Fluctuation-induced forces between rings threaded around a polymer chain under tension

ROMINA LLUBAROFF; KEVIN SPEYER; CLAUDIO PASTORINO

Los Polvorines, Gral. Sarmiento, Pcia. de Buenos Aires

Workshop; Transport Phenomena and Non-Equilibrium Processes; 2018

Fluctuation-induced forces require a fluctuating medium and some kind of boundary condition, restricting the natural oscillations of that medium. The Casimir effect is known as a phenomenon offluctuation-induced forces at a quantum level, but it is also possible to observe this effect due to thermal fluctuations of classical fields. We simulated a system consisting of a long polymer chain undertension, with two threaded polymer rings around the chain, that constrain the fluctuations of the polymer. Chain and rings are immersed in a thermal bath, given by a Langevin thermostat. The systemis interesting from a basic point of view, but also as a model of polyrotaxane which is the basic constituent of novel slide-ring materials. This simple model system can also describe some elements of otherphysical systems feasible experimentally, such as proteins adhered to lipidic membranes and interfaces of immiscible liquids. The most interesting result of our simulation is the presence of an effectiveattractive force between the threaded rings, as a consequence of their restriction on the fluctuations of the chain, without any contribution of direct interactions between them. We varied various parameters,such as the temperature, the stretching, and the stiffness of the chain, to characterize the system and describe its properties.