Ultrastable and Responsive Foams Based on 10-Hydroxystearic Acid Soap for Spore Decontamination

Area of Science:

• Surfactant chemistry
• Materials science
• Biotechnology

Background:

• Renewed interest exists in fatty acid soaps as surfactants.
• Hydroxylated fatty acids, like 12-hydroxystearic acid (12-HSA), possess unique surfactant properties due to their chiral alkyl chains.
• 10-hydroxystearic acid (10-HSA) is a novel hydroxylated fatty acid, readily derived from oleic acid via microbial processes.

Purpose of the Study:

• To investigate the self-assembly and foaming characteristics of R-10-HSA soap in aqueous solutions for the first time.
• To compare the properties of R-10-HSA soap with the well-established 12-HSA soap.
• To evaluate the potential of R-10-HSA based foams for cleaning applications.

Main Methods:

• A multiscale approach combining microscopy, small-angle neutron scattering (SANS), and wide-angle X-ray scattering (WAXS).
• Rheology experiments and surface tension measurements as a function of temperature.
• Assessment of spore removal from model surfaces using R-10-HSA foams under static conditions via foam imbibition.

Main Results:

• Both R-10-HSA and 12-HSA soaps formed multilamellar micron-sized tubes.
• Distinct nanoscale self-assembly structures were observed between R-10-HSA and 12-HSA, likely due to the enantiomeric purity of R-10-HSA versus the racemic mixture of 12-HSA.
• Stable foams derived from R-10-HSA soap demonstrated efficacy in removing spores from model surfaces.

Conclusions:

• R-10-HSA soap exhibits unique self-assembly behavior influenced by its enantiomeric purity.
• The formation of stable foams from R-10-HSA soap suggests its viability for cleaning applications.
• This study highlights R-10-HSA as a promising bio-based surfactant with potential industrial applications.