Ricerc@Sapienza

Microgels are colloidal suspensions of particles consisting of a polymer network with the ability to deform, compress and interpenetrate, which leads them to interact in a complex collective fashion generating a rich and interesting phenomenology.
The responsiveness of their structural and dynamical properties to external stimuli (such as temperature, pH, external fields) represents their main feature. Particularly, in pNIPAM-based thermo-responsive microgels several single-particle and collective quantities, such as size, mobility, effective charge, viscosity, exhibit a transition as varying the temperature, happening at a definite temperature, slightly different for each one of these quantities.
This phenomenology is a sign that during the transition a complex structural rearrangement takes place, that could be described as a two-step collapse, as proposed in several experimental works.
Within this project I will carry on the work I am doing to understand the role of charged molecular groups onto the polymer backbone in this two-step volume phase transition. Particularly, I will carry out numerical simulations of a coarse grained model of the inner polymer structure, building on an approach recently developed in collaboration with the soft matter group wherein I work. Through these simulations, taking into account three fundamental features (the presence of a disordered polymer network, explicit charges and explicit solvent), I aim to explain the microscopic mechanisms underlying the overall structural collapse of microgels. I will compare these theoretical results with experimental data provided us by our collaborators at L2C of University of Montpellier, which investigate the volume phase transition trough dynamic and static light scattering (DLS, SLS) and electrophoresis.
The understanding of the role of charges into the volume phase transition of microgels is of fundamental importance also for the development of new composite materials.