Leonardo Chiappisi

Surfactants are among the simplest building blocks in the colloidal playground. Nevertheless, they exhibit an astonishingly rich behavior. In my research activity, I probe the behavior of very different class of surfactant, explore their response to changes in their chemical or physical environment, with the aim of a better understanding of their properties and to design simpler, greener, surfactant-based systems.

Chitosan is the deacetylated form of chitin, the second most abundant biopolymer after cellulose. This unique polysaccharide attracts wide interests due to its peculiar combination of characteristics. The presence of the amino groups along its backbone, imparts to the polymer a positive charge in acidic aqueous environment. In my research activity, the complex, self-organization behavior in mixtures of chitosan and oppositely charged surfactants is studied and exploited for the design of novel functional materials.

Exploring the behavior of soft matter upon application of an external pressure is at the same a fascinating and challenging topic. The interest into performing this studies is twofold. In the first place, pressure is an extensive thermodynamic parameter, as it is temperature. By the variation of pressure, we can explore the energetic landscape of a system, and obtain a deeper understanding of the interactions within the components and the driving forces governing its behavior. Sudden pressure variations, i.e, pressure-jumps allow us to probe the mechanism trough which certain processes take place, e.g., the mixing or demixing of polymer solutions. In addition, pressure is a technically highly relevant parameter, and understanding its effect on different colloidal systems will allow us to improve the design of, e.g., synovial fluids, pressure-responsive coatings, actuators, etc.

Liquid foams are a recent focus of my research in the realm of colloidal science. These intriguing materials consist of gas bubbles dispersed within a liquid matrix, and they find applications across various industries, from cosmetics to food production. Understanding the stabilization, drainage, and coarsening processes in liquid foams is essential for optimizing their properties and performance. My work involves investigating the intricate interplay of forces and interfaces that govern foam behavior. Neutron scattering techniques provide valuable insights into the structural and dynamical properties of foams at the nanoscale.

Polymers are a fundamental class of materials in the realm of colloidal science, playing a pivotal role in my research as a physico-chemist. These versatile macromolecules, exhibit a wide range of properties that greatly influence the behavior of colloids and soft matter systems. Understanding the interactions and dynamics of polymers within these systems is essential for advancing our knowledge in material science, particularly in the context of designing and engineering novel colloidal materials with tailored properties.

Anyone who attempted to prepare mayonnaise, knows how difficult the mixing of water and oil can be. Nevertheless, the importance of mixing liquids at the microscale goes far beyond a culinary pleasure. In fact, micro-, nano-, or macro-emulsions are of exceptional technical relevance and continuous efforts are made to develop novel, cheap, environmentally friendly procedures to prepare emulsion systems. 

The most common approach foresees the use of surfactants and cosurfactants, which stabilize the interface between the two liquids. The components need to be selected for the target application of the system, and might carry stimuli-responsive properties which allow to adapt the systems properties. Oil and water can, however, be mixed also without the use of surfactant molecules. The so-called "surfactant-free emulsions" are based on the Ouzo-effect, i.e., the formation of a metastable emolsion when a three liquids, pairwise fully miscible, are mixed together. The effect is at the basis of the turbidity arising upon diluting the famous Greek spirit or the French Pastis.

In our research activity, our limits are often set by missing sample environments or the inability of treating the collecting data. Part of my research activity aims at overcoming such limitations. Progress might be brought by novel approaches of data analysis, by providing the computational tools for data treatment, or in the design of new sample enviroments.