Deuterium Isotope Effects on the Interaction between Hyperbranched Polyethylene Imine and an Anionic Surfactant

Abstract

Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, polyethylene imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated using potentiometric titration and eletrophoretic mobility measurements. In the basic pH range, a significantly higher fraction of the amine groups was found to be protonated when the PEI was dissolved in D2O compared to H2O at the same pH/pD. The difference in polymer charge in the two solvents decreases gradually with decreasing pH, and it completely diminishes at around pH = 4. Electrophoretic mobility measurements of PEI/SDS complexes at different pH values correlated very well with these observations. At pH/pD approximately 9 a much higher mobility of the PEI/SDS complexes was found in D2O than in H2O at low surfactant concentrations, and the charge neutralization point shifted to a considerably larger surfactant concentration in heavy water. These results can be explained by the significantly higher charge density of the PEI in D2O compared to H2O. However, at the natural pH/pD as well as at pH = 4 and pD = 4 conditions the PEI molecules have roughly equal charge densities, which result in very similar charged characteristics (mobilities) of the PEI/SDS complexes as well as the same charge neutralization SDS concentration. It can be concluded that extreme care must be taken in the general analysis of those experiments in which weak polyelectrolyte/surfactant aggregates are investigated in heavy water, and then these observations are correlated with structures of the same system in water.

Interaction of Sodium Dodecyl Sulfate with Poly(ethyleneimine) in Bulk Solution and at the Air-Solution Interface

“…The aggregates change to a more complex three-dimensional structure with increasing surfactant concentration. [32] Similarly, in the current study three dimensional structures were observed at a SDS concentration starting from 4 Â 10 À3 M in the presence of PEI (400 ppm) at pH 9.…”

“…As the surfactant association proceeds three-dimensional aggregates, involving several polyelectrolyte chains and SDS, can be formed. [32] In the current study SDS=PEI complexation at high pH is driven by the cooperative interaction of the surfactant via uncharged nitrogen atoms of the amine groups. [33,4] Additionally, hydrophobic interactions is the mechanism that dominates SDS=PEI interaction at high pH.…”

“…The behavior of SDS=PEI mixtures at very high surfactant concentrations can be interpreted by the resolubilization due to repulsive micellar interaction. [4] Bastardo et al [32] reported that a decrease in pH results in a strong association between PEI and SDS. The initial binding of SDS at pH 4.9 does not result in any changes in the polyelectrolyte conformation.…”

Interaction between casein and sodium dodecyl sulfate

“…The interactions between copolymers with nonionic and oppositely charged surfactants have been studied extensively [8][9][10][11][12][13][14][15]. Since the interaction is believed to be weak or nonexistent, interactions between polyelectrolytes and surfactants with the same charge are less extensively studied.…”

Synthesis and characterization of hyperbranched cationic polyelectrolytes via aqueous self‐condensing atom transfer radical polymerization

“…BASF and Hyperpolymers commercialized the hyperbranched polyethyleneimine (PEI) via the self‐condensing proton‐transfer polymerization of ethylene imine. Such PEIs as well as their quaternized derivatives have been well studied in various applications 19–23…”