A Novel Numerical Analysis on Surface Charge Densities of an Amphoteric O/W-Type Microemulsion in the Presence of CaCl2and/or AlCl3
✍ Scribed by Keiichi Yoshihara; Nobuyuki Momozawa; Hideki Sakai; Masahiko Abe
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 210 KB
- Volume
- 191
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
fluorescence techniques for the microemulsions systems, the The effect of pH on the surface charge density of the O/W-type aggregation numbers of microemulsion may not be obtained microemulsion formed in solutions of an amphoteric surfactant, accurately due to the fact that those values include numbers (N a , N a -dimethyl-N e -lauroyllysine, DMLL)/n-octane/1-penta-of solute molecules. nol/CaCl 2 or AlCl 3 , has been investigated. A novel equation for Therefore, we have tried to establish a novel method the surface charge densities in the presence of a multivalent cation which is capable of providing the aggregation numbers of (Ca 2/ and/or Al 3/ ) has been derived taking account of the number an oil-in-water-type (O/W-type) microemulsion, by analyzof DMLL molecules bound to a multivalent cation (q). By applying ing the pH dependence of the surface charge density arising a numerical analysis of this equation, it is possible to determine from the presence of a hydrophilic group in a surfactant the intrinsic binding constants ( K) of the multivalent cation and the monovalent anion to the hydrophilic groups of DMLL and molecule (8). The ''aggregation numbers'' described the adsorption density (N) of DMLL molecules on the oil/water therein represent the numbers of surfactant molecules which interface. Furthermore, N has been found to show pH dependence. compose an O/W-type microemulsion droplet, not con-N has a maximum value around the isoelectric region (in particutaining the numbers of solute molecules. lar, pH 5-7) of DMLL molecules in the presence of CaCl 2 , whereas In our previous papers (8, 9) the effects of a symmetric N increases with increasing pH in the presence of AlCl 3 . The (1-1) electrolyte (for instance, NaCl) and pH on the phase surfactant (DMLL) numbers per O/W-type microemulsion dropbehavior, the z potential, the hydrodynamic diameter, and let, i.e., the aggregation numbers, are successfully obtained as a the surface charge density of an O/W-type microemulsion function of pH in the presence of CaCl 2 and/or AlCl 3 . ᭧ 1997 formed in solutions of an amphoteric surfactant, (N a , N a -Academic Press dimethyl-N e -lauroyllysine, DMLL)/n-octane/1-pentanol/ Key Words: multivalent cation; z potential; surface charge denbrine, have been examined. The values of the z potential and sity; binding constant; oil-in-water-type microemulsion.
the surface charge density showed slightly negative values in the isoelectric region (in particular, pH 5-7) where the net charge derived from the head groups of the surfactant be-