Intrinsic viscosity of wormlike regular four-arm stars

The ratio g(eta) between the values of the intrinsic viscosity [eta] of the Kratky-Porod wormlike regular four-arm star and linear touched-bead models, both having the same total contour length L and bead diameter d(b) (both in units of the stiffness parameter lambda(-1)), was numerically evaluated using the Kirkwood-Riseman approximation. By examination of the behavior of g(eta) as a function of L and d(b), it was found that the ratio g(eta)/g(eta)(0) of g(eta) to its asymptotic value g(eta)(0) in the rod limit monotonically increases from 1 to 3.27 with increasing L and is almost independent of d(b) for d(b)less than or similar to 0.2, although the behavior of g(eta) itself as a function of L has remarkable dependence on d(b). Furthermore, the behavior of the ratio g(eta,4)/g(eta,3) between the values of g(eta) of four-(g(eta,4)) and three-arm (g(eta,3)) stars, both having the same L and d(b), was examined as a function of L and d(b). It was then found that g(eta,4)/g(eta,3) first decreases from the asymptotic value 0.91 in the random-coil limit and then increases after passing through a minimum, with decreasing L in the range of d(b) examined, and g(eta,4)/g(eta,3) appreciably depends on d(b), as in the cases of g(eta,4) and g(eta,3) themselves. Polymer Journal (2012) 44, 115-120; doi:10.1038/pj. 2011.45; published online 1 June 2011