Group contributions to the partial molar volume of ionic organic solutes in aqueous solution

Thermodynamic Studies of Aqueous m–s–m Gemini Surfactant Systems

“…The additivity model assumes that each group in the molecule interacts independently with the solvent. Clearly this assumption does not hold for -CH 2 -groups adjacent to quaternary ammonium centers, which show negative deviations in volume up to the β-carbon (27). In bifunctional molecules this effect is magnified due to the overlap of the regions of influence arising from the substituents, particularly for small values of s, and the contribution for a -CH 2 -group would be expected to have a smaller volume than 15.8 cm 3 mol −1 in some instances.…”

“…Values of V 0 for the bolaform electrolytes were obtained from Gianni et al (27) Table 1, Ref. (27)). The value of 206.9 cm 3 mol −1 was then used in Eq.…”

“…As mentioned above, the apparent molar volume of the surfactant at infinite dilution can be estimated using additivity methods. Two methods were applied; one according to a proposal by Frindi et al (4) and a second based on the volume contribution of chemical groups from Gianni et al (27). The first method considers the partial molar volume of the gemini monomer as consisting of contributions from the corresponding mono-quaternary surfactant V 0 (OTAB, DeTAB, DTAB, CTAB) (where OTAB is octyltrimethylammonium bromide, DeTAB is decyltrimethylammonium bromide, DTAB is dodecyltrimethylammonium bromide, and CTAB is cetyltrimethylammonium bromide) and the partial molar volume contributions from the appropriate number of methylene groups (V 0 (CH 2 ) = 15.8 cm 3 mol −1 (27)) and hydrogen atoms (V 0 (H) = 10.7 cm 3 mol −1 (4)) according to the relation The values of V 0 for OTAB (225.1 cm 3 mol −1 ), DeTAB (256.9 cm 3 mol −1 ), and DTAB (288.4 cm 3 mol −1 ) were previously reported (28).…”

Studies of the Aggregation Behavior of Cyclic Gemini Surfactants

“…Evidence that micelles do not form for the 3-spacer, while they appear to form for the 4-and 6-spacers, is also obtained from experimental V φ,M (42 • C) data (Table 3). In the case of the 3-spacer the value of V φ,M is taken above the concentration where a slight break occurs in the specific conductance vs concentration plot.…”

Effect of the concentration and composition on the size and shape of micelles of sodium oleate–cetyltrimethylammonium bromide mixtures

“…The partial molar volume of CTAB is PMV CTAB = 365.4 cm 3 /mol [23], which by subtraction of the Br-PMV (29.2 cm 3 /mol [24]) gives PMV CTA+ = 336.2 cm 3 /mol. For the oleate ion, the partial molar volume was estimated as 315.0 cm 3 / mol with the group contributions to the partial molar volume method developed by Gianni and Lepori [25,26], and taking into account that on micellization the PMV increases in 8% above that of unmicellized surfactant molecules [23,27]. With these data the volumes of the micellized molecules were computed as V CTAB = 0.5076 nm 3 and V NaOL = 0.4756 nm 3 .…”