- Characterization of Fluorescent Surfactant Aggregates by Fluorimetric and Viscosimetric Techniques
-
A combination of fluorimetric and viscosimetric methods was used to characterize N,N-dimethyl-N-2-(4-(t-butylphenoxy)ethoxy)ethyl-N-hexadecylammonium chloride (BDHC), a double-tailed surfactant with dissimilar tail groups. BDHC was observed to fluoresce at 315 nm when excited at 274 nm, a feature which could be utilized to determine its critical micelle concentration (CMC). A value of 3.98 × 10-5 M was obtained and was observed to be slightly temperature dependent with a Tmin of 25.35°C. Fluorescence quenching experiments using 4-nitroaniline as a quencher were performed in order to determine the aggregation number which was found to be 42.0. The hydrodynamic radius of 21.91 A was obtained using data from viscosimetric experiments. These data, together with the Tanford and Einstein-Stokes relationships, were used to determine the micellar structure (spherical) and the diffusion coefficient (D = 0.97 × 10-6cm2/s), respectively. The ΔG of micellization for BDHC was determined to be -34.9kJ/mol.
- Iwunze,Lambert,Silversmith
-
-
Read Online
- Role of Spacer Chain Length in Dimeric Micellar Organization. Small Angle Neutron Scattering and Fluorescence Studies
-
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
-
-
Read Online
- Cationic gemini lipids containing polyoxyethylene spacers as improved transfecting agents of plasmid DNA in cancer cells
-
Lipoplex nano-aggregates have been analyzed through biophysical characterization (electrostatics, structure, size and morphology), and biological studies (transfection efficiency and cell viability) in five cancer cell lines. Lipoplexes were prepared from pEGFP-C3 plasmid DNA (pDNA) and mixed liposomes, constituted by a zwitterionic lipid (DOPE) and a gemini cationic lipid (GCL) synthesized in this work, [bis(hexadecyl dimethyl ammonium) oxyethylene], referred to as (C16Am)2(C2O) n, (where n is the oxyethylene spacer length, n = 1, 2 or 3, between the ammonium heads). Cryo-TEM micrographs show nano-aggregates with two multilamellar structures, a cluster-type (at low-to-medium GCL composition) and a fingerprint-type that coexists with the cluster-type at medium GCL composition and appears alone at high GCL composition. SAXS diffractograms show that these lipoplexes present three lamellar structures, two of them coexisting at low and high GCL composition. The optimized transfection efficiency (TE) of pDNA was higher for lipoplexes containing GCLs with a longer (n = 3) or shorter (n = 1) polyoxyethylene spacer, at high GCL composition (α = 0.7) with low charge ratio (ρeff = 2). In the all cancer cell lines studied, the TE of the optimized formulations was much better than those of both lipofectamine 2000 and lipoplexes with GCLs of the bis(hexadecyl dimethyl ammonium) alkane series recently reported. Probably, (a) the coexistence of two lamellar structures at high GCL composition synergizes the TE of these lipid vectors, (b) the orientation of the polyoxyethylene region in (C16Am) 2(C2O)3/DOPE may occur in such a way that the spacing between two cationic heads becomes smaller than that in (C 16Am)2(C2O)2/DOPE which is poor in terms of TE, and (c) the synergistic interactions between serum proteins and (C16Am)2(C2O)n/DOPE-pDNA lipoplexes containing a polyoxyethylene spacer improve TE, especially at high GCL content. Lipoplexes studied here show very low levels of toxicity, which confirm them as improved vectors of pDNA in gene therapy.
- Barran-Berdon, Ana L.,Misra, Santosh K.,Datta, Sougata,Munoz-Ubeda, Monica,Kondaiah, Paturu,Junquera, Elena,Bhattacharya, Santanu,Aicart, Emilio
-
-
Read Online
- Ru-Catalyzed Selective Catalytic Methylation and Methylenation Reaction Employing Methanol as the C1 Source
-
Methanol can be employed as a green and sustainable methylating agent to form C-C and C-N bonds via borrowing hydrogen (BH) methodology. Herein we explored the activity of the acridine-derived SNS-Ru pincer for the activation of methanol to apply it as a C1 building block in different reactions. Our catalytic system shows great success toward the β-C(sp3)-methylation reaction of 2-phenylethanols to provide good to excellent yields of the methylated products. We investigated the mechanistic details, kinetic progress, and temperature-dependent product distribution, which revealed the slow and steady generation of in situ formed aldehyde, is the key factor to get the higher yield of the β-methylated product. To establish the environmental benefit of this reaction, green chemistry metrics are calculated. Furthermore, dimerization of 2-naphthol via methylene linkage and formation of N-methylation of amine are also described in this study, which offers a wide range of substrate scope with a good to excellent yield.
- Biswas, Nandita,Srimani, Dipankar
-
p. 10544 - 10554
(2021/07/31)
-
- End group type macromolecular quaternary ammonium salt and preparation method thereof
-
The invention discloses an end group type macromolecular quaternary ammonium salt and a preparation method thereof. Polyhydric alcohols and chlorinated carboxylic acid are dehydrated to produce a macromolecular skeleton in the presence of a catalyst and an appropriate solvent, and the prepared macromolecular skeleton is reacted with tertiary amine so as to obtain the end group type macromolecularquaternary ammonium salt. The macromolecular quaternary ammonium salt is novel in structure and low in toxicity, has strong bacteria inhibiting and resisting effects, and is capable of adjusting the structure according to needs so as to achieve corresponding physical properties. The macromolecular quaternary ammonium salt has wide application prospects in the fields of polymer emulsion, personal care, dry-film preservation, coatings, adhesives, household supplies and the like. The macromolecular quaternary ammonium salt disclosed by the invention is simple and controllable in preparation process, high in operability, mild in conditions, green, environmental-friendly and suitable for industrial production.
- -
-
Paragraph 0018
(2019/03/29)
-
- N-Methylation of amines and nitroarenes with methanol using heterogeneous platinum catalysts
-
We report herein the selective N-methylation of amines and nitroarenes with methanol under basic conditions using carbon-supported Pt nanoparticles (Pt/C) as a heterogeneous catalyst. This method is widely applicable to four types of N-methylation reactions: (1) N,N-dimethylation of aliphatic amines under N2, (2) N-monomethylation of aliphatic amines under 40 bar H2, (3) N-monomethylation of aromatic amines under N2, and (4) tandem synthesis of N-methyl anilines from nitroarenes and methanol under 2 bar H2. All these reactions under the same catalytic system showed high yields of the corresponding methylamines for a wide range of substrates, high turnover number (TON), and good catalyst reusability. Mechanistic studies suggested that the reaction proceeded via a borrowing hydrogen methodology. Kinetic results combined with density functional theory (DFT) calculations revealed that the high performance of Pt/C was ascribed to the moderate metal–hydrogen bond strength of Pt.
- Jamil, Md.A.R.,Touchy, Abeda S.,Rashed, Md. Nurnobi,Ting, Kah Wei,Siddiki, S.M.A. Hakim,Toyao, Takashi,Maeno, Zen,Shimizu, Ken-ichi
-
-
- Synthesis, surface activity and thermodynamic properties of cationic gemini surfactants with diester and rigid spacers
-
A group of cationic gemini surfactants with diester and rigid spacers, 12-Ph-12, 14-Ph-14, 16-Ph-16, were synthesized and confirmed by IR, 1H NMR and elemental analysis. The surface parameters of the synthesized gemini surfactants including: the critical micelle concentration (CMC), the surface tension value at CMC (γCMC), effectiveness (πCMC), efficiency (pC20), maximum surface excess (Γmax) and minimum surface area (Amin), were obtained from surface tension measurements. These gemini surfactants showed higher surface activity than the traditional monomeric surfactants. The thermodynamic parameters of micellization process from conductivity measurements showed that the micellization was a spontaneous and exothermic process in environment, and the micellization process becomes less favorable with the decrease of alkyl chain length and increase in temperature. The micropolarity was evaluated from steady fluorescence spectra, and the dye solubilization was investigated by using UV–visible spectroscopy. The results revealed that the micropolarity of surfactant micelles is very low and these gemini surfactants can really enhance the solubility of water insoluble dyes.
- Zhang, Ting,Cao, Xianfei,Wang, Xuchun,Song, Changchun
-
p. 505 - 510
(2017/02/05)
-
- Synthesis and properties of biodegradable cationic gemini surfactants with diester and flexible spacers
-
A series of cationic gemini surfactants with diester and flexible spacers, namely C12-PG-C12, C14-PG-C14 and C16-PG-C16, were synthesized, purified and characterized. The surface properties and aggregation behavior of the gemini surfactants were investigated by surface tension, electrical conductivity, fluorescence and Krafft point. These gemini surfactants possess higher surface activity than the traditional monomeric surfactants. The thermodynamic parameters exhibited that the micellization was a spontaneous and exothermic process in environment. The micellization process became less favorable with the decrease of alkyl chain length and the increase of temperature. Steady-state fluorescence measurements revealed that the micropolarity and aggregation number of micelles decreased with the increase of hydrocarbon chain length. The Krafft points were taken as ?0?°C, which indicated the synthesized gemini surfactants had good water solubility. The biodegradability of the gemini surfactants were evaluated in river water using Closed Bottle tested and showed their high biodegradation ratio in the open environment due to the diester bond inserting in the flexible spacer of surfactant molecules.
- Xu, Dongqing,Ni, Xiaoyue,Zhang, Congyu,Mao, Jie,Song, Changchun
-
p. 542 - 548
(2017/06/06)
-
- Alkylation of amines with alcohols catalyzed by palladium nanoparticles
-
Palladium nanoparticles (PdNPs) generated in situ from the complex [(dippe)PdMe2] were used as efficient catalyst for the alkylation of amines by aliphatic alcohols using neat conditions, under hydrogen atmosphere. On using short chain alcohols
- Reyes-Rios, Grisell,García, Juventino J.
-
p. 317 - 321
(2013/01/13)
-
- Vernonia oil: Conversion to a mixture of tertiary amines including N,N-Dimethyl-(12S,13R)-Epoxy-cis-9-Octadecenyl amine
-
Vernonia galamensis is a new potential industrial oilseed crop found in tropical Africa. It is the source of a naturally epoxidized oil called vernonia oil (VO) which is extracted from the seed of the plant. In this study VO was used as the starting material for the synthesis of a mixture of amines, with the major product amine being N,N-dimethyl-(12S,13R)-epoxy-cis-9-octadecenyl amine. VO was transesterified via a base catalyzed methanolysis using sodium methoxide to yield VO methyl esters (VOME). Aminolysis of the VOME with dimethylamine as reagent and solvent under reflux conditions afforded the tertiary amides, with N,N- dimethyl-(12S,13R)-epoxy-cis-9-octadecenyl amide as the major product. The mixture was then subjected to metal hydride reduction with lithium aluminum hydride in diethylether under reflux conditions to obtain the desired amine mixture including N,N-dimethyl-(12S,13R)-epoxy-cis-9-octadecenyl amine. Electron impact mass spectrometry was used to characterize the mixture of amines. Additionally, proton NMR, 13C NMR, and FTIR were used for characterization of N,N-dimethyl-(12S,13R)-epoxy-cis-9-octadecenyl amine. To further confirm the conversion of VO to the amines, the quaternary ammonium salts were synthesized and characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.
- Johnson, Nikki S.,Ayorinde, Folahan O.
-
experimental part
p. 1425 - 1430
(2011/11/11)
-
- Synthesis of multifunctional surfactants for elaboration of micellar model systems of enzymes
-
In order to provide a closer analogy between micelles and enzymes, the design of functionalized micellar systems have been undertaken. This paper presents the synthesis of surfactant cationic molecules which contains either a free or a protected aldehyde group. An ammonium quaternary surfactant with two functional groups, aldehyde dimethyl acetal and imidazole, has also been synthesized.
- Huang,Sirieix,de Viguerie,Riviere,Lattes
-
p. 250 - 255
(2007/10/03)
-
