Effects of Salt on Polyelectrolyte−Micelle Coacervation

Abstract

Turbidity, dynamic light scattering, and electrophoretic mobility were used to study the effects of added salt on coacervation in the system composed of the strong cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) and oppositely charged mixed micelles of Triton X-100 (TX100) and sodium dodecyl sulfate (SDS). The phase behavior in the range of ionic strengths from 0.05 to 0.60 M includes regimes of soluble complex formation, coacervation, and precipitation. The corresponding phase boundaries are determined from differential turbidity curves. The shift of the phase boundaries to higher ratios of SDS:TX100 with increase in salt concentration is explained on the basis of electrostatic screening. The width of the coacervation region is found to increase with ionic strength. These observations are consistent with previous reports of the “salt suppression” and “salt enhancement” of coacervation. In the coacervation region, the electrophoretic mobility is found to be close to zero. At higher and lower ionic strengths, soluble complexes are positively or negatively charged, respectively. It is suggested that the principal factor governing coacervation in this system is electroneutrality of the polyion−micelle complex which in turn depends on the charge and number of bound micelles.

Role of Polyelectrolyte Persistence Length in the Binding of Oppositely Charged Micelles, Dendrimers, and Protein to Chitosan and Poly(dimethyldiallyammonium chloride)

“…55 Results and Discussion Figure 1 shows "Type 1" turbidimetric titration plots for SDS/TX100 mixed micelles with PDADMAC or chitosan samples of 1% and 12% degrees of acetylation in 0.4 M NaCl, the ionic strength previously used to explore complexation in the PDADMAC and SDS/TX100 system. 56,57 For comparison of binding affinities of the three polycations with SDS/TX100 micelles, the mole fraction of SDS at the point of incipient complexation, Y c , was determined from such data using a procedure described elsewhere. 37 Since Y c is proportional to the critical micelle surface charge density (σ c ), it is inversely related to the binding affinity of the polycation, in the sense that polyelectrolyte factors promoting binding, such as linear charge density, allow for binding to more weakly charged micelles.…”

Linear viscoelasticity of complex coacervates

“…The qualitative nature of turbidity-style measurements allows a phenomenological characterization of coacervate phase behavior, rather than a more direct quantification of the binodal phase space [8,15,71,[73][74][75][76][77]83,88,[91][92][93]104,105,108,112,114,. Typical characterization experiments include evaluation of the stoichiometric ratio of polycation to polyanion, the effect of increasing salt concentration, and the effect of variable pH.…”

Anomalous Protein–Protein Interactions in Multivalent Salt Solution

“…3,4 This has been observed for a variety of macromolecules and ions, such as latex particles, polyelectrolytes, DNA, proteins, multivalent ions and surfactant micelles. [4][5][6][7][8][9][10][11][12][13] The mechanism relies mainly on strong spatial correlations between ions adsorbed at the surface of the macromolecule, a feature which is not taken into account by generic mean-field theories. [1][2][3][14][15][16] Human Serum Albumin (HSA) is a 585 residues long, 66.5 kDa protein, which is involved in the transport of diverse molecules in blood plasma.…”