Simulations of Thin Films and Fibers of Amorphous Polymers

Abstract

Models for nanofibers of amorphous polymers can be constructed by manipulation of the periodic boundary conditions commonly employed in the simulations of polymer melts. After a strong extension of the periodicity in one direction, equilibration causes the model to form a free-standing thin film. Repetition of this process with the boundary in a different direction converts the free-standing thin film into a thin fiber, exposed to a vacuum. For a successful construction of the model for the fiber, the system must be sufficiently robust, in terms of the degree of polymerization and number of the independent parent chains. The length of the periodic box along the fiber axis can exceed the length of a fully extended parent chain if a sufficiently large number of independent parent chains is employed in the simulation. The correlation length, ξ, in the fit of the radial density profile to a hyperbolic tangent function is a useful indicator of the integrity of the model for the thin fiber.