1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Intermolecular And Surface Forces

Stimuli-responsive nanoparticles, nanogels and capsules for integrated multifunctional intelligent systems

Foods make up some of the most complex examples of soft condensed matter (SCM) with which we interact daily. Their complexity arises from several factors: the intricacy of components, the different aggregation states in which foods are encountered, and the multitude of relevant characteristic time and length scales. Because foodstuffs are governed by the rules of SCM physics but with all the complications related to real systems, the experimental and theoretical approaches of SCM physics have deepened our comprehension of their nature and behaviour, but many questions remain. In this review we discuss the current understanding of food science, by considering established SCM methods as well as emerging techniques and theoretical approaches. With their complexity, heterogeneity and multitude of states, foods provide SCM physics with a challenge of remarkable importance.

Understanding foods as soft materials

1. Particles at liquid interfaces - an introduction B. P. Binks and T. S. Horozov 2. Structure and formation of particle monolayers at liquid interfaces L. Bergstrom 3. Theory for interactions between particles in monolayers J. C. Fernandez-Toledano, A. Moncho-Jorda, F. Martinez-Lopez and R. Hidalgo-Alvarez 4. Particle-assisted wetting W. A. Goedel 5. Particle-laden interfaces: rheology, coalescence, adhesion and buckling G. G. Fuller, E. J. Stancik and S. Melle 6. Solids-stabilized emulsions: a review R. J. G. Lopetinksy, J. H. Masliyah and Z. Xu 7. Novel materials derived from particles assembled on liquid surfaces K. P. Velikov and O. D. Velev 8. Interfacial particles in food emulsions and foams E. Dickinson 9. Collection and attachment of particles by air bubbles in froth flotation A. V. Nguyen, R. J. Pugh and G. J. Jameson 10. Antifoam effects of solid particles, oil drops and oil-solid compounds in aqueous foams N. D. Denkov and K. G. Marinova 11. Metal foams: towards high temperature colloid chemistry N. Babcsan and J. Banhart.

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Colloidal Particles at Liquid Interfaces

The flexural properties of a particle adsorption monolayer are investigated theoretically. If the particles are not densely packed, the interfacial bending moment and the spontaneous curvature (due to the particles) are equal to zero. The situation changes if the particles are closely packed. Then the particle adsorption monolayer possesses a significant bending moment, and the interfacial energies of bending and dilatation become comparable. In this case, the bending energy can either stabilize or destabilize the Pickering emulsion, depending on whether the particle contact angle is smaller or greater than 90 degrees . Theoretical expressions are derived for the bending moment, for the curvature elastic modulus, and for the work of interfacial deformation and emulsification. The latter is dominated by the work for creation of a new oil-water interface and by the work for particle adsorption. The curvature effects give a contribution of second order, which is significant only for emulsification at 50:50 water/oil volume fractions. A thermodynamic criterion for the type of the formed emulsion is proposed. It predicts the existence of a catastrophic phase inversion in particle-stabilized emulsions, in agreement with the experimental observations. The derived theoretical expressions could find application for interpretation of experimental data on production and stability of Pickering emulsions.

On the thermodynamics of particle-stabilized emulsions: curvature effects and catastrophic phase inversion.

Static and dynamic light scattering experiments show that the mixed micelles of sodium dodecyl sulfate (SDS) and cocoamidopropyl betaine (CAPB) undergo a sphere-to-rod transition at unexpectedly low total surfactant concentrations, about 10 mM. The lowest transition concentration is observed at molar fraction 0.8 of CAPB in the surfactant mixture. The transition brings about a sharp increase in the viscosity of the respective surfactant solutions due to the growth of rodlike micelles. Parallel experiments with mixed solutions of CAPB and sodium laureth sulfate (sodium dodecyl-trioxyethylene sulfate, SDP3S) showed that the sphere-to-rod transition in SDP3S/CAPB mixtures occurs at higher surfactant concentrations, above 40 mM. The observed difference in the transition concentrations for SDS and SDP3S can be explained by the bulkier SDP3S headgroup. The latter should lead to larger mean area per molecule in the micelles containing SDP3S and, hence, to smaller spontaneous radius of curvature of the micelles (i.e., less favored transition from spherical to rodlike micelles). The static light scattering data are used to determine the mean aggregation number and the effective size of the spherical mixed SDS/CAPB micelles. From the dependence of the aggregation number on the surfactant concentration, the mean energy for transfer of a surfactant molecule from a spherical into a rodlike micelle is estimated.

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Synergistic sphere-to-rod micelle transition in mixed solutions of sodium dodecyl sulfate and cocoamidopropyl betaine.

Here, we present experimental surface-tension isotherms of mixed solutions of two surfactants, sodium dodecyl sulfate (SDS) and cocoamidopropyl betaine (Betaine), measured by means of the Wilhelmy plate method. The kinetics of surface-tension relaxation exhibits two characteristic time scales, which have been distinguished to determine correctly the equilibrium surface tension. The transition from the zwitterionic to the cationic form of Betaine is detected by surface-tension measurements. Synergistic dependence of the critical micellization concentration on the composition of the surfactant blend is established. The experimental surface-tension isotherms are fitted by means of the two-component van der Waals model, and an excellent agreement between theory and experiment was achieved. Having determined the parameters of the model, we calculated different properties of the mixed surfactant adsorption layer at various concentrations of SDS, Betaine, and salt. Such properties are the adsorptions of the two ...

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Mixed Solutions of Anionic and Zwitterionic Surfactant (Betaine): Surface-Tension Isotherms, Adsorption, and Relaxation Kinetics

Here, we investigate water-in-oil (W/O) emulsions that are stabilized by polystyrene latex particles with sulfate surface groups. The particles, which play the role of emulsifier, are initially contained in the disperse (water) phase. The existence of such emulsions formally contradicts the empirical Bancroft rule. Theoretical considerations predict that the drop diameter has to be inversely proportional to the particle concentration, but should be independent of the volume fraction of water. In addition, there should be a second emulsification regime, in which the drop diameter is determined by the input mechanical energy during the homogenization. The existence of these two regimes has been experimentally confirmed, and the obtained data agree well with the theoretical model. Stable W/O emulsions have been produced with hexadecane and tetradecane, while, in the case of more viscous and polar oils (soybean and silicone oil), the particles enter into the oily phase, and Pickering emulsions cannot be obtained. The formation of stable emulsions demands the presence of a relatively high concentration of electrolyte that lowers the electrostatic barrier to particle adsorption at the oil -water interface. Because the attachment of particles at the drop surfaces represents a kind of coagulation, it turns out that the Schulze -Hardy rule for the critical concentration of coagulation is applicable also to emulsification, which has been confirmed with suspensions containing Na + ,M g 2+ , and Al 3+ counterions. The increase of the particle and electrolyte concentrations and the decrease of the volume fraction of water are other factors that facilitate emulsification in the investigated system. To quantify the combined action of these factors, an experimental stability -instability diagram has been obtained.

Latex-particle-stabilized emulsions of anti-Bancroft type.

https://www.dce.uni-sofia.bg/files/publications/2012/2012-14-SA-KD-EB-PK-KA-Micelle-Charge-Aggregation-Number.pdf

Kavssery P. Ananthapadmanabhan

Papers

On the thermodynamics of particle-stabilized emulsions: curvature effects and catastrophic phase inversion.

Synergistic sphere-to-rod micelle transition in mixed solutions of sodium dodecyl sulfate and cocoamidopropyl betaine.

Mixed Solutions of Anionic and Zwitterionic Surfactant (Betaine): Surface-Tension Isotherms, Adsorption, and Relaxation Kinetics

Latex-particle-stabilized emulsions of anti-Bancroft type.

Determination of the aggregation number and charge of ionic surfactant micelles from the stepwise thinning of foam films