Micelle-forming, liquid-crystalline properties, and catalytic effect of the mixed cetyltrimethylammonium bromide - polyethylene glycol(～9) monoalkanoate(～14) - water micellar system

Article abstract of DOI:10.1023/A:1022166814746

The formation of mixed micelles in the surfactant cetyltrimethylammonium bromide - polyethylene glycol(～9) monoalkanoate(～14) binary system was shown. The stable lyomesophase involving monomers of both surfactants forms in the region of high surfactant concentrations in the temperature interval from 25 to 96°C. In the binary micellar system, the alkaline hydrolysis of O-ethyl-O-p-nitrophenyl chloromethyl phosphonate is accelerated up to 30-fold compared with the reaction in water in the absence of a surfactant. The efficiency of catalysis depends on the molar ratio between both surfactants. The sign of the catalytic effect changes at high surfactant concentrations.

Full text of DOI:10.1023/A:1022166814746

2
176
Russian Chemical Bulletin, International Edition, Vol. 51, No. 12, pp. 2176—2182, December, 2002
Micelleꢀforming, liquidꢀcrystalline properties, and catalytic effect
of the mixed cetyltrimethylammonium bromide—polyethylene glycol(∼ 9)
monoalkanoate(∼ 14)—water micellar system
L. Ya. Zakharova,aꢀ F. G. Valeeva, A. R. Ibragimova, L. A. Kudryavtseva, N. N. Valeev,
a
a
a
b
b
a,b
a
T. L. Didenko, V. I. Kovalenko, and A. I. Konovalov
аA. 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 2) 75 2253. Eꢀmail: lucia@iopc.knc.ru
b
Kazan State Technological University,
6
8 ul. K. Marksa, 420015 Kazan, Russian Federation
The formation of mixed micelles in the surfactant cetyltrimethylammonium bromide—polyꢀ
ethylene glycol(∼ 9) monoalkanoate(∼ 14) binary system was shown. The stable lyomesophase
involving monomers of both surfactants forms in the region of high surfactant concentrations
in the temperature interval from 25 to 96 °С. In the binary micellar system, the alkaline
hydrolysis of ОꢀethylꢀОꢀpꢀnitrophenyl chloromethyl phosphonate is accelerated up to 30ꢀfold
compared with the reaction in water in the absence of a surfactant. The efficiency of catalysis
depends on the molar ratio between both surfactants. The sign of the catalytic effect changes at
high surfactant concentrations.
Key words: mixed micelles, lyomesophase, micellar catalysis, kinetics, hydrolysis,
phosphonates.
Surfactants widely used in industry are, as a rule, mixꢀ
the practical point of view. In this region, the viscosity of
solutions increases, which stimulates their use as thickenꢀ
ers in the production of varnishes, paints, shampoos, etc.
The data obtained in this part of the work were used for
the interpretation of the kinetic experiment. However,
they are also important for the elucidation of the nature of
tures of different detergents. Mixed micellar systems are
of interest from the viewpoint of the theory of solutions
and practical use.1 The properties of mixed solutions
,2
(
critical micelle formation concentration (CMC), aggreꢀ
gation number, solubilizing ability) differ from those for
3
—5
3—7
solutions of individual surfactants.
This difference alꢀ
mixed surfactant solutions.
lows the required parameters to be obtained by the variaꢀ
tion in the composition of the micellar system. In most
cases, mixed systems are better than pure compounds
because the composition of the mixture can be optimized
for each particular case.
In this work, we studied the catalytic effect of mixed
CTAB—С Е micelles in the alkaline hydrolysis of
ОꢀethylꢀОꢀpꢀnitrophenyl chloromethylphosphonate (1)
1
4 9
(Scheme 1).
This work is devoted to the study of the properties of the
mixed cetyltrimethylammonium bromide (CTAB)—polyꢀ
ethylene glycol(∼ 9) monoalkanoate (∼ 14) (С Е )—water
Scheme 1
14 9
system. With this purpose, we studied the aggregating abilꢀ
ity of the system in a wide interval of concentrations. In
the region of low surfactant concentrations (formation of
direct micelles), it was necessary to reveal whether the
surfactants associate in combination (synergistic behavꢀ
ior) or separate micellization occurs and individual surꢀ
factants produce two types of aggregates (antagonistic beꢀ
havior). The region of high surfactant concentrations, in
which liquidꢀcrystalline structures and their precursors
Studies in the field of kinetics and catalysis in mixed
micellar systems are few to date.
8
—12
(
long cylindrical micelles) form, is of special interest from
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2019—2025, December, 2002.
066ꢀ5285/02/5112ꢀ2176 $27.00 © 2002 Plenum Publishing Corporation
1

Mixed micellar system
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002 2177
k/µS cm–1
Experimental
ОꢀEthylꢀОꢀpꢀnitrophenyl chloromethylphosphonate (1) was
synthesized using a previously published procedure. Cetylꢀ
trimethylammonium bromide (Sigma) and an industrial sample
2
3
1
3
1
of С Е were used. The kinetics of hydrolysis was studied specꢀ
14
9
100
trophotometrically on a Specord Мꢀ400 instrument under the
pseudoꢀfirst order conditions by a change in the absorption of
the pꢀnitrophenoxide anion at 400 nm. The apparent rate conꢀ
stants (kapp) were calculated using the weighted leastꢀsquares
method. The temperature observations of the lyotropic mesoꢀ
phase were carried out using a MINꢀ8 polarization microscope
equipped with a Boetius heating stage. The accuracy of temꢀ
perature measurements was ±0.2 °С. Electroconductivity was
measured on a CDMꢀ2ꢀd conductometer (Denmark). The surꢀ
face tension was determined by the ring detachment method
4
5
0
1
4
using a Du Noüy tensometer at 35 °С.
4
–1
1
0
20
30 Csurf•10 /mol L
Fig. 2. Plots of the electroconductivity (k) of mixed
CTAB—С Е micellar solutions at 35 °С and different molar
Results and Discussion
14 9
ratios vs. overall concentration of the surfactant (Csurf): α = 1 (1),
1
Micellization of nonionic surfactants is characterized
by CMC values lower than those of ionic detergents beꢀ
cause the latter make the unfavorable contribution to the
free energy of micellization due to the electrostatic repulꢀ
0
.83 (2), 0.50 (3), and 0.17 (4 ).
aggregates (CMCꢀ1, see Fig. 1), although the tensometric
1
5
5
sion of the head groups. The CMC value for CTAB is
study of micellization found the second inflection correꢀ
–1
0
.85 mmol L–1, and that for С Е is 0.052 mmol L
sponding to CMCꢀ2 in addition to CMCꢀ1.
14 9
(
Fig. 1).
We performed the conductometric and tensometric
studies of aggregation in the mixed CTAB—С Е sysꢀ
The conductometric study of mixed solutions in a wide
interval of surfactant concentrations showed the inflecꢀ
tion in the plots of specific electroconductivity vs. overall
surfactant concentration (Fig. 2). As established previꢀ
14 9
tems. The CMC values were determined by the tensoꢀ
metric method from the inflection point in the plots of
the surface tension vs. overall surfactant concentration at
different molar fractions of the ionic (α ) and nonionic
(
1
6
ously, the CMC values determined conductometrically
and tensometrically can somewhat differ. However, the
surfactant concentrations corresponding to the inflections
in Fig. 2 are higher by an order of magnitude and more
than the CMCꢀ1 values determined tensometrically
(Table 1). Probably, these critical concentrations (see
Fig. 2) should be treated as CMCꢀ2 values. In the systems
1
α2) surfactants for several micellar compositions (see
Fig. 1). The studied concentration interval contains only
one inflection corresponding to the formation of mixed
–
1
γ/dyne cm–2
with α ≥ 0.5, the CMCꢀ2 value is close to 0.001 mol L
1
–
1
and decreases to 0.4—0.5 mmol L only with the further
5
5
4
4
3
5
0
5
0
5
Table 1. The CMCꢀ1 and CMCꢀ2 values of the mixed
CTAB—С Е micellar system determined by measurements of
14 9
the surface tension and electroconductivity at different molar
fractions of the surfactant (α1)
5
α1
CMCꢀ1
CMCꢀ2
4
mol L–1
6
0
0.052
0.055
0.061
0.073
—
0.109
—
0.25
0.85
—
0.4
0.47
0.98
0.90
—
1.07
—
—
3
2
0
0
0
.17
.33
.50
1
1
0–5
10–4
Csurf/mol L–1
0.60
0
0
0
1
.67
.83
.91
Fig. 1. Plots of the surface tension (γ) of mixed CTAB—С Е
4 9
micellar solutions at 25 °С and different molar ratios vs. overall
concentration of the surfactant (Csurf): α1 = 0 (1), 0.17 (2),
1
0
.33 (3), 0.50 (4 ), 0.67 (5), and 0.91 (6 ).

2178
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002
Zakharova et al.
4
–1
С *•10 /mol L
х1
Here x is the molar fraction of the ionic surfactant in
1
0
.9
.8
.7
.6
.5
.4
mixed micelles, which can be calculated using the soluꢀ
tion of the equation
8
0
0
0
0
0
(
5)
7
6
5
4
3
2
1
1
2
3
4
5
by the iteration method.
The mathematical apparatus used in the calculations
4
has been described in detail. The β parameter can be
calculated from the equation
.
(6)
0.3
0.2
0.1
The empirical parameter β takes into account the deꢀ
gree of deviation of the system from the ideal mixture and
the character of interaction of the surfactant monomers
in mixed solutions. The negative value of the β parameter
assumes attraction forces and indicates the synergistic efꢀ
fect related to the involvement of both surfactants in
micellization. The positive values of the β parameter mean
the predomination of repulsion forces between the surꢀ
factant molecules characterizing the antagonistic effect.
Due to this effect, aggregates based on individual surfacꢀ
tants can form in the system. An increase in the absolute
β value indicates a greater deviation of the micellar sysꢀ
tem from the behavior of ideal mixing.
0
0.2
0.4
0.6
0.8
α1
Fig. 3. Plots of the CMC of mixed CTAB—С Е micellar sysꢀ
tems (experimental (1) and calculated values at β = –2.5 (2) and
2.6 (3), for ideal mixing (4 )) vs. molar fraction of CTAB (α1)
14 9
–
and the ratio between the molar fraction of CTAB in a soluꢀ
tion α ) and in micelles (х ) (5 ).
1
1
Analysis of the data presented in Fig. 1 using
Eqs. (1)—(6) allowed the х , х , and β values to be calcuꢀ
lated. As can be seen in Fig. 3, the molar fraction of
increase in the fraction of the nonionic surfactant (see
Table 1).
1
2
Figure 3 presents the dependence of the experimental
CTAB in mixed aggregates (x ) is decreased compared to
1
CMC values for the mixed CTAB—С Е system on the
14
9
its fraction in a solution (α ). This is probably caused by
1
molar fraction of the ionic surfactant (CTAB) and the
the more efficient micelleꢀforming properties of the nonꢀ
ionic surfactant because unfavorable electrostatic interꢀ
actions are absent. It is also seen that the experimental
CMC values do not match the curve corresponding to
the ideal mixing. The β parameters calculated from
Eqs. (1)—(5) are approximately –2.5. The exception is
the micelle composition corresponding to the high CTAB
content (α1 = 0.91), for which β = –2.0 was obtained.
The β values point out to the predomination attraction
forces in mixed aggregates, and the lower β modulus at
α1 = 0.91 can likely be explained by an increase in the
contribution of the Coulomb repulsion of the likely
charged head groups of CTAB with an increase in the
3
CMC values calculated for the case of ideal mixing using
the equation
*
1
/C = α /C + α /C ,
(1)
1
1
2
2
where α and α are the molar fractions of the ionic and
1
2
*
nonionic surfactants, respectively, in a solution; С , С ,
1
and С are the CMC values for the mixed system, ionic
2
surfactant, and nonionic surfactant, respectively.
Different thermodynamic1
7—19
and model
3,4
apꢀ
proaches are known for the description of micellization in
4
mixed systems. The pseudoꢀphase separation model,
which has been checked for many experimental data,5—7,20
is most widely and successfully used in the present time.
In the framework of this approach, to take into account
nonꢀideality of the mixture, the activity coefficients of
surfactants f , f and the parameter of surfactant interacꢀ
*
fraction of the latter in micelles. The С values calculated
in the framework of the theory of regular solutions using
the calculated values of the micelle composition for
β = –2.5 and –2.6 are presented in Fig. 3. The calculated
1
2
*
tion in mixed aggregates β are introduced into Eq. (1)
С values agree well with the experimental values in a wide
interval of surfactant molar ratios.
*
1
/C = α /(f C ) + α /(f C ),
(2)
(3)
(4)
1
1
1
2
2
2
The ability of surfactants to form lyomesophases in
the region of high concentrations is an interesting and
important feature of their behavior in solutions. Accordꢀ
2
f = exp[β(1 – x ) ],
1
1
2
21
f = exp(βx ).
ing to published data, the hexagonal (Н ), cubic (Q ),
2
1
α
α

Mixed micellar system
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002 2179
and lamellar (L ) mesophases form in the CTAB—water
system. The region of the stable state of the hexagonal
phase lies21 in the concentration interval from 40 to
the reaction in water in the absence of a surfactant) due to
the solubilization of the substrate in the micellar pseudoꢀ
phase and simultaneous concentrating of the hydroxide
ions on the positively charged micellar surface. In a miꢀ
cellar solution of the nonionic surfactant С Е , the reacꢀ
α
6
0 wt.% and in the temperature interval from 30 to 200 °С.
The regions of optical anisotropy have also been found for
14 9
2
2,23
aqueous solutions of nonionic surfactants.
We have
tion rate remains unchanged. The kinetic data for the
previously2 shown the formation of the lamellar L phase
4
hydrolysis of 1 in mixed CTAB—С Е micellar systems
β
14 9
(
gel phase) with the melting point ∼ 60 °С (m.p. of the
are presented in Fig. 5 as a dependence of kapp on the
surfactant concentration in the micelles (Csurf) at the unꢀ
changed CTAB : С Е molar ratio. With an increase in
surfactant itself is ∼ 28 °С) in the С Е —water system in
the concentration interval from 45 to 65 wt.%. In this
14 9
14 9
work, the aqueous С Е —CTAB system (α = 0.60) was
the content of the nonionic surfactant to α2 = 0.4, the
kapp value somewhat increases, and the further increase in
α2 results in a smooth decrease in kapp. The quantitative
analysis of the kinetic data was performed using the
pseudoꢀphase model. According to the latter, the deꢀ
pendence of the apparent second order rate constant k´app
14
9
1
studied at different temperatures by polarization microsꢀ
copy. The texture of the studied sample in the temperaꢀ
ture interval from 25 to 96 °С is shown in Fig. 4. The
formation of the stable mesophase in this system is probꢀ
ably associated with the involvement of the surfactants of
both types, because the temperature and concentration
2
5
intervals of lyomesophase formation differ from those for
3
–1
kapp•10 /s
individual solutions.2
1,24
The observation of the sample
using a polarization microscope revealed reproducible
changes in the texture at the temperature close to 60 °С.
This can be attributed to the coexistence at temperatures
below 60 °С of a mixed lyomesophase enriched in indiꢀ
vidual CTAB molecules and a gel phase formed by the
С Е molecules.
3
1
40
20
2
14
9
The dependence of the apparent rate constant for alꢀ
kaline hydrolysis of 1 on the surfactant concentration was
studied in kinetic experiments. In a micellar solution of
CTAB, the reaction is accelerated 20ꢀfold (compared to
3
–1
1
0
20 Сsurf•10 /mol L
3
–1
kapp•10 /s
a
b
120
3
1
00
2
1
8
6
4
2
0
0
0
0
4
5
6
c
d
0
3
–1
1
0
20 Сsurf•10 /mol L
Fig. 5. Plots of the apparent rate constant for alkaline hydrolysis
of 1 (kapp) in mixed CTAB—С Е micellar systems vs. overall
14
9
surfactant concentration at different molar ratios: α1 = 1.0 (1),
.83 (2), 0.67 (3), 0.60 (4), 0.50 (5), and 0.33 (6); insert, simulaꢀ
tion of the apparent rate constant for alkaline hydrolysis of 1
kapp) in a mixed CTAB—С Е micellar system (α = 0.5) using
0
(
14
9
1
Eq. (7) at Сsurf equal to the overall surfactant concentration (1)
and at the CTAB concentration corresponding to the molar
fractions α (2) and х (3). Points are experiment, and lines are
Fig. 4. Texture of a liquidꢀcrystalline mixed С Е —CTAB (1 : 1,
14
9
1
1
mol/mol) solution at 25 (a), 50 (b), 70 (c), and 96 °С (d).
calculation.

2180
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002
Zakharova et al.
(
the first order rate constant divided into the nucleophile
Ψ/mV
0.2
0.4
0.6
0.8
α1
concentration) on Сsurf has the following form:
1
40
.
(7)
1
20
The calculated second order rate constants in aqueous
and micellar phases, k2,w and k2,m, and binding constants
2
of the substrate and nucleophile, K and КOH, are preꢀ
sented in Table 2. Individual micellar solutions of nonꢀ
ionic surfactants have no effect on the reaction kinetics
100
80
S
1
(
see above), and the mixed systems demonstrate a conꢀ
siderable decrease in the catalytic effect with an decrease
in the molar fraction of CTAB. Therefore, different Сsurf
values were used for the simulation of the composition of
micellar aggregates: the overall surfactant concentration,
the stoichiometric concentration of CTAB in a solution
60
calculated from the α value, and the CTAB concentraꢀ
40
1
tion in the micellar pseudoꢀphase calculated using the х1
value. As can be seen from such a simulation for one
–
5.0
–4.5
–4.0
–3.5
loga1
surfactant composition with α = 0.5 (see Fig. 5, insert),
1
Fig. 6. Plots of the surface potential (Ψ) of mixed CTAB—С Е
14 9
the maximum divergence between the experiment and
calculation is observed when formal CTAB concentraꢀ
tions are used (initial concentrations of the surfactant in a
solution, unlike to the true concentrations in the aggreꢀ
gate composition). The best convergence of the calculaꢀ
tion and experiment was obtained when the Сsurf values
equal to the CTAB concentration in the composition
of mixed micelles or the overall concentration of the
surfactant were substituted into Eq. (7), although the
coincidence of the results is better in the latter case.
Perhaps, this confirms that mixed associates formed
by the molecules of both surfactants rather than only
by cationic detergents participate in the hydrolysis caꢀ
talysis.
micelles vs. logarithm of the activity of the CTAB monomer in
the micellar pseudoꢀphase (loga ) (1) and vs. molar fraction of
1
CTAB in micelles (α ) (2).
1
the rate constant in the micellar pseudoꢀphase k2,m inꢀ
creases and the binding constant of both reactants deꢀ
creases. A decrease in the concentrating factor in this
concentration region is mainly caused by a decrease in
the binding constant of the hydroxide ions. As can be seen
in Fig. 6, this is precisely the interval of the α1 values
where the surface potential of micelles decreases substanꢀ
tially in the regions of concentrations higher than CMC,
and further (at α = 0.2—0.6) it changes more smoothly.
1
For analysis of the kinetic data, the surface potential
Despite the compensation character of changing the Fc
and Fm factors, the resulting catalytic effect increases.
The further increase in the fraction of the nonionic surꢀ
factant results in a sharp increase in the efficiency of
binding for both reactants accompanied, however, by a
considerable decrease in k2,m on going from the aqueous
to micellar phase. Superposition of these effects decreases
the efficiency of catalysis with an increase in the С Е
(
Ψ) of mixed micelles was calculated using the Nernst
2
6
correlation between the surface potential and CMC of
the surfactant. As shown previously,2 a similar relation
holds for the mixed systems containing the ionic and
nonionic surfactants
7
d|Ψ|/d(loga ) = 59.16 mV,
(8)
1
14 9
where а is the activity of free monomers of the ionic
content.
1
surfactant in a mixed micellar solution calculated in the
framework of the theory of regular solutions. Figure 6
The increase in kapp with an insignificant decrease in
the molar fraction of CTAB in a solution to α1 = 0.67
additionally confirms that the total decrease in the effiꢀ
ciency of catalysis in the mixed micelles is not a result of a
decrease in the fraction of the CTAB micelles. Taking
into account the data in Table 2, the initial increase in the
rate with a decrease in the molar fraction of the ionic
surfactant is related to the favorable influence of the miꢀ
cellar microenvironment on the transition state of the
reaction. As can be seen in Fig. 3, the composition of
micellar aggregates changes drastically with a decrease in
4
presents a plot of the surface potential vs. activity of the
potentialꢀdetermining CTAB ion and its molar fraction in
a mixed solution calculated using Eq. (8).
Analysis of the main factors responsible for a change
in the rate in micelles, viz., the factor of concentrating
(
(
F ) and the factor of micellar microenvironment (F )
see Note to Table 2), allows some conclusions about a
c
m
change in the rate under conditions of mixed micellization
to be drawn. At a low content of the nonionic surfactant,

Mixed micellar system
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002 2181
Table 2. Results of the quantitative analysis of the kinetic data using Eq. (7) for the CTAB—C E system
14 9
k2,ma
(kapp/k )
KS
KOH
Fcb
Fmb
FcFm
α1
w max
L mol–1
1
0.62
2.9
2.1
0.75
0.20
0.07
20.3
32.4
30
19
14.4
8.2
593
398
494
600
1282
1839
69
127.5
36.7
49.8
100
276
464
0.16
0.76
0.54
0.19
0.052
0.018
20.1
28.1
27.2
19.0
14.2
8.4
0
0
0
0
0
.83
15.8
21.9
50
149
265
.67
.60
.50
.33
a
b
k2,w = 4.0 L mol–1 s–1
.
Calculated using the equation
.
The right part represents the maximum acceleration of the reaction equal to the ratio of the apparent rate
constant (kapp) to the pseudoꢀfirst order rate constant in water (k ). The first factor in the right part
w
expresses the influence of the micellar microenvironment on the reactivity (F ), and the second factor
m
reflects the effect of concentrating of the reactants in micelles (F ).
c
3
–1
2
–1
the molar fraction of CTAB in a solution to 0.67 The
subsequent sharp decrease in k2,m (see Table 2) at low
α1 values (during this, the composition of micelles changes
slightly, see Fig. 3) is not likely related to a change in the
micropolarity. We can assume that the entropy factor is a
kapp•10 /s
0.5
1.0
1.5
2.0 Сsurf•10 /mol L
1
40
2
reason for a decrease in the reactivity at low α (similarly
1
2
8
120
to that observed previously ).
The influence of the nature of nanoparticles formed in
a mixed micellar system is poorly studied. In this work,
the kinetics of alkaline hydrolysis of 1 was studied at
high surfactant concentrations (the region of formation
of lyomesophases or preceding nanostructures) at an
unchanged content of one of the detergents. In the
studied region of surfactant concentrations, anisotropy
3
1
00
80
6
4
0
0
was not observed by polarization microscopy. However,
it is known1
5,29
that at high concentrations of ionic
and nonionic surfactants the sphere—cylinder micelꢀ
lar transition occurs to form long wormꢀlike micelles,
whose interaction produces a threeꢀdimensional spatial
network.
1
0
.1
0.2
0.3
0.4 Сsurf/mol L–1
The plots of kapp vs. concentrations of the nonionic
surfactant and CTAB are presented in Fig. 7. At a conꢀ
stant CTAB concentration, the apparent rate constant
and catalytic effect decrease smoothly to transform into
Fig. 7. Apparent rate constant for alkaline hydrolysis of 1 (kapp
in mixed CTAB—С Е micellar systems as a function of the
concentration of the nonionic surfactant at the unchanged CTAB
concentration equal to 0.003 mol L– (1) and of the CTAB
concentration at the unchanged С Е concentration equal to
)
1
4 9
1
–
1
the inhibition of the process at [С Е ] = 0.2 mol L
.
1
4 9
14 9
The kapp—Csurf kinetic plot at an unchanged content of
the nonionic surfactant shows that at the С Е concenꢀ
–1
–1
0
.15 (2) and 0.3 mol L (3); 25 °С, 0.1 mol L NaOH.
1
4 9
–
1
tration equal to 0.15 mol L the hydrolysis of 1 is cataꢀ
lyzed only, whereas at the constant concentration of С Е
(
30ꢀfold accelation of alkaline hydrolysis of OꢀethylꢀOꢀ
pꢀnitrophenyl chloromethyl phosphonate.
1
4 9
0.3 mol L–1) inhibition is replaced by catalysis with an
increase in the CTAB concentration. These data agree
with the earlier30,31 conclusions about the influence of
the properties of organized solutions on their catalytic
effect. The micellar system under study shows up to
Thus, the study of the micelleꢀforming properties of
the mixed cetyltrimethylammonium bromide—polyꢀ
ethylene glycol(∼ 9) monoalkanoate (∼ 14) micellar system
by measurements of the surface tension and electroꢀ

2182
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Received December 29, 2001;
in revised form July 23, 2002