Free-draining polymer friction
= Free-draining polymer friction
{title2=$\zeta_N=N\zeta_0$}
With additive drag from $N$ identical <monomers>, $\zeta_N=N\zeta_0$ and centre-of-mass <diffusion> is $D_N=k_BT/(N\zeta_0)$. For <monomer> <Stokes law> $\zeta_0=6\pi\eta a$, this gives $D_N\propto N^{-1}$. The model neglects long-range hydrodynamic coupling and does not alone describe the long-time spatial <diffusion> of a strongly entangled chain.