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CTAB/water/chloroform reverse micelles: a closed or open association model?
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SYSNO ASEP 0382282 Druh ASEP J - Článek v odborném periodiku Zařazení RIV J - Článek v odborném periodiku Poddruh J Článek ve WOS Název CTAB/water/chloroform reverse micelles: a closed or open association model? Tvůrce(i) Klíčová, L. (CZ)
Šebej, P. (CZ)
Štacko, P. (CZ)
Filippov, Sergey K. (UMCH-V) RID, ORCID, SAI
Bogomolova, Anna (UMCH-V) RID
Padilla, M. (CZ)
Klán, P. (CZ)Zdroj.dok. Langmuir - ISSN 0743-7463
Roč. 28, č. 43 (2012), s. 15185-15192Poč.str. 8 s. Jazyk dok. eng - angličtina Země vyd. US - Spojené státy americké Klíč. slova CTAB ; reverse micelles ; AFM Vědní obor RIV CD - Makromolekulární chemie CEP GAP108/12/0640 GA ČR - Grantová agentura ČR Institucionální podpora UMCH-V - RVO:61389013 UT WOS 000310484300009 DOI https://doi.org/10.1021/la303245e Anotace The micellization of cetyltrimethylammonium bromide (CTAB) in chloroform in the presence of water was examined. Three scenarios of the reverse micelle formation, the closed, open and Eicke’s association models, were considered in the interpretation of the experimental data. The growth of the aggregates was observed through the changes of NMR signals of associated water, probing the microenvironment of the premicellar aggregates and the interior of reverse micelles. This technique if combined with isothermal titration calorimetry (ITC) revealed that hydrated surfactant premicellar aggregates are already present at ~ 6 mM CTAB. NMR, ITC and conductometry were used to determine the critical micelle concentration (cmc) to be~ 40 mM CTAB. It is suggested that the variation of the cmc values reflects the fact that the NMR analysis indicated the beginning of the reverse micelle formation, whereas conductometry and ITC measurements provided the upper limit and an average value of a so-called apparent cmc, respectively. The cmc values were found to be unaffected by the water content. The presence of reverse micelles, the existence of multiple equilibria, and high polydispersity of the samples were evidenced by DOSY NMR spectroscopy. As a result, we validated Eicke’s association model, according to which cyclic inverse micelles are formed by a structural reorganization of linear associates within a narrow concentration range, called the apparent cmc. New experimental results have also been gained for micellization of cetyltrimethylammonium chloride (CTAC) in chloroform in the presence of water; a similar mechanism of reverse micelle formation has been suggested. Pracoviště Ústav makromolekulární chemie Kontakt Eva Čechová, cechova@imc.cas.cz ; Tel.: 296 809 358 Rok sběru 2013
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