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Herein, we report the synthesis and interfacial properties of cholesterol based biocompatible surface-active biosurfactant choline cholate (CC) and choline deoxy cholate (CDC) surfactants, prepared through salt metathesis reaction. The surface activity and aggregation behavior of these surfactants were investigated by surface tension measurements and small angle X-ray scattering (SAXS) technique. CC and CDC both formed well-defined micelles with distinct CMC values as indicated by tensiometry, while the SAXS patterns can be well described by the polydisperse ellipsoid model. Furthermore, it was observed that both CC and CDC showed good foamability ascribed to the foam film rigidity which could be highly beneficial. Also, CC and CDC showed sphere-to rod micellar transition in the presence of CTAB. The study reported here may prove to be highly beneficial for pharmaceutical and personal care product formulations.

Fe−Pt alloy nanoparticles (NPs) with dendritic shells are efficaciously created by the chemical reduction of K2PtCl4 and FeCl3 species in a low-concentration of nonionic surfactant polyoxyethylene cholesteryl ether (ChEO15) solution. The dissimilarity in reduction potentials of the two soluble metal salts (Fe(III) and Pt(IV) species) plays a crucial role in the one-step synthesis of the bimetallic nanostructure, which is confirmed by TEM and XRD. Interestingly, Fe−Pt alloy NPs exhibit oxidase enzyme-like activity as well as a chemical catalyst. The kinetic parameters calculations revealed that this catalyst enhances the velocity of reaction 10 folds when compared with the reported oxidase-like activity exhibiting nanomaterials. The Fe-Pt alloy NPs also displayed high catalytic activity in the hydrogenation reaction of nitrophenol to aminophenol. The safety assessment of Fe-Pt alloy NPs revealed that these NPs are highly biocompatible to human normal liver cells up to 150 μM concentration. Therefore, the synthesized Fe-Pt alloy NPs showing excellent oxidase enzyme-like activity hold the promise to be used for multiple biomedical applications.

The micellization and foam studies of binary surfactant mixtures assembled of nonionic polyoxyethylene cholesteryl ether (ChEOn; where n = 30), cationic hexadecyltrimethylammonium bromide (CTAB) and anionic sodium dodecylbenzenesulfonate (SDBS) was investigated by surface tension, foaming behavior and viscosity measurements. As an exceptional outcome it was observed that foam stability and foamability of nonionic surfactant ChEO30 in mixtures with ionic surfactants is much superior to the individual ChEO30, CTAB or SDBS components. Moreover, the mixed surfactant systems (ChEO30+CTAB) and (ChEO30+SDBS) have much lower critical micellar concentrations (CMCs) than corresponding sole surfactants. The negative values of interaction parameter (β) estimated from Rubingh’s theory specify synergism amongst mixed ChEO30+CTAB and ChEO30+SDBS surfactants systems.

Nanocomposite hydrogels (NC gels) with polymer–clay network assemblies are useful in a number of applications because of their unique properties and characteristics. Herein, we describe a distinctive strategy for the preparation of discrete monometallic (Ag, Au, and Pd) and bimetallic (Pt-Pd, Au-Pd) nanoparticles that uses a nanocomposite hydrogel composed of a polymer–clay network. Thermoresponsive NC gels were synthesized by the in-situ free-radical polymerization of N-isopropylacrylamide in the presence of clay (synthetic hectorite) nanosheets (CNSs). Since CNSs have strong affinities for metals ions that facilitate the concentration of metal precursors around them, the reduction of metal ions by ascorbic acid in NC gels provides well-dispersed, non-aggregated spherical monometallic and bimetallic nanoparticles (NPs) that are strongly immobilized within the polymer-clay network. The resulting hybrid NP-NC gels, which contain monometallic or bimetallic NPs, exhibit high catalytic activities for the hydrogenation of nitrophenol to aminophenol. The combination of well-defined metal NPs and mechanically tough NC gels opens up new possibilities for the design of environmentally friendly and sustainable functional NP-NC-gel materials.

Microemulsions are unique clear systems comprising of oil, water, surfactant and cosurfactants that offered stimulating perspectives in various applications. The purpose of these study was to create a microemulsion using novel amino acid based anionic sodium N-lauroylsarcosinate (SNLS) surfactant for application in personal care formulations. Triglyceride oils such as caprylic acid, oleic acid and carboxylic acid ester isoamyl acetate were used as oil phase, while short chain alcohols like propanol and butanol were used as cosurfactants. The gradual variations happening in the microstructure of the microemulsions were explored via several complementary characterization techniques. Phase diagrams constructed with or without cosurfactants and using different ratio of surfactant/ cosurfactant (Smix) showed that largest microemulsion region was observed only in the presence of cosurfactant and from Smix of 1:1. Solubility of SNLS in pure water is around 30 wt%, which upsurges in presence of propanol or butanol up to around 85 wt%. This leads to increase in microemulsion region in phase diagram with increasing solubility of oils in the SNLS solution. Microemulsions were relatively stable at an ambient temperature of 27 °C. The optical microscopy, electrical conductivity and viscosity measurement were performed to examine the microstructural changes within the microemulsion region. Three different phases such as water in oil (w/o), bicontinuous, and oil in water (o/w) microemulsion were observed. Foaming behavior specifies increased foam stability of SNLS in the presence of certain amount of oils. Dynamic light scattering study supports the well-defined microemulsion stability even after the manifold dilution. The results obtained from this study may have implications for the developments of an appropriate tactic to prepare stable microemulsion from SNLS which could be exceedingly favorable for personal care formulations.

Hemiesters and Hemiamides of maleic and succinic acid viz. sodium lauryl succinate (C12SE), sodium lauryl maleate (C12ME), sodium lauryl succinamide (C12SA), sodium lauryl maleamide (C12MA), sodium hexadecyl succinate (C16SE) and sodium hexadecyl maleate (C16ME) were synthesized and investigated as surfactants in the pure water and aqueous hydrotrope [sodium p-toluene sulfonate (NaPTs)] solution. The chemical structures of the prepared surfactants were established by FTIR and 1H NMR spectroscopy. The surface tension measurements depicted low CMC and a high adsorption efficiency (pC20) which is highly beneficial for creating personal care formulations. The dynamic light scattering (DLS) technique indicated the formation of larger micelles which was important for skin care as larger micelles cannot penetrate the skin layer. Moreover, these surfactants depicted good foamability and stability attributed to faster monomer adsorption and small bubble size which was preferred for cleansing application. Additionally, low protein/lipid solubilization by these surfactants indicated its mild behaviour on skin as compared to other commonly used conventional anionic [sodium lauryl sulfate (SLS)], zwitterionic [cocamidopropyl betaine (CAPB)] and nonionic [decyl glucoside (DG)] surfactants. Viscosity measurements suggested decent thickening ability of surfactants in the presence of co-surfactant like lauramine oxide. Basis of all the properties discussed, these novel hemiesters and hemiamides seem promising as surfactants for improving various characteristics in potential personal care formulations.

We report a simple and spontaneous method for creation of extremely stable and catalytically active gold nanoparticles (AuNPs) from polyoxyethylene cholesteryl ether (ChEO15) and sodium tetrachloroaurate (III) dihydrate (Na[AuCl₄] · 2H₂O). AuNPs with uniform size and distribution were prepared at 27 °C (AuNPs were formed in

In aqueous anionic sodium lauryl ether sulfate (SLES) solution, presence of nonionic cocamide monoethanolamine (CMEA) depicts intriguing interfacial and bulk properties. CMEA has poor water solubility but can be readily solubilized in SLES solution to form mixed micellar aggregates as revealed by surface tension measurements. Sphere-to-rod micellar transition in aqueous SLES-CMEA binary mixtures occurs at higher surfactant concentration (total surfactant concentration beyond 15 wt%), inducing a sharp growth in the viscosity (>1000 cP). Nevertheless, adding NaCl in SLES-CMEA mixtures, substantial growth in viscosity is perceived at much lower surfactant concentration (~5–10 wt%) attributed to the formation of intertwined worm-like micelles. Micellar sizes were obtained by dynamic light scattering (DLS) measurements and small-angle neutron scattering (SANS) investigations is used to determine micellar shapes and aggregation number for SLES-CMEA mixtures. Furthermore, it is observed that foaming behavior of SLES can be modulated by CMEA ascribed to the change in foam film rigidity. Corresponding experiments were also performed with nonethoxylated counterpart sodium lauryl sulfate (SLS) under analogous condition for comparison. The study reported here may prove to be an appropriate tactic to alter not only the rheology or foaming behavior of SLES-CMEA mixed surfactant system but also provide pre-solubilized composition of CMEA which could be highly beneficial for personal care products enabling CMEA blending at room temperature, which otherwise needs high temperature mixing.

This work reports the aqueous foaming behavior of the synthesized quaternary ammonium-based conventional and Gemini surfactants (GS) varying in degree of hydrophobicity. Foamability and its stability results revealed the significance of the surfactant’s hydrocarbon chain length in tuning its interfacial performance. The micellization breakpoint i.e., the critical micelle concentration (CMC), the surface activity descriptors of each surfactant were evaluated from tensiometry method at 303.15 K. Microscopic studies revealed the time dependency on the foam stability of 12-2-12 as a utility of its concentration greater than its CMC i.e., 1*CMC and 5*CMC. In addition, the dynamic rheological properties like viscosity and viscoelasticity (storage modulus, G' and loss modulus, G") of 12-2-12 were measured as a function of its concentration (1*CMC, 3*CMC, and 5*CMC) which depicted pseudo-plastic behavior. To explore the influence of shear rate, the Power-law model for foam viscosity was employed and observed to be a strong function of GS concentration. Furthermore, the oil-in-water study demonstrated the improved stabilization in the presence of GS, more evident from increasing zeta potential values of 12-2-12 than 12-2-16 and 16-2-16. The interfacial tension (IFT) study of GS for 5*CMC at the oil-aqueous interface was also commenced using several n-alkanes (n-heptane, n-decane, n-dodecane, and n-tetradecane) to make it more practicable for the industrial applications.

The self-healing materials from thermoplastic polymer composites reveal outstanding properties. They impart distinctive advantages over traditional polymers with monotonous chain structures, and cure damage by itself (without human intervention) prompted by thermal (fatigue) and mechanical (fracture, corrosion) means with its intrinsic character of self-healing from injury as inspired from nature. This increases the lifetime and safety of materials with less maintenance. Moreover, it could be an interesting field of research for developing competitive materials with biomimetic properties whose opportunities include electronics, energy, armor, and space applications. This chapter addresses the various approaches of healing mechanism, brief discussion about critical issues and challenges during autonomic self-repair process and concludes with some significant work undergone in various thermoplastic polymer composites.

The production and utilization of biopolymer composites in conversion of waste heat to electrical energy customized to sustainable development which emphasize the importance of natural-based resources over conventional fossil–fuels–based polymers due to its less carbon footprints. Although biopolymer possesses some inferior properties, the overall performance can be significantly enhanced by different stages of modification through blending, doping, or plasticization with other materials which can be utilized in making thermoelectric devices. This chapter features the importance and advantages of biopolymers in energy production, routes to modify biopolymers to biopolymer composites with enhanced properties to achieve good conductive materials and concludes with some selected composites for thermoelectric applications.

The impact of small nonionic hydrophobic molecule, trioxyethylene monododecyl ether (C12EO3), on the viscoelastic properties of aqueous solutions of cetylpyridinium chloride (CPC) is studied. As the C 12 EO 3 concentration increases, the viscosity passes through a maximum. Dynamic rheological measurements revealed a comprehensive picture of how C 12 EO 3 affects the different length scales in the entangled wormlike micelles. Increase in the viscosity can normally be caused by insertion of amphiphilic C 12 EO 3 molecules into the cationic surfactant (CPC) layer, or micellar swelling, caused by solubilization of very hydrophobic molecules in the micellar core. The partial phase behavior and rheology of this mixed surfactant systems is studied.

Pt nanoparticles (Pt NPs) are currently used in many areas of nanoscience and technology. Numerous studies have been reported on the design of Pt and Pt-based nanomaterials with different sizes, shapes, and compositions. Here, we report the synthesis, structure, and properties of a novel hydrogel-based nanostructured Pt material, Pt-NC gel, consisting of ultrafine Pt NPs strongly immobilized within a unique polymer−clay network. Pt-NC gels were synthesized through exfoliated clay-mediated in situ reduction of Pt ions in the NC gel at ambient temperature. Pt NPs were trapped on the clay surface, probably at the edges of the clay nanoplatelets. Ultrafine Pt NPs were also obtained as a stable suspension from the NC gel, without any stabilizing agents. The combination of ultrafine Pt NPs and mechanically tough NC gel may open up new possibilities for designing functional Pt-gel materials.

Clay (synthetic hectorite; Laponite XLG) plays a very crucial role in the formation and stabilization of core-shell nanocrystals and affords high stability, large BET surface area and stimulates the exceptional catalytic activity of the core-shell NCs.

We demonstrate the striking potential of exfoliated clay (synthetic hectorite; Laponite XLG) platelets to prepare bimetallic (Co-Pt and Ni-Pt) NCs with well-defined structures. Catalytic studies show a strong bimetallic synergistic effect of the core-shell NCs; their catalytic activities are much higher than those of monometallic NCs and other bimetallic core-shell NCs.

Nanostructured novel Pt/Clay nanocomposites consisting of well-defined Pt nanoparticles prepared by clay-mediated in situ reduction displays very high thermal stability, large BET surface area and superior catalytic activity for CO oxidation as compared to a model reference Pt/SiO2 catalysts. CO oxidation has attracted renewed attention because of its technological importance in the area of pollution control. The Pt/Clay system consisting of Pt nanoparticles strongly immobilized between the atomic layers of clay inhibits nanoparticle sintering and loss of catalytic activity even after prolonged heating at high temperatures. At elevated temperatures (300 °C), the Pt/Clay system demonstrates significant enhancement of catalytic activity, with almost 100% CO conversion in less than 5 min. Emphasis is given to the role played by the clay supporting material which is chemically and thermally stable under the catalytic conditions of exhaust purification.

Novel and intriguing one-pot in situ method for the preparation of nanostructured Pt-clay materials under simple conditions is reported. In this synthesis, an inorganic clay mineral such as synthetic hectorite ("Laponite XLG") or natural montmorillonite ("Kunipia F") serves as a mild and effective reducing agent for Pt ions, which is uncommon for such a clay system, and also acts as an outstanding stabilizer for the resulting Pt nanoparticles. In aqueous solution, exfoliated colloidal clay platelets forms complex with Pt ions in the initial stage of mixing. Devoid of any organic dispersants or external reducing agents, subsequently, the Pt nanoparticles (3-6 nm) generated by clay-assisted in situ reduction of Pt ions successfully anchored onto the clay nanoplatelets. The Pt-clay material features a very high surface area (312 m(2) g(-1)) and has excellent catalytic activity, as was kinetically evaluated via the reduction of 4-nitrophenol with NaBH(4). After drying, this remarkably stable nanocomposite is completely redispersible in water and displays extreme thermal stability (up to 500 °C). On the basis of these results, this synthetic strategy is anticipated to be a very simple, economical, and green approach for the synthesis of nanostructured Pt-clay materials.

The mixed surfactant systems of anionic sodium dodecyl trioxyethylene sulfate (SDES) and gemini surfactants (cationic) of the series N,N’-bis-(dimethyldodecyl)-α,ω-dialkanediammoniumdibromide, 12-s-12 (s = 2, 4, 6) at different molar ratios were studied by surface tension measurements of aqueous solution as a function of total concentration under standard condition. Various parameters like critical micelle concentration (CMC), surface excess concentration (Гmax), minimum area per molecule (Amin), interaction parameter of mixed micelle and adsorption monolayer (βm, βo) as well as thermodynamic and micellar properties have been determined using Clint, Rubingh, Maeda and Rosen approach. The strong interaction showing very low CMC and large negative interaction parameter β were due to weakening of the electrostatic head group repulsion which favors the mixed micelle formation. The results are discussed in terms of the structural characteristics and spacer chain of gemini surfactants and also in terms of the presence of EO group in SDES molecule. Gemini surfactants bind tightly with SDES by electrostatic, hydrophobic and ion–dipole interactions. Thermodynamic parameters for all three cationic–anionic mixed systems were evaluated. From excess free energy of micellization we can conclude that thermodynamically stable micelles are formed with strong synergistic interaction.

Mixtures of a hydrophobic triblock copolymer (L121, PEO5PPO68PEO5) and a hydrophobic anionic surfactant (AOT, Sodium bis(2-ethylhexyl)sulfosuccinate), each alone forming turbid vesicular solutions in water, aggregate to produce a thermodynamically stable, transparent and isotropic solution. Mixed AOT/L121 aggregates could be confirmed by fluorescence, surface tension, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). In an isotropic region, where mixed aggregates are formed, there is a synergistic interaction between monomers of AOT and L121 in the mixture. In addition, Small Angle Neutron Scattering (SANS) experiments provided evidence that mixed aggregates have the shape of either spheres (with a certain polydispersity) or very short ellipsoids (axial ratio below 2), confirming a transition from giant multilamellar vesicles to small aggregates upon mixing the two hydrophobic amphiphiles. Upon dilution, the morphology changes to disk-like. From an examination of the results of all the methods the peculiar behavior of the mixed AOT/L121 system is explained.

Mixtures of a hydrophobic triblock copolymer (L121, PEO5PPO68PEO5) and a hydrophobic anionic surfactant (AOT, Sodium bis(2-ethylhexyl)sulfosuccinate), each alone forming turbid vesicular solutions in water, aggregate to produce a thermodynamically stable, transparent, and isotropic solution. Mixed AOT/L121 aggregates could be confirmed by fluorescence, surface tension, differential scanning calorimetry (DSC), and isothermal titration calorimetry. In an isotropic region, where mixed aggregates are formed, there is a synergistic interaction between monomers of AOT and L121 in the mixture. In addition, small-angle neutron scattering experiments provided evidence that mixed aggregates have the shape of either spheres (with a certain polydispersity) or very short ellipsoids (axial ratio below 2), confirming a transition from giant multilamellar vesicles to small aggregates upon mixing the two hydrophobic amphiphiles. Upon dilution, the morphology changes to disk-like. From an examination of the results of all the methods the peculiar behavior of the mixed AOT/L121 system is explained.

Formation of reverse micelles in surfactant/oil binary systems without water addition and the tunable parameters for the structure control of such micelles are presented. The small-angle X-ray scattering (SAXS) technique has been used for the structural characterization of micelles. It has been found that the nonionic surfactant glycerol monoisostearate (abbreviated as iso-C18G1) forms reverse micelles in different organic solvents such as cyclohexane, n-decane, and n-hexadecane without the addition of water. The structure (shape and size) of the reverse micelles has been found to depend on the solvent nature (alkyl chain length of oil), composition, temperature, and added water. Phase behavior study has shown that iso-C18G1 forms isotropic single-phase solutions in the aforementioned oils at 25 degrees C. At lower temperatures (20 degrees C) II phases (dispersion of solid or liquid crystal phase) has been observed. SAXS data were evaluated by the generalized indirect Fourier transformation (GIFT) method, which has drawn a clear picture on the structural variations of the reverse micellar aggregates. Small globular types of micelles are found in the iso-C18G1/cyclohexane system. On the other hand, elongated ellipsoidal prolatelike or rodlike micelles are found in iso-C18G1/decane or iso-C18G1/hexadecane systems. The underlying mechanism of this structural evolution may be explained in terms of the transfer free energy of hydrophilic glycerol moiety from hydrophilic to hydrophobic environment of oils with different chain lengths. Besides, the penetration of oils to the lipophilic chain of the surfactant in reverse micellar systems differs depending on the chain length of oils. Lowering temperature and increasing surfactant concentration similarly lead to micellar growth while the cross-section structure remains essentially unchanged. Addition of trace water induced micellar growth, which is accompanied by the rapid swelling of the micellar core. The results obtained by this study demonstrate that the solvent nature, temperature, composition, and water addition can be the tunable parameters for the size, shape, and internal structure control of the iso-C18G1-based reverse micelles.

A highly viscoelastic worm-like micellar solution is formed in hexadecyltrimethylammonium bromide (CTAB) in the presence of sodium nitrate (NaNO3). A gradual increase in micellar length with increasing NaNO3 was assumed from the rheological measurements where the zero-shear viscosity (η 0) versus NaNO3 concentration curve exhibits a maximum. However, upon increase in temperature, the viscosity decreases. Changes in the structural parameters of the micelles with addition of NaNO3 were inferred from small angle neutron scattering measurements (SANS). The intensity of scattered neutrons in the low q region was found to increase with increasing NaNO3 concentration. This suggests an increase in the size of the micelles and/or decrease of intermicellar interaction with increasing salt concentration. Analysis of the SANS data using prolate ellipsoidal structure and Yukawa form of interaction potential between micelles indicate that addition of NaNO3 leads to a decrease in the surface charge of the ellipsoidal micelles which induces micellar growth. Cryo-TEM measurements support the presence of thread-like micelles in CTAB and NaNO3.

Small angle neutron scattering (SANS) experiments have been carried out on the micellar solutions containing mixtures of a hydrophobic triblock copolymer (L121, EO5PO68EO5) and a hydrophobic anionic surfactant (AOT, sodium bis(2-ethylhexyl)sulphosuccinate) in water with varying ratio (R) of AOT to L121 for R = 0.15, 0.2, 0.3, 0.5 and 0.6. It is known that either L121 or AOT alone forms vesicles in water, but in the mixture with appropriate ratio of the two components a thermodynamically stable, isotropic solution of apparently small micelle-like aggregates is formed. We find that these micelles are prolate ellipsoidal.

The solubilization of triglycerides [1,2,3-tributanoylglycerol (TBG) and 1,2,3-trihexanoylglycerol (THG)] in water/octa(oxyethylene) dodecyl ether (C(12)EO(8)) systems has been investigated. Oil-induced changes in the structure of liquid crystals in water/C(12)EO(8) system have been studied by optical observation and small-angle X-ray scattering (SAXS) measurements. In the water/C(12)EO(8)/oil systems, solubilization of THG and TBG induces a transition between H(1) (hexagonal) and L(alpha) (lamellar) liquid crystals at high C(12)EO(8) concentrations, whereas at low surfactant concentrations a H(1)-I(1) (discontinuous micellar cubic phase) transition occurs. This anomalous behavior is attributed to the partitioning of solubilized oil in the micelles. At low surfactant concentrations THG is mainly solubilized into the hydrophobic cores of the surfactant micelles, indicating high swelling or low penetration tendency, resulting in a steep increase in the radius of the aggregates (r(H)), thereby inducing a rod-sphere transition. At high surfactant concentrations, THG is not mainly solubilized into the core but distributed between the palisade layer and the core of the aggregates. The TBG is considerably solubilized into the surfactant palisade layer, indicating a high penetration tendency, resulting in an increase in the effective cross-sectional area per surfactant molecule, a(s). The thermal stability of the I(1) phase increases with the solubilization of THG into the aggregate cores. The percentage deviation of the experimental interlayer spacings (P(d)) from complete swelling was also evaluated for different triglycerides in the H(1) and L(alpha) phases or different surfactant concentrations. It is found that the penetration tendency of triglycerides could be used as a tuning parameter for I(1) phase formation depending on the surfactant concentration and the molecular weight of the oil.

Phase diagrams of water–alkyltrimethylammonium bromide (C n TAB, n = 10, 12, 14 and 16) systems were measured as a function of the temperature and the total surfactant concentration. All C n TABs form an isotropic solution (L 1 ), a hexagonal liquid crystalline phase (H 1 ), a cubic phase (V 1 ) and a lamellar phase (L α ) with increasing surfactant concentration. The size of the alkyl chain length of the surfactant influences the extension of the liquid crystalline phases; the shorter the alkyl chain the smaller the extension of the liquid crystalline region. In the case of the pseudobinary system H 2 O–C 10 TAB/C 16 TAB a shrinking of the H 1 phase was observed. The structure of the H 1 phases was investigated by means of small angle X-ray scattering (SAXS) and polarizing microscopy.

The formation and rheological behavior of a viscoelastic wormlike micellar solution in an aqueous solution of a mixed surfactant system of alkyl ethoxylate sulfate (AES), C(12)H(25)(OCH(2)CH(2))(3)OSO(-)(3)Na(+), and polyoxyethylene dodecyl ether, C(12)EO(3), and the unusual effect of temperature on the rheological behavior have been studied. Upon successive addition of C(12)EO(3) to the dilute micellar solution of AES, viscosity increases swiftly and reaches its peak where a viscoelastic solution with nearly Maxwellian behavior is formed. With the further addition of C(12)EO(3), viscosity decreases sharply, which is attributed to the formation of micellar joints. With increasing temperature, the extent of micellar growth increases and the viscosity maximum is achieved at a lower mixing fraction of C(12)EO(3), but the maximum viscosity attained by the system decreases. The evolution of relaxation time and network density of the viscoelastic network also suggests that with increasing temperature, enhanced micellar growth takes place, but an additional, faster relaxation mechanism becomes increasingly favorable at high concentrations of C(12)EO(3). These results can be explained in terms of the increase in free energy of hemispherical end-caps (end-cap energy) of the micelles with increasing temperature.

8 pages, 11 figures.-- PMID: 17910486 [PubMed].-- Supporting information (Suppl. figures S1-S3, 3 pages) available at: http://pubs.acs.org/doi/suppl/10.1021/la701722f/suppl_file/la701722f-file001.pdf, Printed version published Oct 23, 2007, The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 10^4 Pa, as determined by oscillatory measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase.Atemperature induced order-disorder transition can be detected by calorimetry and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials., This work was partly supported by Core Research for Evolution Science and Technology (CREST) of JST Corporation. C.R. thanks Josep Carilla (Institut d’Investigacions Químiques i Ambientals de Barcelona) for his help with DSC measurements. L.K.S. is thankful to the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan for the Monbukagakusho Scholarship. D.V. thanks JSPS for financial support. The authors are grateful to Dr. Takaaki Sato (Waseda University) for valuable discussions and comments on SAXS results.

10 pages, 13 figures.-- PMID: 17696527 [PubMed].-- Printed version published on Sep 6, 2007., We have studied the structure and rheological behavior of viscoelastic wormlike micellar solutions in the mixed nonionic surfactants poly(oxyethylene) cholesteryl ether (ChEO15)-trioxyethylene monododecyl ether (C12EO3) and anionic sodium dodecyl sulfate (SDS)-C12EO3 using a series of glycerol/water and formamide/ water mixed solvents. The obtained results are compared with those reported in pure water for the corresponding mixed surfactant systems. The zero-shear viscosity first sharply increases with C12EO3 addition and then decreases; i.e., there is a viscosity maximum. The intensity (viscosity) and position (C12EO3 fraction) of this maximum shift to lower values upon an increase in the ratio of glycerol in the glycerol/water mixed solvent, while the position of the maximum changes in an opposite way with increasing formamide. In the case of the SDS/C12EO3 system, zero-shear viscosity shows a decrease with an increase of temperature, but for the ChEO15/C12EO3 system, again, the zero-shear viscosity shows a maximum if plotted as a function of temperature, its position depending on the C12EO3 mixing fraction. In the studied nonionic systems, worm micelles seem to exist at low temperatures (down to 0°C) and high glycerol concentrations (up to 50 wt %), which is interesting from the viewpoint of applications such as drag reduction fluids. Rheology results are supported by small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) measurements on nonionic systems, which indicate micellar elongation upon addition of glycerol or increasing temperature and shortening upon addition of formamide. The results can be interpreted in terms of changes in the surface curvature of aggregates and lyophobicity., D.V. thanks Japan Society for Promotion of Science (JSPS) for financial support. This work was supported by The Ministry of Education, Culture, Sports, Science and Technology, Grant-in-Aid for Young Scientists (B), No. 18780094, and partly supported by Core Research for Evolution Science and Technology (CREST) of JST Corporation. Fruitful suggestion on SAXS measurements from Dr. Takaaki Sato (Waseda University) is gratefully acknowledged.

Formation and rheological behaviour of viscoelastic wormlike micellar solution in aqueous mixed system of nonionic surfactants, polyoxyethylene sorbitan monooleate (Tween-80) and trioxyethylene alkyl ether (C m EO 3 , m = 12 , 14, and 16) was studied. The semi-dilute aqueous solution of Tween-80, in presence of C m EO 3 shows a sharp increase in viscosity leading to the formation of a gel-like highly viscoelastic solution reaching a maximum, but decreases beyond an intermediate concentration and finally phase separates. When C 12 EO 3 is replaced by C 14 EO 3 the micellar growth occurs more effectively. However, with further increase in alkyl chain length, i.e. with C 16 EO 3 , phase separation occurs before a viscoelastic solution is formed. The effect of temperature on the water/Tween-80/C 14 EO 3 mixed surfactant system was also studied. With increase in temperature, viscosity increases more promptly and the viscosity maximum is attained at relatively lower concentration of C 14 EO 3 . Enhanced one dimensional micellar growth with increase in the temperature is mainly attributed to the decrease in the spontaneous curvature of the aggregates. Structural investigation by means of small-angle X-ray scattering (SAXS) technique of micelles in aqueous solution of Tween-80 and mixed water/Tween-80/C m EO 3 systems confirmed the one dimensional micellar growth in the above system.

The structure and rheological properties of a poly(dimethylsiloxane)-graft-poly(oxyethylene) copolymer at high concentrations in block-selective solvents were studied by small-angle X-ray scattering (SAXS) and rheometry. Analysis of SAXS data indicates that quasispherical, reverse micellar aggregates (with no ordered packing) are present in concentrated solutions of the copolymer in nonpolar solvents, and that upon addition of water, the size of such aggregates increases due to the solubilization inside the micellar cores. The viscosity of concentrated polymer solutions increases exponentially as water is added, and finally, viscoelastic, gel-like behavior is found in the vicinity of the phase separation limit. It was found that small silver nanoparticles with an average diameter of ≈3 nm can be synthesized inside the copolymer aggregates without the need of a reducing agent; namely, particles embedded in a viscoelastic matrix are obtained. The synthesis seems to follow first-order kinetics.

This study provides new experimental evidence for the disconnection of the lamellar phase ( L α ) in pseudobinary water–non-ionic surfactant systems. To prove that the disconnection is indeed a general phenomenon the phase behavior of the pseudobinary system water–pentaethylene glycol dodecyl ether/hexaethylene glycol dodecyl ether (H 2 O–C 12 E 5 /C 12 E 6 ) was investigated as a function of the surfactant composition δ and the total surfactant concentration γ . At a fixed γ of 0.10 the extension of the highly diluted L α phase shrank continuously with increasing amount of C 12 E 6 , i.e., increasing δ , until it disappeared at δ = 0.60 . The γ – T phase diagram of this particular surfactant mixture was found to have a disconnected L α phase. For the first time, SAXS measurements were carried out to monitor structural changes related to the disconnection. For this purpose the interlayer spacing d and the effective cross-sectional area a s were determined from the SAXS data along characteristic paths through the L α phase.

The micellization process of binary mixtures formed by polyoxyethylene monododecyl ether (C12En; n=12 and 15) and different ionic surfactants, anionic sodium dodecyl sulfate (SDS) and cationic hexadecylpyridinium bromide (CPB), was examined by using surface tension and viscosity measurements. Rubingh's nonideal solution theory predicted nonideal mixing and attractive interaction between the constituent surfactants in the mixed micelle. In the single systems, the relative viscosity of nonionic surfactant is greater than that of the ionic surfactant and increases with the increasing level of ethylene oxide. In the mixed surfactant systems, the relative viscosities vary at a mixed molar fraction between 0.2 and 0.3, and then the relative viscosities of mixed systems decrease with the increasing mole fraction of ionic surfactants. The experimental viscosity values show a positive deviation from ideal behavior because of mixed micelle formation and the electroviscous effect. This effect could be suppressed by ...

The characteristic feature of nonionic poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymers is that at higher temperatures they undergo clouding and liquid‐liquid phase separation. The clouding temperature of such block copolymers can be profoundly altered in the presence of various additives. In this work the effect of various additives on the clouding phenomenon of triblock copolymer P85[(EO)26(PO)39(EO)26] is discussed.

The formation and structural features of micelles from low molecular weight diblock copolymers of poly(methylmethacrylate-b-ethylene oxide) PMMA–PEO (varying in total molecular weight) and poly(butylmethacrylate-b-ethylene oxide) PBMA–PEO in water, aqueous NaCl and urea solutions were examined by surface tension, dye spectral, cloud point, viscosity and small angle neutron scattering (SANS) measurements. The increasing concentrations of NaCl reduce the onset concentration of micellization and phase separation, while urea has reverse effect. The analysis of the SANS curves revealed the presence of prolate ellipsoidal micelles in diblock copolymers at various experimental concentrations and temperatures studied. The effect of temperature, NaCl and urea on the neutron scattering profiles are more or less the same which is well supported by viscosity and surface tension measurements. The diblock copolymers form spherical micelles of aggregation number in the range of 522–664. The micelles are very temperature stable.

The interaction of aqueous binary mixtures of an N‐acyl amino acid based anionic surfactant, sodium N‐tetradecanoylsarcosinate (C14‐sarcosinate), in the presence of cationic, anionic, and nonionic surfactants has been investigated by surface tension and viscosity measurements. The cationic surfactants dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), hexadecyltrimethylammonium bromide (CTAB), dodecylpyridinium bromide (DPyB), and hexadecylpyridinium bromide (CPyB), the anionic surfactant sodium dodecyl sulphate (SDS), and the nonionic surfactant Triton X‐100 were used. The critical micelle concentration (CMC) values of pure surfactants and their mixtures were determined by surface tension measurements at different mixed ratios. The interaction parameters that measure the interaction between the surfactant molecules in the mixed micelle were computed by Rubingh's approach. The viscosity of the mixed systems of C14‐sarcosinate with cationic surfactants (having higher chain...

Studies on adsorption characteristics and micellization of mixtures containing cationic/nonionic surfactant dodecyldimethylamine oxide (DMDAO) and anionic surfactant sodium dodecyl sulfate (SDS) with and without NaCl as studied by surface tension, viscosity, dynamic light scattering (DLS) and small angle neutron scattering (SANS) showed strong synergisms and micellar growth. A large negative interaction parameter, β, using Rubing's theory for above mixed system was estimated. Sphere-to-rod transition driven by ion–dipole interactions between the dissimilar head groups in mixtures of the two surfactants (total concentration 25–100 mM) was well reflected in DLS and SANS measurements. These results are consistent with the concept that nonidealities of mixing in micelles of oppositely charged mixed surfactant systems are primarily of electrostatic origin with specific interactions.

The aggregation behavior of pure cationic surfactants (quaternary salts) in water has been studied by electrical conductivity (at 293.15–333.15 K), surface tension, dye solubilization and viscosity measurements (at 303.15 K). Critical micelle concentrations (CMCs), degree of counter ion dissociation (β), aggregation number and sphere-to-rod transition for cationic surfactants are reported. Using law of mass action model, the thermodynamic parameters, viz. Gibbs energy (�G ◦), enthalpy (�H ◦) and entropy (�S ◦ m) were evaluated. The plots of differential conductivity, (d k/dc)T,P , versus the total surfactant concentration enables us to determine the CMC values more precisely than the conventional method. Surfactants with longer hydrocarbon chain are adapted to rodlike micelle better than to a spherical micelle. The data are explained in terms of molecular characteristics of surfactants viz. nonpolar chain length, polar head group size and counter ion. © 2004 Published by Elsevier B.V.

The effects of NaCl (0–1.0 M) and alkyl chain length on the micellar size and structures of alkyltrimethylammonium bromide (C n TABr, where n = 12, 14, 16 and 18) in aqueous mixtures with and without trihydroxy bile salt, sodium cholate (NaC) have been investigated by surface tension, viscosity, time-resolved fluorescence quenching and dynamic light scattering measurements. The interaction parameter, β , obtained using Rubingh's theory showed strong interaction between C n TABr and NaC. In the presence of NaCl, the viscosity of C 12 TABr and C 14 TABr remains unaltered with increasing concentration of NaC, while for C 16 TABr and C 18 TABr, a micellar growth occurs at lower NaC concentration (5 mM) resulting a peak in the viscosity. Further addition of NaC gives smaller micelles. The position of the peak in viscosity measurements is independent of temperature (30–50 °C) and NaCl concentration, but is more pronounced in high NaCl concentration and at low temperature. These changes in viscosities are due to changes in the microstructure of the mixed aggregates. The results are well supported by dynamic light scattering and time-resolved fluorescence quenching measurements.

Effect of hydrotropes viz. sodium benzene sulfonate (NaBS), sodium toluene sulfonate (NaTS) and sodium xylene sulfonate (NaXS) on the micellization, phase behavior and structure of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer L62 in aqueous solution was studied by surface tension, dye spectral, cloud point and small angle neutron scattering measurements. The addition of hydrotropes increased the critical micelle concentration (CMC) of L62 which appears to be logistic as the added hydrotrope enhances the solubility of PPO moiety (and PEO) making it behave like a more hydrophilic block copolymer that would micellize at high copolymer concentration. Partial phase diagram of L62 in water shows two cloud point (CP) in the concentration range (0–10 wt.%). Addition of hydrotropes shifts the L62 concentration range showing double cloud points at lower side of concentration; sodium xylene sulfonate (NaXS) being more effective. SANS data for L62 in the presence of 0.4 and 0.8 M NaXS at temperatures

Cloud points, surface tension, viscosity and dynamic light scattering data on solutions of a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO); Pluronic P105, in water and NaBr solutions and for the similar systems in the presence of two ionic surfactants, sodium dodecyl sulphate (NaDS) and dodecyltrimethylammonium bromide (DTABr) are reported. The addition of NaBr to copolymer decreases cloud point, increases surface activity, shifts micellization to lower concentration. The DLS results reveal that presence of ionic surfactant (below CMC) leads demicellization of copolymer P105. Furthermore, in the presence of NaBr more surfactant is needed for demicellization of P105 micelles. The surface tension study of P105-ionic surfactant indicates stronger interaction in case of NaDS as compared to DTABr. Also, the interaction seems to diminish in the presence of NaBr. © 2004 Elsevier B.V. All rights reserved.

Micellar behavior of sodium dodecyl sulfate (NaDS) was examined in the presence of tetrabutylammonium bromide (TBABr) by surface tension, viscosity, dynamic light scattering (DLS), dye solubilization, and cloud point measurements. NaDS showed enhanced solubilization properties and a remarkable decrease in surface tension and critical micelle concentration (CMC) in presence of TBABr. Both viscosity and DLS showed growth in NaDS micelles (50 mM) above 100 mM TBABr concentration; sphere-to-rod transition and micellar growth observed till 200 mM, above which solution undergoes phase separation. The results are explained on the basis of the binding ability of bulky tetrabutylammonium ion on NaDS.

Aqueous solutions of surfactants—cationic: tetradecyltrimethylammonium bromide (C14TABr); anionic: sodium dodecyl sulfate (SDS); and nonionic: polyoxyethylene t-octylphenol (trade name Triton X-102, also called OPE-8)— in the presence of three hydrotropes, viz., sodium xylene sulfonate, sodium p-toluene sulfonate, and sodium chlorobenzene sulfonate, were examined by measuring surface tension, viscosity, and cloud points for the nonionic surfactant. The results show a marked decrease in the critical micelle concentration with increase in hydrotrope concentration for C14TABr, a marginal decrease for SDS, and very little change for OPE-8 up to 0.1 M hydrotrope. The viscosity of cationic surfactant solutions showed a remarkable increase in the presence of trace amounts of hydrotropes (up to 15 mM). In contrast, the SDS solution showed only a slight increase in viscosity at high hydrotrope concentration (150 mM), and the viscosity of the OPE-8 solution remained constant. The cloud point of OPE-8 increased in the presence of hydrotropes, unlike its behavior with the simple salt NaCl. The strong dependence of the solution behavior of cationic surfactants on the presence of hydrotropes is discussed in terms of electrostatic interaction.

Micellization of polyoxyethylene tert‐octylphenyl ether, Triton X‐100 [TX‐100], and sodium dodecyl sulfate [SDS] and their mixtures at varying mole fraction was investigated by surface tension measurements at 30°C. Changes in the critical micelle concentration (CMC) with the composition of the two surfactants so determined were analyzed by applying the Rubingh's regular solution theory to obtain interaction parameter, β ( = −3.81) showing synergism. Sodium dodecyl sulfate shows a remarkable interaction with polyethylene oxide [PEO, mol. wt. = 6000] and polyethylene oxide–polypropylene oxide–polyethylene oxide block copolymer [P65: EO19PO30EO19, total mol. wt. = 3400, % EO = 50], while no such interaction was observed for TX‐100. Interaction weakens in mixed micelle and diminishes when the mole fraction of TX‐100 in mixed system increases. Turbidimetric studies show that the presence of TX‐100 in SDS improves calcium ion tolerance.