Nonionic surfactants geminis

The most frequently used ionic SDAs are again CTAB/CTAC, OTAB/OTAC as well as hexadecylpyridinium bromide/chloride (CPB/CPC), whereby the syntheses are carried out under basic conditions, and most commonly surfactants of the Pluronic and Brij type 86 are used as nonionic SDAs under acidic conditions. In rare cases also Gemini surfactants or long alkyl chained ionic liquids were applied as SDAs, whereby an ethane-bridged PMO with a Fm-3m symmetry was successfully prepared for the first time.88... 

Compositions comprising at least one nonionic gemini surfactant - is useful, e.g., in personal care compositions, household cleaning products and industrial cleaners... 

Contain at least one nonionic gemini surfactant and are extremely effective emulsifiers and provide improved detergency... 

Figure 17.2 shows examples of gemini surfactants, which have been somewhat randomly taken from the literature. Compounds 1-3 are cationics differing in the type of spacer unit connecting the two ionic moieties. The spacer of Compound 1 is hydrophobic and flexible, that of Compound 2 is hydrophilic and flexible, while that of Compound 3 is hydrophobic and rigid. Compound 4 is a typical nonionic gemini and Compound 5 is an anionic one, based on the same backbone structure. Compounds 6 and 7, finally, are examples of heterogemini surfactants. 

M. J. L. Castro, J. Kovensky and A. F. Cirelli, New family of nonionic gemini surfactants. Deter-... 

Figure 11.3 Schematic representation of Gemini surfactant with the spacer group connecting (A) the two head groups (often the case for cationic surfactants), and (B) the alkyl chains at a location very close to the head group (case of nonionic and anionic Gemini surfactants).

Muzzalupo et al. (2007) studied the interactions of nonionic homopolymer poly(vinylpyrrolidone) (PVP) and different gemini surfactants at 25 C. They studied the interactions under a wide variety of experimental conditions by changing the amounts of polymer and surfactant. According to their reported data, the cationic gemini surfactants do not interact with nonionic PVP. 

The gemini-containing cationic [quaternary ammonium salts, called bis (Quats)], anionic (phosphate, sulfate, carboxylate), amphoteric and nonionic (polyether or sugar), polar groups have been a matter of numerous investigations [59]. Only few studies have been done on the physicochemical and biological properties of amino acid-based gemini surfactants [60-62]. 

The CMC of the nonionic gemini surfactants [K] where CeHi3 is substituted by C f 2m+ [51,75] are much lower than those of ionic gemini surfactants with the same alkyl chain carbon number m, just as for conventional surfactants. 

Additions of (3-cyclodextrin increased the CMC of bisquaternary ammonium surfactants [95]. Addition of (3-cyclodextrin to nonionic gemini surfactant [Q] where X = OH causes a gradual change in the size and form of the aggregates. Rod-shaped aggregates form upon increasing cyclodextrin content. More and more rods form whereas the micellar aggregates break up [96,97]. 

These are nonionic organic surfactants, cationic surfactants, amphoteric surfactants, perfluormated surfactants, and gemini surfactants (21). A wide variety of examples have been given. Some are listed in Table 4.11 and shown in Figure 4.6. 

Zana, R., Levy, H., Kwetkat, K. Mixed micellization of dimeric (Gemini) Surfactants and conventional surfactants. I. Mixtures of an anionic dimeric surfactant and of the nonionic surfactants C12E5 and C,2Ej. J. Colloid Interface Sci. 1998, 797(2), 370-376. 

Esumi, K., Miyazaki, M., Arai,T., Koide,Y. Mixed miceUar properties of a cationic Gemini surfactant and a nonionic surfactant. Colloids Surf. A 1998, 735(1-3), 117-122. 

We distinguish four types of surfactant. Anionic (e.g. SDS), cationic (e.g. CTAB), nonionic (e.g. alkylethylene glycols), and zwitterionic (e.g. phosphatidyl choline). Beside conventional surfactants, Gemini, bolafarm, oligomeric and polymeric surfactants become more and more important. 

---