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Purification, Surface Tensions, and Miscibility Gaps of Alkyldimethyl and Alkyldiethylphosphine Oxides
Author(s) -
Blunk Dirk,
Tessendorf Renate,
Buchavzov Natalie,
Strey Reinhard,
Stubenrauch Cosima
Publication year - 2007
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-007-1030-x
Subject(s) - chemistry , alkyl , miscibility , adsorption , pulmonary surfactant , surface tension , solubility , homologous series , steric effects , polymer chemistry , crystallography , organic chemistry , thermodynamics , polymer , biochemistry , physics
Abstract Alkyldimethyl (C n DMPO) with chain lengths of n = 8 (octyl), 10 (decyl), 12 (dodecyl), and 14 (tetradecyl) as well as alkyldiethyl (C n DEPO) phosphine oxides with chain lengths of n = 10, 12, and 14 were synthesized and purified to study how the adsorption properties and the location of the miscibility gap of these surfactants depend on the size of the head group and on the length of the alkyl chain. After surfactant purification, the surface tension isotherms were determined from which the cmc, the minimum surface tension σ cmc , the maximum surface concentration Γ max , and the minimum surface area A min were obtained. As expected, for one homologous series, a decrease in the cmc and an increase in Γ max was observed with increasing alkyl chain length. For two surfactants of the same alkyl chain length, the cmc values of the C n DEPO surfactants are approximately two times lower than those of the C n DMPO surfactants. However, the Γ max values of C n DEPO are lower than those of C n DMPO as two ethyl chains are sterically more demanding than two methyl chains. In addition to the adsorption properties, the location of the miscibility gap as a function of the alkyl chain length and the head group size was studied. Its location depends on the total number of carbon atoms and not primarily on the length of the main alkyl chain. This observation reflects the decreasing water solubility which can be tuned by increasing the length of either the main alkyl chain or of the shorter head group chains.