Binding of Polycarboxylic Acids to Cationic Mixed Micelles: Effects of Polymer Counterion Binding and Polyion Charge Distribution

Abstract

Mixed micelles of cetyltrimethylammonium chloride (CTAC) and n-dodecyl hexaoxyethylene glycol monoether (C 12 E 8 ) bind to polyanions when the mole fraction of the cationic surfactant exceeds a critical value (Y c ). Y c corresponds to a critical micelle surface charge density at which polyelectrolyte will bind to this colloidal particle. Turbidimetric titrations were used to determine Y c for such cationic-nonionic micelles in the presence of acrylic acid and acrylamido-2-methylpropane sulfonate homopolymers (PAA and PAMPS, respectively) and their copolymers with acrylamide, as function of pH, ionic strength, and polyelectrolyte counterion. In 0.20 M NaCl, Y c for PAA is found to be remarkably insensitive to pH, i.e., virtually independent of the apparent polymer charge density app . On the other hand, the expected inverse relationship between Y c and app is observed either for PAA when NaCl is replaced by TMACl (tetramethylammonium chloride), or when app is manipulated using acrylic acid/acrylamide copolymers at high pH. The effective charge density of PAA is thus seen to be suppressed by specific sodium ion binding, indicating that the influence of salts on the interaction of polycarboxylic acids with colloidal particles may differ qualitatively from their effect on the analogous behavior of strong polyanions. Comparisons between homo-and copolymers of acrylic acid were carried out also to test the hypothesis that the "mobility" of charges on PAA at moderate pH (degree of ionization less than unity) could make this "annealed" polymer exhibit the behavior of a more highly charged one. The results, while consistent with this expectation, were obscured by the likely effect of copolymer sequence distributions.

The aqueous phase behavior of polyion–surfactant ion complex salts mixed with nonionic surfactants

“…Another interesting trend in Dubin's work is that the critical mole fraction of the ionic surfactant needed for complexation was reduced as the amount of simple salt was decreased. 21 This is in line with our study, which illustrates that in the absence of simple salt phase separation occurs over most of the mixing range in the dilute regime.…”

“…We will focus on some of the systems that we find relevant to compare with our study. 20,21 In ref. 20 it was found that when the PEO-chain length is increased, more charged surfactant was needed to reach phase separation.…”

Potential use of pearl millet ( Pennisetum glaucum (L.) R. Br.) in Brazil: Food security, processing, health benefits and nutritional products

“…For this reason, the study of the effect of pH on the interaction between proteins is a relevant factor because in addition to influencing the density of biopolymer loads, it also determines the range of stability of the coacervate and the best conditions for its formation (Diarrassouba et al, 2015;Li et al, 2012;Schmitt, Sanchez, Desobry-Banon, & Hardy, 1998). However, a slight increase in turbidity observed even before reaching the pI of Lys may be explained by the fact that during the coacervation process, non-electrostatic interactions may be involved in addition to electrostatic interactions, mainly consisting of hydrogen bonds occurring at a pH above the pI of the protein and which are favored by a low density of charges, as reported in the literature (Vries & Cohen Stuart, 2006;Jones & Mc Clements, 2010;Schmitt & Turgeon, 2011;Girard, Turgeon, & Gauthier, 2002;Yoshida, Sokhakian, & Dubin, 1998). Liu et al (2015) studied the influence of urea, which is capable of breaking hydrogen bonds in the complex formation between BSA and a flaxseed polysaccharide.…”

Adsorption of Polyelectrolytes on Calcium Carbonate – Which Thermodynamic Parameters are Driving This Process?

“…The anionic charge of BNS decreases in the order of pH 9 → pH 12.6 → pH 12.6 + 1 g/L Ca 2+ . This trend can be explained by increased counter ion condensation around the polymer at increased ionic strength of the pore solution as a result of BNS being a strong polyelectrolyte where all sulfonate groups are already fully dissociated at pH ≥9 …”