On the universality of sedimentation of flexible polymers in dilute and semidilute solutions

In the present investigation, the sedimentation behavior, over an extended concentration range, in solutions of polystyrenes under good, marginal, and theta solvent conditions, is analyzed in the framework of a recent theoretical model, which takes into account the gradual screening of both hydrodynamic and excluded-volume interactions in the semidilute regime. The model inspires the construction of universal plots of the form S/S₀ versus k_sc, where S is the sedimentation coefficient at polymer concentration c, S₀ is that at infinite dilution, and k_s is the concentration dependence coefficient. The resulting analytical expressions, without adjustable parameters, are consistent with experimental sedimentation data over the whole concentration range studied.