Oral: Investigating Effects of Dispersity on Welded Polymer Interface: A Coarse-Grained Molecular Dynamics Simulation Study

Polymer interfaces are important in applications such as adhesives, coatings and in their integration into other devices. A common way of strengthening the interface is through thermal welding, where the system is heated above the glass transition temperature, allowing the polymer chains to interdiffuse for a period of time. Understanding molecular mechanisms that dictate interfacial strength has both fundamental and technological implications. Polymer melt dynamics predicts that properties of welded interface should be indistinguishable from those of the bulk once the chains have diffused by about their radius of gyration. Prior simulation studies have mainly focused on monodisperse melts; however, synthetic polymers usually exhibit some form of molecular weight distribution characterized by dispersity Ð, which influence bulk and interfacial properties. In this work, we perform molecular dynamics simulations to study thermal welding of polymers that follow Schulz – Zimm molecular weight distribution. We explore melts in the low Ð regime to moderate Ð and also vary chain stiffness. First, we compute average interdiffusion depth of monomers across the interface at different weld times and also quantify the interfacial entanglement. Next, we estimate interfacial strength at the end of the weld time through a simple shear test. Overall, this work provides a necessary foundation to guide the design of polymers with improved interfacial strength using dispersity as a tuning parameter.