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Karbaschi M.,Max Planck Institute of Colloids and Interfaces | Karbaschi M.,Sharif University of Technology | Bastani D.,Sharif University of Technology | Javadi A.,Max Planck Institute of Colloids and Interfaces | And 6 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

Profile analysis tensiometry (PAT) is presently the most frequently used technique for measuring surface tensions of liquids. The basis of this methodology is however an equilibrium force balance as given by the Gauss-Laplace equation. Therefore, its application under dynamic conditions, i.e. for growing drops or bubbles, is questionable. We discuss the limits of the applicability of PAT under dynamic conditions by using a growing drop configuration equipped with a high speed video camera. The systems studied are the water/air and water/hexane interface. The obtained "dynamic" drop profiles are analyzed by fitting the classical Gauss-Laplace equation. The results are additionally compared with experimental data obtained from capillary pressure tensiometry. The analysis allows defining three different regions related to respective drop expansion rates. © 2012 Elsevier B.V.

Mys V.D.,Donetsk Medical University | Fainerman V.B.,Donetsk Medical University | Makievski A.V.,SINTERFACE Technologies | Krafft M.P.,Charles Sadron Institute | Miller R.,MPI of Colloids and Interfaces
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2015

The dynamic surface tension of aqueous solutions of C10EO8 at the interfaces with air and saturated hexane vapor was measured by the maximum bubble pressure tensiometer BPA for adsorption times t≥0.01s. It can be shown that the dynamic surface pressure of C10EO8 solutions in a saturated hexane atmosphere increases at short adsorption times with increasing surfactant concentration. The theory of diffusion controlled adsorption of two surfactants from the water and gas phases, respectively, was used for data analysis. The obtained experimental results agree with a model based on a reorientation of the C10EO8 molecules, assuming a strong intermolecular interaction between hexane and C10EO8 molecules in the surface layer. Alternatively, an additional enhancement of C10EO8 adsorption activity can be assumed due to the presence of hexane molecules at the interface. © 2015 Elsevier B.V.

Gabrieli R.,SELEX Galileo | Loglio G.,University of Florence | Pandolfini P.,University of Florence | Fabbri A.,SELEX Galileo | And 8 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

A new methodology, based on fundamental optical principles relevant to the evanescent wave properties, is developed to evaluate the thinning behavior and the local thickness in different positions for curved aqueous emulsion films, generated in a hydrocarbon matrix. This methodology is applied to test data obtained by a specially-designed bread-board cell. The generated films, constituted by an aqueous sodium dodecylsulfate solution at concentration c= 2.5 times the critical micellar concentration, remain stable during several hours. The results show a slow evolution of the film thickness as a function of time starting from micrometric dimension, at the initial film formation, to a few nanometres prior to film breakage. The action of the gravitational drainage is furthermore assessed by the local thickness values in different positions of the film profile. The illustrated examples demonstrate that the evanescent wave effect can be advantageously adopted as a complementary measurement technique, additional to the usual interferometric technique. © 2012 Elsevier B.V.

Kovalchuk V.I.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Ravera F.,CNR Institute of Neuroscience | Liggieri L.,CNR Institute of Neuroscience | Loglio G.,University of Florence | And 6 more authors.
Advances in Colloid and Interface Science | Year: 2010

For the understanding of short-time adsorption phenomena and high-frequency relaxations at liquid interfaces particular experimental techniques are needed. The most suitable method for respective studies is the capillary pressure tensiometry. However, under gravity conditions there are rather strong limitations, in particular due to convections and interfacial deformations. This manuscript provides an overview of the state of the art of experimental tools developed for short-time and high-frequency investigations of liquid drops and bubbles under microgravity. Besides the brief description of instruments, the underlying theoretical basis will be presented and limits of the applied methods under ground and microgravity conditions will be discussed. The results on the role of surfactants under highly dynamic conditions will be demonstrated by some selected examples studied in two space shuttle missions on Discovery in 1998 and Columbia in 2003. © 2010 Elsevier B.V. All rights reserved.

Javadi A.,Max Planck Institute of Colloids and Interfaces | Mucic N.,Max Planck Institute of Colloids and Interfaces | Karbaschi M.,Max Planck Institute of Colloids and Interfaces | Karbaschi M.,Sharif University of Technology | And 10 more authors.
European Physical Journal: Special Topics | Year: 2013

Liquid interfaces are met everywhere in our daily life. The corresponding interfacial properties and their modification play an important role in many modern technologies. Most prominent examples are all processes involved in the formation of foams and emulsions, as they are based on a fast creation of new surfaces, often of an immense extension. During the formation of an emulsion, for example, all freshly created and already existing interfaces are permanently subject to all types of deformation. This clearly entails the need of a quantitative knowledge on relevant dynamic interfacial properties and their changes under conditions pertinent to the technological processes. We report on the state of the art of interfacial layer characterization, including the determination of thermodynamic quantities as base line for a further quantitative analysis of the more important dynamic interfacial characteristics. Main focus of the presented work is on the experimental possibilities available at present to gain dynamic interfacial parameters, such as interfacial tensions, adsorbed amounts, interfacial composition, visco-elastic parameters, at shortest available surface ages and fastest possible interfacial perturbations. The experimental opportunities are presented along with examples for selected systems and theoretical models for a best data analysis. We also report on simulation results and concepts of necessary refinements and developments in this important field of interfacial dynamics. © 2013 EDP Sciences and Springer.

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