Adsorption and Micelle Formation of Mixed Surfactant Systems in Water. III. A Comparison between Cationic Gemini / Cationic and Cationic Gemini / Nonionic Combinations

Abstract

A surface tension study (drop volume method) was performed at 30 on micellization and adsorbed film formation of a mixed system of a cationic Gemini-type surfactant with a cationic surfactant in comparison with another mixed system of the same Gemini-type surfactant with a nonionic surfactant. The systems studied were Bis-ammonium Gemini derived from tartaric acid dibromide salt [BAGTB, 1,4-Bis(trimethylammonio)-2,3-dodecyloxy butane dibromide] with hexadecyltrimethylammonium bromide (HTAB): BAGTB / HTAB mixed system and with n-decanoyl-N-methylglucamide (MEGA-10): BAGTB/MEGA-10 mixed system. The data of surface tension (g ) vs logarithmic molality plots as a function of mole fraction of surfactant 2 (2 corresponds to HTAB or MEGA-10), X 2 , enabled us to determine the critical micellization concentration (CMC), the surface tension at CMC (g CMC ), surface excess concentration (G t ), the mean molecular surface area (A m ), the partial molecular area (PMA), and the measures of efficiency of adsorption (pC 20 = log C 20 ) and CMC/C 20 which is available for evaluating the facilitating balance between adsorption and micellization. In addition, a newly defined measure of synergism in surface activity, i. e., the minimum surface Gibbs energy (G ) was employed. Based on these data, the examination of synergism in micelle formation and in surface tension reduction elucidated that the Gemini-type surfactant does not exhibit any positive synergism for either BAGTB / HTAB or BAGTB / MEGA-10 mixed systems. Most of these parameters are found to depend conspicuously on the mixing ratio for both mixtures; indicating that the state of adsorbed film is divided into three ranges of X 2 ; the lower, the middle and the higher. The compositions of micelles formed at CMC (Y 2 ) and of adsorbed film (Z 2 ) equilibinated with bulk solution at a fixed surface tension were estimated.

A Review of Recent Studies on Aqueous Binary Mixed Surfactant Systems

“…It is noted here that, as described later, for the mixed system of a cationic Gemini type surfactant: BAGTB with MEGA-10 36,37) , synergism in surface tension reduction was found to be negligible or rather weak from the examination of partial molecular area (PMA) and the minimum surface Gibbs free energy at air/water interface (G min (S) ). In the case of BAGTB/MEGA-10, the g -ln m t curves of mixed systems showed neither a minimum around CMC nor notable synergism when compared with those of the respective single systems: i.e., g -ln m t curves of different mixtures fit between those of the two single systems and they appeared in the order of mole fraction 36) .…”

“…In regard to effectiveness of adsorption, i.e. the total surface excess G t = G 1 + G 2 , the following relation can be derived for such a mixed system as composed of a 1-1 electrolyte type ionic surfactant 1 and a nonionic surfactant 2 36,37) .…”

“…It is noted here that X 2 can be related to composition in adsorbed film Z 2 , as will be shown later, so G t is also expressed as a function of Z 2 36,37) . The total surface excess, G t together with s defined as (s = (dg/dlnm t )/RT), was thus evaluated using the slopes of the straight line just below the CMC of g -ln m t curves ( ), and We have proposed a thermodynamic quantity for the evaluation of synergism upon mixing, that is, so called minimum surface free energy, G min (S) which is defined as follows 36,37) .…”

“…All the materials used for this series work have been described in terms of their sources and purities in the respective reports [35][36][37][38][39][40] . It may be worth noting the surface tension measurements even in the present review paper.…”

“…Previously, we have reported some studies performed by means of surface tension measurements as a series of works, i.e., adsorption and micelle formation of mixed surfactant systems in water I: a combination of top-heavy type anionic surfactants 35) , II: a combination of cationic Gemini-type surfactant with MEGA-10 36) , III: a comparison between cationic Gemini/cationic and cationic Gemini/ nonionic combinations 37) , and IV: three combinations of one of the most typical anionic surfactant, sodium dodecylsulfate (SDS) with MEGA-8, -9 and -10 (MEGA-n's) 38) , in addition to three combinations of zwitterionic surfactant, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid (CHAPS) which is a derivative of cholic acid in pH 7.2 phosphate buffer solution. These works have followed the previous surface tension study on binary mixed systems of…”