Synthesis of water-soluble polymethacrylates by living anionic polymerization of trialkylsilyl-protected oligo(ethylene glycol) methacrylates

Article abstract of DOI:10.1021/ma021257f

2-[2-[(tert-Butyldimethylsilyl)oxy]ethoxy]ethyl methacrylate (2) and 2-[2-[2-[(tert-butyldimethylsilyl)oxy] ethoxy] ethoxy] ethyl methacrylate (3) were polymerized anionically in THF at -78 °C for 2-24 h. The anionic initiator systems included 1,1-diphenyl-3-methylpentyllithium/lithium chloride and diphenylmethylpotassium/diethylzinc. The polymerization of novel tert-butyldimethylsilyl-protected oligo(ethylene glycol) methacrylates, 2 and 3, proceeded quantitatively in each case. The resulting polymers possessed the predicted molecular weights based on the molar ratios of monomers to initiators, and narrow molecular weight distributions (M_w/M_n < 1.1). The stability of the propagating carbanion of poly(2) and poly(3) was ascertained by the quantitative efficiencies of the sequential block copolymerizations using tert-butyl methacrylate (tBMA). Well-defined block copolymers, poly(2)-block-poly(tBMA) and poly(3)block-poly(tBMA), were obtained. The trialkylsilyl protecting groups of poly(2) and poly(3) were quantitatively hydrolyzed using 2 N HC1 in aqueous THF at 0 °C for 2 h to give tailored poly[di(ethylene glycol) methacrylate] and poly[tri(ethylene glycol) methacrylate], respectively. Both polymethacrylates obtained after deprotection were readily soluble in water due to the high polarity of the hydrophilic oligo(ethylene glycol) pendant units with terminal OH functionality.

Full text of DOI:10.1021/ma021257f

42
Macromolecules 2003, 36, 42-49
Synthesis of Water-Soluble Polymethacrylates by Living Anionic
Polymerization of Trialkylsilyl-Protected Oligo(ethylene glycol)
Methacrylates
Ta k a sh i Ish izon e,* Seok Ha n , Syu n su k e Ok u ya m a , a n d Seiich i Na k a h a m a
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering,
Tokyo Institute of Technology, 2-12-1, Ohokayama, Meguro-ku, Tokyo 152-8552 J apan
Received August 5, 2002
ABSTRACT: 2-[2-[(tert-Butyldimethylsilyl)oxy]ethoxy]ethyl methacrylate (2) and 2-[2-[2-[(tert-butyldi-
methylsilyl)oxy]ethoxy]ethoxy]ethyl methacrylate (3) were polymerized anionically in THF at -78 °C for
2-24 h. The anionic initiator systems included 1,1-diphenyl-3-methylpentyllithium/lithium chloride and
diphenylmethylpotassium/diethylzinc. The polymerization of novel tert-butyldimethylsilyl-protected oligo-
(ethylene glycol) methacrylates, 2 and 3, proceeded quantitatively in each case. The resulting polymers
possessed the predicted molecular weights based on the molar ratios of monomers to initiators, and narrow
molecular weight distributions (Mw/Mn < 1.1). The stability of the propagating carbanion of poly(2) and
poly(3) was ascertained by the quantitative efficiencies of the sequential block copolymerizations using
tert-butyl methacrylate (tBMA). Well-defined block copolymers, poly(2)-block-poly(tBMA) and poly(3)-
block-poly(tBMA), were obtained. The trialkylsilyl protecting groups of poly(2) and poly(3) were
quantitatively hydrolyzed using 2 N HCl in aqueous THF at 0 °C for 2 h to give tailored poly[di(ethylene
glycol) methacrylate] and poly[tri(ethylene glycol) methacrylate], respectively. Both polymethacrylates
obtained after deprotection were readily soluble in water due to the high polarity of the hydrophilic oligo-
(ethylene glycol) pendant units with terminal OH functionality.
In tr od u ction
hydrophilic poly(HEMA) is not soluble in water, whereas
it is extremely hygroscopic.
Although the living anionic polymerization of hydro-
carbons such as styrenes and 1,3-dienes is the most
established synthetic tool for producing homopolymers
and block copolymers with well-defined chain struc-
tures,1 it is difficult to polymerize directly functional
monomers containing acidic and/or electrophilic func-
tional groups under anionic conditions. Since the reac-
tive functional groups readily react with anionic initia-
tors and propagating carbanions, if produced, the
functional groups in the monomers must be protected
prior to anionic polymerization. We have succeeded in
the living anionic polymerizations of a series of mono-
mers containing suitable protected functional groups,2
to produce well-defined polystyrenes and polybutadienes
with a variety of functional groups such as hydroxy,
amino, mercapto, formyl, acetyl, carboxyl, and ethynyl
groups after complete removal of the protecting groups.
Poly(2,3-dihydroxypropyl methacrylate), poly(DIMA),
which has two hydroxy groups in each monomer unit,
is more hydrophilic and readily soluble in water.7 Well-
defined poly(DIMA), the ester of glycerine, has been
synthesized via either the living anionic polymerization
of acetal-protected (2,2-dimethyl-1,3-dioxolan-4-yl)-
methyl methacrylate7 or by chemical modification of
anionically synthesized poly(allyl methacrylate).8 Am-
phiphilic block copolymers containing water-soluble
poly(DIMA) segments also exhibit interesting surface
structures and properties.9 Thus, introduction of one
more hydroxy group to the pendant ester moiety of each
repeat unit solubilizes the polymethacrylate in water.
The present paper reports another molecular design
directed to water-soluble polymethacrylates, by intro-
ducing hydrophilic oligo(ethylene glycol) units in the
side chain. The candidates are the poly(methacrylic
acid) esters of di(ethylene glycol) and tri(ethylene
glycol), poly(DEGMA), and poly(TEGMA), respectively.
Although the cross-linked hydrogels of these polymers
have been prepared via free-radical polymerization in
the presence of cross-linkable dimethacrylates,10,11 ex-
amples of linear soluble polymers are extremely limited.
In this study, the ω-hydroxy groups in the side chain of
monomers were masked with bulky and stable tert-
butyldimethylsilyl groups12 prior to polymerization, as
shown in Scheme 1. We herein attempt the anionic
polymerization of novel protected monomers, 2-[2-[(tert-
butyldimethylsilyl)oxy]ethoxy]ethyl methacrylate (2)
and 2-[2-[2-[(tert-butyldimethylsilyl)oxy]ethoxy]ethoxy]-
ethyl methacrylate (3), followed by deprotection of the
resulting polymers to synthesize well-defined poly[oligo-
(ethylene glycol) methacrylate]s showing water-solubil-
ity.
This strategy is also very effective for the tailored
synthesis of functional polymethacrylates containing
hydroxy groups in each monomer unit. Poly(2-hydroxy-
ethyl methacrylate), poly(HEMA), with predicted mo-
lecular weight and narrow molecular weight distribution
(MWD) can be synthesized via the anionic living poly-
merizations of 2-[(trimethylsilyl)oxy]ethyl methacryl-
ate,3,4 2-[(tert-butyldimethylsilyl)oxy]ethyl methacrylate
(1),4 and 2-[(methoxymethyl)oxy]ethyl methacrylate,4
followed by the successive deprotections. Poly(HEMA),
the ester of ethylene glycol, is a hydrophilic polymer that
has attracted a great deal of attention over the years,
particularly for biomedical applications such as contact
lenses, hydrogels, and hemodialysis membranes. The
amphiphilic triblock copolymer, poly(HEMA)-block-
polystyrene-block-poly(HEMA), has excellent nonthrom-
bogenic activity compared to other polymers, probably
due to its microphase separated surface.5,6 However, the
10.1021/ma021257f CCC: $25.00 © 2003 American Chemical Society
Published on Web 12/14/2002

Macromolecules, Vol. 36, No. 1, 2003
Synthesis of Water-Soluble Polymethacrylates 43
Sch em e 1
PLi), an adduct of s-BuLi and 1,1-diphenylethylene, or
diphenylmethylpotassium (Ph2CHK) as the initiator in
both the absence and presence of LiCl and Et2Zn,
respectively. Upon adding the THF solution of monomer
to the initiator solution, the red color of the initiator
system disappeared immediately to give a colorless
solution. The polymerizations of 2 and 3 were homoge-
neous, and they were quenched with degassed methanol.
In several cases, the conversions of monomers were
analyzed by 1H NMR and GLC measurements. The
polymers were isolated by precipitating in a large excess
of methanol. IR and 1H and 13C NMR spectroscopies
confirmed that the tert-butyldimethylsilyl protecting
group in the isolated polymers remains intact during
the polymerization and workup. The molecular weights
of the polymers were determined by end group analysis
using the proton signal intensity in the aromatic region
of initiator residues in the 1H NMR spectroscopy as
previously reported.18 The results of the anionic poly-
merization of 2 and 3 are summarized in Table 1.
Resu lts a n d Discu ssion
Syn th esis of 2 a n d 3. In this study, we have
employed the stable tert-butyldimethylsilyl group as a
protecting group for OH functions12 in di(ethylene
glycol) methacrylate (DEGMA) and tri(ethylene glycol)
methacrylate (TEGMA), since it tolerates the monomer
purification, including extraction and column chroma-
tography, and the direct polymer characterizations. The
trimethylsilyl protecting group is rather unstable and
is gradually cleaved from the isolated polymer even
under the neutral conditions. The tert-butyldimethylsilyl
ether can be removed under both acidic conditions and
under neutral conditions using tetrabutylammonium
fluoride (Bu4NF),12 whereas relatively severe acidic
conditions are necessary to cleave the corresponding
methoxymethyl ether.
Monomers 2 and 3 were synthesized by reaction of
methacryloyl chloride with either tert-butyldimethylsilyl
ether of di(ethylene glycol) or the corresponding silyl
ether of tri(ethylene glycol) in the presence of triethyl-
amine in diethyl ether, as shown in Scheme 1. A
considerable amount of either di(ethylene glycol) di-
methacrylate or tri(ethylene glycol) dimethacrylate was
formed as byproducts. These difunctional vinyl com-
pounds act as cross-linking reagents in the polymeriza-
tions of 2 and 3,10,11 if they are not completely removed.
Therefore, we have thoroughly purified the protected
monomers by repeating column chromatography and
fractional distillation until the monomers are free from
the traces of dimethacrylates.
An ion ic P olym er iza tion of 2 a n d 3. Lithium
chloride (LiCl)13 and diethylzinc (Et2Zn)14,15 improve
control of the molecular weights and the MWDs in the
anionic polymerizations of (meth)acrylate monomers.
Both binary initiator systems (organolithium/LiCl and
organopotassium/Et2Zn) promoted the controlled anionic
polymerizations of (meth)acrylates to form long-lived
growing species. The added LiCl and Et2Zn remarkably
reduced the propagating rate of (meth)acrylates and
lowered the nucleophilicity of active species, probably
by interacting with the propagating enolate anions as
either a common-ion salt or a weak Lewis acid, respec-
tively. The equilibrium reportedly shifts from the ionic
association state toward the nonassociated species in
the presence of additives.14,16 Using these additives, a
variety of functional methacrylates17 including the
trialkylsilyl-protected HEMA, 1,4 indeed underwent
anionic polymerization in a controlled fashion. We
therefore employed LiCl and Et2Zn as additives to
realize the living anionic polymerizations of 2 and 3.
Monomers 2 and 3 were polymerized in THF at -78
°C using either 1,1-diphenyl-3-methylpentyllithium (DM-
The polymerization of 2 proceeded quantitatively with
DMPLi in THF at -78 °C for 2 h. The SEC curve of
poly(2) produced with DMPLi was unimodal with a
small tailing toward low molecular weight region, and
the polydispersity index, Mw/Mn, was 1.29. The Mn value
1
determined by H NMR measurement was very close
to the calculated value based on the molar ratio of
monomer to initiator. Similarly, the poly(2)s with the
predicted molecular weights were obtained in quantita-
tive yields after 2 h by initiating with the binary system
of DMPLi and LiCl, supporting the quantitative initiator
efficiency.19 In these cases, 3-5-fold excess of LiCl to
DMPLi was added in order to tune the polymerization.
The SEC curves of poly(2) obtained in the presence of
LiCl were significantly narrower, and the Mw/Mn values
were approximately 1.05. The MWD was unimodal and
very narrow even after the prolonged reaction time of
12 h. This means that there are no intermolecular side
reaction such as carbonyl condensation between the
propagating chain end and the ester moieties of the
resulting polymer. The polymerization of 2 was not
complete within 30 min in the presence of LiCl, and the
monomer conversions were 57 and 78% after 10 and 30
min reactions, respectively. The polymerizations of other
(meth)acrylates were also retarded in the presence of
LiCl,13,16 but they were much faster than the polymer-
ization of 2. Usually, the complete conversions of (meth)-
acrylates were attained within several minutes even in
the presence of LiCl under the similar polymerization
conditions. This indicates that the lower polymerization
rate of 2 is probably due to the steric effect of bulky tert-
butyldimethylsilyl-protected di(ethylene glycol) moiety.
The complete consumption of 2 was also achieved with
either Ph2CHK or Ph2CHK/Et2Zn at -78 °C for 2 h. The
anionic initiators associated with potassium counterion
also afforded the poly(2)s with controlled molecular
weights in quantitative yields. The MWD was narrower
(Mw/Mn ) 1.03), when the polymerization was performed
with Ph2CHK in the presence of Et2Zn, than in its
absence (Mw/Mn ) 1.14).
The anionic polymerization of 3 using DMPLi in THF
at -78 °C for 16 h quantitatively produced poly(3) with
the predicted Mn and relatively narrow MWD (Mw/Mn
) 1.19). In the presence of LiCl, poly(3) was obtained
in 66% and 90% yield after 10 min and 2 h, respectively.
The polymerization of 3 is slower than that of 2, since
100% conversion of 2 is attained after 2 h under

44 Ishizone et al.
Macromolecules, Vol. 36, No. 1, 2003
Ta ble 1. An ion ic P olym er iza tion of 2 a n d 3 in THF a t -78 °C
Mn×10-3
tacticity (%)d
monomer
type, mmol
additive
type, mmol
time,
h
yield,
%
c
run
initiator type, mmol
calcda
obsdb
Mw/Mn
mm
mr
rr
1
2
3
4
5
6
7
8
2, 3.63
2, 3.63
2, 3.38
2, 2.14
2, 4.98
2, 4.22
2, 7.76
2, 3.23
2, 3.14
3, 3.18
3, 1.92
3, 2.95
3, 3.12
3, 2.61
3, 3.05
3, 3.84
3, 2.17
3, 3.29
s-BuLi, 0.0811/DPE,e 0.306
s-BuLi, 0.0744/DPE, 0.301
s-BuLi, 0.0941/DPE, 0.264
s-BuLi, 0.104/DPE, 0.133
s-BuLi, 0.142/DPE, 0.188
s-BuLi, 0.0616/DPE, 0.122
s-BuLi, 0.0471/DPE, 0.118
Ph2CHK,g 0.113
2
100
57f
13
8.2
8.3
6.2
10
20
48
8.4
7.6
14
5.5
9.5
13
17
12
15
1.29
1.03
1.03
1.03
1.02
1.05
1.03
1.14
1.03
1.19
1.03
1.03
1.11
1.08
1.32
1.03
1.03
1.06
<1
25
75
LiCl, 0.414
LiCl, 0.364
LiCl, 0.602
LiCl, 0.535
LiCl, 0.302
LiCl, 0.306
10 min
30 min
2
2
8
12
2
2
16
10 min
2
24
24
24
2
3
24
8.1
9.5
5.5
9.3
22
78f
100
100
100
100
100
100
100
66f
<1
25
75
63
<1
14
14
25
55
55
26
75
31
31
74
8.0
7.5
14
5.7
10
11
17
11
9
Ph2CHK, 0.121
Et2Zn, 2.52
10
11
12
13
14
15
16
17
18
s-BuLi, 0.0746/DPE, 0.239
s-BuLi, 0.0770/DPE, 0.301
s-BuLi, 0.0930/DPE, 0.189
s-BuLi, 0.0788/DPE, 0.107
s-BuLi, 0.0508/DPE, 0.0839
Ph2CHK, 0.0859
Ph2CHK, 0.138
Ph2CHK, 0.0808
Ph2CHK, 0.0841
<1
LiCl, 0.388
LiCl, 0.499
LiCl, 0.306
LiCl, 0.245
90f
100
100
100
91
100
100
<1
28
57
72
36
7
Et2Zn, 1.13
Et2Zn, 1.06
Et2Zn, 2.52
7.8
9.1
13
7.3
8.4
13
6
58
36
a
b
Mn(calcd) ) (MW of monomer) × [M]/[I] × yield/100 + MW of initiator. Mn(obsd) was determined by end group analysis using 1H
NMR. c Mw/Mn was determined by SEC calibration using poly(MMA) standards in THF. The triad tacticity was determined by the 13C
d
NMR signal intensity of R-methyl carbon (mm ) 22.7-23.7 ppm, mr ) 20.2-21.4 ppm, and rr ) 18.5-19.5 ppm) of the deprotected
g
polymers. e 1,1-Diphenylethylene. f Conversion determined by 1H NMR. Diphenylmethylpotassium.
Ta ble 2. An ion ic Block Cop olym er iza tion of 2 a n d 3 in THF a t -78 °Ca
block copolymer (homopolymerb)
10-3Mn
first monomer,
[M1]/[initiator]
second monomer,
[M2]/[initiator]
run
initiator
yield, %
calcd
obsdc
Mw/Mn
19
20
21
22
Ph2CHKd
Ph2CHKd
s-BuLi
2, 30.0
tBMA, 63.1
tBMA, 43.1
2, 53.0
100 (98)
100 (100)
100
18 (8.8)
10 (4.2)
17
18 (8.9)
9.0 (3.4)
17
1.03 (1.03)
1.03 (1.05)
1.04
3, 12.0
styrene, 11.0e
styrene, 19.2e
s-BuLi
3, 35.2
100
14
15
1.04
a
b
Polymerization time: 2 h for 2; 3 h for 3; 1 h for tBMA; 20 min for styrene. Homopolymers were obtained at the first-stage
polymerization of first monomer. c Mns of the block copolymers were determined by using the Mns of the homopolymers and the molar
ratios of monomer units in the block copolymer analyzed by 1H NMR. A 10-fold excess of Et2Zn was added to Ph2CHK before the
d
polymerization of first monomer. e A 2-fold excess of 1,1-diphenylethylene and a 5-fold excess of LiCl were added to the living anionic
polystyrene before the addition of second monomer.
identical conditions. For the complete conversion of 3,
the polymerization time was prolonged to 24 h. Similar
to the polymerization behavior of 2, the addition of LiCl
narrowed the MWDs of poly(3)s, while keeping the
controlled molecular weights. As expected, the binary
initiator system of Ph2CHK/Et2Zn provided the excellent
molecular weight control and the extremely narrow
MWD (Mw/Mn < 1.06) of the resulting polymers. Ph2-
CHK by itself gave poly(3) with rather broad MWD,
whereas the Mn values agreed with the value calculated
from the monomer-to-initiator ratio.
strongly depends on the counterions of anionic initiators.
The LiCl and Et2Zn additives did not influence stereo-
regularities of the resulting polymers. This is consistent
with previous reports on the anionic polymerizations of
other methacrylates in a polar solvent of THF.13,14
Although the additives affect the polymerization rates
of the (meth)acrylates by associating with the propagat-
ing chain ends, the stereoregularity of the polymers
depends primarily on the nature of the initiator coun-
terions.
Block Cop olym er iza tion of 2 a n d 3. Monomers 2
and 3 were copolymerized sequentially to synthesize
tailored block copolymers with well-defined chain ar-
chitectures, as shown in Table 2. The first-stage poly-
merization of 2 was performed with Ph2CHK/Et2Zn in
THF at -78 °C for 2 h, and then tert-butyl methacrylate
(tBMA) was added to the reaction system. The reaction
mixture was allowed to polymerize further for 1 h, and
the copolymer was quantitatively obtained after quench-
ing with methanol. Figure 1 shows that the SEC curve
of copolymer shifts from that of homopoly(2) toward the
higher molecular weight region while maintaining its
unimodal and narrow shape. The composition of each
polymer segment estimated by 1H NMR agreed with the
feed molar ratio of 2 and tBMA. The Mn values of
copolymer were consistent with the calculated values
from the monomer-to-initiator ratios. This demonstrates
that the propagating carbanion of poly(2) is sufficiently
stable to initiate the polymerization of tBMA with
We attempted to estimate the stereoregularity of the
resulting poly(2) and poly(3) by 1H and 13C NMR
spectroscopies. However, the appropriate signals were
overlapped with those of the tert-butyldimethylsilyl
protecting group. Therefore, we quantitatively converted
the poly(2) and poly(3) into their deprotected forms,
poly(DEGMA) and poly(TEGMA), under mild acidic
conditions, as shown later. The stereoregularity of the
deprotected poly(DEGMA) and poly(TEGMA) could be
evaluated independently by the 1H (R-methyl proton)
and 13C NMR (carbonyl, quaternary, and R-methyl
carbons) spectroscopies, with comparable values. The
triad tacticities obtained by the relative signal intensity
of R-methyl carbons are shown in Table 1. In the
polymerizations using organolithium initiator, the ster-
eoregularity of polymers were rather syndiotactic (rr ∼
72-75%). The organopotassium initiator always pro-
duced mr-rich configurations. The triad tacticity thus

Macromolecules, Vol. 36, No. 1, 2003
Synthesis of Water-Soluble Polymethacrylates 45
results obtained here and in the preceding section show
the living character of the polymerizations of 2 and 3
under the reaction conditions employed here, similar to
the previous polymerization result of 1.4 The tert-
butyldimethylsilyl protecting group effectively masks
the OH functionalities and suppresses the serious side
reactions during the anionic polymerizations of 1-3.
We next polymerized 2 as a second monomer to
synthesize the block copolymer with styrene. The an-
ionic living polystyrene was first synthesized by initia-
tion with s-BuLi in THF at -78 °C, and then THF
solutions of both 1,1-diphenylethylene and LiCl were
added in order to decrease the nucleophilicity of the
terminal benzylic carbanion of living polystyrene. Fi-
nally, monomer 2 in THF was added at -78 °C to the
living polystyrene capped with 1,1-diphenylethylene in
the presence of LiCl. The diblock copolymer, polystyrene-
block-poly(2), with predetermined composition and nar-
row MWD was obtained in quantitative yield. Similarly,
sequential block copolymerization of styrene and 3
smoothly proceeded with s-BuLi to give a well-defined
block copolymer. These results open the synthetic
pathway to the tailored amphiphilic block copolymer
containing poly(DEGMA) or poly(TEGMA) segment by
the sequential anionic copolymerization and the subse-
quent acidic hydrolysis of poly(2) or poly(3) segment, as
described below.
F igu r e 1. SEC curves of poly(2) (peak A, Mn ) 8900, Mw/Mn
) 1.03) and poly(2)-block-poly(tBMA) (peak B, Mn ) 18,000,
Mw/Mn ) 1.03) measured in THF.
Sch em e 2
Dep r otection of ter t-Bu tyld im eth ylsilyl Gr ou p
in P oly(2)-(3). The deprotections of tert-butyldimeth-
ylsilyl ether linkage of poly(2)-(3) were carried out to
regenerate the OH functionalities by treating with 2 N
HCl in aqueous THF at 0 °C for 2 h, as shown in Scheme
2. After the acidic hydrolyses, the deprotected polymers
were obtained in good yields. The completion of the
quantitative efficiency to give a poly(2)-block-poly-
(tBMA) with the predicted compositions and molecular
weight, and with narrow MWD. In a similar manner, a
well-defined diblock copolymer of 3 and tBMA was
produced with Ph2CHK/Et2Zn in quantitative yield. The
1
hydrolysis could be monitored by H and 13C NMR and
1
IR measurements. In the H NMR spectrum of the both
hydrolyzed polymers, the strong proton signals due to
SiC(CH3)3 (0.9 ppm) and SiCH3 (0.1 ppm) completely
F igu r e 2. 1H NMR spectra of poly(2) (A) in CDCl3 and poly(DEGMA) (B) in CD3OD. The signals attributable to solvents are
marked with asterisks (/).

46 Ishizone et al.
Macromolecules, Vol. 36, No. 1, 2003
Sch em e 3
disappeared. Figure 2 shows the 1H NMR spectra of
poly(2) and its hydrolyzed polymer. The proton signals
corresponding to the oxyethylene units are observed at
3.6-4.2 ppm after deprotection, while the shape of
signals has changed. Their observed intensity relative
to other signals revealed that the cleavage exclusively
occurred on the Si-O linkage but not on the ester
moiety. This is also supported by the fact that no trace
of carbon signals at 26 (Si(C(CH3)3), 18 (Si(C(CH3)3), and
-5 ppm (SiCH3) was detected in the 13C NMR spectrum
of the polymers obtained after hydrolyses. Furthermore,
the IR absorptions at 777, 836, and 940 cm-1 due to the
stretching and deformation vibration of Si-O-C and
Si-CH3 linkages disappeared and a broad absorption
characteristic for the OH groups newly appeared at
3100-3700 cm-1 after hydrolyses. These spectroscopic
observations substantiate the point that complete re-
movals of the tert-butyldimethylsilyl protecting groups
in poly(2) and poly(3) are attained to form poly(DEGMA)
and poly(TEGMA) under acidic conditions, as has been
reported in the transformation of poly(1) into poly-
(HEMA).4 The quantitative deprotection of poly(2) and
poly(3) also occurred under the neutral conditions by
treating with Bu4NF in THF at room temperature for
2 h, as expected.12
F igu r e 3. SEC curves of poly(2) (peak A, Mn (SEC) ) 3300,
Mw/Mn ) 1.06, DP(NMR) ) 46.4), poly(DEGMA) (peak B, Mn-
(SEC) ) 23 000, Mw/Mn ) 1.03, DP(NMR) ) 50.0), and
benzoylated poly(DEGMA) (peak C, Mn(SEC) ) 19 000, Mw/
Mn ) 1.04, DP(NMR) ) 51.0) measured in DMF containing
0.01 M LiBr.
We have examined the SEC measurement of the
resulting poly(DEGMA) in DMF containing 0.01 M LiBr,
because it was insoluble in THF. Parts A and B of
Figure 3 show the typical SEC curves of the poly(2) and
the poly(DEGMA) after hydrolysis, respectively. Very
interestingly, the SEC curve of poly(DEGMA) shifts
toward higher molecular weight region after the acid
hydrolysis with keeping their unimodal and narrow
shape, although the molecular weight of the deprotected
polymer theoretically decreases after the removal of tert-
butyldimethylsilyl protecting group. In fact, the degree
F igu r e 4. SEC curves of poly(2) (peak A, Mn ) 14 000, Mw/
Mn ) 1.06) and benzoylated poly(DEGMA) (peak B, Mn
14 000, Mw/Mn ) 1.02) measured in THF.
)
shows a narrow MWD, as can be seen in Figure 3C. The
chromatogram slightly shifts from that of poly(DEGMA)
toward the lower molecular weight side in DMF, al-
though the theoretical molecular weight increases via
the benzoylation of OH group. The poly(TEGMA-Bz)
also shows a unimodal SEC curve and a similar elution
behavior in DMF solution. The resulting benzoate
polymers were soluble in THF, and we measured their
SEC in THF solution. Figure 4 shows the SEC curves
of poly(2) and poly(DEGMA-Bz) obtained after a two-
step polymer reaction using the acidic hydrolysis and
the following benzoylation. The poly(DEGMA-Bz) elutes
at the reasonable molecular weight region in THF
solution. More importantly, the SEC curve possesses
unimodal and narrow shape similar to the chromato-
gram obtained in DMF, indicating that no side reaction
such as main chain degradation and/or cross-linking
takes place during the course of deprotection and
benzoylation. We have thus realized that the poly-
(DEGMA) and poly(TEGMA) obtained after deprotec-
tions maintain linear and well-defined structures simi-
lar to the parent protected polymers. The acidic
hydrolysis of poly(2) and poly(3) segments in the block
1
of polymerization of poly(DEGMA) estimated by the H
NMR (DP ) 50.0) was in accordance with that of poly-
(2) (DP ) 46.4) within the experimental error. The
elution behavior in SEC is probably due to the difference
in the hydrodynamic volume of the polymers before and
after deprotection in a highly polar DMF solvent.
Similar phenomenon was also observed during the
course of the hydrolysis of poly(3) to poly(TEGMA). To
further confirm the MWD of polymers after the hydroly-
sis, we quantitatively converted the polar OH groups
of poly(DEGMA) and poly(TEGMA) into their benzoyl
ester forms, poly(DEGMA-Bz) and poly(TEGMA-Bz), by
the reaction with benzoic anhydride in pyridine, as
shown in Scheme 3. 1H NMR analysis revealed that the
degree of polymerization of poly(DEGMA-Bz) (DP )
51.0) again agreed with the value of poly(DEGMA) (DP
) 50.0). The SEC curve of the poly(DEGMA-Bz) again

Macromolecules, Vol. 36, No. 1, 2003
Synthesis of Water-Soluble Polymethacrylates 47
Ta ble 3. Solu bility of P olym er sa
Exp er im en ta l Section
poly poly
poly
poly
poly
poly
Ma ter ia ls. All reagents were purchased from Tokyo Kasei,
unless otherwise stated, and purified in the usual manner.
Commercially available methacryloyl chloride and tert-bu-
tyldimethylsilyl chloride (Aldrich) were used without purifica-
tion. Di(ethylene glycol) and tri(ethylene glycol) (Koso Chemi-
cal) were dried and distilled over CaH2 under the reduced
pressure. Triethylamine, pyridine, and dichloromethane were
dried and distilled over CaH2. LiCl (Wako Pure Chemical) was
dried in vacuo for 2 days under heating and used as a THF
solution. Diethylzinc (Tosoh-Akzo) was distilled under the
reduced pressure and diluted with dry THF. Trioctylaluminum
(Sumitomo Chemical Industry) was diluted with dry heptane.
Styrene was washed with 10% aqueous NaOH solution and
water and dried over anhydrous MgSO4. It was then dried and
distilled over CaH2 in vacuo and finally distilled from the THF
solution of benzylmagnesium chloride on a vacuum line. tert-
Butyl methacrylate was distilled over CaH2 and then distilled
in the presence of trioctylaluminum (1 mol %) on a vacuum
line. 1,1-Diphenylethylene was distilled from CaH2 in vacuo
and then distilled in the presence of 1,1-diphenylhexyllithium
on a vacuum line. THF as the polymerization solvent was
refluxed over sodium wire, distilled over LiAlH4 under nitro-
gen, and finally distilled from sodium naphthalenide solution
on a vacuum line. Heptane was washed with concentrated H2-
SO4 and dried over anhydrous MgSO4, and it was dried over
P2O5 for 1 day under reflux. It was then distilled in the
presence of n-BuLi under nitrogen.
solvent
hexane
benzene
CHCl3
acetone
ethyl acetate
Et2O
1,4-dioxane
THF
DMF
DMSO
EtOH
MeOH
water
(2)b (3)c (DEGMA)d (TEGMA)e (HEMA)f (MMA)g
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
S
S
S
S
I
I
I
S
I
I
I
I
I
I
I
I
I
I
I
I
I
S
S
S
S
I
I
S
S
S
S
I
S
S
S
S
I
S
S
S
I
S
I
S
S
S
S
S
S
I
S
S
S
S
S
I
I
I
I
a
Key: I, insoluble; S, soluble. All polymer samples were
b
synthesized with s-BuLi/DPE/LiCl in THF at -78 °C. Mn
)
20 000, Mw/Mn ) 1.05. c Mn ) 19 000, Mw/Mn ) 1.08. Mn ) 7300,
d
Mw/Mn ) 1.03. e Mn ) 7000, Mw/Mn ) 1.05. f Poly(2-hydroxyethyl
g
methacrylate), Mn ) 10 000, Mw/Mn ) 1.03. Poly(methyl meth-
acrylate), Mn ) 20 000, Mw/Mn ) 1.03.
copolymers similarly proceeded to give a series of
amphiphilic block copolymers such as poly(DEGMA)-
block-poly(tBMA), poly(TEGMA)-block-poly(tBMA), poly-
styrene-block-poly(DEGMA), and polystyrene-block-
poly(TEGMA).
In itia tor s. Commercially available s-BuLi (1.3 M in cyclo-
hexane, Nacalai Tesque Inc.) was used without purification
and diluted with dry heptane. Diphenylmethylpotassium was
prepared by the reaction of potassium naphthalenide with a
1.1-fold excess of diphenylmethane in THF at room tempera-
ture for 48 h.20 The concentrations of initiators were deter-
mined by colorimetric titration using standardized 1-octanol
in THF in a sealed reactor in vacuo as previously reported.21
Di(eth ylen e glycol) ter t-Bu tyldim eth ylsilyl Eth er (DEG-
Si). A solution of tert-butyldimethylsilyl chloride (5.80 g, 38.7
mmol) in dichloromethane (30 mL) was added dropwise to a
mixture of di(ethylene glycol) (33.0 g, 307 mmol), pyridine (24.8
g, 314 mmol), and dichloromethane (60 mL) at 0 °C under
nitrogen. The mixture was stirred for 12 h at room tempera-
ture and concentrated under reduced pressure. Hexane (100
mL) was added to the residue to give two phases. The resulting
DEG-Si and the corresponding disilyl ether were extracted
from an excess of di(ethylene glycol) with hexane five times.
The combined hexane layer was concentrated in vacuo and the
residue was purified by column chromatography (silica gel,
hexane/ethyl acetate ) 10/1 to 4/1) to give pure DEG-Si (6.91
g, 31.4 mmol, 81%) as a colorless liquid. The resulting DEG-
Si was used directly for the following reaction without further
purification. 1H NMR (C6D6): δ 0.04 (s, 6H, SiCH3), 0.95 (s,
9H, Si-C-CH3), 2.27 (s, 1H, OH), 3.26-3.33 (m, 4H, OCH2CH2-
OCH2CH2OSi), 3.52 (t, 2H, J ) 5 Hz, HOCH2), 3.57 (t, 2H, J
) 5 Hz, CH2OSi). 13C NMR (C6D6): δ -5.3 (SiCH3), 18.7 (Si-
C-CH3), 26.3 (Si-C-CH3), 62.1 (HOCH2), 63.2 (CH2OSi), 72.9
and 73.0 (OCH2CH2OCH2CH2OSi). IR (neat, cm-1): 777, 834,
940, 1068, 1107, 1255, 1463, 2858, 2929, 2955, 3200-3600
(OH). Anal. Calcd for C10H24O3Si: C, 54.50, H, 10.98. Found:
C, 54.32, H, 10.83.
2-[2-[(ter t-Bu tyld im eth ylsilyl)oxy]eth oxy]eth yl Meth -
a cr yla te (2). A solution of methacryloyl chloride (5.22 g, 49.7
mmol) in ether (30 mL) was added dropwise to a mixture of
DEG-Si (7.13 g, 32.4 mmol), triethylamine (6.79 g, 67.2 mmol),
and ether (80 mL) with stirring at 0 °C under nitrogen. The
reaction mixture was stirred overnight at room temperature
and filtered to remove a precipitated triethylamine hydrochlo-
ride. The filtrate was washed with 10% aqueous NaOH
solution three times and dried over anhydrous MgSO4. After
filtration, the filtrate was concentrated under the reduced
pressure, and the residue was purified by column chromatog-
raphy (silica gel, hexane/ethyl acetate ) 10/1 to 10/3). Vacuum
distillation in the presence of a trace amount of methylene blue
gave a colorless liquid of 2 (7.20 g, 24.9 mmol, 77%, bp 86-88
Solu bility a n d Gla ss Tr a n sition Tem p er a tu r e of
P olym er s. The solubilities of polymers obtained in this
study are shown in Table 3 with those of poly(HEMA)
and poly(MMA) as the references. Poly(2) and poly(3)
were insoluble in methanol and water but soluble in a
wide range of organic solvents including hexane and
ethanol, indicating their amphiphilic characters. The
solubilities of polymers drastically changed after depro-
tection. The resulting poly(DEGMA) and poly(TEGMA)
became insoluble in nonpolar solvents such as hexane,
benzene, and diethyl ether, as expected. Most impor-
tantly, the both polymers showed excellent solubility in
water, in sharp contrast to the fact that poly(HEMA)
was not soluble in water. The observed changes in
solubility mean that the polarity of the deprotected
polymers remarkably increase during the transforma-
tions of silyl ethers to OH moieties. Hence, it is
demonstrated that the pendant di(ethylene glycol) and
tri(ethylene glycol) units in poly(DEGMA) and poly-
(TEGMA) induce the water solubility and the hydro-
philicity higher than the poly(HEMA) bearing shorter
ethylene glycol unit.
All of the polymers obtained in this study were
colorless and sticky, and their glass transition temper-
atures (Tgs) were measured by differential scanning
calorimetry (DSC). Poly(2), poly(3), poly(DEGMA), and
poly(TEGMA) presented Tg values of -83, -87, -95,
and -130 °C, respectively. The flexible oligo(ethylene
glycol) moieties in each monomer unit may afford these
very low Tg values.
In conclusion, we have succeeded in the anionic living
polymerizations of tert-butyldimethylsilyl-protected oli-
go(ethylene glycol) methacrylates, 2 and 3, to give
polymers having well-defined primary chain structures
including narrow MWDs and tailored Mns. The water-
soluble polymethacrylates, poly(DEGMA) and poly-
(TEGMA), are readily obtained by the subsequent
deprotections of the resulting polymers under the mild
acidic conditions.

48 Ishizone et al.
Macromolecules, Vol. 36, No. 1, 2003
1
°C/0.25 mmHg). H NMR (C6D6): δ 0.04 (s, 6H, SiCH3), 0.95
polymerization was terminated with degassed methanol. After
concentration of the reaction mixture in vacuo, the residue was
poured into a large excess of methanol to precipitate poly(2)
(1.46 g, 100%, Mn ) 9300, Mw/Mn ) 1.02).
(s, 9H, Si-C-CH3), 1.83 (s, 3H, R-CH3), 3.29 (t, 2H, J ) 5 Hz,
OCH2CH2OSi), 3.35 (t, 2H, J ) 5 Hz, COOCH2CH2O), 3.59 (t,
2H, J ) 5 Hz, OCH2CH2OSi), 4.14 (t, 2H, J ) 5 Hz, COOCH2-
CH2O), 5.20 and 6.16 (2s, 2H, CH2d). 13C NMR (C6D6): δ -5.2
(SiCH3), 18.6 (R-CH3), 18.7 (Si-C-CH3), 26.3 (Si-C-CH3),
63.2 (CH2OSi), 64.0 (COOCH2), 69.3 (COOCH2CH2O), 72.8
(OCH2CH2OSi), 125.3 (CH2d), 136.8 (CH2dC), 166.9 (CdO).
IR (neat, cm-1): 777, 836, 940, 1048, 1111, 1147, 1168, 1255,
1297, 1320, 1463, 1473, 1641, 1722 (CdO), 2853, 2931, 2956.
Anal. Calcd for C14H28O4Si: C, 58.29, H, 9.78. Found: C, 58.22,
H, 9.94.
Tr i(et h ylen e glycol) ter t-Bu t yld im et h ylsilyl E t h er
(TEG-Si). A procedure similar to that described above for
DEG-Si was followed using tri(ethylene glycol) (37.8 g, 250
mmol), tert-butyldimethylsilyl chloride (5.80 g, 38.7 mmol), and
pyridine (27.0 g, 342 mmol). Column chromatography (silica
gel, hexane/ethyl acetate ) 10/1-3/1) gave TEG-Si (7.40 g, 31.2
mmol, 73%) as a colorless liquid. The resulting TEG-Si was
directly used for the following reaction without further puri-
fication. 1H NMR (C6D6): δ 0.05 (s, 6H, SiCH3), 0.95 (s, 9H,
Si- C-CH3), 3.18 (s, 1H, OH), 3.46-3.53 (m, 8H, OCH2CH2-
OCH2CH2OCH2CH2OSi), 3.72-3.79 (m, 4H, HOCH2, and CH2-
OSi). 13C NMR (C6D6): δ -5.4 (SiCH3), 18.7 (Si-C-CH3), 26.3
(Si-C-CH3), 62.1 (HOCH2), 63.2 (CH2OSi), 70.8, 71.2, 73.0,
and 73.1 (OCH2CH2OCH2CH2OCH2CH2OSi). IR (neat, cm-1):
777, 836, 937, 1111, 1142, 1255, 1464, 1473, 2858, 2929, 2953,
3100-3600 (OH). Anal. Calcd for C12H28O4Si: C, 54.51, H,
10.67. Found: C, 53.99, H, 10.19.
Poly(2) and poly(3) were further purified by reprecipitations
in a THF/methanol system and by freeze-drying from benzene
solution. Polymers thus obtained were characterized by 1H and
13C NMR and IR spectroscopies. The following is the full list.
P oly(2). 1H NMR (CDCl3): δ 0.11 (s, 6H, SiCH3), 0.94 (s,
9H, Si-C-CH3), 0.9-1.2 (m, 3H, R-CH3), 1.8-2.1 (br, 2H,
CH2), 3.56 (bs, 2H, OCH2CH2OSi), 3.70 (bs, 2H, COOCH2CH2O),
3.79 (bs, 2H, CH2CH2OSi), 4.10 (bs, 2H, COOCH2CH2O). 13C
NMR (CDCl3): δ -5.1 (SiCH3), 18.4 (Si-C-CH3), 18-20 (R-
CH3), 26.1 (Si-C-CH3), 45 (main chain quarternary), 54 (main
chain CH2), 62.9 (OCH2CH2OSi), 63.9 (COOCH2), 68.7 (CO-
OCH2CH2O), 72.7 (CH2OSi), 177 (CdO). IR (KBr, cm-1): 777,
836, 940, 1108, 1147, 1253, 1733 (CdO), 2856, 2929, 2952.
P oly(3). 1H NMR (CDCl3): δ 0.10 (s, 6H, SiCH3), 0.93 (s,
9H, Si- C-CH3), 0.9-1.2 (m, 3H, R-CH3), 1.8-2.2 (br, 2H,
CH2), 3.58 (t, J ) 5 Hz, 2H, OCH2CH2OSi), 3.66 (bs, 4H, OCH2-
CH2OCH2CH2OCH2CH2OSi), 3.69 (bs, 2H, COOCH2CH2O),
3.79 (t, J ) 5 Hz, 2H, CH2CH2OSi), 4.11 (bs, 2H, COOCH2-
CH2O). 13C NMR (CDCl3): δ ) -5.1 (SiCH3), 18.5 (Si-C-CH3),
17-20 (R-CH3), 26.1 (Si-C-CH3), 45 (main chain quarter-
nary), 54 (main chain CH2), 62.7 (OCH2CH2OSi), 63.8 (CO-
OCH2), 68.5 (COOCH2CH2O), 70.6 and 70.8 (OCH2CH2OC-
H2CH2OCH2CH2OSi), 72.7 (CH2OSi), 177 (CdO). IR (KBr,
cm-1): 777, 836, 940, 1111, 1147, 1253, 1463, 1473, 1733 (Cd
O), 2858, 2929, 2957.
2-[2-[2-[(ter t-Bu t yld im et h ylsilyl)oxy]et h oxy]et h oxy]-
eth yl Meth a cr yla te (3). The same procedure was followed
as described above for 2 using methacryloyl chloride (5.11 g,
48.7 mmol), triethylamine (9.83 g, 97.4 mmol), and TEG-Si
(7.82 g, 32.6 mmol) in place of DEG-Si. The product was
purified by column chromatography (silica gel, hexane/ethyl
acetate ) 10/1 to 10/3) and the subsequent vacuum distillation
in the presence of methylene blue to afford a colorless liquid
Dep r otection of P olym er s. Two methods were used to
remove tert-butyldimethylsilyl protecting group of poly(2) and
poly(3) with either Bu4NF or aqueous HCl in THF. The typical
procedures using poly(2) were shown below.
Meth od A. Bu4NF (10 mL of a 1 M THF solution) was added
dropwise to poly(2) (0.21 g, 0.73 mmol based on the monomer
unit) at room temperature, and the solution was stirred for 2
h. After concentration under reduced pressure, the residue was
dissolved in ethanol, and the solution was poured into a large
excess of hexane. The complete removal of the trialkylsilyl
group was clarified by the 1H NMR measurement of the
resulting polymer.
Meth od B. Aqueous 2 N HCl (1 mL) was added dropwise
to a solution of poly(2) (0.40 g, 1.4 mmol based on the monomer
unit, DP ) 46.4, Mw/Mn ) 1.06) in THF (10 mL) at 0 °C, and
the homogeneous mixture was stirred at 0 °C for 2 h. After
concentration in vacuo, the deprotected polymer was dissolved
in ethanol and then precipitated in hexane. The resulting poly-
(DEGMA) (0.22 g, 1.3 mmol, 93%, DP ) 50.0, Mw/Mn ) 1.03))
was purified by freeze-drying from 1,4-dioxane containing a
small amount of methanol. The deprotection of poly(3) was
carried out similarly to afford poly(TEGMA) quantitatively.
The deprotected polymers were characterized by 1H and 13C
NMR and IR measurements as follows.
1
of 3 (8.76 g, 26.4 mmol, 81%, bp 106-110 °C/0.3 mmHg). H
NMR (C6D6): δ 0.06 (s, 6H, SiCH3), 0.96 (s, 9H, Si- C-CH3),
1.82 (s, 3H, R-CH3), 3.37 (m, 8H, OCH2CH2OCH2CH2OCH2-
CH2OSi), 3.64 (t, 2H, J ) 5 Hz, CH2OSi), 4.15 (COOCH2), 5.19
and 6.15 (2s, 2H, CH2d). 13C NMR (C6D6): δ -5.1 (SiCH3),
18.4 (R-CH3), 18.5 (Si-C-CH3), 26.1 (Si-C-CH3), 63.1
(SiOCH2), 64.0 (COOCH2), 69.3, 70.9, 71.0, and 73.0 (OCH2C-
H2OCH2CH2OCH2CH2OSi), 125.2 (CH2d), 136.8 (CH2dC),
166.9 (CdO). IR (neat, cm-1): 777, 836, 940, 1105, 1147, 1168,
1255, 1298, 1320, 1463, 1641, 1722 (CdO), 2857, 2931, 2955.
Anal. Calcd for C16H32O5Si: C, 57.80, H, 9.70. Found: C, 57.73,
H, 9.82.
P u r ifica tion of Mon om er s. After careful fractional distil-
lation, monomers 2 and 3 were degassed and sealed off in an
apparatus equipped with a break-seal in the presence of CaH2
and diluted with dry heptane. The monomer solution in
heptane was stirred for 20 h at room temperature and distilled
from CaH2 on a vacuum line into ampules fitted with break-
seals. The distilled monomers were treated with 1-2 mol %
of trioctylaluminum in heptane for 10 min and again distilled
under high vacuum conditions. The purified monomers were
finally distilled in vacuo into an ampule fitted with a break-
seal and diluted with dry THF. The resulting monomer
solutions (0.2-0.3 M) in THF were stored at -30 °C until
ready to use for the anionic polymerization.
P olym er iza tion P r oced u r es. All polymerizations were
carried out at -78 °C in an all-glass apparatus equipped with
break-seals under high vacuum conditions as previously
reported.21 A typical polymerization procedure was as fol-
lows: A THF solution (2.51 mL) of 1,1-diphenylethylene (0.188
mmol) was added to a heptane solution (4.33 mL) of s-BuLi
(0.142 mmol) through the break-seal at -78 °C. After 10 min,
LiCl (0.535 mmol) in THF (3.69 mL) was added to the mixture
at -78 °C, and the initiator system was allowed to stand at
-78 °C for 10 min. Then, monomer 2 (4.98 mmol) in THF (20.5
mL) was rapidly added to the initiator system at -78 °C
through the break-seal with vigorous shaking of the apparatus.
After the reaction was allowed to stand at -78 °C for 2 h, the
P oly(DEGMA). 1H NMR (CD3OD): δ 0.8-1.3 (m, 3H,
R-CH3), 1.8-2.2 (br, 2H, CH2), 3.62 (bs, 2H, CH2OH), 3.74 (bs,
4H, COOCH2CH2OCH2CH2OH), 4.16 (bs, 2H, COOCH2). 13C
NMR (CD3OD): δ 16-20 (R-CH3), 44-45 (main chain quar-
ternary), 54 (main chain CH2), 60.4 (OCH2CH2OH), 63.7
(COOCH2), 67.7 (COOCH2CH2O), 71.7 (CH2OH), 177 (CdO).
IR (KBr, cm-1): 1037, 1068, 1132, 1162, 1271, 1453, 1728 (Cd
O), 2876, 2943, 3100-3700 (OH).
P oly(TEGMA). 1H NMR (CD3OD): δ 0.8-1.3 (m, 3H,
R-CH3), 1.8-2.2 (br, 2H, CH2), 3.65 (bs, 2H, CH2OH), 3.72 (bs,
6H, COOCH2CH2OCH2CH2OCH2CH2OH), 3.8 (bs, 2H, COO-
CH2CH2O), 4.16 (bs, 2H, COOCH2). 13C NMR (CD3OD): δ 16-
20 (R-CH3), 44-45 (main chain quarternary), 54 (main chain
CH2), 60.4 (OCH2CH2OH), 63.4 (COOCH2), 67.8 (COOCH2-
CH2O), 69.6 (OCH2CH2O), 71.9 (CH2OH), 177 (C ) O). IR
(KBr, cm-1): 1068, 1126, 1249, 1728 (CdO), 2875, 2929, 3100-
3700 (OH).
Ben zoyla tion of P olym er s. Benzoic anhydride (1.85 g, 8.2
mmol) in dry pyridine (2 mL) was added in several portions
to a solution of poly(DEGMA) (0.10 g, 0.58 mmol based on the
monomer unit, DP ) 50.0, Mw/Mn ) 1.03) in pyridine (3 mL)
at 0 °C under nitrogen. The reaction mixture was stirred at

Macromolecules, Vol. 36, No. 1, 2003
Synthesis of Water-Soluble Polymethacrylates 49
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room temperature for 24 h. After concentration in vacuo, the
residue was dissolved in THF, and the solution was poured
into water to precipitate. The resulting polymer was further
purified by the reprecipitations from a THF/hexane system and
by the freeze-drying from the benzene solution. The yield of
the benzoylated poly(DEGMA), poly(DEGMA-Bz) (0.17 g, 0.58
mmol based on the monomer unit, DP ) 51.0, Mw/Mn ) 1.04),
was quantitative. The benzoylation of poly(TEGMA) was
performed similarly to afford the corresponding benzoylated
1
poly(TEGMA), poly(TEGMA-Bz). The H NMR spectra of the
resulting polymers indicated that the complete benzoylations
of poly(DEGMA) and poly(TEGMA) proceeded as follows.
P oly(DEGMA-Bz). 1H NMR (CDCl3): δ 0.7-1.3 (m, 3H,
R-CH3), 1.6-2.2 (br, 2H, CH2), 3.68 and 3.76 (2bs, 4H,
COOCH2CH2OCH2CH2OCOPh), 4.09 (bs, 2H, COOCH2), 4.44
(bs, 2H, CH2OCOPh), 7.3-8.2 (m, 5H, aromatic).
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Teyssie´, Ph.; Varshney, S. K. Macromolecules 1987, 20, 1442.
(b) Varshney, S. K.; Hautekeer, J . P.; Fayt, R.; J e´roˆme, R.;
Teyssie´, Ph. Macromolecules 1990, 23, 2618.
(14) Ozaki, H.; Hirao, A.; Nakahama, S. Macromol. Chem. Phys.
1995, 196, 2099.
(15) (a) Ishizone, T.; Yoshimura, K.; Hirao, A.; Nakahama, S.
Macromolecules 1998, 31, 8706. (b) Kobayashi, M.; Okuyama,
S.; Ishizone, T.; Nakahama, S. Macromolecules 1999, 32,
6466.
P oly(TEGMA-Bz). 1H NMR (CDCl3): δ 0.7-1.3 (m, 3H,
R-CH3), 1.7-2.2 (br, 2H, CH2), 3.66 and 3.82 (2bs, 8H,
COOCH2CH2OCH2CH2OCH2CH2OCOPh), 4.09 (bs, 2H, CO-
OCH2), 4.47 (bs, 2H, CH2OCOPh), 7.3-8.2 (m, 5H, aromatic).
Mea su r em en ts. 1H and 13C NMR spectra were recorded
on a Bruker DPX300 (300 MHz for 1H and 75 MHz for 13C) in
C6D6, CD3OD, or CDCl3. Tacticity of poly(DEGMA) and poly-
(TEGMA) was determined by the 13C NMR integral ratio of
three split R-methyl carbon signals appearing at 18.5-23.7
ppm. Three signals were assigned as mm (22.7-23.7 ppm),
mr (20.2-21.4 ppm), and rr (18.5-19.5 ppm) triads. Infrared
spectra (KBr disk or neat) were recorded on a J EOL J IR-
AQS20M FT-IR spectrophotometer. SEC chromatograms for
determination of molecular weight distribution were obtained
in THF at 40 °C at a flow rate of 1.0 mL min-1 with a TOSOH
HLC-8020 instrument equipped with a series of polystyrene
gel columns (TOSOH G5000HXL, G4000HXL, and G3000HXL
,
measurable molecular weight range: 2 × 103 to 4 × 106) and
with ultraviolet (254 nm) or refractive index detection. SEC
measurements ware also performed in DMF containing 0.01
M LiBr at 40 °C at a flow rate of 1.0 mL min-1 with a TOSOH
HLC-8120 instrument equipped with three polystyrene gel
columns (TOSOH GMHXL, × 2 and G2000HXL, measurable
molecular weight range: 103 to 4 × 108). The Tgs of the
polymers were measured by DSC using a Seiko Instrument
DSC220 apparatus, calibrated with indium and tin, and
analyzed by a SSC5200TA station. The samples were first
heated to 100 °C, cooled rapidly to -150 °C with liquid
(16) (a) Kunkel, D.; Mu¨ller, A. H. E.; J anata, M.; Lochmann, L.
Makromol. Chem., Macromol. Symp. 1992, 60, 315. (b)
Yakimansky, A. V.; Mu¨ller, A. H. E.; Van Beylen, M.
Macromolecules 2000, 33, 5686.
(17) (a) Ozaki, H.; Hirao, A.; Nakahama, S. Macromolecules 1992,
25, 1391. (b) Hild, G.; Lamps, J . P.; Rempp, P. Polymer 1993,
34, 2875. (c) Creutz, S.; Teyssie´, Ph.; J e´roˆme, R. Macromol-
ecules 1997, 30, 6. (d) Ishizone, T.; Uehara, G.; Hirao, A.;
Nakahama, S.; Tsuda, K. Macromol. Chem. Phys. 1998, 199,
1827. (e) Zhang, H.; Ruckenstein, E. Macromolecules 1998,
31, 746. (f) Ishizone, T.; Sugiyama, K.; Sakano, Y.; Mori, H.;
Hirao, A.; Nakahama, S. Polym. J . 1999, 31, 983. (g) Zhang,
H.; Ruckenstein, E. Macromolecules 2001, 34, 3587. (h)
Ishizone, T.; Tajima, H.; Torimae, H.; Nakahama, S. Macro-
mol. Chem. Phys., in press.
nitrogen, and then scanned again at a rate of 5 or 10 °C min-1
.
Ack n ow led gm en t. This research was supported by
Grant-in Aid for Scientific Research on Priority Areas,
“New Polymers and Their Nano-Organized Systems”
(08246102), from the Ministry of Education, Science,
Sports, and Culture, J apan. T.I. thanks the Shorai
Foundation and Iwatani Foundation for their financial
support.
(18) Anderson, B. C.; Andrews, G. D.; Arthur, J r., P.; J acobson,
H. W.; Melby, L. R.; Playtis, A. J .; Sharkey, W. H. Macro-
molecules 1981, 14, 1599.
(19) The observed Mn value increased with increasing the monomer-
to-initiator ratio, while apparent deviation in Mn value was
observed (Table 1, run 7). This is probably due to the trace
amount of impurity in the monomer, resulting in the partial
loss of initiator at the initial stage of polymerization.
(20) Varshney, S. K.; J acobs, C.; Hautekeer, J . P.; Bayard, P.;
J e´roˆme, R.; Fayt, R.; Teyssie´, Ph. Macromolecules 1991, 24,
4997.
Refer en ces a n d Notes
(1) (a) Morton, M. Anionic Polymerization: Principles and
Practice; Academic Press: New York, 1983. (b) Hsieh, H. L.;
Quirk, R. P. Anionic Polymerization; Marcel Dekker: New
York, 1996.
(2) (a) Nakahama, S.; Hirao, A. Prog. Polym. Sci. 1990, 15, 299.
(b) Hirao, A.; Nakahama, S. Trends Polym. Sci. 1994, 2, 267.
(21) Hirao, A.; Takenaka, K.; Packrisamy, S.; Yamaguchi, K.;
Nakahama, S. Makromol. Chem. 1985, 186, 1157.
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