Packing within the Microbubbles Surfactant Monolayer

2 MOLECULAR PACKING WITHIN THE MICROBUBBLE S SURFACTANT MONOLAYER 

The above-mentioned artificial microbubble surfactant mixtures, and other successful mixtures found for stable microbubble production (ref. 544-546), all contain saturated glycerides (with acyl chain lengths greater than 10 carbons) combined with cholesterol and cholesterol derivatives (cf. Chapters 9 and 10, and ref. 544). As described earlier, long chain lengths in nonionic (or even unionized) surfactants are known to favor the formation of both large, rodlike micelles (as opposed to small spherical micelles) and macroemulsions (as opposed to microemulsions) (see 

Sections 10.2 and 9.1, respectively). Hence, the observed generation of a concentrated gas-in-liquid (macro)emulsion which interacts readily with simultaneously formed large (rodlike) micelles, using the above surfactant mixtures, is to be expected from and confirms such molecular packing considerations. 

3 REPULSIVE HEAD-GROUP INTERACTIONS AND MONOLAYER CURVATURE 

Still another factor favoring the formation of coarse gas-inliquid emulsions, as demonstrated in Chapter 10, is that all the surfactants employed were nonionic. This feature results in weaker repulsive interactions among the (polar, but uncharged) head groups in the surfactant monolayer surrounding each artificial 

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