Use of isothermal titration calorimetry to study surfactant aggregation in colloidal systems

• Published in: Biochimica et biophysica acta Vol. 1860; no. 5; pp. 999 - 1016
• Main Authors: Loh, Watson, Brinatti, César, Tam, Kam Chiu
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2016
• Subjects: Calorimetry; Calorimetry - methods; Colloids; DNA; DNA - chemistry; energy; enthalpy; entropy; Hydrophobic and Hydrophilic Interactions; Micelles; Micellization; nanoparticles; Nanoparticles - chemistry; Polymers; proteins; Proteins - chemistry; Static Electricity; Surface-Active Agents - chemistry; Surfactants; Temperature; Thermodynamics; titration; X-radiation; Thermodynamics; Calorimetry; Surfactants; Polymers; Micellization
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2015.10.003

Isothermal titration calorimetry (ITC) is a general technique that allows for precise and highly sensitive measurements. These measurements may provide a complete and accurate thermodynamic description of association processes in complex systems such as colloidal mixtures. This review will address uses of ITC for studies of surfactant aggregation to form micelles, with emphasis on the thermodynamic studies of homologous surfactant series. We will also review studies on surfactant association with polymers of different molecular characteristics and with colloidal particles. ITC studies on the association of different homologous series of surfactants provide quantitative information on independent contribution from their apolar hydrocarbon chains and polar headgroups to the different thermodynamic functions associated with micellization (Gibbs energy, enthalpy and entropy). Studies on surfactant association to polymers by ITC provide a comprehensive description of the association process, including examples in which particular features revealed by ITC were elucidated by using ancillary techniques such as light or X-ray scattering measurements. Examples of uses of ITC to follow surfactant association to biomolecules such as proteins or DNA, or nanoparticles are also highlighted. Finally, recent theoretical models that were proposed to analyze ITC data in terms of binding/association processes are discussed. This review stresses the importance of using direct calorimetric measurements to obtain and report accurate thermodynamic data, even in complex systems. These data, whenever possible, should be confirmed and associated with other ancillary techniques that allow elucidation of the nature of the transformations detected by calorimetric results, providing a complete description of the process under scrutiny. This article is part of a Special Issue entitled Microcalorimetry in the BioSciences — Principles and Applications, edited by Fadi Bou-Abdallah. •Studies of surfactant aggregation to form micelles, with emphasis on the thermodynamics of homologous surfactant series.•We review studies on surfactant association with polymers of different molecular characteristics and colloidal particles.•Benefits of using ancillary techniques to clearly identify the nature of the processes identified by calorimetry.