Self-aggregation, dilational surface rheology and foaming properties of 1-O-dodecyl diglyceryl ether compared to n-dodecyl-β-D-maltoside and pentaethyleneglycol monododecyl ether

Diglyceryl alkyl esters are good foaming agents but the ester linker can be sensitive to pH, chemicals and temperature unlike the ether function. In this work, the foaming properties of a diglyceryl ether, namely 1-O-dodecyl diglyceryl ether (C12Gly2), are compared to those of n-dodecyl-β-D-maltoside (C12Glc2) and pentaethyleneglycol monododecyl ether (C12E5). The self-aggregation behaviour of C12Gly2 and adsorption at the air-water interface has been first investigated. For the three surfactants, the dynamic response of the interface, measured in oscillatory bubble interfacial rheology experiments below CMC, is compared and put in relation with their foaming properties. In particular, the foamability by air sparging at a concentration of 10 times the CMC, the foam stability over 1h and the foam density are quantified. It is shown that C12Gly2 forms liquid crystals at low concentration (∼10 CMC). C12E5, with a lower elasticity high frequency limit ε0, forms unstable foam with quick drainage and breakdown, whereas higher ε0 surfactants C12Gly2 and C12Glc 2 form much more stable foams, resulting from hydrogen bonds between the polar heads of C12Glc 2 and C12Gly2. Differences in C12Gly2 and C12Glc2 foams lay in initial bubble size (smaller for the C12Glc 2). In C12Gly2 foam, the main destabilization phenomenon is coalescence over drainage, and the foam volume only decreases by 30% in 1 hour.