Polyelectrolyte Electrophoresis in a Dilute Solution of Neutral Polymers: Model Studies

Abstract

Dilute neutral polymer solutions provide an effective environment for the electrophoretic separation of polyelectrolytes by molecular weight. To better understand the mechanisms responsible, this study examines how the molecular weight dependent mobility μ of poly(styrenesulfonate), termed the probe chain, depends on the molecular weight and concentration of various dilute pullulans, termed the host chains. Available for this system are nearly monodisperse probes and hosts. Carefully performed capillary electrophoresis experiments measure absolute values of μ and its distribution. Below the overlap concentration, hosts reduce μ from its free solution value in proportion to concentration. The strongest dependence of μ on probe molecular weight occurs at nearly equal probe and host chain lengths. The influence of host and probe chain lengths on μ can be understood in terms of pairwise probe−host configurational interactions. Three parametersentanglement probability, average entanglement duration, and averag...