- Synthesis and characterization of asymmetrical gemini surfactants
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The effect of variation in the length of surfactant hydrocarbon tail groups was tested in a series of dissymmetric gemini surfactants (N1-alkyl N1,N1,N3,N3-tetramethyl-N3-(6-pyren-6yl)-hexyl)propane-1,3-diammonium dibromide designated as CmC3CnBr, with m = hexyl pyrene, and n = 8, 12, 14, 16, and 18. The aggregation properties of these surfactants have been investigated by means of 1H NMR, fluorescence spectroscopy, surface tension and electrical conductivity measurements. The critical micelle concentration (CMC) was determined using surface tension and confirmed using the specific conductance method. Krafft temperatures and the degree of micelle ionization (α) were obtained from specific conductance measurements. With an increase of the dissymmetry (m/n) ratio, the CMC decreased linearly and an increase in the Krafft temperatures was observed for all of the gemini surfactants. α values for the dissymmetric GS were higher than those of the m-3-m counterparts, which may be attributed to enhanced micelle-micelle interactions that arise from increased hydrophobicity of the hydrocarbon chains. The introduction of the bulky pyrenyl tail group resulted in much lower CMC values compared to their symmetrical counterparts affecting the packing of these surfactants at the air/water interface, which resulted in high-ordered structures (lamellar and inverted micelles). This in turn affected the thermodynamic parameters of the micellization.
- Muslim, Aula Al,Ayyash, Dana,Gujral, Sarbjeet Singh,Mekhail, George M.,Rao, Praveen P. N.,Wettig, Shawn D.
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- A general strategy for the rational design of size-selective mesoporous catalysts
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A series of functionalized mesoporous silicas with cagelike pore topology has been synthesized and screened for size-selective catalytic transformations. The aluminum-catalyzed Meerwein-Ponndorf-Verley (MPV) reduction of differently sized aromatic aldehydes (benzaldehyde and 1-pyrenecarbox-aldehyde) has been investigated as a test reaction. The catalysts were synthesized in a two-step grafting sequence comprising pore-size engineering of mesoporous silicas (SBA-1, SBA-2, SBA-16) with longchain alkyl dimethylaminosilanes and surface organoaluminum chemistry with triethylaluminum [{Al-(CH2CH 3)3)2]. Size-selective reaction behavior was found for small pore SBA-1 materials, and the selectivity could be efficiently tuned by selecting a silylating reagent of appropriate size. The results are compared with the catalytic performance of a large-pore periodic mesoporous organosilica PMO-[SBA-1] and the nonporous high-surface-area silicas Aerosil 300/380.
- Zapilko, Clemens,Liang, Yucang,Nerdal, Willy,Anwander, Reiner
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- Micellization behavior of cationic gemini surfactants in aqueous-ethylene glycol solution
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The micellization behavior of gemini surfactants i.e. alkanediyl-α, ω-bis(cetyldimethylammonium bromide) (C16-s-C 16,2Br- where s = 3, 4, 10) in 10% (v/v) ethylene glycol solution was investigated by surface tension and conductometric measurements at 300 K. The critical micelle concentration, degree of micellar ionization, surface excess concentration, minimum surface area per molecule of surfactant, surface pressure at the CMC and Gibbs energy of adsorption of the dimeric surfactants have also been determined in the presence of different salts (NaCl, NaBr and NaI). The critical micelle concentration and degree of micellar ionization values decrease significantly in the presence of sodium halides and follows the sequence NaCl NaBr NaI. The free energy, enthalpy and entropy of micellization of dimeric surfactants in 10% (v/v) ethylene glycol solution were determined using the temperature dependence of the critical micelle concentration. The standard free energy of micellization was found to be negative in all the cases. AOCS 2011.
- Tikariha, Deepti,Kumar, Birendra,Singh, Namrata,Ghosh, Kallol K.,Quagliotto, Pierluigi
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- Synthesis of carboxylic group functionalized mesoporous silicas (CFMSs) with various structures
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Carboxylic group functionalized mesoporous silicas (CFMSs) were successfully synthesized by using cationic surfactants as templates and carboxyethylsilanetriol sodium salt (CES) as a co-structure directing agent (CSDA). Well ordered two-dimensional (2D) p6mm, cubic Fm3m, intergrowth of Fm3m and P63/mmc, and cubic Fd3m with uniform carboxyl group distributions have been synthesized with increasing charge density of carboxylate of CES on the surface of the mesopore, which will provide new families of mesoporous materials with different functionalities and structures. The Royal Society of Chemistry 2007.
- Han, Lu,Sakamoto, Yasuhiro,Terasaki, Osamu,Li, Yongsheng,Che, Shunai
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- Determination of the Aggregation Number of Pyrene-Labeled Gemini Surfactant Micelles by Pyrene Fluorescence Quenching Measurements
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A cationic gemini surfactant referred to as Py-3-12 and composed of two alkylated diammonium bromide head groups, a propyl spacer, and dodecyl and 1-pyrenehexyl hydrophobic tails was synthesized. Its critical micellar concentration (CMC) was determined to equal 0.15 (±0.02) mM by surface tension and time-resolved fluorescence measurements. The state of the pyrene molecules, whether they were incorporated inside the Py-3-12 micelles or unassociated in the aqueous solution, was determined by applying the global model-free analysis (MFA) to the fluorescence decays acquired with Py-3-12 aqueous solutions. The unassociated Py-3-12 surfactants emitted as pyrene monomers and showed a long fluorescence lifetime. The excited pyrenyl groups located inside Py-3-12 micelles formed an excimer by a rapid encounter with a ground-state pyrene with an average rate constant equal to 0.69 (±0.06) ns-1. After having the photophysical properties of Py-3-12 in aqueous solution characterized, the number (Nagg) of surfactants per micelle was determined by conducting quenching experiments with dinitrotoluene (DNT). Although DNT is fairly hydrophobic, it was found to partition itself between the Py-3-12 micelles and the aqueous phase. Fluorescence quenching experiments performed on the pyrene monomer and excimer generated by the Py-3-12 aqueous solutions yielded the concentration ([Q]b) of DNT bound to the Py-3-12 micelles and the average number ?n?d of DNT quenching an excimer by diffusive encounters. A combination of steady-state and time-resolved fluorescence quenching experiments on the excimer yielded the number (?n?s) of DNT molecules that were bound to the micelles and quenched the excimer in a static manner. A plot of the sum ?n?d + ?n?s as a function of [Q]b yielded an Nagg value of 14.0 (±0.2) Py-3-12 units per micelle. This study represents the first example in the literature where Nagg is determined for a micelle, where each surfactant molecule is labeled with pyrene.
- Ba-Salem, Abdullah O.,Duhamel, Jean
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- Conformational analysis of (Phenylenedimethylene)bis(n-octylammonium)dibromides in aqueous solution. Conformational change upon micellization
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Three gemini surfactants, in which two quaternary ammonium species (CH3(CH2)7N+(CH3) 2) are linked at the polar headgroups by ο-, m-, or p-phenylenedimethylene spacers, have been synthesized. The critical micelle concentration (cmc) of these surfactants in aqueous solutions was determind by electrical conductivity. Selective-decoupling 13C NMR and 1H NMR spectra were measured at various concentrations below and above the cmc. The selective-decoupling 13C NMR results revealed that the specific rotational isomers about the CH2-aromatic carbon single bonds for the gemini surfactant having a m-phenylenedimethylene spacer are preferentially stabilized upon micellization, while for the gemini surfactant having an ο-phenylenedimethylene spacer, the presence of only the conformation in which the aromatic ring is sandwiched between two n-octyl chains was confirmed. Furthermore, it was found that variation in the stacking pattern of the aromatic rings after micellization of the surfactants is reflected in the 1H spectral features of the aromatic protons. Comparison is made with the conformations of bis(quaternaryammonium) bromides with flexible spacer chains ((CH2)x) and of the corresponding n-alkylammonium bromide monomeric surfactants.
- Hattori, Norikatsu,Yoshino, Akihiro,Okabayashi, Hirofumi,O'Connor, Charmian J.
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- Influence of Amine-Based Cationic Gemini Surfactants on Catalytic Activity of α-Chymotrypsin
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The α-chymotrypsin activity was tested in aqueous media with the presence of novel cationic amine–based gemini surfactant, with different spacer chain lengths and head group size, and also compared with the cationic cetyltrimethylammonium bromide (CTAB) a
- Verma, Santosh Kumar,Ghritlahre, Bhupendra Kumar,Ghosh, Kallol K,Verma, Rameshwari,Verma, Shekhar,Zhao, Xiujian
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p. 779 - 784
(2016/11/02)
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- Retarding action of poly(amidoamine) dendrimers and cationic gemini surfactants in acrylic dyeing
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Two cationic gemini surfactants and two generations of poly(amidoamine) (PAMAM) dendrimers (G = -0.5 and G = 0.5) were studied as retarders in acrylic dyeing with a cationic dye. Effects of retarder concentrations, dyeing time, and temperature were investigated by means of UV-Vis spectrophotometry. The results indicated that the dye adsorption decreased in the presence of the species and more uniform dyeing was achieved. The PAMAM dendrimers had lower retarding action than the cationic gemini surfactants which was attributed to their non-permanent and lower cationic charge density. Kinetics of the dyeing systems were also evaluated by four different empirical models. The modified Cegarra-Puente model fitted the dyeing kinetic data somewhat better than the other empirical kinetic models. Moreover, the activation energy of the dyeing systems was calculated and reported.
- Sadeghi-Kiakhani, Mousa,Tehrani-Bagha, Ali Reza
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p. 323 - 330
(2015/11/24)
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- Gemini surfactants foam formation ability and foam stability depends on spacer length
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A series of cationic gemini surfactants containing different spacer length were synthesized and analyzed structurally. It was shown that the surface tension (σ) and critical micelle concentration (CMC), which had a maximum for the n-C4H8 spacer depended on the spacer length. The foaming ability and foam stability are high for the gemini surfactants with short spacers (C2H4 to n-C4H8), while longer spacers lead to a distinct decrease of these foam parameters. Foaming properties are discussed in terms of configuration and conformation of a surfactant molecule and in relation to micellization state kinetic.
- Kuliszewska, Edyta,Brecker, Lothar
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p. 951 - 957
(2014/11/08)
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- Designing pH-sensitive gemini nanoparticles for non-viral gene delivery into keratinocytes
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This study aimed to develop a more effective non-viral gene delivery system for keratinocyte transfection. To this end, gemini nanoparticles were formulated from plasmid DNA, the lipid DOPE (dioleoylphosphatidylethanolamine) and surfactants, where the sur
- Donkuru, McDonald,Wettig, Shawn D.,Verrall, Ronald E.,Badea, Ildiko,Foldvari, Marianna
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experimental part
p. 6232 - 6244
(2012/06/30)
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- Synthesis, molecular structure, spectral properties and antifungal activity of polymethylene-α,ω-bis(n,n-dimethyl-n-dodecyloammonium bromides)
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Hexamethylene-1,6-bis-(N,N-dimethyl-N-dodecylammonium bromide) (1), pentamethylene-1,5-bis(N,N-dimethyl-N-dodecylammonium bromide) (2), tetramethylene-1,4-bis(N,N-dimethyl-N-dodecylammonium bromide) (3), trimethylene-1,3-bis(N,N-dimethyl-N-dodecylammonium bromide) (4) and ethylene-1,2-bis(N,N-dimethyl-N-dodecylammonium bromide) (5) have been obtained and characterized by FTIR and NMR spectroscopy. DFT calculations have also been carried out. The optimized bond lengths, bond angles and torsion angles calculated by Hartree-Fock/3-21G(d,p) approach have been presented. MIC values for A. niger, P. chrysogenum, C. albicans have been determined and the relationship between MIC and spacer length has been discussed.
- Brycki, Bogumil,Kowalczyk, Iwona,Kozirog, Anna
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experimental part
p. 319 - 335
(2011/04/18)
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- Long chain dicationic phase transfer catalysts in the condensation reactions of aromatic aldehydes in water under ultrasonic effect
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Long chain dicationic ammonium salts were used successfully as phase transfer catalyst in the condensation reactions of aromatic aldehydes in water under ultrasonic irradiation for the first time. The quaternary salt having longer distance between the cation centers was more effective than the mono- and dicationic ones having short chain.
- Esen, Ilker,Yolacan, Cigdem,Aydogan, Feray
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experimental part
p. 2289 - 2292
(2010/11/05)
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- Salt effects on the aqueous two-phase system of Gemini(12-3-12, 2Br -)/SDS/PEG
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The effect of added salts (NaCl, KCl and NaBr) on the aqueous two-phase system (ATPS) formed in mixtures of Gemini(12-3-12, 2Br-)/sodium dodecyl sulfate/polyethylene glycol has been investigated. Phase diagrams of the aqueous systems containing Gemini(12-3-12, 2Br-), sodium dodecyl sulfate (SDS), polyethylene glycol(PEG) and a salt have been determined experimentally at 313.15 K. The results indicate that the addition of salts not only induces the appearance of ATPS-A (in which anionic surfactant is in excess), shortens the phase separation time, enlarges the regions of ATPS-C (in which cationic surfactant is in excess), and decreases the minimum concentration required for forming an ATPS, but also alters the matching between anionic and cationic surfactants. Extractive experiments also showed that these salts notably enhance the extraction ability of ATPS; the Gemini-rich phase exhibits prominent cohesive action with xylenol orange, regardless of whether or not it is the upper phase or the lower phase.
- Al-Hakimi, Abdulaziz Mohammed,Shang, Yazhuo,Liu, Honglai,Hu, Ying
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scheme or table
p. 1307 - 1313
(2010/05/18)
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- Polycations. 19. The synthesis of symmetrical dicationic lipids with internal dimethylazonia functionalities separated by a spacer unit and pendant chains
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Herein is reported the preparation of several series of symmetrical polyammonium salts that serve as cationic lipids or precursors thereof, and are structurally based on several series of parent diamines where dimethylazonia functionalities are present, separated by a central structural unit, and pendant terminal chains. The resultant materials are of significant interest for a variety of purposes, such as serving as antihydrophobic species and as transfectins, the details of which are provided in separate reports. Attempts to effect selective alkylation to provide the corresponding unsymmetrical cationic lipids were without success, always leading to relatively useless mixtures of products.
- Engel, Robert,Rizzo, JaimeLee Iolani,Montenegro, Diego,Leb, Jay,Coleman, Delroy,Hong, Carolyn,Jeanty, Herby,Thomas, Marie
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experimental part
p. 105 - 108
(2010/04/05)
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- Specific ion pairing and interfacial hydration as controlling factors in gemini micelle morphology. Chemical trapping studies
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Results from chemical trapping experiments in micellar solutions containing 1.5-5 mM aqueous solutions of three didodecyl dicationic dibromide gemini surfactants with different methylene spacer lengths (12-n-12 2Br where n = 2-4 CH2 groups) gav
- Geng, Yan,Romsted, Laurence S.,Menger, Fred
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p. 492 - 501
(2007/10/03)
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- Synthesis and solution properties of gemini surfactants containing oleyl chains
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Gemini surfactants 18:1-s-18:1, where s = 2, 3, and 6 methylene groups and 18:1 refers to oleyl carbon chains, have been synthesized, characterized and a number of micelle solution properties measured by using electrical conductance, fluorescence probe em
- Li, Xingfu,Wettig, Shawn D.,Wang, Chuanzhong,Foldvari, Marianna,Verrall, Ronald E.
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p. 3172 - 3178
(2008/02/03)
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- First evaluation of the thermodynamic properties for spheres to elongated micelles transition of some propanediyl-α,ω-bis(dimethylalkylammonium bromide) surfactants in aqueous solution
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The apparent and partial molar enthalpies, apparent molar volumes, and adiabatic compressibilities at 298 K of the aqueous solutions of the cationic gemini surfactants propanediyl-α,ω-bis(octyldimethylammonium bromide) (8-3-8) and propanediyl-α,ω-bis(dodecyldimethylammonium bromide) (12-3-12) have been measured as a function of concentration. The trends of the partial molar enthalpies versus concentration are the first well documented thermodynamic evidence of sphere to rod transition in the micellar phase, involving a detectable quantity of heat, and allow the determination of the change in enthalpy associated with this transition. The changes in enthalpies upon micellization and for the sphere to elongated micelles transition, ΔHs-r have been obtained from the experimental data by using a pseudo-phase transition approach: -1.5 kJ mol-1 for 8-3-8 and -3.9 kJ mol-1 for 12-3-12. No evidence of the above transition is found in the trends of volumetric properties versus m. The apparent adiabatic molar compressibilities for the compounds under investigation are also reported here for the first time: a negative group contribution for the methylene group is evaluated, when the surfactants are present in solution as a single molecule, reflecting its solvation structure. In the micellar phase, the -CH2- group contribution becomes positive. A value of 1.17 × 10-3 cm3 bar-1 mol-1 for the change in adiabatic molar compressibility upon micellization is obtained. The lower values of the methylene group contributions to the volumetric properties for the monomers support the hypothesis of partial association of the chains before the cmc.
- Fisicaro, Emilia,Compari, Carlotta,Duce, Elenia,Contestabili, Cristina,Viscardi, Guido,Quagliotto, Pieriuigi
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p. 1744 - 1749
(2007/10/03)
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- Role of Spacer Chain Length in Dimeric Micellar Organization. Small Angle Neutron Scattering and Fluorescence Studies
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Micelles of different dimeric amphiphiles Br(1-), n-C16H33NMe2(1+)-(CH2)m-N(1+)Me2-n-C16H33, Br(1-) (where m = 3, 4, 5, 6, 8, 10, and 12) adopt different morphologies and internal packing arrangements in aqueous media depending on their spacer chain length (m).Detailed measurements of small angle neutron scattering (SANS) cross sections from different bis-cationic, dimeric surfactant micelles in aqueous media (D2O) are reported.The data have been analyzed using the Hayter and Penfold model for macro ion solution to compute the interparticle structure factor S(Q) taking into account the screened Coulomb interactions between the dimeric micelles.The SANS analysis clearly indicated that the extent of aggregate growth and the variations of shapes of the dimeric micelles depend primarily on the spacer chain length.With spacer chain length, m/=4, the propensity of micellar growth was particularly pronounced.The effects of the variation of the concentration of dimeric surfactants with m = 5 and 10 on the SANS spectra and the effects of the temperature variation for the micellar system with m = 10 were also examined.The critical micelle concentrations (cmc) and their microenvironmental feature, namely, the microviscosities that the dimeric micellar aggregates offer to a solubilized, extrinsic fluorescence probe, 1,6-diphenyl-1,3,5-hexatriene, were also determined.The changes of cmcs and microviscosities as a function of spacer chain length have been explained in terms of conformational variations and progressive looping of the spacer in micellar core upon increasing m values.
- De, Soma,Aswal, Vinod K.,Goyal, Prem S.,Bhattacharya, Santanu
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p. 11664 - 11671
(2007/10/03)
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- Vesicle Formation from Dimeric Surfactants through Ion-pairing. Adjustment for Polar Headgroup Separation leads to Control over Vesicular Thermotropic Properties
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Eight new vesicle-forming dimeric surfactants are synthesized: the polar headgroup separation in such dimeric amphiphiles strongly influences their vesicular thermotropic phase-transition behaviour.
- Bhattacharya, Santanu,De, Soma
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p. 651 - 652
(2007/10/02)
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