Nanoscale Supramolecular Ordering in Gel−Surfactant Complexes:  Sodium Alkyl Sulfates in Poly(diallyldimethylammonium Chloride)

Abstract

Studies of slightly cross-linked polycationic gels interacting with anionic surfactants have been performed by using random copolymers of poly(diallyldimethylammonium chloride) (PDADMACl) and polyacrylamide (PAAm) with varying content of PDADMACl and degree of cross-linking. Gel samples which had been fully swollen in water were placed in aqueous solutions of sodium alkyl sulfates (octyl (SOS), decyl-(SDCS), dodecyl (SDS), tetradecyl (STS), and hexyl (SHS) sulfates). The degree of the sample volume contraction depends on the PDADMACl content. The collapsed gel-surfactant complexes were studied using synchrotron small-angle X-ray scattering. All studied samples containing PDADMACl exhibited pronounced supramolecular nanostructures. The gel-SDCS complex exhibited a cubic structure with a periodicity (7.75 nm) of approximately 4 times the surfactant molecular length, while the gel-SDS, gel-STS, and gel-SHS complexes showed hexagonal supramolecular ordering with a periodicity of approximately 2 times the surfactant molecular length. The d spacing of the longest periodicity in the complexes was dependent on the PDADMACl content and the surfactant. The d spacing generally increased with decreasing PDADMACl (charge) content and increasing number of carbon atoms in the surfactant alkyl chain.

Interactions between cationic starch and anionic surfactants

“…Benjamin Chu and his co-workers have extensively studied ordered polyelectrolyte/surfactant structures. They studied poly(diallylmethylammonium chloride, PDADMAC) gels w ith different sodium alkyl sulphates (Sokolov et al, 1996(Sokolov et al, , 1998 and found that these complexes have structure of hexagonal close-packed of cylindrical micelles with SDS, STS, and SHS. The SDS complex was found to have a cubic structure.…”

A bicontinuous structure in some systems with cubic mesophases

“…The hydrophobic interactions between aliphatic chains of surfactant are also important. Subsequent investigations have confirmed these conclusions [12][13][14][27][28][29]. It should be underlined that, although the scattering by PCCs is registered with SAXS diffractometers, the similar supramolecular structures are analyzed by the usual diffraction methods [8,[16][17][18], not excepting some peculiarities inherent in low-molecular weight crystals [19,43].…”

“…Previous experimental research on polymer colloid complexes (PCC), consisting of a linear or network polyelectrolyte, an oppositely charged surfactant and water, has resulted in the following observations: Various three-dimensional (3D) mesophases, such as face centered cubic (FCC) [11], primitive cubic (PC) [12], and cubic [13] can be obtained in a polyelectrolyte sample, which has no regular structure originally, after the interaction with surfactants. The change of the water content causes the reversible transition HEX ↔ LAM [14], observable directly during experimental studies of one sample, whereas the transition CP to HEX, due to the formation of the complex between a cationic gel and sodium alkyl sulfates [13], takes place in different samples, with increasing length of the hydrophobic surfactant residue measured in the number of CH 2 groups from 10 to 12 and more.…”

“…The change of the water content causes the reversible transition HEX ↔ LAM [14], observable directly during experimental studies of one sample, whereas the transition CP to HEX, due to the formation of the complex between a cationic gel and sodium alkyl sulfates [13], takes place in different samples, with increasing length of the hydrophobic surfactant residue measured in the number of CH 2 groups from 10 to 12 and more.…”

“…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.…”