Controlled radical polymerization and copolymerization of 5-methylene-2-phenyl-1,3-dioxolan-4-one by ATRP

Article abstract of DOI:10.1021/ma050393s

The polymerization and copolymerization of a cyclic acrylate, 5-methylene-2-phenyl-1,3-dioxolan-4-one (MPDO), by conventional radical polymerization and atom transfer radical polymerization (ATRP), were determined to occur by 1,2-vinyl addition according

Full text of DOI:10.1021/ma050393s

Macromolecules 2005, 38, 5581-5586
5581
Controlled Radical Polymerization and Copolymerization of
5
-Methylene-2-phenyl-1,3-dioxolan-4-one by ATRP
†
‡
‡
,§
Quinn Smith, Jinyu Huang, Krzysztof Matyjaszewski, and Yueh-Lin Loo*
Chemical Engineering Department and Center for Nano- and Molecular Science and Technology,
University of Texas at Austin, Austin, Texas 78712, and Chemistry Department,
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Received February 23, 2005; Revised Manuscript Received April 18, 2005
ABSTRACT: The polymerization and copolymerization of a cyclic acrylate, 5-methylene-2-phenyl-1,3-
dioxolan-4-one (MPDO), by conventional radical polymerization and atom transfer radical polymerization
(
ATRP), were determined to occur by 1,2-vinyl addition according to 13C NMR spectroscopy. Copolym-
erization of MPDO with methyl methacrylate (MMA) or styrene (S) led to copolymers with a much higher
MPDO content than originally in the feed, suggesting high reactivity due to its captodative structure.
PMPDO-PS copolymers were stable to UV irradiation and basic environments, confirming that
copolymerization of MPDO also proceeded by 1,2-vinyl addition rather than ring opening. DSC heating
scans of PMPDO-PMMA copolymers show a single T
g
that increases with increasing MPDO content.
Introduction
Scheme 1. Cyclic Monomers that undergo
Ring-Opening and/or Addition Free Radical
Polymerization
Over the past two decades, significant effort has been
devoted to exploring the radical polymerization mech-
1-13
anism of cyclic ketene acetals (CKAs)
(1-3, Scheme
(4 and 5, Scheme
). Because of the presence of ring strain, these mono-
1
,6,13-15
1
1
) and cyclic acrylates (CAs)
mers can potentially undergo ring-opening polymeriza-
tion in addition to the more conventional 1,2-vinyl
addition. Ring-opening polymerization of CKAs and CAs
has generated significant interest because this route
incorporates ester and R-keto ester functionality, re-
spectively, into the backbone of the resulting polymers
(
Scheme 2). These polymers are therefore degradable
Scheme 2. Ring-Opening Mechanism for CKA and CA
Monomers
upon exposure to an acidic or basic environment or to
1
,3,7,12,13,16,17
ultraviolet irradiation.
For this reason, CKA
and CA polymers are attractive candidates in medical
and lithographic applications.
1
,12,18
Scheme 2 illustrates the mechanism of radical ring-
opening polymerization for both the CKA and CA
monomers. Whether ring-opening (as outlined in Scheme
2
) is favored over 1,2-vinyl addition during polymeri-
zation depends on the relative kinetics of monomer
addition and ring opening. The radical polymerization
of CKAs has been examined in detail, and the factors
that influence the degree of ring opening in these
monomers are generally known. To first approximation,
the extent of ring substitution and the magnitude of ring
strain in the monomer can affect the degree of ring
reaction temperatures (e.g., 50 °C), this monomer
undergoes 100% ring opening.2
,3,9,13
Similarly, CKA 3,
opening dramatically. For example, CKA 1a undergoes
5
also a monomer with seven-membered ring, undergoes
complete ring opening during radical polymerization; its
resulting propagating species is presumably even more
stable than that of CKA 1c due to the presence of the
phenyl ring.5
While the polymerization of CKAs is generally un-
derstood, the synthesis of CKA polymers of high mo-
lecular weight remains challenging. The CKA polymers
that result from conventional radical polymerization
typically have low molecular weights (<10 kg/mol) and
broad molecular weight distribution, presumably be-
cause of the low reactivity of such vinyl-ether-type cyclic
monomers. With the recent advent of controlled/“living”
radical polymerization techniques, biodegradable CKA
polymers with controlled molecular weights and narrow
0% ring-opening polymerization at 60 °C.9
,13
The
addition of a phenyl pendant groupswhich tends to
stabilize the propagating radicalsto the monomer (CKA
,19-21
2
) allows for complete ring opening during conventional
8
,9
radical polymerization at 60 °C.
The increase in
monomer ring strain in the case of CKA 1c greatly
favors ring opening during polymerization. Even at low
*
To whom correspondence should be addressed. E-mail: lloo@
che.utexas.edu.
†
Chemical Engineering Department, University of Texas at
Austin.
‡
Carnegie Mellon University.
§
Chemical Engineering Department and Center for Nano- and
Molecular Science and Technology, University of Texas at Austin.
1
0.1021/ma050393s CCC: $30.25 © 2005 American Chemical Society
Published on Web 05/25/2005

5582 Smith et al.
Macromolecules, Vol. 38, No. 13, 2005
molecular weight distributions have been obtained.22-28
Yet, to our best knowledge, CKA polymers of high
molecular weight have not been reported.
alumina to remove impurities and then placed on a vacuum
line where ether and excess diisopropylamine were removed
by distillation to give 3.14 g (17.8 mmol, 85%) of MPDO.
Anisole was condensed into the flask containing MPDO to
protect the monomer from air and moisture as it has been
In light of these challenges associated with CKAs, we
have chosen to focus on the radical polymerization of
CA 5a, 5-methylene-2-phenyl-1,3-dioxolan-4-one (MPDO).
In contrast to what had been reported for CKA poly-
mers, we have been able to obtain PMPDO of high
molecular weights (>40 000 g/mol). When MPDO is
polymerized by a “living” technique, i.e., atom transfer
1
4,15 1
reported to be unstable when isolated.
3
H NMR (CDCl ,
13
ppm): 4.98 (1H, d), 5.28 (1H, d), 6.68 (1H, s), 7.46 (5H, s).
C
2
NMR: 92.3 (H CdC), 103.2 (O-CHPh-O), 126.1, 128.9, 130.8,
and 134.5 (aromatic carbons), 143.7 (H CdC), 162.2 (CdO).
2
ATRP Homo- and Copolymerization of MPDO. MPDO
(2.5 g, 14.2 mmol) in 2 mL of anisole, CuBr (28.6 mg, 0.20
mmol), CuBr (2.2 mg, 0.010 mmol), PMDETA (36.4 mg, 0.21
2
2
9-32
radical polymerization (ATRP),
mer has a narrow molecular weight distribution (PDI
1.2). Although MPDO is the only CA monomer
the resulting poly-
mmol), and an additional 2 mL of anisole were added to a 15
mL flask equipped with a magnetic stir bar. During copolym-
erization, MMA or S comonomer was also added to the reaction
flask. The flask was sealed with a septum and purged with
<
studied, we expect the controlled polymerization of other
CAssthose containing both ester (electron withdrawing)
and ether (electron donating) groups in the ringsto yield
polymers of high molecular weight and narrow molec-
ular weight distribution due to the stabilizing captoda-
2
N for 1 h followed by injection of 39.0 mg (0.20 mmol) of EBiB.
The solution was purged and allowed to stir at room temper-
ature for an additional 30 min. The reaction flask was then
placed in an oil bath preheated to 70 °C for 90 min. After the
specified time, it was removed from the oil bath and cooled to
0 °C, and the solution was exposed to air. The polymerization
medium was diluted with THF and passed through a column
of neutral alumina to remove copper salts. It was then
concentrated and the polymer precipitated into MeOH. The
filtered polymer was dried in vacuo for 24 h.
3
3
tive effect on the active radical carbon.
On the basis of what had been previously reported
on CKA polymerization mechanism, we expected the
polymerization of MPDO to proceed by ring opening.
Yet, we found that MPDO polymerization proceeds
solely by 1,2-vinyl addition at all the reaction conditions
we explored. In addition to homopolymerization, we also
explored the copolymerization of MPDO with methyl
methacrylate (MMA) and with styrene (S). During
copolymerization, MPDO also undergoes 1,2-vinyl ad-
dition rather than ring opening.
Conventional Radical Polymerization of MPDO. MPDO
2.5 g, 14.2 mmol) in 2 mL of anisole, AIBN (16.4 mg, 0.10
(
mmol), and an additional 2 mL of anisole were added to a 15
mL flask equipped with a magnetic stir bar. The reaction flask
was sealed and purged with N
2
for 30 min. The flask was then
placed in an oil bath preheated to 150 °C and allowed to stir
therein for 200 min. The final polymer solution was exposed
to air and concentrated by rotary evaporation, and the polymer
was precipitated in MeOH. The filtered polymer was dried in
vacuo for 24 h.
Degradation of PMPDO-PS Copolymers. PMPDO-
PS-I was exposed to basic conditions for hydrolytic degradation
experiments. Specifically, 0.1 g of the copolymer was dissolved
in a mixture of THF (3 mL) and methanol (1 M KOH, 2.5 mL)
in a 20 mL vial. The mixture was heated to 70 °C, and the
molecular weight change was monitored by GPC. Photodeg-
radation was carried out on a 2% w/v THF solution of
PMPDO-PS-II in a Rayonet photochemical chamber reactor
equipped with 12 RPR-254 nm lamps at 40 °C for 25 h.
Experimental Section
Materials. Methyl methacrylate (Acros, 99%) and styrene
Aldrich, 99%) were passed through a column of activated basic
(
alumina and stored over molecular sieves prior to use. Anisole
Acros, 99%) and benzene (Fisher, 99+%) were dried over CaH
and MgSO , respectively. R,R′-Azoisobutyronitrile (AIBN, Al-
drich, 98%) was recrystallized from MeOH. Benzaldehyde
Aldrich, 99.5%), p-toluenesulfonic acid (Acros, 99%), diiso-
propylamine (Acros, 99+%), CuBr (Aldrich, 98%), CuBr
Aldrich, 98%), ethyl 2-bromoisobutyrate (EBiB, Aldrich, 98%),
(
2
4
(
2
(
and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA,
Aldrich, 99%) were used as received. â-Chlorolactic acid was
34
synthesized according to a previously reported procedure, and
1
Characterization. Molecular weights and molecular weight
distributions were determined using a GPC system equipped
with a Waters 515 HPLC solvent pump, two PLgel mixed-C
columns (5 µm bead size, Polymer Laboroatories Inc.) con-
nected in series, an online interferometric refractometer
the structure was confirmed by H NMR: (CDCl
2H, m) 4.61 (1H, t).
Synthesis of 2-Phenyl-5-chloromethyl-1,3-dioxolan-4-
3
, ppm) 3.91
(
1
5
one (PCDO). A similar procedure to Bailey et al. using
â-chlorolactic acid as a precursor rather than â-bromolactic
acid was used to synthesize PCDO. â-Chlorolactic acid (22.66
g, 0.182 mol), p-toluenesulfonic acid (0.433 g, 2.5 mmol),
benzaldehyde (18.4 g, 0.173 mol), and 130 mL of dry benzene
were added to a 250 mL flask. The flask was equipped with a
Dean-Stark trap to collect water, and the solution was heated
to reflux for 36 h. When the reaction was completed, the
(
Optilab DSP, Wyatt Technology Corp.), and a multiangle laser
light scattering (MALLS) detector (DAWN-EOS, Wyatt Tech-
nology Corp.). THF was used as the mobile phase at a flow
1
3
rate of 1.0 mL/min at 30 °C. C NMR spectroscopy was
performed on a Varian INOVA 500 MHz spectrometer, and
1
H NMR spectroscopy was performed on a Varian Unity+ 300
MHz NMR spectrometer. The 2D NMR spectroscopy experi-
ments were recorded on a Bruker Avance DMX-500 spectrom-
benzene solution was washed with an aqueous NaHCO
solution followed by an aqueous NaCl solution and then dried
3
1
13
eter operating at 500.13 MHz ( H) and 127.76 MHz ( C). 2D
4
over MgSO . Benzene was then removed under partial vacuum,
1
13
H- C correlation experiments (edited-HSQC) were acquired
and the remaining solution was distilled to give 15.5 g (40%)
in a 5 mm z-gradient broad-band inverse probe using Bruker
standard pulse sequences provided with the XWIN NMR 3.5
software package. The edited-HSQC experiment was recorded
in echo-antiecho mode using the hsqcedetgp pulse program
of PCDO, which was collected between 140 and 150 °C under
1
vacuum. H NMR (CDCl
3
, ppm) confirms structure: 3.97 (2H,
d,d), 4.78, 4.83 (1H, m), 6.45, 6.72 (1H, s) 7.44-7.50, 7.59-
.61 (5H, m).
7
35
optimized for a C-H coupling constant of 145 Hz. Differential
scanning calorimetry (DSC) was performed on a Perkin-Elmer
DSC 7 with a heating rate of 10 °C/min. Glass transition
Synthesis of 5-Methylene-2-phenyl-1,3-dioxolan-4-one
15
(
MPDO). The procedure outlined by Bailey et al. for the final
step of MPDO synthesis was modified as follows: A 100 mL
flask containing 4.5 g (21 mmol) of PCDO and 40 mL of dry
g
temperatures (T ) were measured on second heat at the
extrapolated half heat capacity.
ether was sealed with a septum under N
2
. Diisopropylamine
(
2.36 g, 23 mmol) was added dropwise via a syringe, and the
Results and Discussion
solution was allowed to stir at room temperature overnight.
The precipitated ammonium salts were then removed by filtra-
tion, and the remaining solution was washed with water. The
solution was subsequently passed through a column of neutral
Homopolymerization of MPDO. Homopolymeriza-
tions of MPDO were carried out in anisole, by both
conventional radical polymerization and ATRP, and the

Macromolecules, Vol. 38, No. 13, 2005
Polymerization of MPDO by ATRP 5583
Table 1. Polymer Composition and Molecular Weight Data for PMPDO Homopolymer, PMPDO-PMMA, and PMPDO-PS
Copolymers
monomer feed (mol %)
polymer composition (mol %)h
sample
PMPDOa
MPDO
comonomer
PMPDO
comonomer
Mni
PDI
100
100
100
5
100
100
100
5
44 000
52 000
51 000
15 400
11 000
11 200
9500
1.48
1.67
1.18
1.12
1.29
1.51
1.18
1.13
b
PMPDO
PMPDOc
PMPDO-PMMA-Id
PMPDO-PMMA-II
95
91
86
94
94
95
68
42
85
88
e
9
32
f
PMPDO-PMMA-III
14
6
58
g
PMPDO-PS-I
15
g
PMPDO-PS-II
6
12
16 000
a
AIBN]0/[MPDO]0 ) 1/920, 60 °C, 400 min. b [AIBN]0/[MPDO]0 ) 1/142, 150 °C, 200 min. [I]0/[CuBr]0/[CuBr2]0/[PMDETA]0/[MPDO]0
c
[
d
)
)
1/1/0.05/1.05/71, 70 °C, 360 min, PMPDO dn/dc ) 0.10 mL/g (690 nm, THF, 30 °C). [I]0/[CuBr]0/[CuBr2]0/[PMDETA]0/[MMA]0/[MPDO]0
e
f
1/1/0.05/1.05/150/7.5, 70 °C, 90 min. [I]0/[CuBr]0/[CuBr2]0/[PMDETA]0/[MMA]0/[MPDO]0 ) 1/1/0.05/1.05/138/14, 70 °C, 90 min. [I]0/
g
[
CuBr]0/[CuBr2]0/[PMDETA]0/[MMA]0/[MPDO]0 ) 1/1/0.05/1.05/125/21, 70 °C, 90 min. [I]0/[CuBr]0/[CuBr2]0/[PMDETA]0/[S]0/[MPDO]0
1
i
)
1/1/0.05/1.05/200/12, 90 °C. h Determined by peak integration in H NMR spectra. Determined by GPC using MALLS.
resulting polymers were characterized by GPC and 13C
NMR spectroscopy. The conditions for each polymeri-
zation, as well as resulting MW and polydispersity
indices (PDI ) Mw/Mn), are summarized in Table 1. As
shown in the first two entries of Table 1, we carried out
two conventional radical polymerizations, one at 60 °C
spectrum of PMPDO indicates that the polymerizations
proceeded by 1,2-vinyl addition. Further evidence that
the polymerizations proceeded by 1,2-vinyl addition, and
not ring opening, stems from the retention of the peak
13
at ∼100 ppm (labeled d in Figure 1) in the C NMR
spectra of the polymers. This peak is present in the
MPDO monomer spectrum and corresponds to the acetal
benzylic carbon. As illustrated in Scheme 3, the benzylic
carbon can only remain in its same nuclear environment
when the monomer is incorporated by 1,2-vinyl addition.
Should MPDO undergo ring-opening polymerization
instead, the nuclear environment of this particular
carbon would change dramatically. Contrary to previous
1
3
and the other at 150 °C. The C NMR spectra of the
MPDO monomer (Figure 1a) and the homopolymers
synthesized by ATRP (Figure 1b) and conventional
radical polymerization at 150 °C (Figure 1c) are shown
1
3
in Figure 1. The C NMR spectra for PMPDO synthe-
sized by conventional radical polymerization, at both 60
°
C and 150 °C, and by ATRP are identical, indicating a
reports,1
,13-15
our C NMR analysis thus indicates
13
common mechanism for both polymerization techniques
at temperatures as high as 150 °C. More importantly,
the absence of the ketone peak of the R-ketoester (190
unambiguously that MPDO undergoes 1,2-vinyl addi-
tion rather than ring-opening polymerization.
3
6
13
ppm) sevidence of ring openingsin the C NMR
Past reports concerning MPDO polymerization mech-
anism have been ambiguous. For example, Bailey and
Feng reported that MPDO and CA 5b underwent 100%
ring opening at 120 °C in tert-butylbenzene.15 They drew
this conclusion based on similarities in UV spectra
between the resulting PMPDO and pyruvic acid. In
another studysat reaction temperatures merely 10 °C
higher than the previous studysBailey et al. concluded
that the polymerization of MPDO proceeded by 1,2-vinyl
1
addition instead of ring opening. In a third study by
Bailey and co-workers, where the polymerization was
carried out at yet a higher temperature of 140 °C,13 the
authors concluded the polymerization of MPDO pro-
ceeded by ring opening. Yet, many of these studies were
not substantiated by direct structural characterization.
The polymerizations we carried outswhether by
conventional radical polymerization or by ATRPs
Scheme 3. Two Possible Mechanisms for MPDO
Homopolymerization
1
3
Figure 1. C NMR spectra of and peak assignments for (a)
MPDO monomer, (b) PMPDO by ATRP, (c) PMPDO by
conventional radical polymerization, (d) PMPDO-PS-I, and
(
e) PMPDO-PMMA-I. The presence of peak d strongly indi-
cates that the MPDO polymerization proceeded by 1,2-vinyl
addition rather than ring opening in all cases explored.

5584 Smith et al.
Macromolecules, Vol. 38, No. 13, 2005
Figure 3. GPC traces (RI) of PMPDO-PMMA-I, -II, and -III
by ATRP.
along the PMMA segments37,38 and not photocleavage
of the bond between carbonyl groups14 in the ring-
opened form of PMPDO segments.
Figure 3 shows GPC curves for the PMPDO-PMMA
copolymers. Consistent with living radical polymeriza-
tions, the molecular weight distributions of the copoly-
mers are relatively narrow (PDI < 1.6; Table 1). We did,
however, observe a slight increase in polydispersity with
increasing MPDO feed concentration. Strangely, in-
creasing the MPDO in the monomer feed also consis-
tently decreased the overall yield of the polymers. In
fact, yields as low as 3% were recorded for the homo-
polymerization of PMPDO. Additionally, copolymer mo-
lecular weights exceeded their theoretical values; a good
indication that initiation was incomplete.
Figure 2. 1H and 13C HSQC NMR spectrum of PMPDO-PS-I
in CDCl ).
(
3
always resulted in the 1,2-vinyl addition product of
PMPDO as verified by 13C NMR (see Figure 1). In
contrast to polymers derived from CKAs, however,
conventional radical polymerization of MPDO led to
polymers with high molecular weights. We attribute the
ability to achieve high molecular weights in PMPDO to
the increased stability of the active carbon radical due
to the captodative effect. Homopolymerization of MPDO
by ATRP also resulted in high molecular weight poly-
mers; the “living” nature of ATRP yielded polymers with
lower polydispersity (PDI < 1.2), as compared to poly-
mers formed by conventional radical polymerization (see
Table 1).
Polymer compositions were obtained by integrating
the aromatic peaks of PMPDO and the methyl ester
1
peak of PMMA in the H NMR spectra (see Figure 4)
and are summarized in Table 1. The chloroform solvent
peak, which appears at 7.28 ppm, is excluded from the
integration. We found the copolymer compositions,
especially at higher MPDO feed concentrations, to be
significantly different from the feed compositions. In
fact, a monomer feed of 10 mol % MPDO resulted in a
copolymer with 32 mol % PMPDO. That MPDO is
preferentially incorporated into the copolymer was also
observed during the synthesis of PMPDO-PS. These
observations indicate that MPDO is much more likely
to add to a growing carbon radical compared to either
MMA or S. As discussed earlier, the presence of both an
electron-withdrawing and electron-donating substituent
on the cyclic radical of MPDO has a strongly stabilizing
effect. Consequently, the formation of a stabilized MPDO
cyclic radical not only favors conversion of MPDO over
MMA and S but also prevents its ring opening.39
Copolymerization of MPDO with MMA and Sty-
rene. We successfully copolymerized MPDO with both
MMA and S by ATRP. The conditions for the copolym-
erization of MPDO with either MMA or S in anisole,
along with the resulting polymer compositions and
molecular weights, are listed in Table 1. Copolymerizing
MPDO with either MMA or S did not alter the mecha-
nism by which MPDO polymerized. In particular,
13
results from C NMR analysis of the statistical copoly-
mers (representative spectra shown in Figure 1d,e) are
analogous to those of PMPDO homopolymers; the acetal
benzylic carbon (labeled d) from the MPDO monomer
is retained while the R-keto carbonyl carbon is absent.
Furthermore, we also carried out 2D NMR analysis on
PMPDO-PS-I (representative spectrum shown in Fig-
ure 2). We are able to cross correlate the proton peak
at 5.5-6.5 ppm with the acetal benzylic carbon signal
at ∼100 ppmsa further indication that the five-
membered ring in the MPDO monomer is retained on
copolymerization. This is, again, in contrast with what
had previously been reported for the copolymerization
To further confirm that MPDO copolymerization in
fact did proceed by 1,2-vinyl addition and not ring
opening, we also carried out some degradation experi-
ments on PMPDO-PS copolymers. Unlike the PMPDO-
PMMA copolymers examined by Chung and co-work-
14
ers, the PS segments in our copolymers are stable
upon exposure to UV and basic environments. Any
decrease in molecular weight during these degradation
studies must therefore be attributed to MPDOsonly the
ring-opened product contains R-ketoester groups in the
polymer backbone that are both photo- and hydrolyti-
cally cleavablesdegradation. Hydrolytic degradation of
PMPDO-PS-I copolymer was carried out under basic
conditions. After 50 h, only a slight decrease of the
molecular weight was observed (Figure 5), suggesting
1
4
of MPDO with MMA. In that particular report,
structural characterization of the statistical copolymer
was not presented. Rather, that MPDO ring opens
during copolymerization was supported by photodegra-
dation studies. With detailed NMR characterization at
hand, we speculate that the decrease in molecular
weight during the degradation studies observed by
14
Chung and co-workers was a result of random scission

Macromolecules, Vol. 38, No. 13, 2005
Polymerization of MPDO by ATRP 5585
Figure 6. DSC traces for PMMA, PMPDO-PMMA-I, and
PMPDO-PMMA-II.
tion temperature, Tg, at ≈104 °C (0.24 J/(g °C)). While
we have attempted on several occasions to measure the
Tg of pure PMPDO, no apparent glass transition was
detected <200 °C. The copolymers, however, exhibit
measurable Tgs that appear to increase with increas-
ing MPDO content. Specifically, PMPDO-PMMA-I
(
8% PMPDO by mass) copolymer reveals a single Tg at
≈
104 °C while PMPDO-PMMA-II (44% PMPDO by
mass) exhibits a Tg at ≈122 °C. The heat capacities
associated with these transitionss0.17 and 0.20 J/(g °C),
respectivelysare similar to that observed for the PMMA
homopolymer, suggesting that the measured glass
transitions are representative of the entire polymer
samples and not merely segments of the polymers.
1
Figure 4. H NMR spectra of and peak assignments for
PMPDO-PMMA-I, PMPDO-PMMA-II, and PMPDO-PMMA-
III. Integrations from which polymer compositions were ob-
tained are indicated. * indicates the chloroform solvent peak,
which was excluded from the integration.
Conclusions
13C NMR structural analysis has allowed us to
unambiguously determine the radical polymerization
mechanism of MPDO. Specifically, the polymerization
of MPDOswhether homo- or copolymerization and
regardless of polymerization conditions exploreds
proceeded by 1,2-vinyl addition rather than ring-opening
polymerization. During the copolymerization with MMA
or with S, MPDO incorporates significantly faster into
the copolymer. This observation suggests that MPDO
is a much more reactive monomer than either MMA or
S. The stability of PMPDO-PS during photo- and
hydrolytic degradation further confirms that MPDO was
incorporated into the copolymer through 1,2-vinyl ad-
dition and not ring opening. Thermal analysis carried
out on the copolymers revealed a single glass transition
temperature that increases with increasing PMPDO
content.
Figure 5. GPC traces (RI) of PMPDO-PS-I: (a) before
hydrolysis; (b) after hydrolysis for 50 h (polymer:THF:metha-
nol:KOH ) 0.1 g:4 mL:2.5 mL:0.13 g) and of PMPDO-PS-II;
(
c) before irradiation; (d) after irradiation for 25 h (polymer:
Acknowledgment. This research is supported
by the National Science Foundation (CAREER-DMR
THF ) 0.1 g:5 mL).
0
0
348339 and IMR-DMR 0314707 to Y.L.L. and CHE-
4-05627 to K.M.). Funding from the Texas Materials
the absence of any hydrolytically cleavable ester groups
in the polymer backbone. The small decrease of the
molecular weight was probably due to a decrease in the
hydrodynamic volume of the polymer chain stemming
from the hydrolysis of the ester group in the MPDO
ring. Figure 5 also shows that the molecular weight
of PMPDO-PS-II remains unchanged despite having
been exposed to UV irradiation for 25 h. That these
PMPDO copolymers are not susceptible to either photo-
or hydrolytic degradation is a further indication that
MPDO did not ring open during copolymerization.
Institute at the University of Texas at Austin, the
Camille and Henry Dreyfus Foundation, and the Keck
Foundation is also gratefully acknowledged.
4
0
References and Notes
(
1) Bailey, W. J.; Kuruganti, V. K.; Angle, J. S. ACS Symp. Ser.
990, 433, 149.
2) Wei, Y.; Connors, E. J.; Jia, X.; Wang, B. Chem. Mater. 1996,
, 604.
1
(
8
(3) Bailey, W. J.; Chen, P. Y.; Chen, S. C.; Chiao, W. B.; Endo,
T.; Gapud, B.; Kuruganti, V.; Lin, Y. N.; Ni, Z. Makromol.
Chem., Macromol. Symp. 1986, 6, 81.
Figure 6 contains DSC heating scans of PMMA,
PMPDO-PMMA-I, and PMPDO-PMMA-II. The PMMA
homopolymer, made by ATRP, exhibits a glass transi-
(
4) Pan, C.-Y.; Lou, X.-D. Macromol. Chem. Phys. 2000, 201,
1115.

5586 Smith et al.
Macromolecules, Vol. 38, No. 13, 2005
(
5) Antonucci, J. M.; Stansbury, J. W.; Reed, B. B. Polym. Prepr.
(24) Wei, Y.; Connors, E. J.; Jia, X.; Wang, B.; Deng, C. Polym.
Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1995, 36, 241.
(25) Wei, Y.; Connors, E. J.; Jia, X.; Wang, C. J. Polym. Sci., Part
A: Polym. Chem. 1998, 36, 761.
(
Am. Chem. Soc., Div. Polym. Chem.) 1992, 33, 507.
6) Sanda, F.; Endo, T. J. Polym. Sci., Part A: Polym. Chem.
(
2000, 39, 265.
(
(
(
7) Bailey, W. J.; Chou, J. L.; Feng, P. Z.; Kuruganti, V.; Zhou,
L. L. Acta Polym. 1988, 39, 335.
(26) Yuan, J.-Y.; Pan, C.-Y.; Tang, B. Z. Macromolecules 2001,
34, 211.
8) Bailey, W. J.; Wu, S. R.; Ni, Z. Makromol. Chem. 1982, 183,
(
(
(
27) Yuan, J.-Y.; Pan, C.-Y. Eur. Polym. J. 2002, 38, 2069.
28) Yuan, J.-Y.; Pan, C.-Y. Eur. Polym. J. 2002, 38, 1565.
29) Huang, J.; Pintauer, T.; Matyjaszewski, K. J. Polym. Sci.,
Part A: Polym. Chem. 2004, 42, 3285.
1913.
9) Bailey, W. J.; Ni, Z.; Wu, S. R. J. Polym. Sci., Polym. Chem.
Ed. 1982, 20, 3021.
(
(
(
(
(
(
10) Wu, Z.; Cao, L.; Pittman, C. U., Jr. J. Polym. Sci., Part A:
Polym. Chem. 1998, 36, 861.
(
(
30) Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101, 2921.
31) Wang, J.-S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117,
11) Cao, L.; Wu, Z.; Pittman, C. U., Jr. J. Polym. Sci., Part A:
Polym. Chem. 1999, 37, 2841.
5614.
(
(
32) Xia, J.; Matyjaszewski, K. Macromolecules 1997, 30, 7697.
33) Viehe, H. G.; Janousek, Z.; Mernyi, R.; Stella, L. Acc. Chem.
Res. 1985, 18, 148.
12) Sun, L. F.; Zhuo, R. X.; Liu, Z. L. J. Polym. Sci., Part A:
Polym. Chem. 2003, 41, 2898.
13) Bailey, W. J.; Chou, J. L.; Feng, P. Z.; Issari, B.; Kuruganti,
V.; Zhou, L. J. Macromol. Sci., Chem. 1988, A25, 781.
14) Chung, I. S.; Matyjaszewski, K. Macromolecules 2003, 36,
(
34) Hope, D. B.; W a¨ lti, M. J. Chem. Soc. C 1970, 18, 2475.
(35) Willker, W.; Leibfritz, D.; Kerssebaum, R.; Bermel, W. Magn.
Reson. Chem. 1993, 31, 287.
2995.
15) Bailey, W. J.; Feng, P. Polym. Prepr. (Am. Chem. Soc., Div.
Polym. Chem.) 1987, 28, 154.
(36) Miyagawa, T.; Sanda, F.; Endo, T. J. Polym. Sci., Part A:
Polym. Chem. 2000, 38, 1861.
(
(
(
(
(
(
(
16) Feng, P. Chin. J. Polym. Sci. 1992, 10, 350.
(37) MacCullum, J. R.; Schoff, C. K. Trans. Faraday Soc. 1971,
17) Feng, P. Chin. J. Polym. Sci. 1993, 11, 153.
67, 2372.
18) Hiraguri, Y.; Tokiwa, Y. Macromolecules 1997, 30, 3691.
19) Yuan, J.-Y.; Pan, C.-Y. Chin. J. Polym. Sci. 2002, 20, 9.
20) Bailey, W. J.; Ni, Z.; Wu, S. R. Macromolecules 1982, 15, 711.
21) Wickel, H.; Agarwal, S. Macromolecules 2003, 36, 6152.
22) Wickel, H.; Agarwal, S.; Greiner, A. Macromolecules 2003,
(38) MacCullum, J. R.; Schoff, C. K. Trans. Faraday Soc. 1971,
67, 2382.
(
39) Lenz, R. W. Organic Chemistry of Synthetic High Polymers;
John Wiley and Sons: New York, 1967.
40) Bailey, W. J.; Zhou, L. L. Macromolecules 1992, 25, 3.
(
36, 2397.
(23) He, T.; Zou, Y.-F.; Pan, C.-Y. Polym. J. 2002, 34, 138.
MA050393S