Purification, Surface Tensions, and Miscibility Gaps of Alkyldimethyl and Alkyldiethylphosphine Oxides

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 r cmc , the maximum surface concentration G 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 G 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 G 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.

A disjoining pressure study of foam films stabilized by mixtures of a nonionic (C12DMPO) and an ionic surfactant (C12TAB)

“…The respective cmc values are listed in Table 1 and are used throughout as reference concentrations for foam film measurements. Note that our results are in agreement with those from literature, where one finds cmc (C 12 TAB) = 1.5 Â 10 À2 M [39,46] and cmc (C 12 DMPO) = 2.6 Â 10 À4 M [14] and 4.0 Â 10 À4 M [19]. However, to date no study exists on the adsorption behaviour of C 12 DMPO/C 12 TAB mixtures.…”

“…The nonionic surfactant dodecyldimethyl phosphineoxide (C 12 DMPO) was synthesised and purified as described elsewhere [14]. The cationic dodecyl trimethylammonium bromide (C 12 TAB) (purity > 98% AT) was purchased from Fluka and purified by recrystallizing it three times with pure acetone to which traces of ethanol were added.…”

“…Phosphineoxide surfactants are ideal candidates for fundamental research as they are pH-and temperature stable and as they can easily be synthesized and purified [12][13][14]. There is considerable knowledge regarding the surface and bulk properties of C 12 DMPO with extensive surface tension [14][15][16][17][18][19][20][21] and surface rheology [22][23][24][25][26][27][28][29] studies in the past.…”

Partition coefficients of nonionic surfactants in water/n-alkane systems

“…The alkyl dimethyl phosphineoxides C n DMPO (C 12 DMPO and C 14 DMPO) were synthesized and thoroughly purified by means of several recrystallizations (group of Dr. D. Blunk, Universität zu Köln, Germany). The purity degree was checked via miscibility gap or static surface tension measurements [17]. The n-alkanes (n-hexane, >99%, Fluka; n-octane, >99.5%, Sigma; n-decane, >99%, Sigma; n-dodecane, >98%, Fluka) were used as purchased.…”

Foaming properties of mixtures of a non-ionic (C12DMPO) and an ionic surfactant (C12TAB)

“…The non-ionic surfactant dodecyldimethyl phosphineoxide (C 12 DMPO) was synthesised and purified as described elsewhere [44]. The cationic dodecyltrimethylammonium bromide (C 12 TAB) (purity $99%) was purchased from Aldrich and purified by threefold recrystallizing from pure acetone to which traces of ethanol were added.…”