Gemini Surfactants

Journal of Surfactants and Detergents (Impact Factor: 1.69). 09/1998; 1(4):547-554. DOI: 10.1007/s11743-998-0057-8


The literature, including patents, describing the emerging area of gemini surfactants is reviewed. The differences in structure/property
relationships between gemini and comparable conventional surfactants are described and discussed in terms of their predicted
performance properties. Supportive performance data are enumerated.

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    • "The latter ones are composed by two conventional single-tail amphiphilic moieties chemically connected by spacer groups, usually polymethylene or short poly(oxyethylene) chains [10] [21]. Recently, many studies concerning the practical use of gemini molecules appeared in the literature [22] [23] [24] [25], showing that the first speculative interests were followed by practical applications, due to their unusual properties, such as the lower critical micellar concentration (CMC) values, the better adsorption behavior at both the air/water and the solid/water interfaces with respect to their single monomers, and the tendency to form micelles of different shapes and dimensions (i.e., spherical, rodlike, threadlike, vesicles), even at low concentration, when compared with similar nongemini surfactants. In this work, the concentration of surfactants in the ageing solution is varied in order to produce different conditions of selfaggregation between the surfactant molecules themselves. "
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    ABSTRACT: Mesoporous TiO2 nanocrystals have been synthetized by a classical sol-gel route integrated by an hydrothermal growth step using monomeric (dodecylpyridinium chloride, DPC) or dimeric gemini-like (GS3) surfactants as template directing agents. Adsorption isotherms at the solid/liquid interface of the two surfactants have been obtained on aqueous dispersion of titania; the nature of the oxide/adsorbate interactions and the molecules orientation/coarea are discussed. The effects produced by the presence of the two surfactants on the different morphological (surface area, porosity, and shape) and structural (phase composition and aggregate size) features of the final TiO2 samples, calcined at 600∘C, are discussed.
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    • "They have the ability to aggregate at an extraordinary low concentration (10 25 M). According to Rosen and Tracy (1998), it seems likely that in gemini surfactants the inter-or intra-molecular hydrophobic interactions are greatly favoured probably due to the spacer chain nature. "
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    ABSTRACT: Amino acid-based surfactants constitute a class of bio-based surfactants with excellent adsorption and aggregation properties, low potential toxicity and broad biological activity. In this review, the enzymatic synthesis, physicochemical and biological properties as well as the potential uses of these compounds are described.
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    ABSTRACT: The use of compressed CO2 processing to alter the pore size, structure and timescale of silica condensation in surfactant templated silica thin films and powders is investigated by systematically varying the template structure and CO2 processing conditions. Tailoring the mesoporous materials increases its potential applications, as demonstrated in catalysis, drug delivery, chromatographic and electrode applications. This work demonstrates for the first time the applicability of fluorinated surfactants as templates for the synthesis of mesoporous silica thin films by dip coating. Well-ordered films with 2D hexagonal close-packed pore structure are synthesized in an acid-catalyzed medium using three cationic fluorinated templates of varied tail length and branching (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and (CF3)2CFC5F9C2H4NC5H5Cl). CO2 processing of the fluorinated templated silica results in a significant and controlled increase in pore diameter relative to the unprocessed films. The pore expansion is significantly greater compared to the negligible expansion observed in hydrocarbon (C16H23NC5H5Br) templated silica. The greater swelling of the fluorinated templates is attributed to the favorable penetration of CO2 in the CO2-philic fluorinated tail and the relative solvation of each template is interpreted from their interfacial behavior at the CO2-water interface. The CO2 based pore expansion observed in fluorinated surfactant templated films is extended successfully to base-catalyzed silica powders templated with a fluorinated surfactant (C6F13C2H4NC5H5Cl). Pore expansion in silica powders is significantly less than in acid catalyzed films and demonstrates the effects of pH on surfactant selfassembly in CO2 and increased silica condensation at basic conditions, which inhibits pore expansion. Finally, the use of fluorescence probe molecules is demonstrated for in-situ monitoring of the of CO2 processing of surfactant templated silica films to provide time dependent data on the local environment and dynamics of CO2 penetration. CO2 uptake occurs in surfactant tails even for hydrocarbon templates (C16H23N(CH3)3Br and C16H23NC5H5Br), which display negligible CO2 based swelling of the resulting pores. The timescale of silica condensation increases significantly in the presence of CO2 suggesting opportunities for structure alteration through application of external forces, such as magnetic fields and change in substrate chemistry and system humidity
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