Multiscale Microstructure, Composition, and Stability of Surfactant/Polymer Foams

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Polymer Science

Background:

• Polymer additives are used to improve foam stability.
• Quantifying polymer incorporation and understanding structural changes in foams remain challenging.
• Sodium dodecyl sulfate (SDS) and hydroxypropyl methylcellulose (HPMC) are common foam-forming agents.

Purpose of the Study:

• To investigate the amount and retention of HPMC in SDS/HPMC foams.
• To elucidate the structural modifications induced by HPMC in foam films.
• To correlate structural changes with foam stability.

Main Methods:

• Flow injection QTOF mass spectrometry to quantify HPMC-to-SDS ratio.
• Small-angle neutron scattering (SANS) with contrast matching to analyze micellar structure and film thickness.
• Foam stability measurements over time.

Main Results:

• Mass spectrometry confirmed HPMC incorporation and retention in foam, with ratios matching the parent solution.
• SANS revealed HPMC leads to thicker foam films and altered micellar structure.
• Increased film thickness correlated with enhanced foam stability in the initial 15-20 minutes.

Conclusions:

• Combined mass spectrometry and SANS provide a comprehensive understanding of SDS/HPMC foam structure and composition.
• HPMC incorporation thickens films, improving short-term foam stability.
• This approach offers mechanistic insights for rational foam design and formulation guidance.