Micelles, hexadecyltrimethylammonium bromide-cetyl alcohol

The initial descending leg is interpreted as the solubilization process. If micelles are present, the added oil will be solubilized. Also, the added oil may be solubilized in the hexadecyltrimethylammonium bromide-cetyl alcohol complex. That the sol-... 

The parameters P(l) and P(2) define the solubilization stage. In the absence of micelles, there is no solubilization of the oil phase. Therefore, in this case, there are no values of P(l) and P(2), e.g., as for the 1 6 hexadecyltrimethylammonium bromide-cetyl alcohol molar ratio. 

The conductance of the bromide counterion associated with the emulsifier micelles is 4.212x10% divided by the conductance readout (8). The concentration of hexadecyltrimethylammonium bromide in the micelles at a 1 3 molar ratio is (53.1-41.0)/4.212xl03 or 2.87x10"%. The total concentration of hexadecyltrimethylannnaniun bromide in the system is (0.15/364.6) (1000/25) or 1.65x10"%. The solute and micellar hexadecyltrimethylammonium bromide concentrations are subtracted from the total concentration to give the concentration in the crystalline rodlike particles. Table III gives these concentrations for the hexadecyltrimethylammonium bromide-cetyl alcohol ratios of 1 6 to 1 0.33. 

Figure 10 shows that varying the hexadecyltrimethylammonium bromide concentration at the same hexadecyltrimethylammonium bromide-cetyl alcohol ratio changed the conductometric titration curve. For 0.4% hexadecyltrimethylammonium bromide at the 1 3 molar ratio, the conductometric titration curve showed no initial descending leg, suggesting that this system contained no emulsifier micelles. In comparison, the conductometric titration curve for 0.6% hexadecyltrimethylammonium bromide-cetyl alcohol at the... 

The parameter P(2), the solubilization constant, has a finite value when micelles are present in the mixed emulsifier system. The smaller the value of P(2), the smaller the concentration of micellar hexadecyltrimethylammonium bromide and the better the balance between the hexadecyltrimethylammonium bromide and cetyl alcohol in the crystalline rodlike particles. 

Figure 11 shows that the conductometric titration curves for 0.6% hexadecyltrimethylammonium bromide were essentially the same for molar ratios of 1 6 and 1 7. In both cases, the absence of a descending leg suggests that no micelles were present. Therefore, a further increase in the cetyl alcohol concentration resulted in an increase of that incorporated into the rodlike particles, which diminishes the crystallinity but gives no significant change in the conductometric titration curve. 

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