Microgels at interfaces behave as 2D elastic particles featuring reentrant melting

The structural and dynamical properties of colloidal assemblies are determined by the way particles interact with each other. The collective behavior of microgels, which present a characteristic fried-egg shape when adsorbed at an interface [1], remains largely unexplored and limited to indirect experimental feedback. Nonetheless, the development of novel assembly and patterning strategies on surfaces and the design of novel materials with desired interfacial behavior depend on this knowledge [2].
We show, by means of explicit solvent molecular dynamics simulations, that microgels at interfaces interact via a two-dimensional Hertzian potential, resembling simple elastic disks [3]. This functional form allows us to extract an estimate of its Young’s modulus revealing that the adsorption provides these polymeric colloids with an enhanced stiffening as compared to the bulk case. We will also analyze the collective dynamical response and unveil the presence of multiple reentrant melting phenomena. In particular, we are able to specify the experimental conditions for which this phenomenon could be truly observed, enabling the research on unique high-density liquid states.

[1] Camerin et al. ACS Nano (2019)
[2] Fernandez-Rodriguez et al., Nanoscale (2018)
[3] Camerin et al. PRX (2020)