This document provides a comprehensive study of a carboxylate surfactant, including the critical micellar concentration, surfactant properties, and the evolution of surface tension as a function of concentration and temperature. The study is based on the Klevens relation and the packing parameter p, and provides valuable insights into the behavior of surfactants in aqueous solutions.
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[...] The surface has0 remains the same regardless of the value of in fact, for all aliphatic detergents having a single carbon chain, the v ratioc on thec is constant and equals 0.21 nm². The length of the carbon chain has no influence on the shape and size of the aggregate. Calculate the packing parameter in the three previous cases. The value of the packing parameter p is: So we can calculate the P in function of the number of carbon see Table 2. The ratio vc" on thec et a0 being constant therefore P is constant. [...]
[...] 1,674 nm In addition, the formula also has a methyl group at the end of the chain. 0,351 In their publication, Ninham and Israelachvili find a value of for the SDS2. In addition, this is still with literature or vc = 0.21 mm2. The length of an SDS chain is also the radius of the spherical micelle, so we can calculate the micelle volume in the following way: The number of SDS molecules per micelle is: There are therefore 56 SDS molecules per micelle. [...]
[...] The longer the carbon chain (nc augments), the lower the critical micellar concentration. Calculation of a required HLB We wish to stabilize a pH = 6 an oil in water emulsion, with a required HLB of 11. It is for this reason necessary to mix the tensioactive A (for = with a tensioactive B (sorbitan ester) HLB = 5. What is the HLB of tensioactive A at pH = 6 for = 8 ? The hydrophile - lipophile balance noted HLB is the ratio of the mass of the hydrophile pole to the total mass of the molecule. [...]
[...] As can be seen on figure the more the concentration increases, the more the surface tension decreases until it reaches a plateau at a concentration of 5 mmol/L-1 at a temperature of 50°C. This concentration is CMC. The SDS forms in solution in water of micelles spherical direct. Illustrate with a schema what the term 'direct micelle' means. What value is then expected for the stacking parameter? Water is a polar hydrophilic solvent, the hydrophilic parts of surfactants therefore place themselves at the periphery of the micelle and the hydrophobic parts at the center of the micelle. [...]
[...] HLB Values for Surfactants Associated with Molecular Properties4 What proportions of surfactants A and B should be introduced to stabilize the emulsion? At pH=6, the surfactant is in its basic form of type R-COO- ;Na+ (sodium decanoate, so HLBB = 19. Let xA let xB the respective molar fractions of surfactants A and B. On There is therefore 43% tensioactive A for 57% tensioactive B Stacking parameter The compound A forms in solution, a pH = spherical micelles Are these micelles direct or inverse? Justify your answer by specifying the meaning of these two terms. [...]
