The effect sodium chloride on the composition and structure of network polymer−surfactant complexes (NPSC) formed by slightly cross-linked networks of poly(diallyldimethylammonium chloride) (PDADMACL) and oppositely charged surfactants of sodium dodecylbenzenesulfonate (SDBS) was studied. The comparison of the composition of NPSC with the data obtained by SAXS shows that, at some content of the surfactant ions in the gel phase, highly ordered lamellar structure in NPSC is formed. In the solution of high ionic strength and at significant excess of the surfactant molecules in the external solution, this highly ordered NPSC can be strongly nonstoichiometric. The excess of the surfactant anions in the polyelectrolyte network first increases with the increase of the ionic strength of the solution, reaching a maximum at c = 0.3 M NaCl, and only after that starts to decrease. The degree of spatial order in NPSC becomes more pronounced when the nonstoichiometric complexes in the solution of high ionic strength are formed. These results are explained by introducing the model in which the fitting of packing of the surfactant and polymer components in NPSC is improved by the inclusion of extra surfactant molecules together with their counterions in the highly ordered structure.

The interaction of slightly cross-linked positively charged gels of poly(diallyldimethylammonium chloride) (PDADMAC1) with sodium salts of chloride, bromide, iodide, and acetate in aqueous media has been investigated. At the critical concentration of sodium iodide, a phase transition of the network to the collapsed state was observed. A wide hysteresis accompanied this transition. The presence of other salts did not initiate the network collapse in the investigated concentration range. A decrease in the charge density of the cationic network by copolymerization of DADMAC1 with acrylamide resulted in the disappearance of the phase transition. In this case, the usual contraction of polyelectrolyte gels in the presence of the mentioned salts was observed. The rate of volume change increased sharply with increasing concentration of sodium iodide. For some cases, two well distinct regions in the kinetic behavior were observed: a region of fast polyelectrolyte contraction and a region of slow collapse which, to our knowledge, had not been observed previously. The experimental results can be explained by the formation of ion pairs and multiplets (ionomer effect) for the sufficiently charged networks in the collapsed state. As a result, the collapsed ionomeric state of the network becomes competitive with the swollen polyelectrolyte state at high enough fractions of the ion-containing segments because of the tendency of the ion pairs to associate. A potential barrier which separates the ionomeric and the polyelectrolyte states of the gel can be used to explain the two-step kinetics of the collapse.

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The swelling behavior in solutions of sodium chloride and ionic surfactants of composites based on the clay mineral bentonite incorporated in neutral poly(acrylamide) gel and charged gels containing 10 mol % of diallyldimethylammonium chloride or a sodium salt of 2-acrylamide-2-methyl-1-propane-sulfonic acid is studied. Both the charges of the gel and of the clay play a role of the centers of adsorption of oppositely charged surfactants, cetylpyridinium chloride and sodium dodecylbenzenesulfonate. The Coulombic attraction between the ions of the cationic network and the negative charges of bentonite results in significant shrinking of the gel, which gives rise to amphoteric properties. Both the anionic and cationic surfactants, participate in a competition interaction with the charges of the amphoteric composite and their absorption leads to the marked swelling of the gel. The clay embedded in the gels can be kept in the highly dispersed state after modification with the surfactants while the suspension of the free clay coagulates.