Anagrafe della ricerca

This project aims at investigating structured fluids with a multiscale approach combining experiments, theory and simulations. A particular test case, representative of other structured fluids, is selected and studied: binary mixtures of water and Pluronic. Pluronics are tri-block amphiphilic copolymers, aka as poloxamers, with important applications in the pharmaceutical and cosmetic industries. In the context of this project, Pluronics will serve as a model system, due to the wide range of molecular weights and amphiphilic features covered. In fact, depending on the type of molecule, temperature, concentration and external applied flow, they can indeed behave as unimers, create supramolecular aggregates or give rise to phase transitions. Three time- and length-scales are here studied: (1) molecules, (2) microstructures & (3) chemical-reactors/industrial-mixing-devices. Pluronic molecules self-assemble (or aggregate) in water above critical concentrations and temperatures, forming molecular arrangements or microstructures, which in turn result in non-Newtonian behaviour. This latter is eventually crucial in determining the performance of mixing operations involved in the preparation or processing of structured fluids. (1) Molecules are investigated by using full-atom molecular dynamics (MD). The aim is to characterize the behaviour of single Pluronic molecules in water and to quantify the corresponding transport properties, by performing simulations at different concentrations and temperatures. (2) Microstructures (e.g., spherical micelles, rod-like micelles, hexagonal phases, lamellar phases, etc.) are investigated by using both experimental rheology in the linear and non-linear regimes and computational models to explain and/or support experiments. The objective is to understand the microstructure-property relationship, to study the effect of deformation and to investigate quiescent and dynamic phase equilibria, explored also with the use of a coarse-grained MD model, based on dissipative particle dynamics (DPD). (3) The analysis of reactors focuses on particle image velocimetry (PIV), planar laser induced fluorescence (PLIF) and power consumption measurements on stirred tanks. These experimental investigations complement the rheological characterization previously described and provide experimental data for the validation of computational fluid dynamics (CFD) models. The description of the non-Newtonian behaviour of the investigated structured fluid in CFD models will be initially based on analytical constitutive equations, which will then be replaced by a rheological description actively learned from DPD simulations via artificial intelligence (AI). AI allows a very efficient coupling of DPD and CFD simulations. Being based on opensource codes, they will result into a seamless uptake in academic and industrial environments.