THE EFFECT OF BLOB SIZE AND NETWORK DYNAMICS ON THE SIZE-BASED SEPARATION OF POLYSTYRENESULFONATES BY CAPILLARY-ELECTROPHORESIS IN THE PRESENCE OF ENTANGLED POLYMER-SOLUTIONS

This work focuses on the separation of standard polystyrenesulfonates (PSS), with molecular masses (M-r) between 16 and 990 x 10(3) in capil laries filled with semidilute (entangled) linear hydrophilic polymers. Contrary to cross-linked chemical gels, which produce permanent netwo rks, solutions of linear polymers lead to dynamic networks. The analyt ical performances and migration mechanisms are discussed on the basis of experiments performed in solutions of linear polyethyleneoxides and derivatized celluloses of various molecular masses. The influence of the mesh size and of the lifetime of the obstacles of the separating n etwork has been investigated in detail. The mesh size is assimilated t o the blob size of the separating polymer and is a decreasing function of its concentration. The lifetime of the obstacles of the network, i dentified with the reptation time of the polymer chain, characterizes its dynamics. This characteristic time increases with both the molecul ar weight of the separating polymer and its concentration. Its impact was first examined at fixed blob size. Then, the influence of the blob size was studied while keeping the reptation time of the network cons tant. By doing so, the existence of interactions between the solute an d the separating polymer or between the solute and capillary wall can be more safely assessed. It appears that the reptation time of the mes h has a large influence on the electrophoretic mobility of the PSSs un der a threshold value, which is of the order of magnitude of the time taken by the PSS to migrate on the blob size. Also shown are separatio ns using networks made up with mixtures of polyethyleneoxides of the s ame nature and same mass concentration, but of very different molecula r masses. This latter approach allows one to adapt the viscosity of th e solution and the dynamics of the network, keeping the blob size cons tant.