Surfactant Gemini

A gemini surfactant is a dimeric molecule consisting of two hydrophobic tails and two head groups, linked together with a short spacer [14]. This is illustrated below for a molecule containing two cationic head groups (separated by two methylene groups) with two alkyl chains  

Holmberg, K., Jonsson, B., Kronberg, B., and Lindman, B. (2003) Surfactants and Polymers in Solution, 2nd edn, John Wiley, Sons, Ltd. 

McCutcheon. Detergents and Emulsifiers, Allied Publishing Co., New Jersey (published annually), van Os, N.M., Haak, J.R., and Rupert, L.A.M. (1993) Physico-Chemical Properties of Selected Anionic, Cationic and Nonionic 

Porter, M.R. (1994) Handbook of Surfactants, Chapman Hall, Blackie. 

Linfield, W.M. (ed.) (1967) Anionic Surfactants, Marcel Dekker, New York. Lucasssen-Reynders, E.H. (1981) 

A concise account of the structure, properties and uses of gemini surfactants is given by Rosen [60]. 

Dow Chemical Co. (1960) Alkylene oxides. Tech Bull. 125-273-60, Midland, MI. 

Nakaya, H., Adachi, I., Aoki, N. and Kanao, H. (to Lion Corp.) (1989) Jap Patent 03185095A2. 

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Li ZX, Dong CC, and Thomas RK. 1999. Neutron reflectivity studies of the surface excess of Gemini surfactants at the air-water interface. Langmuir 15(13) 4392 -396. 

Torres, J.L., Piera, E., Infante, M.R., Clapes, P. (2001). Purification of non-toxic, biodegradable arginine-based gemini surfactants, bis(Args), by ion exchange chromatography. Prep. Biochem. Biotechnol. 31(3), 259-274. 

Furthermore, Oda et al. pointed out that there are two topologically distinct types of chiral bilayers, as shown in Figure 5.46.165 Helical ribbons (helix A) have cylindrical curvature with an inner face and an outer face and are the precursors of tubules. These are, for example, the same structures that are observed in the diacetylenic lipid systems discussed in Section 4.1. By contrast, twisted ribbons (helix B) have Gaussian saddlelike curvature, with two equally curved faces and a C2 symmetry axis. They are similar to the aldonamide and peptide ribbons discussed in Sections 2 and 3, respectively. The twisted ribbons in the tartrate-gemini surfactant system were found to be stable in water for alkyl chains with 14-16 carbons. Only micelles form... 

Figure 5.46 Schematic representation of helical and twisted ribbons as discussed in Ref. 165. Top Platelet or flat ribbon. Helical ribbons (helix A), precursors of tubules, feature inner and outer faces. Twisted ribbons (helix B), formed by some gemini surfactant tartrate complexes, have equally curved faces and C2 symmetry axis. Bottom Consequences of cylindrical and saddlelike curvatures in multilayered structures. In stack of cylindrical sheets, contact area from one layer to next varies. This is not the case for saddlelike curvature, which is thus favored when the layers are coordinated. Reprinted with permission from Ref. 165. Copyright 1999 by Macmillan Magazines.

In this chapter, we have surveyed a wide range of chiral molecules that self-assemble into helical structures. The molecules include aldonamides, cere-brosides, amino acid amphiphiles, peptides, phospholipids, gemini surfactants, and biological and synthetic biles. In all of these systems, researchers observe helical ribbons and tubules, often with helical markings. In certain cases, researchers also observe twisted ribbons, which are variations on helical ribbons with Gaussian rather than cylindrical curvature. These structures have a large-scale helicity which manifests the chirality of the constituent molecules. 

Synthesis using Gemini surfactant (bromide salt of... 

Fig. 2.9.40. General structural formula of polyethoxylated non-ionic gemini surfactant... 

Fig. 2.9.41. APCI-FIA-MS(+) overview spectrum of gemini surfactant blend Surfynol (2,4,7,9-tetramethy]-5-decyne-4,7-polyol) [16].

The 2,4,7,9-tetramethyl-5-decyne-4,7-diol mixture which belongs to the new group of polyethoxylated non-ionic gemini surfactants was examined by APCI-FIA-MS-MS(+). The [M + NH4]+ homologue ion at m/z 640 (number of PEG units x +y = 9) of the Surfynol 440 blend was fragmented in CID experiments on a TSQ. The product ion spectrum of this homologue is presented in Fig. 2.9.42. 

Fig. 2.11.35. General structural formula of anionic gemini surfactants (R = spacer).

Fig.2.11.37. ESI-FIA-MS-MS(—)(CID) product ion mass spectrum of [M — H] gemini surfactant parent ion at mlz 639 of di-protonated (1,4-cyclohexylene-dimethylene)-bis(dodecylphosphate)) anion fragmentation behaviour in the inset [64].

Fig. 2.12.1. Chemical structure of different classes of cationic surfactants (a) quaternary ammonium surfactants (quats) (b) dialkylcarboxyethyl hydroxyethyl methyl ammonium surfactants (esterquats) (c) alkyl polyglycol amine surfactants (d) quaternary perfluoro-alkyl ammonium surfactants (e) N, N, N1, JV -tetramethyl-iV, iV -didodecyle-l,3-propane-diyle-diammonium dibromide (cationic gemini surfactant). R = alkyl or benzyl group.

Fig. 2.12.9. (a) FIA-ESI-MSC+) overview spectrum of cationic gemini surfactant lV,lV,lV,lV,-tetramethyl-lV,iV,-dicloclecyle-l,3-propane-cliyle-diammonium dibromide C12H25-N (CH3)2-CH2-CH2-CH2-N (CH3)2-C12H25 2Br- (b) FIA-ESI-MS(+) mass spectrum of cationic gemini surfactant as in (a) in the presence of methane sulfonic... 

Fig. 2.12.10. FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of [M - 2Br]2+ parent ion (mJz 234) of cationic gemini surfactant general formula Ci2H25-N (CH3)2-CH2-CH2-CH2-N (CH3)2-C 12H25 fragmentation behaviour under CID shown... 

Various classes of cationic surfactants, including quats, esterquats, alkyl ethoxy amines, quaternary perfluoroalkyl ammoniums and gemini surfactants have been analysed extensively with LC—MS and LC—MS—MS techniques, and their spectra have been fully characterised. Different ionisation methods have been applied for the detection of such surfactants, including API techniques (APCI and ESI) in negative and positive modes of operation. In addition, detailed examples regarding MS—MS fragmentation of these compounds have been reported and presented in this chapter. 

Non-ionic surfactants containing an amide group This group of non-ionic surfactants comprises different sub-groups, such as polyethoxylated amides, fatty acid diethanol amides, aminosu-gars and dialkyl disugar amides (gemini surfactants). 

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