Synthesis of sterically hindered benzoquinone methacrylates

Article abstract of DOI:10.1007/s11172-012-0165-8

Sterically hindered p- and o-benzoquinone methacrylates, viz., 2,5-di(tert-butyl)-3,6-di-oxocyclohexa-1,4-dienyl methacrylate and 2,5-di(tert-butyl)-3,4-dioxocyclohexa-1,5-dienyl methacrylate, were synthesized by O-acylation of the lithium and tetrabutyla

Full text of DOI:10.1007/s11172-012-0165-8

Russian Chemical Bulletin, International Edition, Vol. 61, No. 6, pp. 1215—1219, June, 2012
1215
Synthesis of sterically hindered benzoquinone methacrylates
M. P. Shurygina, O. V. Markina, N. O. Druzhkov, T. I. Kulikova, A. V. Cherkasov,
A. V. Piskunov, S. A. Chesnokov, and V. K. Cherkasov
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Eꢀmail: sch@iomc.ras.ru
Sterically hindered pꢀ and oꢀbenzoquinone methacrylates, viz., 2,5ꢀdi(tertꢀbutyl)ꢀ3,6ꢀdiꢀ
oxocyclohexaꢀ1,4ꢀdienyl methacrylate and 2,5ꢀdi(tertꢀbutyl)ꢀ3,4ꢀdioxocyclohexaꢀ1,5ꢀdienyl
methacrylate, were synthesized by Oꢀacylation of the lithium and tetrabutylammonium salts of
3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoquinone with methacryloyl chloride. The influence of the
nature of cation and solvent on regioselectivity of the acylation was studied. The oꢀbenzoꢀ
quinone derivative obtained can serve as a paramagnetic ligand in metal complexes.
Key words: benzoquinones, methacrylates, monomers, ligands.
Chemistry of coordination polymers is one of the acꢀ
tively developing trends in modern coordination and maꢀ
terials chemistry.1,2 In the broad typology of these comꢀ
pounds, a special place is taken by coordination polymers
with radical ligands, which are of interest for the developꢀ
ment of molecular magnets.3—5 In this field, the attention
is mainly concentrated on the metal complexes with staꢀ
ble nitroxyl and nitronylꢀnitroxyl radical ligands. As of the
present moment, no less promising oꢀsemiquinone derivꢀ
atives have not virtually been studied. At the same time,
the ability of oꢀbenzoquinone reduction products (oꢀsemiꢀ
quinone radical anions) to form complexes with metals is
well known.6,7 One of the possible approaches to the synꢀ
thesis of metalꢀcontaining polymers is based on the introꢀ
duction of a metal fragment into a side chain. To accomꢀ
plish this in the case of oꢀsemiquinone complexes, it is
necessary for the oꢀquinones to contain functional groups
capable of polymerization. A freeꢀradical polymerization
of metal complexes with oꢀsemiquinone ligands is of inꢀ
terest as one of the possible approaches to the synthesis of
multiꢀspin metalꢀcontaining polymers. In the literature,
there are examples only describing synthesis of pꢀbenzoꢀ
quinones containing allylic fragments.8,9
between methacryloyl chloride and the salts of benzoꢀ
quinone 1. In this case, the anion 1´ is the true reactant
(Scheme 1).
Compound 1 can exist in solutions as two tautomers of
the pꢀ and oꢀbenzoquinone type. For its salt 1´, the existꢀ
ence of two corresponding isomers is also possible (see
Scheme 1).
According to quantum chemical calculations perꢀ
formed on the B3LYP/6ꢀ311+G(d,p) level, in the "free"
anion 1´ the negative charge is delocalized between O(3),
C(2), C(3), C(4), and O(2) atoms (Fig. 1) so that the
electron density on the oxygen atoms O(3) and O(2) is
comparable, therefore, it is hard to expect for the regioꢀ
selectivity to be high when it reacts with electrophilic reꢀ
agents. Theoretically, both isomers with paraꢀ (2a) and
orthoꢀquinonoid structure (2b) should be formed in comꢀ
parable amounts.
However, in fact (Table 1) the regiodirection of the
electrophilic attack strongly depended on the nature of
O(3)
–0.70
1.296
C(5)
1.491
The present work is devoted to the preparation of sterꢀ
ically hindered oꢀ and pꢀbenzoquinones containing a methꢀ
acrylate fragment. To meet this goal, we used a well known
methacrylation reaction between methacryloyl chloride
and alcohols in the presence of bases.10,11 We have chosen
3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoquinone (1) as an
object of our studies.12 Attempted direct methacrylation
of compound 1 failed, probably, because of the presence
of intramolecular hydrogen bonding, which lowers activiꢀ
ty of the hydroxyl proton. The methacrylate fragment
can be alternatively introduced by an exchange reaction
1.425
1.351
C(4)
C(3)
C(6)
1.487
1.428
C(2)
1.277
C(1)
1.554
1.252
O(1)
–0.66
O(2)
Fig. 1. Distribution of bond distances and NBOꢀcharges on the
oxygen atoms in the anion of 3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoꢀ
quinone 1´ according to the quantum chemical calculations.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1202—1206, June, 2012.
1066ꢀ5285/12/6106ꢀ1215 © 2012 Springer Science+Business Media, Inc.

1216
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 6, June, 2012
Shurygina et al.
(Li+), the paraꢀ1´ isomer would be more stabilized as
compared to the orthoꢀ1´ isomer due to the chelate effect.
The power of this effect would enhance with the decrease
in polarity and solvation ability of the solvent. Therefore,
the proportion of product 2a in the products of methꢀ
acrylation reaction would increase (see Scheme 1).
Scheme 1
Bulky cations possessing low coordinating ability (such
as Bu4N+), on the contrary, will facilitate formation of
loose ion pairs, in which, as the solvation ability and poꢀ
larity of the solvent increase, the equilibrium will be disꢀ
placed to the side of the solventꢀseparated ion pairs, to the
state of "free" anion, whose involvement into the reaction
will give higher proportion of oꢀderivative 2b.
In the polar, solvating solvents which facilite formaꢀ
tion of the solventꢀseparated ion pairs, the "free" anion is
the reacting species, and, therefore, the nature of cation
has little or no effect. In THF, the use of both salts led to
a predominance of orthoꢀisomer 2b, while in acetonitrile
paraꢀisomer 2a is predominant. The dependence of regioꢀ
selectivity of methacrylation of compound 1 from the naꢀ
ture of cation is the most prominent in nonpolar benzene.
In this solvent, the exchange of Li+ with Bu4N+ leads to
a nearly complete inversion of regioselectivity: more than
90% of isomer 2a when M = Li and more than 70% of
isomer 2b when M = Bu4N. The high proportion of 2a in
the case of lithium salt in benzene is explained by the shift
of the equilibrium (see Scheme 1) to the side of formation
of the intimate ion pair, whose acylation would lead to
paraꢀisomer. When Bu4N salt is used in benzene, steric
factors apparently become dominating. The position of
the bulky tetrabutylammonium cation in the contact ion
pair near the oxygen atom O(3) has proved more sterically
favorable, resulting in the shift of the equilibrium in this
ion pair to the side of orthoꢀ1´ isomer, whose methacrylaꢀ
tion gives product 2b. In all the cases, the total yield of
2a + 2b was higher than 90%.
Both reaction products 2a and 2b were isolated in the
individual form by column chromatography and characꢀ
terized by NMR, IR, and UV spectroscopy, elemental
analysis, and Xꢀray crystallography. The NMR spectra of
compounds 2a,b exhibit signals for the protons of nonꢀ
equivalent But groups (for 2a, at  1.26 and 1.35, for 2b, at
 1.23 and 1.29), the protons of the methacrylate group
(CH3 at  2.05 (2a, 2b), CH2= at  5.82—5.83 and
6.32 (2a), 5.88 and 6.32 (2b)), and the proton at position 5
of the quinone ring (at  6.50 (2a) and 6.40 (2b)). The IR
spectra of compounds 2a,b exhibit absorption bands of
stretching vibrations of the C=O group in the methacrylate
fragment (1740 (2a) and 1728 (2b) cm–1) and the carbonꢀ
yl groups of the quinone fragments (1658 and 1670 cm–1
(2a), 1655 and 1678 cm–1 (2b)). The structures of benzoꢀ
quinoneꢀmethacrylates obtained were ultimately estabꢀ
lished by Xꢀray crystallography (Figs 2 and 3). The bond
distances obtained for the C—C and C—O bonds of differꢀ
ent order are close to average values for double bonds
M = Li, Bu4N
Reagents and conditions: i. LiOH, THF; ii. LiOH, THF, then,
Bu4NBr; iii. H2C=C(Me)C(O)Cl, MeCN, THF or benzene.
cation and solvent. In the case of compact cations with
small ionic radius, inclined to form intimate ion pairs
Table 1. The ratio of isomers 2a : 2b in the acylation prodꢀ
ucts of 3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoquinone lithꢀ
ium and tetrabutylammonium salts in different solvents
(20 C)
Cation
Ratio 2a : 2b
MeCN
THF
C6H6
Li+
Bu4N+
62 : 38
67 : 33
44 : 56
36 : 64
91 : 9
28 : 72

Benzoquinone methacrylates
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 6, June, 2012
1217
C(8)
to 3.045, 3.119, and 2.962, 3.044 Å, respectively). The
tertꢀbutyl groups in the structure of 2b are in the gauche
conformation (14.5), the shortest distances O Me lie
C(9)
...
C(7)
in the cisꢀposition relative to the carbonyl fragment.
Apparently, the eclipsed conformation is interfered
with the intramolecular interaction between the oxyꢀ
gen atom of the methacrylate fragment O(3A) and the
carbon atom of the methyl group C(10A) (O(3A)—C(10A)
is 2.742 Å, O(3A)—H(10A) is 2.45 Å, O(3A)—H(10B)
is 2.48 Å).
C(10)
C(2)
C(3)
O(1)
C(4)
O(2)
O(4)
C(1)
A brief geometric analysis showed that the bond disꢀ
tances O(1)—H(17A) and O(1)—H(18A) are equal to 2.38
and 2.49 Å and the bond distances O(2)—H(8AA) and
O(2)—H(9AC), to 2.31 and 2.41 Å. Such geometric
characteristics indicate that the intramolecular interacꢀ
tions of the type O...H are present in the structure of 2b.
According to the correlation equations,14 the energies of
C(5)
C(15)
C(17)
C(6)
C(12)
O(3)
C(11)
C(16)
C(18)
these reactions lie in the range 2.29—3.83 kcal mol–1
.
C(13)
To investigate the complexation ability of oꢀquinoꢀ
ne 2b, we studied its photolytic reaction with Mn2(CO)10
by ESR. Irradiation of a toluene solution of 2b with
Mn2(CO)10 with unfiltered visible light leads, like in the
case of other oꢀquinones, to the formation of paramagnetꢀ
ic complexes of the type 3 (Scheme 2, Fig. 4).15
C(14)
Fig. 2. Molecular structure of 2,5ꢀdi(tertꢀbutyl)ꢀ3,6ꢀdioxocycloꢀ
hexaꢀ1,4ꢀdienyl methacrylate 2a.
C(sp2)=O (1.222 Å), C(sp2)=C(sp2) (1.349 Å) and single
bonds C(sp2)—C(sp2) (1.478 Å) in pꢀ and oꢀbenzoquinoꢀ
nes.13 In compound 2a, the quinone fragment is planar,
the planes of the quinone and the methacrylate fragments
are turned with respect to each other by 70.0, while in 2b,
the analogous angle is equal to 85.5. In addition, in comꢀ
pound 2b the carbonyl groups of the quinone fragment are
not in the plane of the ring, the dihedral angle between
them is equal to 15.4. Such a nonplanarity of the carbonꢀ
yl fragment results from the nonequivalent arrangement of
the methyl groups of the tertꢀbutyl substituents with reꢀ
spect to the oxygen atoms14 (the distances O(1)—C(17),
O(1)—C(18), and O(2)—C(8), O(2)—C(9) are equal
Scheme 2
C(17)
C(16)
C(15)
C(6)
C(5)
The hyperfine structure observed in the ESR spectrum
reflects the hyperfine interaction (HFI) of the unpaired
C(13)
C(12)
O(3)
C(18)
O(1)
C(4)
C(1)
5 G
C(11)
C(10)
O(4)
C(13)
C(14)
C(3)
C(7)
O(2)
C(8)
C(9)
Fig. 3. Molecular structure of 2,5ꢀdi(tertꢀbutyl)ꢀ3,4ꢀdioxocycloꢀ
hexaꢀ1,5ꢀdienyl methacrylate 2b.
Fig. 4. The ESR spectrum of the chelate oꢀsemiquinone complex
of manganese tetracarbonyl 3.

1218
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 6, June, 2012
Shurygina et al.
hydroxyꢀpꢀbenzoquinone (1)12 and methacryloyl chloride20 were
obtained according to the known procedures.
electron with the magnetic isotope 55Mn (N = 1.387;
I = 5/2; 100%)16 of one manganese atom and one proton
at position 5 of the semiquinone ring. The value gi = 2.0035
and the values of the HFI constants ai(55Mn) = 0.730 mT,
ai(H) = 0.320 mT are in good agreement with the literaꢀ
ture data for the known oꢀsemiquinone complexes, substiꢀ
tuted at position 4 3,6ꢀdi(tertꢀbutyl)ꢀoꢀbenzoquinone deꢀ
rivatives.17,18
In conclusion, we synthesized promising derivatives of
oꢀ and pꢀbenzoquinone containing methacrylate substituꢀ
ents and showed that the oꢀquinone fragment of oꢀbenzoꢀ
quinone methacrylate can serve as a ligand in the syntheꢀ
sis of coordination compounds.
Compounds 2a,b. An excess of LiOH was added to a solution
of 3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoquinone (1) (5 g) in
tetrahydrofuran (50 mL) with stirring. The formation of the salt
was accompanied by the change in color of the reaction mixture
from yellow to saturated violet. The consumption of the starting
quinone in the mixture was monitored spectrophotometrically
based on the disappearance of the absorption band in the region
400 and 580 nm and arising of an absorption band at max = 550 nm.
An excess of LiOH was filtered off, the solvent was evaporated.
For the preparation of the tetrabutylammonium salt, tetrabutylꢀ
ammonium bromide (2 g) was added to a solution of the lithium
salt (1.5 g) in THF (20 mL). The methacrylation reaction of the
2ꢀhydroxyꢀ3,6ꢀdi(tertꢀbutyl)ꢀpꢀbenzoquinone salts was perꢀ
formed according to the procedure described earlier.10,11 To
accomplish this, 3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀhydroxyꢀpꢀbenzoquinone
salt (1 g) was dissolved in a solvent (acetonitrile, THF, benzene,
50 mL). A solution of methacryloyl chloride (a 1.5 molar excess
with respect to the salt) was added on stirring using a dropping
funnel. After the reaction was complete, the mixture was washed
with water and extracted with diethyl ether. Further, the reacꢀ
tion products were isolated by preparative column chromatoꢀ
graphy (silica gel 0.2—0.5 mm, eluent hexane—diethyl ether
(20 : 1)). The first yellow fraction contained 2,5ꢀdi(tertꢀbutyl)ꢀ
3,6ꢀdioxocyclohexaꢀ1,4ꢀdienyl methacrylate (2a), the second
claretꢀcolored fraction contained 2,5ꢀdi(tertꢀbutyl)ꢀ3,4ꢀdioxoꢀ
cyclohexaꢀ1,5ꢀdienyl methacrylate (2b). The overall yield of the
products was 90—95% calculated based on 3,6ꢀdi(tertꢀbutyl)ꢀ2ꢀ
hydroxyꢀpꢀbenzoquinone salt. The physicochemical data of the
reaction products are given below.
Experimental
NMR spectra were recorded on a Bruker Avance DPXꢀ200
spectrometer (1H, 200 MHz; 13C, 50 MHz) using SiMe4 as an
internal standard. ESR spectra were recorded on a Bruker ER
200DꢀSRC spectrometer equipped with an ER 4105 DR double
resonator with an operational frequency of 9.5 GHz. IR spectra
were recorded on a FSMꢀ1201 Fourierꢀtransform IR spectroꢀ
meter (Russia) and on a Specord Mꢀ40 spectrometer. HPLC
analysis was performed on a Knauer liquid chromatograph with a UV
spectrophotometer as a detector ( = 254 nm); a stainless steel
column (200×6 mm) with the Silasorb SPH 600 sorbent (Lacheꢀ
ma, Czech Republic) 5 m; hexane—THF in the ratio 50 : 1 was
a carrier phase, the flow rate of the eluent was 1.5 mL min–1
.
Quantum chemical calculations were performed in the
GAUSSIAN03 program package using the DFT method (the
B3LYP functional with the 6ꢀ311+G(d,p) basis). The absence of
imaginary vibration frequencies confirmed a stationary characꢀ
ter of the calculated structures. Solvents were purified and dried
according to the standard procedures.19 3,6ꢀDi(tertꢀbutyl)ꢀ2ꢀ
2,5ꢀDi(tertꢀbutyl)ꢀ3,6ꢀdioxocyclohexaꢀ1,4ꢀdienyl methꢀ
acrylate (2a), yellow crystals, m.p. 82—84 C. Found (%):
C, 71.12; H, 7.89. C18H24O4. Calculated (%): C, 71.03; H, 7.95.
IR (Nujol), /cm–1: 567, 628, 719, 736, 806, 864, 908, 940, 955,
987, 1010, 1115, 1142, 1197, 1229, 1258, 1299, 1328, 1369, 1378,
1
1463, 1486, 1602, 1638, 1658, 1670, 1740. H NMR (CDCl3,
Table 2. Selected bond distances (d) and bond angles () in the structures of pꢀ and oꢀbenzoquinone
methacrylates 2a and 2b
Parameter
Value
Parameter
Value
Compound 2a
Compound 2b
Bond distance
d/Å
Bond distance
d/Å
С(1)—О(1)
С(4)—О(2)
С(5)—О(3)
С(15)—О(3)
С(15)—О(4)
С(1)—С(2)
С(2)—С(3)
С(3)—С(4)
С(4)—С(5)
С(5)—С(6)
С(1)—С(6)
1.225(2)
1.217(2)
1.393(2)
1.376(2)
1.199(2)
1.472(2)
1.338(2)
1.488(2)
1.511(3)
1.335(2)
1.500(3)
С(1)—О(1)
С(2)—О(2)
С(4)—О(3)
С(11)—О(3)
С(11)—О(4)
С(1)—С(2)
С(2)—С(3)
С(3)—С(4)
С(4)—С(5)
С(5)—С(6)
С(1)—С(6)
1.209(2)
1.213(2)
1.395(2)
1.365(2)
1.192(2)
1.565(2)
1.475(2)
1.343(2)
1.463(2)
1.336(2)
1.474(2)
Bond angle
/deg
Bond angle
/deg
С(4)—С(5)—О(3)—С(15)
70.0
С(5)—С(4)—О(3)—С(11)
О(1)—С(2)—С(2)—О(2)
85.5
15.4

Benzoquinone methacrylates
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 6, June, 2012
1219
400 MHz), : 1.26 (s, 9 H, But); 1.34 (s, 9 H, But); 2.05 (s, 3 H,
Me); 5.82—5.83 (m, 1 H, CH2=); 6.32 (s, 1 H, CH2=); 6.50 (s, 1 H,
H(5)). UV, max/nm (/L mol–1 cm–1): 310 (580), 327 (590),
420 (140). The Xꢀray crystallographic data are given in Table 2.
2,5ꢀDi(tertꢀbutyl)ꢀ3,4ꢀdioxocyclohexaꢀ1,5ꢀdienyl methacrylꢀ
ate (2b), claretꢀcolored crystals, m.p. 90—92 C. Found (%):
C, 71.09; H, 7.97. C18H24O4. Calculated (%): C, 71.03; H, 7.95.
IR (Nujol), /cm–1: 558, 628, 646, 724, 809, 885, 905, 946, 967,
1016, 1060, 1106, 1150, 1179, 1203, 1226, 1282, 1322, 1366,
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1
1379, 1463, 1588, 1626, 1655, 1678, 1728. H NMR (CDCl3,
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Me); 5.88 (s, 1 H, CH2=); 6.32 (s, 1 H, CH2=); 6.40 (s, 1 H,
H(5)). UV, max/nm (/L mol–1 cm–1): 400 (2260), 558 (50).
Manganese tetracarbonyl chelate oꢀsemiquinone complexes
with 2b were generated in a toluene solution of oꢀquinone and
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Compound 2a. The crystal size 0.33×0.33×0.11 mm; molecꢀ
ular formula C18H24O4, molecular weight 304.37; a = 14.187(2) Å,
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Ser. Khim., 1980, 2707 [Bull. Acad. Sci. USSR, Div. Chem.
Sci. (Engl. Transl.), 1980, 39, 1883].
b = 10.3436(15) Å, c = 12.0454(15) Å,  = 90,  = 102.456(3),
3
 = 90, V = 1726.0(4) Å , the space group P21/c, Z = 4; dcalc
=
= 1.171 g cm–3,  = 0.082 mm–1, 2 = 54; there were measured
10039 reflections, from them 3666 were independent (Rint
=
= 0.0623), R1 = 0.0565 (I > 2(I)), wR2 = 0.1148 (on all the data).
Compound 2b. The crystal size 0.45×0.32×0.14 mm; molecular
formula C18H24O4, molecular weight 304.37; a = 11.1682(11) Å,
b = 11.9020(12) Å, c = 14.0549(14) Å,  = 14.0549(14),  =
3
= 89.500(2),  = 77.607(2), V = 1693.3(3) Å , the space group
Pꢀ1, Z = 4; dcalc = 1.194 g cm–3,  = 0.083 mm–1, 2 = 54;
there were measured 10975 reflections, from them 7331 were
independent (Rint = 0.0236), R1 = 0.0575 (I > 2(I)), wR2 =
= 0.1275 (on all the data).
The structures of 2a,b were solved by direct method and
refined by the least squares method on F2 in anisotropic apꢀ
hkl
proximation for all the nonhydrogen atoms and the hydrogen
atoms of the CH2 groups. All other hydrogen atoms were placed
into geometrically calculated position and refined isotropically
using the riding model. All the calculation were performed using
the SHELXTL program package.21 The absorption was allowed
for using the SADABS program.22 The main bond distances and
bond angles are given in Table 2. The structures were deposited
with the Cambridge Structural Database (CCDC № 823636 (2a)
and 823637 (2b)); they are available at www.ccdc.cam.ac.uk/
conts/retrieving.html.
18. G. A. Abakumov, V. K. Cherkasov, K. G. Shalnova, I. A.
Teplova, G. A. Razuvaev, J. Organomet. Chem., 1982,
236, 333.
19. K. Weygand, G. Hilgetag, Organischꢀchemische experimenꢀ
tierkunst, Leipzig, 1970.
20. J. Gordon, R. A. Ford, The Chemist´s Companion, A Wileyꢀ
Intercience Publication John Wiley and Sons, New
York—London—Sydney—Toronto, 1972, 541 pp.
21. G. M. Sheldrick, SHELXTL v. 6.12, Structure Determination
Software Suite, Bruker AXS, Madison (WI, USA), 2000.
22. G. M. Sheldrick, SADABS v. 2.01, Bruker/Siemens Area Deꢀ
tector Absorption Correction Program, Bruker AXS, Madison,
Wisconsin, USA, 1998.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 10ꢀ03ꢀ00788ꢀa,
11ꢀ03ꢀ97040ꢀr_povolzh´e_a, 11ꢀ03ꢀ12184ꢀofi_m, and
12ꢀ03ꢀ01092ꢀa), the Council on Grants at the President
of the Russian Federation (Program of State Support for
Leading Scientific Schools of the Russian Federation,
Grant NShꢀ1113.2012.3), and the State Contract No. Pꢀ839.
References
1. S. R. Batten, S. M. Neville, D. R. Turner, Coordination Polyꢀ
mers: Design, Analysis and Application, RSC Publishing, Camꢀ
bridge, 2009.
Received May 17, 2011;
in revised form March 14, 2012