Non-Equilibrium Molecular Dynamics Simulation of Polymer-Polymer (Slippage) Interaction

DESCRIPTION:  This demonstration illustrates the application of forced (non-equilibrium) molecular dynamics (FMD) to simulate the interaction of two different polymers (polypropylene and polyaniline) as they are forced to slip past one another. LEFT PANEL: At Time = 0, the polymers are in a sterically relaxed conformation. Then a constant kinetic energy (25 Angstroms/ps) is  applied to the terminal "Tractor Atom" in the polypropylene chain (green arrow), whereas a single carbon atom in the polyaniline chain (red arrow) is tethered in place to prevent net displacement of that polymer. The zone of friction that develops as a reuslt of the polymer-polymer slippage is indicated by the wavy orange line. RIGHT PANEL: Plot of system temperature (K), potential energy (kcal/mol), and strain energy (kcal/mol-Angstrom) as a function of time (cycle number). The temperature increases over the course of the FMD simulation as energy is continuously injected into the system to maintain a constant slippage velocity. Young's Modulus, a measure of the stiffness of a material, could be calculated from a series of such simulations in which the applied stress (kinetic input) is varied as a function of the resulting strain (change in potential). 
Click HERE to view animated GIF movie loop of polymer-polymer slippage (File Size ~72MB).