Modeling non-linear micromechanics of hydrogels using dissipative particle dynamics
Svetoslav Nikolov, Alberto Fernandez-Nieves, Alexander Alexeev
Microgels have the remarkable ability to undergo large, reversible changes in volume (10-20 times) when exposed to appropriate external stimuli (electric/magnetic fields, temperature, salinity, etc.), which has made them an attractive material of choice for tasks such as drug delivery and micropropulsion. However, the mechanics of microgels is still not completely understood. Full-scale atomistic modeling of micrometer-sized gel networks is currently not possible due to the large length and time scales involved. We develop a mesoscale model based on dissipative particle dynamics to examine the mechanics of microgels in solvent. In our work, we characterize the flexibility of individual chains which we then use to construct larger networks. By varying the osmotic pressure of the gels we probe the changes in bulk modulus for different values of the Flory-Huggins parameter. Therefore, establishing a relationship between individual chain parameters and bulk material properties. We also examine how the bulk modulus depends on inhomogeneities we introduce within the gel structure by altering the crosslink density and by embedding rigid nanoparticles.