Interdiffusion of Short Chain Associative Polymers in Thin Films: MD Simulation Study

Polymer dynamic behavior at interfaces often defines the stability and control function of macromolecules in a broad range of applications. The interfacial behavior polymers that consist of highly interacting groups, such as ionizable segments, differ significantly from that of van-der Waals polymers, where tethering a few associating groups to a polymer backbone significantly affects the polymer mobility due to the formation of ionic clusters. Using molecular dynamics (MD) simulations, this study explores the interfacial dynamics at the associative/non-associative polymers interface using a bead-spring model starting with a length of 20 beads per chain with interacting beads of varying interactions 1 to 10 k_BT typical to the van der Waals interactions and hydrogen bonds. We find that the interfacial structure of the interacting polymers changes as the interaction strength of the associating groups is varied and affects the interdiffusion across the interface. With increasing interaction strength, clusters grow in bulk, acting as physical crosslinkers, diminishing chain mobility in bulk and across the interfaces. The diffusion across the structured interface and degree of interpenetration as a function of interaction strength, chain length and polymer topology will be discussed.