Effects of Polyelectrolytes on the Structures and Interactions of Surfactant Aggregates

Abstract

Aqueous solutions of sodium polyacrylate (NaPA) have been mixed with different phases of the system water−cetyltrimethylammonium bromide (CTABr). In all mixtures, the surfactant ions (CTA+) associate to form micelles. The polyions (PA-) bind to these micelles, displace their counterions, and bridge them together. The replacement of micellar counterions changes the micellar shapes. The bridging may change the distances between micelles, and cause them to separate into a concentrated phase; in this case excess water and salt are released in a dilute aqueous phase. The structures of the concentrated phases have been determined. At low water contents, the hexagonal, nematic, and micellar phases of the polymer-containing system merge with the corresponding phases of CTABr/water. At high water content, the concentrated phases that separate are closer to the hexagonal and cubic phases of cetyltrimethylammonium acetate/water.

DNA-lipid systems: A physical chemistry study

“…The surfactant molecules are in an aggregated form in the concentrated phase, but different types of aggregates are formed in different systems; micelles of different shape, cubic liquid crystalline phase, (normal or inverse) hexagonal phase and lamellar phase are the cases described so far (2)(3)(4)(5)(6)(7)(8)(9). The factors determining the type of aggregate formed can be assumed to be the same as for simple surfactant systems, a statement supported by some recent reports (8).…”

“…Depending on the balance between the polar and nonpolar parts, a large number of self-assembly structures is (43)(44)(45). Only recently have we started to learn about how polymers modify surfactant self-assembly structures (2,3,9,46). The first studies probing the surfactant aggregates in the concentrated phase in a phase separated polyion-surfactant system revealed by fluorescence that the aggregates are discrete and have low aggregation numbers; they are small globular, closely spherical micelles (47)(48)(49)(50).…”

Evidence of overcharging in the complexation between oppositely charged polymers and surfactants

“…In biophysics, comprehensive studies have been dedicated to the cooperative condensation of DNA with multivalent counterions [3][4][5] or with cationic liposomes 1,[6][7][8][9] . In material science, electrostatic layer-by-layer deposition yielding polyelectrolyte multilayers have been achieved for encapsulation purposes and colloidal stabilization [10][11][12] .When an ion-containing polymer solution is mixed to a dispersion of oppositely charged colloids, a phase separation usually follows [13][14][15][16][17][18][19][20][21][22][23] . At the mixing, the solution becomes turbid, and after centrifugation it displays two separated phases.…”

DNA gel particles: An overview

“…When the surfactant/polyelectrolyte attraction overcomes their solubility in the solvent, associative phase separation occurs [29][30][31][32][33][34]. This results in the formation of concentrated liquid, gel, or precipitate phases in equilibrium with a dilute liquid [29][30][31][32][33][34][35][36][37].…”