Premicelle Formation of Double-chain Surfactants and Bile Salts in the Neighborhood of the CMC Region: Application of a Differential Conductivity Technique to the Determination of Micellization Parameters

Abstract

It has been demonstrated that differential conductivity, dκ/dC, is useful for experimentally extracting the contribution of micellar aggregates from the conductivity data of an ionic surfactant solution in which aggregates and monomers coexist. This extraction allows us to treat the micellization process using a simple two-state model (nS→M) instead of the general mass action model of micellization (nS+qG→M). As a result, the three parameters of micellization, i.e., aggregation number (n), micellization constant, and ionization degree (α) of micelles, for homologous double-chain surfactants and bile salt derivatives can be determined. It was found that when the side-chain was long enough, the double-chain surfactants examined formed highly ionized (α=0.6-0.9) and small (ca. n=20) aggregates, regarded as premicelles.

Effect of Spacer Structures on the Interfacial Adsorption and Micelle Properties of Quaternary Ammonium Salt-Based Gemini Surfactants

“…2C 12 (2/2) showed a higher CMC value than gemini surfactants with cyclic spacer of benzene rings. The α of 2C 12 (2/2) obtained from the conductivity was close to 1, indicating that the surfactant formed loose micelles in solution . This result obtained for 2C 12 (2/2) was supported by the free energy of micellization |Δ G mic °|, which was smaller than those of monomeric and other gemini surfactants.…”

“…The α of 2C 12 (2/2) obtained from the conductivity was close to 1, indicating that the surfactant formed loose micelles in solution. 40 This result obtained for 2C 12 (2/2) was supported by the free energy of micellization |ΔG mic °|, which was smaller than those of monomeric and other gemini surfactants. 2 C 1 2 ( 2 / 2 -N -2 ) w i t h t h e 1 -m e t h y l -4 -[ 2 -( N , Ndimethylammonio)ethyl]piperazin-1-ium spacer showed smaller α and larger |ΔG mic °| values than 2C 12 (2/2).…”