Aggregation, cationic surfactant polyelectrolyte

CONCLUSIONS This Study shows that fluorescence probing techniques are useful and powerful tools for investigation of conformational transitions of polyelectrolytes as induced by cationic surfactants, pH or other means. Studies on the interaction of cationic probes with polyelectrolytes provide useful information on the intermediates that lie between A states and B states. It is concluded that the conformational transition induced by pH is a progressive process over several pH units. Studies on the interaction of cationic surfactants with PMA at pH 8 show that the aggregates formed are large loose structures, while the interior of the aggregate has a hydrophobicity that is similar to that of a micelle. 

Kogej K, Skerjanc J. Effect of polyelectrolyte on the aggregation of cationic surfactants in aqueous solutions. Acta Chim Slov 1998 45 443—453. 

The cationic charge on a polymer affects its behavior considerably when surfactants are included in formulations. Cationic polymers (a member of the broader class of polymers termed polyelectrolytes) usually interact strongly with anionic surfactants, weakly with cationic surfactants, and unpredictably with nonionic and amphoteric surfactants (14,167-169). Anionic surfactant binds to cationic polymers at concentrations well below the critical micelle concentration (cmc). The low surfactant concentration where polymer and surfactant begin to interact is known as the critical aggregation concentration (cag). 

Jain NJ, Trabelsi S, Guillot S, McLoughlin D, Langevin L, Letellier P, Turmine M (2004) Critical aggregation concentration in mixed solutions of anionic polyelectrolytes and cationic surfactants. Langmuir 20 8496... 

With the discussion of previous sections as background, the observed enthalpy of binding may be considered to contain three contributions (1) the enthalpy change due to the atmospheric binding of surfactant cations to the PSS- anion, A/7a, (2) the heat effect accompanying the aggregation of the bound surfactant molecules into polyelectrolyte induced micelles, A//m, and (3) the enthalpy change, A// due to other specific interactions of surfactant micelles with the polyelectrolyte chain ... 

In many formulations, polymers and surfactants are present and interaction between them can produce remarkable effects. Several structures can be identified, and the aggregates produced can have profound effects on particle deposition. With many hair shampoos, conditioning agents are added that are mostly polyelectrolytes with cationic charges, which are essential for strong attachment to the negatively charged keratin surface. 

Dedinaite, A. and Claesson, P. M., Interfacial properties of aggregates formed by cationic polyelectrolyte and anionic surfactant, Langmuir, 16, 1951-1959 (2000). 

Here we focus on one aspect of the association between polyelectrolytes and surfactants at a solid surface, namely the structure of the adsorbed layer and its relation to the internal structure of the aggregates formed in bulk solution. The system we will discuss consists of a cationic polyelectrolyte, PCMA (Fig. 5), having one charge per segment that is preadsorbed onto negatively charged mica surfaces. The effect of addition of an anionic surfactant, SDS, was explored. It should be noted that no polyelectrolyte was present in the solution during these experiments, whereas the surfactant was present in bulk solution and was also incorporated in the adsorbed layer. 

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