Adsorption of alkyl trimethylammonium bromides at the air/water interface
2008 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, no 2, 395-401 p.Article in journal (Refereed) Published
A number of features of the adsorption of alkyl trimethylammonium bromides with n(c) = 10, 12, 14, and 16 at the air/water interface were studied. First, the adsorption isotherms were calculated front experimental surface tension vs concentration curves by means of the Gibbs equation. Second, a novel method was used to estimate the adsorption free energy change. From the analysis of these data it was concluded that the hydrophobic driving force for the adsorption first increases with increasing adsorbed amount and then levels off in a plateau, which holds true for all four homologues. This peculiar behavior was interpreted by the formation of a thin liquid-like alkane film at the air/water interface once a certain adsorbed amount is exceeded. The hydrophobic contribution to the standard free energy change of adsorption was compared with those values previously determined for alkyl sulfate homologues. This comparison suggests that the alkyl trimethylammonium type surfactants behave as if their alkyl chain was approximately one methylene group shorter than those of the corresponding alkyl sulfates.
Place, publisher, year, edition, pages
2008. Vol. 317, no 2, 395-401 p.
adsorption, surfactants, adsorption free energy, alkyl trimethylammonium bromides
IdentifiersURN: urn:nbn:se:kth:diva-33358DOI: 10.1016/j.jcis.2007.10.007ISI: 000251556100004ScopusID: 2-s2.0-36148994728OAI: oai:DiVA.org:kth-33358DiVA: diva2:414654
QC 201105042011-05-042011-05-042011-05-04Bibliographically approved