Synthesis and hydrodynamic behavior of stoichiometric complexes of cationic polyelectrolytes with amphiphilic anions

Article abstract of DOI:10.1007/s11167-005-0477-7

Complexation of poly(N,N-dimethyl-N-benzyl-N-methacryloyloxyethyl)ammonium chloride with oppositely charged amphiphilic compounds was studied. The solubility and hydrodynamic properties of the resulting complexes in chloroform, methanol, and chloroform-he

Full text of DOI:10.1007/s11167-005-0477-7

Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1190 1193. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
2005, pp. 1211 1214.
Original Russian Text Copyright
2005 by Kovaleva, V. Navrotskii, Shulevich, A. Navrotskii, Novakov.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Synthesis and Hydrodynamic Behavior of Stoichiometric
Complexes of Cationic Polyelectrolytes with Amphiphilic Anions
O. Yu. Kovaleva, V. A. Navrotskii, Yu. V. Shulevich,
A. V. Navrotskii, and I. A. Novakov
Volgograd State Technical University, Volgograd, Russia
Received October 6, 2004; in final form, April 2005
Abstract Complexation of poly(N,N-dimethyl-N-benzyl-N-methacryloyloxyethyl)ammonium chloride with
oppositely charged amphiphilic compounds was studied. The solubility and hydrodynamic properties of the
resulting complexes in chloroform, methanol, and chloroform hexane and chloroform toluene mixtures
were determined.
Polyelectrolytes (PEs) interact with oppositely
charged diphilic ions of micelle-forming surfactants to
form polyelectrolyte complexes (PECs) with unique
physicochemical properties [1]. Studies of such inter-
actions are necessary for understanding the processes
that occur in natural PECs of biopolymers and diphilic
compounds [2 4] and the behavior of PECs at floc-
culation and stabilization of dispersions [5]. It is
known [6 9] that stoichiometric PECs (SPECs)
formed by anionic surfactants and polydimethyldial-
lylammonium chloride (PDMDAAC) or poly-N-ethyl-
zation was performed in an aqueous solution (2 M
monomer concentration) at 25 0.5 C up to 96 98%
conversion. Then, the polymerizate was dissolved
in methanol and precipitated with diethyl ether.
tert-Butylperoxy-2-propanol used as initiator was
prepared by the procedure given in [11]. The resulting
polymer was additionally purified by recrystallization
from methanol with diethyl ether and dried in a vacu-
um (1.5 2.0 mm Hg, 20 0.5 C) to constant weight.
In our study we used commercial aqueous solutions
of PE-2 (40 wt %). The solutions of PE-2 of various
concentrations were prepared from the initial solution
by successive dilution.
4
5
4-vinylpyridinium bromide (PEVPB) (M 10 10 )
w
are soluble in low-polar organic solvents. However,
the features of hydrodynamic behavior of SPECs of
macromolecular polyelectrolytes based on aminoalkyl
acrylates are still poorly understood. Poly(N,N-dimeth-
yl-N-benzyl-N-methacryloyloxyethyl)ammonium chlo-
ride (PE-1) shows promise for preparing hydrophobic
complexes, as it has higher molecular weight as com-
pared to poly-N,N-dimethyldiallylammonium chloride
(PE-2) and exhibits pronounced hydrophobic proper-
ties imparted by the benzyl substituent [10].
The intrinsic viscosities of PE-1 and PE-2 deter-
1
mined in 0.1 M NaCl at 30 C were 4.7 and 1.4 dl g ,
respectively.
Anionic surfactants such as sodium dodecyl sulfate
SDS (chemically pure grade, Merck) and Volgonat-
emul’gator (VE) [mixture of sodium salts of alkylsul-
fonic acids RSO Na, R = C C , Khimprom Joint-
3
16 18
Stock Company, Volgograd, Russia; STP (Enterprise
Standard) 2480-282-05763458 99] were used without
additional purification.
In this work we studied the features of interaction
between various amphiphilic anions and PE-1 and the
hydrodynamic behavior of the resulting SPECs in
chloroform, methanol, and mixed solvents.
The stoichiometric polyelectrolyte complexes of
surfactants were prepared from the aqueous solutions
of components with vigorous stirring. The concentra-
tions of polyelectrolytes and surfactants were 0.01 and
0.1 M, respectively. The resulting precipitate of SPEC
was separated, washed with water, and dried in a
desiccator to constant weight.
EXPERIMENTAL
Polyelectrolyte PE-1 was prepared by radical poly-
merization of the monomer, which was synthesized by
alkylation of dimethylaminoethyl methacrylate with
benzyl chloride at 0 3 C in acetone and recrystallized
from acetone acetonitrile mixture. Radical polymeri-
The composition of the reaction mixture Z was
determined as the ratio of the concentration of the sur-
factant ions to the concentration of PE units in the
1070-4272/05/7807-1190 2005 Pleiades Publishing, Inc.

SYNTHESIS AND HYDRODYNAMIC BEHAVIOR OF STOICHIOMETRIC COMPLEXES
Synthesis of insoluble complexes based on PE-1 and PE-2
1191
1
PE surfactant
PE-1 SDS
Z
SPEC yield, wt %
S, wt %
N, wt %
S/N
, mol
r, dl g *
1.0
1.5
3.0
65
68
5.5
3.1
4.7
2.30
1.70
2.70
2.4
1.8
1.7
1.00
0.80
0.76
5.3
4.6
PE-1 VE
PE-2 SDS
PE-2 VE
1.0
1.5
3.0
1.0
1.5
3.0
1.0
1.5
3.0
84
86
5.8
4.9
5.4
2.28
2.56
2.20
2.5
1.9
2.4
1.10
0.84
1.07
6.3
5.2
5.1
59
63
6.9
2.70
2.5
1.09
38
63
7.4
3.40
2.2
0.95
1
* Reduced viscosity of the chloroform solution of the complex (0.2 g dl ).
system (Z = [surfactant]/[PE]). The composition of
PEC was characterized by the ratio of the number
of diphilic surfactant ions in PEC to the number of
PE units in the polymeric complex ( = [surfac-
tant] /[PE] . The composition of the resulting
the polyanion chain length. For example, PEVPB with
the degree of polymerization of 1000 yields SPEC
with
= 1.0 [13], whereas the same polymer with
the higher degree of polymerization (2000) gives an
insoluble SPEC with = 0.85. A similar trend is ob-
served with the complexes PE-2 SDS and PE-1 VE
PEC
PEC
PECs was determined by chemical analysis.
(
= 1.09 and 0.84, respectively). This suggests that
To determine the solubility and hydrodynamic
properties of SPECs in organic solvents, the samples
were placed in chemically pure grade methanol,
chloroform, benzene, toluene, and butyl acetate.
certain decrease in is associated with the length of
the polymeric ion, because the probability of forma-
tion of various defects (e.g., loops) increases with in-
creasing length of the polymer chain. These defects
are also typical for double-stranded chains of stoichi-
ometric complexes of oppositely charged polymeric
ions [14]. These defects are formed owing to confor-
mational noncomplementarity of the polymer chain
and surfactant micelles, because the structure of SPEC
is a compromise between the conformation of poly-
meric ion and geometric characteristics of the sur-
factant aggregates. The mismatch of these parameters
will be greater in the case of longer chains, which
causes appearance of unlinked sections in the polymer
The viscosities of the SPEC solutions in chloro-
form, methanol, and mixed solvents were measured
with an Ubbelohde viscometer (0.34 mm capillary
diameter).
A distinctive feature of the interaction of diphilic
surfactant ions with oppositely charged macroion is
that the phase state of the reaction system depends on
the initial reagent ratio Z, and certain Z values char-
acterize different phase states of PECs [12].
chain. As a result,
smaller than unity.
of the resulting complexes is
In the reaction of PE-1 with SDS and VE, the pre-
cipitate is formed only at the reagent ratio close to
stoichiometric.
It is known that the major factor determining
whether the polymer will dissolve or swell is its
specific interaction with the solvent. In this connec-
tion, we studied the behavior of SPECs in various
organic solvents. It was found that these complexes
dissolve in chloroform and methanol, whereas in
aliphatic and aromatic hydrocarbons and ethyl and
butyl acetates they occur in the swollen state. Taking
into account the polarity and proton-donor power of
methanol and chloroform, we suggest that the dissolu-
tion of SPECs in them proceeds owing to the solva-
tion of the ion pairs and ester fragments. The other
The table shows that quantitative yield of the in-
soluble complex is never obtained at the stoichiomet-
ric reagent ratio, and with increasing Z above the
stoichiometric ratio the yield of all the SPECs studied
increases. It should be noted that the yields of the
complexes in the PE-2 SDS and PE-2 VE systems
are lower than those in the corresponding systems
with PE-1. The possibility of SPEC formation is
determined by the size ratio of the polymer chain and
internal surfactant micelles. Moreover, the composi-
tion of the precipitated complex can be determined by
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005

1192
KOVALEVA et al.
1
lower that 0.1 g dl . Similar effect was observed for
complexes of sodium polystyrenesulfonate with
alkyltrimethylammonium bromides in ethanol, DMF,
and isopropanol [15]. This phenomenon was attributed
to the effective charge on the polymer chains even
in a low-polarity solvent, which enhances the electro-
static repulsion and increases the hydrodynamic size
of the polymer globule. At the same time, in chloro-
1
1
r, dl g
r, dl g
form
of the complexes is significantly lower than
r
that in methanol. The
comparable with [ ] of PE-1 in an aqueous-salt solu-
tion (4.7 dl g ), which suggests that SPECs occur in
values given in the table are
r
1
chloroform as loose swollen globules.
The behavior of the complexes in question strong-
ly differs from that of the complexes based on
PDMDAAC or PEVPB for which [ ] is 0.35
0.55 dl g and their Huggins constants k = 0.66 are
typical for linear flexible-chain macromolecules in
1
c, g dl
Fig. 1. Reduced viscosity
as a function of PEC con-
r
1
centration c in chloroform, methanol, and mixed solvents.
(1) Chloroform, (2) methanol, (3) chloroform : hexane =
70 : 30, (4) chloroform : hexane = 50 : 50, (5) chloro-
form : toluene = 70 : 30, and (6) chloroform : toluene =
50 : 50 (volume ratio in all cases).
thermodynamically good solvents. The
linearly decrease with dilution, which is typical for
uncharged polymers.
values
r
1
r, dl g
Since no dissolution of SPECs in individual hydro-
carbons was observed, their hydrodynamic behavior
was studied using mixed systems with chloroform and
toluene or hexane. The viscometric measurements per-
formed in a wide range of solvent compositions
showed no phase separation at a chloroform content
from 10 to 90 vol %.
It was expected that addition of hydrocarbons
exhibiting affinity for surfactant chains and benzyl
groups into the mixed solvent would cause solvation
of the above fragments and enhance swelling of the
polymer globule. However, as seen from Figs. 1 and
wcl, vol %
2, in the mixed solvents
sharply decreases with in-
Fig. 2. Reduced viscosity of PE-1 VE in the mixed solu-
r
r
creasing hydrocarbon content. This is probably due to
the deterioration of the conditions of the ion pair
solvation. The effect of this factor is more decisive
than the increase of the affinity for the hydrocarbon
polymer fragments. As a result, more compact poly-
mer globules are formed in the mixed solvents. Thus,
the solubility of the complexes and swelling of their
globules are primarily promoted by weakening of the
interionic interaction.
tion as a function of chloroform concentration w ; PE-1
cl
1
VE concentration 0.11 g dl . Second component of the
solvent: (1) hexane and (2) toluene.
solvents studied cannot dissolve SPECs, as they are
incapable of specific interactions with SPECs.
The dependence of the reduced viscosity on the
concentration of the complex in methanol is typical
for dissociating polyelectrolytes (Fig. 1). The reduced
viscosity of the complex
tration c 0.015 g dl is 37.1 dl g , which is com-
in methanol at a concen-
r
The revealed features in the hydrodynamic behavior
of PE surfactant complexes suggest the possibility of
their use for modifying the rheological properties of
organic liquids.
1
1
1
parable with
for PE-1 (43.3 dl g ). Thus, in meth-
r
anol the complex dissociates, and owing to the elec-
trostatic repulsion the complex macromolecules occur
in the form of a strongly swollen globule.
CONCLUSIONS
The solutions of PE-1 VE in chloroform also
exhibit abnormal concentration dependences of
(1) Complexing of poly(N,N-dimethyl-N-benzyl-
N-methacroyloxyethyl)ammonium chloride with ani-
r
(Fig. 2), which strongly increases at concentrations
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005

SYNTHESIS AND HYDRODYNAMIC BEHAVIOR OF STOICHIOMETRIC COMPLEXES
1193
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63 86%) with
ratio Z = 1 3.
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anol and chloroform exhibit abnormal hydrodynamic
behavior typical for polyelectrolytes. The solubility
and high viscosity of solutions of the complexes are
enhanced by solvation of the ion pair and polar frag-
ments with proton-donor solvents.
10. Kotlyarevskaya, O.O., Navrotskii, A.V., Orlyan-
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