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1.
Neha Kandpal Hitesh K. Dewangan Rekha Nagwanshi Kallol K. Ghosh 《Journal of Dispersion Science and Technology》2019,40(4):604-611
Kinetic studies have been performed to understand the hydrolytic potencies of oximate (2- and 4-pyridinealdoxime) and its functionalized oximate (4-(hydroxyiminomethyl)-1-alkylpyridinium bromide) ions (alkyl?=?C10H21 (4-C10PyOx-); alkyl?=?C12H25 (4-C12PyOx-)) in the cleavage of phosphate esters, diethyl p-nitrophenylphosphate (Paraoxon) and p-nitrophenyl diphenyl phosphate (PNPDPP) in a cationic (O/W) microemulsion system (ME) over a pH range 7.5 to 11.0 at 300?K. The kobs values for the reaction of paraoxon with oximate and its functionalized oximate were determined in different microemulsion composition and the kinetic rate data shows that kobs values increases with increasing water content. The specificity of different chain length of alcohols (n-butanol, n-pentanol, n-hexanol and n-octanol) was also investigated in hydrolytic reactions of paraoxon for different microemulsion composition. 相似文献
2.
Wei Li Jianling Zhang Dr. Yueju Zhao Minqiang Hou Dr. Buxing Han Prof. Dr. Cailan Yu Jianping Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(4):1296-1305
The study of the micelle‐to‐vesicle transition (MVT) is of great importance from both theoretical and practical points of view. Herein, we studied the effect of compressed CO2 on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactants in aqueous solution by means of direct observation, turbidity and conductivity measurements, steady‐state fluorescence, time‐resolved fluorescence quenching (TRFQ), fluorescence quantum yield, and template methods. Interestingly, all these approaches showed that compressed CO2 could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO2 can be used to switch the MVT reversibly by controlling pressure. Some other gases, such as methane, ethylene, and ethane, could also induce the MVT of the surfactant solution. A possible mechanism is proposed on the basis of the packing‐parameter theory and thermodynamic principles. It is shown that the mechanism of the MVT induced by a nonpolar gas is different from the MVT induced by polar and electrolyte additives. 相似文献
3.
Fernando Moyano Dr. R. Dario Falcone Dr. J. C. Mejuto Dr. Juana J. Silber Prof. N. Mariano Correa Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8887-8893
Reverse micelles (RMs) are very good nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different RM interfaces on the hydrolysis of 2‐naphthyl acetate (2‐NA) by α‐chymotrypsin (α‐CT). The reaction was studied in water/benzyl‐n‐hexadecyldimethylammonium chloride (BHDC)/benzene RMs and, its efficiency compared with that observed in pure water and in sodium 1,4‐bis‐2‐ethylhexylsulfosuccinate (AOT) RMs. Thus, the hydrolysis rates of 2‐NA catalyzed by α‐CT were determined by spectroscopic measurements. In addition, the method used allows the joint evaluation of the substrate partition constant Kp between the organic and the micellar pseudophase and the kinetic parameters: catalytic rate constant kcat, and the Michaelis constant KM of the enzymatic reaction. The effect of the surfactant concentration on the kinetics parameters was determined at constant W0=[H2O]/[surfactant], and the variation of W0 with surfactant constant concentration was investigated. The results show that the classical Michaelis–Menten mechanism is valid for α‐CT in all of the RMs systems studied and that the reaction takes place at both RM interfaces. Moreover, the catalytic efficiency values kcat/KM obtained in the RMs systems are higher than that reported in water. Furthermore, there is a remarkable increase in α‐CT efficiency in the cationic RMs in comparison with the anionic system, presumably due to the unique water properties found in these confined media. The results show that in cationic RMs the hydrogen‐bond donor capacity of water is enhanced due to its interaction with the cationic interface. Hence, entrapped water can be converted into “super‐water” for the enzymatic reaction studied in this work. 相似文献
4.
Nanoscale Control Over Interfacial Properties in Mixed Reverse Micelles Formulated by Using Sodium 1,4‐bis‐2‐ethylhexylsulfosuccinate and Tri‐n‐octyl Phosphine Oxide Surfactants
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Emmanuel Odella Dr. R. Darío Falcone Prof. Juana J. Silber Prof. Dr. N. Mariano Correa 《Chemphyschem》2016,17(15):2407-2414
The interfacial properties of pure reverse micelles (RMs) are a consequence of the magnitude and nature of noncovalent interactions between confined water and the surfactant polar head. Addition of a second surfactant to form mixed RMs is expected to influence these interactions and thus affect these properties at the nanoscale level. Herein, pure and mixed RMs stabilized by sodium 1,4‐bis‐2‐ethylhexylsulfosuccinate and tri‐n‐octyl phosphine oxide (TOPO) surfactants in n‐heptane were formulated and studied by varying both the water content and the TOPO mole fraction. The microenvironment generated was sensed by following the solvatochromic behavior of the 1‐methyl‐8‐oxyquinolinium betaine probe and 31P NMR spectroscopy. The results reveal unique properties of mixed RMs and we give experimental evidence that free water can be detected in the polar core of the mixed RMs at very low water content. We anticipate that these findings will have an impact on the use of such media as nanoreactors for many types of chemical reactions, such as enzymatic reactions and nanoparticle synthesis. 相似文献
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Prof. Lucia Zakharova Dr. Mikhail Voronin Dr. Vyacheslav Semenov Dinar Gabdrakhmanov Dr. Victor Syakaev Dr. Yuri Gogolev Dr. Rashit Giniyatullin Dr. Svetlana Lukashenko Prof. Vladimir Reznik Dr. Shamil Latypov Alexander Konovalov Prof. Yuri Zuev 《Chemphyschem》2012,13(3):788-796
Novel mono‐ and dicationic pyrimidinic surfactants are synthesized and their aggregation behavior is studied by methods of tensiometry and nuclear magnetic resonance (NMR) self‐diffusion. To estimate their potentiality as gene delivery agents, the complexation with oligonucleotides (ONus) is explored by dynamic light scattering (DLS) and zeta‐potential titration methods and ethidium bromide exclusion experiments. Bola‐type pyrimidinic amphiphile (BPM) demonstrates rather a weak affinity to ONus. Although it induces mixed associations with ONus, only slight charge compensation changes occur at a large excess of bola, with no recharging reached. Similarly, the ethydium bromide exclusion study reveals a slow increase in the binding capacity toward an ONu with an increment in BPM concentration. The monocationic pyrimidinic surfactant (MPM) and its gemini analogue (GPM‐1) are ranked as intermediates in both their aggregative activity and complexing properties toward ONus. They both form mixed associates with ONus well below the critical micelle concentrations (cmcs) of 2 and 15 mM respectively. However, GPM‐1 has a much lower isoelectric point at the molar ratio surfactant/ONu r~1 compared to r~3 for MPM. This probably indicates a larger electrostatic contribution to the ONu complexation in the case of GPM‐1. The most hydrophobic pyrimidinic surfactant (GPM‐2), bearing three alkyl tails, demonstrates enhanced aggregative activity and binding capacity toward ONus as compared to former pyrimidinic surfactants. Due to effective aggregative (low cmc of 0.04 mM ) plus binding properties (fraction of bound ONu β=0.76 at r=2.5), GPM‐2 may be ranked as a promising agent for wider biological applications. 相似文献
7.
Self‐Assembly of Imidazolium‐Based Surfactants in Magnetic Room‐Temperature Ionic Liquids: Binary Mixtures
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The phase behaviour of binary mixtures of ionic surfactants (1‐alkyl‐3‐imidazolium chloride, CnmimCl with n=14, 16 and 18) and imidazolium‐based ionic liquids (1‐alkyl‐3‐methylimidazolium tetrachloroferrate, CnmimFeCl4, with n=2 and 4) over a broad temperature range and the complete range of compositions is described. By using many complementary methods including differential scanning calorimetry (DSC), polarised microscopy, small‐angle neutron and X‐ray scattering (SANS/SAXS), and surface tension, the ability of this model system to support self‐assembly is described quantitatively and this behaviour is compared with common water systems. The existence of micelles swollen by the solvent can be deduced from SANS experiments and represent a possible model for aggregates, which has barely been considered for ionic‐liquid systems until now, and can be ascribed to the rather low solvophobicity of the surfactants. Our investigation shows that, in general, CnmimCl is a rather weak amphiphile in these ionic liquids. The amphiphilic strength increases systematically with the length of the alkyl chain, as seen from the phase behaviour, the critical micelle concentration, and also the level of definition of the aggregates formed. 相似文献
8.
Erik Frotscher Bartholomäus Danielczak Dr. Carolyn Vargas Priv.‐Doz. Annette Meister Dr. Grégory Durand Prof. Sandro Keller 《Angewandte Chemie (International ed. in English)》2015,54(17):5069-5073
Surfactants carrying fluorocarbon chains hold great promise as gentle alternatives to conventional hydrocarbon‐based detergents for the solubilization and handling of integral membrane proteins. However, their inertness towards lipid bilayer membranes has limited the usefulness of fluorinated surfactants in situations where detergent‐like activity is required. We demonstrate that fluorination does not necessarily preclude detergency, as exemplified by a fluorinated octyl maltoside derivative termed F6OM. This nonionic compound readily interacts with and completely solubilizes phospholipid vesicles in a manner reminiscent of conventional detergents without, however, compromising membrane order at subsolubilizing concentrations. Owing to this mild and unusual mode of detergency, F6OM outperforms a lipophobic fluorinated surfactant in chaperoning the functional refolding of an integral membrane enzyme by promoting bilayer insertion in the absence of micelles. 相似文献
9.
I. S. Ryzhkina L. A. Kudryavtseva Ya. A. Babkina K. M. Enikeev M. A. Pudovik A. I. Konovalov 《Russian Chemical Bulletin》2000,49(8):1355-1359
The reaction kinetics of aminomethylated calix[4]resorcinolarenes (AMC) withp-nitrophenyl esters of phosphorus acids (EPA) in a water—DMF solution (30 vol.% DMF) was studied by spectrophotometry and31P NMR spectroscopy in the presence and absence of the nonionic surfactant Triton X-100. The AMC form aggregates of micellar
and nonmicellar types and are the catalysts for EPA hydrolysis. The catalytic activity of the aggregates depends on their
structure, pH of the medium, and the nature of the solvent.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1361–1365, August, 2000. 相似文献
10.
There are two platforms in the surface tension vs. concentration curve (γ‐lgC curve) of cationic‐anionic surfactant mixtures. The first platform is the same as that of common surfactant solution, and the cross point is the CMC. After the CMC, the mixtures form precipitate. At higher concentration, the mixtures form homogeneous solution again. When the mixtures form homogeneous solution at high concentration, surface tension increases with concentration, then becomes constant. So the γ‐lgC curve exhibits the second platform. The surface tension at the second platform increases by increasing molar ratio of two surfactants and polar group size of surfactants, and decreases with adding inorganic salts. 相似文献
11.
Yanfei Shen Dr. Yuanjian Zhang Dr. Daniel Kuehner Dr. Guifu Yang Dr. Fuyu Yuan Li Niu Prof. Dr. 《Chemphyschem》2008,9(15):2198-2202
We propose a simple but efficient, rapid, and quantitative ion‐responsive micelle system based on counter‐anion exchange of a surfactant with an imidazolium unit. The ion‐exchange reaction results in the amphiphilic‐to‐hydrophobic transition of the imidazolium salt, leading to the destruction of the micelles, which has been successfully applied to controlled release and emulsification. The proposed design offers a novel alternative stimulus to control these smart physical aggregates besides pH, temperature and light—with extra advantages. Our finding greatly benefits both fundamental research and industry. 相似文献
12.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(16):1815-1824
We report a new design of photolabile acetal‐containing amphiphilic block copolymers. Acetals as protecting groups for carbonyls or diols can be hydrolyzed under acidic condition but very stable with respect to hydrolysis at pH > 7. When combining light‐capturing chromophores with acetals, the hydrolysis of acetals can be activated by light to design dual responsive acetal‐containing polymers. Using acetalization reaction of 2,3‐dihydroxypropyl methacrylate with benzaldehyde derivatives, two new acetal‐containing photolyzable monomers have been designed. Comparable to commonly used photolabile monomers containing nitrobenzyl esters, the two acetal‐containing monomers are easy to polymerize using atom transfer radical polymerization with excellent molecular weight and dispersity control. We studied the cleavage kinetics and mechanism of acetal groups in both monomers and polyethylene oxide (PEO)‐containing amphiphilic block copolymers using 1H NMR and UV–vis spectroscopy. o‐Nitrobenzaldehyde acetal showed a Norrish Type II rearrangement to form benzoic ester; while, 2,5‐dimethoxy benzaldehyde acetal was photolabile to completely release 2,3‐dihydroxypropyl methacrylate. The photocleavage of acetals is a zero‐order reaction in regardless of molecular states of acetals; while, the acid‐cleavage of acetals proves to be a first‐order kinetics and the cleavage becomes much slower for polymers. The self‐assembly of acetal‐containing amphiphilic block copolymers and the acid‐/light‐controlled dissociation of their vesicles have been investigated. We demonstrate that those acetal‐containing polymers are potentially useful as smart drug delivery systems where the release kinetics of payloads is tunable using light and pH as triggers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1815–1824 相似文献
13.
William B. Tucker Aaron M. McCoy Samantha M. Fix Melissa F. Stagg Matt M. Murphy Sandro Mecozzi 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3324-3336
Linear, dibranched, and miktoarm amphiphiles containing both hydrophobic and fluorophilic moieties were synthesized and characterized in an attempt to elucidate the relationship between semifluorinated amphiphile structure and aggregate behavior in aqueous solution. For the linear and dibranched amphiphiles, there was an exponential decrease in critical aggregation concentration (CMC) and a logarithmic increase in core microviscosity with increasing length of the fluorocarbon segments; while the miktoarm architecture produced no notable trend in microviscosity or CMC. Furthermore, the linear and dibranched surfactants showed enhanced kinetic stability, dissociating more slowly in the presence of human serum than did either the dibranched or miktoarm amphiphiles. Finally, encapsulation studies with the hydrophobic drug paclitaxel (PTX) showed that the ability to solubilize and retain PTX increased with the presence and with the increasing size of the fluorocarbon moiety for both the linear and dibranched amphiphiles, while no such trend was observed for the miktoarm amphiphiles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3324–3336 相似文献
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16.
Exploiting Co‐solubilization of Warfarin,Curcumin, and Rhodamine B for Modulation of Energy Transfer: A Micelle FRET On/Off Switch
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Dr. Parvaiz Ahmad Bhat Dr. Oyais Ahmad Chat Prof. Aijaz Ahmad Dar 《Chemphyschem》2016,17(15):2360-2372
Two new FRET pairs, warfarin (WF)–curcumin (CUR) and curcumin–rhodamine B (RhB), are explored by using surfactant‐based self‐assembled soft systems as scaffolds. The study is extended to design a two‐step concurrent FRET system based on these three fluorophores, which is an important mechanism to devise artificial light‐harvesting/antenna systems. Surfactant systems of varying nature (cationic, anionic, nonionic, and zwitterionic) are exploited to modulate the energy transfer in different FRET systems. Interestingly, micelle/water interfacial‐charge‐responsive FRET is observed owing to selective solubilization of the fluorophores during co‐solubilization. The step‐one FRET (WF→CUR) is switched on in cationic and zwitterionic media but switched off in anionic/nonionic media, whereas the step‐two FRET from CUR to RhB is switched on in anionic/nonionic and zwitterionic media. However, both the FRET steps (WF→CUR→RhB) are observed to be active only in zwitterionic medium. Co‐solubilized, appropriately mixed fluorophores having multistep FRET possibilities can be switched on/off selectively as and when required and energy efficiency can be tuned to an optimal level by varying the nature and geometry of the micellar scaffold. Thus, the two FRET pairs selectively acknowledge all types of media for their anticipated applications in biological systems, as structural tools, and for the development of artificial light‐harvesting/antenna systems and lasers. 相似文献
17.
Ken‐Ichi Seno Itsuko Tsujimoto Takunobu Kikuchi Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6151-6164
Thermosensitive forced gradient copolymers with various sequence distributions were synthesized by living cationic polymerization in the presence of an added base. The synthesis was conducted using a semibatch reaction method, which is unfavorable for ionic polymerization, especially when a simple apparatus is employed. Polymerization of 2‐ethoxyethyl vinyl ether (EOVE) was initiated using a conventional syringe technique. Immediately after initiation, 2‐methoxyethyl vinyl ether (MOVE) was continuously added using a syringe pump at regulated feed rates, which allowed control of the sequence distribution. The resulting gradient copolymers of EOVE and MOVE underwent thermally induced association in water, forming micelles with a hydrophobic core derived from EOVE‐rich segments. Interestingly, the size of the micelles obtained from gradient copolymers decreased monotonously with increasing solution temperature, while the micelles of the corresponding block copolymers were unchanged in size. This self‐association behavior can be controlled by designing the gradient pattern of the instantaneous composition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6151–6164, 2008 相似文献
18.
At frequencies between 100 kHz and 400 MHz, ultrasonic attenuation spectra are measured at 25 °C for aqueous solutions of hexyl‐, heptyl‐, octyl‐, nonyl‐, and decyl‐β‐D ‐maltopyranoside as well as of decyl‐α‐D ‐maltopyranoside. The spectra with surfactant concentration c above the relevant critical micelle concentration (cmc) display three relaxation terms with discrete relaxation times. That with a relaxation time between 0.1 and 1.2 μs is due to exchange of monomers between micelles and the suspending phase. It is discussed in the light of the Teubner–Kahlweit–Aniansson–Wall model of the formation/decay kinetics of systems with Gaussian size distribution of micelles. The relaxation parameters are compared to those for solutions of other non‐ionic surfactants, such as alkyl monoglycosides and poly(ethylene glycol) monoalkyl ethers. At c<cmc this low‐frequency relaxation term is missing and at c≈cmc it is broadened, as is characteristic of solutions of oligomeric molecular structures rather than proper micelles. The relaxation terms with relaxation times between 6 and 15 ns and 0.7 and 2.3 ns reveal head‐group rotations around glycosidic angles and isomerization of the exocyclic hydroxymethyl group, respectively. These unimolecular reactions are also examined with a view to solutions of alkyl monoglycosides as well as of glucose and maltose. 相似文献
19.
The effect of the addition of a zwitterionic sulfobetaine to a dye‐containing polymer gel composed of two polymers – poly(vinyl alcohol) (PVA) and polyether – was investigated. With increasing sulfobetaine content a remarkable reduction of the UV‐vis‐absorption intensity of the longest wavelength absorption band of Phenol Red in the aqueous polymer network was observed, even for sulfobetaine concentrations below its critical micelle concentration (cmc). It can be assumed that this effect is based on the formation of ionic complexes between dye molecules and either single sulfobetaine molecules or aggregates of sulfobetaine. Furthermore, thermotropic behavior occurs in the investigated polymer gel system even at a polyether concentration as low as 0.8 wt%. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
20.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(11):1140-1145
Allyl‐telechelic polyisobutylene (A‐PIB‐A) produced by the bis‐benzocyclobutane dichloride (bBCB‐diCl) initiator contains the bis‐benzocyclobutane (bBCB) fragment at the center of the macromolecule (A‐PIB‐bBCB‐PIB‐A). Thermolysis of A‐PIB‐bBCB‐PIB‐A quantitatively converts the central bBCB fragment to a substituted conjugated tetraene (A‐PIB‐tetraene‐PIB‐A). The structure of A‐PIB‐tetraene‐PIB‐A was anticipated from small molecule models and identified/quantitated by 1H NMR spectroscopy. This is the first time a reactive functional group was introduced at the statistical center of a (telechelic) PIB. Subsequently, the A‐PIB‐tetraene‐PIB‐A was peroxidized to an epoxy derivative. Reaction of the A‐PIB‐tetraene‐PIB‐A with HSCH2CH2OH produced HOCH2‐telechelic PIB containing a central CH2OH function, and hydrosilation with HSi(Me2)‐O‐Si(Me2)H produced SiH‐telechelic PIB with a central SiH function. Reactions with maleic anhydride, tetracyanoethylene, butyl lithium, and potassium permanganate have also been examined. In sum, A‐PIB‐bBCB‐PIB‐A and A‐PIB‐tetraene‐PIB‐A are useful intermediates for the synthesis of novel PIB‐based materials for various end uses under investigation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1140–1145 相似文献