Séminaire Susana Marín-Aguilar (Sapienza University, Rome)

Dependence on crosslinker concentration in the Structural, Dynamical and Mechanical Properties of Microgels

Susana Marín-Aguilar Department of Physics, Sapienza University of Rome, 00185 Rome, Italy.

Microgels are a versatile type of soft particle consisting of crosslinked polymer chains. Their structure and elastic properties are closely related to the amount of crosslinker monomers used in their synthesis [1]. However, extracting detailed information about crosslinker features from experimental measurements remains a cumbersome task. Moreover, in some extreme cases, probing how their structure evolves under crowding remains difficult due to experimental limitations. In the first part of this talk, I will show that we can leverage data obtained from monomer-resolved molecular simulations of microgel particles to use it as Machine Learning input data to give insights on the crosslinker structural information of a single particle [2]. Next, I will then focus on the extreme case of ultra low-crosslinked microgels (ULCs). I will demonstrate that the structural, mechanical, and dynamical behavior of ULCs differs significantly from that of microgels with higher crosslinker concentrations under crowded conditions. By combining surface-mesh and particle-resolved analyses, we capture the role of dangling chains and quantify shape changes, interparticle overlaps, and bulk moduli with unprecedented detail. Our results reveal a previously uncharacterized regime in which ULCs deform and interpenetrate through their loose outer chains. This has a significant impact on their collective dynamics and mechanical response [3]. 

[1] A. Scotti, et al. “Deswelling of microgels in crowded suspensions depends on cross-link density and architecture”. Macromolecules, 52,11, (2019).

[2] S. Marín-Aguilar and E. Zaccarelli. “Predicting structure and swelling of microgels with different crosslinker concentrations combining machine-learning with numerical simulations”. Soft Matter, 21, 8669, (2025). 

[3] S. Marín-Aguilar and E. Zaccarelli. “Unexpected Behavior of Ultra-Low-Crosslinked Microgels in Crowded Conditions”, Submitted (2025), arxiv preprint arXiv:2511.04868