Dynamics of semiflexible polymer solutions in the highly entangled regime

We present experimental evidence that the effective medium approximation (EMA), [D.C. Morse, Phys. Rev. E 63, 031502 (2001)PLEEE81063-651X10.1103/ PhysRevE.63.031502], provides the correct scaling law of the plateau modulus G0 ρ4/3Lp-1/3 (with ρ the contour length per unit volume and Lp the persistence length) of semiflexible polymer solutions, in the highly entangled regime. Competing theories, including a binary collision approximation (BCA), instead predict G0 ρ7/5Lp-1/5. We have tested both predictions using F-actin solutions which permit experimental control of Lp independently of other parameters. A combination of video particle tracking microrheology and dynamic light scattering yields independent measurements of G0 and Lp, respectively. Thus we can distinguish between the two proposed laws, in contrast to previous experimental studies focused on the (less discriminating) concentration dependence. © 2008 The American Physical Society.