The formation and salt induced melting of a highly viscoelastic mixture oftwo oppositely charged polyelectrolytes

A quick and convenient route to prepare a highly viscoelastic mixture of tw o oppositely charged polyelectrolytes is presented. The investigation was e ssentially performed at a Axed total polyelectrolyte concentration The phas e behaviour was studied at varying ratios between the two oppositely charge d polyions. The mixtures phase separated associatively at mixing ratios in the vicinity of overall charge neutrality, while by screening the attractiv e forces with NaCl the precipitate could be dissolved. At certain mixing ra tios off charge neutrality the mixtures were highly viscoelastic single-pha se solutions in the absence of screening electrolyte. When NaCl was added t o such a solution the viscoelasticity decreased strongly since the attracti ve forces between the oppositely charged polyions were screened. Therefore, by contacting an initially salt free mixture of polyions with a brine solu tion of known concentration, the diffusion of salt into the polyion matrice s could be monitored by following the rheology of the mixture as a function of the contact time. It is shown that the transport of NaCl inside the pol yion matrices was diffusion controlled.