Systems based on nonionic amphiphilic compounds: Aggregation and catalytic properties

Article abstract of DOI:10.1007/s11172-010-0162-8

The micellization properties, solubilization capability, and catalytic effect of conventional nonionic surfactants and amphiphilic compounds of oligomeric (Tyloxapol) and polymeric (Synperonic F-68, Pluronic F-127) structure were compared. The systems studied demonstrate a marked catalytic effect toward basic hydrolysis of p-nitrophenyl laurate, which exceeds the effect of aqueous alkali solutions by two orders of magnitude. Correlations between the solubilization capacity of aggregates and their catalytic effect were observed. The maximum efficiency was found for the Tyloxapol solution. The synergetic enhancement of the catalytic effect was observed for the mixed Tyloxapol-cetyltrimethylammonium bromide systems in the presence of small amounts of cationic surfactant

Full text of DOI:10.1007/s11172-010-0162-8

784
Russian Chemical Bulletin, International Edition, Vol. 59, No. 4, pp. 784—789, April, 2010
Systems based on nonionic amphiphilic compounds:
aggregation and catalytic properties
Yu. R. Ablakova, A. B. Mirgorodskaya, L. Ya. Zakharova, and F. G. Valeeva
A. E. Arbuzov Institute of Organic and Physical Chemistry,
Kazan Research Center of the Russian Academy of Sciences,
8
ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843) 273 2253. Eꢀmail: mirgorod@iopc.knc.ru
The micellization properties, solubilization capability, and catalytic effect of conventional
nonionic surfactants and amphiphilic compounds of oligomeric (Tyloxapol) and polymeric
(
Synperonic Fꢀ68, Pluronic Fꢀ127) structure were compared. The systems studied demonstrate
a marked catalytic effect toward basic hydrolysis of pꢀnitrophenyl laurate, which exceeds the
effect of aqueous alkali solutions by two orders of magnitude. Correlations between the solubiliꢀ
zation capacity of aggregates and their catalytic effect were observed. The maximum efficiency
was found for the Tyloxapol solution. The synergetic enhancement of the catalytic effect was
observed for the mixed Tyloxapolꢀcetyltrimethylammonium bromide systems in the presence
of small amounts of cationic surfactant.
Key words: nonionic surfactants, cationic surfactants, block copolymers, aggregation,
pꢀnitrophenyl laurate, solubilizaton, hydrolysis, kinetics.
Amphiphilic compounds including surfactants and
The present work is devoted to the study of aggregation
of biocompatible amphiphilic nonionic compounds posꢀ
sessing the surface activity, to estimation of their solubilizaꢀ
tion ability toward biologically active compounds, and to
control of the reactivity of the latter. Particular attention
is paid to the study of aggregation and catalytic activity of
the mixed systems based on CTAB and Tyloxapol (nonꢀ
ionic amphiphile with oligomeric structure). Mixed sysꢀ
tems based on surfactants are widely used in modern techꢀ
polymers are widely used in gene therapy for transportaꢀ
tion of medicines and as the catalysts (nanoreactors) simꢀ
1
—4
ulating the basic factors of catalytic action of enzymes.
Specific features of chemical and biochemical processes
occurring in the systems based on surfactants arise from the
nanoscale sizes of the reaction zone and from the develꢀ
oped area of the interface layer, which determine the beꢀ
havior of reactants.5 Structural variations in the subꢀ
stances forming the interface, as well as directed variation
of the contributions of electrostatic, hydrophobic, and speꢀ
cific interactions between the surface and the reactants
allow one to control the rates of chemical transformaꢀ
tions. Mixed solutions of amphiphilic compounds are
promising for controllable variation of the surface properꢀ
ties of aggregates. Previously,9—12 we have shown that
modification of micellar solutions of nonionic surfactants
by ionic surfactant additives can be a tool for target conꢀ
trol of the rates of ionꢀmolecular reactions due to the
change in the microscopic properties of the interface, such as
the surface potential, micropolarity, etc. In particular, a synꢀ
ergetic effect in the micelleꢀforming and catalytic properꢀ
ties of the systems based on cetyltrimethylammonium broꢀ
mide (CTAB) and nonionic surfactants TritonꢀXꢀ100 and
—8
1
3
nologies; therefore, information on the properties of such
systems is topical. The mixed systems based on Tyloxapol
have not been studied as yet. Since Tyloxapol has oligoꢀ
meric structure and occupies a position between surꢀ
factants and polymers, information on this system can
be of very importance for understanding the mechanism
of selfꢀorganization in mixed systems based on monomerꢀ
ic and highꢀmolecular amphiphiles. The catalytic effect of
binary surfactant solutions and surfactant—polymer sysꢀ
1
4—18
tems is poorly studied;
therefore, it is also of special
interest. In addition, data on the regularities of changes in
the reactivity in organized media can be used as additional
tool for exploration of the properties of these systems (see,
for example, Ref. 19).
In order to estimate the properties of the solution of
nonꢀclassical amphiphile Tyloxapol, we compared its agꢀ
gregation ability with those of traditional nonionic surfacꢀ
tants polyoxyethylene(10)—monooleic ether (Brijꢀ97),
polyoxyethylene(23)—monododecyl ether (Brijꢀ35), polyꢀ
oxyethylene(10)—monoꢀ4ꢀisooctylphenyl ether (Tritonꢀ
9
11
Brijꢀ97 was revealed. It was shown that the addition of
CTAB to a TritonꢀXꢀ100 solution results in the formation
of mixed aggregates in which an increase in the rate of
basic hydrolysis of carboxylic acid esters and the acids
containing fourꢀcoordinate phosphorus is observed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 768—773, April, 2010.
066ꢀ5285/10/5904ꢀ0784 © 2010 Springer Science+Business Media, Inc.
1

Systems based on nonionic amphiphilic compounds Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
785
Xꢀ100), as well as with those of macromolecular amꢀ
phiphiles (poly(ethylene oxide)—poly(propylene oxide)
block copolymers).
pꢀNitrophenyl laurate (PNPL) was used as a probe for
the study of the solubilization properties and catalytic acꢀ
tivity of micellar systems. A general scheme of the reacꢀ
tion studied is as follows:
mined using the expression log(A∞ – Aτ) = –0.434kappτ + const,
where A and A are the optical densities of the solutions at the
instant τ and after completion of the reaction. The kapp values
were calculated by the least squares method.
τ
∞
The kinetic data were analyzed using the equation of the
pseudoꢀphase model5 for micellar catalysis
,6
kapp = (k K C + k )/(1 + K C),
(1)
m
S
0
S
–
where k and km (s–1) are the firstꢀorder rate constants in water
С11Н23С(О)ОС Н NO + 2 ОН
6
4
2
0
–
1
and in the micellar phase, respectively, K (L mol ) is the conꢀ
S
–
–
С11Н23С(О)О + ОС Н NO + Н О.
6
4
2
2
stant of substrate binding, C is the total surfactant concentration
minus the critical micelle concentration (CMC).
Experimental
The data on the micellar aggregate sizes were obtained by
the dynamic light scattering on a Photocor Complex spectroꢀ
photometer (He—Neꢀlaser, 633 nm). The details of the experiꢀ
mental design were described in Ref. 20. The measurement error
did not exceed 4%.
The concentration of bromine ions in mixed surfactant sysꢀ
tems was determined by a bromineꢀselective electrode on
a Iꢀ160MI ionꢀmeter. The electrode potential (ΔE) and the broꢀ
mideꢀion activity are related by the Nernst equation:
Commercially available surfactants (TritonꢀXꢀ100, Brijꢀ35,
Brijꢀ97, CTAB) and block copolymers (Synperonic Fꢀ68, Pluꢀ
ronic Fꢀ127, Tyloxapol) (Sigma), containing ~99% of the main
substance were used. The molar concentrations (mol L–1) of
conventional nonionic surfactants are used as they were; the
molar concentrations of Tyloxapol and block copolymers are
given per monomer unit.
The solubilization of the micellar systems toward PNPL was
determined according to the procedure involving the preparaꢀ
tion of saturated PNPL solution, subsequent basic hydrolysis,
and spectrophotometrical determination of the content of
pꢀnitrophenol. For this purpose, the sample of freshly recrystalꢀ
lized PNPL was flushed with the solution of the surfactant studꢀ
ied and then vigorously stirred for 6 h at constant temperature.
Then, the undissolved PNPL was separated; an aliquot was taken
from the saturated solution, and a known amount of concentratꢀ
ed NaOH solution (2 mol L–1) was added to the aliquot. The
completeness of PNPL hydrolysis was confirmed by spectrophoꢀ
tometry until a constant optical density (A) at 400 nm (the abꢀ
sorption of pꢀnitrophenolateꢀanion). The concentration of the
ΔE = –(RT/F)log(a ) + const,
(2)
Br
where F is the Faraday constant. Theoretically, the slope of the
–1
ΔE — log(a ) dependence is 59.2 mV equiv. at 25 °C. The
Br
potential was measured during a gradual increase in the surfacꢀ
tant concentration; the extent of counterꢀion binding was calcuꢀ
lated as the ratio of the concentration of bound bromide ions and
the total surfactant concentration in the micelle.
The surface tension was measured by the Du Nouy ring deꢀ
tachment method.
Results and Discussion
pꢀnitrophenolate (CPhO
tially solubilized PNPL was determined using the expression
= εAL, where L is the width of the absorbing layer and ε is
–
) equal to the concentration of the iniꢀ
Previously,8—12 we studied aggregation of nonionic surꢀ
C
PhO–
factants Brijꢀ97, Brijꢀ35, and TritonꢀXꢀ100 both in indiꢀ
vidual solutions and in mixed systems with ionic surfacꢀ
tants by tensiometry and conductometry. The CMC of
surfactants depend on their hydrophilicꢀlipophilic balance
and decreases in the series Brijꢀ35, TritonꢀXꢀ100, Brijꢀ97:
the extinction coefficient of pꢀnitrophenolate ion (18000).
The kinetics of basic hydrolysis of PNPL was studied by
spectrophotometry on a Specord UV—Vis instrument at 25 °C. The
course of the reaction was monitored by the change in the optical
density of the solutions at 400 nm. The initial substrate concenꢀ
tration was 5•10–5 mol L , the degree of conversion was >90%.
The observed pseudofirst order rate constants (kapp) were deterꢀ
–
1
–1
0.31, 0.2, and 0.017 mmol L , respectively. At concenꢀ
trations exceeding the CMC, micellar aggregates with

786
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
Ablakova et al.
a mean hydrodynamic radius of 4.5—5.0 nm are formed in
the solutions. The surface tension isotherms for the synꢀ
thetic amphiphiles Tyloxapol and Synperonic Fꢀ68, which
are structurally similar to nonionic surfactants, are shown
in Fig. 1. The CMC and the effective sizes of aggregates
for Tyloxapol are nearly the same as those of TritonꢀXꢀ
systems due to the oligomeric structure of Tyloxapol. In
this case, the first breakpoint Ccr in the isotherms (see
1
Fig. 2) can be attributed to the critical concentration of
aggregation, characterizing the beginning of mixed aggreꢀ
2
gation in the solution, while the second breakpoint Ccr
can be attributed to the saturation concentration of the
oligomeric chain by micelles. At higher concentrations,
free surfactant micelles are formed in the solution.
1
00. According to tensiometry data, micelle formation
was not observed in solutions of the Synperonic Fꢀ68 block
copolymer in the studied interval of concentrations, probꢀ
ably, due to its high hydrophilicity. The same results were
obtained for Pluoronic Fꢀ127.
1
The Ccr values are nearly the same for all α values
–
1
studied (~0.1 mmol L ) and are below the CMC of both
amphiphiles. Probably, this can be considered as indirect
confirmation of the mixed aggregation in the system. The
One could expect that the aggregation behavior in the
system Tyloxapol—CTAB is analogous to that of a binary
system of surfactants or of a surfactant—polymer system,
because Tyloxapol, being an amphiplile, has oligoꢀ
meric structure. The tensiometry data for the mixed
systems Tyloxapol—CTAB at different mole fractions of
CTAB (α) are demonstrated in Fig. 2. In all cases, the
surface tension isotherms have two breakpoints. This charꢀ
acter of tensiometric curves is typical of surfactant—polyꢀ
mer systems,21 whereas for the binary surfactant solutions
the shapes of the surface tension isotherms of individual
and mixed solutions are the same and exhibit one breakꢀ
point at the CMC. Probably, the character of Tyloxapol
aggregation in mixed solutions with conventional surfacꢀ
tants is similar to that observed in surfactant—polymer
2
Ccr values decrease with an increase in the CTAB fracꢀ
2
–1
tion in the system (Ccr = 1.15, 1.07, and 0.17 mmol L
at α = 0.3, 0.5, and 0.7, respectively), which suggests the
narrowing of the interval of mixed aggregation with the
increase in the fraction of the cationic surfactant.
We performed a potentiometric study of the mixed
systems Tyloxapol—CTAB with the use of bromineꢀselecꢀ
tive electrodes. For all Tyloxapol : CTAB ratios up to
a particular surfactant concentration, the dependence of ΔE
on logC is linear with the slope equal to 59±5 mV equiv.–
(see Fig. 3, inset, as an example). The concentration corꢀ
1
2
responding to the change in the slope equals C . This
cr
2
fact, as well as the proximity of the Ccr value to the CMC
of individual CTAB solutions, poorly agrees with the asꢀ
sumption of the formation of mixed aggregates in the sysꢀ
tem or suggests a high extent of dissociation of CTAB
γ/mN m–1
0.0001
0.001 C/mol L–1
6
5
0
5
0
5
0
5
γ/mN m–1
6
5
5
4
4
3
6
6
5
5
4
5
0
5
0
5
α = 0.3
α = 0.5
α = 0.7
2
1
0
.0001 0.001 0.01
0.1
1
C/mol L–1
0
.00001
0.0001
0.001
0.01 Ctot/mol L–1
Fig. 1. Surface tension (γ) isotherms of aqueous solutions of
Tyloxapol (1), and Synperonic Fꢀ68 (2) (amphiphile concentraꢀ
tions are given per mole unit); 25 °C. Herein and in Fig. 2 logaꢀ
rithmic abscissa axis is shown.
Fig. 2. Surface tension isotherms of aqueous Tyloxapol—CTAB
solutions at different component ratio; 25 °C; Ctot is the total
concentration of amphiphiles.

Systems based on nonionic amphiphilic compounds Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
787
β (%)
00
Table 1). They give evidence that block copolymers only
slightly promote the increase in solubility of PNPL; this
is in agreement with the results shown in Fig. 1, which
confirm the lack of micelle formation in the studied region
of amphiphile concentrations. Tyloxapol increases the solꢀ
ubility of the ester by an order of magnitude. One can
assume that the ability of the systems studied to dissolve
the hydrophobic substrate is determined by the correlation
of the contribution of two types of interactions, viz.,
the solubilization mechanism of PNPL binding, which
assumes the formation of mixed micelles, and the sorption
mechanism on the polymer surface. Estimation of the hyꢀ
drolytic stability of the guest in aqueous solutions of
amphiphilic compounds at concentrations of 0.02 mol L–
was performed; as a result, the data on the rate of basic
hydrolysis of PNPL were obtained (see Table 1).
1
9
8
7
6
5
4
3
2
1
0
α = 0.3
α = 0.5
α = 0.7
0
0
0
0
0
0
0
0
ΔE/mV
20
1
α = 0.7
8
0
1
40
0
As a rule, nonionic surfactants have little effect on the
12
rate of ionꢀmolecular reactions. Previously, a slight reꢀ
tardation of basic hydrolysis of esters in solutions of nonꢀ
ionic amphiphiles was demonstrated. In this work, we
observed acceleration of the hydrolysis of PNPL; the catꢀ
alytic activity of the systems studied changes in parallel to
their solubilization ability (see Table 1). The maximum
effect is observed in the Tyloxapol solutions, namely,
a 14ꢀfold increase in the solubility of PNPL and a 145ꢀfold
acceleration of its hydrolysis. It is known that PNPL is
prone to selfꢀassociation, which is the reason for its lower
reactivity (compared to nonꢀmicelleꢀforming homologs)
in the nucleophilic substitution in the absence of surfacꢀ
tants. Probably, in micellar solutions the structure of these
associates is changed and mixed micelles possessing highꢀ
er reactivity appear.
In order to obtain systematic data on the catalytic efꢀ
fect of supramolecular systems, the kinetics of the reacꢀ
tions at different surfactant concentrations was studied
(see Fig. 4) with the subsequent quantitative analysis of
the concentration dependences of the observed rate conꢀ
stant for PNPL hydrolysis. The character of the depenꢀ
dences showing plateau regions at high concentration
0
.0001 0.001 Ctot/mol L–1
Ctot/mol L–1
0
0.01 0.02 0.03 0.04
Fig. 3. The dependence of the binding extent of bromide ions (β)
in the system Tyloxapol—CTAB on the total concentration (Ctot
of amphiphiles at different component ratio; 25 °C. Inset: the
dependence of the electrode potential (ΔЕ) on the total concenꢀ
tration of amphiphiles at the CTAB : Tyloxapol ratio equal to
)
0
.7; 25 °C; logarithmic abscissa axis is shown.
micelles bound to Tyloxapol. The binding degree of the
counter ions depends on the composition of micellar sysꢀ
tems (Fig. 3); it increases with the increase in the CTAB
fraction and approaches a value of 1.0 in the plateau reꢀ
gion at high amphiphile concentrations.
The data characterizing the solubilization action of
the systems studied were obtained by spectrophotometry
at the amphiphile concentration of 0.02 mol L–1 (see
Table 1. Solubilization of PNPL and the observed rate constant for basic hydrolysis of PNPL in water, in
solutions of nonionic surfactants and block copolymers
4
kapp/s–1
(0.05 М NaOH)
System
[PNPL]m•10–
[PNPL] /[PNPL]
kapp/k0
m
0
/
mol L–1
Water
TritonꢀXꢀ100
Brijꢀ35
0.12
3.35
0.42
0.82
0.17
0.14
1.79
1
28
0.0002
0.010
0.008
1
50
40
3.5
6.8
1.4
1.2
15
Brijꢀ97
0.016
80
Pluronic Fꢀ127
Synperonic Fꢀ68
Tyloxapol
0.00078
0.00074
0.029
3.9
3.7
145
Note. [PNPL]m and [PNPL] are the maximum concentrations of PNPL, which are achieved on dissoluꢀ
0
–1
tion in solutions of amphiphiles and water, respectively. The amphiphile concentration is 0.02 mol L , 25 °C.

788
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
Ablakova et al.
kapp/s–1
PNPL when it is incorporated into aggregates based on
this oligomer.
4
Mixed systems with cationic surfactant were studied
for Tyloxapol, which is the most efficient catalyst (see
Fig. 3). It was assumed that the positive charge on the
surface of micelles can lead to additional concentration of
hydroxide ions in the micelles and enhancement of the
catalytic action of Tyloxapol. The results of kinetic studies
of basic hydrolysis of laurate in the system Tyloxaꢀ
pol—CTAB at different component ratios are demonstratꢀ
ed in Fig. 5. They show that the catalytic effect
of this system considerably differs from that obtained for
0
.015
1
2
0
0
0
0
.012
.009
.006
.003
1
0,11
the previously studied
binary solutions CTAB—Triꢀ
tonꢀXꢀ100. In the CTAB—TritonꢀXꢀ100 system a moꢀ
notonous increase in the rate constant with an increase in
the mole fraction of the cationic surfactant was observed.
This agrees with the concept of formation of combined
aggregates whose surface potential varies depending on
the component ratio and is the rateꢀdetermining factor. For
the binary system Tyloxapol—CTAB, the introduction of
small amounts of the cationic surfactant (α = 0.1) results
in fivefold increase in the rate of PNPL basic hydrolysis;
however, even at α = 0.2 the effect of CTAB introducꢀ
tion virtually reaches its limiting value and increases by
6—10 times on subsequent increase in the cationic surfacꢀ
3
0
.002 0.004 0.006 0.008 C/mol L–1
Fig. 4. The dependence of the observed rate constant (kapp) for
basic hydrolysis of PNPL on the concentration (C) of nonionic
surfactants: Brijꢀ97 (1), TritonꢀXꢀ100 (2), Brijꢀ35 (3), Tylꢀ
oxapol (4); 0.05 М NaOH, 25 °C.
kapp/s–1
0
0
0
0
.08
.06
.04
.02
allows one to apply the pseudophase model (1) to the
kinetic data obtained and to calculate the constants of
4
5
substrate binding (K ) and the rate constants in the micelꢀ
6
S
lar pseudoꢀphase (k ) (Table 2). It is seen from the calculaꢀ
m
tions that for nonionic surfactants the increase in the bindꢀ
ing constant is accompanied by the increase in the rate of
–
1
7
hydrolysis. Thus, for Brijꢀ35 one gets K = 370 L mol
S
and acceleration (compared with the rate constant in
the absence of surfactants) by 45 times. For Brijꢀ97,
3
2
–
1
one gets K = 1100 L mol and acceleration by ~70 times.
S
The CMC value resulted from the kinetic and tensioꢀ
metric studies are close. Much higher acceleration in
the case of Tyloxapol (up to 150 times), is probably
due to favorable changes in the microenvironment of
1
Table 2. Results of quantitative analysis of kinetic data for basic
hydrolysis of PNPL in solutions of nonionic surfactants and Tylꢀ
oxapol using Eq. (1) (0.05 М NaOH, 25 °C)
–1
Surfactant
k /s
KS
L mol
СМС
/mol L
k /k
m
m
0
–
1
–1
0.002 0.004 0.006 0.008
C/mol L–1
/
Fig. 5. The dependence of the observed rate constant for basic
hydrolysis of PNPL in the system Tyloxapol—CTAB on the total
concentration of amphiphiles at different mole fraction of CTAB:
α = 0 (1), 0.1 (2), 0.2 (3), 0.3 (4), 0.5 (5), 0.7 (6), 1 (7); 0.05 М
NaOH, 25 °C.
TritonꢀXꢀ100
Brijꢀ35
Brijꢀ97
0.01
890
370
1100
140
0.00013
0.00033
0.00005
0.0009
50
45
70
0.009
0.014
0.030
Tyloxapol
150

Systems based on nonionic amphiphilic compounds Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
789
tant fraction to 1.0 (see Fig. 5). Probably, this is due to the
observed narrowing of the region of existence of mixed
aggregates, and also to stronger binding of counterions,
resulting in the decrease in the surface potential with the
increase of the CTAB fraction in the system. It should be
noted that at α = 0.3—0.7 the observed rate constant is
higher than that in the individual Tyloxapol and CTAB
systems. The demonstrated kinetic data give additional
evidence of the formation of mixed aggregates, which cause
the observed synergetic catalytic effect.
5. I. V. Berezin, K. Martinek, A. K. Yatsimirsky, Usp. Khim.,
1
4
973, 42, 1729 [Russ. Chem. Rev. (Engl. Transl.), 1973,
2, 1343].
6
7
. C. A. Bunton, G. Savelli, Adv. Phys. Chem., 1986, 22, 213.
. L. S. Romsted, Surfactants in Solution, Ed. K. L. Mittal,
Plenum Press, New York—London, 1984, 4, 1015.
. L. Ya. Zakharova, A. B. Mirgorodskaya, E. P. Zhil´tsova,
L. A. Kudryavtseva, A. I. Konovalov, Izv. Akad. Nauk,
Ser. Khim., 2004, 1331 [Russ. Chem. Bull., Int. Ed., 2004,
53, 1385].
8
9. L. Zakharova, F. Valeeva, A. Zakharov, A. Ibragimova,
L. Kudryavtseva, H. Harlampidi, J.Colloid Interface Sci.,
Thus, we obtained and characterized micellar systems
based on nonionic amphiphiles with oligomeric (Tylꢀ
oxapol) and polymeric (Synperonic Fꢀ68, Pluronic Fꢀ127)
structure, as well as previously not studied mixed systems
Tyloxapol—CTAB. The CMCs, aggregate sizes, and the
extent of counterion binding of mixed systems were estabꢀ
lished. The micelleꢀforming properties, solubilization
capability, and catalytic effect of the classical surfactants
and amphiphilic highꢀmolecular compounds were comꢀ
pared. In contrast to the usually observed slowing down
or the lack of the influence of nonionic micelles on
the rate of nucleophilic substitution, it was shown that the
systems studied have a pronounced catalytic effect on the
basic hydrolysis of PNPL, which exceeds two orders of
magnitude. A correlation between the solubilization abiliꢀ
ty of aggregates based on nonionic amphiphiles and their
catalytic effect was revealed for the first time. The highest
efficiency was found for the Tyloxapol solution. For the
mixed systems Tyloxapol—CTAB, synergetic enhanceꢀ
ment of the catalytic effect upon addition of small amounts
of CTAB was established.
2
003, 263, 597.
1
1
1
1
0. L. Ya. Zakharova, F. G. Valeeva, A. V. Zakharov, A. B.
Mirgorodskaya, L. A. Kudryavtseva, A. I. Konovalov, Kinet.
Katal., 2007, 48, 221 [Kinet. Katal. (Engl. Transl.), 2007,
4
8, 221].
1. A. B. Mirgorodskaya, L. Ya. Zakharova, F. G. Valeeva, A. V.
Zakharov, L. Z. Rizvanova, L. A. Kudryavtseva, Kh. E.
Kharlampidi, A. I. Konovalov, Izv. Akad. Nauk, Ser. Khim.,
2007, 1933 [Russ. Chem. Bull., Int. Ed., 2007, 56, 2000].
2. L. Ya. Zakharova, F. G. Valeeva, A. R. Ibragimova, V. M.
Zakharov, L. A. Kudryavtseva, Yu. G. Elistratova, A. R.
Mustafina, A. I. Konovalov, Kolloidn. Zh., 2007, 766 [Colloid J.
(
Engl. Transl.), 2007, 69, 718].
3. B. Jonsson, B. Lindman, K. Holmberg, B. Kronberg, Surꢀ
factants and Polymers in Aqueous Solution, 2nd ed., John Wilꢀ
ley and Sons, Chichester, England, 2003, p. 545.
14. C. A. Bunton, S. Wright, P. M. Holland, F. Nome, Langꢀ
muir, 1993, 9, 117.
15. C. R. A. Bertoncini, M. F. S. Neves, F. Nome, C. A. Bunꢀ
ton, Langmuir, 1993, 9, 1274.
6. V. L. A. Frescura, D. M. O. Marconi, D. Zanette, F. Nome,
A. Blasko, C. A. Bunton, J. Phys. Chem., 1995, 99, 11494.
7. D. M. Davies, S. J. Foggo, J. Chem. Soc., Perkin Trans. 2,
1
1
1
998, 247.
18. E. Iglesias, L. Montenegro, Phys. Chem. Chem. Phys., 1999,
, 4865.
References
1
1
2
9. L. S. Romsted, Langmuir, 2007, 23, 414.
1
. C. L. Gebhart, S. Sriadibhatla, S. Vinogradov, P. Lemieux,
V. Alakhov, A. V. Kabanov, Bioconjugate Chem., 2002,
0. L. Zakharova, A. Ibragimova, F. Valeeva, A. Zakharov,
А. Mustafina, L. Kudryavtseva, H. Harlampidi, А. Konovꢀ
alov, Langmuir, 2007, 23, 3214.
1
3, 937.
. V. A. Sethuraman, K. Na, Y. H. Bae, Biomacromolecules,
006, 7, 64.
. T. Dwars, E. Paetzold, G. Oehme, Angew. Chem., Int. Ed,.
005, 44, 7174.
2
3
4
2
1. J. C. Brackman, J. B. F. N. Engberts, Chem. Soc. Rev., 1993,
2
2
2, 85.
2
. M. N. Khan, Micellar Catalysis, in Surfactant Science Series,
CRC Press, Boca Raton, FL, 2006, 133, p. 482.
Received November 25, 2008;
in revised form August 28, 2009