Living anionic polymerization of N-methacryloylazetidine: Anionic polymerizability of N,N-dialkylmethacrylamides

Article abstract of DOI:10.1021/ma901984d

Anionic polymerization of a series of N,N-dialkylmethacrylamides such as TV-methacryloylazetidine (M4), N-methacryloylpyrrolidine (M5), and N-methacryloylpiperidine (M6) was carried out with diphenylmethyllithium (Ph₂CHLi) or diphenylmethylpotassium (Ph₂CHK) in the presence of LiCl or Et₂Zn in THF to clarify the relationship between polymerizability and monomer structure. Poly(M4)s possessing predicted molecular weights and very narrow molecular weight distributions M_wM _n < 1.1) were obtained quantitatively with Ph₂CHLi/LiCl or Ph₂CHK/Et₂Zn at -40 to 0 °C within 24 h. From the polymerizations of M4 at the various temperatures ranging from -40 to -20 °C, the apparent rate constant and the activation energy of the anionic polymerization were determined as follows: In k_p^ap = -6.17 x 10³/r+22.4 Lmol^-1s^-1 and 51 ± 5 kJ mol^-1, respectively. Compared to the previous report on the anionic polymerization of N-methacryloyl-2-methylaziridine (M3), the polymerization rate of M4 was significantly slower and the activation energy was slightly larger, indicating the lower polymerizability of M4. The acryloyl counterpart, N-acryloylazetidine (A4), also underwent the anionic polymerization to afford the well-defined polymer quantitatively. The polymerizations of M5 gave the polymers in 30-77% yields but did not complete even after 1 week at 0 °C. By contrast, no polymer was obtained from the anionic polymerization system of M6 similar to the case of N.N-dimethylmethacrylamide (DMMA). From the experimental results, it was demonstrated that the polymerizability of a series of N,N-dialkylmethacrylamides with cyclic substituents decreased drastically with increasing the ring size from three to six (M3 > M4 > M5M6 = DMMA). The observed relative polymerizability was well correlated with the chemical shifts of vinyl β-carbons for monomers in the ¹³C NMR spectra. The NMR data suggested that the polymerizable M3 and M4 attained effective conjugation between C=C and C=O double bonds, while M5, M6, and DMMA had negligible conjugation effects.

Full text of DOI:10.1021/ma901984d

Macromolecules 2010, 43, 107–116 107
DOI: 10.1021/ma901984d
Living Anionic Polymerization of N-Methacryloylazetidine:
Anionic Polymerizability of N,N-Dialkylmethacrylamides
Takashi Suzuki, Jun-ichi Kusakabe, Keita Kitazawa, Takeshi Nakagawa, Susumu Kawauchi,
and Takashi Ishizone*
Department of Organic and Polymeric Materials, Tokyo Institute of Technology 2-12-1-H-119, Ohokayama,
Meguro-ku, Tokyo 152-8552, Japan
Received September 5, 2009; Revised Manuscript Received November 14, 2009
ABSTRACT: Anionic polymerization of a series of N,N-dialkylmethacrylamides such as N-methacryloyl-
azetidine (M4), N-methacryloylpyrrolidine (M5), and N-methacryloylpiperidine (M6) was carried out with
diphenylmethyllithium (Ph CHLi) or diphenylmethylpotassium (Ph CHK) in the presence of LiCl or Et Zn
2 2 2
in THF to clarify the relationship between polymerizability and monomer structure. Poly(M4)s possessing
predicted molecular weights and very narrow molecular weight distributions (M /M < 1.1) were obtained
w
n
2 2 2
quantitatively with Ph CHLi/LiCl or Ph CHK/Et Zn at -40 to 0 °C within 24 h. From the polymerizations
of M4 at the various temperatures ranging from -40 to -20 °C, the apparent rate constant and the activation
ap
p
3
-1 -1
energy of the anionic polymerization were determined as follows: ln k = -6.17 ꢀ 10 /T þ 22.4 L mol
s
and 51 ( 5 kJ mol- , respectively. Compared to the previous report on the anionic polymerization of
N-methacryloyl-2-methylaziridine (M3), the polymerization rate of M4 was significantly slower and the
activation energy was slightly larger, indicating the lower polymerizability of M4. The acryloyl counterpart,
N-acryloylazetidine (A4), also underwent the anionic polymerization to afford the well-defined polymer
quantitatively. The polymerizations of M5 gave the polymers in 30-77% yields but did not complete even
after 1 week at 0 °C. By contrast, no polymer was obtained from the anionic polymerization system of M6
similar to the case of N,N-dimethylmethacrylamide (DMMA). From the experimental results, it was
demonstrated that the polymerizability of a series of N,N-dialkylmethacrylamides with cyclic substituents
decreased drastically with increasing the ring size from three to six (M3 > M4 > M5 . M6 = DMMA). The
observed relative polymerizability was well correlated with the chemical shifts of vinyl β-carbons for
1
1
3
monomers in the C NMR spectra. The NMR data suggested that the polymerizable M3 and M4 attained
effective conjugation between CdC and CdO double bonds, while M5, M6, and DMMA had negligible
conjugation effects.
2,10-14
Introduction
polymerizability under the various reaction conditions.
In
fact, a number of research groups have reported that N,N-dialkyl-
methacrylamides are difficult to polymerize with the radical or
anionic initiators. The only structural difference between
DMMA and the polymerizable acryloyl counterpart, N,N-di-
methylacrylamide (DMA), is the presence of R-methyl substitu-
The living/controlled polymerizations of polar monomers such
as acrylates and methacrylates, R,β-unsaturated esters, have been
intensely studied under the various conditions from the synthetic
viewpoints and the industrial interest. In fact, the controls on
molecular architectures such as molecular weight, molecular
weight distribution (MWD), and stereoregularity of their
1
1
13
ent on the acryloyl framework. On the basis of H and C NMR
1
5
5
study and MNDO calculations, Kodaira and Hogen-Esch
have suggested that DMMA takes twisted conformation between
vinyl and carbonyl groups probably due to the intramolecular
(
co)polymers are realized in those studies to design the properties
of new functional materials. Similar to the esters, R,β-unsaturated
amides such as acrylamide, methacrylamide, and their N-mono-
alkyl-substituted derivatives readily undergo the vinyl polymer-
steric repulsion between R-methyl or CH = group and N-alkyl
2
2
,3
substituents. The twisted conformation should lead to the re-
duced π-conjugation between CdC and CdO double bonds,
lowering the polymerizability of DMMA significantly.
ization under the radical conditions, while the anionic vinyl
polymerization is often accompanied by the hydrogen transfer
polymerization because of the highly acidic amide hydrogen of
4
As an exception, N-methacryloylaziridine (MAz), a particular
N,N-dialkylmethacrylamide possessing small and highly strained
three-membered aziridine ring, can be polymerized with either
the monomers. On the other hand, it has been reported that N,N-
dialkylacrylamides readily undergo the radical and anionic poly-
5-9
merizations to afford the vinyl polymers.
The formation of
1
6,17
17
radical
or anionic initiators to give vinyl polymers. In the
stable living polymers is also achieved in the anionic poly-
5-8
9
preceding paper, we have also found that N-methacryloyl-2-
methylaziridine (M3), 2-methyl-substituted derivative of MAz,
readily undergoes the vinyl polymerization under the basic
merization
and the group transfer polymerization of various
N,N-dialkylacrylamides.
Among the polar monomers carrying the electron-withdraw-
ing substituents, the N,N-dialkylmethacrylamides such as N,N-
dimethylmethacrylamide (DMMA) show the very strange negative
1
8
conditions to form the stable anionic living polymer. The
poly(M3)s possessing the predicted molecular weights and the
very narrow MWDs (M /M < 1.1) are obtained in quantitative
w
n
yields. The stability of pendant aziridine ring during the anio-
nic polymerization is noteworthy, since the ring-opening and
*Corresponding author. E-mail: tishizon@polymer.titech.ac.jp.
r 2009 American Chemical Society
Published on Web 12/03/2009
pubs.acs.org/Macromolecules

1
08 Macromolecules, Vol. 43, No. 1, 2010
Suzuki et al.
isomerization reactions of N-acylaziridines with various nucleo-
in Figure 1. After the polymerization of M4, two signals
corresponding to R and β vinyl carbons at 138.5 and 119.1
ppm disappeared completely, and signals of methylene car-
bon and quaternary carbon in main chain newly appeared at
52 and 45.5-47.0 ppm, respectively. Furthermore, after the
polymerization reaction, three carbon signals assigned to
azetidine ring remained at the similar region of M4. It is
1
9
philes have been reported in the organic synthesis. Very
recently, Chen and co-workers also succeeded in the coordina-
tion-addition polymerization of M3 with transition metal cata-
20
lysts, although M3 possessed the strained aziridine rings
activated with the electron-withdrawing N-acyl moiety. Thus,
considering the striking findings that only MAz and M3 can be
polymerized, we postulate that the strained cyclic moiety as three-
membered aziridine ring is essential to realize the polymerization
of N,N-dialkylmethacrylamides. In contrast to the usual car-
noteworthy that the two CH groups adjacent to azetidine
2
nitrogen (signals e and f in Figure 1) are nonequivalent in the
both spectra of M4 and poly(M4), indicating the restricted
rotation between CdO and amide nitrogen on azetidine ring
in the monomer and the resulting polymer. These spectra
clearly indicate that the vinyl polymerization of M4 success-
fully proceeds, and the strained azetidine moiety is intact
during the course of the polymerization.
boxylic amides possessing the planarity in (OdC)-NR moiety,
2
various aziridine amides are recognized as nonplanar amide
showing characteristic features on conformation and spectro-
21
scopic properties. This nonplanarity in aziridine amides is
mainly derived from the pyramidal geometry of nitrogen in the
highly strained three-membered ring, and it might play an
important role to result in the positive polymerizability of MAz
The results of anionic polymerization of M4 are summar-
ized in Table 1. The polymerization of M4 with either
DMPLi or Ph CHLi successfully gave a polymer in the
16-18,20
and M3.
2
In this study, a series of monomers possessing four-, five-, and
six-membered rings, N-methacryloylazetidine (M4), N-metha-
cryloylpyrrolidine(M5), and N-methacryloylpiperidine (M6), are
therefore synthesized purposefully to compare the relative po-
lymerizability with M3 (Chart 1). Since the ring strain continu-
ously and drastically decreases with increasing the substituted
ring size of monomers from M3 to M6, the varying polymeriza-
tion behaviors as a function of ring size are of great interest. We
have already reported that the anionic polymerizations of the
corresponding acryloyl monomers possessing aziridine, pyrroli-
presence of LiCl at -78 °C (runs 1 and 2). However, the
resulting polymer precipitated at -78 °C during the course of
the polymerization, and the polymer yields were not quanti-
tative (72-84%) even after 96 h reaction. At elevated
temperature at -40 °C, the polymerization of M4 proceeded
homogeneously and completed within 15 h (run 3). The
molecular weight of poly(M4) was estimated from the H
NMR by using end-group analysis of the initiator residue
containing aromatic protons. The M of poly(M4) agreed
n
1
well with the calculated value estimated by the molar ratio
between M4 and Ph CHLi. The size exclusion chromato-
1
8
6
6
dine, and piperidine rings, A3, A5, and A6, proceed smoothly
2
and afford the vinyl polymers quantitatively as in the case of
graphy (SEC) showed unimodal trace, and the MWD was
narrow (M /M = 1.11). Similarly, poly(M4)s with very
5,6
22
DMA. Herein, we also attempt to polymerize N-acryloylaze-
tidine (A4) possessing four-membered ring as a counterpart of
M4 to verify the general positive polymerizability of acryloyl
monomers.
w
n
narrow MWDs were produced with Ph CHLi/LiCl in quan-
2
23
titative yields at -40 °C within 24 h (runs 4 and 5). It is
noticeable that the well-defined poly(M4)s quantitatively
yielded even at higher temperatures of -20 and 0 °C (runs
Results and Discussion
6
and 7). We next employed Lewis acidic Et Zn as the
2
Anionic Polymerization of M4. Anionic polymerization of
M4 was carried out with 1,1-diphenyl-3-methylpentyllithium
effective additive for the polymerization of various polar
6
-8,24,25
monomers.
Ph CHLi/Et Zn seemed slightly slower compared with the
The polymerization reaction with
(DMPLi), an adduct of sec-BuLi and 1,1-diphenylethylene,
diphenylmethyllithium (Ph CHLi), diphenylmethylsodium
2
2
system of Ph CHLi/LiCl, and most of monomer was con-
2
2
(
Ph CHNa), and diphenylmethylpotassium (Ph CHK) in
2
sumed within 24 h at 0 °C. The poly(M4)s obtained with
Ph CHLi/Et Zn also possessed narrow MWDs (M /M <
1.2). Interestingly, poly(M4) with controlled chain structures
2
THF at various temperatures (-78, -40, -20, and 0 °C).
In most cases, LiCl or Et Zn was added to the polymeriza-
tion system as an additive to control the polymerization of
M4, as in the polymerization of M3. After quenching the
polymerization with degassed methanol, the polymerization
solution was poured into a large excess of diethyl ether.
Then, the precipitated polymer was collected by filtra-
tion and analyzed by H and C NMR and IR spectro-
scopies and elemental analysis. C NMR spectra of M4 and
2
2
w
n
2
quantitatively formed at -40 °C, when the polymerization of
1
8
M4 was conducted with Ph CHLi in the absence of additives
(run 10). The MWD of the polymer was slightly broadened
(M /M = 1.27) in the polymerization performed with
2
w
n
Ph CHLi at 0 °C (run 11). Ph CHNa also induced the
2
2
1
13
polymerization of M4 at -40 °C to form a polymer having
1
3
predicted M and narrow MWD either in the presence or
in the absence of Et Zn. In the presence of Lewis acidic
n
a polymer obtained with Ph CHLi/LiCl at -40 °C are shown
2
2
Chart 1

Article
Macromolecules, Vol. 43, No. 1, 2010 109
Et Zn, the polymerization proceeded much slower and did
2
We also attempted to polymerize M4 under the radical
conditions with AIBN in toluene at 70 °C. The conversion of
M4 reached 40% after 72 h, and the resulting polymeric
products were oligomers possessing very low molecular
not complete even after 72 h at -40 °C, while the polymer-
ization initiated with Ph CHNa completed within 13 h. We
then attempted to polymerize M4 with organopotassium
initiator (Ph CHK) in the presence of Et Zn. No apparent
2
weight (M < 500). It is thus demonstrated that M4 also
n
2
2
polymerization of M4 virtually occurred with Ph CHK/
2
undergoes the radical polymerization as well as the anionic
polymerization; even M4 is a derivative of N,N-dialkyl-
methacrylamide showing nonpolymerizability. From the
viewpoints of polymerization rate and the yield, the relative
polymerizability of M4 under the anionic and radical con-
Et Zn at -78 °C even after 72 h (run 14). This is sharp
2
contrast to the polymerization behavior initiating with or-
ganolithium initiator at -78 °C (runs 1 and 2). On the other
hand, complete consumption of M4 was attained at 0 °C
after 24 h (runs 17-19), although monomer conversion was
still 20% at -40 °C after 15 h (run 15). The binary system of
Ph CHK/Et Zn always gave the poly(M4)s possessing very
1
8
ditions is apparently lower than that of M3. In particular,
compared to the anionic polymerization of M3, higher
polymerization temperature and longer polymerization time
are required for the completion of the polymerization of M4.
Stereoregularity of Poly(M4). In this section, we focused
2
2
narrow MWDs (M /M < 1.1, runs 16-19), while the
w
n
polymer obtained at higher [M]/[I] ratio (run 19) showed
the apparent deviation between the observed molecular
weight (M = 55 000) and the calculated value (Mn =
1
3
on the tacticity of poly(M4)s. In the C NMR spectra of
poly(M4)s measured in DMSO-d at 75 °C, the split signals
n
6
2
3
2
9 000). Finally, we carried out the direct polymerization
assigned to R-methyl carbon were observed around
18.0-21.7 ppm. We postulated that the tacticity of poly(M4)
was observed same as that of poly(methyl methacrylate)
of M4 with Ph CHK at 0 °C for 16 h (run 20). The
2
polymerization reaction completely proceeded to afford
the well-defined poly(M4), while the MWD was slightly
broad (M /M = 1.17).
2
4
(PMMA). The R-methyl carbon signals were therefore
assigned to rr (18.0-18.7 ppm), mr (19.2-19.8 ppm), and
w
n
1
3
Figure 1. C NMR spectra of M4 (A) and poly(M4) obtained with Ph
2 3
CHLi/LiCl (B) measured in CDCl .
Table 1. Anionic Polymerization of M4 in THF
-
3
d
tacticity, %
M
n
ꢀ 10
a
b
c
n
run M4, mmol
initiator, mmol
DMPLi, 0.147
additive, mmol temp, °C time, h conversion, % calcd
obsd
M
w
/M
mm
mr
rr
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6.69
5.91
6.32
6.98
10.9
12.2
7.36
6.57
6.76
6.25
5.79
7.62
8.15
5.93
6.83
6.89
6.83
7.18
9.25
6.52
LiCl, 0.589
LiCl, 0.317
LiCl, 0.437
LiCl, 0.195
LiCl, 0.286
LiCl, 0.418
LiCl, 0.396
-78
-78
-40
-40
-40
-20
0
-40
0
-40
0
-40
-40
-78
-40
0
72
96
15
24
24
84
72
5.0
11
7.0
18
29
16
15
26
9.3
18
8.1
9.2
17
4.6
1.09
1.14
1.11
1.05
1.10
1.07
1.05
1.06
1.17
1.08
1.27
1.06
1.13
92
93
72
70
73
72
68
27
38
60
55
11
52
8
7
<1
<1
5
5
4
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
CHLi, 0.0693
CHLi, 0.115
CHLi, 0.0471
CHLi, 0.0456
CHLi, 0.0989
CHLi, 0.0610
CHLi, 0.0270
CHLi, 0.0930
CHLi, 0.0439
CHLi, 0.0906
14
6.7
19
50
15
18
39
7.8
23
9.8
6.9
19
100
100
100
100
100
85
23
25
23
23
27
54
45
33
35
57
42
2.5
5
5
2
36
24
16
16
72
13
72
15
5
Et
Et
2
Zn, 0.464
Zn, 1.17
19
17
7
10
32
6
2
98
1
1
1
1
1
1
1
1
1
1
2
100
100
69
100
0
20
91
100
100
100
100
CHNa, 0.0731 Et
CHNa, 0.0594
2
Zn, 1.14
CHK, 0.108
CHK, 0.100
CHK, 0.0755
CHK, 0.105
CHK, 0.0521
CHK, 0.0398
CHK, 0.0692
Et
2
Et
2
Et
2
Et
2
Et
2
Et
2
Zn, 1.25
Zn, 1.15
Zn, 0.896
Zn, 1.25
Zn, 0.669
Zn, 0.572
7.0
1.7
11
8.3
17
1.5
15
7.2
19
55
16
1.10
1.06
1.07
1.09
1.17
0
0
0
0
24
24
24
16
14
13
15
12
60
62
62
54
26
25
23
34
29
12
a
b
M
n
(calcd) = (MW of monomer) ꢀ conversion/100[monomer]/[initiator] þ (MW of initiator fragment).
n
M (obsd) was obtained by end-group
d
1
c
analysis using H NMR. M
w
/M
n
was obtained by SEC calibration using polystyrene standards in DMF containing 0.01 M LiBr. The triad tacticity
at 75 °C.
13
was determined by the C NMR measurment in DMSO-d
6

1
10 Macromolecules, Vol. 43, No. 1, 2010
Suzuki et al.
Figure 3. SEC traces of a series of poly(M4)s obtained with DMPLi in
the presence of 4.2-fold LiCl in THF at -20 °C: (A) after 5 min, 36%
1
3
Figure 2. C NMR spectra of R-methyl carbon of poly(M4)s mea-
sured in DMSO-d
at 75 °C: (A) DMPLi/LiCl at -78 °C, mm/mr/rr =
2/8/<1; (B) Ph
CHLi/LiCl at -40 °C, mm/mr/rr = 72/23/5; (C)
Ph CHLi at -40 °C,
CHLi/LiCl at 0 °C, mm/mr/rr = 68/27/5; (D) Ph
mm/mr/rr = 60/33/7; (E) Ph
CHNa at -40 °C, mm/mr/rr = 52/42/6;
F) Ph CHLi/Et CHK/
Zn at -40 °C, mm/mr/rr = 27/54/19; (G) Ph
Et CHK at 0 °C, mm/mr/
Zn at 0 °C, mm/mr/rr = 13/62/25; (H) Ph
rr = 12/54/34; (I) Ph CHNa/Et
Zn at -40 °C, mm/mr/rr = 11/57/32.
conversion, M
sion, M = 7600, M
= 12000, M /M
4 000, M /M
5 000, M /M
n
= 3300, M
w n
/M = 1.05; (B) after 21 min, 63% conver-
6
n
w
/M = 1.08; (C) after 51 min, 84% conversion,
n
9
2
M
n
w
n
= 1.07; (D) after 95 min, 97 conversion, M
n
=
=
2
2
1
1
w
n
= 1.07; (E) after 160 min, 100% conversion, M
= 1.07.
n
2
w
n
(
2
2
2
2
2
2
2
mm (21.1-21.7 ppm) triads in series. A series of expanded
C NMR spectra of poly(M4) are shown in Figure 2, and the
13
tacticity estimated from the relative signal intensity is sum-
marized in Table 1. The stereoregularity of the poly(M4) is
largely changed by the polymerization conditions, as can be
seen in Figure 2.
The mm contents of poly(M4)s produced with Ph CHLi,
2
Ph CHNa, and Ph CHK at 0 or -40 °C were 55-60, 52, and
2
2
1
3
2%, respectively. On the other hand, mr contents were
3-35 (Li ), 42 (Na ), and 54% (K ) and evidently in-
þ
þ
þ
creased with the radius of the counterion. These data
strongly indicate the significant effect of counterion on the
stereoregularity, while the effect of polymerization tempera-
ture is also observed. The smaller cation induces the isotactic
configurations of poly(M4), but the larger one prefers the
heterotactic configurations. Apparently, the stereoregularity
of the poly(M4) changed after the addition of Lewis acidic
Et Zn. In each case of polymer obtained with Ph CHM/
Figure 4. First-order plots for the polymerization of M4 at [M]
0
=
-
3
0.48-0.50 M and [I] = (3.8-4.2) ꢀ 10 M: (A) at -20 °C, (B) at
0
-30 °C, (C) at -35 °C, (D) at -40 °C.
Kinetic Studies of Polymerization for M4. We herein
compare the relative polymerizability of M4 and M3 from
the kinetic viewpoint in detail. The monomer conversion was
analyzed by the GLC measurement of the residual monomer.
Figure 3 shows a series of SEC traces of poly(M4)s obtained
with DMPLi/LiCl (4.2 equiv) in THF at -20 °C. The SEC
traces clearly shift from the lower molecular weight region to
the higher side, as the conversion of M4 increases with the
polymerization time. In each case, the resulting polymer
maintains the unimodal and narrow MWD. It is proven
from the SEC trace shift that no chain transfer and termina-
tion reaction occur during the polymerization reaction of M4
at -20 °C. We then attempted to polymerize M4 with
DMPLi/LiCl at -30, -35, and -40 °C in order to estimate
the polymerization rate at each temperature. The initial
2
2
Et Zn, the mr content was predominant. In fact, the binary
2
initiator systems of Ph CHLi/Et Zn and Ph CHNa/Et Zn at
2
2
2
2
0
4
or -40 °C afforded heterotactic configurations, mr =
5-57%, similar to the cases of Ph CHK/Et Zn at 0 °C
2
2
(mr = 60-62%). More interestingly, addition of LiCl to
Ph CHLi caused a significant change of the stereoregularity
2
of the resulting poly(M4)s. When 6-fold LiCl was added to
the polymerization system at 0 °C, the mm content of the
resulting poly(M4) increased from 55% (run 11) to 68%
(run 7). A similar tendency was observed in the polymeri-
zation systems at -40 °C, and the mm content changed from
6
In the presence of LiCl, the mm content tended to increase
0 (run 10, without LiCl) to 70-73% (runs 3-5, with LiCl).
with lowering the polymerization temperature and reached
9
LiCl or Et Zn to the organolithium initiator induces iso-
3% at -78 °C. Thus, we have found that the addition of
concentration of DMPLi, [I] , was regulated between 3.8 ꢀ
0
-
3
-3
2
10 and 4.2 ꢀ 10 M, and the content of LiCl was
controlled in range of 4.2-4.6 equiv against DMPLi. At all
temperatures, the first-order plots showed good linearity
within the experimental error, as shown in Figure 4. This
clearly verifies that the concentration of the propagating
enolate anion derived from M4 is almost constant during the
polymerization under the employed conditions. Next, the
tactic-specific or atactic polymerization of M4, respec-
tively. From the synthetic viewpoint, the tacticity of
poly(M4) can be tuned by changing the counterion of
initiator, the additive, and the polymerization temperature.
A similar relationship between initiator systems and stereo-
regularity has been observed in the anionic polymerization
6
,7
ap
of N,N-diethylacrylamide and N-methoxymethyl-N-iso-
propylacrylamide.
kp value at each temperature was calculated from the slope
of first-order plot shown in Figure 4. The kp values strongly
8
ap

Article
Macromolecules, Vol. 43, No. 1, 2010 111
a
Table 2. Rate Constants of Anionic Polymerization of M4
presence of 14-35-fold Et Zn at -78 and 0 °C (runs 23-25).
2
ap
p
-1 -1
In addition, the M s of the resultant poly(A4) were in
n
temperature, °C
k
, L mol
s
accordance with the calculated values. Poly(A4)s were simi-
larly obtained with Ph CHK in 100% yields (run 26). Similar
-20
-30
-35
-40
0.129 ( 0.01
2
0.0540 ( 0.005
0.0297 ( 0.003
0.0157 ( 0.002
to the polymerization systems using organolithium initiator,
the addition of Et Zn (13-31 equiv) to Ph CHK was very
2
2
a
effective to narrow the MWD. The well-defined poly(A4)s
were obtained when Et Zn was introduced to the polymeri-
In THF in the presence of 4.2-4.6-fold LiCl.
2
zation system at -78 or 0 °C. The radical polymerization of
A4 with AIBN at 70 °C in toluene for 4 h afforded the polymer
in 100% yield.
The diad tacticity of poly(A4) was determined from the
signal intensity of main chain methylene protons in the H
1
1
NMR measurement (Table 3). Figure 6 shows a series of H
NMR spectra of poly(A4)s synthesized by the anionic poly-
merization at -78 °C. As a general trend, m-rich poly(A4)s
were produced by the anionic polymerization, while the
radical polymerization induced the atactic configuration
(
Ph CHLi and Ph CHK were 79 and 86%, respectively. The
m:r = 57:43). The m contents of poly(A4)s obtained with
2
2
addition of LiCl to Ph CHLi initiator slightly increased the
2
m content to 85%. On the other hand, the addition of Lewis
acidic Et Zn to Ph CHLi resulted in the lower meso-diad in
2
2
addition to the narrowing the MWD of polymer. A similar
additive effect of Et Zn was observed in the polymeriza-
2
tion with Ph CHK.
2
p
Figure 5. Arrhenius plots of k for the polymerization of M4 with
Thus, we have realized that A4 possessing the strained
azetidine ring also undergoes the anionic polymerization in
the controlled fashion similar to the cases of a series of N,N-
dialkylacrylamides such as A3, A5, A6, and DMA. In
both cases of A4 and M4, well-defined polymers quantita-
tively yielded by tuning the reaction conditions, and the
stereoregularity of polymers was affected by the counterion
of initiators and by the additives.
DMPLi and 4.2-4.6-fold LiCl in THF.
depended on the polymerization temperature, and varied
from 0.129 L mol
-
1
-1
-1 -1
1
8
6
6
5,6
s
at -20 °C to 0.0157 L mol
s
at -40 °C, as listed in Table 2. It has been demonstrated
ap
p
-1
that the k values of the polymerization for M3 are 0.165 L
at -60 °C.
-
1
-1 -1
18
mol
s
Thus, the observed k
at -40 °C and 0.0169 L mol
s
ap
p
value of M4 is ∼10 times smaller
ap
than that of M3 under the similar polymerization conditions.
The Arrhenius plots of kp for the anionic polymerization of
Attempts of Anionic Polymerizations for M5, M6, and
DMMA. We finally attempted to polymerize N,N-dialkyl-
methacrylamides carrying five-membered pyrrolidine ring
ap
M4 are drawn in Figure 5, and the relationship between kp
and the polymerization temperature is expressed in the
equation
(
M5) and six-membered piperidine ring (M6) in order to
further elucidate the relationship between the molecular
structure and the polymerizability of N,N-dialkylmethacryl-
amides (Table 4). The controlled polymerization of the
corresponding acryloyl monomers, A5 and A6, has been
ap
ln kp ¼ -6:17 ꢀ 10 =T þ 22:4 L mol
3
-1 -1
s
ð1Þ
ap
The activation energy of the polymerization, ΔE , of Ma4p
was calculated to be 51 ( 5 kJ mol from eq 1. This ΔE
was close to the reported value of M3 (49 ( 4 kJ mol ) but
was slightly larger, supporting the lower polymerizability of
M4 compared to M3 as discussed in the preceding section.
It should be emphasized that the ΔEa s of M3 and M4
were significantly larger than the reported values of
6
a
reported. We also reexamined the polymerization of
DMMA under the similar polymerization conditions.
At first, we have realized the positive polymerizability of
-
1
a
-
1
M5 by the initiation with Ph CHLi at 0 °C (run 30). The
2
resulting poly(M5) possessed the narrow MWD and the
predicted M , while the monomer conversion was 69% even
ap
n
after 72 h. Similarly, the binary initiator system of DMPLi/
LiCl induced the polymerization of M5 at -40 °C, but only
9% of M5 was consumed after 15 h (run 31). Even when M5
underwent the polymerization reaction for 72 h, the mono-
mer conversion was still 44% (run 32). At higher temperature
of 0 °C after 72 h, the conversion increased to 65%. However,
the conversion was almost constant (∼65%), and 100%
conversion could not be achieved even after longer time for
168 and 336 h (runs 33 and 34). M5 also underwent the
polymerization with Ph CHLi/Et Zn at -40 °C within 72 h
anionic polymerization of methyl methacrylate (MMA, 20-
-
1
5 kJ mol ) under similar conditions. The low anionic
26
2
polymerizability of M4 is thus realized by the kinetic data
such as small rate constant and large activation energy of
polymerization for M4. The relative anionic polymerizabil-
ity among M3, M4, and MMA is clearly determined as
follows: M4 < M3 , MMA.
Anionic Polymerization of A4. We next polymerized A4,
acryloyl counterpart of M4, under similar conditions. The
results of the polymerization of A4 are summarized in Table 3.
2
2
in 30% conversion. In the case of Ph CHK, the conversions
2
In each case, the polymerization of A4 with either Ph CHLi or
2
of M5 were 74 and 77% at 0 °C after 72 and 168 h,
respectively. The MWDs of polymers were very broad
(M /M = 2-2.5). On the other hand, no apparent polym-
Ph CHK at 0 or -78 °C proceeded quantitatively. The direct
2
initiation of A4 with Ph CHLi gave a poly(A4) of broad
MWD (M /Mn = 1.45). When LiCl was added to the
2
w
n
w
erization took place with Ph CHK in the presence of Et Zn
2 2
polymerization solution (run 22), the MWD was further
broadened (M /M = 1.65). By contrast, the poly(A4)s with
at -40 °C in 72 h. Higher polymerization temperature at 0 °C
w
n
was necessary to achieve the polymerization with Ph CHK/
Et Zn. The additive effect of Et Zn to Ph CHK was realized
2
narrow MWDs (M /M < 1.11) were obtained, when
w
n
2
2
2
the polymerizations were performed with Ph CHLi in the
2
at 0 °C to retard the propagation and to narrow the MWD of

1
12 Macromolecules, Vol. 43, No. 1, 2010
Suzuki et al.
a
Table 3. Anionic Polymerization of A4 in THF
-
3
e
tacticity, %
M
n
ꢀ 10
b
c
d
n
run
A4, mmol
initiator, mmol
additive, mmol
LiCl, 0.513
temp, °C
time, h
calcd
obsd
M /M
w
m
r
21
22
23
24
25
26
27
28
29
5.83
5.83
5.28
5.93
5.79
4.92
6.04
4.59
7.28
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
CHLi, 0.108
CHLi, 0.108
CHLi, 0.107
CHLi, 0.0494
CHLi, 0.120
CHK, 0.104
CHK, 0.128
CHK, 0.106
-78
-78
-78
-78
0
-78
-78
0
2
2
2
2
2
2
2
20
2
6.3
6.2
5.6
14
5.5
5.5
5.4
5.0
12
6.8
1.45
1.65
1.11
1.06
1.09
1.79
1.08
1.09
1.04
79
85
72
21
15
28
10
7.4
18
6.4
7.2
7.0
6.5
Et
2
Et
2
Et
2
Zn, 1.58
Zn, 1.74
Zn, 1.73
86
67
14
33
Et
2
Et
2
Et
2
Zn, 1.81
Zn, 1.34
Zn, 2.13
CHK, 0.0680
b
0
16
a
c
Conversion = 100% in all cases. M
n
(calcd) = (MW of monomer) ꢀ [monomer]/[initiator] þ (MW of initiator fragment). M
n
(obsd) was obtained
e
1
by end-group analysis using H NMR.
diad tacticity was determined by the H NMR measurment in CDCl at 50 °C.
d
M /M was obtained by SEC calibration using polystyrene standards in DMF containing 0.01 M LiBr. The
w n
1
3
from the reaction mixture. On the addition of DMMA to
Ph CHK, an orange color of initiator solution remained
2
throughout the course of the polymerization, and no poly-
meric product of DMMA formed. We also tried to poly-
merize DMMA under the radical conditions with AIBN in
toluene at 50 and 70 °C for 72 h. However, any trace of
polymeric product was not obtained from the radical poly-
merization system. The nonpolymerizability of DMMA was
again confirmed by our experiments similar to the previous
2
,10-14
reports from the various research groups.
Relative Polymerizability of Monomers. Thus, it is demon-
strated from the present study that the polymerizability of a
series of N,N-dialkylmethacrylamides carrying small-mem-
bered ring decreases drastically with increasing ring size
from three to six (M3 > M4 > M5 . M6). In particular,
the polymerizations of M3 and M4 proceed quantitatively to
give well-defined vinyl polymers in the living manners under
the suitable basic conditions, even though they are the N,N-
1
Figure 6. H NMR spectra of main-chain methylene proton for poly-
(
A4)s measured in CDCl
3
at 50 °C: (A) Ph
CHLi/LiCl, m/r = 85/15; (C) Ph CHLi, m/r = 79/21; (D)
CHLi/Et Zn, m/r = 72/28; (E) Ph CHK/Et Zn, m/r = 67/33.
2
CHK, m/r = 86/14; (B)
Ph
Ph
2
2
dialkylmethacrylamide derivatives usually showing non-
By contrast, we have not obtained
2,10-14
2
2
2
2
polymerizability.
any polymeric product from the polymerization system of
M6 under the various conditions similar to the polymeriza-
tion behavior of DMMA.
poly(M5) (runs 40 and 41), whereas the monomer conversion
was still not quantitative after the prolonged polymerization.
The stereoregularity of the poly(M5) could not be deter-
mined, since the suitable signals in H and C NMR spectra
were overlapped with other signals. Thus, we could manage
to polymerize M5 via the slow propagation, while the
completion of polymerization had not been achieved even
under the drastic reaction conditions. These clearly indicate
the lower polymerizability of M5 compared to those of M3
and M4.
We have reported that the anionic polymerizability of
vinyl monomers can be predicted by the β-carbon chemical
1
13
1
3
27
shifts of vinyl groups in the C NMR spectra, which
reasonably reflect the electron densities of the CdC bonds
accepting the nucleophilic attack of the initiator and the
propagating carbanion. In our present study, the varied
polymerizability can be explained by the β-carbon chemical
1
3
shifts of N,N-dialkylmethacrylamides in the C NMR spec-
1
3
Next, we found that no apparent polymerization of M6
occurred under the various reaction conditions (runs
tra. In fact, the C NMR chemical shifts of vinyl β-carbons
of M3, M4, M5, M6, and DMMA are observed at 124.5,
119.1, 116.0, 114.6, and 115.4 ppm, respectively, as can be
4
Ph CHK, the characteristic color of the initiator disap-
2-48). On the addition of M6 to DMPLi, Ph CHLi, or
2
2
8
seen in Figure 7. These β-carbon chemical shifts are in good
accordance with the relative polymerizability (M3 > M4 >
M5 . M6 = DMMA) observed in the present study. The
upfield chemical shifts for M5, M6, and DMMA (115-116
ppm) are rather comparable to that of styrene (113.8 ppm)
and far from the downfield values of typical polar monomers
such as methyl acrylate (130.6 ppm), MMA (125.3 ppm), and
DMA (125.8 ppm). We now consider that the β-carbon
chemical shifts effectively reflect the π-electron densities of
vinyl groups and the anionic polymerizability of a series of
N,N-dialkylmethacrylamides.
2
peared, suggesting the occurrence of initiation reaction.
However, no polymer was obtained in each case after
quenching the polymerization after 72 h, and the unreacted
M6 was recovered almost quantitatively. In addition, it has
been reported that the radical polymerization of M6 with
1
0
AIBN also gives no polymeric product. These polymeriza-
tion behaviors of M6 are in accordance with the negative
polymerizability of DMMA as shown below.
Finally, the anionic polymerization of DMMA was at-
tempted under the preferable reaction conditions with
DMPLi or Ph CHK either in the presence or in the absence
2
Furthermore, the conformation of monomer and the
dihedral angle between CdC and CdO groups are consid-
ered to be essential to determine the polymerizability of N,N-
of LiCl or Et Zn for 72 h. When DMMA was added to
2
DMPLi, a color change from red to colorless occurred either
with or without additives such as LiCl and Et Zn. However,
15
2
dialkylmethacrylamides, as previously Kodaira, Hogen-
5
20
no polymeric product was formed after the termination with
methanol, and the monomer was quantitatively recovered
Esch, and Chen suggested on the basis of the NMR
chemical shifts and the theoretical calculations. The planar

Article
Macromolecules, Vol. 43, No. 1, 2010 113
Table 4. Anionic Polymerization of M5, M6, and DMMA in THF
-
3
M
n
ꢀ 10
a
b
c
run
monomer, mmol
initiator, mmol
Ph CHLi, 0.107
DMPLi, 0.107
DMPLi, 0.103
DMPLi, 0.102
DMPLi, 0.0943
additive, mmol
temp, °C
time, h
conversion, %
calcd
obsd
w n
M /M
30
31
32
32
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
M5, 6.84
M5, 5.88
M5, 6.25
M5, 6.25
M5, 6.39
M5, 5.03
M5, 5.48
M5, 6.77
M5, 5.97
M5, 5.55
M5, 6.09
M5, 6.33
M6, 5.18
M6, 5.97
M6, 5.89
M6, 5.91
2
0
-40
-40
0
0
0
-40
0
72
15
72
72
168
336
72
72
168
72
72
168
72
72
72
72
72
72
72
72
72
72
72
72
72
72
72
72
69
9
6.2
0.71
3.8
5.7
6.3
4.7
2.3
6.6
6.5
8.7 c
0.70
1.6
1.07
1.07
1.06
1.14
1.28
1.27
1.07
1.98
2.51
LiCl, 0.422
LiCl, 0.462
LiCl, 0.592
LiCl, 0.478
LiCl, 0.322
c
44
65
65
60
30
74
77
0
46
68
0
0
0
0
0
0
0
0
0
0
0
6.9
8.1
2.0
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
Ph
2
CHLi, 0.0891
CHLi, 0.102
CHK, 0.105
CHK, 0.0982
CHK, 0.111
CHK, 0.0895
CHK, 0.0888
CHLi, 0.126
c
Et
2
Zn, 1.09
1.2
7.0
7.8
0
-40
0
Et
Et
Et
2
Zn, 1.17
2
Zn, 0.986
2
Zn, 0.939
4.4
6.7
4.5
7.7
1.11
1.14
0
-40
-40
0
0
-40
0
0
-78
0
-78
0
-78
-78
0
DMPLi, 0.131
Ph CHLi, 0.122
DMPLi, 0.136
LiCl, 0.688
LiCl, 0.568
Et Zn, 1.83
2
M6, 5.85
M6, 5.21
M6, 6.08
Ph
2
Ph
2
Ph
2
CHK, 0.129
CHK, 0.122
CHK, 0.156
2
Et
2
Zn, 2.54
DMMA, 6.76
DMMA, 7.57
DMMA, 8.60
DMMA, 8.69
DMMA, 8.58
DMMA, 7.34
DMMA, 8.69
DMMA, 6.51
DMMA, 8.00
DMPLi, 0.117
DMPLi, 0.0611
DMPLi, 0.114
DMPLi, 0.0756
DMPLi, 0.0762
LiCl, 0.508
LiCl, 0.407
Et Zn, 1.01
2
0
0
0
0
Ph
2
Ph
2
Ph
2
Ph
2
CHK, 0.133
CHK, 0.104
CHK, 0.0986
CHK, 0.0729
Et
Et
2
Zn, 1.15
-78
0
2
Zn, 0.669
0
a
b
M
n
(calcd) = (MW of monomer) ꢀ conversion/100[monomer]/[initiator] þ (MW of initiator fragment).
n
M (obsd) was obtained by end-group
1
analysis using H NMR.
c
M
n
and M
w
/M
n
were obtained by SEC calibration using polystyrene standards in THF solution.
a
Table 5. Solubility of Polymers
poly-
(M3)
poly- poly-
(M4) (M5)
poly-
(A3)
poly- poly-
c
b
b
solvent
(A4)
(A5)
þ
þ
initiator
Li /LiCl
d
d
Li /LiCl
d
e
n-hexane
benzene
I
I
I
S
S
I
I
I
I
I
I
S
S
S
S
S
S
S
S
S
S
I
S
S
S
I
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
CHCl
ethyl acetate
diethyl ether
3
1,4-dioxane
THF
DMSO
DMF
methanol
I
S
S
S
S
S
S
S
S
S
S
f
g
water
a
S
þ
b
c
d
þ
e
þ
I: insoluble; S: soluble. See ref 18. See ref 6. Li /LiCl, K /Et Zn. Li ,
2
þ
þ
f
g
Li /Et Zn, K /Et
2
2
Zn. Cloud point at 26-28 °C. Cloud point at 14 °C.
role for the effective resonance between carbonyl and vinyl
groups in M3 and M4. The evaluations of the stable con-
formation and the varied electron density of the monomers
are now in progress by using the ab initio calculation. We will
comprehensively discuss the relationship between the ob-
served polymerizability and the molecular structure and/or
the spectroscopic data in the forthcoming paper.
1
3
Figure 7. C NMR spectra of vinyl group region for DMMA, M3,
M4, M5, and M6 measured in CDCl at room temperature.
3
geometry of (OdC)-NR moiety and the steric repulsion
between R-methyl or CH = group and two methyl substit-
uents on amide nitrogen in DMMA presumably induce the
twisted conformation of the CdC-CdO system and the
nonpolymerizability. On the other hand, aziridine and aze-
tidine amides are considered to have characteristic features
on conformation as the unusual nonplanar amides with
pyramidal nitrogen. The lack of amide conjugation be-
tween CdO and lone pair on amide nitrogen in M3 and M4,
arisen from the highly strained aziridine and azetidine mo-
ieties, is proposed as the typical nonplanar amides possessing
nitrogen-pyramidal structure and may play a very important
2
Solubility and Thermal Property of Polymers. To our best
knowledge, poly(M4), poly(M5), and poly(A4) are newly
synthesized in this study. Solubility of these polymers is
2
18
listed in Table 5 in addition to those of poly(M3), poly-
1
8
6
(A3), and poly(A5) as the references. Poly(M4), poly(M5),
and poly(A4) are insoluble in n-hexane but soluble in polar
solvents such as methanol, DMF, and DMSO. It should be
noted that all three polymers had water solubility, indicating
the high polarity of N,N-dialkylamide moiety. Poly(M4) and
poly(A4) bearing four-membered azetidine ring presented
higher polarity than their counterparts, poly(M3) and
2
1

1
14 Macromolecules, Vol. 43, No. 1, 2010
Suzuki et al.
poly(A3), having three-membered 2-methylaziridine ring. For
example, poly(M4) was completely soluble in water at any
temperature, but the corresponding poly(M3) was insoluble in
water. Furthermore, poly(A4) was readily soluble in water at
any temperature, while the aqueous solution of poly(A3)
Initiators. Commercially available sec-BuLi (1.0 M in cyclo-
hexane, Kanto Chemical Co., Inc.) was used without purifica-
tion and diluted with dry n-heptane. DMPLi was prepared prior
to the polymerization from sec-BuLi and 2-fold DPE in THF at
-
2 2 2
78 °C for 10 min. Ph CHLi, Ph CHNa, and Ph CHK were
18
synthesized by the reaction of the corresponding metal naphthal-
enide and 1.5-fold diphenylmethane in dry THF under argon at
room temperature for 48 h. These initiators were sealed off
under high-vacuum conditions in ampules equipped with
break-seals and stored at -30 °C. The concentration of initiator
was determined by colorimetric titration using standardized
showed the cloud point (T ) around 14 °C. On the other
c
hand, the polarity of poly(M5) seemed lower in comparison
with poly(M4), since the poly(M5) had the typical thermally
dependent solubility (T = 26-28 °C) in water.
c
The glass transition temperatures (T ) of polymers ob-
tained with Ph CHK/Et Zn were analyzed by differential
g
2
2
1
-octanol in THF in a sealed reactor under vacuum, as previously
scanning calorimetry (DSC). T s of poly(M4), poly(M5),
g
29
reported. AIBN for radical polymerization was purified by
recrystallization from methanol.
and poly(A4) were observed at 168, 178, and 114 °C,
respectively. The methacryloyl type poly(M4) showed higher
T value compared with the acryloyl counterpart of poly-
Synthesis of M4. A solution of methacryloyl chloride (10.28 g,
98.3 mmol) in dichloromethane (20 mL) was added dropwise to
a mixture of azetidine hydrochloride (9.06 g, 96.8 mmol) and
triethylamine (20.17 g, 199 mmol) in dichloromethane (80 mL)
at 0 °C under nitrogen, and then the mixture was stirred at room
temperature for 4 h. After the filtration of precipitated ammo-
nium salt, the filtrate was washed with 2 N HCl, saturated
g
(
A4), as expected. The strained four-membered azetidine
moieties in poly(M4) and poly(A4) were stable at least below
50 °C, and the polymers were soluble even after the heating.
This is sharp contrast to the facts that poly(M3) and poly-
A3) possessing three-membered aziridine rings are thermo-
setting and become insoluble after the thermal treatment at
2
(
NaHCO aqueous solution, and saturated NaCl aqueous solu-
3
tion. The aqueous layer was extracted with dichloromethane.
1
8
1
50 °C due to the intermolecular cross-linking. Thermal
stability of the resulting polymers was investigated by ther-
mogravimetric analysis (TGA) under nitrogen. The 10%
weight loss temperatures of poly(M4), poly(M5), and poly-
The combined organic layer was dried over anhydrous MgSO
and filtered. After the evaporation, the crude product was
distilled twice over CaH under reduced pressure to yield color-
4
2
less liquid of M4 (9.82 g, 78.6 mmol, 81%, bp 80-81 °C/4
(
A4) were observed at 327, 358, and 352 °C, respectively.
1
mmHg). H NMR (300 MHz, CDCl
3
): δ = 1.92 (s, 3H, CH
3
),
2
CH
.28 (m, 2H, CH ), 4.08 and 4.23 (br, 4H, NCH ), 5.29 (s, 1H, cis
2
2
1
=). C NMR (75 MHz, CDCl
3
Conclusions
2
=), 5.36 (s, 1H, trans CH
2
3
):
δ = 15.8 (CH
2
), 19.4 (CH
3
2
), 48.3 and 52.7 (N-CH ), 119.1
We have conducted the anionic polymerization of a series of N,
N-dialkylmethacrylamides having 4-, 5-, and 6-membered rings
in the amide moieties in order to compare the relative polymer-
izability with DMMA. In sharp contrast to the nonpolymeriz-
ability of DMMA, M4 with 4-membered azetidine ring can be
polymerized quantitatively to afford the stable living polymer
having the predicted molecular weight and very narrow MWD
(
CH =), 138.3 (=C-), 170.9 (CdO). IR (ATR): 2956, 2885,
2
-
1
1
for C
649 (CdC), 1612 (CdO), 1459, 1434, 925 cm . Anal. Calcd
11NO 0.1H O (126.971, hygroscopic): C, 66.22, H, 8.73,
7
H
2
3
N, 11.03. Found: C, 66.54, H, 8.95, N, 10.87.
Synthesis of A4. A solid of azetidine hydrochloride (9.75 g,
1
04 mmol) was added to a solution of 11.98 g (214 mmol) of
KOH in water (8 mL). The reaction system was heated to 90 °C,
and colorless liquid of azetidine (5.06 g, 88.6 mmol) was isolated
in 85% yield by the distillation in the receiver cooled by an ice
bath. A solution of azetidine (5.06 g, 88.6 mmol) and triethyl-
amine (11.43 g, 113 mmol) in diethyl ether (100 mL) was added
dropwise to a mixture of acryloyl chloride (10.67 g, 117 mmol)
and diethyl ether (100 mL) at 0 °C under nitrogen. After stirring
for 2 h at room temperature, the precipitated triethylammonium
chloride was removed by the filtration, and filtrate was concen-
trated by the evaporation. The residual product was purified by
(
3
M /M ∼ 1.1) similar to the previous report for M3 with
w
n
1
8
-membered aziridine ring. The tacticity of poly(M4) is con-
trolled from 11 to 93% in the range of mm-triad content by
choosing the initiator system and the polymerization tempera-
ture. It is substantiated from the viewpoints of polymer yield
and polymerization rate that the anionic polymerizability of N,N-
dialkylmethacrylamides clearly decreases with increasing the ring
size of monomers from 3 to 6 (M3 > M4 > M5 . M6 =
DMMA). The relative polymerizability is well correlated with the
1
3
vinyl β-carbon chemical shifts of monomers in the C NMR
spectra, which reflect the electron density of CdC bonds.
the repeating vacuum distillations over CaH to obtain colorless
2
liquid of A4 (4.72 g, 42.5 mmol, 48%, bp 47-48 °C/3 mmHg).
1
3 2
H NMR (300 MHz, CDCl ): δ = 2.31 (p, 2H, CH ), 4.08 (t, 2H,
N-CH ), 4.23 (t, 2H, N-CH ), 5.62 (d, 1H, J = 9.8 Hz, trans
2
2
Experimental Section
CH
J = 17 Hz, cis CH
(CH ), 47.9 and 50.1 (N-CH
165.5 (CdO). IR (ATR): 2949, 2879, 1793, 1728, 1649 (CdC),
2
=), 6.18 (dd, 1H, J = 17 and 9.8 Hz, =CH-), 6.28 (d, 1H,
13
Materials. All reagents were purchased from Tokyo Kasei,
unless otherwise stated. Azetidine hydrochloride (Aldrich) was
dried under vacuum condition. Pyrrolidine, piperidine, and
2
=). C NMR (75 MHz, CDCl
3
): δ = 15.4
=),
), 125.8 (=CH-), 127.0 (CH
2
2
2
-
1
triethylamine were distilled from CaH . Acryloyl chloride and
2
1613 (CdO), 1434, 1287, 1049, 978, 796 cm . Anal. Calcd for
NO 0.1H O (112.945, hygroscopic): C, 63.81, H, 8.03, N,
12.40. Found: C, 64.18, H, 8.17, N, 12.28.
methacryloyl chloride were used without purification. Diethyl
ether was dried over sodium wire. THF used as a polymerization
solvent was refluxed over sodium wire for 3 h, distilled over
LiAlH , and further distilled from sodium naphthalenide solu-
4
tion on a vacuum line. n-Heptane was washed with concentrated
C
6
H
9
2
3
Synthesis of M5. M5 was synthesized according to the similar
procedure for A4 by using methacryloyl chloride (15.67 g, 150
mmol), pyrrolidine (10.66 g, 150 mmol), and triethylamine
(16.00 g, 158 mmol). The crude product was distilled repeatedly
under reduced pressure to yield colorless liquid of M5 (14.50 g,
2 4 4 2 5
H SO , dried over MgSO , and then dried over P O for 1 day
under reflux. It was then distilled in the presence of n-BuLi under
nitrogen. 1,1-Diphenylethylene (DPE) was distilled from CaH2
in vacuo and then distilled in the presence of 1,1-diphenylhexyl-
lithium on a vacuum line. The purified DPE was diluted with dry
THF. LiCl was dried in vacuo for 2 days and used as a THF
1
104 mmol, 69%, bp 92-93 °C/4 mmHg). H NMR (300 MHz,
CDCl
3.48 (m, 4H, N-CH
3
): δ = 1.90 (m, 4H, -CH
2
-CH
), 5.14 (s, 1H, cis CH
CH =). C NMR (75 MHz, CDCl ): δ = 20.0 (CH ), 24.4 and
2
-), 1.96 (s, 1H, CH
2
3
),
2
=), 5.23 (s, 1H, trans
1
3
2
3
3
solution. Et Zn (TOSOH-Akzo) was distilled under reduced
2
pressure and was diluted with dry THF. DMMA was distilled
over CaH under reduced pressure.
2
26.2 (-CH -CH -), 45.5 and 48.7 (N-CH ), 116.0 (CH =),
2
2
2
2
141.9 (=C-), 170.7 (CdO). IR (ATR): 2975, 2952, 1647
(CdC), 1609 (CdO), 1451, 1428, 1368, 1340, 1224, 1186, 1168,

Article
Macromolecules, Vol. 43, No. 1, 2010 115
-
1
9
13 cm . Anal. Calcd for C
scopic): C, 68.15, H, 9.44, N, 9.93. Found: C, 68.18, H, 9.51, N,
.96.
Synthesis of M6. M6 was prepared by the reaction of metha-
8
H
13NO 0.1H
2
O (140.996, hygro-
presence of LiCl in THF in an all-glass apparatus equipped
with break-seals and several ampules under high-vacuum con-
ditions. After a THF solution of M4 was added to the initiator
solution at -78 °C, the mixture was immediately divided into
several ampules and sealed off at -78 °C. Then, the sealed
ampules were placed in an acetone bath thermostated at a
desirable temperature between -20 and -40 °C. After the
given time, the polymerization was terminated with methanol
at -78 °C. The total content of each ampule was diluted to an
appropriate volume, and the concentration of the residual
3
9
cryloyl chloride (15.31 g, 146 mmol) and piperidine (13.08 g, 154
mmol) in the presence of triethylamine (15.34 g, 146 mmol) in
diethyl ether. Repeating vacuum distillations of the crude
product gave colorless liquid of M6 (14.8 g, 96.7 mmol, 66%,
): δ =
1
bp 61-63 °C/0.7 mmHg). H NMR (300 MHz, CDCl
3
1
.56 (br, 4H, N-CH -CH ), 1.65 (m, 2H, N-CH -
2
2
2
CH -CH ), 1.95 (s, 3H, CH ), 3.47 and 3.56 (br, 4H, N-CH ),
monomer [M] was measured by GLC with undecane as an
t
external standard. The observed experimental error of [M] was
t
5% in the range 0.04-0.50 M.
2
2
3
2
1
3
5.01 (s, 1H, cis CH
MHz, CDCl
2
=), 5.13 (s, 1H, trans CH
): δ = 20.6 (CH
2
=). C NMR (75
-CH
3
3
), 24.7 (N-CH
2
2
-
CH ), 25.6 and 26.8 (N-CH -CH ), 42.3 and 47.9 (N-CH ),
Radical Polymerization. Radical polymerization of M4 (0.74
g, 5.92 mmol) was carried out with AIBN (0.14 g, 0.80 mmol) in
toluene (20 mL) at 70 °C for 72 h under nitrogen. The reaction
mixture was poured into a mixture of hexane and diethyl ether to
precipitate a poly(M4) (0.30 g, 40% yield, Mn < 500). The
polymerization of A4 (0.67 g, 6.08 mmol) was similarly per-
formed with AIBN (0.11 g, 0.65 mmol) in toluene (20 mL) at
70 °C for 4 h under nitrogen. The poly(A4) (0.67 g, conversion
∼ 100%, M = 4900, M /M = 1.42) was quantitatively
2
2
2
2
1
2
1
(
6
14.6 (CH =), 141.1 (=C-), 171.1 (CdO). IR (ATR): 2935,
2
854, 1644 (CdC), 1618 (CdO), 1469, 1432, 1371, 1294, 1245,
-
1
9 2
204, 1134, 1016, 908, 853 cm . Anal. for C H15NO 0.2H O
3
156.825, hygroscopic): C, 68.93, H, 9.90, N, 8.93. Found: C,
8.83, H, 10.02, N, 9.01.
Purification of Monomers. After careful fractional distilla-
tions, the liquid monomers (M4, A4, M5, M6, and DMMA)
were degassed and sealed off in an apparatus equipped with a
break-seal in the presence of CaH under high-vacuum condi-
tions and diluted with dry THF. The monomer solution in THF
was distilled from CaH on a vacuum line into an ampule fitted
2
with a break-seal and further diluted with dry THF. The
resulting monomer solutions (0.75-0.82 M) in THF were stored
at -30 °C until ready to use for the anionic polymerization.
Anionic Polymerization. All anionic polymerizations were
carried out in THF at -78 to 0 °C in an all-glass apparatus
equipped with break-seals with vigorous shaking under high-
vacuum conditions (10 mmHg). Polymerization was termi-
nated with methanol. The residue was precipitated in diethyl
ether at room temperature. When Et Zn was used as an additive,
the reaction mixture was immediately concentrated in vacuo to
remove THF and excess amount of methanol and again diluted
with THF to precipitate the zinc compounds overnight. After
filtration of the system to remove the precipitated zinc com-
pounds, the filtrate was concentrated by evaporation and pre-
cipitated in diethyl ether. The resulting polymers were further
purified by freeze-drying from benzene and characterized by
NMR and IR spectroscopies and elemental analysis. The fol-
n
w
n
2
obtained after the precipitation in diethyl ether. The resulting
polymer collected by filtration was purified by freeze-drying
from benzene.
1
13
Measurements. H and C NMR spectra were recorded on a
Bruker DPX300 spectrometer (300 MHz for H and 75 MHz for
1
1
3
C) in CDCl
3 6
or d -DMSO. The chemical shifts were reported
in ppm downfield relative to tetramethylsilane (δ 0.00) in CDCl
3
1
for H NMR and CDCl
13
3
(δ 77.1) or DMSO (δ 39.5) for
NMR as standard. Tacticity of poly(M4) was determined by the
C
-
6
29
13
C NMR integral ratio of three split R-methyl carbon signals
appearing at 18.0-21.7 ppm in d -DMSO at 75 °C. Three signals
were assigned as rr (18.0-18.7 ppm), mr (19.2-19.8 ppm), and
mm (21.1-21.7 ppm) triads. Tacticity of poly(A4) was deter-
mined by the H NMR integral ratio of three split methylene
6
2
1
proton signals appearing at 1.1-1.8 ppm in CDCl at 50 °C.
3
Three signals were assigned as m (1.1-1.3 ppm), r (1.3-1.6
ppm), and m (1.6-1.8 ppm) diads. IR spectra were recorded on a
JASCO FT/IR-4100 instrument using either an attenuated total
reflectance (ATR) attachment or KBr disk method. SEC chro-
matograms for determination of MWD were obtained in DMF
-
1
containing 0.01 M LiBr at 40 °C at a flow rate of 1.0 mL min
lowing is the complete list.
1
Poly(M4). H NMR (300 MHz, CDCl
1.7-2.5 (CH
NMR (75 MHz, CDCl
45.5-47 (main chain quaternary), 49.3 (N-CH , cis to
carbonyl), 52.0 (main chain CH
with a TOSOH HLC8120 instrument equipped with three
polystyrene gel columns (TSK-GEL GMHXL ꢀ 2 þ G2000HXL)
with either ultraviolet (254 nm) absorption or refractive index
detection. The cloud point of poly(M5) in water was determined
by monitoring the transmittance using a JASCO UVITEC-660
spectrometer. Transmittance of 0.2 wt % aqueous solution of
polymer at 500 nm was monitored in a PMMA cell (path length
3
3
): δ = 1.0-1.6 (CH ),
1
3
2
and main chain CH
2
), 3.7-4.7 (4H, N-CH
2
).
C
3
): δ = 15.8 (CH
2
), 18.0-21.7 (CH ),
3
2
2
), 54.1 (N-CH
2
, trans to
carbonyl), 173.0-177.5 (CdO). IR (KBr): 2946, 2882, 1594
CdO), 1417, 1300, 1212, 1039 cm- . Anal. Calcd for C
1
(
NO 0.2H O (128.783, hygroscopic): C, 65.28, H, 8.93, N, 10.88.
7 11
H -
-
1
=
1.0 cm) with stirring at a heating rate of 0.5 °C min . The Tgs
3
2
of the polymers were measured by DSC using a Seiko instrument
DSC6220 apparatus under nitrogen flow. The polymer sample
was first heated to 200 °C, cooled to 30 °C, and then scanned at a
Found: C, 65.80, H, 8.89, N, 10.10.
1
Poly(A4). H NMR (300 MHz, CDCl ): δ = 1.1-1.8 (2H,
3
main chain CH ), 1.9-2.1 (1H, main chain CH), 2.11 (2H, CH ),
2
2
-1
1
). C NMR (75 MHz, CDCl
3
rate of 10 °C min . A Seiko Instruments TG/DTA6200 was
3
.8-4.6 (4H, N-CH
2
3
): δ = 15.2
used for TGA analysis at 30-600 °C under nitrogen flow with
(
CH
2
), 32-35 (main chain CH ), 35-38 (main chain CH), 47.9
2
-
1
.
heating rate of 10 °C min
and 50.5 (N-CH ), 173.5-174.5 (CdO). IR (KBr): 2956, 2886,
2
-
1
1
C
1
623(CdO), 1476, 1448, 1364, 1153, 1016 cm . Anal. Calcd for
NO H O (129.169, hygroscopic): C, 55.79, H, 8.59, N,
0.85. Found: C, 57.06, H, 6.59, N, 10.48.
Acknowledgment. This work was partially supported by a
Grant-in Aid (No. 18550105 and 20550108) from the Ministry of
Education, Science, Sports, and Culture, Japan. The authors
appreciate Dr. Mamoru Kobayashi at Lintec Corp. for the NMR
measurement poly(M4) samples.
6
H
9
3
2
1
Poly(M5). H NMR (300 MHz, CDCl
CH ), 1.4-2.4 (6H, -N-CH -CH - and main chain CH
). C NMR (75 MHz, CDCl ): δ = 17-22
CH ), 22.8 and 27.5 (CH ), 46.9 (main chain quaternary), 48.1 and
3
): δ = 0.5-1.4 (3H,
3
2
2
2
),
13
3
(
.0-4.0 (4H, N-CH
2
3
3
2
References and Notes
4
9.2 (N-CH
2
), 51-56 (main chain CH ), 173-177 (CdO). IR
2
-1
(KBr): 2968, 2873, 1601 (CdO), 1456, 1409, 1342, 1182, 1161 cm
Anal. Calcd for C H NO 0.4H O (146.403, hygroscopic): C,
.
(
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13
3
2
65.63, H, 9.50, N, 9.57. Found: C, 65.63, H, 9.50, N, 9.09.
Kinetic Study of Polymerization of M4. Anionic polymeriza-
tion of M4 was performed at -78 °C with DMPLi in the

1
16 Macromolecules, Vol. 43, No. 1, 2010
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(
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1
(
7) (a) Kobayashi, M.; Ishizone, T.; Nakahama, S. Macromolecules
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2
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n
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n
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n
w
(
(
(
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(28) In terms of R-carbon chemical shifts, we have not seen any
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(
(
2
1