Lecture series on soft matter
Calorimetric methodologies: principles and applications
|Calorimetry is a powerful physicochemical methodology for measuring the thermal properties of a variety of substances, including soft-materials, and is the only technique for direct determination of the enthalpy change of the processes. Among calorimeters, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) are widely used in many fields of sciences. DSC, giving direct thermodynamic information, has proved to be very useful in clarifying the energetics of macromolecule transitions and in characterizing their thermal stability. On the other hand, ITC is very suitable to study the energetics of molecular interactions, giving the binding constant, the stoichiometry and all the thermodynamic parameters. Here basic principles, common instrumentations, data analyses and some applications will be discussed. Specifically, two examples of calorimetric applications to study the thermodynamics of secondary nano-emulsion formation and the energetics of ligand-receptor binding affinity on endothelial cells will be discussed.
Direct measurement of free energy derivatives: Calorimetry and Volumetry
|The lecture will be focused on the direct measurement of thermodynamic properties that are free energy derivatives. In particular the partial molar quantities will be described. Based on some case studies, we’ll explore the relevance in colloidal systems about methods to access directly thermodynamic quantities. In particular, the dilemma on enthalpy changes in supramolecular aggregates: van’t Hoff vs direct methods will be described. Volumetrv analysis of complex systems will be presented based also on its predictive ability toward pressure effect. Experimental tips and case studies will help the audience in a proper planning of measurements.
Ana Celia Vila Verde
Introduction to classical particle-based simulations of soft matter
|This lecture will introduce the listeners to Monte Carlo and Molecular dynamics simulation methods using classical energy functions, and the most commonly used algorithms to perform free energy calculations. Emphasis will be given to the concepts that a non-specialist must have to be able to critically read a report of a simulation study.
Surfactant Self-Assembly – Fundamentals and Applications
|Self-assembly is a ubiquitous phenomenon in science, being observed in solution for surfactants, copolymers, or proteins – and, of course, in combinations thereof with other colloidal systems. Accordingly, self-assembly is at the heart of many important scientific processes, such as detergency, formulations in pharmacy or cosmetics, biomembranes, biological systems, etc. Therefore, it is very important to understand the principles of self-assembly and especially how they are related to the molecular composition of the systems and how this translates into the properties of such systems. In this lecture this will be discussed for the case of surfactants, which can become organised in the form of small spherical micelles or worm-like micelles, where the latter may exhibit several orders of magnitude higher viscosity and viscoelastic properties. Another example concerns the solubilisation of hydrophobic molecules in aqueous solutions, which is important for instance for cleaning or tertiary oil recovery, but also for rendering otherwise insoluble drug molecules soluble. The lecture will deal with the basic principles of surfactant self-assembly and use this understanding to rationalise some simple applications of surfactants.
Thermodynamics of interfaces
|In this lecture, I will first introduce some concepts related to the definition of an interface, long range surface forces, disjoining pressure and adsorption. In the second part, I will discuss some aspects of the physics of wetting. Energetics of: a) liquid drops on solid substrates and b) solid particles at liquid interfaces, will be described in different length scales: from the macroscopic down to the nanoscale. Finally, I will describe the stability of a liquid foam, considered as an interfacial material rather than a gas in liquid dispersion.
Atomic Force Microscopy (AFM): working principles, modes of operation and applications
|The atomic force microscope (AFM) is an invaluable tool not only to obtain high (sub-nanometer)-resolution topographical images, but also to determine certain physical properties of specimens, such as stiffness and adhesion, surface charge and even chemical surface composition. The AFM has the advantage over other forms of microscopy in terms of spatial and temporal resolution and possibility of imaging almost any type of surface, including polymers, ceramics, composites, glass, and biological samples. In addition to the wide range of applications, from materials science to biology, this technique can be operated in a number of environments as long as the specimen is attached to a surface, including ambient air, ultra-high vacuum, and, most importantly for biology, in liquids. This lecture will first introduce the viewer to the fundamental aspect of AFM. Then, basic principles of operation of an AFM, the associated instrumentation and methodology; and the fundamental aspects how this high-resolution surface typography images and maps of surface forces can be obtained will be discussed. Main AFM operation modes; pro and cons of each mode, as well as representative results from the literature highlighting a variety of application areas will be also shown. Finally, some representative AFM artefacts and other examples of the applications of AFM imaging and force spectroscopy will be illustrated.
Physical mechanisms of the interaction between lipid-based membranes in aqueous environments
In the congested environment of cells and tissues, the interaction between the surfaces of biomolecular assemblies -- notably biomembranes -- is of paramount importance for numerous biological processes. This lecture reviews various mechanisms underlying the interaction between lipid-based membranes in their aqueous (physiological) surroundings. The lecture covers van der Waals interactions, electric double-layer forces, solvent- and solute-mediated forces, as well as undulation-induced forces and forces associated with the conformation of membrane-associated polymers. Experimental aspects as well as continuum-theoretical descriptions and atomistic computer simulations are discussed.
Liquid Foams: From Basic Principles over Practical Aspects to Future Perspectives
Part 1: What is the difference between foamability and foam stability? How do liquid fraction, foam volume, and bubble size evolve as a function of time for stable and unstable foams, respectively? How can I study foams reproducibly? Under which circumstances can I compare the properties of foams generated with different surfactants? The first part of this presentation will answer these questions!
 On how Surfactant Depletion during Foam Generation Influences Foam Properties, J. Boos, W. Drenckhan, C. Stubenrauch, Langmuir, 2012, 28, 9303-9310