Investigation of dialkyldimethylammonium bromides as stabilizers and/or emulsifiers for O/W emulsion

The emulsifying and/or stabilizing properties of dialkyldimethylammonium bromides (the alkyl chain-lengths 8, 10 and 12 carbon atoms) were investigated by dynamic light scattering technique. The multimodal size distribution, effective diameter and ζ potential of the n-tetradecane droplets in 0.5 M n-propanol (and/or the bromide) solution were studied as a function of time. The parameters were determined with the help of ZetaPals/BI-MAS (Brookhaven Instrument Co.) apparatus. Following the droplet size determination in the emulsion, the ζ potential was measured for the same sample placed in the measuring cell. The results obtained show that the surfactant molecules are easily adsorbed on the surface of newly formed oil droplets. The stabilizing properties of these bromides depend on the alkyl chain-length, the bromide concentration and the method of emulsion preparation. These bromides were also tested as the emulsifying agents, without the presence of alcohol. It was found that, at appropriate conditions, they could be used as emulsifiers only. However, more investigations are needed with other emulsion systems to better determine their emulsifying properties. A possible stabilizing mechanism by which they interact in the oil-in-water emulsions is discussed.