Controlling aggregation of nonionic surfactants using mixed glycol media

Area of Science:

• Physical Chemistry
• Materials Science
• Colloid and Surface Chemistry

Background:

• Nonionic surfactants are crucial in various industrial applications.
• Controlling surfactant aggregation behavior is essential for optimizing their performance.
• Ethylene glycol (EG) and propylene glycol (PG) are miscible hydrogen-bonding solvents.

Purpose of the Study:

• To investigate the aggregation of nonionic surfactants in mixed ethylene glycol/propylene glycol (EG/PG) solvents.
• To determine the influence of solvent composition on surfactant aggregation extent and structure.
• To explore the potential of using EG:PG ratio as a control mechanism for surfactant aggregation.

Main Methods:

• Utilized three nonionic surfactants with varying hydrocarbon chain lengths (C12E8, C14E8, C16E8) and a common E8 ethoxylated headgroup.
• Employed small-angle neutron scattering (SANS) in deuterated EG/PG solvent mixtures at different PG concentrations (mol %).
• Analyzed SANS data using cylinder and ellipsoidal form factors to model aggregate structures.

Main Results:

• Increasing PG concentration in EG/PG mixtures led to a significant decrease in SANS intensity, indicating reduced aggregation.
• Observed a transition in aggregate shape from cylindrical (EG-rich) to ellipsoidal (PG-rich) as solvent composition changed.
• Demonstrated that surfactant aggregation is dependent on the EG:PG ratio in the mixed solvent system.

Conclusions:

• Nonionic surfactant aggregation occurs in EG/PG solvent mixtures.
• The EG:PG ratio provides an effective method to control the extent and potentially the structure of surfactant aggregates.
• This tunability allows for switching surfactant aggregation 'on' or 'off' as needed for specific applications.