首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Sulfobetaine-type surfactants containing a hydroxy group were synthesized by the reaction of long chain monoalkyl dimethyl tertiary amine with 3-chloro-2-hydroxypropanesulfonic acid sodium salt. The structures were characterized by 1H NMR and ESI-MS. Their critical micelle concentrations (CMC) in aqueous solution were determined by the plate method in the temperature rang from 298.15 to 328.15 K. The thermodynamic parameters of micellization ( $\Delta G_{\text{mic}}^{\theta}$ , $\Delta H_{\text{mic}}^{\theta}$ and $\Delta S_{\text{mic}}^{\theta}$ ) and surface adsorption ( $\Delta G_{\text{ad}}^{\theta}$ , $\Delta H_{\text{ad}}^{\theta}$ and $\Delta S_{\text{ad}}^{\theta}$ ) were calculated from CMC data. The results showed that the micellization and surface adsorption of these surfactants in aqueous solution was a spontaneous and entropy-driven process. The micellization and surface adsorption became easier when the alkyl chain length increased from 12 carbon atoms to 14. The enthalpy–entropy compensation of micellization and adsorption was investigated. The compensation temperature were found to be (311 ± 2) K for both micellization and adsorption. The $\Delta H_{\text{mic}}^{*}$ and $\Delta H_{\text{ad}}^{*}$ decreased, but the $\Delta S_{\text{mic}}^{*}$ and $\Delta S_{\text{ad}}^{*}$ increased with increasing the hydrophobic chain length from 12 to 14.  相似文献   

2.
The micellization behavior of bile salts—sodium cholate and sodium deoxycholate was studied in aqueous methanol, ethanol and ethylene glycol mixtures (10–20 % v/v) over a temperature range (300–320 K) by surface tension and conductivity methods. Critical micelle concentration, extent of counter ion binding (α), interfacial property (A min, ζmax, π-CMC, $ \Updelta G_{\text{ad}}^{ \circ } $ ) and thermodynamic parameters ( $ \Updelta G_{\text{m}}^{ \circ } $ , $ \Updelta H_{\text{m}}^{ \circ } $ , $ \Updelta S_{\text{m}}^{ \circ } $ ) for the micellization process are reported and discussed.  相似文献   

3.
Metal oxide nanoparticles are the subject of current interest because of their unusual optical, electronic, and magnetic properties. In this work, cobalt zinc ferrite ( $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ ) nanoparticles have been synthesized successfully through redox chemical reaction in aqueous solution. The synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles have been used for the preparation of homogenous polyvinyl acetate-based nanocomposite ( $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} /{\text{PVAc}} $ ) via in situ emulsion polymerization method. Structural, morphological and magnetic properties of the products were determined and characterized in detail by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD patterns of the $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ confirmed that the formed nanoparticles are single crystalline. According to TEM micrographs, the synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles had nano-needle morphology with an average particle size of 20 nm. The calculated coefficient of variation (CV) of nanoparticles diameters obtained by TEM micrographs was 16.77. The $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles were dispersed almost uniformly in the polymer matrix as was proved by SEM technique. The magnetic parameters of the samples, such as saturation magnetization (M s) and coercivity (H c) were measured, as well. Magnetization measurements indicated that the saturation magnetization of synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} /{\text{PVAc}} $ nanocomposites was markedly less than that of $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ magnetic nanoparticles. However, the nanocompoites exhibited super-paramagnetic behavior at room temperature under an applied magnetic field.  相似文献   

4.
A surface tension study was performed on mixed amphiphilic drug-nonionic surfactant systems. The drugs used were adiphenine hydrochloride and nortriptyline hydrochloride whereas surfactants were ethoxylated sorbitan esters and polyethylene oxide?Cpolypropylene oxide?Cpolyethylene oxide triblocks. The critical micelle concentration (CMC) and CMCid (CMC at ideal mixing condition) values suggest nonideal and attractive interactions among the components. The micellar mole fraction $ (X_{ 1}^{\text{m}} ) $ values calculated using Rubingh??s model indicate predominance of the nonionic surfactant in micelle formation. The mole fraction of surfactant in mixed monolayer $ (X_{1}^{\sigma } ) $ values are greater than $ X_{ 1}^{\text{m}} $ values, indicating a greater contribution of surfactant in monolayer formation. Thermodynamic parameters, viz. Gibbs energy of micellization $ (\Updelta G_{\text{m}}^{\text{o}} ) $ , Gibbs energy of adsorption $ (\Updelta G_{\text{ad}}^{\text{o}} ) $ , and excess free energy of mixed micelles $ (\Updelta G_{\text{ex}}^{\text{m}} ) $ and monolayers $ (\Updelta G_{\text{ex}}^{\sigma } ) $ were also evaluated. All these values suggest stable mixed micelle and mixed monolayer formation.  相似文献   

5.
The specific retention volumes, $ V_{\text{g}}^{0} $ , for adsorption of 21 solute probes on the solid surface of cellulose acetate butyrate (CAB)–poly(caprolactone) diol (PCLD) blend determined in the temperature range by inverse gas chromatography were used to evaluate Hansen solubility parameters (HSP). The effect of plasticizer, PCLD, on the HSP of CAB was investigated. The three components of HSP namely dispersive $ \delta_{2}^{\text{d}} $ , polar $ \delta_{2}^{\text{p}} $ , and hydrogen bonding $ \delta_{2}^{\text{h}} $ of the blend surface were compared with the CAB surface. The $ \delta_{2}^{\text{h}} $ of CAB was increased due to the addition of PCLD, while the change in the dispersive and polar components was found to be insignificant. The three HSP were decreasing linearly with increase of temperature for the blend as well as for pure CAB. The variation of HSP with weight fraction of CAB shown that the $ \delta_{2}^{\text{p}} $ was positively deviating from linearity whereas $ \delta_{2}^{\text{d}} $ and $ \delta_{2}^{\text{h}} $ were negatively deviating from linearity.  相似文献   

6.
In this study, different cationic surfactants were prepared by esterification with bromoacetic acid of different fatty alcohols, i.e., dodecyl, tetradecyl and hexadecyl species. The products were then reacted with diphenyl amine, and the resulting tertiary amines were quaternized with benzyl chloride to produce a series of quaternary ammonium salts. The metallocationic surfactants were prepared by complexing the cationic surfactants with nickel and copper chlorides. Surface tension of these surfactants were investigated at different temperatures. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γ max), minimum surface area (A min), efficiency (PC20) and effectiveness (π CMC) were studied. The thermodynamic parameters such as the free energy of micellization ( $\Updelta G_{\text{mic}}^{^\circ }$ ) and adsorption ( $\Updelta G_{\text{ads}}^{^\circ }$ ), enthalpy ( $\Updelta H_{\text{m}}^{^\circ }$ ), ( $\Updelta H_{\text{ads}}^{^\circ }$ ) and entropy ( $\Updelta S_{\text{m}}^{^\circ }$ ), ( $\Updelta S_{\text{ads}}^{^\circ }$ ) were calculated. FTIR spectra and 1H-NMR spectra were obtained to confirm the compound structures and purity. In addition, the antimicrobial activities were determined via the inhibition zone diameter of the prepared compounds, which were measured against six strains of a representative group of microorganisms. The results indicate that these metallocationic surfactants exhibit good surface properties and good biological activity on a broad spectrum of microorganisms.  相似文献   

7.
Methyl-4-[bis(4-bromophenyl)amino]benzoate cation radical salts having non-nucleophilic anions such as $ {\text{SbF}}^{ - }_{6} $ , $ {\text{PF}}^{ - }_{6} $ and $ {\text{AsF}}^{ - }_{6} $ were newly prepared and found to be very active initiators for the polymerization of cyclohexene oxide at room temperature, in dichloromethane without any external stimulation. The effects of counter ion structure, salt and monomer concentration on the polymerization yield and molecular weight, and the mechanism of initiation are presented.  相似文献   

8.
The thermodynamics of micellization of the sulfobetaine (SB) amphoteric surfactants, that is N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate and N-alkyl-N,N-dimethyl-3-ammonio-1-butanesulfonate (the carbon atom number of the alkyl chain is 12, 14 and 16 respectively) in aqueous solution, have been studied by surface tension measurements with the temperature range from 298.15 to 318.15?K. The critical micelle concentrations (CMC) of SB n-3 and SB n-4 surfactants were determined from the drop-volume methods at different temperatures. The obtained results indicated that the values of critical micelle concentration strongly depended on the surfactants species and temperatures. Thermodynamic parameters ( $ \Updelta G_{\text{mic}}^{ \circ } $ , $ \Updelta H_{\text{mic}}^{ \circ } $ and $ \Updelta S_{\text{mic}}^{ \circ } $ ) of the micelle formation were determined. The micellization was found to be enthalpy-driven at lower temperatures, while this process was entropy-driven at higher temperatures. The enthalpy?Centropy compensation were also investigated. The compensation temperature T c and $ \Updelta H_{\text{mic}}^{*} $ decreased, while $ \Updelta S_{\text{mic}}^{*} $ increased with the increase in the hydrophobic chain length.  相似文献   

9.
Structural characterization, the mechanism of catalytic activity generation and the nature of active sites of a NiSO4/γ-Al2O3 catalyst for isobutene oligomerization were studied by temperature programmed reduction (TPR), X-ray diffraction (XRD), diffuse reflectance infrared fourier transformed (DRIFTS) and X-ray photoelectron spectroscopy (XPS) techniques. The TPR measurements together with the XRD data indicated that calcination of the catalyst at 500 °C did not form either nickel oxide or nickel aluminate. The presence of only one type of surface nickel species formed by the incorporation of nickel ions into the surface vacant sites of γ-alumina lattice was indicated by XPS with Ar+ ions sputtering and TPR measurements. XPS analysis of the calcined catalyst suggested that the oxidation state of nickel ions in the calcined catalyst was (+2) and after calcination the nickel ions were coordinated to relatively more basic ligands. The surface acid centers of the catalyst were found to be only Lewis type. SO4 2? ions were found to be present as a chelating bidentate ligand and enhanced the acidity of metal ( $ {\text{Al}}^{3 + } $ and/or $ {\text{Ni}}^{2 + } $ ) Lewis acid centers. The results suggested that the combined effects of the presence of the bidentate SO4 2? ligand and dehydroxylation generate coordinatively unsaturated $ {\text{Ni}}^{2 + } $ that interact with isobutene during the oligomerization reaction. The formation of lower-valent nickel ions ( $ {\text{Ni}}^{x + } ,x\; \le\; 1 $ ) was demonstrated by in situ DRIFTS using CO as a probe molecule and by XPS measurements. Formation of a binuclear bridging carbonyl complex, $ [{\text{Ni}}({\text{CO}})^{ + } ]_{2} $ suggested that some lower-valent nickel species were formed via in situ reduction by isobutene. Analysis of Ni 2p photolines indicated the appearance of a new lower-valent nickel species ( $ {\text{Ni}}^{x + } ,x \;\le\; 1 $ ) during the course of isobutene oligomerization. Hence it is plausible that lower-valent nickel species might act as the active center for the oligomerization reaction, while the SO4 2? ions enhance the acidity of the Lewis acid sites on the surface and assist in the adsorption of reactant molecules on the surface.  相似文献   

10.
The formation dynamics of calcium barium sulphoaluminate mineral with the composition of 2.75CaO·1.25BaO·3Al2O3·SO3 (C2.75B1.25A3 $\overline{\text{S}}$ S ¯ ) was studied. The results suggest that, under the preparative conditions, the formation of C2.75B1.25A3 $\overline{\text{S}}$ S ¯ mineral is controlled by a diffusion mechanism from 1,100 to 1,380 °C; and, the formation dynamics fits nicely with D 4 = 1 ? 2α/3 ? (1 ? α)2/3 = Kt. From 1,100 to 1,300 °C, the apparent activation energy is 227.45 kJ mol?1. From 1,300 to 1,380 °C, the apparent activation energy decreases to 175.94 kJ mol?1, making the formation of C2.75B1.25A3 $\overline{\text{S}}$ S ¯ mineral faster and easier.  相似文献   

11.
A series of novel iminium surfactants were prepared through quaternization of different prepared fatty Schiff bases with benzyl chloride. The chemical structures were confirmed using FTIR, 1H-NMR and mass spectroscopy. The surface properties and biological activity of these surfactants were investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γmax) and minimum surface area (A min), Efficiency (PC20) and Effectiveness (πCMC) as well as the free energy of micellization ( $ \Updelta G_{\text{mic}}^{\text{o}} $ ) and adsorption ( $ \Updelta G_{\text{ads}}^{\text{o}} $ ) were calculated. It was found that the prepared compounds have good surface and biological activity.  相似文献   

12.
A ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane supported on a macroporous $\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ tube was prepared by sol–gel processing and used in the partial hydrogenation of acetylene and 1,3-butadiene. The average pore diameter of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was 3.6 nm. The gases were separated by Knudsen diffusion. The activity and selectivity of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was compared to that of ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ catalysts used in a conventional packed bed reactor. The highest selectivity to the partially hydrogenated products occurred when the reactant was premixed with H2 and was passed through the membrane wall.  相似文献   

13.
This work represents an idea of forming nanoporous structures on surface of a LPD (liquid phase deposition)-derived GeO2 ceramic film by thermal reduction of GeO2 under hydrogen atmosphere. SEM, XRD and Raman analyses show that well-defined nanopores with size in range of 10–100 nm have been formed on surface of GeO2 film by annealing at 600 °C for 5–10 min. The pore formation process is furthered by structural defects which serve as active sites for the thermal reduction reaction. Fast phase transformation from hexagonal GeO2 to tetragonal GeO2 has occurred within the first 5 min of annealing. Green-yellow (2.32 eV) and violet (2.9 eV) photoluminescences originating from $ {\text{O}} {-} \mathop {\text{Ge}}\limits^{ \bullet \bullet } {-} {\text{O}} $ and ≡Ge–Ge≡ defects are observed in the film samples. The photoluminescence peak intensity decreases with increase of annealing time due to diminution of O/Ge ratio. The film annealed for 5 min exhibits a maximum green-yellow to violet PL peak ratio, which is related to generation of some new $ {\text{O}} {-} \mathop {\text{Ge}}\limits^{ \bullet \bullet } {-} {\text{O}} $ defects at the phase interface.  相似文献   

14.
The catalytic activity toward hydrogen production through the dry reforming of methane was determined for Ru supported on lanthanum oxide. The catalyst remained stable for more than 80 h in the 823–903 K temperature range and reactant partial pressure ratio ( $ {\text{P}}_{{{\text{CO}}{}_{2}}} /{\text{P}}_{{{\text{CH}}{}_{4}}} $ ) equal to unity. However, a significant deactivation was observed during the kinetic measurements when the catalyst was exposed to $ {\text{P}}_{{{\text{CO}}{}_{2}}} /{\text{P}}_{{{\text{CH}}{}_{ 4}}} > 1 $ at 823 K. In order to establish why the catalyst deactivated, the Ru reactivity in reductive and CO2 rich atmospheres was studied by in situ LRS and XPS spectroscopies. The partial re-oxidation of metallic Ru could be one of the factors that produce the catalyst deactivation. To perform the kinetic measurements, the temperature range and the partial pressure ratios were selected within the window where the Ru catalyst was stable. The kinetic data and supporting spectroscopic evidence is consistent with a mechanism in which the metal and the oxide play key roles in decomposing the paraffin and activating the CO2, respectively.  相似文献   

15.
Various micelle parameters viz., critical micelle concentration (CMC), counter-ion binding (β), aggregation number (N), hydrodynamic radius (R h), micelle zeta potential (ζ) and energetic parameters, free energy of micellization ( $ \Updelta G_{\text{m}}^{0} $ ), enthalpy of micellization ( $ \Updelta H_{\text{m}}^{0} $ ) and entropy of micelle formation ( $ \Updelta S_{\text{m}}^{0} $ ) were determined for sodium dodecylsulfate, and dodecyltrimethylammonium bromide in the presence of NaCl for the former and NaBr for the latter. Conductometry and calorimetry methods were used for the measurements of CMC and energetic parameters. The fluorimetric (static quenching) method was employed to determine N and dynamic light scattering to estimate R h and ζ. The conductometrically determined β was verified from the CMC values by calorimetry using the Corrin–Harkins equation. The results found for the two surfactants of identical tails but different head groups have been presented and discussed. A detailed report on the salt effect using salts containing counter-ions the same as those in the surfactant is found only limitedly in the literature.  相似文献   

16.
In CH3CN–H20 medium the porphyrin Fe(IV)=O and porphyrin-C6F5IO adduct, and tBu $\dot{\hbox{O}}$ /tBuO $\dot{\hbox{O}}$ radicals have been spectroscopically identified. The involvement of multiple reactive intermediates in C6F5IO oxidizing system has also been demonstrated.  相似文献   

17.
Kinetic analysis of the Li|Li+ interphase in an electrolyte based on N-metyl-N-propylpyrrolidinium bis(trifluoromethanesulfon)imide ionic liquid (MPPyrrTFSI) and lithium bis(trifluoromethanesulfon)imide salt (LiTFSI) was performed. Li|electrolyte|Li and LiC6|electrolyte|Li cells were galvanostatically charged/discharged in order to form solid electrolyte interphase (SEI) protecting layer. SEM images showed that the surface of both Li and LiC6 anodes was covered with small particles. The fitting procedure of electrochemical impedance data taken at different temperatures gave three resistances (R el, R SEI, R ct) and hence, three lnR = f(T ?1) straight lines of different slopes. Specific conductivity and activation energy of the conduction process of the liquid electrolyte, were ca. σ = 2.5 mS cm?1 (at T = 25.0 °C) and $ E_{\text{el}}^{\# } $  = 15 kJ mol?1. Activation energy for the conduction process in the SEI layer was ca. 56 kJ mol?1 in the case of the metallic lithium and 62 kJ mol?1 for the graphite anode. Activation energy of the charge transfer process, $ E_{\text{ct}}^{\# } $ , for Li and LiC6 anodes was 71 and 65 kJ mol?1, respectively. Analysis of literature data for different electrolytes suggests that the $ E_{\text{ct}}^{\# } $ value for Li+ reduction may be approximated by 57 ± 5 kJ mol?1. Activation energy for the diffusion processes in the graphite electrode, detected from the Warburg coefficient, was ca 74 kJ mol?1.  相似文献   

18.
A series of novel cationic gemini surfactants, namely 1,3-adamantanedicarboxylic acid bis(alkyldimethyl-3-ammoniopropyl amide) dibromide designated as [Ad-2(amC n )] (n = 12, 14, 16), containing adamantane, two amide groups, and two hydrocarbon chains, were synthesized from 1,3-adamantanedicarboxylic acid. The surface-active properties of the surfactants were investigated through surface tension and electrical conductivity measurement. A series of thermodynamic parameters such as standard free energy \(\left( {\Delta G^\circ_{\text{m}} } \right)\) , enthalpy \(\left( {\Delta H^\circ_{\text{m}} } \right)\) , and entropy \(\left( {\Delta S^\circ_{\text{m}} } \right)\) of micellization were evaluated from electrical conductivity measurements in the temperature range from 288 to 308 K. The micellization for [Ad-2(amC n )] is entropy-driven at low temperature and enthalpy-driven at high temperature. Further, the antimicrobial activity of the synthesized gemini surfactants against both Gram-positive and Gram-negative bacteria was also investigated, and this study showed that the compound [Ad-2(amC12)] has excellent antibacterial activity against all studied bacteria.  相似文献   

19.
The surface properties and mixed micellization behavior of binary combinations of an ionic liquid surfactant, namely, 1-tetradecyl-3-methylimidazolium bromide ([C14mim]Br) with common cationic surfactants viz. tetradecyltrimethylammonium bromide and tetradecylpyridinium bromide in the presence of sodium bromide (NaBr) were investigated by surface tension and conductivity measurements. The critical micelle concentration (CMC) and interfacial parameters, such as the maximum surface excess (Γmax), minimum area per molecule (Amin) and surface pressure at the CMC (πCMC) were determined from the surface tension data. The CMC and Γmax values were found to decrease with increasing salt concentrations. The $ \Updelta G_{\text{ad}}^{ \circ } $ and $ \Updelta G_{\text{m}}^{ \circ } $ values are negative indicating the spontaneity of micelle formation.  相似文献   

20.
A comparative analysis is performed of the variations in the total concentration of the main components $\left( {\sum\limits_i {c_i } } \right)$ , in the solutions proposed and used in different years for electroplating individual metals (Cr, Cu, Ni, Zn, Sn, Cd, Pb, and Fe). A quantitative concentration criterion is determined for classifying solutions into resource-saving ( $\left( {\sum\limits_i {c_i \leqslant 2.32} } \right)$ mol-equiv/L) and resourceintensive ( $\left( {\sum\limits_i {c_i \geqslant 2.78} } \right)$ mol-equiv/L) compositions. In addition to scientific interest, this material can be useful for developing studies aimed at reducing the negative environmental impact of electroplating shops or sections.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号