Volume and Expansivity Changes of Micelle Formation Measured by Pressure Perturbation Calorimetry

We present the application of pressure perturbation calorimetry (PPC) as a new method for the volumetric characterization of the micelle formation of surfactants. The evaluation is realized by a global fit of PPC curves at different surfactant concentration ranging, if possible, from below to far ab...

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Bibliographic Details
Published in:Langmuir 2011-03, Vol.27 (5), p.1693-1699
Main Authors: Fan, Helen Y, Nazari, Mozhgan, Chowdhury, Saria, Heerklotz, Heiko
Format: Article
Language:English
Subjects:
Calorimetry
Chemistry
Colloidal state and disperse state
Colloids: Surfactants and Self-Assembly, Dispersions, Emulsions, Foams
Exact sciences and technology
General and physical chemistry
Hydrophobic and Hydrophilic Interactions
Maltose - analogs & derivatives
Maltose - chemistry
Micelles
Micelles. Thin films
Pressure
Surface-Active Agents - chemistry
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Summary:We present the application of pressure perturbation calorimetry (PPC) as a new method for the volumetric characterization of the micelle formation of surfactants. The evaluation is realized by a global fit of PPC curves at different surfactant concentration ranging, if possible, from below to far above the CMC. It is based on the knowledge of the temperature dependence of the CMC, which can for example be characterized by isothermal titration calorimetry. We demonstrate the new approach for decyl-β-maltopyranoside (DM). It shows a strong volume increase upon micelle formation of 16 ± 2.5 mL/mol (+4%) at 25 °C, and changes with temperature by −0.1 mL/(mol K). The apparent molar expansivity (E S) decreases upon micelle formation from 0.44 to 0.31 mL/(mol K) at 25 °C. Surprisingly, the temperature dependence of the expansivity of DM in solution (as compared with that of maltose) does not agree with the principal behavior described for polar (E S(T) decreasing) and hydrophobic (E S(T) increasing) solutes or moieties before. The results are discussed in terms of changes in hydration of the molecules and internal packing of the micelles and compared with the volumetric effects of transitions of proteins, DNA, lipids, and polymers.
ISSN:0743-7463
1520-5827
DOI:10.1021/la1042487