Dimeric surfactant

R. Zana, In K. Holmberg (Ed.), Dimeric Surfactants, Novel Surfactants, Surfactant Science Series, Vol. 74, Marcel Dekker, New York, USA, 1998, p. 241. 

Beside the conventional surfactants with one polar head group and one nonpolar tail, dimeric and oligomeric surfactants have attracted considerable interest in academia and industry [521], Dimeric surfactants, also called Gemini surfactants, are made up of two amphiphilic moieties connected closely to the head group by a spacer group (Fig. 12.1). In bolaform surfactants the connection is in the middle of the alkyl chain or close to the end, so that they can be considered as two polar head groups connected by a long hydrophobic chain. 

An MMA dimer obtained by CCT was hydrolyzed and then re-esterified with 1,10-decanediol. The resulting diester was allowed to react with chlorosulfonic acid to produce the methacrylate dimer surfactant, 2,4-bis(sodium 10-sulfate decanoxycarbonyl)-4-methyl-pent-l-ene. At the beginning of a polymerization, the molecule acts as a surfactant and subsequent incorporation of the dimer in the polymerization yields a surfactant-functionalized polymer. Thus, additional surfactants are not required. 

A theoretical explanation of experimental results, obtained for modified (non rigid spacer) gemini surfactants, was presented by Andelman and Diamant.47 They noted that the aggregate morphology for dimeric surfactants is related mainly to the influence of the spacer on the specific area X. The geometrical parameter, that determines aggregate shape, is the packing parameter denoted by the formula 48,49... 

D. Danino, Y. Talmon, and R. Zana, Alkanediyl-Alpha, Omega-Bis(Dimethylalkylammo-nium Bromide) Surfactants (Dimeric Surfactants). 5. Aggregation and Microstructure in Aqueous-Solutions. Langmuir, 1995, 11, 1448-1456. 

Another interesting work published recently in the literature addresses the issue of solute localization dependence on phase selectivity. The influence of the length of flexible hydrophobic (67) and hydrophilic (68) spacers of anionic dimeric surfactants was studied by MEKC in contrast to SDS. A set of 41 solutes was categorized into nonhydrogen bond, hydrogen bond acceptors, and hydrogen bond donors. Although the authors chose to perform an LSER... 

Generally, both types of dimeric surfactants still show well-defined, clear CMCs, though in selected cases the CMC is less obvious to standard methods, in particular to conductometric methods [415, 424, 425]. The values of CMCs determined by different methods agree well, and the counter-ion effects are the usual ones [426,427]. But, strikingly, CMC values of both bola-surfactants and of gemini-surfactants are lowered by one order of magnitude or more in... 

Zana R 1996 Gemini (dimeric) surfactants Curr. Opin. Colloid Interface Sci. 1 566-71... 

Bernheim-Groswasser. A. Zana, R. Talmon, Y. Micro- 30. structures in aqueous solutions of mixed dimeric surfactants Vesicle transformation into networks of thread-like micelles. J. Phys. Chem.. B 2000. 104. 12192-12201. and references therein. 

Danino, D. Talmon. Y. Zana, R. Vesicle-to-micelle transformation in systems containing dimeric surfactants. J. Colloid Interface Sci. 1997, 185. 84-93. 

Worm-like micelles are formed in solutions of both ionic and nonionic surfactants. For aqueous solutions of ionic surfactants, inorganic or organic salt or cosurfactants are necessary except for special system like dimeric surfactants. On the other hand, nonionic surfactants can form worm-like micelles in water without anyadditionalcomponents. Surfactants ofpolyoxyethylene type C H2 +i(OC2H4) OH... 

The term gemini surfactant was coined by Menger inl991. A gemini surfactant may be viewed as a surfactant dimer, i.e. two amphiphilic molecules connected by a spacer. Figure 17.1 shows the general structure. Gemini surfactants are also referred to as twin surfactants , dimeric surfactants or bis-surfactants . 

Karaborni, S., K. Esselink, and R. Os. Zana. 1994. Simulating the self-assembly of Gemini (dimeric) surfactants. Science 266(5183) 254. 

Zana, R. 1996. Gemini (dimeric) surfactants. Current Opinion in Colloid and Interface Science 1(5) 556-571. 

Organogels can be prepared by cationic gemini (dimeric) surfactants as ion pairs with dianions. Hue et al. prepared ion pairs 2a-d consisting of dimers of cetyltrimethylammonium ions with various counteranions (Fig. 4.2b(i)) [11]. Ion pairs 2a,b formed gels in CH2CI2, CHCI3, and CHCI2CHCI2 ( 10 mM). In these... 

Gemini (dimeric) surfactants are made up of two surfactants like moieties connected at the level of the head groups or on the alkyl... 

Although the electrostatic force plays the main role in the interactions of oppositely charged surfactants and polymers, hydrophobicities of polymer and surfactant also play a role. Zana and Benrraou (2000) studied the interaction of two polyelectrolytes PSl and PS4 (copolymers of disodium maleate and methyl or butyl vinyl ether, respectively), and quaternary ammonium bromide surfactants (3-dodecyldimethyl(alkyl)ammonium bromides and two dimeric surfactants of the polymethylene-a,fi)-bis(dodecyldimethylammonium bromide) type). They used the surfactant-binding isotherms method and spectrofluorometry using pyrene as a fluorescent probe to detect the onset of binding. Their results showed that surfactant binding to the polymer is more pronounced when the polymer is more hydrophilic for a given surfactant. 

Xu Y, Feng J, Liu H, Hu Y, Jiang J (2007) Molecular dynamics simulation of polyelectrolyte with oppositely charged monomeric and dimeric surfactants. Mol Simul 33(3) 261-268. doi 10.1080/08927020601158679... 

MJL Castro, J Kovensky, A Fernandez Cirelli. Dimeric Surfactants from... 

Finally, it has been shown in the author s laboratory that lipases are rather useful catalysts for the synthesis of dimeric gemini surfactants. Our interest in these compounds was due to several recent reports dealing with the preparation and properties of geminis, which are effectively two molecules of a conventional monomeric surfactant linked through a flexible spacer. It appeared that dimeric surfactants display most unusual patterns... 

There is another important difference between the two types of surfactant. The phenylalkylsulfonates (Al) represent simple dimeric surfactants, whereas the A2 compounds are examples of a new class of surfactants, the gemini surfactants. Both types of surfactants and consequently both types of inisurfs differ considerably in their properties. The gemini inisurfs are able to stabilize a much larger surface area per molecule than conventional and simple dimeric surfactants. Consequently, the gemini inisurfs should lead in an emulsion polymerization to smaller particle sizes than the other inisurfs. 

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