Interaction of guar gum galactomannans with the anionic surfactant sodium lauryl ether sulphate

The interaction between galactomannans, guar gum (GG) with sodium lauryl ether sulphate (SLES) was demonstrated using conductometric, tensiometric, pyrene probe and 1H NMR analyses. SLES and GG formed aggregates and reduced the surface tension at a critical aggregation concentration. The interaction was attributed to the presence of surfactant ethoxyl (EO) groups, since in conductometric, tensiometry and pyrene probe analyses using the non-ethoxylated form, sodium lauryl sulphate – SLS, no aggregation was observed. The aggregates formed between SLES and GG presented a negative zeta potential indicating that the polymer is surrounded by SLES and according to the dynamic light scattering analysis (DLS), presented a size of approximately 26 nm. The determination of the thermodynamic parameters showed that the aggregation occurs spontaneously and is a driven-enthalpy and entropy process. SLES and GG interaction could be explored to produce formulations with lower concentrations of surfactants, using commonly used thickeners as GG. •Galactomannans and SLES interaction were demonstrated using different techniques.•Galactomannans and SLES interacts forming aggregated structures.•The GG and SLES aggregates presented interfacial properties.•The aggregates are stable and presented a size of approximately 26 nm.•The interaction is non-ionic and may involve SLES EO groups.