Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

Synthesis and properties of novel alkyl sulfate gemini surfactants

Four anionic gemini surfactants of the sulfate type C₁₂C_nC₁₂, where n is the spacer chain length (n = 3, 4, 6, and 10) were synthesized. The structures of these surfactants were confirmed by FT‐IR, ¹H NMR, ESI mass spectra (ESI‐MS), and elemental analysis. The surface‐active properties of these compounds were investigated by means of surface tension, electrical conductivity, and fluorescence measurements. Premicellar aggregations were found for the four gemini surfactants, as revealed by the conductivity measurement. The formation of premicellar aggregates may account for the discrepancy between the critical micelle concentration (cmc) obtained by the surface tension and conductivity measurement. The cmc values of these gemini surfactants were much lower than that of sodium dodecylsulfate (SDS) and decreased monotonously with the increase of spacer chain length from 3 to 10. The effect of spacer chain length on the performance properties like foaming, emulsion stability, and lime soap dispersing ability were also studied and discussed. Practical applications : Alkyl sulfate surfactants are one of the most widely used surfactants. The new alkyl sulfate gemini surfactants synthesized in our study are more surface‐active than sodium dodecylsulfate. These gemini surfactants possess low critical micelle concentrations, high emulsion stability, and excellent lime soap dispersing ability. They have potential applications in the fields of cosmetics, detergents, etc.     

Preparation,Characterization and Properties of Novel Cationic Gemini Surfactants with Rigid Amido Spacer Groups

A series of novel cationic gemini surfactants with rigid amido groups inserted as the spacers, named C ₁₂ ‐PPDA‐C ₁₂ , C ₁₄ ‐PPDA‐C ₁₄ and C ₁₆ ‐PPDA‐C ₁₆ , were synthesized by a two‐step reaction with dimethyl terephthalate, N,N‐dimethyl propylene diamine and alkyl bromide as raw materials. The chemical structures of the prepared compounds were confirmed by IR, ¹H and ¹³C NMR and element analysis. Surface activity properties of the synthesized compounds were investigated by surface tension, electrical conductivity and fluorescence. Increasing the number of carbon atoms in the hydrophobic alkyl chain, decreased the critical micelle concentration (CMC), surface tension at the CMC and the minimum surface area. Other relevant properties including foaming ability and emulsion stability were investigated. The results indicated that the synthesized gemini surfactants possess good surface properties, emulsifying properties and steady foam properties.     

Antibacterial Activities of Five Cationic Gemini Surfactants with Ethylene Glycol Bisacetyl Spacers

A series of cationic gemini surfactants containing two dimethylalkylammonium chains linked by ethylene glycol bisacetyl spacers were synthesized [G_m‐AnA‐m, G = gemini surfactant, m = 12 (–C₁₂H₂₅), 14 (–C₁₄H₂₉), or 16 (–C₁₆H₃₃), A = acetyl, and n = 2, 3, or 4 is the number of ethylene glycol units in the spacers]. Because of the inductive effect of the oxygen atom in the spacer, acylation can take place using chloroacetyl chloride instead of bromoacetyl bromide which helps to limit the use of environmentally harmful reagents. Critical micelle concentrations were determined using conductivity measurements. The antibacterial activities of the surfactants against Gram‐positive bacterium Staphylococcus aureus and Gram‐negative bacterium Escherichia coli were evaluated from the minimum inhibitory concentration (MIC), minimum bacterial concentration, a time–kill study, and the inhibitory zone. Increasing the length of the spacer did not result in an obvious change of antibacterial activity. However, increasing the length of the alkyl chain apparently increased the antibacterial activity against S. aureus but decreased the antibacterial activity against E. coli. The G_{12‐A2A‐12} surfactant had the lowest CMC of 1.26 mmol L^?1 and exhibited the best antibacterial activity with a MIC of 32 μg mL^?1 toward S. aureus and 64 μg mL^?1 toward E. coli in the presence of 10⁵ CFU of bacteria. This work indicated that these cationic gemini surfactants have potential applications as antibacterial agents and emulsifiers.     

Study of the Interaction Between Methyl Orange and Mono and Bis-Quaternary Ammonium Surfactants

The solubilization and interaction of an azo-dye (methyl orange) with dodecyl trimethyl ammonium bromide and cationic gemini surfactants in the series of alkanediyl α,ω-bis[(dimethyl alkyl ammonium)bromide)] referred to as (m-s-m), m = 10, 12, 14 and s = 2, 3, 4 were investigated by means of UV–Vis spectroscopy. Aggregation with the anionic dye was reflected by a hypsochromic shift with a decrease in the intensity of the absorption band. The results also show a bathochromic shift followed by a sharp increase in the intensity of the maximum absorption band λ_max after the critical micellar concentration (CMC). This indicates that the dye solubility increased with increasing surfactant concentration. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration far below the CMC of the individual surfactant. The effects of the chain length as well as the spacer length of gemini surfactants on the critical aggregation concentration and CMC were also examined. Moreover, the partition coefficients between the bulk water and surfactant micelles K _S and K _X as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were determined using the pseudo-phase model. The effect of the hydrophobic chain length and spacer of gemini surfactants on the distribution parameters is also reported.     

Synthesis of Succinic Gemini Surfactants and the Effect of Stereochemistry on Their Monolayer Behaviors

In this work, succinic gemini surfactants, dl‐ and meso‐2,3‐bis(alkyl)succinic acids (alkyl: C₆H₁₃–C₁₃H₂₇), were successfully synthesized by oxidative coupling of enolates of fatty acid tert‐butyl esters with copper(II) bromide followed by treatment with CF₃COOH. Focusing on the influence of stereochemistry (dl‐ and meso‐) of succinic geminis, their monolayer behaviors at the air–water interface were explored using surface pressure–area (Π–A) isotherms, the compression modulus of monolayers (ε_s), and Brewster angle microscope (BAM) analysis. meso‐2,3‐Bis(undecyl)succinic acid showed a unique isotherm where the surface pressure drastically decreased at A = ~0.56 nm² (Π = 21.9 mN m^?1) regardless of compression rates and subphase temperatures, while dl‐isomer showed the common isotherm of gas → liquid‐expanded → liquid‐condensed phase transitions. BAM analysis on meso‐2,3‐bis(undecyl)succinic acid films at the air–water interface showed that small islands of aggregates appear just after the maximum pressure (A = ~0.56 nm²), and on further compression needle‐shaped assemblies appear that can grow in size. It was reasonably concluded that hydrophobic interactions can operate more effectively in meso‐isomers than in dl‐isomers, and that meso‐molecules can “jump up” to cause a transition from monolayer to bilayer. This is the first finding of the “jumping‐up” phenomenon of gemini surfactants having meso‐stereochemistry.     

Synthesis and Surface Activity of Bisphosphate Gemini Surfactants

Anionic bisphosphodiester gemini surfactants with two different spacer moieties and varying alkyl chain lengths were synthesized and investigated for their surface active properties. The equilibrium and dynamic surface tension studies were carried out using the Wilhelmy plate technique and maximum bubble pressure method respectively. It was found that these gemini surfactants possess lower critical micellar concentration values, and reduce the surface tension to a greater extent in comparison with the conventional analogues. The efficiency of the synthesized gemini surfactants was also evaluated. The results of surface activities obtained were correlated with the structures of gemini surfactants. The dynamic surface tension measurements showed that the geminis with long chains adsorb very slowly at the air/water interface within the time span of measurements. These gemini surfactants showed low foamability.     

Gemini surfactant controlled preparation of well-ordered lamellar mesoporous molybdenum oxide

A series of well-ordered lamellar mesoporous molybdenum oxides were prepared using gemini surfactant [C _n H_2n+1N⁺(CH₃)₂–(CH₂)₂–N⁺(CH₃)₂C _n H_2n+1] · 2Br⁻(denoted as C _n-2-n , n = 12, 14 and 16) as the structure-directing agent and ammonium heptamolybdate tetrahydrate (NH₄)₆Mo₇O₂₄ · 4H₂O as the precursor. The obtained samples were characterized by X-ray powder diffraction, thermal analysis, transmission electron microscopy and nitrogen adsorption–desorption. Results showed that contrary to complete structure collapse after removing tetradecyltrimethylammonium bromide (TTAB) from molybdenum oxide/TTAB composite, the lamellar mesostructure was retained after removal of C _n-2-n from corresponding composite. The effects of alkyl chain length and concentration of gemini surfactants on the structure of the mesoporous molybdenum oxide were also investigated. The specific surface area of extracted sample was as high as 116 m² g⁻¹. The maintenance of the lamellar mesostruture was due to the strong self-assembly ability of gemini surfactants and the strong electrical interaction between gemini surfactants and molybdenum oxide.     

Synthesis and Properties of Dissymmetric Gemini Surfactants

A series of novel dissymmetric gemini surfactants, [C _m H_2m+1COOC₂H₄(CH₃)₂N(CH₂)₃N(CH₃)₂C₂H₄OOCC _n H_2n+1]Br₂ was synthesized and symbolized as m-s–n. The Krafft temperatures and surface tension curves of the dissymmetric gemini surfactants were measured using an electrical conductivity method and a drop volume method. The low Krafft temperatures indicate very good solubility of these esterquat gemini surfactants. With the increasing numbers of carbon atoms in the hydrophobic alkyl chain, the critical micelle concentration (CMC) and the minimum surface area (A _min) decrease, and the efficiency of surface tension reduction (pc₂₀) increases. With the same numbers of carbon atoms in the hydrophobic alkyl chain, the dissymmetric gemini surfactant has a lower CMC and a smaller A _min than the corresponding symmetric gemini surfactant due to the enhanced hydrophobic interactions.     

Synthesis, Antimicrobial Activity and Micellization of Gemini Anionic Surfactants in a Pure State as Well as Mixed With a Conventional Nonionic Surfactant

New gemini anionic surfactants were prepared from sodium salts of monoalkyl sulfosuccinate esters of ethylene glycol having variably long tails (C₁₂, C₁₆, C₁₈) and dichloroethane. The chemical structures of the prepared surfactants were confirmed using different spectroscopic techniques. The surfaces tension values of the synthesized surfactants were measured at 25 °C individually or mixing at different molar fractions with ethoxylated alkylphenol. In all cases, mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured. The micellization processes of the individual and mixed surfactants were investigated. The effect of different alkyl chains of gemini anionic surfactants on properties of binary systems and molar ratio in the mixed aggregates were deduced. The critical micelle concentration of mixed surfactants shifted to lower values compared to those of the single surfactants. Effectiveness values increased with decreases in the mole fraction of gemini anionic surfactants. The negative values of interaction parameter (β) increased with increases in the chain length of anionic surfactants. The activity coefficient (f ₁, f ₂) and total minimum surface area of mixed solution were calculated. Also, the gemini anionic surfactants prepared have moderate antimicrobial activity towards bacteria and not active towards fungi.     

Synthesis and Evaluation of Novel Amido-Amine Cationic Gemini Surfactants Containing Flexible and Rigid Spacers

New amido‐amine‐based cationic gemini surfactants with flexible and rigid spacers and different hydrophobic tails were synthesized and characterized. These gemini surfactants were prepared by a modified procedure through amidation of long chain carboxylic acids using 3‐(dimethylamino)‐1‐propylamine followed by treatment with halohydrocarbons. The effect of the trans and cis conformation of the spacer double bond was investigated by means of critical micelle concentration, surface tension reduction, and thermal stability. The short‐term thermal stability of the gemini surfactants was assessed using thermogravimetric analysis (TGA) and the long‐term thermal stability was examined by a unique approach based on structure characterization techniques including NMR (¹H and ¹³C) and FTIR analysis. TGA results demonstrated excellent short‐term thermal stability since no structure degradation was observed up to 200 °C. Structural characterization revealed impressive long‐term thermal stability of the gemini surfactants with no structure decomposition after exposing them to 90 °C for 10 days. The critical micelle concentration of gemini surfactants was found to be in the range of 0.77 × 10^?4–3.61 × 10^?4 mol L^?1 and corresponding surface tension (γ_CMC) ranged from 30.34 to 38.12 mN m^?1. The surfactant with the trans conformation of spacer double bond showed better surface properties compared to the surfactant with the cis conformation of spacer double bond. Similarly, increasing surfactant tail length and spacer length resulted in decreasing CMC values. Moreover, bromide counterion showed improved surface properties compared to chloride counterion.     

Effects of Molecular Structure and Temperature on Micellization of Cationic Ammonium Gemini Surfactants in Aqueous Solution

Micellization of four cationic quaternary ammonium gemini surfactants, having a diethyl ether or hexyl spacer with the alkyl chain lengths of 12 and 16 carbon atoms, was studied using isothermal titration microcalorimetry (ITC) and electrical conductivity measurements in the temperature range from 298.15 to 313.15 K. In this temperature range, where surfactants are normally applied, the temperature almost does not influence the critical micelle concentration (CMC) and the degree of micelle ionization (α) values of the gemini surfactants, and the replacement of a hexyl spacer by a diethyl ether spacer leads to a slight decrease in the CMC and α values. However, as the alkyl chain length increases from 12 to 16 carbon atoms, the CMC values significantly decrease from 0.99–1.19 mM to 0.020–0.057 mM. In particular, the enthalpy of micellization (ΔH_mic ) and the associated thermodynamic parameters show obvious changes with varying temperature and molecular structure. ΔH_mic becomes much more exothermic at higher temperature or for the surfactants with a more hydrophilic spacer. Moreover, the heat capacity change of micellization (ΔC _{P, mic} ) is less exothermic for the surfactants with a more hydrophilic spacer or a longer alkyl chain. The enthalpy–entropy compensation data show that the surfactants with longer alkyl chains have a more stable micellar structure.     

Synthesis and physico‐chemical properties of novel dialkyl diphosphate gemini surfactants based on octadecanol

A series of dialkyl diphosphate gemini surfactants has been synthesized using C₁₈ as hydrophobic chains and phosphate as head groups. Three flexible spacers have been used. In the present study, an attempt has also been made to synthesize mono octadecyl phosphate (MOP) at 35°C, which was used as an intermediate in the synthesis of geminis. This long chain of MOP has been effectively converted to gemini surfactants and subsequently converted to their disodium salts. The effect of reaction variables like temperature, duration, molar ratios of reactants, catalyst and spacer on the yield of dialkyl diphosphate gemini surfactant has also been reported. The MOP, gemini surfactants and disodium salt of gemini surfactants were characterized using FT‐IR and ¹H‐NMR. Surface active and physico‐chemical properties of synthesized gemini surfactants and their monomer were also determined. The results revealed that the yield of dialkyl diphosphate gemini surfactants ranged from 80 to 90%. Among all synthesized dialkyl diphosphate gemini surfactants D, S‐1,6‐GSOD had maximum anionic content, i.e. 80.7%, showed highest foaming ability and superior dispersing ability, whereas D, S‐1,8‐GSOD showed low cmc values, i.e. 0.00012 mM/L; minimum surface tension and interfacial tension, i.e. 39.1 and 36.3 mN/m, respectively.     

Surface-Active Properties and Antimicrobial Study of Conventional Cationic and Synthesized Symmetrical Gemini Surfactants

Symmetrical gemini surfactants of cationic series α,ω-alkanediyl bis (dimethyl ammonium bromide) commonly referred as “m–s–m” have been synthesized. Spectral analysis was performed to confirm compound structures and purity. Conductivity and surface tension measurements provide better understanding of the micellization process. Their self-assembly behavior in aqueous solution is also discussed in detail. The antimicrobial efficacy was measured by bacterial and fungal growth inhibition expressed as minimal inhibitory concentration values against five strains of a representative group of microorganisms viz. Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia, Salmonella paratyphi B and Aspergillus niger. All of the synthesized surfactants showed antimicrobial activity against them, but at different levels depending on their structures. The surfactants possessing longer alkyl chains (more hydrophobic environment) demonstrated better antimicrobial functionality. The antimicrobial potency was found to be dependent on the representative target microorganism (Gram-positive bacteria > fungi > Gram-negative bacteria), as well as on the ionic nature of the surfactant (cationic), alkyl chain length (m = 12, 16) and spacer length (s = 2, 4, 6) of the synthesized compounds. Gemini surfactants such as 12-2-12 and 12-4-12 were found to be weakly active whereas 16-2-16 and 16-4-16 compounds proved to be the most potent antimicrobial surface-active agents among the synthesized gemini homologues.     

Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6-Diaminohexane and Alkyl Bromides

Two new classes of gemini cationic surfactants—hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: C_nC₆C_n[iPr-OH] and C_nC₆C_n[iPr-OH]₂; alkyl: C_nH_{2n + 1} with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N′-di-(isopropylol)-1,6-diaminohexane and N,N,N′,N′-tetra-(isopropylol)-1,6-diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C₁₂H₂₅ chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.     

Synthesis and evaluation of new imidazolium‐based aromatic ether functionalized cationic mono and gemini surfactants

Synthesis of a novel series of imidazolium‐based surfactants, [(ROArCH₂MIm)Br] with aromatic ether functionalized hydrophobic tail of varying chain lengths and also their gemini counterparts were conducted in the present work. Synthesis involves initial conversion of 4‐hydroxy benzoic acid to its methyl ester followed by its O‐alkylation with long chain fatty alcohols, which was subsequently reduced and brominated to get 4‐alkyloxy benzyl bromide. For the synthesis of monocationic surfactant, 4‐alkyloxy benzyl bromide is quaternized with N‐methylimidazole. Gemini surfactants are synthesized by initial coupling of imidazole to 4‐alkyloxy benzyl bromide followed by its quaternization with dibromoalkane. The surface properties of all the synthesized surfactants were determined using surface tensiometry. Within the same homologous series, expected decrease in critical micelle concentration (cmc) with the increase in hydrophobicity was observed for shorter chain homologs. However, the deviation in cmc value from regularity was observed when the number of carbon atoms in the hydrophobic chain exceeded a certain number. The cmc values of the geminis were found to be remarkably low compared to their monomeric counterparts.     

Aggregation and Thermodynamic Properties of Some Cationic Gemini Surfactants

In this study, the gemini surfactants of the alkanediyl-α-ω-bis(alkyl dimethyl ammonium) dibromide type, on the one hand, with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred to as “m-2-m” (m = 10, 12 and 16) and, on the other hand, with n-C₁₆ alkyl groups and different spacers containing s carbon atoms, referred to as “16-s-16” (s = 2, 6, 10 and Ar (8)) have been synthesized, purified and characterized. The critical micelle concentration (CMC), micelle ionization degree (α) and Gibbs free energy of micellization (∆G _mic) of these surfactants and the monomeric cationic surfactants DTAB and CTAB have been determined by means of electric conductivity measurements. In addition, the temperature dependence of the CMC was determined for the 10-2-10 gemini surfactant. The CMCs of the gemini surfactants are found to be much lower than those of the corresponding monomeric surfactants and the effect of the hydrophobic alkyl chain length is more important than that of the spacer. The CMC of 16-s-16 passes through a maximum of (or around) s = 6 and then decreases for s = 10. The presence of a maximum CMC is explained by the contribution of a change of conformation of the surfactant with increasing spacer chain length. The changes of α with s and m are found qualitatively similar to those found for CMC values. The values of ∆G _mic are more negative for the dimers than for the monomers and also change with an increasing spacer carbon number, as CMC values do. The thermodynamic parameters of micellization indicate that the micellization of 10-2-10 is enthalpy driven.     

Synthesis and Properties of Alkoxyethyl β‐d‐Xylopyranoside

In order to improve the water solubility of sugar‐based surfactants, alkyl β‐d‐ xylopyranosides, novel sugar‐based surfactants, 1,2‐trans alkoxyethyl β‐d‐ xylopyranosides, with alkyl chain length n = 6–12 were stereoselectively prepared by the trichloroacetimidate method. Their properties including hydrophilic–lipophilic balance (HLB) number, water solubility, surface tension, emulsification, foamability, thermotropic liquid crystal, and hygroscopicity were investigated. The results indicated that their HLB number decreased with increase of alkyl chain, the water solubility improved since the hydrophilic oxyethene (─OCH₂CH₂─) fragment was introduced. The dissolution process was entropy driven at 25–45 °C for alkyl chain length n = 6–10. Octyloxyethyl β‐d‐ xylopyranoside had the best foaming ability. Nonyloxyethyl β‐d‐ xylopyranoside had the best foam stability and the emulsifying ability was better in toluene/water system than in rapeseed oil/water system. The surface tension of in aqueous solution dropped to 27.8 mN m^?1 at the critical micelle concentration, and it also showed the most distinct thermotropic liquid phases with cross pattern texture upon heating and the fan schlieren texture on cooling. Hexyloxyethyl β‐d‐ xylopyranoside possessed the strongest hygroscopicity. Based on the effective improvement of water solubility, the prepared alkoxyethyl β‐d‐ xylopyranosides showed excellent surface activity and are expected to develop their practical application as a class of novel sugar‐based surfactants.     

Reverse Micellar Encapsulation of d‐ and l‐Enantiomers of Some Aromatic α‐Amino Acids and Nucleobases by Glucose‐Derived Non‐ionic Gemini Surfactants in Neat n‐Hexane

Novel carbohydrate‐based non‐ionic gemini surfactants consisting of two sugar head groups, two hydrophobic tails having chain lengths of C12, C14, and C16 and a flexible –(CH₂)₆– spacer were synthesized and investigated for their reverse micellar encapsulation properties. The head groups of the geminis comprise glucose entities (with reducing function blocked in a cyclic acetal group) connected through C‐6 to tertiary amines. These surfactants were explored for reverse micellar encapsulation of d ‐ and l ‐enantiomers of aromatic α‐amino acids viz. histidine (His), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp) in neat n‐hexane. Similar studies were carried out for encapsulation of nucleobases viz. adenine (Ade), guanine (Gua), thymine (Thy), cytosine (Cyt) and Uracil (Ura). Reverse micellar studies revealed that aromatic α‐amino acids were encapsulated in the sequence His>Tyr>Phe>Trp. In most cases, a difference in the degree of encapsulation of d ‐ and l ‐enantiomers of aromatic amino acids in reverse micellar phases of gemini amphiphiles in neat n‐hexane, was revealed. For Tyr, l ‐enantiomer was better encapsulated than its antipode, i.e., d ‐enantiomer but for Trp, d ‐enantiomer was better encapsulated then l ‐enantiomer. In the case of nucleobases, Ura was found selectively encapsulated by reverse micelles formed by these new amphiphiles.     

Glucamine-based gemini surfactants I: Gemini surfactants from long-chain <Emphasis Type="Italic">N</Emphasis>-alkyl glucamines and α,ω-diepoxides

N-Alkyl glucamines can be reacted with α,ω-diepoxides to yield gemini (dimeric) surfactants similarly to the reaction of glucamine with terminal epoxides. Under the conditions chosen for this work, epoxides were quantitatively converted in the presence of an equimolar amount of amine to gemini surfactants. Reactions could be carried out under mild conditions (70°C) in methanol, and products were obtained quantitatively by removing the solvent. The combination of N-octyl glucamine, N-decyl glucamine, or N-dodecyl glucamine with diepoxides of α,ω-diolefins having chain lengths of C₈, C₉, C₁₀, or C₁₄ resulted in gemini surfactants differing in spacer length and length of hydrophobic alkyl chains. Surface-active properties were studied by measuring surface tension and evaluating foaming properties. Tensiometric studies showed the reduction of surface tension down to 29–33 mN/m and critical micelle concentrations often in the range of 3–150 mg/L. Comparison of a selected gemini surfactant [1,8-bis(N-dodecyl glucamino-2,7-octane diol] with its corresponding “single surfactant” demonstrated the enhancement of surface-active properties afforded by the gemini structure.