Francis W. Starr, Thomas B. Schroeder, Sharon C. Glotzer
Center for Theoretical and Computational Materials Science and
Polymers Division, Materials Science and Engineering Laboratory
Fillers are commonly used in industrial applications to alter the properties of polymer materials. However, little is known about the microscopic details of polymer-filler interactions, limiting the development and application of new filled polymers. In particular, fillers can shift the glass transition temperature $T_g$ in polymers, which influences crystallization, aging, frictional properties, and material hardness. The relevant lengths range from the nanometer scale of primary filler particles to the macroscopic scale of filler agglomerates. Because of this diversity, simulating filled polymers poses interesting computational challenges. Here we address this problem by simulating a coarse-grained, bead-spring model of a generic, unentangled filled melt in the presence of an idealized carbon-black filler particle. We also consider a pure melt to probe the effects of the filler relative to a pure system. Preliminary results indicate the the melt dynamics are significantly slowed near the surface of an attractive filler particle, which leads to a slight increase in $T_g$ relative to the pure system. Conversely, fillers with repulsive interactions speed up the melt dynamics near the filler-melt interface, and slightly decrease $T_g$. Additional simulations probe the effects of altering the monomer-filler interactions on the static properties.