Controlled polymerization of functional monomers and synthesis of block copolymers using a β-phosphonylated nitroxide

Article abstract of DOI:10.1021/ma0260086

4-Vinylpyridine (4VP) and N,N-dimethylacrylamide (DMAA) were polymerized in a controlled manner using a β-phosphorylated nitroxide (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl-propyl) nitroxide, commonly designated as DEPN) as a control agent. Compared to the results that had previously been reported for the nitroxide-mediated radical polymerization (NMRP) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), the polymerization of 4VP was much faster and very well controlled up to higher monomer conversions. Unlike 4VP, the controlled radical polymerization of DMAA using different types of nitroxides had so far remained limited to a very low conversion range (typically inferior to 10%). The use of DEPN gave rise to a very significant improvement of the NMRP of DMAA by providing a good control up to high conversion (approximately 60%). For the first time, the ability of DEPN to control the homopolymerization of DMAA even at high conversion allowed the synthesis of poly(DMAA-b-4VP) block copolymers with a hydrophilic poly(DMAA) block whichw as longer than the poly(4VP) block. This particular feature should fairly improve the hydrosolubility of the derived amphiphilic cationic polymers, which can be obtained by simple quaternization of the former block copolymers, and extend the scope of their applications.

Full text of DOI:10.1021/ma0260086

Macromolecules 2003, 36, 2235-2241
2235
Controlled Polymerization of Functional Monomers and Synthesis of
Block Copolymers Using a â-Phosphonylated Nitroxide
T. Dia z,† A. F isch er ,*,† A. J on qu ie`r es,‡ A. Br em billa ,† a n d P . Loch on ‡
Equipe de Chimie Physique Organique et Colloı¨dale, Unite´ Mixte de Recherche CNRS-UHP 7565,
Universite´ Henri Poincare´-Nancy 1, B.P. 239-54506 Vandoeuvre-les-Nancy Cedex, France, and
Laboratoire de Chimie Physique Macromole´culaire, Unite´ Mixte de Recherche CNRS-INPL 7568,
Groupe ENSIC, 1, rue Grandville-B.P. 451-54001 Nancy Cedex, France
Received December 27, 2002; Revised Manuscript Received February 6, 2003
ABSTRACT: 4-Vinylpyridine (4VP) and N,N-dimethylacrylamide (DMAA) were polymerized in
a
controlled manner using a â-phosphonylated nitroxide (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl-
propyl) nitroxide, commonly designated as DEPN) as a control agent. Compared to the results that had
previously been reported for the nitroxide-mediated radical polymerization (NMRP) with 2,2,6,6-
tetramethylpiperidine-1-oxyl (TEMPO), the polymerization of 4VP was much faster and very well
controlled up to higher monomer conversions. Unlike 4VP, the controlled radical polymerization of DMAA
using different types of nitroxides had so far remained limited to a very low conversion range (typically
inferior to 10%). The use of DEPN gave rise to a very significant improvement of the NMRP of DMAA by
providing a good reaction control up to high conversion (approximately 60%). For the first time, the ability
of DEPN to control the homopolymerization of DMAA even at high conversion allowed the synthesis of
poly(DMAA-b-4VP) block copolymers with a hydrophilic poly(DMAA) block which was longer than the
poly(4VP) block. This particular feature should fairly improve the hydrosolubility of the derived
amphiphilic cationic polymers, which can be obtained by simple quaternization of the former block
copolymers, and extend the scope of their applications.
In tr od u ction
NMRP. Indeed, whereas styrene and acrylate deriva-
tives have become regularly used species, the polymer-
ization of other monomers in the presence of nitroxides
still remains uninvestigated in many cases.
We had already reported the successful polymeriza-
tion of 3-vinylpyridine37,38 and of 4-vinylpyridine36 in the
presence of TEMPO, but our results concerning the
polymerization of N,N-dimethylacrylamide (DMAA) us-
ing the same nitroxide were still to be improved as
regards reaction control and macromolecular polydis-
persity.39 Nevertheless, a series of poly(1-hexadecyl-4-
vinylpyridinium bromide-b-N,N-dimethylacrylamide)s
had been obtained and had revealed original amphi-
philic properties in aqueous medium.40
The synthesis of that series of block copolymers had
required the preparation and characterization of a poly-
(4-vinylpyridine) first block whose polydispersity was
low, followed by the chain extension of that macro-
initiator using DMAA as a comonomer. Although TEMPO
provided very satisfactory results with 4-vinylpyridine,
the major problem at that time was the poor control of
the polymerization of N,N-dimethylacrylamide allowed
by TEMPO at high conversion.39 Therefore, the synthe-
sis of block copolymers presenting a poly(DMAA) second
block with a wide length range from a TEMPO-
terminated poly(4VP) macroinitiator was seriously im-
peded when DMAA was used as the comonomer. Con-
sequently, in the previous series of amphiphilic macro-
molecules, the proportion of DMAA units could not
exceed 40 mol %.
Yet, there was no doubt that block copolymers with a
high proportion of hydrophilic DMAA units would
certainly lead to a much improved solubility of the
derived amphiphilic polymers in aqueous medium and,
thus, enable to overcome one of the limitations of the
amphiphilic block copolymers of the former series for
potential applications.
Because of its ability to lead to macromolecules with
a well-defined structure, nitroxide-mediated radical
polymerization (NMRP) has now been triggering inter-
est for almost 10 years.1-17 Using this new type of
reaction, it is possible to synthesize polymers and block
copolymers with much narrower molecular weight dis-
tributions than those obtained with conventional radical
polymerization and under conditions that are far more
convenient than those involved in ionic polymerizations.
A lot of the pionnering works that were conducted in
this field dealt with the mechanism of NMRP and,
consequently, used styrene as a typical monomer for
their investigations. 2,2,6,6-Tetramethylpiperidine-1-
oxyl (TEMPO) was regularly chosen as a capping agent,
before new nitroxides progressively appeared to allow
the controlled polymerization of more monomers.18-35
In all cases, the basic scheme of the reaction involves
the thermally reversible trapping of the active polymeric
chain end by a stable nitroxide radical. The high
proportion of the obtained dormant chains is likely to
strongly limit transfer and termination reactions, which
accounts for the adjective “pseudo-living” that is some-
times improperly used to designate NMRP, as under-
lined by Matyjaszewski.7
In our laboratories, this type of polymerization has
now been used for 5 years with a view to synthesizing
particular block copolymers that are precursors for
amphiphilic macromolecules.36-40 Using nonconven-
tional monomers, such as the ones that are employed
in our research, systematically requires a comprehen-
sive study of the behavior of the latter as regards
† Universite´ Henri Poincare´-Nancy 1.
‡ Laboratoire de Chimie Physique Macromole´culaire.
* Corresponding author: Tel 0033(0)383684340; Fax 0033(0)-
383684322; e-mail Arnaud.Fischer@lesoc.uhp-nancy.fr.
10.1021/ma0260086 CCC: $25.00 © 2003 American Chemical Society
Published on Web 03/11/2003

2236 Diaz et al.
Sch em e 1. N-ter t-Bu tyl-N-
Macromolecules, Vol. 36, No. 7, 2003
(1-d ieth ylp h osp h on o-2,2-d im eth ylp r op yl) Nitr oxid e,
Com m on ly Design a ted a s DEP N
Aiming at synthesizing the same type of macromol-
ecules but, this time, with a higher proportion of DMAA
units, we reversed the order of the steps involved in the
synthetic pathway. Thus, in the new synthesis scheme,
DMAA was homopolymerized first. The nitroxide-
terminated poly(DMAA) was then used as a macro-
initiator and chain-extended with 4VP, as the poly-
merization of 4VP was much easier to control than that
of DMAA. The first step obviously required a nitroxide
radical which was likely to control the polymerization
of DMAA up to high conversion values much better than
TEMPO. Considering the progress that had been trig-
gered in the field of NMRP by the introduction of
â-phosphonylated nitroxides,20-24,26-31 N-tert-butyl-
N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide
(DEPN) was chosen as a control agent.
We report here on the behavior of two functional
monomers, i.e., 4VP and DMAA, as regards their
homopolymerization in the presence of either DEPN or
a derived alkoxyamine in comparison with TEMPO. On
the basis of the homopolymerization results, the syn-
thesis of the targeted diblock copolymers is then de-
scribed.
F igu r e 1. Reverse-phase high-pressure liquid chromatograms
of crude (below) and purified (above) DEPN. Eluent: aceto-
nitrile/water (30/70, v/v); flow rate: 2 mL min-1; detection
wavelength: 210 nm.
coupling constants obtained for the mixture of the two dia-
stereoisomers were fully consistent with their chemical struc-
tures. The composition (62/38%) of the diastereoisomer mixture
was determined by 31P NMR. NMR spectra were recorded
using a Bruker DRX 400 spectrometer.
1H NMR (400 MHz, CDCl3): First diastereoisomer: δ (ppm)
) 0.88 (t, 3H, J H-H ) 7.2 Hz), 1.21 (s, 18H), 1.23 (t, 3H, J H-H
) 7.3 Hz), 1.56 (d, 3H, J H-H ) 6.5 Hz), 3.40 (d, 1H, J H-p
)
26.1 Hz), 3.20-4.20 (m, 4H), 5.24 (q, 1H, J H-H ) 6.5 Hz), 7.2-
7.5 (m, 5H). Second diastereoisomer: δ (ppm) ) 0.84 (s, 9H),
1.25 (s, 9H), 1.32 (t, 3H, J H-H ) 7.1 Hz), 1.35 (t, 3H, J H-H
)
7.0 Hz), 1.60 (d, 3H, J H-H ) 6.7 Hz), 3.35 (d, 1H, J H-P ) 26.1
Hz), 3.90-4.50 (m, 4H), 5.00 (q, 1H, J H-H ) 6.5 Hz), 7.10-
7.40 (m, 5H).
13C NMR (100 MHz, CDCl3): First diastereoisomer: δ (ppm)
) 16.45 (2d, J C-P ) 7.2 Hz), 21.45 (s), 28.47 (s), 30.92 (d, J C-P
) 5.5 Hz), 35.61 (d, J C-P ) 6.0 Hz), 58.85 (d, 7.5 Hz), 61.83 (d,
J C-P ) 7.0 Hz), 70.25 (d, J C-P ) 138.8 Hz), 78.63 (s), 127.63
(s), 128.12 (s), 128.16 (s), 143.57 (s). Second diastereoisomer:
δ (ppm) ) 16.53 (d, J C-P ) 7.3 Hz), 17.02 (d, J C-P ) 5.2 Hz),
Exp er im en ta l Section
Syn th esis of N-ter t-Bu tyl-N-(1-d ieth ylp h osp h on o-2,2-
d im eth ylp r op yl) Nitr oxid e (DEP N). DEPN was obtained
by oxidation of 2,2-dimethyl-1-(1,1-dimethylethylamino)pro-
pyldiethylphosphonate with oxone, the synthesis being adapted
from refs 27, 29, and 30. The obtained crude oil was purified
by chromatography on silica (eluent: chloroform/isopropyl
ether, 91/9, v/v). A very careful fractionation led to DEPN
(yield: 40%) with a purity higher than 95% as confirmed by
reverse-phase HPLC analysis (Figure 1) (Chromolith RP18e
Merck column (100 × 4.6 mm); eluent: 30/70, v/v acetonitrile/
water mixture; flow rate: 2 mL min-1; Shimadzu UV detector:
detection at 210 nm).
P r ep a r a tion of th e DEP N-Ba sed Alk oxya m in e N-Ter -
tiobu tyl-N,1-d ieth ylp h osp h on o-2,2-d im eth ylp r op yl-O,1-
p h en yleth ylh yd r oxya m in e (Sty-DEP N). The synthesis of
Sty-DEPN was adapted from refs 22 and 28-30. Copper,
copper bromide, pentamethyldiethylenetriamine (PMDETA),
and (1-bromoethyl)benzene (Aldrich) were used as received.
Dichloromethane was distilled on phosphorus pentoxide and
stored on molecular sieves.
24.34 (s), 28.78 (s), 30.38 (d, J C-P ) 5.7 Hz), 35.88 (d, J C-P
)
6.0 Hz), 59.08 (d, J C-P ) 7.5 Hz), 61.43 (d, J C-P ) 6.5 Hz),
70.17 (d, J C-P ) 138.6 Hz), 85.61 (s), 127.24 (s), 127.38 (s),
128.24 (s), 145.71 (s). 31P NMR (162 MHz, CDCl3): First
diastereoisomer: δ (ppm) ) 24.1, second diastereoisomer: δ
(ppm) ) 25.3.
P olym er iza tion s. Commercial 4VP and DMAA (Aldrich)
were distilled under reduced pressure (40 and 65 °C/1 mmHg,
respectively). 2,2′-Azobis(2-methylpropionitrile) (AIBN, Acros
Organics) was recrystallized from methanol and dried under
vacuum at room temperature.
Typically, monomer, initiator, and nitroxide were introduced
in a Schlenk-type reactor. The mixture was degassed by
several freeze-thaw cycles and finally purged with argon. The
vessel was then immersed in a preheated oil bath (110 °C).
Magnetic stirring and temperature control ((1 °C) were
imposed throughout the reaction. The reaction was stopped
by cooling the flask after different polymerization times.
Excess monomer was evaporated under reduced pressure (0.5
mmHg), and the polymer was recovered as a powder after
careful drying in a vacuum oven (0.5 mmHg) at 60 °C for 48
h. Conversion was determined by weighing the obtained
products. For the bulk polymerization of 4VP with a bicom-
ponent AIBN/DEPN system, the reactor was originally charged
with 4 mL of 4VP, 6.6 mg (4.02 × 10-5 mol) of AIBN, and 21.2
mg (7.21 × 10-5 mol) of DEPN. In the case of the bulk
polymerization of 4VP using the Sty-DEPN alkoxyamine as
an initiator, 16.0 mg (4.01 × 10-5 mol) of alkoxyamine and 4
mL of 4VP were introduced in the reactor. As regards the bulk
polymerization of DMAA with the AIBN/DEPN system, 4 mL
of DMAA was added to 14.4 mg (8.78 × 10-5 mol) of AIBN
and 51.7 mg (1.76 × 10-4 mol) of DEPN. In the case of the
bulk polymerization of DMAA with Sty-DEPN alkoxyamine
In a three-necked round-bottom flask, under a nitrogen
atmosphere, 2.05 g (11 mmol) of (1-bromoethyl)benzene dis-
solved in 50 mL of dichloromethane was added to a mixture
of 3.46 g (20 mmol) of PMDETA, 1.14 g (8 mmol) of copper
bromide, 0.51 g (8 mmol) of copper, 2.94 g of crude DEPN, and
50 mL of dichloromethane. The mixture was left to react for 4
days under vigorous stirring and a nitrogen atmosphere at
room temperature. The solid residue was eliminated by
filtration, and the organic phase was washed with distilled
water until it became limpid. The latter was then dried on
magnesium sulfate, and dichloromethane was removed by
evaporation under reduced pressure at room temperature. The
alkoxyamine was purified by chromatography on silica (eluent:
hexane/diethyl ether, 4/1, v/v). A colorless oil (1.92 g, yield 48%)
was obtained as a mixture of two diastereoisomers. Given the
original purity of crude DEPN, the reaction could be considered
1
quantitative. H NMR and 13C NMR chemical shifts and spin

Macromolecules, Vol. 36, No. 7, 2003
Controlled Polymerization of Functional Monomers 2237
Sch em e 2. Syn th etic P a th w a y To Obta in
P oly(DMAA-b-4VP ) Am p h ip h ilic Block Cop olym er s
F igu r e 2. Bulk polymerization of 4VP at 110 °C; ln([M]0/[M])
vs time. System I (O): [AIBN]0 ) 10-2 mol L-1; [DEPN]0/
[AIBN]0 ) 1.8. System II ([): [alkoxyamine]0 ) 10-2 mol L-1
.
in the presence of an excess DEPN, 4 mL of DMAA was used
along with 35.1 mg (8.80 × 10-5 mol) of Sty-DEPN and 17.1
mg (5.82 × 10-5 mol) of DEPN.
The copolymerization procedure was the same as the one
used for homopolymerizations. As for the original amounts, 2
g (7.87 × 10-5 mol) of DEPN-terminated poly(DMAA) used as
a macroinitiator was added to 9.3 mL of 4VP. The features of
the macroinitiator were as follows: Mn ) 25 400 g mol-1; Mw/
Mn ) 1.23.
Molecu la r Weigh t Det er m in a t ion . The average molar
weights of the polymers were determined by size exclusion
chromatography (SEC). Prior to any experiment, the polymers
were left to dissolve overnight in N,N-dimethylformamide
(Aldrich, HPLC grade, 99.9+%), which was also used as an
eluent (elution rate: 1 mL min-1). Before injection, the solu-
tions were filtered through PTFE membranes (Alltech, average
pore diameter: 200 nm). The temperature was maintained at
40 °C during all SEC experiments. Measurements were
performed on a Waters device equipped with a Styragel HR4
(7.8 × 300 mm) column (103-5 × 106 g/mol). The system had
previously been calibrated with poly(2-vinylpyridine) stand-
ards (Fluka) and also with polystyrene standards (Altergen,
Schiltigheim, France) as a comparison. Sample detection was
performed using a Waters 410 differential refractometer. The
chromatograms were then processed with the Millenium
software.
F igu r e 3. Bulk polymerization of 4VP at 110 °C; Mn vs
conversion. System I (O): [AIBN]0 ) 10-2 mol L-1; [DEPN]0/
[AIBN]0 ) 1.8. System II ([): [alkoxyamine]0 ) 10-2 mol L-1
.
These very promising results represented a first step
toward the synthesis of poly(DMAA-b-4VP) new block
copolymers which would combine significant molecular
weights for both blocks (up to Mn ) 20 000 g mol-1) with
a wide composition range.
Resu lts a n d Discu ssion
Hom op olym er iza tion of 4-Vin ylp yr id in e. It is
commonly admitted that a nitroxide-mediated poly-
merization can be considered controlled as soon as the
number of propagating free polymeric radicals is con-
stant and, at the same time, the molar weight of the
obtained macromolecules is proportional to monomer
conversion.7,10 In the case of 4VP, Figures 2 and 3 gather
the results obtained for the plots of both ln([M]0/[M])
vs time and Mn vs conversion, where [M]0, [M], and Mn
respectively stand for monomer original and current
concentration in the bulk and polymer number-average
molar weight. It must here be reminded that a linear
plot of ln([M]0/[M]) as a function of time guarantees a
constant number of propagating polymeric radicals, as
shown by integration of eq 1 which describes monomer
consumption:
As we aimed at preparing block copolymers with both
4VP and DMAA units, our first objective consisted in
making sure that DEPN was able to control the homo-
polymerization of each of these monomers.
Two different systems were investigated for each
monomer, i.e., a bimolecular one (system I), in which
the polymerization was carried out in the presence of
DEPN along with AIBN as an initiator, and a mono-
molecular one (system II), in which an alkoxyamine
derived from DEPN was the only species to both initiate
and control the reaction.
Whatever the used system and monomer, DEPN
enabled to control the homopolymerization of 4VP and
DMAA with polymerization rates that were much
higher than those observed with TEMPO. Contrary to
4VP, DMAA had never been polymerized in a controlled
manner by NMRP up to high conversion so far. Com-
pared to former nitroxides that had been reported for
the NMRP of DMAA,25,39,41 DEPN clearly provided a
breakthrough for the polymerization of this particular
monomer by extending the range of monomer conversion
for which the polymerization was controlled from 10%
to almost 60%.
-d[M]/dt ) kp[R•][M]
(1)
where kp and [R•] respectively stand for the propagation
rate constant of the polymerization and the concentra-
tion in propagating polymeric radicals in the bulk.
For the bimolecular system (system I) as well as for
the monomolecular system (system II), the two graphic

2238 Diaz et al.
Macromolecules, Vol. 36, No. 7, 2003
Ta ble 1. Bu lk P olym er iza tion of 4VP a t 110 °C Usin g
System I; [AIBN]0 ) 10-2 m ol L-1; [DEP N]0/[AIBN]0 ) 1.8
Ta ble 2. Bu lk P olym er iza tion of 4VP a t 110 °C Usin g
System II; [Alk oxya m in e]0 ) 10-2 m ol L-1
Mn (103 g/mol)
(poly(2VP)
standards)
Mw/Mn
(poly(2VP)
standards)
Mn (103 g/mol)
(poly(2VP)
standards)
Mw/Mn
(poly(2VP)
standards)
theor Mn
theor Mn
conv
(103 g/mol)
conv
(103 g/mol)
0.25
0.26
0.28
0.30
0.35
0.38
0.40
0.42
0.48
12.2,a 13.4b
12.7,a 14.2b
13.7,a 15.4b
14.6,a 16.2b
17.0,a 18.7b
19.0,a 20.7b
19.8,a 21.8b
20.6,a 23.0b
23.0,a 26.0b
13.6
14.9
17.2
17.1
20.9
22.5
24.0
24.2
27.1
1.12
1.12
1.10
1.11
1.11
1.09
1.13
1.20
1.21
0.25
0.31
0.40
0.45
0.49
0.54
24.6
30.6
38.7
44.1
47.4
52.0
26.5
32.2
39.7
49.0
47.5
60.6
1.36
1.28
1.27
1.22
1.31
1.15
would have antagonistic effects on molecular weights.
Hence, both effects would have a tendency to compen-
sate.
However, all these results obviously need considering
while keeping in mind that the poly(2VP) standards
used to characterize the samples by SEC do not exactly
correspond to poly(4VP) macromolecules (even though
they are very closely related), which induces an incer-
titude as regards molar weight characterization.
a
Considering the original AIBN concentration as determining.
Considering the original DEPN concentration as determining.
b
criteria required to ascertain a controlled polymerization
were fulfilled, as proved by the corresponding plots
(Figures 2 and 3). As concerns the kinetic plot (Figure
2), a positive shift at the very beginning of the poly-
merization was observed with the bimolecular system,
which seems to indicate a slightly poorer reaction
control early on, corresponding to a possible higher
radical concentration. However, Figure 3 confirms the
control of the number of growing chains throughout the
polymerization.
As shown in Table 2, when homopolymerized in the
presence of system II, 4VP yields molar weights which
are really close to the theoretical expectations. (In this
case, the [DEPN]0/[initiator]0 ratio is equal to 1 as the
same molecule plays the role of both the initiator and
the capping agent.) Nevertheless, the polydispersity
indices turned to be a little higher than those obtained
with system I. Moreover, the kinetic comparison be-
tween systems I and II (Figure 2) shows that the
polymerization rate is twice as low with a bimolecular
system as it is with an alkoxyamine. Both of the former
observations are unusual so far but might be interpreted
again by considering an initiator efficiency that is
inferior to 1 for the bimolecular system. In that case,
the excess of nitroxide with respect to the active
initiating radicals would be responsible for a much
slower kinetics and a stronger homogeneity of the
molecular weight distribution, which is in very good
agreement with former observations made on the sys-
tems styrene/DEPN and n-butyl acrylate/DEPN sys-
tems.17,23,27,31,43
H om op olym er iza t ion of N,N-Dim et h yla cr yl-
a m id e. Contrary to 4VP, DMAA had never been poly-
merized in a controlled manner up to high conversions
so far. Systems I and II were used here as well. As
already observed during our former investigations with
TEMPO,36 the NMRP of DMAA is much slower than
that of 4VP. With the bimolecular system (system I),
an original AIBN initial concentration equal to 10-2 mol
L-1 along with a [DEPN]0/[AIBN]0 ratio of 1.8 (the latter
conditions corresponding to those encountered while
working on 4VP) was not sufficient to guarantee a
controlled reaction. It can be supposed that, with too
little AIBN, chemical initiation becomes overcome by
thermal radical generation, which prevents satisfactory
control. Our experiments were then conducted with an
initial AIBN concentration in the bulk which was equal
to 2.2 × 10-2 mol L-1 and a [DEPN]0/[AIBN]0 ratio equal
to 2. These conditions enabled a good control of the
radical polymerization of DMAA up to high conversion
(almost 60%) (Figures 4 and 5, Table 3). Accordingly,
the alkoxyamine only controlled the polymerization of
DMAA provided additional free DEPN was introduced
in the bulk. The latter observation, along with the
required initial nitroxide excess involved in several
polymerization systems, is consistent with the role
played by excess nitroxide in the field of NMRP, as long
Compared to the former results36 obtained with
TEMPO for 4VP, the reaction was much faster with
DEPN even at a much lower temperature (i.e., 110 and
138 °C for DEPN and TEMPO, respectively). The in-
crease in polymerization rate with the acyclic nitroxide
DEPN was expected from the faster rate of homolysis
of the dormant species obtained by coupling with acyclic
rather than cyclic nitroxides, as shown for instance by
Marque et al.42 and Kazmaier et al.4 When a bimolecu-
lar system DEPN/AIBN was used, the polymerization
was also very well controlled (Figures 2 and 3). It must
be emphasized that the polymerization control was well
achieved for a [DEPN]0/[AIBN]0 ratio which was equal
to 1.8 (i.e., inferior to 2).
Table 1 deals with the homopolymerization of 4VP in
the presence of the bimolecular system DEPN/AIBN
(system I) and compares the experimental values of the
number-average molar weights of the obtained polymers
with theoretical values worked out when considering
either the initiator (AIBN) or the capping agent (DEPN)
as the species whose original concentration determines
the number of chains. According to the results gathered
in Table 1, it seems that DEPN is responsible for the
actual number of macromolecules and, consequently,
their molar weights. In good agreement with former
polymerization data obtained with DEPN in different
systems,23,27,31,43 the experimental molecular weights
were usually slightly higher than the theoretical ones.
An initiator efficiency inferior to 1 might account for
the difference between theoretical and experimental
molar weights for system I and would also account for
the low amount of DEPN which was nevertheless
sufficient to control the polymerization in the bimolecu-
lar system. An irreversible decomposition of DEPN
throughout the polymerization, which has been reported
to occur at elevated temperatures,43 would also produce
the same effects on molecular weights.
Thermal polymerization, which is sometimes men-
tioned as a key phenomenon in NMRP, does not seem
to occur in a significant way although its contribution
is certainly difficult to assess because thermal poly-
merization and a lowered efficiency of the initiator

Macromolecules, Vol. 36, No. 7, 2003
Controlled Polymerization of Functional Monomers 2239
Ta ble 3. Bu lk P olym er iza tion of DMAA a t 110 °C Usin g
System s I a n d II
Mn (103 g/mol)
(poly(2VP)
standards)
Mw/Mn
(poly(2VP)
standards)
theor Mn
conv
(103 g/mol)
0.18a
0.25a
0.38a
0.47a
0.57a
0.09b
0.22b
0.27b
0.36b
0.38b
0.43b
0.48b
0.64b
3.9,c 3.9d
3.1
4.3
8.2
10.2
12.6
3.7
7.6
10.0
9.8
11.4
11.9
11.5
15.7
1.37
1.45
1.26
1.27
1.39
1.41
1.31
1.21
1.37
1.31
1.35
1.38
1.54
5.4,c 5.4d
8.3,c 8.3d
10.4,c 10.4d
12.7,c 12.7d
3.9,c 2.4d
9.6,c 5.8d
11.6,c 7.0d
15.8,c 9.5d
16.3,c 9.8d
19.3,c 11.6d
21.2,c 12.8d
28.4,c 17.1d
F igu r e 4. Bulk polymerization of DMAA at 110 °C; ln([M]0/
[M]) vs time. System I (O): [DEPN]0/[AIBN]0 ) 2; [AIBN]0 )
2.2 × 10-2 mol.L-1; overall nitroxide concentration ) 4.4 ×
10-2 mol L-1. System II ([): [alkoxyamine]0 ) 2.2 × 10-2 mol
L-1; [excess free DEPN]0 ) 0.66[alkoxyamine]0; overall nitrox-
a
[DEPN]0/[AIBN]0 ) 2; [AIBN]0 ) 2.2 × 10-2 mol L-1; overall
nitroxide concentration ) 4.4 × 10-2 mol L-1
.
[Alkoxyamine]0 )
b
2.2 × 10-2 mol L-1; [excess free DEPN]0 ) 0.66[alkoxyamine]0;
ide concentration ) 3.5 × 10-2 mol L-1
.
overall nitroxide concentration ) 3.5 × 10-2 mol L-1
.
c Considering
the original concentration of the initiating species as determining.
d
Considering the original overall nitroxide concentration (DEPN
+ alkoxyamine) as determining.
Ta ble 4. Com p a r ison betw een th e Exp er im en ta lly
Obta in ed Va lu es of Both Mola r Weigh ts a n d
P olyd isp er sities Dep en d in g on th e Sta n d a r d s Used To
Ca libr a te th e SEC Colu m n
Mn (103 g/mol)
(polystyrene
standards)
Mn (103 g/mol)
(poly(2VP)
standards)
Mw/Mn
(polystyrene
standards)
Mw/Mn
(poly(2VP)
standards)
Poly(4VP)
44.7
48.0
52.3
53.8
59.3
60.5
61.2
65.7
71.7
73.0
81.4
92.9
98.4
105.2
123.8
13.6
14.9
17.2
17.8
20.9
21.1
24.2
24.4
27.1
28.4
32.2
39.7
44.3
47.5
60.6
1.05
1.05
1.04
1.04
1.05
1.05
1.14
1.03
1.08
1.05
1.12
1.12
1.11
1.15
1.09
1.12
1.12
1.10
1.10
1.11
1.14
1.20
1.09
1.21
1.13
1.28
1.27
1.23
1.31
1.15
F igu r e 5. Bulk polymerization of DMAA at 110 °C; Mn vs
conversion. System I (O): [DEPN]0/[AIBN]0 ) 2; [AIBN]0 ) 2.2
× 10-2 mol L-1; overall nitroxide concentration ) 4.4 × 10-2
mol L-1. System II ([): [alkoxyamine]0 ) 2.2 × 10-2 mol L-1
;
[excess free DEPN]0 ) 0.66[alkoxyamine]0; overall nitroxide
concentration ) 3.5 × 10-2 mol L-1
.
underlined by Georges et al.5 and more recently by
Lacroix-Desmazes et al.43 This finally led us to work
with an alkoxyamine original concentration equal to 2.2
× 10-2 mol L-1 and a 66% DEPN molar excess, which
means that the potential DEPN overall concentration
Poly(DMAA)
3.7
4.3
5.3
7.0
7.7
8.6
10.0
11.9
13.3
20.7
22.9
26.2
30.8
32.3
35.1
37.9
42.8
46.5
1.13
1.19
1.12
1.11
1.09
1.13
1.07
1.13
1.15
1.41
1.45
1.36
1.33
1.31
1.39
1.21
1.35
1.43
(free DEPN + alkoxyamine) was 3.65 × 10-2 mol L-1
.
The obtained Mn vs conversion plot (Figure 5) is
consistent with these concentration values: System I,
with a higher original nitroxide concentration, turned
to yield polymers with lower molar weights than system
II for the same conversion.
Compared to former nitroxides that had been reported
for the NMRP of DMAA,25,39,41 DEPN enabled to largely
extend the range of polymerization control (from 10%
to almost 60% conversion). For 57% conversion (after
less than 9 h polymerization) and under the experimen-
tal conditions described in Table 3, the number-average
molecular weight of poly(DMAA) was 12 600 g mol-1
with a polydispersity of 1.39 (poly(2VP) calibration). As
for 4VP, the original nitroxide concentration proved
responsible for the number of growing chains. Indeed,
as shown in Table 3, the experimental number-average
molar weights were closer to the theoretical ones that
had been worked out when considering the initial
overall DEPN concentration (alkoxyamine + free DEPN)
than to those calculated from the original concentration
of the initiating species.
To allow a better comparison of the properties of our
systems with those of others reported in the literature
on the basis of polystyrene standards, the characteristics
of the molar weight distributions of poly(DMAA) and
poly(4VP) were also determined using a polystyrene
standard calibration (Table 4). As expected given the
very different polarities of polystyrene, polyvinylpyri-
dine, and the highly polar eluent (DMF) used for the
SEC analysis, the results concerning poly(4VP) indi-
cated that a polystyrene calibration overestimated 2-3
times the number-average molar weights of poly(4VP)
samples and, at the same time, underestimated their

2240 Diaz et al.
Macromolecules, Vol. 36, No. 7, 2003
Ta ble 5. F ea tu r es of th e Differ en t Cop olym er s Obta in ed
w ith Ea ch Typ e of Nitr oxid e
Mn
molar
molar
nature of (103 g/mol)
Mw/Mn
percentage percentage
the used
(poly(2VP) (poly(2VP)
of 4VP
units
of DMAA
units
nitroxide standards) standards)
DEPNa
25.4
29.6
36.4
39.9
52.2
7.8
7.6
7.3
6.8
6.5
1.23
1.21
1.23
1.23
1.40
1.53
1.61
1.61
1.61
1.55
1.83
1.37
0
15
30
36
51
50
51
53
57
60
68
100
100
85
70
64
49
50
49
47
43
40
32
0
TEMPOb
F igu r e 6. Copolymerization of 4VP at 110 °C using a poly-
(DMAA) macroinitiator (Mn ) 25 400 g mol-1; Mw/Mn ) 1.23);
ln([4VP]0/[4VP]) vs time; [macroinitiator]0 ) 8.5 × 10-3 mol
5.7
3.9
L-1
.
a
Using a poly(DMAA) macroinitiator along with DEPN to
b
copolymerize 4VP. Using a poly(4VP) macroinitiator along with
TEMPO to copolymerize DMAA.
polydispersities. This trend got even worse in the case
of poly(DMAA), for which poly(2VP) and polystyrene
calibrations yielded molar weights that differed by 3-6-
fold, while polydispersity indicesswhich could be re-
garded as satisfactory using polystyrene standardss
dramatically increased when using poly(2VP) standards,
while still remaining below the critical limit of 1.5
obtained for a standard radical polymerization. Fur-
thermore, it must be pointed out that using poly(DMAA)
standards would probably increase such differences.
Although it is well-known that the characterization of
polymers by SEC on the basis of relative calibration is
highly dependent on the standards that are used to
calibrate the column, very little apart from the very
recent paper by Charleux et al.17 has been reported in
the NMRP literature so far about the influence of the
choice of the standards on polydispersity values (which
are among the key factors to assess the controlled
character of any polymerization). Our results clearly
show that, in certain conditions, a SEC analysis based
on a polystyrene calibration (as most commonly reported
in the literature on controlled radical polymerization)
can convey a somewhat idealized assessment of the
molecular weight distribution by overestimating its
homogeneity.
Syn th esis of P oly(DMAA-b-4VP ) Block Cop oly-
m er s. As previously mentioned, TEMPO had already
enabled us to synthesize block copolymers with 4VP and
DMAA units, but the size of the second block (i.e.,
hydrophilic poly(DMAA)) was rather small compared
with that of the first block (i.e., poly(4VP)). Further-
more, if the number-average molar weights of the
obtained macromolecules had appeared satisfactory
when worked out from polystyrene standards, they
turned to appear rather small once poly(2VP) standards
were used to calibrate the SEC column. As regards
polydispersity values, they turned from inferior to 1.5
using a polystyrene calibration to sometimes superior
to 1.5 when obtained from poly(2VP) standards (see this
work) (Table 5).
F igu r e 7. Copolymerization of 4VP at 110 °C using a poly-
(DMAA) macroinitiator (Mn ) 25 400 g.mol-1; Mw/Mn ) 1.23);
Mn vs 4VP conversion; [macroinitiator]0 ) 8.46 × 10-3
mol L-1
.
As shown in Table 5, DEPN led to satisfactory molar
weights for both blocks and also allowed to complete the
range of synthesized copolymers by more hydrophilic
species, which was one of the objectives of this work.
Con clu sion s
The reported results have brought an interesting
insight into nitroxide-mediated radical polymerizations
and have first revealed the good performance of DEPN
for the NMRP of two functional and polar monomers.
The bimolecular system DEPN/AIBN (2/1) as well as
alkoxyamine Sty-DEPN based systems enabled to con-
trol the radical polymerization of N,N-dimethylacryl-
amide (DMAA) and 4-vinylpyridine (4-VP). For both
investigated monomers, and particularly for DMAA, the
progress was really significant as compared with the
results formerly obtained with TEMPO: a 30 °C lower
temperature, much shorter polymerization times (i.e.,
at least 20 times shorter for DMAA), high conversion
for NMRP (even superior to 60%), higher average
molecular weights, etc.
The good control obtained for both radical homo-
polymerizations allowed the consecutive synthesis of
poly(DMAA)-b-poly(4-VP) block copolymers from a poly-
(DMAA) macroinitiator. Even during chain extension,
the control of the radical polymerization of 4VP proved
excellent, and a wide range of well-defined block co-
polymers were eventually obtained. In addition to
covering a much broader composition range than that
formerly obtained with TEMPO, the new family of block
On the other hand, the use of DEPN led to longer
hydrophilic poly(DMAA) blocks with a much better
reaction control. The latter was then used as a macro-
initiator for the chain extension by 4-vinylpyridine
whose polymerization was much easier to control than
that of DMAA. As shown by Figures 6 and 7, the
polymerization of the second block poly(4VP) was also
very well controlled.

Macromolecules, Vol. 36, No. 7, 2003
Controlled Polymerization of Functional Monomers 2241
(22) Matyjaszewski, K.; Woodworth, B. E.; Zhang, X.; Gaynor, S.
G.; Metzner, Z. Macromolecules 1998, 31, 5955-5957.
(23) Benoit, D.; Grimaldi, S.; Finet, J . P.; Tordo, P.; Fontanille,
M.; Gnanou, Y. In Controlled Radical Polymerization; Maty-
jaszewski, K., Ed.; ACS Symposium Series 685; American
Chemical Society: Washington, DC, 1998; pp 225-235.
(24) Grimaldi, S.; Le Moigne, F.; Finet, J . P.; Tordo, P.; Nicol, P.;
Plechot, M.; Gnanou, Y. Eur. Patent 0832902 A2, 1998.
(25) Benoit, D.; Chaplinski, V.; Braslau, R.; Hawker, C. J . J . Am.
Chem. Soc. 1999, 121, 3904-3920.
(26) Benoit, D.; Grimaldi, S.; Robin, S.; Finet, J . P.; Tordo, P.;
Gnanou, Y. J . Am. Chem. Soc. 2000, 122, 5929-5939.
(27) Grimaldi, S.; Finet, J . P.; Le Moigne, F.; Zeghdaoui, A.; Tordo,
P.; Benoit, D.; Fontanille, M.; Gnanou, Y. Macromolecules
2000, 33, 1141-1147.
(28) Couturier, J . L.; Henriet-Bernard, C.; Le Mercier, C.; Tordo,
P.; Lutz, J . F. Patent WO 00/49027,Elf Atochem SA, 24 Aug
2000.
(29) Couturier, J . L.; Guerret, O.; Senninger, T. Patent WO 00/
61544, Elf Atochem SA, 19 Oct 2000.
(30) Le Mercier, C.; Lutz, J . F.; Marque, S.; Le Moigne, F.; Tordo,
P.; Lacroix-Desmazes, P.; Boutevin, B.; Couturier, J . L.;
Guerret, O.; Martschke, R.; Sobek, J .; Fischer, H. In Con-
trolled Radical Polymerization: Progress in ATRP, NMP and
RAFT; Matyjaszewski, K., Ed.; ACS Symposium Series 768;
American Chemical Society: Washington, DC, 2000; pp 108-
122.
copolymers also displayed much higher average molar
weights for both blocks.
Refer en ces a n d Notes
(1) Solomon, D. H.; Rizzardo, E.; Cacioli, P. U.S. Patent 4,581,429,
1986.
(2) Georges, M. K.; Veregin, R. P. N.; Kazmaier, P. M.; Hamer,
G. K. Macromolecules 1993, 26, 2987-2988.
(3) Veregin, R. P. N.; Georges, M. K.; Hamer, G. K.; Kazmaier,
P. M. Macromolecules 1995, 28, 4391-4398.
(4) Kazmaier, P. M.; Moffat, K. A.; Georges, M. K.; Veregin, R.
P. N.; Hamer, G. K. Macromolecules 1995, 28, 1841-1846.
(5) Veregin, R. P. N.; Odell, P. G.; Michalak, L. M.; Georges, M.
K. Macromolecules 1996, 29, 2746-2754.
(6) Fukuda, T.; Terauchi, T.; Goto, A.; Ohno, K.; Tsujii, Y.;
Miyamoto, T.; Kobatake, S.; Yamada, B. Macromolecules
1996, 29, 6393-6398.
(7) Matyjaszewski, K.; Mueller, A. H. E. Polym. Prepr. (Am.
Chem. Soc., Div. Polym. Chem.) 1997, 38, 6-9.
(8) Fischer, H. Macromolecules 1997, 30, 5666-5672.
(9) Georges, M. K.; Veregin, R. P. N.; Daimon, K. In Controlled
Radical Polymerization; Matyjaszewski, K., Ed.; ACS Sym-
posium Series 685; American Chemical Society: Washington,
DC, 1998; pp 170-179.
(10) Matyjaszewski, K. In Controlled Radical Polymerization;
Matyjaszewski, K., Ed.; ACS Symposium Series 685; Ameri-
can Chemical Society: Washington, DC, 1998; pp 2-30.
(11) Fischer, H. J . Polym. Sci., Part A: Polym. Chem. 1999, 37,
1885-1901.
(12) Farcet, C.; Lansalot, M.; Charleux, B.; Pirri, R.; Vairon, J .
P. Macromolecules 2000, 33, 8559-8570.
(13) Fukuda, T.; Goto, A.; Ohno, K. Macromol. Rapid Commun.
2000, 21, 151-165.
(14) Matyjaszewski, K. In Controlled Radical Polymerization:
Progress in ATRP, NMP and RAFT; Matyjaszewski, K., Ed.;
ACS Symposium Series 768; American Chemical Society:
Washington, DC, 2000; pp 2-26.
(31) Lacroix-Desmazes, P.; Lutz, J . F.; Boutevin, B. Macromol.
Chem. Phys. 2000, 201, 662-669.
(32) J ousset, S.; Catala, J . M. Macromolecules 2000, 33, 4705-
4710.
(33) Catala, J . M.; J ousset, S.; Lamps, J . P. Macromolecules 2001,
34, 8654-8656.
(34) Robin, S.; Guerret, O.; Couturier, J . L.; Gnanou, Y. Macro-
molecules 2002, 35, 2481-2486.
(35) Drockenmuller, E.; Catala, J . M. Macromolecules 2002, 35,
2461-2466.
(36) Fischer, A.; Brembilla, A.; Lochon, P. Macromolecules 1999,
32, 6069-6072.
(37) Ding, X. Z.; Fischer, A.; Brembilla, A.; Lochon, P. J . Polym.
Sci., Part A: Polym. Chem. 2000, 38, 3067-3073.
(38) Ding, X. Z.; Fischer, A.; Yang, S.; Wu, P.; Brembilla, A.;
Lochon, P. Eur. Polym. J . 2001, 37, 1561-1569.
(39) Fischer, A.; Brembilla, A.; Lochon, P. Eur. Polym. J . 2001,
37, 33-37.
(15) Lacroix-Desmazes, P.; Lutz, J . F.; Chauvin, F.; Severac, R.;
Boutevin, B. Macromolecules 2001, 34, 8866-8871.
(16) Farcet, C.; Charleux, B.; Pirri, R. Macromolecules 2001, 34,
3823-3826.
(17) Farcet, C.; Belleney, J .; Charleux, B.; Pirri, R. Macromolecules
2002, 35, 4912-4918.
(18) Catala, J . M.; Bubel, F.; Hammouch, S. O. Macromolecules
1995, 28, 8441-8443.
(19) J ousset, S.; Hammouch, S. O.; Catala, J . M. Macromolecules
1997, 30, 6685-6687.
(40) Fischer, A.; Brembilla, A.; Lochon, P. Polymer 2001, 42,
1441-1448.
(20) Grimaldi, S.; Finet, J . P.; Zeghdaoui, A.; Tordo, P.; Benoit,
D.; Gnanou, Y.; Fontanille, M.; Nicol, P.; Pierson, J . F. Polym.
Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1997, 38, 651-
652.
(21) Benoit, D.; Grimaldi, S.; Finet, J . P.; Tordo, P.; Fontanille,
M.; Gnanou, Y. Polym. Prepr. (Am. Chem. Soc., Div. Polym.
Chem.) 1997, 38, 729-730.
(41) Li, D.; Brittain, W. J . Macromolecules 1998, 31, 3852-3855.
(42) Marque, S.; Le Mercier, C.; Tordo, P.; Fischer, H. Macromol-
ecules 2000, 33, 4403-4410.
(43) Lacroix-Desmazes, P.; Lutz, J . F.; Chauvin, F.; Severac, R.;
Boutevin, B. Macromolecules 2001, 34, 8866-8871.
MA0260086