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Shohei Aikawa,
Rekha Goswami Shrestha,
Takashi Ohmori,
Yuko Fukukita,
Yoji Tezuka,
Takeshi Endo,
Kanjiro Torigoe,
Koji Tsuchiya,
Kazutami Sakamoto, Kenichi Sakai,
Masahiko Abe,
Hideki Sakai
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ABSTRACT: Recently, we have reported a new cinnamic acid-type photo-cleavable surfactant, C4-C-N-PEG9 that experiences a photo-cleavage through UV-induced cyclization in aqueous solution, yielding a coumarin derivative and an aminated polyoxyethylene compound. Here, we have studied the effects of C4-C-N-PEG9 on the photorheological behavior of viscoelastic wormlike micelles formed by aqueous mixture of nonionic surfactants, polyoxyethylene phytosterol ether (PhyEO20) and tetraoxyethylene dodecyl ether (C12EO4). When C4-C-N-PEG9 is added to the viscous, non-Newtonian 4.9 wt% PhyEO20/H2O + 2.4 wt% C12EO4 fluid, a decrease in viscosity is observed, while upon UV irradiation C4-C-N-PEG9 added solution regains the viscosity. It increases by 200 times, suggesting a modulation in micellar shape and size. The UV-Vis spectroscopy and HPLC measurements confirm that the trans-C4-C-N-PEG9 with large head group and its photodecomposition to form less surface-active coumarin derivative and an aminated polyoxyethylene compound are responsible for different rheological behavior.
Langmuir 04/2013; · 4.19 Impact Factor
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ABSTRACT: Rheological properties of alkyl dicarboxylic acid-alkylamine complex systems have been characterized. The complex materials employed in this study consist of an amino acid-based surfactant (dodecanoylglutamic acid, C12Glu) and a tertiary alkylamine (dodecyldimethylamine, C12DMA) or a secondary alkylamine (dodecylmethylamine, C12MA). 1H-NMR and mass spectroscopic data have suggested that C12Glu forms a stoichiometric 1:1 complex with C12DMA and C12MA. Rheological measurements have suggested that the complex systems yield viscoelastic wormlike micellar solutions and the rheological behavior is strongly dependent on the aqueous solution pH. This pH-dependent behavior results from the structural transformation of the wormlike micelles to occur in the narrow pH range 5.5-6.2 (in the case of C12Glu-C12DMA system), i.e., positive curved aggregates such as spherical or rodlike micelles tend to be formed at high pH values. Our current study offers a unique way to obtain viscoelastic wormlike micellar solutions by means of alkyl dicarboxylic acid-alkylamine complex as gemini-like amphiphiles.
Langmuir 11/2012; · 4.19 Impact Factor
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ABSTRACT: Aqueous binary phase behavior of a peptide based gemini amphiphile with glutamic acid and lysine as spacer group, acylglutamyllysilacylglutamate, (m-GLG-m where m = 12, 14, and 16) has been reported over a wide range of concentration and temperature. Lauroylglutamyllysillauroylglutamate, 12-GLG-12 self-assembles into spherical micelles above critical micelle concentration (CMC). The micellar region extends upto 32 wt% and an ordering of spherical micelles into micellar cubic phase, I1 takes place at 33 wt% at 25 oC. The phase transition, I1 - hexagonal liquid crystal, (H1) - lamellar liquid crystal, (L has been observed with further increase in concentration, moreover mixed phases are also observed in between the pure liquid crystal domains. Similar phases were observed with 16-GLG-16 above 50 oC (Krafft temperature). The partial ternary phase behavior shows that the micellar solutions of m-GLG-m can solubilize a large amount of cationic amphiphile, alkyltrimethylammonium bromide, CnTAB, (where n = 14 (TTAB) and 16 (CTAB)) at 25 oC. An addition of CnTAB to the aqueous solutions of 16-GLG-16 in a dilute region forms a transparent solution of viscoelastic wormlike micelles at very low concentration (0.25 wt%) even at ambient condition. A mixture of oppositely charged amphiphiles, m-GLG-m and CnTAB exhibits synergism as a result the amphiphile layer curvature becomes less positive and favors sphere to rod to transient networks(wormlike micelles) transition. The gemini amphiphile, 16-GLG-16 forms wormlike micelles at relatively low concentrations compared to others reported so far. Viscosity increases by 6th orders of magnitude that of pure solvent. The hydrophobic chain length of m-GLG-m and coamphiphile effects the rheology; the maximum viscosity achieved with 16-GLG-16/H2O/CTAB is higher than 14-GLG-14/H2O/CTAB, 12-GLG-12/H2O/CTAB and 16-GLG-16/H2O/TTAB systems. These temperature sensitive systems exhibited viscoelastic behavior described by the Maxwell mechanical model with a single stress relaxation mode.
Langmuir 10/2012; · 4.19 Impact Factor
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ABSTRACT: We have studied the rheology and structure of a mixed long polyoxyethylene chain phytosterol (PhyEO30) and monoglyceride (monolaurin (ML) or monopalmitin (MP)) surfactants in an aqueous system. Both ML and MP are insoluble
in 10wt.% PhyEO30 solution at normal room temperature, but their solubility is found to increase with the rise of temperature and an isotropic
solution is formed at higher temperature. A maximum viscosity as a function of temperature appears as ML or MP is solubilized
in the micellar solution of PhyEO30. With increasing temperature, viscosity increases rapidly for higher monoglyceride content and forms viscoelastic solution.
The oscillatory rheological behavior of the viscoelastic solution can be described by Maxwell model at low-frequency region,
which is the typical pattern of entangled wormlike micelles. Upon successive increase in temperature, the viscosity decreases
and ultimately a phase separation occurs. Small-angle X-ray scattering measurements were performed to provide a supportive
structural evidence for the rheological data.
Colloid and Polymer Science 04/2012; 288(4):405-414. · 2.33 Impact Factor
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ABSTRACT: A simple glass capillary microflow reactor system has been applied for the synthesis of palladium nanoparticles by thermal
decomposition of palladium acetate (Pd(OAc)2) in diphenyl ether in the presence of poly(benzyl ether) dendron ligands (PBED Gn-NH2, n=1–3) as a stabilizer. Effect of hydrodynamic parameters (capillary diameter, linear flow rate, volume flow rate, and reaction
temperature) and concentrations (precursor and stabilizer) on the particle size was investigated. The particle size can be
controlled by varying linear flow rate and temperature as well as ligand/precursor concentration ratio. Volume flow rate does
not affect the particle size when the linear flow rate is held constant for different capillary diameters (150–320μm). Unlike
batch systems, in this microreactor system, smaller particles are produced at low ligand concentrations when the molar ratio
of the ligand to metal precursor ranged from 1 to 5. As another characteristic of the microreactor synthesis, the concentration
of the Pd precursor can be increased (up to 27mM) with maintaining a constant particle size (3.1±0.2nm) and a good monodispersity,
while in the batch system a significant increase and broadening in the particle size are observed with increasing precursor
concentration.
KeywordsMicroflow reactor-Palladium nanoparticles-Thermal decomposition-Dendron ligand-Microfluidics-Nanomanufacturing
Journal of Nanoparticle Research 04/2012; 12(3):951-960. · 3.29 Impact Factor
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ABSTRACT: The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.
Colloid and Polymer Science 04/2012; 284(1):74-79. · 2.33 Impact Factor
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Hideki Sakai,
Shohei Aikawa,
Wataru Matsuda,
Takashi Ohmori,
Yuko Fukukita,
Yoji Tezuka,
Atsutoshi Matsumura,
Kanjiro Torigoe,
Koji Tsuchiya,
Koji Arimitsu,
Kazutami Sakamoto, Kenichi Sakai,
Masahiko Abe
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ABSTRACT: We have developed a novel cinnamic acid-type photo-cleavable surfactant. This surfactant experiences photo-cleavage through UV-induced cyclization in aqueous solutions. The photo-cleavage not only reduces its capabilities as a surfactant but also yields two functional materials including a coumarin derivative and an aminated polyoxyethylene compound. This means that the photo-cleavable surfactant synthesized in this study is a photo-responsive function-exchangeable material. In our current study, we have characterized the photo-cleavable behavior that occurs in aqueous solutions and a resulting change in interfacial properties. The photo-cleavage induces an increased interfacial tension of a squalane/water interface and a decreased solubilization capability of the surfactant micelles.
Journal of Colloid and Interface Science 03/2012; 376(1):160-4. · 3.07 Impact Factor
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ABSTRACT: A toluene-polyethylene (PE) mixture, only partially miscible at room temperature (RT), was ultrasonically dispersed in hot water, followed by immediate cooling to give a highly stable surfactant-free oil-in-water (O/W) emulsion. This temperature effect was correlated with physical gelation of the bulk mixture. Prolonged stabilization was achieved only through dispersion at a temperature (T(d)) above the gelation temperature (T(gel)) of the toluene-low-density PE (LDPE) mixture and subsequent rapid cooling. These stabilized emulsions exhibited characteristics such as a small droplet size with a narrow size distribution, low ζ-potential, and round-shaped droplets, which were not observed for the emulsions prepared at T(d) < T(gel) or those at T(d) > T(gel) that had been subjected to slow cooling. From these results, physical gelation through crystallization and modification of the droplet surface by PE were concluded to be essential for the prolonged stability of a surfactant-free toluene emulsion.
Journal of oleo science 01/2012; 61(2):57-63. · 1.42 Impact Factor
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ABSTRACT: The temperature-concentration phase behavior of nonionic surfactants in an aprotic imidazolium-type room-temperature ionic liquid (RT-IL) was evaluated on the basis of a combination of visual appearance, polarized optical microscopy, and small angle X-ray scattering data. Phytosterol ethoxylates (BPS-n, where n denotes oxyethylene chain lengths of 5, 10, 20, and 30) were used as surfactants in the RT-IL, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆). The two component mixtures yielded various phases such as discontinuous cubic, hexagonal, and lamellar phases. An increased tendency toward formation of lesser-curved molecular assemblies was observed at higher BPS-n concentrations, at lower temperatures, and for shorter oxyethylene chain surfactants. These trends are similar to those observed in aqueous BPS-n systems; however, notable differences in the phase states of the aqueous system versus the BmimPF₆ system were evident. Comparison with the water system showed that the BmimPF₆ system yielded fewer phases and generally required higher BPS-n concentrations to induce phase transitions. Evaluation of the effects of addition of a third component (e.g., 1-dodecanol and dodecane) to the binary system on the phase behavior showed that at a given composition ratio of BPS-20 to BmimPF₆, the addition of 1-dodecanol generally results in the phase transition to lesser-curved assemblies whereas dodecane generated no significant effects. The observed phase change is satisfactorily rationalized by localized solubilization of the third component into the binary surfactant assemblies.
Journal of oleo science 01/2012; 61(3):135-41. · 1.42 Impact Factor
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ABSTRACT: Discreetness of a cell is the key to life, with the cell
membrane separating the interior cytosol from its environment.
In this regard, cytosol is never connected to the external media
even during the course of cell fission or fusion. However, watersoluble
peptides called protein transduction domain (PTD) can
spontaneously translocate through the cell membranes without
any particular transporter or receptor. Here, we propose that the
translocation of PTD can be described based on a local and
temporal dynamic topological transformation of the membrane
structure to mesh phase.
Chemistry Letters 01/2012; 41:1078. · 1.59 Impact Factor
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ABSTRACT: In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO(20)) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The ChEO(20) self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η(0)) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η(0 max)) increased with the increasing ChEO(20) mixing fraction with water. We observed that η(0 max) increased by 2 to 4 orders of magnitude as a function of the ChEO(20) concentration. The Maxwell relaxation time (τ(R)) shows a maximum value at a concentration corresponding to η(0 max) (i.e., τ(R) increases with L-02 concentration and then decreases after attaining a maximum value, whereas the plateau modulus (G(0)) shows monotonous growth). These observations demonstrate microstructural transitions in two different modes: L-02 first induces 1-D micellar growth and as a result the viscosity increases, and finally after the system attains its maximum viscosity, L-02 causes branching in the network structures. The microstructure transitions are confirmed by SAXS and cryo-TEM techniques.
Langmuir 09/2011; 27(21):12877-83. · 4.19 Impact Factor
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ABSTRACT: Surface adsorption and aggregation behavior of polyoxyethylene (POE)-type nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)), were investigated by means of surface tension, (1)H NMR, and dynamic light-scattering (DLS) measurements. The maximum surface excess in bmimPF(6) is much lesser than those observed for aqueous solution, reflecting a much weaker solvophobicity exhibited by the surfactant hydrocarbon chain in the ionic liquid compared with the hydrophobicity experienced in water. Compared with another ionic liquid with different anion species, 1-butyl-3-methylimidazolium terafluoroborate (bmimBF(4)), the surfactant solution in bmimPF(6) brings about higher critical micelle concentration (cmc), smaller micellar aggregation number, and weaker dependence of cmc on the surfactant hydrocarbon chain length. This indicates that the solvophobic interaction between surfactant hydrocarbon chains acts more weakly in bmimPF(6) than in bmimBF(4). The weaker solvophobic effect in bmimPF(6) is also appreciable in the thermodynamic parameters for micelle formation derived from temperature dependence of cmc, and would be attributed to weaker attractive interaction between bmim cation and PF(6)(-) ion compared with that between bmim cation and BF(4)(-) ion. Present results give an insight into a better understanding of the importance of anion species for the properties of ionic liquids as a solvent to support a self-assembly of amphiphilic molecules.
Journal of Colloid and Interface Science 06/2011; 358(2):527-33. · 3.07 Impact Factor
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ABSTRACT: Polyoxyethylene cholesteryl ether (ChEO(20)) nonionic surfactant self-assembles into spherical micelles above the critical micelle concentration in water. An ordering of micelles takes place with an increase in surfactant concentration and forms a micellar cubic phase with the space group Pm3n at ∼30%. Cocamid methyl MEA (designated as C-11S) cosurfactant is soluble at the palisade layer of the ChEO(20) micelle as a result; the curvature of the aggregates tends to decrease and favors sphere-to-rod transition. The axial length of the rod increases with C-11S concentration, and after a certain concentration, elongated micelles entangle with each other, forming a transient network of wormlike micelles. Viscosity increases by 5 orders of magnitude. The zero-shear viscosity (η(0)) versus C-11S concentration curve shows a peak, and the position of the peak shifts toward the right (at higher concentration of C-11S) when the concentration of ChEO(20) in water is increased from 10 to 15%. On the other hand, the peak position shifts toward the left with a decrease in the ethylene oxide (EO) chain of the surfactant, i.e., in the ChEO(15) system. Viscosity increases only slightly with a longer EO chain ChEO(30) system, and it does not show any viscoelastic properties. These wormlike micelles exhibited viscoelastic behavior and could be described by the Maxwell mechanical model with a single stress relaxation mode that is sensitive to temperature. Viscosity and relaxation time were first increased and then decreased, but the plateau modulus increased continuously upon heating. These observations revealed that micelles first grew with temperature and then branched. Dynamic rheology and small-angle X-ray scattering (SAXS) further support the rheology data.
The Journal of Physical Chemistry B 03/2011; 115(12):2937-46. · 3.70 Impact Factor
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ABSTRACT: Photochemical control of vesicle disintegration and reformation in aqueous solution was examined using a mixture of 4-butylazobenzene-4'-(oxyethyl)trimethylammonium bromide (AZTMA) as the photoresponsive cationic surfactant and sodium dodecylbenzenesulfonate (SDBS) as the anionic surfactant. Spontaneous vesicle formation was found in a wide-ranging composition of the trans-AZTMA/SDBS system. AZTMA molecules constituting vesicles underwent reversible trans-cis photoisomerization when irradiated with ultraviolet and visible light. Transmission electron microscopy observations using the freeze-fracture technique (FF-TEM) showed that UV light irradiation caused the vesicles to disintegrate into coarse aggregates and visible light irradiation stimulated the reformation of vesicles (normal control). A detailed investigation of the phase state and the effects of UV and visible light irradiation on the AZTMA/SDBS system with the use of electroconductivity, dynamic/static light scattering, and surface tension measurements and FF-TEM observations revealed that in the AZTMA-rich composition (AZTMA/SDBS 9:1) a micellar solution before light irradiation became a vesicular solution after UV light irradiation and visible light irradiation allowed the return to a micellar solution (reverse control). Thus, we could photochemically control the disintegration (normal control) and reformation (reverse control) of vesicles in the same system.
Langmuir 03/2011; 27(5):1610-7. · 4.19 Impact Factor
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ABSTRACT: The adsorption of a nonionic surfactant at a silica/room-temperature ionic liquid interface has been characterized on the basis of analytical data obtained through a combination of surface force measurements, in situ soft-contact atomic force microscope (AFM) images, and quartz crystal microbalance with dissipation monitoring (QCM-D) data. The surfactant employed in this study is a kind of phytosterol ethoxylate (BPS-20), and the ionic liquid selected here is aprotic 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI). This ionic liquid spontaneously forms solvation layers on silica, being composed of an Emim(+) cation layer and EmimTFSI ion pair layers. The addition of BPS-20 disrupts these solvation layers and suggests a surfactant layer adsorbed at the interface. This is the first report demonstrating the adsorption of nonionic surfactants at the solid/aprotic ionic liquid interface.
Langmuir 03/2011; 27(7):3244-8. · 4.19 Impact Factor
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ABSTRACT: Gemini surfactants recently developed by our research group are introduced from the standpoints of their syntheses, aqueous solution properties, and potential applications. Two series of gemini surfactants are introduced in this short review, the first of which is the oleic acid-based gemini surfactants, and the second is the polymerizable gemini surfactants. These gemini surfactants have been developed not only as environmentally friendly materials (the use of gemini surfactants enables the reduction of the total consumption of surfactants in chemical products owing to their excellent adsorption and micellization capabilities at low concentrations) but also as functional organic materials.
Journal of oleo science 01/2011; 60(4):159-63. · 1.42 Impact Factor
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ABSTRACT: The membrane properties of phospholipid mixtures supported on silica were studied by means of a quartz crystal microbalance with dissipation monitoring (QCM-D) technique, in situ soft-contact atomic force microscopy (AFM), and friction force microscopy (FFM). The phospholipids used in this study were di-stearoylphosphatidylcholine (DSPC) and dilauroylphosphatidylcholine (DLPC). The phospholipid films were prepared by a vesicle-fusion method, in which DSPC/DLPC mixed liposomes dispersed in an aqueous medium are adsorbed on silica and their structure is transformed into a bilayer on the substrate. The changes in QCM-D (frequency and dissipation) and friction responses of DSPC single systems (gel state at 25°C) are relatively large compared with those of DLPC single systems (liquid-crystalline state at 25°C) and those of mixed DSPC/DLPC systems. This suggests that (i) the gel-state DSPC liposomes are somewhat flattened on the silica, by keeping their solid-like molecular rigidity, whereas (ii) both the liquid-crystalline DLPC and mixed liposomes experience instantaneous structural transformation at the silica/water interface and form a normally flattened bilayer on the substrate. The friction force response is dependent on the phase state of the phospholipids, and the liquid-crystalline DLPC has a more significant impact on the overall membrane properties (i.e., the degree of swelling and the friction response on the surface) than does the gel-state DSPC.
Journal of oleo science 01/2011; 60(4):177-83. · 1.42 Impact Factor
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ABSTRACT: This article reports the preparation and properties of nanosized biodegradable polymer capsules synthesized using the electrocapillary emulsification method. The biodegradable polymers used were poly(ε-caprolactone) (PCL), which is a highly biodegradable and biocompatible polymer, and poly(lactide-co-glycolic acid) (PLGA). While the size of the capsules prepared using PCL alone was in the micrometer range, it decreased with an increase in the amount of PLGA added to PCL and eventually reached the nanometer level. When the electrocapillary emulsification applied potential was 2000 V, the sizes of the capsules (PCL:PLGA = 5:5) ranged from 50 to 80 nm. The percentage of glucose trapped in the PCL/PLGA nanocapsules was higher than 80% and the duration of glucose release from the nanocapsules was about two times longer than that from PCL capsules.
Journal of oleo science 01/2011; 60(11):569-73. · 1.42 Impact Factor
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ABSTRACT: The adsorption and aggregation behaviors of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) on a hydrophobic graphite surface were examined using a novel molecular dynamics (MD) simulation with the periodic-shell boundary condition (PSBC). Differences in the adsorption behavior of SDS and CTAB molecules were clearly shown on the hydrophobic surface. Unexpectedly, the SDS molecules approached the graphite surface with their hydrophilic head groups. This unexpected approach mode was thought to be due to the aqueous layer on the graphite surface. The hydrophobic moiety of SDS molecules repeatedly adsorbed and desorbed on the graphite surface. In addition, SDS molecules kept moving on the graphite surface; thus, they did not form a stable adsorption layer. In contrast to SDS, the hydrophobic moiety of CTAB molecules approached the graphite surface at the primary step of adsorption. The hydrophobic moieties of CTAB molecules came close to each other, whereas the hydrophilic groups separated from one another. This result suggests that the CTAB molecules form molecular assemblies with a curved structure. The simulation results were consistent with the experimental observations. A clear difference between the adsorption behavior of SDS and CTAB molecules was revealed by MD simulations with PSBC.
Journal of oleo science 01/2011; 60(4):171-6. · 1.42 Impact Factor
