The area/molecule of a surfactant is an important factor. What is the effect of this parameter on foaming?
When a bubble leaves the liquid, it is enveloped by a double layer of oriented molecules, inside which there is some liquid. If this film is strong, the foams are stable. Typically, such films are created by surfactant + polymer. Therefore, the area per molecule of surfactant is large. Great strength in guaranteeing the Marangoni effect.
My experience is a bit different. Most foams for consumer products (e.g., shampoos, dishwashing liquids) often contain a mixture of surfactants, typically an anionic surfactant and another surfactant that interacts with the anionic surfactant via ion-dipole interactions (e.g., with an amine oxide), or electrostatic interactions (e.g., anionic-cationic surfactant mixtures). Each of these mixtures decrease the area.molecule at the air-water interface. So yes, in the absence of polymers there is a benefit to decreasing the area per molecule at the air-water interface.
Generally, increasing the surface area per surfactant molecule at the liquid-air interface decreases the foaming ability of the molecule. However, this is not true in the strict sense. In actuality, the foaming tendency of a surfactant system must increase with the ease of which the system can be explained using the Gibbs Marangoni effect. Greater the surface tension gradient within the desired range, the roll up (thinning) of the interface without complete detachment, higher is the foaming power of the surfactant. This is surely achieved by increasing the temperature of the system, that improves the thermodynamic spontaneity of surfactant adsorption at the interface, and also increases surface curvature area in contact with air.
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