Adsorption and Adsolubilization by Monomeric, Dimeric, or Trimeric Quaternary Ammonium Surfactant at Silica/Water Interface

✍ Scribed by Kunio Esumi; Masaya Goino; Yoshifumi Koide

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 132 KB
• Volume: 183
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.0577

✦ Synopsis

been studied (1, 2) from the viewpoints of the hydrophobic Adsorption of monomeric, dimeric, or trimeric quaternary amchain length of surfactants, the ionic strength, and the pH monium surfactant on silica from its aqueous solution has been of media. Most of the studies so far have been limited to investigated by measuring adsorption density, z potential, and single-chain surfactants. Recently, we have studied (3, 4) dispersion stability. The monomeric (dodecyltrimethylammonium adsorption of single-chain, double-chain, and triple-chain bromide, 1RQ), dimeric (1,2-bis(dodecyldimethylammonio)cationic surfactants on silica and found that the physicoethane dibromide, 2RenQ), and trimeric (methyldodecylbis[2chemical properties of the adsorbed layer are significantly dimethyldodecylammonio)ethyl]ammonium tribromide, affected by their chain number, similar to those in aqueous 3RdienQ) surfactants are used in this study. The amounts adsolutions. Further, Zana et al. (5, 6) synthesized a new type sorbed at saturation decrease with increasing dodecyl chain numof surfactant, dimeric and trimeric surfactants in which two ber of the surfactants from 1RQ to 2RenQ and 3RdienQ. Silica

or three quaternary ammonium species are linked at the level suspensions by adsorption of the surfactants exhibit a process of dispersion-flocculation-redispersion with the surfactant concen-of the head groups by a hydrocarbon spacer, and reported tration for the three surfactants which can be correlated with the that their aqueous solution properties are quite different from change in z potentials. ESR measurements using methyl 12-doxylthose of conventional surfactants. Similarly, surfactants havstearate show that the microviscosities in 2RenQ-and 3RdienQing a rigid spacer of benzene have also been synthesized adsorbed layers are greater than that in the 1RQ-adsorbed layer. (7). This type surfactant is called a ''gemini'' surfactant Under a constant feed concentration of 2-naphthol, the adsolubiand has physicochemical properties different from those of lized amounts of 2-naphthol increase, reach a maximum, and then the multichain surfactants in which the hydrocarbon chains decrease with the surfactant concentration for the three surfacare attached to one ammonium head group. From the viewtants. The ratio of maximum amount of 2-naphthol adsolubilized point of surfactant structure, it is still worthwhile that the to the adsorbed amount of surfactant on silica increases with an adsorption of gemini surfactants on particles be characterincrease in the dodecyl chain number of the surfactants from 1RQ ized.

to 2RenQ and 3RdienQ. In addition, from a two-step process of Surfactant-adsorbed layers formed on solid particles by adsorption-adsolubilization, it is suggested that 2RenQ and adsorption of surfactants provide hydrophobic circumstances 3RdienQ adsorb on much stronger than 1RQ, keeping 2-naphthol that facilitate incorporation of water-insoluble compounds.