It is well known that polyion-complexes are formed by mixing polyanion and polycation in water. However, their detailed formation mechanism and the conformation of the polyelectrolyte chains inside the complex have not clearly understood yet. The irreversible formation of polyion-complexes makes difficult to understand this phenomenon. In this study, we have investigated the formation of the polyion-complex by mixing aqueous solutions of sodium polyacrylate (PAA) and poly(vinyl ammonium) chloride PVAm), mainly by light scattering. We have found that the aggregation number of the complex irreversibly increases by changing successively the mixing ratio of PAA and PVAm and also by heating and cooling process of the solution.
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Fig. 1. Composition dependence of mw for polyion–complexes formed from PAA and PVAm with different degrees of polymerization. |
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Fig. 2. Change of mw by addition of PAA and PVAm to a polyion–complex solution. |
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Fig. 3. Temperature dependence of mw of a PAA–PVAm polyion–complex in water. |