Due to wide range of applications, much emphasis has been placed on understanding the physicochemical behavior of polyelectrolyte/surfactant complex coacervates. In this study we have explored the correlation of the physicochemical behavior of coacervates normalized with critical overlap concentration of the polymer.The effect of molecular weight effect was studied for cationic hydroxyethylcellulose. The effect of charge distribution was studied between the randomly charged poly(methacrylamidopropyltrimethyl ammonium chloride)(MAPTAC) and tri-cluster charged poly(methacrylamide propyl (methoxy-carbonyl-methyl)dimethyl ammonium chloride) (AMT). The effect of rigidity and hydrophilicity/hydrophobicity of the polyelectrolyte backbone was studied by comparing and contrasting flexible/hydrophobic MAPTAC and semi rigid/hydrophilic Cationic HEC. All of these polyelectrolytes were interacted with sodium dodecyl sulfate (SDS) surfactant over a wide range of polymer and surfactant concentrations. The adsorption behavior was analyzed by surface tension measurements, while, the complexation in the bulk was examined by rheological measurements. Fluorescence measurement techniques were additionally used to analyze the effect of charge localization on the structure of the polyelectrolyte/surfactant complexes.Contrary to prior studies, our investigation revealed that above the critical aggregation concentration, the surface tension increased with increase in the SDS concentration and this became more pronounced with increase in polyelectrolyte molecular weight. This increase can be explained by intermolecular association preferentially occurring in the solution phase between the polymer and surfactant through hydrophobic association of the bound surfactants. Increase in molecular weight increased this intermolecular association and the surface tension increased with increase in the molecular weight.Fluorescence measurements revealed that charge localization enhances SDS aggregation. Rigidity and hydrophilicity of the polymer backbone increased the surface tension in the one phase region. Both the viscosity and storage modulus of the cationic HEC coacervate phase is higher than MAPTAC. We deduce from this that the MAPTAC chain collapses and phase-separates with addition on surfactant in the one phase region.

Effect of polyelectrolyte concentration, molecular weight, charge localization, and backbone rigidity/hydrophobicity on complex coacervate formation and rheology

248th National Meeting (2014)

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