Nonionic ortho ester surfactants as cleavable emulsifiers.

Area of Science:

• Colloid and Surface Chemistry
• Polymer Science
• Organic Chemistry

Background:

• Acid labile surfactants with ortho ester linkages are utilized as emulsifiers.
• Emulsions were formulated using squalane as the oil phase.
• Cationic polymers, including polyamines and their hydrophobically modified counterparts, were incorporated.

Purpose of the Study:

• To investigate the behavior of acid labile surfactants in emulsions stabilized by cationic polymers.
• To evaluate the impact of surfactant hydrolysis on emulsion properties like droplet size and stability.
• To understand the role of cationic polymers in modulating surfactant degradation kinetics.

Main Methods:

• Characterization of linear and branched nonionic ortho ester surfactants using (1)H NMR.
• Emulsion preparation and stability assessment.
• Monitoring surfactant hydrolysis and degradation products via gas chromatography and (1)H NMR.
• Droplet size measurements and kinetic stability studies under acidic conditions.

Main Results:

• Spontaneous hydrolysis of ortho ester surfactants occurred under acidic conditions, leading to polymer-stabilized emulsions with surfactant degradation products.
• Ortho ester surfactants are complex mixtures, identifiable by (1)H NMR based on the central methine proton's chemical shift.
• The presence of cationic polymers resulted in a slower rate of surfactant breakdown, attributed to hydrophobic shielding.
• A strong correlation was observed between increased droplet size and the extent of surfactant decomposition.

Conclusions:

• Cationic polymers influence the hydrolysis rate of acid labile surfactants in emulsions.
• Surfactant decomposition significantly affects emulsion stability and droplet size.
• The findings provide insights into the design and application of responsive surfactant systems.