Ordered Nonstoichiometric Polymer Gel−Surfactant Complexes in Aqueous Medium with High Ionic Strength

Abstract

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.

Assembled Materials: Polyelectrolyte-Surfactant Complexes

“…Thus, the assembly structure of the polyelectrolyte-gel±surfactant complexes would be affected. Mironov et al [63] have studied the structures of surfactant aggregates in the PDADMACl gel±SDBS complexes prepared in aqueous media with high ionic strength. When excess SDBS molecules were available in the external solution, the presence of NaCl could induce a non-stoichiometric complex whose lamellar structure was more ordered than that of the complexes prepared in the absence of salts.…”

Formation of ordered microstructures in polyelectrolyte/surfactant systems: linear anionic polyelectrolytes and cetylpyridinium chloride

“…[13][14][15][16] It is well established that such systems can give rise to highly ordered mesoscopic structures. The structures of the known crosslinked gel-surfactant complexes show either lamellar ordering, [13] cubic organization, [11,14] or hexagonal arrangement. [15,16] At the same time, the interactions between thermoreversible gels (physical networks) and surfactants remain a completely unexplored research field.…”

A bicontinuous structure in some systems with cubic mesophases

“…The real magnitudes, apparently, will not significantly differ from the calculated, and all the corrections (variations of molar composition, water content, and density provided the absence of jump-like structural changes) are introduced elementary. We have neglected errors connected with a non-homogeneous distribution of water over a gel body [14], and also with a possible non-stoichiometric structure of similar complexes [30,31]. All these assumptions have also been used for the PCC of PDADMACL/DS [13].…”

“…The pioneer work [26] by A.T. Dembo and his colleagues has stimulated subsequent extensive structural research on PCCs [11][12][13][14][27][28][29][30][31][32][33][34][35]. As a result of all these studies, new nanostructures that had not been described earlier for the given types of materials have been revealed.…”

“…The d-spacing generally increases with increasing water content [14] or the number of carbon atoms in the surfactant alkyl chain [13,26,27], and also with decreasing charge content in polymer chains [13]. Decreasing the charge content results in disordering the PCC structure [13] whereas in solutions of high ionic strength and significant excess of surfactant molecules in the external solution, highly ordered PCCs can be formed [30].…”