Abstract
Ionic microgel particles are intriguing systems in which the properties of thermo-responsive polymeric colloids are enriched by the presence of charged groups. In order to rationalize their properties and predict the behaviour of microgel suspensions, it is necessary to develop a coarse-graining strategy that starts from the accurate modelling of single particles. Here, we provide a numerical advancement of a recently-introduced model for charged co-polymerized microgels by improving the treatment of ionic groups in the polymer network. We investigate the thermoresponsive properties of the particles, in particular their swelling behaviour and structure, finding that, when charged groups are considered to be hydrophilic at all temperatures, highly charged microgels do not achieve a fully collapsed state, in favorable comparison to experiments. In addition, we explicitly include the solvent in the description and put forward a mapping between the solvophobic potential in the absence of the solvent and the monomer–solvent interactions in its presence, which is found to work very accurately for any charge fraction of the microgel. Our work paves the way for comparing single-particle properties and swelling behaviour of ionic microgels to experiments and to tackle the study of these charged soft particles at a liquid–liquid interface.
Highlights
Soft matter is a very active branch of condensed matter physics which comprises, among other systems, colloidal suspensions, whose constituent particles can greatly vary in shape, softness and function
In reference [33], we modelled a single microgel particle such that all of its monomers, including charged ones, experienced a solvophobic attraction on increasing temperature
In this work we report an extensive numerical study of single microgel particles, a prototype of soft colloids that is of great interest for the colloidal community, for the formation of arrested states with tunable rheological properties [9], including glasses [47, 48] and gels [49]
Summary
Soft matter is a very active branch of condensed matter physics which comprises, among other systems, colloidal suspensions, whose constituent particles can greatly vary in shape, softness and function. A single colloidal particle is already quite a complex object whose behaviour at the collective level is strongly connected to the microscopic features of the particle itself. This situation is typical of soft colloids, i.e. deformable particles with internal degrees of freedom strongly influencing their mutual interactions, which makes them already intrinsically multi-scale.
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