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Tomokazu Yoshimura - One of the best experts on this subject based on the ideXlab platform.
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adsorption and aggregation properties of alkoxy group modified homogeneous Polyoxyethylene Alkyl Ether nonionic surfactants
Journal of Molecular Liquids, 2019Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The development of new surfactants with interesting properties and new functionalities that can be controlled in a simple manner is an important industrial objective. Herein, we report the synthesis of homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants modified with alkoxy groups (C12EO8OR, where C12 and EO8 are dodecyl and octaoxyethylene chains, respectively, and R = Me and Et) from a homogeneous EO-type hexaoxyethylene dodecyl Ether (C12EO6) and diethylene glycol monomethyl Ether or diethylene glycol monoethyl Ether. The adsorption and aggregation properties of these surfactants were characterized through cloud point and surface tension measurements, and by small-angle X-ray scattering, polarization microscopy, and cryogenic transmission electron microscopy; these properties were compared to those of previously reported homogeneous EO-type (C12EO8) and polyoxypropylene-Polyoxyethylene type surfactants (C12EO8POy, y = 1, 2, 3). The introduction of a methoxy or ethoxy group at the terminus of the EO chain in C12EO8 resulted in an increase in hydrophobicity and a greatly reduced cloud point. Substitution of the terminal hydroxy group of the EO chain in C12EO8 with methoxy and then ethoxy led to increasingly lower surface tensions in solution and more efficient air/water interfacial adsorption. C12EO8OR formed small micelles at low concentrations in solution, and the micelles of C12EO8OMe transformed to hexagonal liquid crystals with increasing surfactant concentration, whereas C12EO8OEt remained to form micelles even at high concentration; that is, the introduction of bulkier functional groups into the C12EO8 surfactant helps to control the formation of aggregates with higher-order structures.
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structure and catalytic activities of gold nanoparticles protected by homogeneous Polyoxyethylene Alkyl Ether type nonionic surfactants
Langmuir, 2019Co-Authors: Shiho Yada, Tomokazu YoshimuraAbstract:Gold nanoparticles were prepared in aqueous solutions containing four homogeneous Polyoxyethylene (EO) Alkyl Ether type nonionic surfactants: octaoxyethylene dodecyl Ether (C12EO8), methoxyoctaoxyethylene dodecyl Ether (C12EO8OMe), ethoxyoctaoxyethylene dodecyl Ether (C12EO8OEt), and trioxypropylene-octaoxyethylene dodecyl Ether (C12EO8PO3). The sizes of obtained gold nanoparticles were almost independent of the terminal group in the EO surfactants; and the average sizes of nanoparticles prepared by surfactants with hydroxy, methoxy, ethoxy, and trioxypropylene terminal groups at [surfactant]:[Au3+] = 1:1 were 5.1 ± 1.2, 8.1 ± 1.4, 6.4 ± 2.1, and 8.6 ± 2.9 nm, respectively. The gold nanoparticles easily aggregated togEther according to the increasing hydrophobicity of hydroxy < methoxy ethoxy < trioxypropylene terminal groups. Highly stable dispersed nanoparticles were observed with hydroxy group in the EO terminal group. On the other hand, introducing hydrophobic moiety to the hydroxy group resulted in a...
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emulsification solubilization and detergency behaviors of homogeneous polyoxypropylene Polyoxyethylene Alkyl Ether type nonionic surfactants
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Shiho Yada, Keisuke Matsuoka, Yu Nagai Kanasaki, Keiko Gotoh, Tomokazu YoshimuraAbstract:Abstract The emulsification and solubilization properties and detergency behaviors were investigated using homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether type nonionic surfactants (C12EOxPO3, where x represents EO chain lengths of 6 and 8, and C12 and PO3 indicate the dodecyl chain and single trioxypropylene chain, respectively) and Polyoxyethylene (EO) Alkyl Ether type nonionic surfactants (C12EOx, x = 6 and 8). These nonionic surfactants possess single EO and PO chain lengths without a distribution. An oil-in-water (O/W) type emulsion prepared using mixtures of nonionic surfactant C12EOxPO3 or C12EOx solutions and squalane was shown to be stable in the order of C12EO6PO3
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adsorption dynamics of homogeneous polyoxypropylene Polyoxyethylene Alkyl Ether nonionic surfactants at the air water interface
Journal of Molecular Liquids, 2018Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The dynamic surface tensions of two homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants with terminal hydroxy group (C12EOx, where C12 is a dodecyl chain and x is the length of the EO chain; x = 6, 8) and two homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether nonionic surfactants (C12EOxPO3, where PO3 is a trioxypropylene chain inserted between the EOx and the terminal hydroxy group) were measured using the maximum bubble pressure method. The effects of EO chain length, the presence or absence of the PO3 chain, and the surfactant concentration on the maximum rates of surface-tension reduction and diffusion coefficient were investigated. The C12EO6PO3 surfactant exhibited the fastest rate of surface-tension reduction of the four systems studied, despite its complex hydrophobic-Alkyl-chain/hydrophilic-EO-chain/hydrophobic-PO-chain structure that differs from that of conventional EO Alkyl Ether surfactants. The diffusion coefficients obtained from short and long time analyses indicate that surfactant diffusion to the subsurface is faster for the C12EOxPO3 surfactants than the C12EOx surfactants (short time data), while surfactant adsorption from the subsurface to the air/water interface is faster for the C12EOx surfactants than the C12EOxPO3 surfactants (long time data).
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Adsorption dynamics of homogeneous polyoxypropylene-Polyoxyethylene Alkyl Ether nonionic surfactants at the air/water interface
Journal of Molecular Liquids, 2018Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The dynamic surface tensions of two homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants with terminal hydroxy group (C12EOx, where C12 is a dodecyl chain and x is the length of the EO chain; x = 6, 8) and two homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether nonionic surfactants (C12EOxPO3, where PO3 is a trioxypropylene chain inserted between the EOx and the terminal hydroxy group) were measured using the maximum bubble pressure method. The effects of EO chain length, the presence or absence of the PO3 chain, and the surfactant concentration on the maximum rates of surface-tension reduction and diffusion coefficient were investigated. The C12EO6PO3 surfactant exhibited the fastest rate of surface-tension reduction of the four systems studied, despite its complex hydrophobic-Alkyl-chain/hydrophilic-EO-chain/hydrophobic-PO-chain structure that differs from that of conventional EO Alkyl Ether surfactants. The diffusion coefficients obtained from short and long time analyses indicate that surfactant diffusion to the subsurface is faster for the C12EOxPO3 surfactants than the C12EOx surfactants (short time data), while surfactant adsorption from the subsurface to the air/water interface is faster for the C12EOx surfactants than the C12EOxPO3 surfactants (long time data).
Shiho Yada - One of the best experts on this subject based on the ideXlab platform.
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adsorption and aggregation properties of alkoxy group modified homogeneous Polyoxyethylene Alkyl Ether nonionic surfactants
Journal of Molecular Liquids, 2019Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The development of new surfactants with interesting properties and new functionalities that can be controlled in a simple manner is an important industrial objective. Herein, we report the synthesis of homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants modified with alkoxy groups (C12EO8OR, where C12 and EO8 are dodecyl and octaoxyethylene chains, respectively, and R = Me and Et) from a homogeneous EO-type hexaoxyethylene dodecyl Ether (C12EO6) and diethylene glycol monomethyl Ether or diethylene glycol monoethyl Ether. The adsorption and aggregation properties of these surfactants were characterized through cloud point and surface tension measurements, and by small-angle X-ray scattering, polarization microscopy, and cryogenic transmission electron microscopy; these properties were compared to those of previously reported homogeneous EO-type (C12EO8) and polyoxypropylene-Polyoxyethylene type surfactants (C12EO8POy, y = 1, 2, 3). The introduction of a methoxy or ethoxy group at the terminus of the EO chain in C12EO8 resulted in an increase in hydrophobicity and a greatly reduced cloud point. Substitution of the terminal hydroxy group of the EO chain in C12EO8 with methoxy and then ethoxy led to increasingly lower surface tensions in solution and more efficient air/water interfacial adsorption. C12EO8OR formed small micelles at low concentrations in solution, and the micelles of C12EO8OMe transformed to hexagonal liquid crystals with increasing surfactant concentration, whereas C12EO8OEt remained to form micelles even at high concentration; that is, the introduction of bulkier functional groups into the C12EO8 surfactant helps to control the formation of aggregates with higher-order structures.
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structure and catalytic activities of gold nanoparticles protected by homogeneous Polyoxyethylene Alkyl Ether type nonionic surfactants
Langmuir, 2019Co-Authors: Shiho Yada, Tomokazu YoshimuraAbstract:Gold nanoparticles were prepared in aqueous solutions containing four homogeneous Polyoxyethylene (EO) Alkyl Ether type nonionic surfactants: octaoxyethylene dodecyl Ether (C12EO8), methoxyoctaoxyethylene dodecyl Ether (C12EO8OMe), ethoxyoctaoxyethylene dodecyl Ether (C12EO8OEt), and trioxypropylene-octaoxyethylene dodecyl Ether (C12EO8PO3). The sizes of obtained gold nanoparticles were almost independent of the terminal group in the EO surfactants; and the average sizes of nanoparticles prepared by surfactants with hydroxy, methoxy, ethoxy, and trioxypropylene terminal groups at [surfactant]:[Au3+] = 1:1 were 5.1 ± 1.2, 8.1 ± 1.4, 6.4 ± 2.1, and 8.6 ± 2.9 nm, respectively. The gold nanoparticles easily aggregated togEther according to the increasing hydrophobicity of hydroxy < methoxy ethoxy < trioxypropylene terminal groups. Highly stable dispersed nanoparticles were observed with hydroxy group in the EO terminal group. On the other hand, introducing hydrophobic moiety to the hydroxy group resulted in a...
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emulsification solubilization and detergency behaviors of homogeneous polyoxypropylene Polyoxyethylene Alkyl Ether type nonionic surfactants
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Shiho Yada, Keisuke Matsuoka, Yu Nagai Kanasaki, Keiko Gotoh, Tomokazu YoshimuraAbstract:Abstract The emulsification and solubilization properties and detergency behaviors were investigated using homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether type nonionic surfactants (C12EOxPO3, where x represents EO chain lengths of 6 and 8, and C12 and PO3 indicate the dodecyl chain and single trioxypropylene chain, respectively) and Polyoxyethylene (EO) Alkyl Ether type nonionic surfactants (C12EOx, x = 6 and 8). These nonionic surfactants possess single EO and PO chain lengths without a distribution. An oil-in-water (O/W) type emulsion prepared using mixtures of nonionic surfactant C12EOxPO3 or C12EOx solutions and squalane was shown to be stable in the order of C12EO6PO3
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adsorption dynamics of homogeneous polyoxypropylene Polyoxyethylene Alkyl Ether nonionic surfactants at the air water interface
Journal of Molecular Liquids, 2018Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The dynamic surface tensions of two homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants with terminal hydroxy group (C12EOx, where C12 is a dodecyl chain and x is the length of the EO chain; x = 6, 8) and two homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether nonionic surfactants (C12EOxPO3, where PO3 is a trioxypropylene chain inserted between the EOx and the terminal hydroxy group) were measured using the maximum bubble pressure method. The effects of EO chain length, the presence or absence of the PO3 chain, and the surfactant concentration on the maximum rates of surface-tension reduction and diffusion coefficient were investigated. The C12EO6PO3 surfactant exhibited the fastest rate of surface-tension reduction of the four systems studied, despite its complex hydrophobic-Alkyl-chain/hydrophilic-EO-chain/hydrophobic-PO-chain structure that differs from that of conventional EO Alkyl Ether surfactants. The diffusion coefficients obtained from short and long time analyses indicate that surfactant diffusion to the subsurface is faster for the C12EOxPO3 surfactants than the C12EOx surfactants (short time data), while surfactant adsorption from the subsurface to the air/water interface is faster for the C12EOx surfactants than the C12EOxPO3 surfactants (long time data).
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Adsorption dynamics of homogeneous polyoxypropylene-Polyoxyethylene Alkyl Ether nonionic surfactants at the air/water interface
Journal of Molecular Liquids, 2018Co-Authors: Shiho Yada, Toshiyuki Suzuki, Satoru Hashimoto, Tomokazu YoshimuraAbstract:Abstract The dynamic surface tensions of two homogeneous Polyoxyethylene (EO) Alkyl Ether nonionic surfactants with terminal hydroxy group (C12EOx, where C12 is a dodecyl chain and x is the length of the EO chain; x = 6, 8) and two homogeneous polyoxypropylene-Polyoxyethylene (PO-EO) Alkyl Ether nonionic surfactants (C12EOxPO3, where PO3 is a trioxypropylene chain inserted between the EOx and the terminal hydroxy group) were measured using the maximum bubble pressure method. The effects of EO chain length, the presence or absence of the PO3 chain, and the surfactant concentration on the maximum rates of surface-tension reduction and diffusion coefficient were investigated. The C12EO6PO3 surfactant exhibited the fastest rate of surface-tension reduction of the four systems studied, despite its complex hydrophobic-Alkyl-chain/hydrophilic-EO-chain/hydrophobic-PO-chain structure that differs from that of conventional EO Alkyl Ether surfactants. The diffusion coefficients obtained from short and long time analyses indicate that surfactant diffusion to the subsurface is faster for the C12EOxPO3 surfactants than the C12EOx surfactants (short time data), while surfactant adsorption from the subsurface to the air/water interface is faster for the C12EOx surfactants than the C12EOxPO3 surfactants (long time data).
Yoshiyuki Einaga - One of the best experts on this subject based on the ideXlab platform.
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Wormlike micelles of Polyoxyethylene Alkyl Ether mixtures C10E5 + C14E5 and C14E5 + C14E7: hydrophobic and hydrophilic chain length dependence of the micellar characteristics.
Journal of Physical Chemistry B, 2007Co-Authors: Kiyoe Imanishi, Yoshiyuki EinagaAbstract:The wormlike micelles formed with the binary mixtures of surfactant Polyoxyethylene Alkyl Ethers (CiEj), C10E5 + C14E5 (Mix1) and C14E5 + C14E7 (Mix2), were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The SLS results have been analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass Mw(c) as a function of c along with the cross-sectional diameter d of the micelle. The observed Kc/ΔR0 as a function of c, the mean-square radius of gyration 〈S2〉 and the hydrodynamic radius RH as functions of Mw have been well described by the theories for the wormlike spherocylinder model. It has been found that the micellar length increases with increasing concentration c or with raising temperature T irrespective of the composition of the surfactant mixtures. The length of the Mix1 and Mix2 micelles at fixed c and T steeply increases with increasing weight fraction wt of C14E5 in both of the surfactant mixtures, implying that the micelles ...
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wormlike micelles of Polyoxyethylene Alkyl Ether mixtures c10e5 c14e5 and c14e5 c14e7 hydrophobic and hydrophilic chain length dependence of the micellar characteristics
Journal of Physical Chemistry B, 2007Co-Authors: Kiyoe Imanishi, Yoshiyuki EinagaAbstract:The wormlike micelles formed with the binary mixtures of surfactant Polyoxyethylene Alkyl Ethers (CiEj), C10E5 + C14E5 (Mix1) and C14E5 + C14E7 (Mix2), were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The SLS results have been analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass Mw(c) as a function of c along with the cross-sectional diameter d of the micelle. The observed Kc/ΔR0 as a function of c, the mean-square radius of gyration 〈S2〉 and the hydrodynamic radius RH as functions of Mw have been well described by the theories for the wormlike spherocylinder model. It has been found that the micellar length increases with increasing concentration c or with raising temperature T irrespective of the composition of the surfactant mixtures. The length of the Mix1 and Mix2 micelles at fixed c and T steeply increases with increasing weight fraction wt of C14E5 in both of the surfactant mixtures, implying that the micelles ...
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wormlike micelles of binary Polyoxyethylene Alkyl Ether mixtures c10e6 c14e6 and c14e8 c14e6
Polymer Journal, 2006Co-Authors: Yoshiyuki Einaga, Yumi Kito, Mikiko WatanabeAbstract:Wormlike Micelles of Binary Polyoxyethylene Alkyl Ether Mixtures C 10 E 6 + C 14 E 6 and C 14 E 8 + C 14 E 6
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Wormlike Micelles of Binary Polyoxyethylene Alkyl Ether Mixtures C_10E_6 + C_14E_6 and C_14E_8 + C_14E_6
Polymer Journal, 2006Co-Authors: Yoshiyuki Einaga, Yumi Kito, Mikiko WatanabeAbstract:The wormlike micelles formed with the binary mixtures of surfactant Polyoxyethylene Alkyl Ethers (C_ i E_ j ), C_10E_6 + C_14E_6 and C_14E_8 + C_14E_6, were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The observed Kc /Δ R _0 as a function of the surfactant concentration c have been successfully analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass M _w( c ) of the micelle as a function of c along with the cross-sectional diameter d of the micelle. The mean-square radius of gyration < S ^2> and the hydrodynamic radius R _H as functions of M _w have been well described by the theories for the wormlike spherocylinder model. The length of the micelles at fixed c and temperature T steeply increases with increasing weight fraction w _ t of C_14E_6 in both of the surfactant mixtures, implying that the micelles greatly grow in length when the surfactant component with longer Alkyl group or with shorter oxyethylene group increases in the mixture. The results are in line with the findings for the micelles of the single surfactant systems where the C_ i E_ j micelles grow in length to a greater extent for larger i and smaller j . Although the values of d do not significantly vary with composition of the surfactant mixture, the stiffness parameter λ^−1 remarkably decreases with w _ t in both of the mixtures, indicating that the stiffness of the micelle is controlled by the relative strength of the repulsive force due to the hydrophilic interactions between oxyethylen groups to the attractive one due to the hydrophobic interactions between Alkyl groups among the surfactant molecules.
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Wormlike micelles of binary Polyoxyethylene Alkyl Ether mixtures C10E6 + C14E6 and C14E8 + C14E6
Polymer Journal, 2006Co-Authors: Yoshiyuki Einaga, Yumi Kito, Mikiko WatanabeAbstract:Wormlike Micelles of Binary Polyoxyethylene Alkyl Ether Mixtures C 10 E 6 + C 14 E 6 and C 14 E 8 + C 14 E 6
L. Monticelli - One of the best experts on this subject based on the ideXlab platform.
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a coarse grained martini model of polyethylene glycol and of Polyoxyethylene Alkyl Ether surfactants
Journal of Physical Chemistry B, 2012Co-Authors: G. Rossi, P. F.j. Fuchs, J. Barnoud, L. MonticelliAbstract:Nonionic surfactants are used for the isolation and purification of membrane proteins, as well as for the study of fundamental aspects of protein diffusion in membranes. Here we present a new coarse-grained model of polyethylene glycol (PEG) and of the family of Polyoxyethylene Alkyl Ether (CiEj) surfactants. The model is compatible with the MARTINI coarse-grained force-field for lipids and proteins. We validate the model by comparing molecular dynamics simulations with experimental data. In particular, we show that the model reproduces the phase behavior of water–surfactant mixtures as a function of water concentration. We also simulate the self-assembly of two ternary mixtures that have been used for the experimental measure of protein diffusion coefficients. The first includes a cosurfactant that affects the curvature of the surfactant bilayers; the second is a mixture of CiEj surfactants, alkanes and water. In both cases, the results of self-assembly simulations are in agreement with experimental obse...
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A coarse-grained MARTINI model of polyethylene glycol and of Polyoxyethylene Alkyl Ether surfactants
Journal of Physical Chemistry B, 2012Co-Authors: G. Rossi, P. F.j. Fuchs, J. Barnoud, L. MonticelliAbstract:Nonionic surfactants are used for the isolation and purification of membrane proteins, as well as for the study of fundamental aspects of protein diffusion in membranes. Here we present a new coarse-grained model of polyethylene glycol (PEG) and of the family of Polyoxyethylene Alkyl Ether (C(i)E(j)) surfactants. The model is compatible with the MARTINI coarse-grained force-field for lipids and proteins. We validate the model by comparing molecular dynamics simulations with experimental data. In particular, we show that the model reproduces the phase behavior of water-surfactant mixtures as a function of water concentration. We also simulate the self-assembly of two ternary mixtures that have been used for the experimental measure of protein diffusion coefficients. The first includes a cosurfactant that affects the curvature of the surfactant bilayers; the second is a mixture of C(i)E(j) surfactants, alkanes and water. In both cases, the results of self-assembly simulations are in agreement with experimental observations and pave the way to the use of the surfactant model in combination with MARTINI peptides and proteins.
Hideki Sakai - One of the best experts on this subject based on the ideXlab platform.
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spontaneous emulsification of triolein induced by mixed micellar solutions of sodium Polyoxyethylene Alkyl Ether sulfate and dodecyldimethyl amine oxide
Journal of Oleo Science, 2015Co-Authors: Chika Endo, Chika Akabane, Yukihiro Kaneko, Hideki SakaiAbstract:A new mechanism of spontaneous emulsification without any salts or co-solvents is described, and is related to the dilatational behavior. Spontaneous emulsification can reduce the time required to remove oily soils from hard surfaces and enhance the detergency, because this type of emulsification requires no external mechanical work. In this paper, we focused on triolein, the main component of food oils and human sebum soil, and tried to induce spontaneous emulsification by using mixed micellar solutions of sodium Polyoxyethylene Alkyl Ether sulfate and N, N-dimethyldodecylamine oxide (AES/DDAO). We characterized the dilatation of the oil/water interface using dynamic interfacial tension and elasticity measurements. This study confirmed that the degree of spontaneous emulsification can be enhanced by controlling the molar ratio of DDAO to AES. This enhancement can be attributed to an increased rate of decrease in the dynamic interfacial tension (i.e., a decreased interface dilatational elasticity), allowing for much greater suppression of the Marangoni effect. Further, we determined that one of the reasons for the decrease in the interface dilatational elasticity is the increasing number of micelles near the oil drop interface, which results from a decrease in the electrostatic repulsion between the micelles and the drop interface. Therefore, controlling the molar ratio of a mixed anionic/amphoteric surfactant solution is an effective way to induce spontaneous emulsification in the absence of salts or co-solvents.
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Effect of Water on Interfacial Chemical Properties of Nonionic Surfactants in Hydrophobic Ionic Liquid bmimPF6
Journal of Oleo Science, 2013Co-Authors: Takeshi Misono, Kenichi Sakai, Takeshi Endo, Kenichi Aburai, Hideki SakaiAbstract:We studied the effect of water addition on interfacial properties and aggregate behavior of nonionic surfactants (Polyoxyethylene Alkyl Ether; CnEm) in an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate; bmimPF₆). When a small amount of water was added to mixtures of CnEm and bmimPF₆, two breaking points (cac1, cac2) were observed in the surface tension/CnEm concentration plots, suggesting the formation of two kinds of aggregates. This two-step aggregate formation was also confirmed by the fluorescence probe method using pyrene. The particle size of the aggregates measured by dynamic light scattering (DLS) was around 200 nm at cac1, and decreased to 4 nm above cac2. These results, togEther with freeze-fracture TEM observations, showed that the aggregate formed at cac1 was water in bmimPF₆ emulsions, which then transformed to micelles solubilizing water in the palisade layer above cac2. This concentration-dependent aggregate formation was supported thermodynamically by studying the dependence of cacs on temperature and Alkyl and POE chain lengths of the surfactant.
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Phytosterol Ethoxylates in Room-Temperature Ionic Liquids: Excellent Interfacial Properties and Gel Formation
Langmuir, 2009Co-Authors: Hideki Sakai, Koji Tsuchiya, Takeshi Endo, Takanori Saitoh, Kenichi SakaiAbstract:Physicochemical properties of phytosterol ethoxylates (BPS-n, where n is the oxyethylene chain length of 5, 10, 20, and 30) in a room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), have been characterized on the basis of static surface tension, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopic (cryo-TEM) data. The surface tension data clearly show that the BPS-n surfactants employed in this study exhibit the most excellent surface activity in BmimPF6 yet reported in the literature. The decreased chain length of the Polyoxyethylene unit results in a greater surface activity (i.e., lower critical association concentration (cac) and lower surface tension measured above the cac), as is similarly reported for nonionic Polyoxyethylene Alkyl Ether surfactants in aqueous solution. This suggests that the hydrophobic phytosterol groups are normally oriented toward the air phase, and the Polyoxyethylene chains ar...
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Phytosterol ethoxylates in room-temperature ionic liquids: Excellent interfacial properties and gel formation
Langmuir, 2009Co-Authors: Hideki Sakai, Kenichi Sakai, Teppei Saitoh, Koji Tsuchiya, Takeshi Endo, Masahiko AbeAbstract:Physicochemical properties of phytosterol ethoxylates (BPS-n, where n is the oxyethylene chain length of 5, 10, 20, and 30) in a room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), have been characterized on the basis of static surface tension, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopic (cryo-TEM) data. The surface tension data clearly show that the BPS-n surfactants employed in this study exhibit the most excellent surface activity in BmimPF6 yet reported in the literature. The decreased chain length of the Polyoxyethylene unit results in a greater surface activity (i.e., lower critical association concentration (cac) and lower surface tension measured above the cac), as is similarly reported for nonionic Polyoxyethylene Alkyl Ether surfactants in aqueous solution. This suggests that the hydrophobic phytosterol groups are normally oriented toward the air phase, and the Polyoxyethylene chains are present in the ionic liquid. Just above the cac, the BPS-n surfactants spontaneously form molecular assemblies in BmimPF6, depending on their critical packing parameters: less-curved vesicular assemblies are seen for BPS-10, whereas greater-curved (spherical) micelles are formed for BPS-20 and BPS-30. Indeed, an increased surfactant concentration results in a structural transformation of the molecular assemblies from micelles to discontinuous cubic, hexagonal, and lamellar structures. The current article explores the best combination of surfactants with ionic liquids to see excellent surface activity and characterize molecular assemblies in bulk solution.