Supramolecular systems based on poly(ethyleneimines) and calix[4]resorcinarenes with alkylphosphonate fragments. Aggregation and catalytic activity

Article abstract of DOI:10.1007/s11172-007-0145-6

Aggregation in poly(ethylenimine)-calix[4]resorcinarene-water-DMF systems was studied by the methods of conductometry and dynamic light scattering. The sizes (radii) of the aggregates formed and the critical micelle concentrations were determined. The cat

Full text of DOI:10.1007/s11172-007-0145-6

Russian Chemical Bulletin, International Edition, Vol. 56, No. 5, pp. 959—966, May, 2007
959
Supramolecular systems based on poly(ethyleneimines)
and calix[4]resorcinarenes with alkylphosphonate fragments.
Aggregation and catalytic activity
T. N. Pashirova, S. S. Lukashenko, E. M. Kosacheva,ꢀ L. Z. Rizvanova, G. A. Gainanova,
I. R. Knyazeva, A. R. Burilov, L. A. Kudryavtseva, and A. I. Konovalov
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 2) 73 2253. Eꢀmail: kosacheva@iopc.knc.ru
Aggregation in poly(ethylenimine)—calix[4]resorcinarene—water—DMF systems was
studied by the methods of conductometry and dynamic light scattering. The sizes (radii) of the
aggregates formed and the critical micelle concentrations were determined. The catalytic
activity for these systems in the hydrolisys of phosphorus acid esters was shown.
Key words: poly(ethyleneimines), calix[4]resorcinarenes, aggregation, catalysis, phosphoꢀ
rus acid esters, hydrolysis, phosphonates.
Many publications are devoted to investigation of the
properties of mixed solutions of polymers (polyelectroꢀ
lytes) with amphiphilic compounds, for example, with
ionogenic surfactants (Surf).1—4 In these systems, comꢀ
bined associates are formed due to noncovalent interacꢀ
tions (electrostatic, hydrophobic, hydrogen, and others)
of the amphiphile with the polymer macromolecule. The
study of the properties of mixed compositions makes it
possible to model and understand the nature of intermoꢀ
lecular interactions of biopolymers (proteins) with lipids
in biomembranes and the mechanisms of their functionꢀ
R = Et (1), Pr (2)
ing.5—7 At the same time, nanostructured polymeric sysꢀ
tems are of practical significance, because they are used as
flocculants, mediators of biologically active substances,
nanoreactors for various chemical processes, etc. Aggreꢀ
gates of different shape and size are formed and structural
and phase transformations occur due to the selection of
the structures of amphiphiles and polymers (polyelectroꢀ
lytes) and their ratio and concentration in mixed systems,
which determine their specific properties, including the
catalytic ones.
In the present work, polyelectrolyte—calix[4]resorcinꢀ
arene—water—DMF (30 vol.%) compositions were studꢀ
ied as nanoreactors of hydrolysis of phosphorus acid esꢀ
ters. Phosphorylated calix[4]resorcinarenes (PCR) 1 and 2
containing the alkylphosphonate fragments at the lower
rim of the molecule in the cone conformation were used.
Calixarenes are macrocyclic compounds synthesized
by the condensation of phenols and aldehydes of different
structure.8 They contain hydrophobic cavities that allow
them to act as receptors binding molecules with certain
sizes and polarity to form host—guest complexes (moꢀ
lecular recognition).
Depending on the conformation, amphiphilic
calix[n]arenes form aggregates of different structure of the
type of micelles or lamellas.9—12 The critical micelle conꢀ
centrations (CMC) depend on the length of the hydroꢀ
carbon radicals and the number of aromatic rings (n) in
a calixarenes molecule. It is known13 that functionalized
calixarenes, similarly to natural detergents, can incorpoꢀ
rate into micelles and bilayers formed by other amphiꢀ
philes. It has previously been found14 by conductometry
that PCR aggregate in a water—DMF (30 vol.%) medium
at high pH (PCR : NaOH = 1 : 8) with CMC = 4•10–4
mol L–1. We showed by tensiometry that the PCR under
study at neutral pH values possess surface activity affected
by the hydrophobicity of the R radical in calixarene
(CMC = 1.3•10–4 and 8•10–5 mol L–1 for PCR 1 and 2,
respectively) (Fig. 1). The radii of the PCR aggregates
(4•10–4 mol L–1) determined by the light scattering
method are 100—103 nm.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 924—931, May, 2007.
1066ꢀ5285/07/5605ꢀ0959 © 2007 Springer Science+Business Media, Inc.

960
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
Pashirova et al.
σ/mN m–1
Data on the electrical conductance of micellar solutions
were obtained on a CDMꢀ2d conductometer (Denmark). The
conductance of bidistilled water, which was used for preparing
solutions of the reactants, was accepted as zero. The surface
tension was determined by the ring detachment method on a
Du Nouy tensiometer.
56
54
52
50
48
46
44
The effective hydrodynamic radius of the aggregates (Reff
)
was determined on a Photocor Complex instrument for dynamic
and static light scattering. The radiation source was a He—He
gas laser with a power of 10 mW and a wavelength of 633 nm.
The effective radii of the aggregates were calculated from the
diffusion coefficients using the Stokes—Einstein equation for
spherical particles of the same size taking into account the visꢀ
cosity of the solutions under study.
For each system, the hydrodynamic radius was determined
as the arithmetic mean from the data of ten measurements. The
measurement error was ≤10%.
1
2
The kinematic viscosity of solutions was determined using a
VPZhꢀ1 capillary glass viscosimeter (internal diameter of the
capillary 0.54 mm, viscosimeter constant 0.01162 mm2 s–2). The
measurements were carried out in a temperatureꢀcontrolled vesꢀ
sel at 25 0.2 °C.
–5
–4
–3
logCPCR
Fig. 1. Surface tension isotherms (σ) of solutions of PCR 1 and 2
at their different concentrations (CPCR
(30 vol.%), 25 °C).
) (water—DMF
The kinetic dependences were analyzed in terms of the equaꢀ
tion of the pseudoꢀphase model of micellar catalysis18
Linear and branched waterꢀsoluble poly(ethyleneꢀ
imines) (PEI) were used as polyelectrolytes in this work.
kobs = [kw + kmKS(CSurf – CMC)]/
/[1 + KS(CSurf – CMC)],
(2)
Experimental
where kobs is the observed rate constant of the firstꢀorder reacꢀ
tion (s–1); kw and km are the reaction rate constants in the
solvent bulk and in the micellar phase (s–1), respectively; KS is
the binding constant of the substrate and micelle (L mol–1);
CSurf is the surfactant concentration (mol L–1).
4ꢀNitrophenyl bis(chloromethyl)phosphinate (3) and
bis(4ꢀnitrophenyl) methylphosphonate (4) were synthesized
using known procedures.15 Samples of branched PEI (Fluka)
with the molecular weights 10000 (PEI10) and 800 (PEI0.8),
linear PEI with the molecular weight 5000 (LPEI5), and the
PEI10 sample modified by C12H25 groups (12ꢀPEI10) were used.
The latter were synthesized according to a described proceꢀ
dure16 by the reaction of PEI10 with dodecyl bromide. The alkyꢀ
lated polymer isolated from the organic layer was evacuated by
heating to a constant weight and characterized by IR and
1H NMR spectroscopy. The molecular weight of the monoꢀ
meric unit of PEI was determined by potentiometric titration on
a pHꢀ150MA instrument.
Results and Discussion
We found by conductometry that in a water—DMF
(30 vol.%) medium at critical association concentrations
(CAC) poly(ethyleneimines) form aggregates. It should
be noted that the conductometric curves for the polyelecꢀ
trolytes studied contain two breaks: at (0.8—4)•10–3
(CAC1) and (0.9—1)•10–2 mol L–1 (CAC2) (Table 1).
Calix[4]resorcinarenes 1 and 2 containing the alkylphosꢀ
phonate groups were synthesized according to a described proꢀ
cedure.17 The structures and compositions of the compounds
Table 1. Critical association concentrations (CAC) of
poly(ethyleneimines) in a water—DMF (30 vol.%) medium in
the absence and presence of PCR 1 (30 °С)
1
were confirmed by H NMR, 31P NMR, and IR spectroscopy,
MALDIꢀTOF mass spectrometry, and elemental analysis data.
The kinetics of hydrolysis of 4ꢀnitrophenyl esters of tetraꢀ
coordinate phosphorus acids was studied by spectrophotometry
on a Specord UV—VIS instrument at the initial substrate conꢀ
centrations 5•10–5—1•10–4 mol L–1 and different pH values.
The course of the reaction was monitored by a change in the
absorbance of the solutions (A) at 400 nm (formation of the
4ꢀnitrophenoxide anion). The conversion was >90%. The obꢀ
served rate constants of the firstꢀorder reaction (kobs/s–1) was
calculated using the regression method by the equation
PEI
CPCR•104
CAC1•103
mol L–1
CAC2•102
PEI10
PEI10
12ꢀPEI10
12ꢀPEI10
PEI0.8
—
2.7
—
4.0**
—
4.0
—
4.0
0.9
2.4*
1.0
0.8
1.0
1.3
0.96
0.9
0.95
1.5
PEI0.8
LPEI5
1.85
2.0
ln(A∞ – At) = –0.434kobst + const,
(1)
0.9
where A∞ and At are the absorbances at the reaction cessation
and at the time t, respectively.
* According to the viscosimetry data, 2•10–3 mol L–1
.
** For PCR 2.

Poly(ethyleneimine)—calixarene systems
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
961
χ/µS cm–1
The molecular weight of the electrolyte and the presence
of longꢀchain alkyl radicals in the macromolecule affect
the CAC1 values, and the CAC2 values are close for all
PEI samples under study (see Table 1).
44
36
28
20
12
1
2
Probably, aggregation of PEI first occurs inside one
macromolecule (intrapolymer interactions) involving the
N...HN hydrogen bonds, whereas for 12ꢀPEI10 the aggreꢀ
gation first involved strong hydrophobic interactions. The
CAC2 values in the PEI—water—DMF systems characꢀ
terize structural rearrangements of the aggregates, which
involves, evidently, several polyelectrolyte macromolꢀ
ecules (interpolymer interactions). This can change the
sizes and properties of the polymeric associates. We found
by light scattering that the PEI concentration affects the
radius size: for 12ꢀPEI10 Reff = 88 and 106 nm at concenꢀ
trations of 0.01 and 0.02 mol L–1, respectively. Note that
in a water—DMF medium the sizes of the PEI aggregates
are much larger than those in water. For instance, the
effective radius of 12ꢀPEI10 (0.02 mol L–1) in water is
72 nm and that in a water—DMF medium is 106 nm. The
presence of DMF in the system should decrease the disꢀ
sociation of the acidic groups of PCR capable, probably,
of forming complexes with DMF, although, as shown
earlier,19 the interaction of phosphorus acids with water is
energetically more favorable than that with DMF.
8
16
24
C12ꢀPEI10/mol L–1
Fig. 2. Plots of the electrical conductance (χ) vs. 12ꢀPEI10 conꢀ
centration (C12ꢀPEI10) in the absence (1) and presence of
PCR 2 (2) (water—DMF (30 vol.%), 30 °C).
tion of combined aggregates (polyelectrolyte complexes
with calix[4]resorcinarenes) in PEI—PCR—water—DMF
systems. The plots of the electrical conductivity
vs. 12ꢀPEI10 concentration in the absence and presence
of PCR are shown in Fig. 2 as an example.
For 12ꢀPEI10 some increase in the CAC is observed in
a water—DMF medium (see Table 1) compared to an
aqueous solution, where CAC1 = 1.8•10–3 mol L–1 and
CAC2 = 8•10–3 mol L–1. It is most likely that the CAC
values decrease in an aqueous medium, because the hydroꢀ
phobic interactions that are more pronounced in water
participate primarily in the formation of the polymer asꢀ
sociate 12ꢀPEI10. Interestingly, for PEI10 the aggregation
occurs in water at high concentrations (0.01 mol L–1),
although CAC1 and CAC2 are determined for PEI10 in
the presence of DMF (see Table 1). It is known20 that
DMF favors the destruction of the water structure due to
the arrangement of its Me groups in cavities of the tetraꢀ
hedral framework of water, which can affect the solvation
of the nitrogen atoms of PEI and its aggregation properꢀ
ties. Note that the CAC1 value for LPEI5 in a water—DMF
medium differs strongly from CAC1 for branched PEI,
but structural rearrangements in these samples occur at
virtually equal concentrations (CAC2) (see Table 1). The
conductometric curves for PEI0.8 in water also exhibit
two breaks (at 1.1•10–3 and 1.6•10–3 mol L–1).
It is known21,22 that the properties of mixed polyꢀ
mer—amphiphile compositions (viscosity, surface activꢀ
ity, electrical conductance, aggregation numbers of the
amphiphile, size of the polymer globule, and others)
change compared to the properties of the systems based
on individual components. We found that in the presence
of PCR in a water—DMF medium the CAC1 values for
the PEI samples (except for PEI0.8) decrease. According
to published data,21,23 this indicates in favor of the formaꢀ
The formation of the mixed nanostructures confirms
the sharp increase in the radii of the 12ꢀPEI10 aggregates
(0.01 mol L–1) from 88 to 138 nm in the presence of
PCR 1 (4•10–4 mol L–1) in a water—DMF medium,
which was determined by us using the light scattering
method.
Several publications on studying selfꢀassembling in
aqueous systems based on PEI and anionic surfactants are
available.24—26 Aggregation manner in these compositions
varies depending on the pH of the medium and the moꢀ
lecular weight and structure of the polyelectrolyte.
The main intermolecular interactions in the
PEI—PCR—water—DMF systems are electrostatic interꢀ
actions and hydrogen bonds of the N...HN and OH...N
types, whereas hydrophobic binding is substantial for the
compositions based on 12ꢀPEI10. Contributions of nonꢀ
covalent interactions depend on the pH of the medium,
because they change the ratio of charged and free nitroꢀ
gen atoms of the polyelectrolyte and the number of anꢀ
ions of the alkylphosphonate fragments. This should unꢀ
ambiguously affect the aggregation properties of the sysꢀ
tems under study. The fraction of the free amino groups
in PEI (α) at different pH values of the medium and in the
presence or absence of PCR was determined by potentioꢀ
metric titration of the samples of the PEI studied in a
water—DMF medium using the Henderson—Hasselbach
equation27 (Table 2). The presence of PCR exerts a weak
effect on the α value. At high pH values poly(ethyleneꢀ
imines) are almost neutral polymers (see Table 2), beꢀ
cause the fraction of the charged amino groups (1 – α) is

962
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
Pashirova et al.
Table 2. Fraction of the free amino groups (α) in the PEI samples
(0.02 mol L–1) in a water—DMF (30 vol.%) medium at differꢀ
ent pH values (30 °C)
ball, whose formation involves the hydrophobic fragments
of the macromolecule. The aggregation of PEI10 in a waꢀ
ter—DMF medium begins at a higher concentration (see
Table 1) involving N...HN hydrogen bonds. In this case,
Reff in a water—DMF medium for 12ꢀPEI10 is much longer
pH
PEI10
PEI0.8 LPEI5 12ꢀPEI10
*
12ꢀPEI10—
—PCR 1**
than that for PEI10 (106 and 4 nm, respectively (CPEI
=
0.02 mol L–1)). Therefore, it can be assumed that PCR
interacts with PEI10 as shown in Fig. 3, a, and the interꢀ
action with 12ꢀPEI10 occurs as shown in Fig. 3, b. At
the same time, the large size of the PCR aggregates
(Reff ≈ 100 nm) assumes that for the formation of comꢀ
bined structures the calixarene nanoaggregate can serve as
a scaffold on which the supramolecular catalyst is formed.
A probability of threading PCR on the PEI macromolꢀ
ecules according to the type of pseudorotaxane formaꢀ
tion28 cannot be rejected; however, this requires addiꢀ
tional proofs.
It is known14,29—32 that aqueous and aqueousꢀorganic
compositions based on calixarenes manifest catalytic acꢀ
tivity in processes of ester bond cleavage in esters of phosꢀ
phorus and carboxylic acids. The weak catalytic effect of
PCR on the hydrolysis of phosphorus acid esters in aqueꢀ
ousꢀalcohol media was shown, whereas in aqueous DMF
virtually no catalytic activity of these compounds is obꢀ
served.33 The catalytic effect of the PEI—water composiꢀ
tions in the hydrolysis of phosphorus acid esters was deꢀ
scribed,34—37 including for PEI10 and LPEI5.35,37 Howꢀ
ever, in a water—DMF medium the catalytic activity of
PEI has not been studied earlier.
9.5 0.92
9.0 0.84
8.5 0.75
8.0 0.64
7.5 0.5
0.99
0.94
0.87
0.77
0.64
0.49
0.35
0.26
0.16
0.07
—
0.92 (0.96)
0.95
0.89
0.81
0.71
0.58
0.45
0.31
0.23
0.14
0.05
0.96
0.81
0.69
0.57
0.46
0.36
0.23
0.13
0.03
0.87 (0.92)
0.77 (0.79)
0.64 (0.67)
0.51 (0.56)
0.39 (0.41)
0.27 (0.3)
0.17 (0.25)
0.09 (0.14)
0.016 (0.07)
7.0 0.4
6.5 0.31
6.0 0.23
5.5 0.15
5.0 0.08
* The value for CPEI = 0.01 mol L–1 is given in parentheses.
** CPEI = 0.01 mol L–1, CPCR = 4•10–4 mol L–1
.
insignificant: for instance, at pH 9.5 it is 0.05—0.08, which
agrees with literature data.26
A PEI macromolecule (Fig. 3, a) or globule (Fig. 3, b)
can be considered as a soluble polymer matrix (scaffold)
on which a PCR molecule "sits down," approaching to the
polyelectrolyte by its lower rim containing the alkylꢀ
phosphonate fragments that bind to the nitrogen atoms
of PEI.
Probably, the mixed PEI10—PCR and 12ꢀPEI10—PCR
aggregates have different structures. A 12ꢀPEI10 macroꢀ
molecule contains rather high number of longꢀchain radiꢀ
cals arranged closely to each other and in rather low conꢀ
centration (CAC1 ≈ 2•10–3 mol L–1) it forms a polymer
In the present work, the catalytic effect of the
PEI—water—DMF and PEI—PCR—water—DMF
(30 vol.%) systems on the hydrolysis of 4ꢀnitrophenyl
bis(chloromethyl)phosphinate (3) and bis(4ꢀnitrophenyl)
methylphosphonate (4) (Scheme 1) was studied.
a
b
Scheme 1
R1 = R2 = CH2Cl (3); R1 = Me, R2 = 4ꢀO2NC6H4O (4)
The plots of the observed rate constants for hydrolysis
of substrates 3 and 4 vs. pH of the medium in the
PEI—water—DMF and PEI—PCR—water—DMF sysꢀ
tems are shown in Figs 4 and 5. The catalytic activities of
PEI10 and PEI5 are equal, and 12ꢀPEI10 catalyzes the
hydrolysis of the esters considered by ~7—10 times more
rapidly (see Fig. 4). It is known37 that PEI catalyze this
Fig. 3. Interactions in the PEI—PCR system involving the PEI
macromolecule (a) or globule (b).

Poly(ethyleneimine)—calixarene systems
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
963
kobs•102/s–1
kobs/k0
800
20
5
16
600
1
12
2
400
2
8
4
1
200
4
3
7.6
8.4
9.2
pH
8
9
10
pH
Fig. 6. Plots of the acceleration value of the hydrolysis of
phosphinate 3 (kobs/k0) vs. pH in a water—DMF (30 vol.%)
Fig. 4. Plots of the observed rate constant of hydrolysis of
phosphinate 3 (kobs) vs. pH for PEI10 (1), 12ꢀPEI10 (2),
LPEI5 (3), PEI10—PCR 2 (4), and 12ꢀPEI10—PCR 1 (5)
medium for 12ꢀPEI10 (1) and 12ꢀPEI10—PCR 1 (2) (СPCR
4.0•10–4 mol L–1, СPEI = 0.01 mol L–1, 30 °С).
=
(water—DMF (30 vol.%), CPEI
= 0.02 (1, 3, 4) and
0.01 mol L–1 (2, 5), CPCR = 4•10–4 mol L–1, 30 °C).
ferent structure. For instance, at pH 7—8 the acceleration
value for phosphonate 4 (see Fig. 5) is by ~3—5 times
higher than that for phosphinate 3 (see Fig. 6).
The study of the plot of kobs vs. PEI concentration in
the absence and presence of PCR showed that the kinetic
profiles are nonlinear and reach a plateau (Figs 7 and 8).
process via the general basic mechanism. The presence of
PCR exerts a weak effect on the catalytic activity of PEI10;
however, the acceleration values (kobs/k0) in the systems
based on 12ꢀPEI10 and PCR are much higher than those
in the absence of the latter (Fig. 6).
In the presence of PCR in an aqueousꢀorganic system
based on 12ꢀPEI10, the plots kobs = f(pH) shift considerꢀ
ably toward lower pH values (see Fig. 4), which makes it
possible to use these catalytic compositions under mild
conditions at pH 7—8, where the acceleration of hydrolyꢀ
sis achieves three orders of magnitude (see Figs 5 and 6).
It should be noted that the 12ꢀPEI10—PCR—water—DMF
system manifests some selectivity toward substrates of difꢀ
kobs•102/s–1
16
6
14
5
12
10
kobs•102/s–1
kobs/k0
4000
2
8
2
1
1.6
6
4
3000
2000
1000
1
4
1.2
0.8
0.4
2
3
0
1
2
3
CPEI•102/mol L–1
Fig. 7. Plots of the observed rate constant of hydrolysis of
phosphinate 3 (kobs) vs. PEI concentration (CPEI) for PEI10 (1),
PEI10—PCR 1 (2), PEI0.8—PCR 2 (3, 4), 12ꢀPEI10 (5), and
12ꢀPEI10—PCR 2 (6) at pH 9.5 (1, 2, 5), 8 (3, 6), and 9 (4)
(CPCR = 2.7•10–4 (2—4) and 4•10–4 mol L–1 (6), water—DMF
(30 vol.%), 30 °C).
7
8
9
pH
Fig. 5. Plots of the observed rate constant of hydrolysis of
phosphonate 4 (kobs) in the 12ꢀPEI10—PCR 2—water—DMF
(30 vol.%) system (1) and the acceleration value (kobs/k0) (2)
vs. pH (CPCR = 4.0•10–4 mol L–1, CPEI = 0.01 mol L–1, 30 °C).

964
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
Pashirova et al.
kobs•103/s–1
kobs•102/s–1
28
4
14
12
10
8
24
20
16
12
8
3
2
1
2
6
1
2
4
6
CPCR•104/mol L–1
4
Fig. 9. Plots of the observed rate constant of hydrolysis of
phosphinate 3 (kobs) vs. PCR 1 concentration in the presence of
PEI0.8 (1) and PEI10 (2) (CPEI = 0.02 mol L–1, pH 9.5, 30 °C).
2
4
6
8
C12ꢀPEI •103/mol L–1
10
Fig. 8. Plots of the observed rate constant of hydrolysis of
phosphonate 4 (kobs) vs. 12ꢀPEI10 concentration (C12ꢀPEI10) in
the absence (1) and presence of PCR 2 (2—4) at 30 (1, 2),
40 (3), and 50 °C (4) (CPCR = 4•10–4 mol L–1, water—DMF
(30 vol.%), pH 8).
ratio in the point of maximum in the kobs = f(CSurf) plots
at the PEI content equal to 0.02 mol L–1 is significantly
lower, being ~3—6 for phosphorus acid esters of different
structure.34,36 In a water—DMF medium PCR has no
catalytic activity in the hydrolysis of phosphorus acid esꢀ
ters33 but in the presence of PCR the catalytic effect of
PEI10 and PEI0.8 increase by ~2—2.5 times (see Fig. 9).
This confirms the formation of combined PEI—PCR
structures with the higher catalytic activity than that of
the polyethyleneimine aggregates.
The kinetic curves kobs = f(CPEI) were processed using
Eq. (2) for the pseudoꢀphase model of micellar catalyꢀ
sis,18 which is used successfully for polymeric and nanoꢀ
structured polymeric systems.34,36,39,40 The obtained paꢀ
rameters (km, KS, and CMC) are given in Table 3.
This assumes the primary binding of the substrate by mixed
PEI—PCR aggregates according to the host—guest type
similarly to the formation of enzyme—substrate comꢀ
plexes,38 which precedes the reaction itself. The plots of
kobs of hydrolysis of substrate 3 vs. PCR concentration in
the presence of constant amounts of PEI10 and PEI0.8
(0.02 mol L–1) have also nonlinear profiles with maxima
at CPCR ≈ (4—4.5)•10–4 mol L–1 (PEI : PCR ≈ 45—50)
(Fig. 9). Usually in surfactant—PEI systems the CPEI/CSurf
Table 3. Parameters of hydrolysis of substrates 3 and 4 in PEI—water—DMF (30 vol.%) and
PEI—PCR 2—water—DMF (30 vol.%) systems at different pH and T values calculated by Eq. (2)
Subꢀ
strate
PEI
СPCR•104
/mol L–1
pH
T
/°С
km
/s–1
KS
/L mol–1
CMC•103 km/k0*
/mol L–1
3
3
3
3
3
3
4
4
4
4
PEI10
PEI10
12ꢀPEI10
12ꢀPEI10
PEI0.8
—
2.7**
—
4.0
2.7
2.7
—
4.0
4.0
4.0
9.5
9.5
9.5
8.0
8.0
9.0
8.0
8.0
8.0
8.0
25
30
30
30
30
30
30
30
40
50
0.071
0.11
0.31
55
53
89
490
950
280
190
1400
730
550
29
3.4
4.4
6.3
19.4
367
14.5
11.5
990
1560
2560
3560
2.2
1.1
1.0
2.2
2.5
2.4
1.5
1.3
0.22
0.008
0.063
0.0089
0.014
0.023
0.032
PEI0.8
12ꢀPEI10
12ꢀPEI10
12ꢀPEI10
12ꢀPEI10
* k0 is the rate constant of the noncatalytic process at the corresponding pH.
** For PCR 1.

Poly(ethyleneimine)—calixarene systems
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
965
Ea/kJ mol–1
∆S/J K–1 mol–1
–300
As can be seen from the data in Table 3, substrate 4
under similar conditions (pH 8, 30 °C) is much stronger
34
bound by the 12ꢀPEI10—PCR aggregate (KS
=
1400 L mol–1) than substrate 3 (KS = 490 L mol–1), which
affects the acceleration of the hydrolysis reaction
(1560 and 367 times, respectively). The binding constants
for substrate 3 decrease with the pH increase (for exꢀ
ample, for the system based on PEI0.8 and PCR it deꢀ
creases from 950 (pH 8) to 280 L mol–1 (pH 9)), i.e., with
a decrease in the fraction of the protonated nitrogen atꢀ
oms (1 – α) from 0.23 to 0.06 (see Table 2). Evidently,
the protonated nitrogen atoms of PEI on the surface of
polymerꢀcolloidal globule participate only in the binding
of phosphorus acid esters similarly to micelles of cationic
surfactants. In the presence of PCR, the CMC values for
PEI10 determined by the kinetic method decrease considꢀ
erably (see Table 3), which agrees with the conductometꢀ
ric data (see Table 1). For 12ꢀPEI10 these values are close
to CAC1 (conductometric method). At the same time, it
should be mentioned that the CMC determined by the
kinetic and conductometric methods can differ, because
the presence of the substrate in the reaction medium can
affect the aggregation properties of the system.22
–305
–310
–315
–320
32
30
28
26
2
4
6
C12ꢀPEI •103/mol L–1
10
Fig. 10. Plots of the activation parameters of hydrolysis of subꢀ
strate 4 (Ea and ∆S) in the 12ꢀPEI10—PCR 2—water—DMF
(30 vol.%) system vs. polyelectrolyte concentration (C12ꢀPEI10).
the substrate structure (selectivity), molecular weight and
structure of the polyelectrolyte, pH of the medium, and
temperature were shown.
The effective activation parameters of the hydrolysis
of substrate 4 in the 12ꢀPEI10—PCR—water—DMF sysꢀ
tem were calculated from the kinetic plots kobs = f(CPEI
)
Investigations of the structural organization of polyꢀ
mer—amphiphile complexes provide new routes for the
design of nanostructured polymeric systems for the purꢀ
pose of developing materials with predicted properties,
including the catalytic ones.
at different temperatures (see Fig. 8). The effective actiꢀ
vation parameters, contributed from the reaction in the
solution bulk, aggregation processes, and the reaction on
the surface of the supramolecular associate, depend on
the 12ꢀPEI10 concentration. The sharp decrease in the
activation energy (Ea) to 25 kJ mol–1 is observed, most
likely, in the region of formation of the 12ꢀPEI10—PCR
complexes at the polymer concentration ~(4—6)•10–3
mol L–1 (CPEI : CPCR ≈ 10—15) (Fig. 10), i.e., at the
12ꢀPEI10 content higher than CAC1 (see Table 1). It can
be assumed that CAC1 corresponds to the onset of formaꢀ
tion of the polymeric ball (matrix) with which the PCR
molecules then interact (formation of combined aggreꢀ
gates). It should be mentioned that for the systems based
on hydrophobic 12ꢀPEI10 the CPEI : CPCR ratio equal
to 10—15 is considerably lower than that for PEI10 and
PEI0.8 (CPEI : CPCR ≈ 45—50, see Fig. 9). The activation
energy of the reaction in the mixed 12ꢀPEI10—PCR agꢀ
gregates calculated from the km values at different temꢀ
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 05ꢀ03ꢀ
08086ꢀofi_a).
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Received December 2, 2006;
in revised form March 20, 2007