阳离子与非离子混合表面活性剂模板合成介孔SiO2

利用各种两亲分子有序组合体构成超分子模板,合成从介观到宏观尺度不同形态的无机材料成为材料科学新崛起的研究方向[1].介孔SiO2在催化、吸附、分离介质及化学传感器等方面有广阔的应用前景.     

Sensing micelle hydration by proton-transfer dynamics of a 3-hydroxychromone dye: role of the surfactant headgroup and chain length

The dynamics of the excited-state intramolecular proton-transfer (ESIPT) reaction of 2-(2'-furyl)-3-hydroxychromone (FHC) was studied in micelles by time-resolved fluorescence. The proton-transfer dynamics of FHC was found to be sensitive to the hydration and charge of the micelles, demonstrated through a decrease of the ESIPT rate constant (k(PT)) in the sequence cationic → nonionic → anionic micelles. A remarkably slow ESIPT with a time constant (τ(PT)) of ~100 ps was observed in the anionic sodium dodecyl sulfate and sodium tetradecyl sulfate micelles, whereas it was quite fast (τ(PT) ≈ 15 ps) in the cationic cetyltrimethylammonium bromide and tetradecyltrimethylammonium bromide micelles. In the nonionic micelles of Brij-78, Brij-58, Tween-80, and Tween-20, ESIPT occurred with time constants (τ(PT) ≈ 35-65 ps) intermediate between those of the cationic and anionic micelles. The slower ESIPT dynamics in the anionic micelles than the cationic micelles is attributed to a relatively stronger hydration of the negatively charged headgroups of the former than the positively charged headgroups of the latter, which significantly weakens the intramolecular hydrogen bond of FHC in the Stern layer of the anionic micelles compared to the latter. In addition, electrostatic attraction between the positively charged -N(CH(3))(3)(+) headgroups and the negatively charged 4-carbonyl moiety of FHC effectively screens the intramolecular hydrogen bond from the perturbation of water molecules in the micelle-water interface of the cationic micelles, whereas in the anionic micelles, this screening of the intramolecular hydrogen bond is much less efficient due to an electrostatic repulsion between its negatively charged -OSO(3)(-) headgroups and the 4-carbonyl moiety. As for the nonionic micelles, a moderate level of hydration, and the absence of any charged headgroups, causes an ESIPT dynamics faster than that of the anionic but slower than that of the cationic micelles. Furthermore, the ESIPT rate decreased with a decrease of the hydrophobic chain length of the surfactants due to the stronger hydration of the micelles of shorter chain surfactants than those of longer chain surfactants, arising from a less compact packing of the former surfactants compared to the latter surfactants.     

Self-assembly of hydrophobin and hydrophobin/surfactant mixtures in aqueous solution

The self-assembly of the protein hydrophobin, HFBII, and its self-assembly with cationic, anionic, and nonionic surfactants hexadecylterimethyl ammonium bromide, CTAB, sodium dodecyl sulfate, SDS, and hexaethylene monododecyl ether, C(12)E(6), in aqueous solution have been studied by small-angle neutron scattering, SANS. HFBII self-assembles in solution as small globular aggregates, consistent with the formation of trimers or tetramers. Its self-assembly is not substantially affected by the pH or electrolytes. In the presence of CTAB, SDS, or C(12)E(6), HFBII/surfactant complexes are formed. The structure of the HFBII/surfactant complexes has been identified using contrast variation and is in the form of HFBII molecules bound to the outer surface of globular surfactant micelles. The binding of HFBII decreases the surfactant micelle aggregation number for increasing HFBII concentration in solution, and the number of hydrophobin molecules bound/micelle increases.     

Microstructure of un-neutralized hydrophobically modified alkali-soluble emulsion latex in different surfactant solutions

At low pH conditions and in the presence of anionic, cationic, and nonionic surfactants, hydrophobically modified alkali-soluble emulsions (HASE) exhibit pronounced interaction that results in the solubilization of the latex. The interaction between HASE latex and surfactant was studied using various techniques, such as light transmittance, isothermal titration calorimetry, laser light scattering, and electrophoresis. For anionic surfactant, noncooperative hydrophobic binding dominates the interaction at concentrations lower than the critical aggregation concentration (CAC) (C < CAC). However, cooperative hydrophobic binding controls the formation of mixed micelles at high surfactant concentrations (C > or = CAC), where the cloudy solution becomes clear. For cross-linked HASE latex, anionic surfactant binds only noncooperatively to the latex and causes it to swell. For cationic surfactant, electrostatic interaction occurs at very low surfactant concentrations, resulting in phase separation. With further increase in surfactant concentration, noncooperative hydrophobic and cooperative hydrophobic interactions dominate the binding at low and high surfactant concentrations, respectively. For anionic and cationic surfactant systems, the CAC is lower than the critical micelle concentration (CMC) of surfactants in water. In addition, counterion condensation plays an important role during the binding interaction between HASE latex and ionic surfactants. In the case of nonionic surfactants, free surfactant micelles are formed in solution due to their relatively low CMC values, and HASE latexes are directly solubilized into the micellar core of nonionic surfactants.     

Size-dependent interaction of silica nanoparticles with different surfactants in aqueous solution

The size-dependent interaction of anionic silica nanoparticles with ionic (anionic and cationic) and nonionic surfactants has been studied using small-angle neutron scattering (SANS). The surfactants used are anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB), and nonionic decaoxyethylene n-dodecylether (C(12)E(10)). The measurements have been carried out for three different sizes of silica nanoparticles (8, 16, and 26 nm) at fixed concentrations (1 wt % each) of nanoparticles and surfactants. It is found that irrespective of the size of the nanoparticles there is no significant interaction evolved between like-charged nanoparticles and the SDS micelles leading to any structural changes. However, the strong attraction of oppositely charged DTAB micelles with silica nanoparticles results in the aggregation of nanoparticles. The number of micelles mediating the nanoparticle aggregation increases with the size of the nanoparticle. The aggregates are characterized by fractal structure where the fractal dimension is found to be constant (D ≈ 2.3) independent of the size of the nanoparticles and consistent with diffusion-limited-aggregation-type fractal morphology in these systems. In the case of nonionic surfactant C(12)E(10), micelles interact with the individual silica nanoparticles. The number of adsorbed micelles per nanoparticle increases drastically whereas the percentage of adsorbed micelles on nanoparticles decreases with the increase in the size of the nanoparticles.     

Study of mixtures of n-dodecyl-beta-D-maltoside with anionic, cationic, and nonionic surfactant in aqueous solutions using surface tension and fluorescence techniques

Surfactants of practical interest are invariably mixtures of different types. In this study, mixtures of sugar-based n-dodecyl-beta-D-maltoside with cationic dodecyltrimethylammonium bromide, anionic sodium dodecylsulfate, and nonionic pentaethyleneglycol monododecyl ether in solution, with and without supporting electrolyte, have been studied using surface tension and fluorescence spectroscopic techniques. Interaction parameters and mole fraction of components in mixed micelles were calculated using regular solution theory. The magnitude of interactions between n-dodecyl-beta-D-maltoside and other surfactants followed the order anionic/nonionic > cationic/nonionic > nonionic/nonionic mixtures. Since all surfactants have the same hydrophobic groups, strengths of interactions are attributed to the structures of hydrophilic headgroups. Electrolyte reduced synergism between n-dodecyl-beta-D-maltoside and ionic surfactant due to charge neutralization. Industrial sugar-based surfactant, dodecyl polyglucoside, yielded results similar to that with dodecyl maltoside, implying that tested commercial alkyl polyglucosides are similar to the pure laboratory samples in synergistic interactions with other surfactants. Fluorescence study not only supported the cmc results using tensiometry, but showed that interfaces of all the above mixed micelle/solution interfaces are mildly hydrophobic. Based on these results, an attempt is made to discover the nature of interactions to be a combination of intermolecular potential energies and free energy due to packing of surfactant molecules in micelles.     

Widening of the elution window in micellar electrokinetic chromatography with cationic surfactants. II. Cationic additives and modifiers of the electroosmotic flow.

In micellar electrokinetic chromatography (MEKC) with cationic surfactants the migration window is significantly narrower than with anionic surfactants. In order to overcome this disadvantage of cationic surfactants, it is investigated whether it is possible to widen the migration window by reducing the velocity of the aqueous phase while the electrophoretic mobility of the micelles is maintained. Short chain alkylammonium compounds, hexamethonium bromide and hydroxypropylmethylcellulose are tested as additives to the separation electrolyte with the potential to improve the migration window via reducing the velocity of the electroosmotic flow. It will be shown that these modifiers can be successfully used in order to widen the migration window in MEKC with cationic surfactant employing an alkyltrimethylammonium bromide as micelle forming agents. Influence of the modifiers selected on retention of neutral and acidic solutes and on efficiency of the separation system is investigated.     

Molecular interaction of Congo Red with conventional and cationic gemini surfactants

Interaction of tetradecyltrimethylammonium bromide (TTAB), octylophenylpolyoxyethylene ether (TX-100), sodium dodecylsulfate (SDS), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (14,4,14) and N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12) with an anionic diazo dye, Congo Red, was investigated using conductometry, spectroscopy, tensiometry, and pulsed field gradient NMR (PFG-NMR). The formation of dye-surfactant ion pairs, their small mixed aggregates (below the critical micelle concentration (CMC) of these surfactants) and surfactant micelles were detected successfully. Above the CMC, the dye reverted to its monomeric state and solubilized in the micelles. Job's method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs and revealed the formation of more hydrophile ion pairs for geminis compared to their conventional analogs. Quantitative results obtained from tensiometry indicated the existence of considerable synergism for cationic surfactants and antagonism for anionic SDS. In addition, the synergism observed for TX-100 revealed the effect of π-π stacking and hydrophobic forces on ion pair and mixed micelle formation. The increase of dye-surfactant interactions by increasing the electrical charge and chain length of cationic surfactants confirmed the importance of both electrostatic and hydrophobic forces in binary dye/surfactant systems. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the cationic and nonionic micelles increased in the presence of CR molecules.     

Kinetics of alkaline fading of methyl violet in micellar solutions of surfactants: Comparing Piszkiewicz's,Berezin's,and pseudophase ion-exchange models

The micellar effect of surfactants of various types on the rate of the reaction between methyl violet and hydroxide ion is studied. The absorption spectra show that the cation of methyl violet is bound by micelles of all types at proper concentrations of surfactants. The observed rate constant in micellar systems containing nonionic Brij-35, zwitterionic 3-(dimethyldodecylammonio)-propanesulfonate, cationic cetyltrimethylammonium bromide and hydroxide surfactants is higher, whereas in solutions of the anionic surfactant sodium dodecylsulfate is lower than that one in the surfactant-free system. Piszkiewicz's, Berezin's, and pseudophase ion-exchange models of the kinetic micellar effect are used for the treatment of the dependences of the above-mentioned constants on the surfactant concentration. The values of the corresponding kinetic parameters are compared and discussed. The influence of nonionic, zwitterionic, and anionic micelles on the reaction rate is discussed on the basis of medium and concentration kinetic effects. The character of the cationic micelles effect is somewhat paradoxical. Although the observed pseudo–first-order reaction rate constant substantially increases in the presence of such micelles, the second order-rate constant in these micelles is lower than the corresponding value in surfactant-free aqueous solution. As a possible explanation, the decrease in the reactivity of the HO^– ions is proposed, owing to their electrostatic association with the cationic headgroups (“diverting effect”).     

Effect of self‐assemblies of various surfactants in their single and mixed states on the BZ oscillatory reaction

Micelles of different surfactants are well known to affect chemical equilibria and reactivities by selectively sequestering the reagent substrates through electrostatic and hydrophobic interactions. In this article, the effects of micelles of various surfactants on different parameters of the Ce(IV)‐catalyzed Belousov–Zhabotinsky (BZ) oscillatory reaction at 35°C in nonstirred closed conditions are studied by employing spectrophotometry and tensiometry. Surfactants used in this study are the cationics hexadecyltrimethylammonium bromide (CTAB) and pentamethylene‐1,5‐bis(N‐hexadecyl‐N,N‐dimethylammonium)bromide gemini (Gemini), anionic sodium dodecylbenzene sulfonate (SDBS), and nonionic Brij58, whereas the binary surfactant systems used are cationic–nonionic CTAB+Brij58 and anionic–nonionic SDBS+Brij58. The results revealed that the induction period shows a definite variation with increasing concentration of different surfactants above their critical micelle concentration (cmc). The amplitudes of oscillation and absorbance maxima and minima are enhanced in the presence of micelles of CTAB and Gemini surfactants, whereas micelles of SDBS and Brij58 have almost no effect on the nature of the oscillations. However, mixed micelles of CTAB+Brij58 and SDBS+Brij58 binary mixtures show a quite different effect on the overall behavior of the oscillations. The enhanced effect of CTAB and Gemini surfactants on the overall nature of oscillations has been attributed to the positive charge on the surface of their micelles and to some extent on the presence of nitrogen in their head group. The effect of mixed binary micelles may be attributed to their synergistic nature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 659–668, 2010     

Amphiphilic azobenzenesulfonic acid anionic surfactant for water-soluble, ordered, and luminescent polypyrrole nanospheres

Self-organized micelles of new renewable resource amphiphilic azobenzenesulfonic acid anionic surfactant were utilized to prepare water-soluble, luminescent, and highly ordered polypyrrole nanomaterials. The micellar behavior of the reaction medium was precisely controlled by varying the composition of pyrrole/surfactant ratio from 3 to 100 (up to 100 times lower amount of surfactant with respect to pyrrole), and polypyrrole nanospheres of 150-800 nm were prepared. Dynamic light scattering (DLS) and viscosity techniques were employed as tools to trace the factors, which control the mechanism of polypyrrole nanomaterials formation. DLS studies confirmed that the surfactant exists as in the form of spherical micelles of 4.8 nm diameter in water. Specific viscosity measurement revealed that the pyrrole+surfactant complexes in water exist in the form of either aggregated or isolated micelles depending upon their composition in the feed. SEM and TEM analysis confirmed that the aggregated micellar templates produced coral-like morphology, whereas uniform polypyrrole nanospheres of 150-400 nm were obtained at low micellar concentration. The nanomaterials formation was unperturbed by the variation of the oxidation agents such as ammonium persulphate (APS) or ferric chloride (FeCl3). WXRD analysis of the nanomaterials indicates that the anionic surfactant effectively penetrates into the polypyrrole chains, and a new peak at 2theta = 6.3 degrees (d-spacing = 14 A) was observed corresponding to highly ordered polymer chains. UV-vis and FT-IR confirmed the highly doped state, and the conductivity of the samples was obtained in the range of 10(-1) to 10(-2) S/cm by four-probe conductivity measurements. The azobenzenesulfonic acid anionic surfactant is luminescent in water, and its grafting on the polypyrrole nanospheres enhances the luminescent intensity with the quantum yield in the range of 2 x 10(-3) to 3 x 10(-4).     

Fluorescence delineation of the surfactant microstructures in the CTAB-sOS-H2O catanionic system

A key feature of amphiphilic molecules is their ability to undergo self-assembly, a process in which a complex hierarchical structure is established without external intervention. Ternary systems consisting of aqueous mixtures of cationic and anionic surfactants exhibit a rich array of self-assembled microstructures such as spherical and rodlike micelles, unilamellar and multilamellar vesicles, planar bilayers, and bicontinuous structures. In general, multiple complementary techniques are required to explore the phase behavior and morphology of aqueous systems of oppositely charged surfactants. As a novel and effective alternative approach, we use fluorescence spectroscopic measurements to examine the microstructures of aqueous cationic/anionic surfactant systems in the dilute surfactant region. In particular, we demonstrate that the polarity-sensitive fluorophore prodan can be used to demarcate the surfactant microstructures of the ternary system of cetyltrimethylammonium bromide, sodium octyl sulfate, and water. As the fluorescence signature of this probe is dependent on the nature of the surfactant aggregates present, our method is a promising new approach to effectively map complex surfactant phase diagrams.     

A spectral approach to determine location and orientation of azo dyes within surfactant aggregates

The UV–vis absorption properties of azo dyes are known to exhibit a variation with the polarity and acidity of the dye environment. The spectral properties of a series of anionic azo dyes were characterized to further probe the interaction of these dyes with two types of surfactant aggregates: (1) the spherical micelles formed in aqueous solution by alkyltrimethylammonium bromide (C_nTAB) surfactants with n = 10–16 and (2) the unilamellar vesicles spontaneously formed in water from binary mixtures of the oppositely-charged double-tailed surfactants cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT). The observed dye spectra reflect the solvatochromic behavior of the dyes and suggest the location and orientation of the dye within the surfactant aggregates. Deconvolution of the overall spectra into sums of Gaussian curves more readily displays any contributions of tautomeric forms of the azo dyes resulting from intramolecular hydrogen bonding. The rich variation in UV/vis absorption properties of these anionic azo dyes supports their use as sensitive tools to explore the nanostructures of surfactant aggregates.     

Surfactant-directed polypyrrole/CNT nanocables: synthesis, characterization, and enhanced electrical properties.

We describe here a new approach to the synthesis of size-controllable polypyrrole/carbon nanotube (CNT) nanocables by in situ chemical oxidative polymerization directed by the cationic surfactant cetyltrimethylammonium bromide (CTAB) or the nonionic surfactant polyethylene glycol mono-p-nonylphenyl ether (Opi-10). When carbon nanotubes are dispersed in a solution containing a certain concentration of CTAB or Opi-10, the surfactant molecules are adsorbed and arranged regularly on the CNT surfaces. On addition of pyrrole, some of the monomer is adsorbed at the surface of CNTs and/or wedged between the arranged CTAB or Opi-10 molecules. When ammonium persulfate (APS) is added, pyrrole is polymerized in situ at the surfaces of the CNTs (core layer) and ultimately forms the outer shell of the nanocables. Such polypyrrole/CNT nanocables show enhanced electrical properties; a negative temperature coefficient of resistance at 77-300 K and a negative magnetoresistance at 10-200 K were observed.     

Synthesis of highly-ordered mesoporous silica particles using mixed cationic and anionic surfactants as templates

We applied a molecular assembly formed in an aqueous surfactant mixture of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium octylsulfate (SOS) as templates of mesoporous silica materials. The hexagonal pore size can be controlled between 3.22 and 3.66 nm with the mixed surfactant system. In addition, we could observe the lamellar structure of the mixed surfactants with precursor molecules, which strongly shows the possibility of precise control of both the pore size and the structure of pores by changing the mixing ratio of surfactants. Moreover, use of the cationic surfactant having longer hydrophobic chain like stearyltrimethylammonium bromide (STAB) caused the increase in d(100) space and shifted the point of phase transition from hexagonal phase to lamellar phase to lower concentration of SOS.     

Interaction between the water soluble poly{1,4-phenylene-[9,9-bis(4-phenoxy butylsulfonate)]fluorene-2,7-diyl} copolymer and ionic surfactants followed by spectroscopic and conductivity measurements

The interaction has been studied in aqueous solutions between a negatively charged conjugated polyelectrolyte poly{1,4-phenylene-[9,9-bis(4-phenoxybutylsulfonate)]fluorene-2,7-diyl} copolymer (PBS-PFP) and several cationic tetraalkylammonium surfactants with different structures (alkyl chain length, counterion, or double alkyl chain), with tetramethylammonium cations and with the anionic surfactant sodium dodecyl sulfate (SDS) by electronic absorption and emission spectroscopy and by conductivity measurements. The results are compared with those previously obtained on the interaction of the same polymer with the nonionic surfactant C12E5. The nature of the electrostatic or hydrophobic polymer-surfactant interactions leads to very different behavior. The polymer induces the aggregation with the cationic surfactants at concentrations well below the critical micelle concentration, while this is inhibited with the anionic SDS, as demonstrated from conductivity measurements. The interaction with cationic surfactants only shows a small dependence on alkyl chain length or counterion and is suggested to be dominated by electrostatic interactions. In contrast to previous studies with the nonionic C12E5, both the cationic and the anionic surfactants quench the PBS-PFP emission intensity, leading also to a decrease in the polymer emission lifetime. However, the interaction with these cationic surfactants leads to the appearance of a new emission band (approximately 525 nm), which may be due to energy hopping to defect sites due to the increase of PBS-PFP interchain interaction favored by charge neutralization of the anionic polymer by cationic surfactant and by hydrophobic interactions involving the surfactant alkyl chains, since the same green band is not observed by adding either tetramethylammonium hydroxide or chloride. This effect suggests that the cationic surfactants are changing the nature of PBS-PFP aggregates. The nature of the polymer and surfactant interactions can, thus, be used to control the spectroscopic and conductivity properties of the polymer, which may have implications in its applications.     

One-dimensional assemblies of platinum nanoparticles on a graphite surface using nonionic/ionized mixed hemicylindrical micelle templates

One-dimensional (1-D) self-assemblies of Pt nanoparticles on a graphite surface have been synthesized via a template-directed sintering process of individual nanoparticles, using nonionic/cationic mixed hemicylindrical micelle templates of dodecyldimethylamine oxide surfactant at graphite/solution interfaces. The dimension and morphology of Pt nanoparticles can be widely controlled by the concentration of Pt ions equivalent to the mixing ratio of nonionic and cationic species in the surfactant micelle. This approach could be extended to fabricate a wide range of self-assembling metallic nanostructures on surfaces using various nonionic/cationic mixed micelle-like self-assemblies carrying metal ions at interfaces, while providing a fundamental insight into a 1-D self-assembly from individual nanoparticles.     

Surfactant aggregation within room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

On the basis of the response of solvatochromic probes [Reichardt's betaine dye, pyrene, and 1,3-bis(1-pyrenyl)propane], we have investigated the aggregation behavior of common anionic, cationic, and nonionic surfactants when solubilized within a low-viscosity room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (emimTf2N). We observed possible aggregate formation by all nonionic surfactants included in the study (Brij-35, Brij-700, Tween-20, and Triton X-100), while no aggregation was observed for the cationic surfactant cetyltrimethylammonium bromide. The anionic surfactant sodium dodecyl sulfate does not appear to solubilize within emimTf2N at ambient conditions.     

Spectrophotometric study of interaction and solubilization of procaine hydrochloride in micellar systems

The interaction of Procaine hydrochloride (PC) with cationic, anionic and non-ionic surfactants; cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and triton X-100, were investigated. The effect of ionic and non-ionic micelles on solubilization of Procaine in aqueous micellar solution of SDS, CTAB and triton X-100 were studied at pH 6.8 and 29°C using absorption spectrophotometry. By using pseudo-phase model, the partition coefficient between the bulk water and micelles, K_x, was calculated. The results showed that the micelles of CTAB enhanced the solubility of Procaine higher than SDS micelles (K_x = 96 and 166 for SDS and CTAB micelles, respectively) but triton X-100 did not enhanced the solubility of drug because of weak interaction with Procaine. From the resulting binding constant for Procaine-ionic surfactants interactions (K_b = 175 and 128 for SDS and CTAB surfactants, respectively), it was concluded that both electrostatic and hydrophobic interactions affect the interaction of surfactants with cationic procaine. Electrostatic interactions have a great role in the binding and consequently distribution of Procaine in micelle/water phases. These interactions for anionic surfactant (SDS) are higher than for cationic surfactant (CTAB). Gibbs free energy of binding and distribution of procaine between the bulk water and studied surfactant micelles were calculated.      

Competition between aggregation and hydrolysis in the reaction of arylperfluorooctanoates in micellar solutions

The rate of hydrolysis of phenyl and p-nitrophenyl perfluorooctanoate (2a and 2b) was measured in water and in the presence of different cationic (dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide), anionic (sodium dodecyl sulfate (SDS) and perfluorooctanoate (PFO)) and neutral (Brij-35) surfactants. In water solution, the formation of phenol from 2a and p-nitro phenol from 2b takes place through two kinetic processes, both of which are much slower than the expected rate of hydrolysis for the monomeric compounds in water. The two kinetic processes are attributed to a coupling of the rates of hydrolysis and aggregation of the substrates. In the presence of charged surfactants at concentrations below the respective critical micellar concentration (cmc), two relaxation times are also observed. These are of the same order of magnitude as the substrates alone in the case of SDS, but faster for the cationic surfactants. At some concentration above the cmc, all the surfactants, except for PFO, showed a clean pseudo-first-order behavior attributed to the hydrolysis of the substrate incorporated into the micellar phase. In cationic micelles, the rates for 2a are slower and those for 2b are faster than the value expected for the monomer in water. The difference in behavior is attributed to the location of the substrates in the micellar phase and to the charge distribution in the transition state of the reactions. It is shown that the reactions in the micellar phase are catalyzed by the buffer PO4H(2-)/PO4H2(-). The reactions in SDS micelles are faster than those in water but slower than the estimated value for the monomer in water. The rate of the reactions in the presence of nonionic surfactant has values between those in cationic and anionic surfactants, that is, the rates are k(cationic) > k(nonionic) > k(anionic.) The behavior of 2a and 2b in water and in micellar solutions indicates that the substrates form aggregates in water at a rate that competes with the rate of hydrolysis.