The statistics and dynamics of confined or entangled stiff polymers

The statistics of a wormlike chain of persistence length P and contour length L trapped in a cylindrical pore of diameter D can be understood if a length scale X N D2/3P*/3 is introduced ( P >> D). If L 5 A, it is a good approximation to view the chain as being completely rigid. Whenever L >> A, it is convenient to regard the stiff coil as a sequence of rigid links, each of length A. The free energy involved in forcing a stiff chain into a pore is calculated by scaling arguments. When the chain is confined in a network of mesh size A, we again have X N A2I3P1J3. If L 5 A, i t is reasonable to approximate the chain as a completely stiff rod in its reptational and reorientational motion. Whenever X 5 L 5 P, a new region emerges in between the rigid rod and flexible chain limits. Then, the rotational diffusion coefficient scales as L-2 instead of L-5 as in the rigid rod case. The usual L-3 dependence (flexible coil limit) is recovered if L 2 P.