Star polymers with a temperature-dependent valence

Hard patchy particles are colloids decorated with attractive spots (patches) on their surface. Recently, many pivotal theoretical and numerical studies have highlighted the richness of phenomena that these systems exhibit, both from the dynamic and the thermodynamic points of view. Examples of interesting applications relevant to this projects are empty liquids (liquid-like states which do not separate at low temperatures and densities), reentrant gels
(systems which are dynamically arrested only for a limited range of temperature) and pinched gas-liquid phase diagrams (materials exhibiting a gas-liquid instability region which shrinks at lower densities as the system is cooled down).
Unfortunately, fabricating monodisperse, anisotropic nano-- or micro--sized patchy particles in bulk quantities still eludes modern experimental techniques. In this project we build on the work carried out by the co-applicant and its group and focus on a possible realisation of patchy particles: telechelic star polymers. These are supramolecular objects made of diblock copolymer chains (i.e. chains composed by a hydrophilic part and a hydrophobic part) grafted on a central anchoring point. Such particles, due to the dual nature of their arms, exhibit a hierarchical self-assembling scenario. Indeed, on the single particle level and under the right conditions, each particle self-assembles in a soft patchy particle. The shape and topology of the resulting object depend both on the star polymer properties (number of arms and fraction of hydrophobic monomers in a chain) and on the external conditions (temperature, pressure, solvent properties). On a larger scale, particles can then self-assemble into meso- and macroscopic structures. Since the properties of the final structures depend on the shape of and mutual interactions between the constituent objects, it is vital to investigate the single particle conformation diagram as a function of the number of arms, fraction of hydrophobic monomers and temperature. Indeed, the main aim of this project is to fully characterise and control the self-assembly of telechelic star polymers, their mutual interaction strength and shape and how the latter changes upon varying the external conditions in order to
• Investigate whether telechelic star polymers conform to theoretical predictions like the shrinking of the gas-liquid phase coexisting region upon decreasing the maximum number of bound neighbours and the existence of pinched phase diagrams.
• Realise in silico technologically relevant materials like reentrant gels and empty liquids and the establishment of guidelines for their realisation in vitro by experimental groups.