Systematic study on alkyl iodide initiators in living radical polymerization with organic catalysts

Article abstract of DOI:10.1021/ma501569j

Several low-molar-mass alkyl iodides were studied as initiating dormant species in living radical polymerization with organic catalysts. Primary, secondary, and tertiary alkyl iodides with different stabilizing groups (ester, phenyl, and cyano groups) were systematically studied for the rational design of initiating alkyl iodides. The activation rate constants of these alkyl iodides were experimentally determined for quantitative comparison. These alkyl iodides were used in the polymerizations of methyl methacrylate and butyl acrylate to examine their initiation ability in these polymerizations. A telechelic polymer was prepared using an alkyl iodide with a functional group. Alkyl iodides with multi-initiating sites were also studied.

Full text of DOI:10.1021/ma501569j

Article
pubs.acs.org/Macromolecules
Systematic Study on Alkyl Iodide Initiators in Living Radical
Polymerization with Organic Catalysts
†
†
,†
,†
‡
‡
Lin Lei, Miho Tanishima, Atsushi Goto,* Hironori Kaji,* Yu Yamaguchi, Hiroto Komatsu,
‡
‡
Takuya Jitsukawa, and Michihiko Miyamoto
†
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
‡
Techno Research Center, Godo Shigen Sangyo Co., LTD., 1365 Nanaido, Chosei-Mura, Chosei-Gun, Chiba 299-4333, Japan
S Supporting Information
*
ABSTRACT: Several low-molar-mass alkyl iodides were studied as initiating dormant species in living radical polymerization
with organic catalysts. Primary, secondary, and tertiary alkyl iodides with different stabilizing groups (ester, phenyl, and cyano
groups) were systematically studied for the rational design of initiating alkyl iodides. The activation rate constants of these alkyl
iodides were experimentally determined for quantitative comparison. These alkyl iodides were used in the polymerizations of
methyl methacrylate and butyl acrylate to examine their initiation ability in these polymerizations. A telechelic polymer was
prepared using an alkyl iodide with a functional group. Alkyl iodides with multi-initiating sites were also studied.
INTRODUCTION
mechanistically different systems referred to as reversible
■
5
,6
chain transfer catalyzed polymerization (RTCP)
reversible coordination mediated polymerization (RCMP).
and
Living radical polymerization (LRP) has gained increased
attention as a useful technique for preparing well-defined
polymers with narrow molecular weight distributions.
is based on the reversible activation of a dormant species
Polymer-X) to a propagating radical (Polymer ) (Scheme 1a).
A sufficiently large number of activation−deactivation cycles are
required for achieving low polydispersity. We recently
6
−11
1
−3
In this work, we focus on RCMP. The catalysts for RCMP
include organic salts such as tetrabutylammonium iodide (BNI)9
and methyltributylphosphonium iodide (BMPI) (Figure 1).
RCMP utilizes a reversible coordination of Polymer-I with a
LRP
•
(
•
•
4
catalyst (activator) to generate Polymer and an I−catalyst
•
complex (deactivator) (Scheme 1b). (The I−catalyst complex
is not a stable radical and reacts with another I-catalyst
developed new LRP systems using iodine as a capping agent
and organic molecules as catalysts. We developed two
•
complex to generate an I -catalyst complex and a catalyst
2
•
(
Scheme 1b). Both of the I−catalyst and I −catalyst
2
Scheme 1. Reversible Activation: (a) General Scheme and
b) RCMP
7,9
•
complexes work as deactivators of Polymer . ) Attractive
features of RCMP include no use of special capping agents or
metals. The catalysts are inexpensive, relatively nontoxic, easy
to handle, and amenable to a wide range of monomers
including styrenes, methacrylates, acrylates, acrylonitrile, and
(
7
−9
those with various functional groups.
RCMP can serve as a
facile methodology for various applications.
To achieve low polydispersity, a sufficiently fast initiation of
initiating dormant species (low-molar-mass alkyl iodides) is
required as well as a sufficiently high frequency of activation−
deactivation cycles in the polymer region (during the
Received: July 31, 2014
Revised: September 7, 2014
Published: September 16, 2014
©
2014 American Chemical Society
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Figure 1. Structures and abbreviations of alkyl iodides and catalysts studied in this work. The k value with BMPI at 70 °C is given for several alkyl
a
iodides. The arrows indicate the ranges of effective alkyl iodides in the polymerizations of MMA and BA.
polymerization). Thus, rational design of initiating alkyl iodides
is of primary importance. If the carbon−iodine bond of the
alkyl iodide is too strong, the radical is not effectively generated
from the alkyl iodide, resulting in low initiation efficiency. Thus,
the radical must be effectively generated. Another requisite is
that the generated radical must undergo sufficiently fast
addition to monomer to drive the initiation process.
Information). Figure 2 shows the Arrhenius plots, from which
ka is given as eqs 1 and 2.
In this work, we systematically studied several low-molar-
mass alkyl iodides shown in Figure 1. The abbreviations of the
alkyl iodides are given in Figure 1. Primary, secondary, and
tertiary alkyl iodides with different stabilizing groups (ester,
phenyl, and cyano groups) were studied for the rational design
of initiating alkyl iodides with high initiation efficiency. We
experimentally determined the activation rate constant ka
(
Scheme 1b) for several alkyl iodides for quantitative
Figure 2. Arrhenius plot for k of PMMA-I with BMPI and BNI in
bulk MMA.
a
comparison. We then used these alkyl iodides in methyl
methacrylate (MMA) and butyl acrylate (BA) polymerizations
to probe their initiation ability, using BMPI and BNI as
catalysts. We prepared a telechelic polymer (chain-end-
functionalized polymer) by employing an alkyl iodide with a
functional group. Alkyl iodides with multi-initiating sites, i.e.,
alkyl di-iodides and alkyl tri-iodides, were also studied.
−
1
−1
11
−1
ka/M
s
= 8.3 × 10 exp(−86.8 kJ mol /RT) for BNI
(1)
−1 −1
13
−1
ka/M
s
= 3.0 × 10 exp(−97.6 kJ mol /RT) for BMPI (2)
The k value extrapolated at 70 °C from the Arrhenius plot was
a
RESULTS AND DISCUSSION
−1 −1
−1 −1
■
0.050 M
s
for BNI and 0.041 M
s
for BMPI in bulk
Determination of k for Polymer−Iodide. Prior to low-
MMA medium.
We also determined k for BMPI at 70 °C in a solution
a
molar-mass alkyl iodides, we studied a polymer−iodide, i.e.,
poly(methyl methacrylate)−iodide (PMMA-I), which is the
dormant species in the polymer region in the polymerization of
a
medium of MMA (90%) and acetonitrile (10%). Acetonitrile
was used to ensure that BMPI (organic salt catalyst) was
completely dissolved at the mild temperature of 70 °C. (BMPI
MMA. We determined the k values of PMMA-I using BMPI
and BNI as catalysts. The medium (solvent) is MMA
monomer. We previously determined the k values at 90 °C.
In this work, we extended the study to other temperatures to
establish the temperature dependence. The method for
determining k was a previously reported gel permeation
chromatography (GPC) peak resolution method (Supporting
a
was not completely dissolved in bulk MMA medium below 80
9
−1 −1
°C.) The k value in MMA/acetonitrile was 0.0070 M s ,
a
a
−1
which is approximately 1/6 times smaller than that (0.041 M
−1
s ) in bulk MMA (estimated by extrapolation). This result
shows a solvent effect. The value for BMPI at 70 °C in MMA/
acetonitrile will be referred to in the subsequent section.
a
12
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Determination of ka for Low-Molar-Mass Alkyl
PMMA-I, would not significantly affect k because the side
a
Iodides. We determined the k values of several low-molar-
chain is far from the carbon−iodine bond. (In a copper-
a
7,13
mass alkyl iodides by a radical trap experiment,
using BMPI
catalyzed ATRP, the k values for unimer model alkyl bromides
a
as a catalyst at 70 °C. In each radical trap trial, we heated an
alkyl iodide (5 mM), BMPI (20 mM), and the radical trap
,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) (20 mM) in a
with methyl and ethyl side chains (MMA-Br and EMA-Br)
1
4
−1 −1
were very similar. ) The k value of EMA-I (0.0023 M s ) is
a
−1
−1
2
smaller than that of PMMA-I (0.0070 M s ). This result
mixture of toluene-d (90%) and acetonitrile-d (10%). We
8
3
clearly shows a polymer effect (chain length dependence
assume that k would not significantly differ in toluene and
a
(CLD)) in k . The CLD should be the strongest between the
a
MMA (used for the polymer iodide) used as a hydrophobic
unimer and dimer and become less significant with increasing
chain length.
For alkyl iodides possessing an ester stabilizing group, ka
medium. If the alkyl iodide (R−I) reacts with BMPI, the
•
generated radical R is trapped by TEMPO, thereby yielding R-
1
TEMPO. Figure 3 shows the H NMR spectra at time zero and
increased in the order of a primary alkyl iodide E-I (<0.0001
−
1
−1
−1 −1
M
s ) < a secondary one EA-I (0.0004 M s ) < a tertiary
−1
−1
one EMA-I (0.0023 M s ), as expected. For different
stabilizing groups, a cyano group led to a larger k than an ester
a
−1
−1
group, based on comparing CE-I (0.0040 M s ) and EA-I
−
1 −1
(
M
0.0004 M s ) for secondary alkyl iodides and CP-I (0.0058
−1
−1
−1 −1
s ) and EMA-I (0.0023 M s ) for tertiary ones. These
results suggest that the cyano group is a more effective
stabilizing group than the ester group for this radical reaction.
Alkyl iodides with two stabilizing groups (ester, cyano, and
phenyl groups) showed very large k values. In the case of
a
PhCN-I, it was difficult to accurately determine k because the
a
R-TEMPO species produced was not stable enough (easily
dissociated) at 70 °C due to the weak carbon−TEMPO bond.
This difficulty, in turn, indicates that PhCN-I has a very large ka
value, and the value for PhCN-I in Figure 1 is a rough
1
Figure 3. H NMR spectra (in the range of 0.75−2.25 ppm) of the
estimation (0.25 M− s ).
1
−1
solution of CP-I (5 mM), BMPI (20 mM), and TEMPO (20 mM)
heated at 70 °C for 0 and 3 h. The solvent was a mixture of toluene-d8
90%) and acetonitrile-d (10%).
The k value increased in the order of EA-I (1) < EMA-I (6)
a
(
3
< CE-I (10) < PhE-I (33) in this RCMP. This order is the same
as in an ATRP with the corresponding alkyl bromides, i.e., MA-
at 3 h for CP-I. At 3 h, new signals appeared and matched the
signals of independently prepared pure R-TEMPO. We
obtained k by following the decay of the concentration of R-
I with NMR. In some cases, NMR signals were difficult to
distinguish, and HPLC (high performance liquid chromatog-
raphy) was used to follow the decay of the R-I concentration.
5
Br (1) < MMA-Br (56) < CE-Br (340) < PhM-Br (2.8 × 10 ),
where the side chain is a methyl group for MA-Br, MMA-Br,
and PhM-Br, and the catalyst was CuBr/(2-pyridylmethyl)-
a
15
amine used in acetonitrile at 22 °C. The numbers in the
parentheses are the relative k values in each RCMP and ATRP
a
system (compared with EA-I for RCMP and MA-Br for
5
Figure 1 summarizes the k values obtained at 70 °C. EMA-I
is a unimer model of a polymeric PMMA-I. The different side
ATRP). Notably, whereas k is as much as 2.8 × 10 times
a
a
different between PhM-Br and MA-Br in ATRP, k is only 33
a
chains, i.e., ethyl group for EMA-I and methyl group for
times different between PhE-I and EA-I in RCMP. The weaker
Figure 4. Plots of (a) ln([M] /[M]) vs t and (b) M and M /M vs conversion for the MMA/R-I/BMPI systems (in 25% toluene): [MMA] = 8 M;
0
n
w
n
0
[
R-I] = 80 mM; [BMPI] = 80 mM. The symbols, R-I, and temperatures are indicated in the figure. I (2 mM) was added for EMA-I at 80 °C.
0
0
2
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Figure 5. Plots of (a) ln([M] /[M]) vs t and (b) M and M /M vs conversion for the MMA/R-I/BMPI systems (in 25% toluene) (70 °C):
0
n
w
n
[
MMA] = 8 M; [R-I] = 80 mM; [BMPI] = 80 mM. The symbols and R-I are indicated in the figure.
0 0 0
Figure 6. Plots of (a) ln([M] /[M]) vs t and (b) M and M /M vs conversion for the BA/R-I/BNI systems (in bulk) (110 °C): [BA] = 8 M; [R-
0
n
w
n
0
I] = 80 mM; [BNI] = 320 mM. The symbols and R-I are indicated in the figure. I (0.2 mM) was added for filled squares.
0
0
2
dependence of k on the alkyl groups in RCMP (alkyl iodides)
would be an interesting feature.
unimer model is not yet an efficient initiator in this particular
condition (70 °C).
a
MMA Polymerizations. We then examined the polymer-
ization performance with these alkyl iodides in actual
polymerizations. The studied system is a solution polymer-
ization of MMA (8 M (100 equiv)) with an alkyl iodide (80
mM (1 equiv)) and BMPI (80 mM) in toluene (75% MMA
and 25% toluene) at 70 °C.
However, we would note that at a slightly higher temperature
of 80 °C the unimer model EMA-I became an efficient initiator
filled squares). The k of EMA-I would be sufficiently large at
a
(
8
0 °C. In this case, we added a small amount (2 mM) of
9
molecular iodine I2 as a deactivator to avoid too many
•
monomers to add to the generated EMA at an early stage of
polymerization. The M agreed well with M
from a middle
n
n,theo
Figure 4 shows the results for alkyl iodides possessing an
ester group. PMMA-I (filled circles) showed well-controlled
polymerization. The number-average molecular weight (Mn)
agreed with the theoretical value (Mn,theo), and the polydisper-
sity index (PDI = M /M ) was small, i.e., approximately 1.2,
stage of polymerization (at a conversion >60%), and PDI was
small, e.g., approximately 1.2. Thus, we may use the unimer
model EMA-I for possible applications at slightly high
temperatures.
w
n
We then studied 70 °C without I again. The secondary alkyl
2
from an early stage of polymerization, where M is the weight-
w
iodide EA-I (open triangles) showed much slower polymer-
average molecular weight. In comparison with the polymeric
PMMA-I, the unimer model EMA-I (open squares) showed a
slightly lower polymerization rate. The Mn deviated from
Mn,theo, and PDI was relatively large, i.e., approximately 1.5,
throughout the polymerization. This result indicates that the
ization and poorer control of M and PDI than the tertiary one
n
EMA-I (open squares) because activation (initiation) is too
slow for EA-I. No polymerization took place with the primary
alkyl iodide E-I (open circle). All these observations (Figure 4)
are consistent with the k values discussed above.
a
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1
Figure 7. H NMR spectrum (acetonitrile-d ) of PMMA-I obtained from PhEOH-I: [MMA] = 8 M; [PhEOH-I] = 160 mM; [BMPI] = 80 mM in
3
0
0
0
25% toluene for 4 h at 60% conversion (70 °C).
Figure 5 shows the results for alkyl iodides possessing a
cyano group, i.e., CP-I (filled circles) and CE-I (filled squares).
poly(methacrylate)−iodine, as suggested in the above dis-
cussion. We studied the bulk polymerization of BA (8 M) with
R-I (80 mM) and BNI (320 mM) at 110 °C. Figure 6 shows
the results. In contrast to the MMA polymerization at 70 °C,
this BA polymerization at the elevated temperature proceeded
even with the primary alkyl iodide E-I (open circles), although
its initiation efficiency was low. The secondary alkyl iodide EA-I
(open squares) afforded relatively low PDI (= 1.4−1.5). EA-I
(filled squares) afforded almost quantitative initiation and low
PDI (= 1.3) with the addition of a small amount (0.2 mM) of I2
(deactivator). This result shows that EA-I can be used as a good
CP-I has a similar k value to that of PMMA-I (see above) and
a
should work as an efficient initiator. In fact, the polymerization
rate with CP-I was almost the same as that with the polymeric
PMMA-I (Figure 4 (filled circles)). The M agreed well with
n
Mn,theo, and PDI was approximately 1.2 throughout the
polymerization. While CP-I showed better polymerization
performance than CE-I, CE-I also exhibited sufficiently good
control in M and PDI. These results clearly demonstrate the
n
usefulness of both CE-I and CP-I as initiating alkyl iodides.
Figure 5 also compares the results for alkyl iodides with two
stabilizing groups, i.e., PhE-I (filled triangles), EEMA-I (filled
pentagons), and PhCN-I (open circles). They have very large ka
values (see above). PhE-I (with a phenyl group and an ester
group) and EEMA-I (with two ester groups and a methyl
group) led to controlled polymerizations similarly to CP-I with
a cyano group, as expected. However, PhCN-I (with a phenyl
group and a cyano group) afforded a slower polymerization and
initiator. Without the addition of I , the tertiary alkyl iodide
2
EMA-I (filled circles) exhibited quantitative initiation and
yielded low-polydispersity polymers (PDI = 1.3). CP-I with a
cyano group (filled triangles) also worked well and achieved
even lower polydispersity (PDI = 1.2). PhE-I (open triangles)
and EEMA-I (open pentagons) with two stabilizing groups,
which were highly efficient in the MMA polymerization at 70
°C, led to slower polymerization. This would be because the
•
•
a large deviation of M from Mn,theo. This result would be
addition of the released radicals (PhE and EEMA ) to the less
conjugated monomer BA is relatively slow and also because
these labile alkyl iodides undergo decomposition (degradation)
as a side reaction at the elevated temperature. (The generated
byproducts may slow down the polymerization as retarders.)
Thus, the range of effective initiating alkyl iodides depended on
monomers and temperatures, as depicted in Figure 1.
n
obtained because activation is very fast, but the released radical
•
•
PhCN is too stable to add to monomer. PhCN would
undergo radical−radical termination rather than addition to
monomer, and the termination would significantly reduce the
concentration of the dormant species and hence lead to the
observed slow polymerization and large deviation of M . Thus,
n
efficient alkyl iodides should have sufficiently large k values,
Telechelic Polymers. Telechelic polymers have many
useful applications. We prepared a telechelic polymer using a
a
and at the same time, the released alkyl radicals should be
reactive enough to add to monomer. The range of effective
initiating alkyl iodides for this MMA system is depicted in
Figure 1. Examples of the GPC chromatograms are given in the
Supporting Information.
BA Polymerizations. We switched the monomer from
MMA to BA, elevated the temperature from 70 to 110 °C, and
functional alkyl iodide, i.e., PhEOH-I with a hydroxyl group.
1
Figure 7 shows the H NMR spectrum of the polymer (M =
n
3100 and PDI = 1.14) synthesized in the polymerization of
MMA (8 M) with PhEOH-I (160 mM) and BMPI (80 mM) at
70 °C for 4 h (conversion = 60%) and purified with a
preparative GPC. The introduction of the hydroxyl group was
clearly confirmed by the signals of CH CH OH (3.9−4.2
changed the catalyst from BMPI to BNI. A higher temperature
2
2
9
(
110 °C) is required for the BA polymerization because the
ppm). We estimated chain-end functionality from the relative
peak areas of this moiety and the monomer units. The number
carbon−iodine bond is stronger for poly(acrylate)−iodine than
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Figure 8. Plots of (a) ln([M] /[M]) vs t and (b) M and M /M vs conversion for the MMA/R-I/BMPI systems (in 25% toluene) (70 °C) and the
0
n
w
n
BA/R-I/BNI system (in bulk) (110 °C): [monomer] = 8 M; [R-I] = 80 mM; [catalyst] = 80 mM for BMPI and 320 mM for BNI. The symbols,
0
0
0
monomers, and R-I are indicated in the figure.
of monomer units (= 28) was calculated using the Mn
determined by GPC. The estimated chain-end functionality
was 105% (with ±5% experimental error). Thus, we
successfully obtained a well-defined telechelic polymer with
virtually quantitative chain-end functionality.
using an alkyl iodide with a hydroxyl functional group. The
studied alkyl di-iodides and alkyl tri-iodide were effective
initiators and would be useful for the design of polymer
architectures.
Multi-Initiating Alkyl Iodides. We previously successfully
prepared A-B-A triblock copolymers and 3-arm star polymers
by employing alkyl di-iodide EMA-II and alkyl tri-iodide EMA-
EXPERIMENTAL SECTION
■
Materials. MMA (99%, Nacalai Tesque, Japan) and BA (99%,
Nacalai) were purified through an alumina column. CP-I (99%, Tokyo
Chemical Industry (TCI), Japan (contract service)), BNI (98%, TCI),
BMPI (96%, Wako Pure Chemical, Japan), TEMPO (99%, Aldrich),
acetonitrile (99.5%, Wako), and toluene (99.5%, Nacalai) were used as
received.
Ethyl 2-Iodoisobutyrate (EMA-I). The corresponding bromide,
i.e., ethyl 2-bromoisobutyrate (EMA-Br) (39.0 g, 200 mmol), and NaI
149.9 g, 1000 mmol) were stirred in dry acetonitrile (300 mL) at 80
1
0
III, respectively. EMA-II and EMA-III are methacrylate types
tertiary alkyl iodides with an ester group). Here, we compare
EMA-I, EMA-II, and EMA-III in the MMA polymerization at
(
7
0 °C. As Figures 4 and 8 show, both EMA-II (Figure 8 (filled
circles)) and EMA-III (Figure 8 (filled squares)) effectively
initiated, whereas the corresponding monoiodide EMA-I
(
Figure 4 (open squares)) did not initiate very effectively, as
(
mentioned. (The molecular weights of the star polymers from
EMA-III were determined by GPC-MALLS (multiangle laser
light scattering).) The effective initiation of EMA-II and EMA-
III would be due to their larger steric hindrance compared with
that of EMA-I. (The steric hindrance can weaken the carbon−
iodine bond.) PhE-II with two stabilizing groups (phenyl and
ester groups) (Figure 8 (filled triangles)) also achieved low
polydispersity in the same polymerization condition.
In the BA polymerization at 110 °C, we studied an alkyl di-
iodide EA-II of the acrylate type (secondary alkyl iodide with an
ester group). As Figures 6 and 8 show, EA-II (Figure 8 (open
circles)) initiated effectively, whereas the monoiodide EA-I
°C for 20 h. The reaction mixture was filtered to remove insoluble
salts. The filtrate was concentrated under reduced pressure, and the
residue was dissolved in dichloromethane, washed with saturated
aqueous NaHSO solution and water, and dried over MgSO . After
3
4
removal of solvent under reduced pressure, the purification by
1
distillation afforded EMA-I (57% yield). H NMR (CDCl ): δ = 1.28
3
(
t, 3H, OCH CH J = 7.2 Hz), 2.06 (s, 6H, CI(CH ) ), 4.21 (q, 2H,
2 3, 3 2
13
OCH CH J = 7.1 Hz). C NMR (CDCl ): δ = 13.7 (OCH CH ),
2
3,
3
2
3
3
3.7 (CI(CH ) ), 33.8 (CI(CH ) ), 61.9 (OCH CH ), 173.3
3 2 3 2 2 3
(OC(O)CI).
Ethyl 2-Iodopropionate (EA-I). The corresponding bromide, i.e.,
ethyl 2-bromopropionate (EA-Br) (35.0 g, 193 mmol), and NaI (58.0
g, 387 mmol) were stirred in dry acetone (193 mL) at 25 °C for 2 h.
The reaction mixture was filtered to remove insoluble salts. The filtrate
was concentrated under reduced pressure, and the residue was
dissolved in dichloromethane, washed with saturated aqueous Na SO
(
Figure 6 (open squares)) did not initiated so effectively. This
result again suggests the importance of the steric hindrance.
These results for MMA and BA also demonstrate the
effectiveness of the studied alkyl di-iodides and tri-iodide for
the design of polymer architectures.
2
3
solution and water, and dried over Na SO . Removal of solvent under
2
4
1
reduced pressure afforded EA-I (79% yield). H NMR (CDCl
.26 (t, 3H, OCH CH , J = 7.0 Hz), 1.93 (d, 3H, CHICH , J = 7.0
): δ =
3
1
2
3
3
Hz), 4.14−4.22 (m, 1H, CHICH , J = 7.0 Hz), 4.45 (q, 2H,
CONCLUSIONS
3
■
13
OCH CH , J = 7.0 Hz). C NMR (CDCl ): δ = 13.2 (CHICH ), 13.7
2
3
3
3
The k value increased in the order of primary < secondary <
a
(
OCH CH ), 23.3 (CHICH ), 61.8 (OCH CH ), 171.9 (OC(O)CI).
2 3 3 2 3
tertiary alkyl iodides. The cyano group was a better stabilizing
group than the ester group. Alkyl iodides with two stabilizing
groups had very large k values. Figure 1 summarizes the k
values with BMPI catalyst at 70 °C and also the ranges of
effective alkyl iodides in the polymerizations of MMA (70 and
Ethyl 2-Iodoacetate (E-I). E-I was obtained from the same
procedure as EA-I. Ethyl 2-bromoacetate (E-Br) was used instead of
1
a
a
EA-Br to afford E-I (83% yield). H NMR (CDCl ): δ = 1.25 (t, 3H,
3
OCH CH , J = 7.2 Hz), 3.65 (s, 2H, ICH CO), 4.17 (q, 2H,
2
3
2
13
OCH CH , J = 7.1 Hz). C NMR (CDCl ): δ = −5.3 (C(O)CH I),
2
3
3
2
8
0 °C) and BA (110 °C). A telechelic polymer was prepared
13.8 (OCH CH ), 62.1 (OCH CH ), 168.7 (C(O)CI).
2 3 2 3
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2
-Iodopropionitrile (CE-I). CE-I was obtained from the same
(PhCHI), 60.5 (CH OH), 67.5 (OCH CH ), 128.7 (Ph), 128.8 (Ph),
128.9 (Ph), 136.8 (Ph), 170.0 (OC(O)CI).
2
2
2
procedure as EA-I. 2-Bromopropionitrile (CE-Br) was used instead of
EA-Br to afford CE-I (82% yield). H NMR (CDCl ): δ = 2.12 (d, 3H,
CHICH , J = 7.0 Hz) 4.26 (q, 1H, CNCHICH , J = 7.2 Hz).
NMR (CDCl ): δ = −13.2 (CICH ), 25.5 (CICH ), 120.0 (CICN).
Ethyl 2-Iodo-2-phenylacetate (PhE-I). PhE-I was obtained from
the same procedure as EA-I. Ethyl 2-bromo-2-phenylacetate (PhE-Br)
was used instead of EA-Br to afford PhE-I (82% yield). H NMR
1
Ethylene Glycol Bis(2-iodoisobutyrate) (EMA-II). The mixture
of ethylene glycol (5.0 g, 80 mmol) and pyridine (13.9 g, 176 mmol)
in dichloromethane (25 mL) was slowly added to the solution of 2-
bromoisobutyryl bromide (44.1 g, 192 mmol) in dichloromethane (15
mL) and stirred for 1 h. The reaction mixture was washed with
aqueous HBr (5%), saturated aqueous Na SO solution, and water and
3
13
C
3
3
3
3
3
1
2
3
(
CDCl ): δ = 1.27 (t, 3H, OCH CH , J = 7.2 Hz), 4.15−4.27 (m, 2H,
dried over MgSO . Removal of the solvent under reduced pressure
3
2
3
4
OCH CH ), 5.51 (s, 1H, PhCHICO), 7.27−7.33 (m, 3H, PhH),
afforded ethylene glycol bis(2-bromoisobutyrate) (EMA-BB), which
2
3
1
3
1
7
2
1
.58−7.60 (m, 2H, PhH). C NMR (CDCl ): δ = 13.8 (OCH CH ),
0.7 (PhCHI), 62.3 (OCH CH ), 128.7 (Ph), 128.7 (Ph), 128.9 (Ph),
was used in the subsequent reaction without further purification. H
3
2
3
NMR (CDCl ): δ = 1.92 (s, 12H, CCH ), 4.42 (s, 4H, OCH CH O).
2
3
3
3
2
2
37.3 (Ph), 169.8 (OC(O)CI).
Diethyl 2-Iodo-2-methylmalonate (EEMA-I). The correspond-
EMA-BB (25.5 g, 71 mmol) and NaI (50.9 g, 340 mmol) were stirred
in dry acetonitrile (110 mL) at 80 °C for 8 h. The reaction mixture
was filtered to remove insoluble salts. The filtrate was concentrated
under reduced pressure, and the residue was dissolved in dichloro-
methane, washed with saturated aqueous Na SO solution and water,
ing bromide, i.e., diethyl 2-bromo-2-methylmalonate (EEMA-Br) (17.7
g, 70 mmol), and NaI (12.6 g, 84 mmol) were stirred in dry
acetonitrile (44 mL) at 25 °C for 1 h. The reaction mixture was
concentrated under reduced pressure. The residue was dissolved in
diethyl ether and filtered to remove insoluble salts. Removal of solvent
under reduced pressure afforded EEMA-I (88% yield). 1H NMR
2
3
and dried over MgSO . After removal of solvent under reduced
4
pressure, the purification by flash chromatography (silica gel; ethyl
1
acetate/hexane) afforded EMA-II (35% yield). H NMR (CDCl ): δ =
3
13
(
CDCl ): δ = 1.21 (t, 6H, OCH CH , J = 7.2 Hz), 2.18 (s, 3H,
2.08 (s, 12H, CCH ), 4.39 (s, 4H, OCH CH O). C NMR (CDCl ):
3
2
3
3 2 2 3
13
CICH ), 4.18 (q, 4H, OCH CH , J = 7.1 Hz). C NMR (CDCl ): δ =
δ = 32.8 (CI(CH ) ), 33.6 (CI(CH ) ), 63.1 (OCH CH O), 173.1
3 2 3 2 2 2
3
2
3
3
1
1
3.6 (OCH CH ), 29.4 (CH CI), 35.1 (C(CH )I), 62.9 (OCH CH ),
68.7 (OC(O)CI).
α-Iodobenzyl Cyanide (PhCN-I). Bromine (52.3 g, 308 mmol)
(OC(O)CI).
2
3
3
3
2
3
Glycerol Tris(2-Iodoisobutyrate) (EMA-III). EMA-III was
obtained from the same process as EMA-II. Glycerol was used instead
of ethylene glycol to afford pure EMA-III in a 35% yield. H NMR
1
was dropwisely added into benzyl cyanide (32.8 g, 280 mmol) over 1 h
at 110 °C. After stirring for another 0.5 h, the reaction mixture was
cooled to room temperature and diluted with dichloromethane. The
(CDCl ): δ = 2.08 (m, 18H, CCH ), 4.33 (dd, 2H, OCHHCHCH-
3
3
HO), 4.48 (dd, 2H, OCHHCHCHHO), and 5.37 (m, 1H,
OCHHCHCHHO). 13C NMR (CDCl ): δ = 32.3 (CI(CH ) ), 32.5
solution was washed with saturated aqueous NaHSO solution and
3
3
3 2
water and dried over MgSO . Removal of the solvent under reduced
(CI(CH ) ), 33.6 (CI(CH ) ), 33.6 (CI(CH ) ), 62.9
4
3 2 3 2 3 2
pressure afforded α-bromobenzyl cyanide (PhCN-Br) (97% yield),
(OCH CHCH O), 70.3 (OCH CHCH O), 172.4 (OC(O)CI),
2 2 2 2
which was used in the subsequent reaction without further purification.
172.8 (OC(O)CI).
1
H NMR (CDCl ): δ = 5.48 (s, 1H, PhCHICN), 7.40−7.44 (m, 3H,
Ethylene Glycol Bis(2-iodo-2-phenylacetate) (PhE-II). 2-
Bromo-2-phenylacetic acid (25.0 g, 115 mmol) and thionyl chloride
(27.6 g, 232 mmol) were stirred at 80 °C for 1.5 h. After removal of
thionyl chloride under reduced pressure, the residue was dissolved in
dichloromethane and dropwisely added into the mixture of ethylene
glycol (3.4 g, 55 mmol) and pyridine (8.7 g, 110 mmol) in
dichloromethane at 0 °C. The reaction mixture was stirred at 0 °C
for another 1 h, washed with aqueous HBr (5%), saturated aqueous
3
PhH), 7.53−7.56 (m, 2H, PhH). PhCN−Br (32.0 g, 160 mmol) and
NaI (28.8 g, 192 mmol) were stirred in dry acetonitrile (100 mL) at 25
°C for 1 h. The reaction mixture was concentrated under reduced
pressure, and the residue was dissolved in dichloromethane. After
filtration to remove insoluble substances, the filtrate was washed with
saturated aqueous Na SO solution and water and dried over MgSO .
2
3
4
After removal of solvent under reduced pressure, the purification by
1
recrystallization from acetonitrile afforded PhCN-I (57% yield). H
Na SO solution, and water, and dried over MgSO . Removal of
2
3
4
NMR (CDCl ): δ = 5.60 (s, 1H, PhCHICN), 7.32−7.39 (m, 3H,
solvent under reduced pressure afforded ethylene glycol bis(2-bromo-
3
13
PhH), 7.51−7.54 (m, 2H, PhH). C NMR (CDCl ): δ = −4.9
2-phenylacetate) (PhE-BB) (23.9 g, 95% yield), which was used in the
3
1
(
(
CHIPh), 118.2 (CHICN), 127.2 (Ph), 129.4 (Ph), 129.7 (Ph), 135.2
Ph).
subsequent reaction without further purification. H NMR (CDCl
3
): δ
= 4.31−4.38 (m, 4H, OCH CH O), 5.25−5.29 (m 2H, PhCH.),
2 2
2
-Hydroxyethyl 2-Iodo-2-phenylacetate (PhEOH-I). 2-Bromo-
7.24−7.36 (m, 6H, PhH), 7.42−7.50 (m, 4H, PhH). PhE-BB (15.1 g,
33 mmol) and NaI (14.8 g, 99 mmol) were stirred in dry acetone (33
mL) at 17 °C for 3.5 h. The reaction mixture was filtered to remove
insoluble salts. The filtrate was concentrated under reduced pressure,
and the residue was dissolved in dichloromethane, washed with
saturated aqueous Na SO solution and water, and dried over MgSO .
2
2
-phenylacetic acid (25.0 g, 115 mmol) and thionyl chloride (27.3 g,
29 mmol) were stirred at 80 °C for 1 h. After removal of thionyl
chloride under reduced pressure, the residue was dropwisely added
into the mixture of ethylene glycol (284.7 g, 4.6 mol) and pyridine (9.5
g, 120 mmol) over 0.5 h at 25 °C. The reaction mixture was stirred for
another 1 h, diluted with dichloromethane, washed with saturated
aqueous NaHSO solution and water, and dried over MgSO . Removal
2
3
4
Removal of solvent under reduced pressure afforded EMA-II (88%
1
yield). H NMR (CDCl ): δ = 4.33 (s, 4H, OCH CH O), 5.47 (s, 2H,
3
4
3
2
2
1
3
of solvent under reduced pressure afforded 2-hydroxyethyl 2-bromo-2-
PhCHICO), 7.22−7.26 (m, 6H, PhH), 7.51−7.53 (m, 4H, PhH). C
NMR (CDCl ): δ = 19.6 (PhCHI), 19.7 (PhCHI), 63.2
phenylacetate (PhEOH-Br) (80% yield), which was used in the
3
1
subsequent reaction without further purification. H NMR (CDCl ): δ
(OCH CH O), 128.8 (Ph), 128.9 (Ph), 129.0 (Ph), 136.8 (Ph),
3
2
2
=
1.73 (br s, 1H, OCH CH OH), 3.78−3.87 (m, 2H, OCH CH OH),
169.6 (OC(O)CI).
Diethyl 2,5-Diiodoadipate (EA-II). EA-II was obtained from the
same procedure as EA-I. Diethyl 2,5-dibromoadipate (EA-BB) was
used instead of EA-Br to afford EA-II (73% yield). H NMR (CDCl ):
2
2
2
2
4.25−4.35 (m, 2H, OCH CH OH), 5.39 (s, 1H, PhCHBrCO), 7.31−
7.38 (m, 3H, PhH), 7.52−7.56 (m, 2H, PhH). PhEOH-Br (5.0 g, 19.3
2
2
1
mmol) and NaI (5.8 g, 38.6 mmol) were stirred in dry acetone (20
mL) at 0 °C for 1 h. The reaction mixture was filtered to remove
insoluble salts. The filtrate was concentrated under reduced pressure,
and the residue was dissolved in dichloromethane, washed with
saturated aqueous Na SO solution and water, and dried over MgSO .
3
δ = 1.27 (t, 3H, OCH CH J = 7.2 Hz), 1.89−1.99 (m, 2H,
2
3,
CHICH CH CHI), 2.06−2.18 (m, 2H, CICH CH CI), 4.15−4.24 (m,
2
2
2
2
1
3
4H, OCH CH ), 4.25−4.30 (m, 2H, CHICH CH CHI). C NMR
2
3
2
2
(CDCl ): δ = 13.7 (OCH CH ), 18.6 (CH CH ), 35.6 (OC(O)CHI),
2
3
4
3
2
3
2
2
After removal of solvent under reduced pressure, the purification by
flash chromatography (silica gel; ethyl acetate/hexane) afforded
62.0 (OCH CH ), 170.8 (OC(O)CI).
2 3
Analytical GPC. The GPC analysis was performed on a Shodex
GPC-101 liquid chromatograph (Tokyo, Japan) equipped with two
Shodex KF-804L mixed gel columns (300 × 8.0 mm; bead size = 7
μm; pore size = 20−200 Å). The eluent was tetrahydrofuran (THF)
with a flow rate of 0.8 mL/min (40 °C). Sample detection and
PhEOH-I (79% yield). 1H NMR (CDCl ): δ = 2.12 (br s, 1H,
3
OCH CH OH), 3.77−3.86 (m, 2H, OCH CH OH), 4.22−4.31 (m,
2
2
2
2
2
H, OCH CH OH), 5.58 (s, 1H, PhCHICO), 7.27−7.33 (m, 3H,
2
2
13
PhH), 7.57−7.60 (m, 2H, PhH). C NMR (CDCl ): δ = 20.1
3
6
616
dx.doi.org/10.1021/ma501569j | Macromolecules 2014, 47, 6610−6618

Macromolecules
Article
quantification were conducted using a Shodex differential refrac-
tometer RI-101 calibrated with known polymer concentrations in
solvent. The monomer conversion was determined from the GPC
peak area. The column system was calibrated using standard PMMAs.
For the polymerizations of BA and the polymerization of MMA from
EMA-III, the samples were also detected using a Wyatt Technology
DAWN EOS MALLS detector (Santa Barbara, CA) equipped with a
Ga−As laser (λ = 690 nm). The refractive index increment dn/dc was
AUTHOR INFORMATION
Corresponding Authors
E-mail agoto@scl.kyoto-u.ac.jp (A.G.).
E-mail kaji@scl.kyoto-u.ac.jp (H.K.).
Notes
■
*
*
The authors declare no competing financial interest.
−1
−1
determined to be for 0.056 mL g for BA and 0.086 mL g for MMA
ACKNOWLEDGMENTS
■
with a Wyatt Technology OPTILAB DSP differential refractometer (λ
This work was partly supported by Grants-in-Aid for Scientific
Research from the Japan Society of the Promotion of Science
(JSPS) and the Japan Science and Technology Agency (JST).
H NMR experiment was carried out with the NMR
spectrometer in the Joint Usage/Research Center (JURC) at
Institute for Chemical Research, Kyoto University.
=
690 nm).
Preparative GPC. The PMMA-I shown below was purified with a
preparative GPC (LC-918, Japan Analytical Industry, Tokyo)
equipped with JAIGEL 1H and 2H polystyrene gel columns (600 ×
1
2
0 mm; bead size = 16 μm; pore size = 20−30 (1H) and 40−50 (2H)
Å). Chloroform was used as eluent with a flow rate of 3.8 mL/min
(
room temperature).
NMR. The NMR spectra were recorded on a JEOL (Japan Electron
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■
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8
3
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(
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■
*
S
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dx.doi.org/10.1021/ma501569j | Macromolecules 2014, 47, 6610−6618