Isohexadecane nanoemulsions

The results with isohexadecane are summarised in Table 14.2. As with the hexadecane system, the droplet size and polydispersity index were decreased with increases in surfactant concentration. Nanoemulsions with droplet radii of 25-80run were obtained at 3-8% surfactant concentration. It should be noted, however, that nanoemulsions could be produced at lower surfactant concentration when using isohexadecane, when compared to results obtained with hexadecane. This could be attributed to the higher solubility of isohexadecane (a branched hydrocarbon), the lower HLB temperature, and the lower interfacial tension. 

The stability of nanoemulsions prepared using isohexadecane was assessed by following the droplet size as a function of time. Plots of versus time for four... 

In contrast to the results obtained with hexadecane, the addition of squalane to the O/W nanoemulsion system based on isohexadecane showed a systematic decrease in Ostwald ripening rate as the squalene content was increased. The results are included in Figure 14.14, which shows plots of versus time for nanoemulsions containing varying amounts of squalane. The addition of squalane up to 20% based on the oil phase showed a systematic reduction in ripening rate (from 8.0 to 4.1 x 10 m s i). It should be noted that when squalane alone was used as the oil phase, the system was very unstable and showed creaming within 1 h. The results also showed that the surfactant used was unsuitable for the emulsification of squalane. 

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