Cationic gemini surfactant

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. 

These three problems will be dealt with in this presentation the MCM-48 support is prepared by a controlled extraction of the cationic gemini surfactant, in such a way that no thermal post-treatment step is required. Secondly, we present an approach of selective, partial hydrofobization of the silica walls, using dimethyldichlorosilane (DMDCS), rendering it essentially hydrophobic to withstand the water attack, but creating simultaneously sufficient active sites for a subsequent grafting of the surface. Finally, VOx surface species are grafted on the silylated MCM-48 surface, in such a way that leaching is almost completely suppressed. 

The preparation of pure silica MCM-48, using cationic gemini surfactants, followed by a controlled extraction of the surfactant results in materials that have a more narrow pore size distribution than the ones in which the surfactant is removed by calcination. Since no calcination is needed, there is no unit cell contraction and the extraction surfactant can be recrystallized and re-used. 

Ionic compounds can also gelate solvents, perhaps one of the nicest examples being that of dicationic gemini surfactants in which tartrate is used as the counterion and source of chirality [158], because it shows the very important role of chirality on the property of the salt. When either d- or L-tartrate dianions and dimers of cetyltrimethylammonium cations are combined, stable gels are formed in chlorinated solvents, but neither the mixture of enantiomers nor the meso tartrate form a gel. The structure of the gelator... 

Jennings KH et al (2002) Aggregation properties of a novel class of cationic gemini surfactants correlate with their efficiency as gene transfection agents. Langmuir 18 2426... 

There are many combinations of surfactants reported. For example, cationic CTA surfactant and cationic Gemini surfactant, CTA and long-chain pyridine quaternary ammonium surfactant,11] anionic and cationic surfactant,1126 CTA and amine (Q2H25NH2), neutral and cationic surfactant,11761 and neutral-neutral surfactants have been used to prepare silica with interesting mesostructures (e.g., Ia3d cubic) or morphologies (e.g., nanoparticles). 

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 ... 

While this manuscript was in preparation, the first example of twisting of the bilayers of cationic gemini surfactants by chiral counterions like tartrate, glucarate, malate, and gluconate was reported. ... 

The adsorption from aqueous solution of surfactants with two hydrophilic and two hydrophobic groups (gemini surfactants, Chapter 12) onto oppositely charged sites on solid particle surfaces—cationic geminis onto clay particles (Li, 2000), anionic geminis onto limestone particles (Rosen, 2001)—results in one hydrophilic group oriented toward the solid surface and the second oriented toward the aqueous phase. The solid particles are dispersed in both cases. 

A micellar electrokinetic capillary chromatographic (MECC) method to separate 17 dihydroergotoxines, aci-alkaloids, and oxidation products has been described [103]. The authors used novel cationic dimeric (Gemini) surfactants such as l,3-bis(dodecyl-W,N-dimethyl ammonium)-2-propanol and l,3-bis(te-tradecyl-N,N-dimethyl ammonium)-2-propanol for the separation in less than 8 min. 

The second of the above compounds is an example of a so-called gemini surfactant. Recently there has been considerable interest in these surfactants which are doubleheaded cationic compounds in which two alkyl dimethyl quaternary ammonium groups per molecule are linked by a hydrocarbon spacer chain. (These are denoted as n-m-n... 

Ronsin, G. Penin. C. Guedat, P. Kremer, A. Camilleri. P. Kirby. A.J. Novel spermine-based cationic gemini surfactants for gene delivery. Chem. Commun. 2001. 2234. 

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