Josmary Alejandra Velasquez Cano, Tillämpad kemi

Chelating agents are common components of aqueous surfactant formulations, yet they are typically regarded as passive additives whose role is limited to metal ion sequestration. This thesis challenges that assumption by showing that chelating agents such as glutamate diacetate and methylglycinediacetate actively interact with mixed surfactant systems and significantly influence micellar organization, dynamics, and formulation cleaning performance.

A systematic multi-scale investigation was conducted using mixed surfactant systems composed of nonionic and amphoteric surfactants with varied hydrophobic chain architectures. Diffusion NMR spectroscopy, small angle neutron scattering (SANS), cloud point measurements, viscosity analysis, and interfacial performance tests were employed to probe molecular dynamics, mesoscopic structure, and macroscopic behavior.

Diffusion NMR demonstrates that chelating agents undergo dynamic association with micellar environments, despite not forming aggregates themselves. Complementary SANS measurements reveal that this association is accompanied by changes in micellar size, shape, and internal organization, with the extent of restructuring strongly dependent on surfactant architecture, particularly hydrophobic chain branching. Linear amphoteric surfactants form mixed micelles that readily reorganize upon chelating agent addition, whereas branching reduces packing adaptability and limits structural response.

The macroscopic properties reflect these molecular interactions. Cloud point and viscosity measurements identify regimes in which chelating agents counteract classical salting-out behavior, particularly in amphoteric-stabilized systems. Changes in wetting, cleaning efficiency, and foam stability further demonstrate that chelating agent concentration governs the redistribution of surfactant between bulk and interfacial regions through micellar reorganization.

Complementary SANS measurements reveal that this association is accompanied by changes in micellar size, shape, and internal organization, with the extent of restructuring strongly dependent on surfactant architecture, particularly hydrophobic chain branching. Linear amphoteric surfactants form mixed micelles that readily reorganize upon chelating agent addition, whereas branching reduces packing adaptability and limits structural response.