Tumbling and Deformationof Isolated Polymer Chainsin Shearing Flow.

Using Brownian dynamics simulations of polymer chainsover a widerange of resolution, we find universal scaling laws for polymer coildimensions and tumbling time. At high shear rates γ̇,the coil thickness in the gradient direction becomes independent ofchain length, scaling as NK0γ̇–1/4,where NKdenotes the numbers of Kuhn steps,and the tumbling time scales as NKγ̇–3/4, correcting scaling laws presented in prior studies.We find this to be a consequence of the formation of loops whose lengthis limited by the time required to stretch them and derive scalinglaws from a balance of convection and diffusion of monomers. We findthat, in the absence of hydrodynamic interaction (HI) and excludedvolume (EV), for wormlike chains, the shrinkage in chain stretch observedat ultrahigh shear rates is pushed out to arbitrarily high shear ratesif the chain is resolved increasingly finely below the persistencelength. Finally, scaling laws in the presence of excluded volume andhydrodynamic interactions are derived that are expected to be validfor long chains at high shear rates. [ABSTRACT FROM AUTHOR]