Using capillaries with varying cross-section to study polymer dynamics and behavior under multiple confining length scales

Infiltrating polymers into cylindrical nanopores to induce confinement has led to the fabrication of a new class of nanostructured polymeric materials. The behavior of polymers during infiltration and under confinement has been elucidated with the help of computational studies, revealing a rich thermodynamic and kinetic landscape. These systems, however, focus on confinement with a single characteristic length scale. There are many situations in which polymers infiltrate into a porous medium with varying dimensions (e.g., a packing of nanoparticles). In this talk, we address the question of what happens when polymers are confined with more than one characteristic length scale. To that end, we have simulated capillaries with varying cross-sections and multiple well-defined points of confinement, including necks and voids. Using umbrella sampling, we can explore the free energy of an infiltrating polymer melt to characterize the impact of confinement on the driving force for infiltration. We also vary the diameter of the capillary mouths to characterize the effect of geometry on the start of infiltration as polymers move from the bulk to the confined pore. Lastly, we also investigate the effect of varying cross-section on the rheological components of the polymer.