In contrast to solid colloidal particles, microgels promptly respond to external stimuli such as the temperature and the pH of the solution. This peculiarity has been widely applied in bulk experiments, where the subsequent size changes can be used to tune the particle volume fraction with no change in its number density. Despite the plain experimental interest, theory stands behind, as models lack a comprehensive description in terms of the internal polymeric nature of the microgels, which is fundamental to describe correctly their elasticity and deformability, especially in high density states [1]. We are now able to provide novel theoretical insights in this respect, thanks to a cuttingedge model that reproduces in silico realistic PNIPAM microgels. Indeed, we reconstruct the polymer network via an ensemble of bi- and tetra-valent patchy particles, whose topology is subsequently fixed via a bead-spring model [2]. The computational protocol is validated, in the first place, by comparing the calculated form factors to the ones obtained via x-ray and neutron scattering experiments. Secondly, we verify that designed and experimental microgels with equal crosslinks ratio undertook the same swelling behavior. Further improvements have allowed to introduce in the model a coarse-grained explicit solvent [3]. Indeed, we demonstrate that a likely description shall include hydrodynamics interactions, for which the solvent behaves as a continuous fluid that permeates the polymer network. The newly designed protocol paves the way to the calculation of effective interactions acting among multiple microgels in bulk, and where the presence of the solvent has revealed to be crucial, such as at interfaces [4]. [1] L. A. Lyon and A. Fernandez-Nieves, Annu. Rev. Phys. Chem. 2012, 63, 25-43 [2] N. Gnan, L. Rovigatti, M. Bergman, E. Zaccarelli, Macromolecules 50 (21), 2017 [3] F. Camerin, N. Gnan, L. Rovigatti, E. Zaccarelli, In preparation [4] L. Isa et al., Phys. Chem. Chem. Phys., 2017, 19, 8671
In silico modelling of microgels at interfaces / Camerin, Fabrizio. - (2018). (Intervento presentato al convegno Seventh Annual Niels Bohr International Academy Workshop-School on ESS Science (NBIA7): Deciphering the hidden dynamics of Soft Matter tenutosi a Copenaghen; Denmark).
In silico modelling of microgels at interfaces
Fabrizio Camerin
2018
Abstract
In contrast to solid colloidal particles, microgels promptly respond to external stimuli such as the temperature and the pH of the solution. This peculiarity has been widely applied in bulk experiments, where the subsequent size changes can be used to tune the particle volume fraction with no change in its number density. Despite the plain experimental interest, theory stands behind, as models lack a comprehensive description in terms of the internal polymeric nature of the microgels, which is fundamental to describe correctly their elasticity and deformability, especially in high density states [1]. We are now able to provide novel theoretical insights in this respect, thanks to a cuttingedge model that reproduces in silico realistic PNIPAM microgels. Indeed, we reconstruct the polymer network via an ensemble of bi- and tetra-valent patchy particles, whose topology is subsequently fixed via a bead-spring model [2]. The computational protocol is validated, in the first place, by comparing the calculated form factors to the ones obtained via x-ray and neutron scattering experiments. Secondly, we verify that designed and experimental microgels with equal crosslinks ratio undertook the same swelling behavior. Further improvements have allowed to introduce in the model a coarse-grained explicit solvent [3]. Indeed, we demonstrate that a likely description shall include hydrodynamics interactions, for which the solvent behaves as a continuous fluid that permeates the polymer network. The newly designed protocol paves the way to the calculation of effective interactions acting among multiple microgels in bulk, and where the presence of the solvent has revealed to be crucial, such as at interfaces [4]. [1] L. A. Lyon and A. Fernandez-Nieves, Annu. Rev. Phys. Chem. 2012, 63, 25-43 [2] N. Gnan, L. Rovigatti, M. Bergman, E. Zaccarelli, Macromolecules 50 (21), 2017 [3] F. Camerin, N. Gnan, L. Rovigatti, E. Zaccarelli, In preparation [4] L. Isa et al., Phys. Chem. Chem. Phys., 2017, 19, 8671I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
