Micelles ionization

The experimental techniques used to obtain the properties necessary to derive the kinetic constants of interest from the ultrasonic relaxation times have been previously described in detail [2,3]. Briefly, the degree of micelle ionization (P) and the binding constant (Ka) of an alcohol to mixed micelles were obtained from specific conductivity measurements as a function of surfactant concentration at various fixed alcohol compositions. The binding constant was determined from the slopes of the curves above the cmc, as proposed by Abu-Hamdiyyah et al... 

Figure 12.9. Diagram of a Section of a Micelle. Ionized fatty acids readily form such structures, but most...

Upper triplet states of biphenyls in micelles ionize to produce hydrated electrons . Diffuse reflective laser flash photolysis has been used to characterise the triplet states of p-terphenyl generated in powder systems. Other triplet states which have been characterised include those of naphthalene and acenaphthene in the solid state", those involved in photoreactions of tetracene with anthracene and 9-bromoanthrene", phenanthrene and biphenylene, highly excited triplet states... 

C=surfactant concentration). The micelle ionization degree the CMC was taken as the ratio of the slopes of the specific conductivity C curves above and below CMC. The CMC and micelle ionization degpree were also determined for SDS in the presence of N-methylpyrrolidone (NMP), as a function of the NMP concentration. Indeed NMP can be considered as the repeat unit of PVP. The comparison of the results for NMP and PVP then allows one to assess the part of the change of the micelles properties due to the polymeric character of the additive. 

Figures 1 and 2 show the changes of CMC and micelle ionization degree 3 of the various surfactant-polymer systems, and of the SDS-NMP system, as a function of the concentration Cp of polymer or NMP (in g. per 100 ml of solution).

Figure 2 Variation of the micelle ionization degree at the CMC with the polymer concentration for the systems SDS-NMP ( ) SDS-POE (O) SDS-PVP ( ) TTAB-POE (X) and TTAB-PVP (+).

The cmc and micelle ionization degrees near the cmc (9) were determined by emf measurements using a specific bromide ion electrode (Orion 9435), in conjunction with a double junction reference electrode (Orion 9002) and a millivoltmeter (Orion 701A). Some determinations were also performed by means of conductivity. It was noted that emf measurements yielded cmc values slightly lower than those obtained from the equivalent conductivity vs. (concentration) plots. This, however, is of no importance in this work where we are only interested in relative changes. 

The effect of alcohols on dilute micellar solutions is to decrease the cmc and micelle molecular weight and to increase the micelle ionization. Also, the exchange of detergent ions between micelles and surrounding solution and the micelle formation-dissolution are strongly accelerated upon addition of alcohol (micelles become more labile in presence of alcohol). All these variations can be explained on the basis of the effects associated with the dissolution of alcohol into micelles, leading to mixed alcohol + detergent micelles. 

Bales BL, Benrraou M, Zana R (2002) Krafft temperature and micelle ionization of aqueous solutions of cesium dodecyl sulfate. J Phys Chem B 106 9033-9035... 

This expression of I/Tj is veiy similar to Equation 3.9 except for the correcting term F. In Equation 3.17 a is the experimentally accessible micelle ionization degree and y=... 

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