Ultrafast and reversible multiblock formation by the SET-nitroxide radical coupling reaction

Article abstract of DOI:10.1071/CH10092

The single electron transfer-nitroxide radical coupling (SET-NRC) reaction has been used to produce multiblock polymers with high molecular weights in under 3 min at 50°C by coupling a difunctional telechelic polystyrene (Br-PSTY-Br) with a dinitroxide. The well known combination of dimethyl sulfoxide as solvent and Me₆TREN as ligand facilitated the in situ disproportionation of Cu^IBr to the highly active nascent Cu ⁰ species. This SET reaction allowed polymeric radicals to be rapidly formed from their corresponding halide end-groups. Trapping of these carbon-centred radicals at close to diffusion controlled rates by dinitroxides resulted in high-molecular-weight multiblock polymers. Our results showed that the disproportionation of Cu^I was critical in obtaining these ultrafast reactions, and confirmed that activation was primarily through Cu ⁰. We took advantage of the reversibility of the NRC reaction at elevated temperatures to decouple the multiblock back to the original PSTY building block through capping the chain-ends with mono-functional nitroxides. These alkoxyamine end-groups were further exchanged with an alkyne mono-functional nitroxide (TEMPO-≡) and 'clicked' by a Cu ^I-catalyzed azide/alkyne cycloaddition (CuAAC) reaction with N ₃-PSTY-N₃ to reform the multiblocks. This final 'click' reaction, even after the consecutive decoupling and nitroxide-exchange reactions, still produced high-molecular-weight multiblocks efficiently. These SET-NRC reactions would have ideal applications in re-usable plastics and possibly as self-healing materials. CSIRO 2010.

Full text of DOI:10.1071/CH10092

RESEARCH FRONT
Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2010, 63, 1227–1236
Ultrafast and Reversible Multiblock Formation by the
SET-Nitroxide Radical Coupling Reaction
A
A
A
A,B
Jakov Kulis, Craig A. Bell, Aaron S. Micallef, and Michael J. Monteiro
AAustralian Institute for Bioengineering and Nanotechnology, University of Queensland,
Brisbane, Qld 4072, Australia.
B
Corresponding author. Email: m.monteiro@uq.edu.au
The single electron transfer-nitroxide radical coupling (SET-NRC) reaction has been used to produce multiblock polymers
◦
with high molecular weights in under 3 min at 50 C by coupling a difunctional telechelic polystyrene (Br-PSTY-Br)
with a dinitroxide. The well known combination of dimethyl sulfoxide as solvent and Me6TREN as ligand facilitated the
I
0
in situ disproportionation of Cu Br to the highly active nascent Cu species. This SET reaction allowed polymeric radicals
to be rapidly formed from their corresponding halide end-groups. Trapping of these carbon-centred radicals at close to
diffusion controlled rates by dinitroxides resulted in high-molecular-weight multiblock polymers. Our results showed
I
that the disproportionation of Cu was critical in obtaining these ultrafast reactions, and confirmed that activation was
0
primarily through Cu . We took advantage of the reversibility of the NRC reaction at elevated temperatures to decouple
the multiblock back to the original PSTY building block through capping the chain-ends with mono-functional nitroxides.
These alkoxyamine end-groups were further exchanged with an alkyne mono-functional nitroxide (TEMPO–≡) and
I
‘
clicked’ by a Cu -catalyzed azide/alkyne cycloaddition (CuAAC) reaction with N3–PSTY–N3 to reform the multiblocks.
This final ‘click’ reaction, even after the consecutive decoupling and nitroxide-exchange reactions, still produced high-
molecular-weight multiblocks efficiently. These SET-NRC reactions would have ideal applications in re-usable plastics
and possibly as self-healing materials.
Manuscript received: 18 February 2010.
Manuscript accepted: 17 May 2010.
Introduction
[8,9]
systems to create new advanced materials.
In the polymer
I
Nitroxide (aminoxyl) radicals can react with carbon-centred
radicals at close to diffusion controlled rates to form
field, the Cu -catalyzed azide/alkyne cycloaddition (CuAAC)
coupling reaction has been the dominant click reaction used
to prepare complex architectures such as dendrimers, stars,
[
1]
alkoxyamines. This nitroxide radical coupling (NRC) tech-
nique of trapping transient radicals allowed the study of the
complex initiation pathways in free-radical polymerizations,[
and recently emerged as a powerful technique for the synthesis
of complex polymer architectures (termed ATNRC). ATNRC
through trapping of mono- and multifunctional nitroxides can
vary the polymer chain-end functionality or create a variety of
polymer architectures.[ The reaction conditions in these stud-
miktoarm stars, and polymer grafts.[
9,10]
Recently, there has
2,3]
been a significant push to develop new click-type/coupling
chemistries. Important examples include the thiol-based
thiol-ene,[ thiol-yne,
11]
[12]
and thio-bromo
[13]
reactions, as well
[
14]
as hetero-Diels–Alder cycloadditions.
0
SET from Cu significantly increased the rate of carbon-
centred radical production from polymeric chains with halide
end-groups. To achieve this, nascent Cu should be formed
4]
◦
0
ies, however, required high temperatures (e.g., >70 C), very
I
0
high levels of copper (sometimes in a 10-fold excess to halide
groups), and long reaction times (4–12 h). Kinetic simulations
showed that the overall rate of alkoxyamine formation in poly-
meric systems was only limited by the rate of carbon-centred
in situ. By starting with Cu , Cu can be produced in situ
I
I
through the disproportionation of Cu species (e.g., Cu Br; see
Eqn 1) in selective solvents (e.g., dimethyl sulfoxide (DMSO),
alcohols) and ligands (e.g., tris[2-(dimethylamino)ethyl]amine
(Me6TREN)). Single electron transfer-‘living’ radical poly-
merization (SET-LRP) was the first technique to utilize this
approach, allowing the ultrafast production of well-controlled
[
5]
radical formation. Our group attained ultrafast radical forma-
tion through single electron transfer (SET) to achieve a reaction
with ‘click’-type attributes at room temperature, which included
near quantitative yields, selectivity in the presence of functional
groups, rapid rates of alkoxyamine formation, and non-toxic
[15]
acrylate polymerizations at room temperature.
Similarly,
we reported[ the rapid (<7 min) formation of three-arm star
polymers at room temperature using a tri-nitroxide core, lin-
ear polystyrene chains with halide chain-ends (PSTY-Br), and
NRC methodology. We subsequently established that the SET-
NRC reaction was much faster than previously thought, and
highly effective as an ultrafast click-type reaction as demon-
strated by the formation of two-arm PSTY in less than 1 min
6]
[
6]
byproducts. Moreover, thisreactionwasreversibleathightem-
peratures, and we demonstrated the further functionalization of
end-groups through competitive exchange with other functional
[
6]
nitroxides.
Click reactions have become an important tool for the modi-
fication and coupling of small molecule[ and macromolecular
7]
©
CSIRO 2010
10.1071/CH10092
0004-9425/10/081227

RESEARCH FRONT
1
228
J. Kulis et al.
I
Cu Br/Me6 TREN
50/50 v/v toluene/DMSO
25°C
Br
PSTY
Br
O
N
O
O
N
O
PSTY
O
N
O
I
Cu Br/Me TREN
6
CuAAC:
Toluene, Cu Br/PMDETA
RT, 1 h
5
0/50 v/v toluene/DMSO
I
50°C
O
N
O
O
O
O
N
O
1
Br
PSTY
PSTY
N3
PSTY
N3
Route C
m
Toluene
20°C, 5 h
Toluene
120°C, 5 h
1
O
N
OH
O
N
O
HO
N
O
PSTY
O
N
OH
O
N
O
PSTY
O
N
O
Route A
Route B
CuAAC:
Toluene,
Cu Br/PMDETA
RT, 1 h
Toluene
20°C, 5 h
O
N
O
N3
PSTY
N3
1
I
CuAAC:
I
Toluene, Cu Br/PMDETA
RT, 1 h
O
N
O
PSTY
O
N
O
O
N
O
PSTY
O
N
O
N
N
PSTY
N3
N
N3
PSTY
N3
m
Scheme 1. Synthetic strategies for the formation of multiblocks using the SET-NRC reaction, decoupling and exchange with functional nitroxides, and the
reformation of multiblocks by a CuAAC reaction.
at room temperature.[5] In fact, this reaction appeared essen-
tially complete upon the addition of Cu Br. Kinetic simulations
reaction temperature (50 C) for this type of NRC, in order
to solubilize and maintain a homogeneous reaction solution
mixture of the resulting high-molecular-weight polymer prod-
uct throughout the reaction. Fig. 1 shows the molecular weight
distributions (MWDs) through the course of the SET-NRC reac-
tion. After only 3 min, high-molecular-weight polymer formed,
and the MWD remained relatively constant even after prolonged
reaction times.This indicated that most of the coupling reactions
took place within the first 3 min. We observed a distribution
at a lower peak molecular weight (Mp1 = 4240) relative to that
of the starting Br–PSTY–Br (Mp2 = 4920) (see Fig. 1B), and
◦
[6]
I
also showed: negligible radical–radical bimolecular termination
−
4
0
(
<10 %), Cu dominated activation, and confirmed that the
II
persistent radical effect (through deactivation by Cu Br2) had
no effect until conversions of greater than 99%.
Kdisp
I
0
II
2
Cu Br −−−ꢀ Cu + Cu Br2
−−−
(1)
ꢁ
In this work, we demonstrate the utility of the SET-NRC
reaction through the ultrafast formation of multiblock poly-
mers from the reaction between Br–PSTY–Br and a dinitroxide
identified this as monocyclic PSTY with a lower hydrodynamic
(
(
Scheme1).Therearemanyreportsintheliteratureofmultiblock
co)polymers produced from difunctional polymers but none
[19,20]
volume.
Scheme 2 shows the mechanism by which the
monocyclic species can be formed. The peak at Mp3 (9490) did
not change with time and was most likely attributable to a cyclic
structure consisting of two PSTY chains coupled together by
two dinitroxide linkers. It was very unlikely that the cyclic struc-
tures formed by the bimolecular termination of two chain end
with the speed and versatility of the NRC technique. Some exam-
ples include the coupling of dihydroxy telechelic polymers with
◦
[16]
a 2,4-toluene diisocyanate coupling agent at 60 C for 12 h
and the use of N,N-dicyclohexylcarbodiimide (DCC) as a cou-
pling agent for dihydroxy and dicarboxylated polymers with a
[5]
radicals because of the very low probability of the simulta-
[
17]
reaction time of 12 h.
PSTY with telechelic thiol end-groups
neous activation of both ends of a PSTY chain to radicals. The
decoupling experiments described below support this assertion.
The very rapid multiblock formation by SET-NRC in the
batch reaction led us to attempt to control the MWD by feeding
the Br–PSTY–Br into a solution of dinitroxide 1, Me6TREN, and
has also been homo-coupled to form disulfide linkages between
the PSTY building blocks.[
18]
Results and Discussion
I
The basic building block, Br–PSTY–Br, was synthesized by
ATRP to produce a polymer with a number-average molecular
weight, Mn, of 4700 and a polydispersity index (PDI) of 1.09.
Cu Br in 50/50 v/v toluene/DMSO. Under these conditions, the
molecular weight should increase linearly with the amount of
Br–PSTY–Br fed into the reaction mixture. Fig. 2A shows the
evolution of the MWD as a function of Br–PSTY–Br fed into a
II
I
A large amount of Cu Br2 (20% relative to Cu Br) in the reac-
tion mixture ensured a narrow molecular weight distribution and
high chain-end functionality. This Br–PSTY–Br building block
formed high-molecular-weight multiblocks being linked by the
dinitroxide 1 through the SET-NRC reaction. This one pot batch
I
reaction mixture that contained an equimolar ratio of Cu Br to
polymer Br end-groups. It can be seen that after the addition of
only 0.1 equivalents of Br–PSTY–Br to 1, a new peak at 6309
(log MP = 3.8) formed, assigned to a PSTY chain with a dinitrox-
ide attached to both ends, along with higher-molecular-weight
species. With an increase in the amount of Br–PSTY–Br fed into
◦
I
reaction at 50 C contained Cu Br and Me6TREN in a 50/50 v/v
toluene/DMSO solvent mixture. We used a higher than normal

RESEARCH FRONT
Multiblock Formation by SET-NRC
1229
(a)
MWD was near identical to the feed reaction after the addition
of 0.1 equivalents of Br–PSTY–Br (Fig. 3, curve c).
4
3
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
.5
.0
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
These results suggest that the rate of disproportionation plays
an important role in controlling the MWD, especially during
the feed process. In batch reactions, the SET-NRC process was
very fast relative to disproportionation so that low levels of
0
3
6
1
min
min
min
80 min
II
deactivator (Cu Br2) were present in the reaction mixture (as
I
Cu Br was added as the last reagent just before the start of
the reaction). Kinetic simulations showed that the concentra-
II
tion of Cu Br2 from this type of reaction increased linearly with
conversion.[ In a feed process, Cu Br has time to dispropor-
5]
I
tionate, allowing the copper species to reach their equilibrium
II
concentrations. This resulted in a high Cu Br2 concentration
2
.0
3.0
4.0
5.0
6.0
7.0
8.0
at the initial stage of the reaction, in which deactivation of the
Log (MW)
II
chain-end radicals by Cu Br2 now successfully competed with
(b)
•
nitroxide trapping. Therefore, α,ω-telechelic PSTY (i.e., ON–
4
3
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
.5
.0
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
T–PSTY–Br) initially formed, and over time could form higher
molecular weight polymer.
Mp2
0
3
min
min
An important feature of the NRC methodology was the
reversibility of this reaction at elevated temperatures. In our
6 min
80 min
[6]
previous work, we used the reversibility of this reaction to
1
change the chemical functionality of the polymer chain-ends
through exchange with functional nitroxides. Here, the multi-
Mp1
◦
Mp3
block polymer was decoupled at 120 C in the presence of
either a high excess of TEMPO-OH (route A) or TEMPO–≡
(route B) relative to the original PSTY building block, and
the chain ends capped with the respective functional nitroxide.
Fig. 4A shows the near quantitative cleavage of the multiblock
3
.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
(curve a) to give lower molecular weight difunctional PSTY
Log (MW)
capped with TEMPO-OH (curve b). The MWD of the multi-
block (Mn = 36970, PDI = 5.29) decreased to a value close to
that of the original starting PSTY building block with an Mn of
5010 and PDI of 1.10. Assignments of the TEMPO-OH groups
Fig. 1. Weight-normalized size exclusion chromatography (SEC) for
the batch SET-NRC coupling reaction between Br–PSTY–Br (Mn = 4700,
I
PDI = 1.09) and dinitroxide using Cu Br (three-fold excess to bromine
◦
1
end-groups) at 50 C in 50/50 v/v toluene/DMSO and Me6TREN. (A)
by H NMR spectroscopy confirmed the capping of the poly-
Weight-normalized SEC for overall MWD. (B) Weight-normalized SEC of
lowMWD(Mp1 = 4240, Mp2 = 4920, Mp3 = 9490).AllSECchromatograms
were weight normalized and then replotted as w(M) versus log (MW).
mer chain-ends by these nitroxides (Fig. 5B). The characteristic
peaks for the methyl groups on the nitroxide (denoted as h), and
the characteristic splitting of the broad peak f were consistent
1
[2,6]
with previously reported H NMR spectra
of small molecule
diastereomers capped with nitroxides. Exploiting the versatility
of the decoupling and exchange reaction, we then exchanged the
TEMPO-OH on the PSTY chain ends with an alkyne TEMPO
(TEMPO–≡). Curve c in Fig. 4A shows only a slight change in
the MWD (Mn = 5350, PDI = 1.10). The distinct l and k reso-
the reaction, the Mn increased from 4700 to 32000 (Fig. 2C)
and the PDI increased from 1.09 to 3.5 (Fig. 2D). Increas-
I
ing the Cu Br stoichiometry to three equivalents relative to the
Br end-groups resulted in higher Mn and PDI values (Fig. 2C
and D).
1
nances arising from the alkyne moiety in the H NMR spectrum
These results were puzzling. We did not expect high-
molecular-weight polymer after the addition of 0.1 equivalents
of Br–PSTY–Br because of the large excess of dinitroxide rela-
tive to Br groups. Based on previous reactions,[ we expected
that the Br chain-ends would simply be exchanged for nitroxides.
To unravel this conundrum, we first conducted a batch reaction
with only 0.1 equivalents of Br–PSTY–Br relative to dinitrox-
(Fig. 5C) confirmed exchange of theTEMPO-OH toTEMPO–≡
end-groups. These exchange reactions, through a two-step pro-
cess to obtain the alkyne-functionalized polymer, demonstrated
the versatility of the nitroxide exchange process. It was also
possible to obtain the alkyne-functionalized polymer directly by
performing the multiblock decoupling reaction in the presence
of TEMPO–≡. Fig. 4B shows the near quantitative cleavage of
the multiblock (curve a) to give lower molecular weight difunc-
tional PSTY capped with TEMPO–≡ (curve b) (Mn = 5470 and
PDI = 1.10). The capping with TEMPO–≡ during the decou-
6]
I
ide (Fig. 3, curve a). The Cu Br, as in all previous experiments,
was added as the final reagent just before the start of the reac-
tion. As expected, there was a slight shift to a higher molecular
•
•
1
weight corresponding to ON–T–PSTY–T–NO , a second peak
corresponding to the coupling of two PSTY chains, and a low
population of high-molecular-weight species. The next experi-
ment was carried out under identical conditions, but this time
pling process was again confirmed by H NMR spectroscopy
(Fig. 5D).
Importantly, the decoupling reaction shed light on the nature
of the cyclic polymer products obtained from the multiblock
synthesis (Fig. 1). As shown in Fig. 4C, the MWD of the low
Mn cyclic polymer (Mp1 = 4263; curve a) shifts to higher Mn
(Mp2 = 5702; curve b) upon decoupling because of an increase in
hydrodynamic volume associated with the change from a cyclic
structure to a linear structure. The decoupling process also gave
I
the Cu Br was added first to the reaction mixture containing
1
3
, Me6TREN, DMSO, and toluene; and left to equilibrate for
0 min. We observed a very different MWD (Fig. 3, curve b),
one with high molecular weight, when Br–PSTY–Br was added
as the last reagent and just before the start of the reaction. This

RESEARCH FRONT
1
230
J. Kulis et al.
Br
Br
Br
n
n
SET activation
nϪ1
O
O
n
O
O
O
O
O
O
O
N
O
O
O
O
N
O
NRC
Br
O
N
O
O
O
O
N O
n
n
O
O
O
O
SET activation
O
N
O
O
O
O
NO
O
N
O
O
O
O
N
O
n
NRC
nϪ1
O
O
O
O
n
n
O
O
O
O
Scheme 2. Proposed mechanism for the formation of monocyclic PSTY chains.
rise to a mono-modal distribution, indicative of near quantitative
decoupling of the multiblock and cyclic products. We can con-
sequently conclude that the low Mn cyclic structure arises from
the coupling of the chain ends of a single PSTY chain through
a single dinitroxide (Scheme 2) rather than from the radical–
radical termination of two simultaneously activated chain ends.
The C–C bond that results from the latter process (i.e., through
radical termination between radicals on each end of the polymer
chain) would not decouple under these conditions. The presence
of cyclic PSTY species observed in our multiblock systems was
not unexpected. Lonsdale et al.[ showed that cyclization of
α,ω-telechelic PSTY (i.e., ≡–PSTY–N3) by the CuAAC reac-
tion in toluene resulted in a high yield (∼83%) of monocyclic
polymer. Their results were in agreement with predicted values
weight distribution (curve b) was produced by route B, and the
lowest distribution (curve c) produced by route A. The latter two
multiblock formations showed lower molecular weight distribu-
tions. This was presumably because of the increased number of
synthetic steps and consequent loss of chain-end functionality.
In comparison to the multiblock formed from Br–PSTY–Br and
dinitroxide (1) there was no evidence of monocyclic or dicyclic
species in the size exclusion chromatograms (Fig. 7, curves b
and c).The peak (Mp2 in curve a) did not move to higher molecu-
lar weight over time and we postulated this to be a small amount
of dicyclic PSTY (i.e., two PSTY chains to form one cyclic
structure).
20]
determined from the Jacobson–Stockmyer equation.[ In our
21]
Conclusion
SET-NRC system, monocyclic polymers can only form from
the precursor ON–T–PSTY–Br. However, the many competitive
SET-NRC reactions produce high-molecular-weight multiblock
polymers from Br–PSTY–Br in the presence of a dinitroxide
•
◦
0
reaction with free dinitroxide and other functional PSTY chains
in under 3 min at 50 C. The highly active Cu , formed in situ
•
I
results in a low amount of ON–T–PSTY–Br and thus a small
from the disproportionation reaction of Cu Br in the presence of
amount of cyclic polymer in our system.
DMSO and Me6TREN, significantly accelerates the activation
of the polymer halides to the carbon-centred macroradicals that
are subsequently trapped by the nitroxides. Our results showed
We demonstrated the reversibility and orthogonal nature
of the NRC decoupling reactions by a CuAAC click reaction
between the ≡–TEMPO–PSTY–TEMPO–≡ and N3–PSTY–N3.
The three different routes (see Scheme 1) gave high-molecular-
weight polymer after 60 min (Fig. 7). The highest molecular
weight polymer produced was by route C (curve a) because of the
minimalnumberofreactionstepstoproducethestartingmaterial
I
0
II
that the disproportionation reaction of Cu to give Cu and Cu
was critical in obtaining ultrafast reactions. The results also con-
0
firmed that activation was primarily through Cu , thus providing
additional support for the SET mechanism. A feature of this
NRC reaction is its reversibility at elevated temperatures.Taking
advantageofthis, wedecoupledthemultiblockpolymertoobtain
(
≡–TEMPO–PSTY–TEMPO–≡). A slightly lower molecular

RESEARCH FRONT
Multiblock Formation by SET-NRC
1231
(
A)
(B)
4
4
3
3
2
2
1
1
0
0
.5
.0
.5
.0
.5
.0
.5
.0
.5
.0
0.50
.45
0.40
4
.5
0.20
0
0
0
0
.0 equiv.
.1 equiv.
.2 equiv.
.3 equiv.
0.0 equiv.
0.1 equiv.
0.2 equiv.
0
4.0
3.5
Time
0.3 equiv.
0.4 equiv.
0.5 equiv.
0.6 equiv.
0.7 equiv.
0.8 equiv.
0.9 equiv.
1.0 equiv.
0
0
.15
.10
0
0
0
0
.35
.30
.25
.20
0.4 equiv.
.5 equiv.
0.6 equiv.
3
2
.0
.5
0
Time
0
0
0
1
.7 equiv.
.8 equiv.
.9 equiv.
.0 equiv.
2.0
1.5
1.0
0.15
.10
0.05
0.00
0
0.05
0.00
0
0
.5
.0
3
.0
3.5
4.0
4.5
5.0
5.5
6.0
3
.0
3.5
4.0
4.5
5.0
5.5
6.0
Log (MW)
Log (MW)
(
C)
(D)
4
3
3
2
2
1
1
0000
5000
0000
5000
0000
5000
0000
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
(
b)
(
b)
(
a)
(
a)
5
000
0
0
.0
0.2
0.4
0.6
0.8
1.0
0.0
0.2
0.4
0.6
0.8
1.0
Br–PSTY–Br equiv. added via feed
Br–PSTY–Br equiv. added via feed
I
Fig. 2. SET-NRC coupling reaction performed by feeding Br–PSTY–Br (Mn = 4700, PDI = 1.09) into a solution of dinitroxide 1, Cu Br and Me6TREN in
◦
I
5
0/50 v/v toluene/DMSO at 50 C. (A) Weight-normalized size exclusion chromatography (SEC) for Cu Br (1 equivalent relative to bromine end-groups)
I
over 4 h. (B) Weight-normalized SEC for Cu Br (3 equivalents relative to bromine end-groups) over 4 h. (C) Mn versus equivalents of Br–PSTY–Br added by
the feed. (D) PDI versus equivalents of Br–PSTY–Br added by the feed. Curve a: 1 equivalent Cu Br relative to bromine end-groups. Curve b: 3 equivalents
of Cu Br relative to bromine end-groups. All SEC chromatograms were weight normalized and then replotted as w(M) versus log (MW).
I
I
the original PSTY building block capped with TEMPO-OH
or TEMPO–≡. An exchange reaction between HO–TEMPO–
PSTY–TEMPO–OH and TEMPO–≡ gave ≡–TEMPO–PSTY–
TEMPO–≡, which was then further ‘clicked’with N3–PSTY–N3
to reform multiblocks. Size exclusion chromatography con-
firmed the efficiency of these consecutive decoupling, nitroxide
exchange, and CuAAC reactions.
99.8%), toluene (HPLC, LABSCAN, 99.8%), dimethyl sulfox-
ide (DMSO, LABSCAN, 99.8%), triethylamine (TEA, Fluka,
purum), dimethyl 2,6-dibromoheptanedioate (DMDBHD,
I
Aldrich, 97%), cuprous bromide (Cu Br, Aldrich, 99.999%),
II
ꢀ
ꢀ
ꢀꢀ
cupric bromide (Cu Br2, Aldrich, 99%), and N,N,N ,N ,N -
pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%) were
all used as received. Styrene (STY, Aldrich, 99%, 10–15 ppm
4
-tert-butyl catechol inhibitor) was purified by passage through
Experimental
a column of activated basic alumina (Aldrich, Brockmann I,
standard grade, ∼150 mesh, 58 Å). Me6TREN was synthe-
sized following the previously described method by Ciampolini
et al.[ TEMPO–≡ was synthesized following the previously
described method by Reiser et al.[
Materials
Silica gel 60 (230–400 mesh ATM (SDS), TLC plates (sil-
ica gel 60 F254), sodium chloride (Univar, 99.9%), methanol
22]
23]
(
Univar, AR grade), sodium hydrogen carbonate (Merck,
AR grade), n-hexane for gas chromatography (GC) analy-
sis (Scharlau, 96%), terephthaloyl chloride (Aldrich, >99%),
sulfuric acid (Laboratory-Scan, AR grade), acetonitrile
Synthesis
4
(
-Hydroxy-2,2,6,6-tetramethylpiperidin-1-yloxyl
TEMPO-OH) (Fig. 6)[
6]
(
(
Laboratory-Scan, HPLC grade), hydrogen peroxide 30% w/w
Univar, AR grade), 2,2,6,6-tetramethyl-4-piperidinol (Aldrich,
To a solution of 2,2,6,6-tetramethyl-4-piperidinol (5.00 g,
31.8 mmol) in MeOH (59.2 mL) was added NaHCO3 (2.13 g,
25.4 mmol), Na2WO4·2H2O (0.305 g, 0.923 mmol), and MeCN
(4.23 mL, 82.5 mmol). H2O2 30% w/w (11.8 mL, 0.110 mol)
9
8%), chloroform (CHCl3, Pronalys, 99%), dichloromethane
DCM, Labscan, AR grade), diethyl ether (Et2O, Pronalys,
AR grade), tetrahydrofuran (THF, HPLC grade, Lichrosolv,
(

RESEARCH FRONT
1
232
J. Kulis et al.
1
0
0
0
0
0
0
0
0
0
0
.0
.9
.8
.7
.6
.5
.4
.3
.2
.1
.0
(A)
1
.4
4.5
Starting Br–PSTY–Br
160
140
1.2
1.0
0.8
0.6
0.4
0.2
4
3
.0
.5
1.2
Dinitroxide
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
(b)
3.0
2.5
2.0
120
(a)
(c)
(a)
100
80
(
a)
1
.5
1.0
.5
0.0
5.5
(c)
0
60
(b)
2
.5
3.5
4.5
40
Log (MW)
20
0
0.0
7.0
(
c)
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
Log (MW)
(
b)
(B)
1
1
1
40
20
00
1.2
1.0
3
.0
3.5
4.0
4.5
5.0
5.5
Log (MW)
(b)
(a)
0
0
0
.8
.6
.4
Fig. 3. Weight-normalized size exclusion chromatography (SEC) for (a) a
batch SET-NRC reaction with 0.1 equivalents of Br–PSTY–Br (Mn = 4700,
8
6
0
0
I
PDI = 1.09) relative to dinitroxide with Cu Br added last, (b) a batch reaction
with 0.1 equivalents of Br–PSTY–Br (Mn = 4700, PDI = 1.09) relative to
I
40
dinitroxide 1 and letting the Cu Br equilibrate for 30 min, and then adding the
polymer last, (c) a feed reaction when 0.1 equivalents of Br–PSTY–Br were
0.2
2
0
I
fed into the reaction mixture using Cu Br (3 equivalents relative to bromine
◦
0
3
0.0
6.5
end-groups). Reactions were carried out at 50 C using Me6TREN in 50/50
.0
3.5
4.0
4.5
5.0
5.5
6.0
v/v toluene/DMSO. All SEC chromatograms were weight normalized and
then replotted as w(M) versus log (MW).
Log (MW)
(
C)
1
40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
was then added dropwise. After stirring in air at room temper-
ature for 38 h the orange/red solution was diluted with brine
120
100
(b)
(
100 mL) and extracted with dichloromethane (3 × 60 mL).
The organic layer was washed with brine (60 mL) and dried
over Na2SO4. Removal of the solvent under vacuum gave a
bright orange residue that was triturated with hexane to yield
80
M
p1
Mp2
(
a)
6
4
2
0
0
0
0
4
-hydroxy-2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPOL) as
an orange solid (4.84 g, 88%). Rf (50% EtOAc/hexane) 0.22;
−
1
νmax/cm
3402br, 2974, 2948, 2928, 2858br. m/z (GC-MS,
+
+
EI ) 172 (M , 11%), 158 (6), 142 (8), 85 (33), 71 (100),
3.4
3.6
3.8
4.0
4.2
5
7 (51), 41 (97). Only one peak was observed in the GC-MS
Log (MW)
chromatogram.
Fig. 4. Weight-normalized distributions by size exclusion chromatography
SEC). (A) Curve a: Multiblock formed through the batch SET-NRC reac-
(
Dinitroxide 1 (Fig. 8), Bis(2,2,6,6-tetramethylpiperidin-
tion between Br–PSTY–Br (Mn = 4700, PDI = 1.09) and dinitroxide using
4
-yloxyl) Terephthalate
I
◦
Cu Br (3 equivalents relative to bromine end-groups) at 50 C in 50/50 v/v
toluene/DMSO and Me6TREN. Curve b: Decoupled multiblock in the pres-
Terephthaloyl chloride (0.725 g, 3.57 mmol) was dissolved
in dry toluene (17.9 mL) under argon. A solution of TEMPOL
1.84 g, 10.7 mmol) and dry TEA (4.998 mL, 35.3 mmol) in
dry toluene (28.6 mL) was added dropwise to the stirring acid
chloride solution. After stirring at room temperature for 48 h
under argon, the solvent was removed under vacuum yielding an
orange/red solid which was purified by flash chromatography
◦
ence ofTEMPO-OH for 5 h in toluene at 120 C. Curve c: Nitroxide exchange
reaction of HO-TEMPO–PSTY–TEMPO-OH with TEMPO–≡ for 5 h in
(
◦
toluene at 120 C. (B) Curve a: identical to curve a in (A). Curve b: Decou-
◦
pled multiblock in the presence of TEMPO–≡ for 5 h in toluene at 120 C.
(
C) Magnified view of the low molecular weight region of (B). All SEC
chromatograms were weight normalized and then replotted as w(M) versus
log (MW).
(
0
50/50 EtOAc/hexane) (0.604 g, 36%). Rf (50% EtOAc/hexane)
.55. The presence of the paramagnetic nitroxide moieties
Synthesis of Polymers
precluded direct analysis by NMR spectroscopy. Consequently,
dinitroxide (1) was reduced to the corresponding hydroxylamine
with phenylhydrazine. δH (CDCl3): 1.28 (s, 12H, CH3CNO),
Br–PSTY–Br (Fig. 9)
Styrene (15.39 g, 0.1480 mol), PMDETA (0.351 mL, 1.68 ×
−
3
−3
1
4
.29 (s, 12H, CH3CNO), 1.80 (m, 4H, CHCH2C), 2.06 (m,
H, CHCH2C), 5.33 (m, 2H, COOCHCH2), 6.83 (m, phenyl-
10 mol), DMDBHD (0.73 mL, 3.36 × 10 mol), and
II
−4
Cu Br2/PMDETA (0.133 g, 3.36 × 10 mol) were added to a
Schlenk flask and deoxygenated by bubbling with argon for
20 min with vigorous stirring. The contents were stirred for an
hydrazine), 7.26 (m, phenylhydrazine), 7.35 (s, benzene), 8.05
1
(
s, 4H, ArH). The H NMR spectrum also contained resonances
I
−3
attributable to excess phenylhydrazine and its oxidation product,
benzene.
hour under argon. Cu Br (0.241 g, 1.68 × 10 mol) was then
added under a positive argon flow and the contents deoxygenated

RESEARCH FRONT
Multiblock Formation by SET-NRC
1233
(
A)
(B)
g
a, b, c, e
g
a, b, c, e, h, i
Br
e
b
Br
f
a
c
n
h
n
e
b
O
f
c
a
O
n
i
N
n
N
d
O
O
O
O
d
H O
j
h
O
d
O
O
O
2
HO
i
OH
H O
2
g
CHCl3
CHCl3
g
d
f, j
f
f
4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ppm
4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ppm
h
7
.5 7.0 6.5 6.0 5.5
5.0 4.5 4.0 3.5 3.0 2.5
2.0 1.5 1.0
a, b, c, e, h, i
0.5 ppm
7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 ppm
(
C)
g
(D)
g
a, b, c, e, h, i
H O
H O
2
2
h
h
e
b
e
b
O
f
c
a
O
O
f
c
a
O
n
i
N
n
n
N
i
N
N
n
h
O
O
O
O
h
O
O
O
O
j
i
O
O j
k
O
O
i
k
d
d
CHCl3
CHCl3
g
g
I
I
k
k
d
d
f
j
f
j
f
f
4
.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ppm
4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ppm
h
h
l
l
7.5 7.0 6.5 6.0 5.5
5.0 4.5 4.0 3.5 3.0 2.5
2.0 1.5 1.0
0.5 ppm
7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 ppm
1
Fig. 5. H NMR spectra of: (A) starting Br–PSTY–Br (Mn = 4700, PDI = 1.09). (B) HO-TEMPO–PSTY–TEMPO-OH (Mn = 5010, PDI = 1.10) after
exchange reactions with multiblocks. (C) ≡–TEMPO–PSTY–TEMPO–≡ (Mn = 5350, PDI = 1.10) after nitroxide exchange with HO-TEMPO–PSTY–
TEMPO-OH (Mn = 5010, PDI = 1.10). (D) ≡–TEMPO–PSTY–TEMPO–≡ (Mn = 5470, PDI = 1.10) after exchange reactions with multiblocks. Inset:
expanded region between 3 and 5 ppm.
•
volume MeOH, recovered by vacuum filtration, and washed
exhaustively with water and MeOH. The azide-functionalized
polymer was dried under vacuum (Mn = 4640, PDI = 1.09).
O
N
OH
Fig. 6. TEMPO-OH.
SET-NRC
Batch Process
by bubbling with argon for a further 5 min. The reaction vessel
was then sealed and placed in an oil bath at 80 C. The reac-
Br–PSTY–Br (Mn = 4700, PDI = 1.09, 120 mg, 2.56 ×
◦
−
5
−5
1
0
mol), dinitroxide 1 (10.6 mg, 2.22 × 10 mol), and
tion was stopped by quenching in liquid nitrogen followed by
exposure to air. The contents were diluted with DCM and passed
through an activated basic alumina column. The solvent was
removed under vacuum and the residue dissolved in a mini-
mal amount of DCM. The polymer was precipitated into 10×
volume of MeOH, collected by filtration, and dried under vac-
uum. The resulting polymer was analyzed by size exclusion
chromatography (SEC) (Mn = 4700, PDI = 1.09).
−
4
Me6TREN (35.2 mg, 1.53 × 10 mol) (Fig. 11) were placed
in a 10 mL Schlenk flask and dissolved in 50/50 v/v
toluene/DMSO (1 mL). Oxygen was removed from the solution
I
by three successive freeze–pump–thaw cycles. Cu Br (22.0 mg,
−
4
1
.54 × 10 mol) was then added to the frozen solution and the
flaskre-evacuated.TheSchlenkflaskwasback-filledwithargon,
◦
sealed, and placed in an oil bath at 50 C with stirring. The reac-
tion was sampled at regular time intervals and analyzed by SEC.
N3–PSTY–N3 (Fig. 10)
−
3
General Method for Feed Formation of Multiblocks
NaN3 (139.12 mg, 2.14 × 10 mol) was added to a
solution of Br–PSTY–Br (Mn = 4700, PDI = 1.09, 503 mg,
−
5
Dinitroxide 1 (21.2 mg, 4.44 × 10 mol) and Me6TREN
−
4
−4
−4
1
.07 × 10 mol) in DMF (3 mL). The reaction mixture was
(70.4 mg, 3.06 × 10 mol or 23.5 mg, 1.02 × 10 mol) were
◦
stirred for 16 h at 25 C. The polymer was precipitated in a 10×
placed in a 10 mL Schlenk flask and dissolved in 50/50 v/v

RESEARCH FRONT
1
234
J. Kulis et al.
−
4
3
.0
.5
.0
.5
.0
.5
.0
Me6TREN (35.2 mg, 1.53 × 10 mol) were placed in a 10 mL
Schlenk flask and dissolved in 50/50 v/v toluene/DMSO
0.55 mL). Oxygen was removed from the solution by three suc-
2
2
1
1
0
0
(
cessive freeze–pump–thaw cycles. The Schlenk flask was back-
I
−4
filled with argon, and then Cu Br (22.0 mg, 1.54 × 10 mol)
Mp3 (c)
was added to the solution. The Schlenk flask was sealed and
◦
placed in an oil bath at 50 C, with stirring. The reaction was
sampled at regular time intervals and analyzed by SEC.
(b)
Mp1
Batch Process – 0.1 Equivalents of Br–PSTY–Br,
Letting Cu Species Reach Equilibrium First
Mp2
(a)
−
5
Dinitroxide 1 (10.6 mg, 2.22 × 10 mol) and Me6TREN
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
−
4
(
35.2 mg, 1.53 × 10 mol) were placed in a 10 mL Schlenk
Log (MW)
flask and dissolved in 50/50 v/v toluene/DMSO (0.45 mL).
Oxygen was removed from the solution by three successive
freeze–pump–thaw cycles. The Schlenk flask was back-filled
Fig. 7. Weight-normalized size exclusion chromatography (SEC)
for multiblock formed by the CuAAC coupling reaction through:
I
−4
(
a) route
PDI = 1.06) and N3–PSTY–N3 (Mn = 4640, PDI = 1.09), (b) route B
between ≡–TEMPO–PSTY–TEMPO–≡ (Mn = 5470, PDI = 1.10) and
C
–
between ≡–TEMPO–PSTY–TEMPO–≡ (Mn = 5350,
with argon, and then Cu Br (22.0 mg, 1.54 × 10 mol) was
added to the solution under a positive argon flow. The Schlenk
◦
–
flask was sealed and placed in an oil bath at 50 C, with stirring
for 30 min to let the copper species reach equilibrium. Br–
N3–PSTY–N3 (Mn = 4640, PDI = 1.09), and (c) route A – between
≡
–TEMPO–PSTY–TEMPO–≡(Mn = 5350, PDI = 1.10)andN3–PSTY–N3
−6
PSTY–Br (Mn = 4700, PDI = 1.09, 12.0 mg, 2.55 × 10 mol)
I
(
Mn = 4640, PDI = 1.09). All reactions used Cu Br/PMDETA in toluene at
was dissolved in 50/50 v/v toluene/DMSO (0.1 mL). Oxygen
was removed from the solution by three successive freeze–
pump–thaw cycles. The Br–PSTY–Br solution was then placed
under an argon atmosphere and added to the previous solution
in one batch. The reaction was sampled at regular time intervals
and analyzed by SEC.
◦
2
5 C. All SEC chromatograms were weight normalized and then replotted
as w(M) versus log (MW).
O
O
O
O
O
N
N O
1
Decoupling and Exchange Reactions
Nitroxide Exchange of Multiblock with TEMPO–≡
Multiblock (Mn = 36970, PDI = 5.29, 106.6 mg) and
Fig. 8. Dinitroxide 1.
−
3
Br
Br
TEMPO–≡ (272.6 mg, 1.30 × 10 mol) were placed in a
Schlenk flask equipped with a Teflon screw cap and dissolved
in toluene (1.2 mL). Oxygen was removed from the solution by
purging with argon (15 min). The flask was sealed under argon
n
n
O
O
O
O
◦
and placed in an oil bath at 120 C with stirring for 5 h. The reac-
Fig. 9. Br–PSTY–Br.
tion mixture was quenched by cooling in an ice bath and the
solvent removed under a flow of air. The residue was dissolved
in a minimal amount of DCM and the polymer precipitated in
a 10× volume of MeOH. The resulting white precipitate was
collected by vacuum filtration and dried under vacuum, to give
N3
N3
n
n
O
O
O
O
≡
–TEMPO–PSTY–TEMPO–≡ (Mn = 5470, PDI = 1.10).
Fig. 10. N3–PSTY–N3.
Nitroxide Exchange of Multiblock with TEMPO-OH
Multiblock (Mn = 36970, PDI = 5.29, 119.5 mg) and
−
3
toluene/DMSO (1.0 mL). Oxygen was removed from the solu-
tion by three successive freeze–pump–thaw cycles. The Schlenk
flask was back-filled with argon, and then Cu Br (44.1 mg,
TEMPO-OH (305.6 mg, 1.77 × 10 mol) were placed in a
Schlenk flask equipped with a Teflon screw cap and dissolved
in toluene (1.4 mL). Oxygen was removed from the solution by
purging with argon (15 min). The flask was sealed under argon
I
−
4
−4
3
.07 × 10 mol or 14.7 mg, 1.02 × 10 mol) was added to
◦
the solution under a positive argon flow. The Schlenk flask was
sealed and placed in an oil bath at 50 C with stirring. Br–PSTY–
and placed in an oil bath at 120 C with stirring for 5 h. The
◦
reaction mixture was quenched by cooling in an ice bath and
the solvent removed under a flow of air. The residue was dis-
solved in a minimal amount of dichloromethane and the polymer
precipitated in a 10× volume of MeOH. The resulting white
precipitate was collected by vacuum filtration and dried under
vacuum, to give HO-TEMPO–PSTY–TEMPO-OH (Mn = 5010,
PDI = 1.10).
−
5
Br (Mn = 4700, PDI = 1.09, 240 mg, 5.11 × 10 mol) was
dissolved in 50/50 v/v toluene/DMSO (1.0 mL). Oxygen was
removed from the solution by three successive freeze–pump–
thaw cycles.The Br–PSTY–Br solution was then placed under an
argon atmosphere and added to the previously degassed solution
−
1
using a syringe pump (1.0 mL at 0.0042 mL min ).The reaction
was then sampled at regular time intervals and analyzed by SEC.
Nitroxide Exchange of HO-TEMPO–PSTY–TEMPO-OH
Batch Process – 0.1 Equivalents of Br–PSTY–Br
with TEMPO–≡
Br–PSTY–Br (Mn = 4700, PDI = 1.09, 12 mg, 2.55 ×
HO-TEMPO–PSTY–TEMPO-OH (Mn = 5010, PDI = 1.10,
−
6
−5
−5
1
0
mol), dinitroxide 1 (10.6 mg, 2.22 × 10 mol), and
60.0 mg, 1.20 × 10 mol) and TEMPO–≡ (100.92 mg, 4.80 ×

RESEARCH FRONT
Multiblock Formation by SET-NRC
1235
Br
O
N
O
O
O
O
N
O
O
N
O
O
O
O
N O
n
n
n
n
O
O
O
O
O
O
O
O
m
Fig. 11. Multiblocks.
N
N
N3
O
N
O
O
N
n
N
O
n
n
n
O
O
O
O
O
O
O
O
m
Fig. 12. Reformed multiblocks.
−
4
1
0
mol) were placed in a Schlenk flask equipped with a
Techniques
SEC
Teflon screw cap and dissolved in toluene (0.9 mL). Oxygen
was removed from the solution by purging with argon (15 min).
All polymer samples were dried under vacuum for 2 days
The flask was sealed under argon and placed in an oil bath at
◦
at 25 C before analysis. The dried polymer was dissolved in
◦
1
20 C with stirring for 5 h. The reaction mixture was quenched
−
1
THF (Labscan, 1 mg mL ) and the resulting solution filtered
using a 0.45 μm PTFE syringe filter. Analysis of the MWDs of
the polymers was accomplished using a Waters 2695 Separa-
tions Module, fitted with a Waters 410 refractive index detector
by cooling in an ice bath and the solvent removed under a flow
of air. The residue was dissolved in a minimal amount of DCM
and the polymer precipitated in a 10× volume of MeOH. The
resulting white precipitate was collected by vacuum filtration
and dried under vacuum, to give ≡–TEMPO–PSTY–TEMPO–≡
◦
maintained at 35 C, a Waters 996 Photodiode Array detector
and two Ultrastyragel linear columns (7.8 × 300 mm) arranged
(
Mn = 5350, PDI = 1.10).
◦
in series. These columns were maintained at 40 C for all anal-
yses, and were capable of separating polymers in the molecular
weightrangeof500to4million g mol withhighresolution.All
samples were eluted at a flow rate of 1.0 mL min . Calibration
was performed using narrow molecular weight PSTY standards
NRC Functionalization of Br–PSTY–Br with TEMPO–≡
Br–PSTY–Br (Mn = 4700, PDI = 1.09, 100 mg, 2.13 ×
−1
−
1
−5
−5
1
0
mol), TEMPO–≡ (10.75 mg, 5.11 × 10 mol), and
−
5
−1
Me6TREN (10.78 mg, 4.68 × 10 mol) were placed in a 10 mL
(PDI ≤ 1.1) that ranged from 500 to 2 million g mol . Data
Schlenk flask and dissolved in 50/50 v/v toluene/DMSO
acquisition was performed using Empower software and molec-
ular weights were calculated relative to PSTY standards. All
SEC chromatograms were weight normalized and then replotted
as w(M) versus log (MW).
(
1.1 mL). Oxygen was removed from the solution by purging
I
−5
with argon (15 min). Cu Br (6.72 mg, 4.68 × 10 mol) was
then added under a positive argon flow. The reaction vessel
◦
was sealed and placed in an oil bath at 25 C with stirring for
0 min. The contents were then diluted with DCM and passed
1H and 13C NMR Spectroscopy
3
through an activated basic alumina column. The solvent was
removed under reduced pressure, and the residue was dissolved
in a minimal amount of DCM. The polymer was precipitated in
a 10× volume of MeOH. The resulting white precipitate was
collected by vacuum filtration and dried under vacuum, to give
All NMR spectra were recorded on a Bruker DRX 400 MHz
or Bruker DRX 500 MHz spectrometer in deuterated chloroform
utilizing an internal lock from residual solvent.
Attenuated Total Reflectance-Fourier Transform
Infrared Spectroscopy (ATR-FTIR)
≡–TEMPO–PSTY–TEMPO–≡ (Mn = 5350, PDI = 1.06).
ATR-FTIR spectra were obtained using a horizontal, single
bounce, diamond ATR accessory on a Nicolet Nexus 870 FT-IR.
Cu-Catalyzed Huisgen 1,3-Cycloaddition (CuAAC)
Reaction of ≡–TEMPO–PSTY–TEMPO–≡ with
N3–PSTY–N3 to Reform Multiblock (Fig. 12)
−
1
Spectra were recorded between 4000 and 500 cm for 32 scans
−
1
−1
at 4 cm resolution with an OPD velocity of 0.6289 cm s .
Solids were pressed directly onto the diamond internal reflection
element of the ATR without further sample preparation.
A typical procedure is as follows:
≡
–TEMPO–PSTY–TEMPO–≡ (Mn = 5350, PDI = 1.06,
−
6
3
1
1
0 mg, 5.61 × 10 mol), N3–PSTY–N3 (Mn = 4640, PDI =
−
6
Accessory Publication
.09, 26.04 mg, 5.61 × 10 mol), and PMDETA (1.94 mg,
−5
1
.12 × 10 mol) were placed in a 10 mL Schlenk flask and
ATR-FTIR and H NMR spectra are provided on the Journal’s
dissolved in toluene (0.7 mL). Oxygen was removed from
website.
I
the solution by purging with argon (15 min). Cu Br (1.61 mg,
−5
1
.12 × 10 mol) was then added under a positive argon flow.
Acknowledgements
◦
The reaction vessel was sealed and placed in an oil bath at 25 C
with stirring for 60 min. The reaction was sampled and analyzed
by SEC.
J.K. thanks the RACI Polymer Division for the SirTedTreloar Prize received
at PPC11 in Cairns. M.J.M. acknowledges financial support from an ARC
Discovery Projects (DP0987315) and receipt of an ARC Future Fellowship.

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J. Kulis et al.
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