Gemini-type

Direct hydrothermal synthesis. Prepared using titanium isopropoxide (triethanolaminato) and TEOS as the sources of Ti and Si, respectively, and the Gemini-type surfactant 18-12-18 or cetyl-benzyl dimethylammonium chloride (CBDAC) as a template. In the grafting method, silicious MCM-48 first prepared and then the dry surface grafted with titanium isopropoxide... 

Diquatemary ammonium halides of the gemini type (Chapter 12) are particularly effective micellar catalysts for nucleophilic substitution and decarboxylation reactions (Bunton, 1971, 1972, 1973). 

Kunieda s group reported numerous viscoelastic worm-like micellar systems in the salt-free condition when a lipophilic nonionic surfactant such as short hydrophilic chain poly(oxyethylene) alkyl ether, C EOni, or N-hydroxyethyl-N-methylaUcanolamide, NMEA-n, was added to the dilute micellar solution of hydrophilic cationic (dodecyltrimethylammonium bromide, DTAB and hexade-cyltrimethylammonium bromide, CTAB) [12-14], anionic (sodium dodecyl sulfate, SDS [15, 16], sodium dodecyl trioxyethylene sulfate, SDES [17], and Gemini-type [18]) or nonionic (sucrose alkanoates, C SE [9, 19], polyoxyethylene cholesteryl ethers, ChEO [10, 20], polyoxyethylene phytosterol, PhyEO [11, 21] and polyoxyethylene sorbitan monooleate, Tween-80 [22]) surfactants. The mechanism of formation of these worm-Hke stmctures and the resulting rheological behavior of micellar solutions is discussed in this section based in some actual published and unpublished results, but conclusions can qualitatively be extended to aU the systems studied by Kunieda s group. 

Kunieda, H., Masuda, N., and Tsubone, K. (2000) Comparison between phase behavior of anionic dimeric (Gemini-type) and monomeric surfactants in water and water-oil. Langmuir, 16, 6438-6444. 

Kunieda, H., Kaneko, M., Feng,)., and Tsubone, K. (2002) Formation of microemulsions with Gemini-type surfactant./. Oleo Sci., 51, 761-769. 

Acharya, D.P., Kunieda, H., Shiba, Y., and Aratani, K. (2004) Phase and rheological behavior of novel Gemini-type surfactant systems. /. Phys. Chem. B., 108,1790-1797. 

Aramaki, K., Aratani, K., and Kunieda, H. (2005) Interfadal properties and foam stability effect of novel gemini-type surfactant in aqueous solutions./. Colloid Interface Sci., 291, 236-243. 

Recently dimeric cholesterol-based derivatives were reported as a new class of organogelator architecture. The examples pubhshed so far display a A(LS)2 structure in which a central unit A is sandwiched by two cholesterol moieties. Moreover, all such gemini -type cholesterol-based structures reported to date are based on the cholesterol unit having the natural (S) configuration at C-3. They are listed below according to the main functional characteristics of the central unit. 

Sugihara, G. Miyazono, A. Nagadome, S. Oida, T. Hayashi, Y. Ko, J-S. Adsorption and Micelle Formation of Mixed Surfactant Systems in Water. II A Combination of Cationic Gemini-type Surfactant with MEGA-10. /, Oleo Sci. 2003,52,449-461. 

A Gemini-type compound (two carbon hydrogen chains connected to a neutral molecule segment or spacer, via ionic groups) (p-Phenyldimethyl)bis(octadecyldimethylammonium) dibromide, as in Scheme 1. 

Specific surface areas of nanocomposites and metal oxide samples were determined by a Micromeritics gas adsorption analyzer (Gemini type 2375) at 77 0.5 K in liquid nitrogen. Prior to measurements the samples were pretreated in a vacuum at 120 °C for 2 h. The sample vessel was loaded with about 0.1-0.7 g of samples. The adsorption isotherms were analyzed by means of the Brunauer-Emmett-Teller (BET) equation. 

Banno T, Kawada K Matsumura S. 2010. Creation of novel green and sustainable Gemini-type cationics containing carbonate linkages. Journal of Surfactants and Detergents 13(4) 387-398. 

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