Critical Aggregation Concentration in Mixed Solutions of Anionic Polyelectrolytes and Cationic Surfactants

Abstract

We have examined the polymer/surfactant interaction in mixed aqueous solutions of cationic surfactants and anionic polyelectrolytes combining various techniques: tensiometry, potentiometry with surfactant-selective electrodes, and viscosimetry. We have investigated the role of varying polymer charge density, polymer concentration, surfactant chain length, polymer backbone rigidity, and molecular weight on the critical aggregation concentration (Cac) of mixed polymer/surfactant systems. The Cac of these systems, estimated from tensiometry and potentiometry, is found to be in close agreement. Different Cac variations with polymer charge density and surfactant chain length were observed with polymers having persistence lengths either smaller or larger than surfactant micelle size, which might reflect a different type of molecular organization in the polymer/surfactant complexes. The surfactant concentration at which the viscosity starts to decrease sharply is different from the Cac and probably reflects the polymer chain shrinkage due to surfactant binding.

Micellar polymerization of alkylammonium 2-acrylamido-2-methylpropane sulfonates in the solvents of different polarities and properties of resulting polyelectrolyte-surfactant complexes

“…Generally, PSC based on poly-2-acrylamido-2-methylpropane sulfonate (PAMPS) and cationic surfactants can be obtained by direct mixing of water solutions of PAMPS (or its copolymers) and corresponding surfactant [18]. The stoichiometric complexes precipitate from water solutions, as a rule, but 100 % binding of surfactants can be reached not in all cases.…”

“…Many teams have been involved in the study of binding process and structure of the PSC formed by direct mixing of polyelectrolyte and oppositely charged surfactants with the use of different methods: DLS [15], SAXS and fluorescence [16,17], surface tension [18], electronic microscopy [19], and many others. The authors [20] have performed computer simulation of phases and self-assembled structures of PSC depending on relative contributions of hydrophobic and electrostatic interactions in the structure formation.…”

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

“…This effect can be observed at low surfactant concentrations where pure surfactant alone does not adsorb at the surface. [5,10] Furthermore, strong surface complexation can be inferred from the suppression of the surface tensions at low surfactant concentrations. [35] Results also showed that there is shift in CMC values of the mixtures depending on the PEI concentration.…”

“…[1][2][3] Therefore, properties of mixtures of surfactants and oppositely charged polymers in aqueous solutions gained much interest in scientific field in recent years and intensive effort has been made to characterize the nature of these interactions. [4][5][6][7][8] In the absence of polymers, surfactant molecules aggregate in aqueous solutions to form micelles at concentrations beyond a critical micelle concentration. [9,10] When water soluble polymers are added to the surfactant solutions, they may modify the free energy contributions during the surfactant micellization.…”

Colloid solution of surfactant monomers and polyelectrolyte: Polymerization and properties of the resulting interpolyelectrolyte complexes

“…Binding between surfactant molecule and polyelectrolyte is accompanied by a cooperative effect which is observed when surfactant concentration exceeds the critical aggregation concentration (CAC). This effect manifests itself in the dramatic increase in degree of surfactant-polyelectrolyte binding [7].…”