Brownian Motion of Stiff Filaments in a Crowded Environment

Abstract

Movement in a Tight Squeeze The motion of flexible polymer chains in a dense melt or concentrated solution is described by reptation theory, in which a single chain is considered to snake back and forth inside a virtual confining tube formed by all its neighboring chains. A number of theories have been proposed for stiffer molecules, but it has been hard to obtain experimental data to determine the thermal motion of stiff filaments. Fakhri et al. (p. 1804 ) visualized carbon nanotubes directly as a model system for stiff polymers diffusing in a gel, and found that even a slight increase in flexibility significantly sped up diffusion of stiff filaments under confinement. The rotational diffusion constant grew linearly with the flexibility and, counterintuitively, did not depend on the degree of crowding.