Temperature- and pH-dependent interaction between an alkyl ethoxylate surfactant and an acid azo dye

Alkyl ethoxylate surfactants (AEOs) are widely used due to their mildness and low toxicity. In aqueous solution, AEOs usually show a lower critical solution temperature (LCST). AEOs are nonionic and therefore not very sensitive to changes in pH or ionic strength. However, a pH-responsivity can be introduced by adding an acidic solute, rendering the system responsive to two triggers: Temperature and pH. Both parameters affect the mechanism of solubilization of the solute (e.g. dye molecules) and therefore its interaction with substrates (e.g. textiles, hair fibers). We will investigate the morphology of dye/AEO co-assemblies to understand the mechanism of dye solubilisation and its response to changes in temperature and pH. This will aid the targeted design of more efficient dyeing-systems.