Study of Interaction between Cetyltrimethylammonium Bromide and Poly(acrylic acid) by Rheological Measurements

Abstract

Interaction between the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the anionic polyelectrolyte poly(acrylic acid) (PAA), having molecular weight by viscosity of 750 kDa, is investigated by rheological measurements. Upon addition of 1 or 0.5 wt % CTAB to the semidilute PAA solutions with concentration ranging from 0.04 to 0.1 wt %, the insoluble complex salts (the surfactant ion + the polyion) precipitate. In contrast, with addition of 2 or 3 wt % CTAB to the aforementioned PAA solutions, evidence of transition from shear-thinning to nearly Newtonian behavior is observed. The origin of this observation appears to lie in the fact of formation of more compact PAA/CTAB aggregates, because the radii of gyration, R g , of PAA coils have been reduced by about 60% with addition of 2 wt % CTAB by static light-scattering measurements. Furthermore, pH measurements also reveal the possible formation of "ion pairs" between PAA and CTAB as the pH values of the PAA solutions decrease with addition of CTAB. That is, the pH values of the solutions containing PAA and CTAB together are less than those of neat PAA or CTAB solutions. This implies that addition of CTAB leads to more acids dissociated from the acrylic acid monomers on the poly(acrylic acid) macromolecules.

Study of the interaction between a diblock polyelectrolyte PDMA-b-PAA and a gemini surfactant 12-6-12 in basic media

“…7), significantly different from the common stoichiometric polyelectrolyte/surfactant complexes from aqueous solution [30][31][32][33][34]. The aggregates are stable and avoided macroscopic flocculation in these systems.…”

Self‐Healing Poly(acrylic acid) Hydrogels: Effect of Surfactant

“…Hydrogels deswell in water with 60% reduction in the gel mass (m rel ¼0.37 AE0.2) after gels were immersed in a large excess of water because PAAc is a polyelectrolyte whose repeating units bear an electrolyte group and forms a complex with cationic surfactants. [16][17][18] Here, the surfactant alkyl chains are trapped electrostatically in a supramolecular polymer network formed via hydrophobic interactions. 70% CTAB bound to PAAc network chains was calculated from the nitrogen contents of the dried gels, which were subjected elemental analysis measurements using a Thermo Flash EA-1112 Series elemental analyzer.…”

Interface interaction within nanopores in thin films of an amphiphilic block copolymer and CTAB

“…Particularly, the association between polyelectrolytes and oppositely charged surfactants has been extensively studied, both in bulk and at interfaces [9]. A widely studied weak polyelectrolyte system is that of poly(acrylic acid) interactions between poly(acrylic acid) (PAA) and cetyltrimethylammonium bromide (CTAB) in aqueous solutions [10,11]. Despite a great variety of work having been carried out on polymer-surfactant systems, the detailed mechanisms of the polymer-surfactant interactions are not well understood yet [12].…”