more In the previous study, we investigated the cation recognition by 12-crown-4 ether with the 3D-RISM theory [Ikuta, Y. et al., Chem. Phys. Lett., 2007, 433, 403], and showed the applicability of the theory to the problem. The results show that a 12-crown-4 ether recognizes Li + and Mg 2+ . 18-crown-6 ether is widely used in comparison with 12-crown-4 ether. In this study, we calculated three-dimensional distributions of water as well as cations (Li + , K + , Mg 2+ , Ca 2+ ) inside and outside 18-crown-6 ether in aqueous solutions of electrolytes. A 18-crown-6 ether recognizes not only Li + and Mg 2+ but also K + and Ca 2+ . K + is dehydrated in the host cavity whereas other cations are hydrated. It is found that a hydration structure, as well as cation size, is important for the molecular recognition by crown ether.
Journal of Physical Chemistry B, 2006
Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire... more Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire mole fraction range of EG, 0 e x EG e 1, have been clarified by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), and small-angle neutron scattering (SANS) techniques. The DSC curves obtained have shown that the EG-water solutions over the range of EG mole fraction 0.3 e x EG e 0.5 are kept in the supercooling state until ∼100 K, and those in the range of 0.6 e x EG e 0.8 are vitrified, and those in the ranges of 0 < x EG e 0.2 and 0.9 e x EG < 1 are crystallized. The radial distribution function (RDF) for pure EG obtained from the LAXS measurements has suggested that a gauche conformation of an EG molecule is favorable in the liquid. The RDFs for the EG-water solutions have shown that the structure of the binary solutions moderately changes from the inherent structure of EG to the tetrahedral-like structure of water when the water content increases. The SANS intensities for deuterated ethylene glycol (HOCD 2 CD 2 OH) (EGd 4 )-water solutions at x EG ) 0.4 and 0.6 have not been significantly observed in the temperature range from 298 to 173 K, showing that EG and water molecules are homogeneously mixed. On the other hand, the SANS intensities at x EG ) 0.2 and 0.9 have been strengthened when the temperature decreases due to crystallization of the solutions. On the basis of all the present results, a relation between thermal properties of EG-water binary solutions and their mixing states clarified by the LAXS and SANS measurements has been discussed at the molecular level.
The Journal of Physical Chemistry B, 2008
Differential scanning calorimetry (DSC) has been performed on aqueous mixtures of three diols, wh... more Differential scanning calorimetry (DSC) has been performed on aqueous mixtures of three diols, which involve a linear carbon chain, HO-(CH 2 ) n -OH (n ) 3, 4, and 5), over the whole mole fraction range of diols. The DSC results have shown the alkyl chain parity for the freezing process of the aqueous mixtures: aqueous mixtures of 1,3-propanediol (PrD) and 1,5-pentanediol (PeD) are kept in the supercooled state or vitrified over a wide mole fraction range, while those of 1,4-butanediol (BuD) are easily crystallized. The structure of PrD-water mixtures has been elucidated by using the large-angle X-ray scattering (LAXS) technique. It has been suggested that the structural change of PrD-water mixtures occurs at PrD mole fractions of x PrD ) 0.4 and 0.8: in the range of x PrD e 0.4 where the tetrahedral-like structure of water predominates, in the range of 0.4 < x PrD < 0.8 where both PrD and water structures coexist, and in the range of x PrD g 0.8 where the inherent structure of PrD is mainly formed. 17 O and 1 H NMR relaxation measurements have been made on aqueous mixtures of ethylene glycol (EG, n ) 2), PrD, and BuD to clarify the dynamics of H 2 17 O and diol molecules. The 17 O NMR relaxation rates have suggested that the rotational motion of water molecules is gradually retarded in the diol-water mixtures with increasing diol content and that the restriction of the motion is more remarkable in the order of EG < PrD < BuD. On the basis of all the results, together with comparison with those of methanol-water, ethanol-water, and 1-propanol-water mixtures previously reported, the mixing state of diol-water mixtures has been discussed at the molecular level.
The Journal of Chemical Physics, 2014
The density fluctuation of water in the supercritical region was investigated theoretically using... more The density fluctuation of water in the supercritical region was investigated theoretically using the reference interaction site model theory combined with the Kovalenko-Hirata closure relation, the so-called RISM-KH theory. The density fluctuation was evaluated by the numerical differentiation of density with respect to pressure at constant temperature. The density fluctuations plotted against density show finite maxima along a line slightly off from the critical isochore, in accordance with experimental results. The microscopic structures of water on both regions that were separated by the line were investigated by analyzing the site-site radial distribution functions. The analysis clearly indicates that the structure is determined by the two effects featuring liquid states: the packing or volume exclusion effect and the screening of the Coulomb interaction or the hydrogen bond, both becoming more important at higher densities. An interplay of the two effects creates maxima of the density fluctuation in the supercritical region of water.
Analytical Sciences, 2013
It has been established that poly(benzyl methacrylate) in a room-temperature ionic liquid, 1-ethy... more It has been established that poly(benzyl methacrylate) in a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mIm(+)][TFSA(-)]), exhibits lower critical solution temperature (LCST)-type phase separation. In this work we investigated the solvation structure of benzyl methacrylate monomer in the ionic liquid by using high-energy X-ray diffraction with the aid of a molecular dynamics simulation. It was found that the C2mIm cation orderly distributes above and below a benzyl group within benzil methacrylate (BnMA), while the TFSA anion distributes around the equatorial position of the benzyl group where no cation distribution is found, with a weak interaction between TFSA and BnMA. The relationship between specific solvation and the LCST phase separation mechanism was considered at the molecular level.
Phys. Chem. Chem. Phys., 2015
Molecular dynamics simulations of equimolar mixtures of glymes (triglyme and tetraglyme) and Li[T... more Molecular dynamics simulations of equimolar mixtures of glymes (triglyme and tetraglyme) and Li[TFSA] (lithium bis(trifluoromethylsulfonyl)amide) show that the glyme chain length affects the coordination geometries of Li(+), which induces the changes in interactions between the [Li(glyme)](+) complex and [TFSA](-) anions and diffusion of ions in the equimolar mixtures.
Physical chemistry chemical physics : PCCP, Jan 11, 2015
Certain molten complexes of Li salts and solvents can be regarded as ionic liquids. In this study... more Certain molten complexes of Li salts and solvents can be regarded as ionic liquids. In this study, the local structure of Li(+) ions in equimolar mixtures ([Li(glyme)]X) of glymes (G3: triglyme and G4: tetraglyme) and Li salts (LiX: lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]), lithium bis(pentafluoroethanesulfonyl)amide (Li[BETI]), lithium trifluoromethanesulfonate (Li[OTf]), LiBF4, LiClO4, LiNO3, and lithium trifluoroacetate (Li[TFA])) was investigated to discriminate between solvate ionic liquids and concentrated solutions. Raman spectra and ab initio molecular orbital calculations have shown that the glyme molecules adopt a crown-ether like conformation to form a monomeric [Li(glyme)](+) in the molten state. Further, Raman spectroscopic analysis allowed us to estimate the fraction of the free glyme in [Li(glyme)]X. The amount of free glyme was estimated to be a few percent in [Li(glyme)]X with perfluorosulfonylamide type anions, and thereby could be regarded as solvate ...