Synthesis of neutral, water-soluble oligo-ethylene glycol-containing dendronized homo-and copolymers of generations 1, 1.5, 2, and 3

Article abstract of DOI:10.1021/ma5017192

Oligo-ethylene glycol-containing dendronized monomers MG1, MG1.5, MG2, and MG3 were synthesized in a particularly easy fashion on the gram scale involving only few steps. Their corresponding homopolymers (PG1, PG1.5, PG2, and PG3) and copolymers (PG1co2, PG1co3, and PG2co3) were synthesized via free radical polymerization. All the polymers are soluble in water and also in organic solvents such as DCM, CHCl₃, 1,4-dioxolane, DMF, and DMSO. Their glass transition temperatures (T_g) are in the range -68 °C < T_g < -48°C and thus rather low. All polymers show thermoresponsive behavior which was investigated by turbidity measurements. Interestingly, a 1:1 mixture of homopolymers PG1 and PG2 behaves identical with PG1 alone, while the collapse curve of copolymer PG1co2 is almost superimposable with that of PG2 alone. Thus, in the former case PG1 dominates the thermoresponsive behavior while in the latter this is done by the G2-dendrons in the copolymer. Finally, the polymer chains were visualized by AFM, confirming the rod-like behavior of these rigidified polymers.

Full text of DOI:10.1021/ma5017192

Article
pubs.acs.org/Macromolecules
Synthesis of Neutral, Water-Soluble Oligo−Ethylene Glycol-
Containing Dendronized Homo- and Copolymers of Generations 1,
.5, 2, and 3
1
Xiaoyu Sun, Jean-Pierre Lindner, Bernd Bruchmann, and A. Dieter Schlu
̈
ter*,†
†
,‡
§
§,‡
†
Institute of Polymers, Department of Materials, ETH Zurich, HCI J 541 Vladimir-Prelog-Weg 5, Ho
̈
nggerberg Campus, CH 8093
Zurich, Switzerland
‡
JONASJoint Research Network on Advanced Materials and SystemsThe European Post Doc Initiative of BASF and Academia,
Carl-Bosch-Strasse 38, 67056 Ludwigshafen, Germany
§
Advanced Materials and Systems Research, BASF SE, Carl-Bosch-Strasse 38, 67056 Ludwigshafen, Germany
S Supporting Information
*
ABSTRACT: Oligo-ethylene glycol-containing dendronized monomers
MG1, MG1.5, MG2, and MG3 were synthesized in a particularly easy
fashion on the gram scale involving only few steps. Their corresponding
homopolymers (PG1, PG1.5, PG2, and PG3) and copolymers (PG1co2,
PG1co3, and PG2co3) were synthesized via free radical polymerization. All
the polymers are soluble in water and also in organic solvents such as
DCM, CHCl , 1,4-dioxolane, DMF, and DMSO. Their glass transition
3
temperatures (T ) are in the range −68 °C < T < −48 °C and thus rather
g
g
low. All polymers show thermoresponsive behavior which was investigated
by turbidity measurements. Interestingly, a 1:1 mixture of homopolymers
PG1 and PG2 behaves identical with PG1 alone, while the collapse curve of copolymer PG1co2 is almost superimposable with
that of PG2 alone. Thus, in the former case PG1 dominates the thermoresponsive behavior while in the latter this is done by the
G2-dendrons in the copolymer. Finally, the polymer chains were visualized by AFM, confirming the rod-like behavior of these
rigidified polymers.
INTRODUCTION
groups as the peripheral functional groups which can be easily
converted into charged ammonium groups or carboxylates. In
both cases the resulting DPs are water-soluble; thus, the charges
shield the hydrophobic interior of the thick macromolecules
against the aqueous environment, very much as it is known for
micelles. Water-soluble polymers are attractive for many fields
of application including construction, agriculture, and pharma-
■
1
Dendronized polymers (DPs) carry dendritic units (dendrons)
at every repeat unit and by this have a tunable main chain cross-
2
sectional radius. This variable thickness is the key feature that
makes them differ from common linear polymers. The dense
substitution with dendrons not only increases the persistence
length of the main chain but also turns the main chain into an
object with an “interior” and a “surface” including countless
lateral functional groups on this “surface”. The reversibly
swellable interior of low generation DPs provides these unusual
macromolecules with a mode of responsivity that is absent in
conventional polymers. It potentially opens the way into
applications based upon persistence lengths, which are tunable
by the degree of swelling, but also offers novel transport
options by translocation of guest-loaded DPs through
nanopores. The numerous functional groups, which are the
terminal functional groups of the dendrons, have a radial
3
9
ceuticals. There is a growing demand for nontoxic and
4
biocompatible water-soluble polymers which needs to be served
by providing cheap, robust and synthetically scalable solutions.
Noncharged polymers are preferred because they do not cause
problems with cell lysis and also do not normally have a
complex aggregation behavior. Oligoethylene glycol (OEG)
and its variants proved to be valuable in this regard. Attachment
of OEG groups of different compositions is an often used
strategy to render otherwise hydrophobic polymers water-
5
6
10
soluble. There are even a few DPs, whose entire branch work
11
or part of it is based on OEG units. Also these polymers are
probability distribution and do therefore not all reside on the
12
7
water-soluble and furthermore show thermoresponsivity.
Most DPs are homopolymers even though an increasing
“
surface”. Those that happen to connect the macromolecule to
the outside world determine the solubility behavior but also,
e.g., the adhesion of DPs to solid substrates. This was used to
immobilize enzymes on simple glass slide with the help of
13
number of blockcopolymers and particularly alternating
8
DPs.
Received: August 22, 2014
Revised: October 6, 2014
Most DPs are neutral and soluble in organic solvents. The
working horses from our laboratory carry Boc-protected amine
©
XXXX American Chemical Society
A
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 1. Chemical structures of all synthesized macromonomers and some of the new homo- and copolymers. The hydrogen atoms nearest to the
main chains are denoted as A.
1
4
copolymers have been reported. Recently there was also a
report on a copolymer for which the authors claim a gradient
the intrinsic nature of DPs as exemplified, e.g. by their behavior
in melt. Second, DPs are “thick” and can be viewed as
molecular cylinders. While the homopolymers typically have a
smooth cylindrical “surface”, copolymers using monomers with
dendrons of different generation may open the possibility to
create “corrugated cylinders” (Figure 1). We consider this an
attractive option for expanding topology reminiscent of
colloidal molecules. Further, we report the lower critical
solution temperatures (LCSTs) of both homo- and copolymers
and address the question which dendron in a copolymer
determines the turbidity behavior. Finally, we provide AFM
tapping mode images of some of the polymers synthesized
while adsorbed as single chain entities on mica substrate.
1
4g
structure. Furthermore, our laboratory has recently reported
copolymerization parameters of the first generation OEG-based
macromonomer MG1 (Figure 1) with styrene and different
1
5a
acrylates.
We here report the syntheses of monomers MG1, MG1.5,
MG2, and MG3, which are either modified to known
17
1
5
procedures under efficiency aspects (MG1, MG1.5) or new
MG2 and MG3). These monomers were converted into their
(
homopolymers through free radical polymerization and also
used to create the random copolymers PG1co2, PG1co3, and
PG2co3. Besides the more general motivation given above,
there were two further concrete aspects that made us
synthesizing these novel polymers. First, the rheological
behavior of our prototype DPs points toward an interaction
between these polymers in the melt that could be the result of
interchain hydrogen bond formation and/or π,π-stacking. To
prevent this from happening, DPs of the kind PG1, PG1.5,
PG2, and PG3 are ideal candidates because they can obviously
not undergo such interaction. Thus, these novel DPs are
expected to provide us with a more comprehensive picture of
RESULTS AND DISCUSSION
■
The synthetic routes to the dendrons 4, 5, 8, and 10 and the
corresponding macromonomers MG1, MG1.5, MG2, and
MG3 are delineated in Scheme 1. All procedures are based on
the cheap commercial starting materials epichlorohydrin 1 and
ethylene glycol monomethylester 2. MG1 had been published
earlier but was then synthesized in a one-pot procedure from 1
and 2 which−given the manifold possibilities for nucleophilic
16
B
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
a
Scheme 1. Reagents and Conditions
a
Key: (a) 1:2 = 1:1, NaH, THF, room temperature 16 h, then 65 °C, 4 h; (b) 3:1 = 1:2, NaOH/H O, 55 °C, overnight, 4 (53%), 5 (30%); (c)
2
MAC, DMAP, TEA, DCM, 0−25 °C, overnight, 86%; (d) 1:4 = 1:1, NaH, THF, room temperature 16 h, then 65 °C, 4 h; (e) 6:2 = 1:2, NaOH/
H O, 50 °C, overnight, 85%; (f) NaH, [15]-crown-6, KI, THF (yields for 7 and 9, respectively: 84% and 85%); (g) O , DCM/MeOH, −78 °C; (h)
2
3
NaBH , DCM/MeOH, −78 °C to room temperature (yields for 8 and 10, respectively: 95% and 91%); (i) MAA, DMAP, DIEA, DCM, 0−40°C,
4
overnight (yields for MG2 and MG3, respectively: 82% and 85%).
ring-opening of 1 and the other epoxides involved−resulted in
complex mixtures of products requiring nontrivial purifications
The incomplete dendron 5 used for the synthesis of MG1.5
can either be obtained as the side product of the synthesis of 4
or be made selectively by the reaction of 1 with dendron 4 to
furnish epoxide 6 which is then ring-opened with 2.
15a
leading to a low yield (22%). This is why we aimed at first
performing the nucleophilic substitution of 2 selectively at the
chlorinated carbon of 1, before then reacting the obtained
epoxide 3 further with 2. Intermediate 3 was in fact obtained as
the sole product when 1 and 2 were reacted with one another
in a 1:1 ratio in THF using NaH as the base. Compound 3
could either be used as obtained or after distillation. Further
reaction with 2 in a ratio 3:2 = 1:2 afforded a mixture of
dendrons 4 and 5 whereby 4 was the main product (yields: 4,
With sufficient dendron 4 in hand, we started synthesis of
MG2 and MG3 following a previously reported procedure
which was developed for structurally related non-OEG-
1
8,19
dendrons and proved to be very potent in our case.
First
the commercially available methallyl dichloride (MDC) was
20
etherified with 4 at both chloromethyl groups to give the
geminally disubstituted olefin 7. This proved to be an efficient
process when performed with NaH (1.5 equiv per OH) and
catalytic amounts of KI, [15]crown-5, and [18]-crown-6 in dry
THF. Flash chromatography afforded pure 7 in 84% on the
12.5 g scale. Ozonolysis with subsequent reductive work-up
53%, 5, 30%). The compounds were easily separated by
distilling off the lighter product and subjecting the remainder to
a simple chromatography. Both dendrons were converted with
MAC into the monomers MG1 and MG1.5, respectively, in
high yields (>85%).
(NaBH ) gave the second generation dendron 8 in excellent
4
yield (95%). This dendron was either directly converted into
C
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 1. Homo- and Copolymerizations: Conditions and Results
a
c
polymerization conditions
GPC
b
monomer, amt
(mmol)
[AIBN]
solvent, amt
(mL)
[monomer]
yield
Mn
1
d
entry
(mol %)
(mol L−
)
time (h)
17
(%)
(kDa)
PDI
DPn
1
2
3
4
5
6
7
8
9
MG1, 0.60
MG1, 0.60
MG1, 0.60
MG1, 3.60
MG1.5, 0.40
MG2, 0.30
MG2, 0.20
MG3, 0.084
MG3, 0.10
MG1, 0.10
MG2, 0.10
MG1, 0.15
MG2, 0.15
MG1, 0.10
MG2, 0.10
MG1, 0.05
MG3, 0.05
MG1, 0.10
MG3, 0.10
MG2, 0.05
MG3, 0.05
MG2, 0.10
MG3, 0.10
0.1
0.1
0.1
0.1
0.2
0.1
0.2
0.5
0.5
0.2
toluene, 0.5
toluene, 0.1
DMF, 0.1
1.2
6.0
6.0
1.2
2.0
6.0
2.0
1.68
2.0
2.0
90
18
97
80
86
86
93
44
37
46
210
639
118
280
646
144
219
66
4.3
7.3
4.1
2.8
5.0
3.4
3.5
2.6
2.3
3.4
760
2310
425
1016
1584
266
406
62
5, 17 (gel)
17
17
17
5
toluene, 3
toluene, 0.2
toluene, 0.05
toluene, 0.1
toluene, 0.05
toluene, 0.05
toluene, 0.1
17
17
17
3
57
54
e
10
11
12
13
14
15
16
446
RUG1, 751
RUG2, 442 (1.7:1)
RUG1, 206
0.1
0.2
0.2
0.2
0.2
0.2
toluene, 0.05
toluene, 0.1
toluene, 0.05
toluene, 0.1
toluene, 0.05
toluene, 0.1
6.0
2.0
2.0
2.0
2.0
2.0
5
17
3
73
86
27
75
42
75
168
133
323
147
316
317
34
RUG2, 206 (1:1)
RUG1, 163
8.1
3.0
4.1
2.5
4.9
RUG2, 163 (1:1)
RUG1, 371
RUG3, 206 (1.8:1)
RUG1, 182
17
2
RUG3, 91 (2:1)
RUG2, 343
RUG3, 122 (2.8:1)
RUG2, 295
17
RUG3, 147 (2:1)
a
b
c
All polymerizations were carried out at 60 °C. Yield: isolated by precipitation. All GPC measurements were done with DMF (1% LiBr) as eluent
d
e
at 45 °C. DP = number-average degree of polymerization. RUG1 stands for repeat unit with first generation dendron.
n
1
Figure 2. H NMR spectra of the synthesized homo- (a) and copolymers (b) in CDCl at 25 °C. The signals of the protons, HA, absorb between δ =
3
4
.62 and 4.85 ppm and can be differentiated for the different generations except for PG2co3. GPC elution curves (DMF; at 45 °C) of the homo- (c)
and copolymers (d) synthesized in this study. In part d for each copolymer, the curves at low (dashed line) and high conversion (full line) are given.
The curves are largely monomodal except for PG1.5 (red line in part c) and for PG1co2 at high conversion. For a discussion, see text.
monomer MG2 or subjected to the same etherification/
ozonolysis procedure to first furnish the olefin 9 and then the
third generation dendron 10. Reaction of 10 with MAA gave
monomer MG3. Monomers MG2 and MG3 were synthesized
both on the 0.9 g-scale. The new monomers were obtained in
high purity (see Supporting Information for spectra).
All polymerizations were performed on the 100 mg to 1 g
scale of the respective monomers and with AIBN as initiator at
60 °C whereby all initial solutions were fully clear and
D
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
transparent. The results are compiled in Table 1. Relevant
NMR spectra and GPC elution curves are shown in Figure 2.
Entries 1−9 of Table 1 refer to homopolymerizations and
entries 10−16 to copolymerizations. The best conditions
regarding achievable molar mass and prevention of gel
formation were first explored with MG1. Concentration had
a strong effect. As the comparison of entries 1 and 2 shows,
polymerizations at 6 mol/L of monomer in toluene had to be
quenched already after 5 h to prevent gel formation, while at
(Figure 2d) and the very high PDI = 34. This bimodality and
extreme distribution are likely due to MG2 homopolymeriza-
tion competing with regular copolymerization at high
conversion. Additionally, because of the high concentration
applied, chain transfer effects may compete with linear
polymerization. For the monomer combination MG1 and
MG3 the differences in incorporation rate do not seem to
depend much on conversion which, given the even larger
molecular weight differences between these monomers and
MG1 and MG2 is unexpected. For the combination MG2 and
MG3 the situation is back to “normal”. While at lower
conversion RUG2:RUG3 = 2.8:1 (entry 15) at higher
conversion RUG2:RUG3 = 2:1 was found (entry 16). Despite
the uncertainty with regard to the monomer combination MG1
and MG3, taking all homo- and copolymerizations together, it
is safe to conclude the reactivity relation: MG1> MG2 > MG3.
All the polymers are soluble in water and in organic solvents
1.2 mol/L the polymerization could be run for 17 h without
problems. When quenched after 5 h (at 6 mol/L) yields were
poor and the material had an unattractively broad PDI = 7.3
(entry 2). This broad dispersity is likely due to branching, the
onset of cross-linking. While there are no unequivocal results
available yet, we consider it reasonable to assume that the α-
CH positions (to oxygen) in the macromonomers and the
corresponding polymers can undergo chain transfer and
therefore can cause cross-linking. When switching to DMF as
solvent, gel formation could be suppressed even at high
conversion but the molar masses were relatively low. The
largest scale polymerization of MG1 (1 g) was therefore
performed in toluene and at low monomer concentration
such as DCM, CHCl , 1,4-dioxolane, DMF and DMSO. They
3
are insoluble in n-hexane which provided an opportunity for
purification by precipitation. All polymers are sticky solids in
line with their rather low glass transition temperatures (T
which range from −68 °C < T < −48 °C (Table 2). For
)
g
g
(entry 4). Low monomer concentrations proved advantageous
also in the other hompolymerizations (entries 5−9). Yields
referring to precipitated and high vacuum-dried products were
Table 2. Number Average Molecular Weight and Glass
Transition Temperatures (T ) of all Synthesized Homo- and
g
8
0
0% and above except for MG3. At initiator concentrations of
.1−0.2 mol % this monomer did not polymerize at all and at a
Copolymers
polymer
M (kDa)
Tg (°C)
n
concentration of 0.5 mol % yields could not be pushed beyond
around 40%. As is known from other macromonomer
polymerizations, chain lengths decreases with increasing
monomer mass, so also here. While for MG1 and MG1.5
chain lengths were about 1000 and higher (DP ), for MG2 they
dropped to a few hundred to arrive at a few tens for MG3. The
GPC elution curves of all polymers are monomodal (Figure 2c)
except for PG1.5. The reason for the broadening in this case is
not known. The proton NMR spectra of all homopolymers can
be easily differentiated by the chemical shift of the proton
PG1
280
200
219
67
−48.5
−55.6
−68.5
−68.4
−57.3
−65.9
−68.4
2
1
PG1.5
PG2
PG3
n
PG1co2
PG1co3
PG2co3
168
147
317
comparison, the T ’s of tri(oxyethylene) glycol-based poly-
g
A
nearest to the backbone, H (Figure 2a). The shifts gradually
methacrylates PG1(OH) and PG2(OH) are T = −45 °C and
g
move upfield with increasing dendron generation (δ in ppm for
PG1, 4.85; PG1.5, 4.77; PG2, 4.70; PG3, 4.64) (Figure 2a).
This feature proved useful in case of the copolymers where the
comonomer composition could be determined in two of the
three cases by NMR integration. All homopolymers gave
satisfactory data from combustion analysis.
The copolymerizations were performed for the three possible
combinations between MG1, MG2 and MG3 at molar feed
ratios of 1:1. They were run to relatively low and high
conversion in order to obtain qualitative information about the
initial and the overall monomer incorporation. Co-monomer
composition was determined by NMR integration for PG1co2
and PG1co3 and by weighing back recovered monomer for
PG2co3. In the former case the chemical shift differences of the
protons HA of the homopolymers also showed in the
copolymers, which allowed an easy analysis (Figure 2b). For
PG1co2, the ratio of G1 to G2 repeat units was RUG1: RUG2
T = −40 °C, respectively, and of their methoxy-terminated
g
1
1a,d
counterparts T < −80 °C.
g
Furthermore, the thermoresponsive behavior of the homo-
and copolymers was investigated by turbidity measurements
using a λ = 500 nm light source. In general the transitions are
sharp and have negligible hysteresis (Figure 3; Δ(PG1) = 0.2,
Δ(PG2) = 0.4) as is commonly observed for OEG-based DPs.
Also the LCSTs increase with generation indicating the
increasing hydrophilicity of the higher generation DPs. This
increase is even more pronounced than in other DP cases. The
fact that PG3 does not follow this expectation (Figure 3a) is
due to the rather short main chain of the sample (Table 1, entry
8), rendering its LCST to still be molar mass dependent. The
turbidity curves of the copolymers deserve a few more
comments. It was of interest to see whether the thermores-
ponsive behavior of a copolymer would be dominated by either
of its two different dendrons. This investigation was started by
measuring a 1:1 mixture of the homopolymers PG1 and PG2.
These mixtures turned out to behave identical with PG1 alone,
proving that both polymers act independently from one
another. In contrast, the heating and cooling curves of
PG1co2 (Table 1, entry 10; Figure 3b) are almost super-
imposable with that of PG2 (Figure 3a). Thus, the G2
dendrons of PG1co2 are the ones that determine the behavior,
suggesting in a first approximation that the G1 dendrons are
22
=
1.7:1 for the low conversion case (entry 10). Prolonging
reaction time to 17 h (entry 12) or performing copolymeriza-
tion at high concentration for 5 h (entry 11), resulted in high
conversions and a ratio RUG1: RUG2 = 1:1 indicating that
MG1 has the higher reactivity than MG2. This is what one
would expect based on the considerably lower molecular weight
15a
of MG1 compared to MG2.
conversions also resulted in a reproducible bimodal distribution
For entry 11 these high
E
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
basically buried within the molecular structure. Looking into
the other two copolymers, however, it becomes evident that the
effect is not of general validity. The matter is further
complicated by the fact that the PG3 samples have short
main chains only. On the basis of the observation with other
thermoresponsive DPs we tentatively assume that LCSTPG3
>
LCSTPG2 in contrast to what Figure 3a suggests. This
assumption is further supported by the transmittance curve of
PG1co3 which lies above 45 °C and thus well above LCSTPG1
.
Thus, also in this copolymer the larger dendron controls the
thermoresponsive behavior. This is contrasted, however, by
copolymer PG2co3 which exhibits heating and cooling curves
very similar to PG2 suggesting that in this case, and contrary to
the other two cases, the lower generation dendron largely
controls the behavior. It seems that we have discovered a
peculiar effect of molecular structure on thermoresponsivity,
which requires more in depth studies on sequence and
copolymer composition before a full understanding can be
gained.
Finally, the DPs were adsorbed on mica and directly imaged
by tapping mode AFM (Figures 4a−c). Single “well-behaved”
chains are clearly visible for PG2 (Figure 4a) and the
coprepared chains of PG1, PG2 and PG3 (Figure 4b). PG1
coils up into islands, while PG2 chains are more extended. PG3
chains appear as dots because of their short chain length. The
image in Figure 4b can be used to determine height differences
between the three samples which amount to roughly 0.5 nm
between PG1 and PG2 and 0.7 nm between PG2 and PG3.
These height differences are smaller than those observed for
2
our working horse DP series. We refrain from providing h
AFM
values for the different DPs because they strongly depend on
exogenic factors such as humidity and, thus, vary from
measurement to measurement. This can nicely be seen by
comparing Figures 4a and 4b which both contain PG2 chains.
Interestingly, while the heights along the contours of the
homopolymers were essentially constant, those of the
copolymer PG1co3 varies quite a bit. This can already be
seen from the height profile provided in Figure 4c, where the
Figure 3. Determination of lower critical solution temperatures
(
LCST): Plots of transmittance vs temperature for 0.25 wt % aqueous
solutions of (a) PG1 (Table 1, entry 4), PG2 (entry 7), and PG3
entry 9). (b) PG1co2 (entry 10), PG1co3 (entry 13), PG2co3 (entry
5) and a 1:1 mixture of PG1 (entry 4) and PG2 (entry 7). Heating
and cooling rate: 0.2 °C/min.
(
1
Figure 4. AFM height images of (a) PG2 (Table 1, entry 7), (b) a mixture of PG1 (Table 1, entry 4), PG2 (Table 1, entry 7), and PG3 (Table 1,
entry 8), and (c)PG1co3 (Table 1, entry 13) . Samples were prepared from DCM solution [2 mg/L (a and c) and (0.6 mg PG1 + 0.6 mg PG2 + 0.6
mg PG3)/L (b)] by spin coating (2000 rpm) on mica, and air-dried for 4 h before AFM imaging. The height scale of these images is not the same in
order to obtain good contrast, and therefore, the color of the images cannot be directly compared. The Z scale is 10 nm for parts a and b and 6 nm
for part c.
F
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
hAFM values vary strongly depending on where the analysis is
performed. This is a first indication of a corrugated surface of
these objects. Higher resolution images are required to establish
this point more convincingly.
Scanning probe microscope (from Digital Instruments, San Diego,
CA) operated in the tapping mode with an “E” scanner (scan range 10
μm × 10 μm) and operated in the tapping mode at room temperature
in air. Olympus silicon OMCL-AC160TS cantilevers (from Atomic
Force F&E GmbH, Mannheim, Germany) were used with a resonance
frequency between 200 and 400 kHz and a spring constant around 42
N/m. The samples were prepared by spin-coating (2000 rpm) the
polymer solution onto freshly cleaved mica (from PLANO W. Plannet
GmbH, Wetzlar, Germany). UV/visturbidity measurements were
carried out for the lower critical solution temperature (LCST)
determination on a Varian Cary 100 Bio UV/vis spectrophotometer
equipped with a thermostatically regulated bath. Solutions of the
polymers in deionized water were filtered with a 0.45 μm filter before
adding into a cuvette (path length 1 cm), which was placed in the
CONCLUSIONS
■
As judged by number of steps, overall yields, and total
experimental effort, we have presented the arguably easiest
synthetic access to a variety of water-soluble, neutral DPs with
generations up to three based on the corresponding macro-
monomers MG1, MG1.5, MG2, and MG3. These monomers
were prepared as analytically pure materials on the several gram
scale. This variety of DPs comprises both homo- and
‑
1
spectrophotometer and heated or cooled at a rate of 0.2 °C min . The
absorptions of the solution at λ = 500 nm were recorded every minute.
Syntheses. 2,5,9,12-Tetraoxatridecan-7-ol (4). NaH (60% in
mineral oil) (40.00 g, 1.00 mol) was rinsed with toluene and added as
(presumably random) copolymers. Copolymer compositions
were determined by NMR spectroscopy and weighing of
unconsumed monomers, respectively. The copolymers differ
from dendronized homopolymers because their “surface”
should not be smooth and near cylindrical but rather
corrugated. A first indication for the correctness of this
expectation was obtained from the AFM image of copolymer
PG1co3. All polymers described are thermoresponsive, where-
by the generation dependence of LCST is stronger than in
other OEG-based DPs. While the thermoresponsivity of the
copolymers is fully reproducible, there does not seem to be a
straightforward interpretation of where the transition is to be
expected solely based on the two different dendrons involved in
each of the three cases.
dry powder to dry THF (850.0 mL) under N atmosphere. Ethylene
2
glycol monomethyl ether (78.85 mL, 1.00 mol) was then added and
stirred for 2 h. Thereafter epichlorohydrine (0.96 mol) was added, and
the reaction mixture was stirred for 16 h at room temperature, then
heated to 65 °C for 4 h. The reaction mixture was filtered through
Celite and concentrated under reduced pressure to afford the desired
crude intermediate 3, which was used without further purification.
Ethylene glycol monomethyl ether (151.4 mL, 1.92 mol) was added to
an aqueous solution of NaOH (19 mol/L; 1.0 equiv), then heated to
5
5 °C and 3 was added. The reaction mixture was stirred overnight at
this temperature and then extracted with DCM (3 × 200 mL). The
combined organic phases were dried over MgSO and the solvent was
4
evaporated to afford the crude products. Distillation under vacuum
afforded the desired 4 as colorless oil (106.0 g, 53%). The residue in
the flask was purified by flash chromatography with hexane/ethyl
EXPERIMENTAL SECTION
Materials. Azobis(isobutyronitrile) (AIBN) was recrystallized
twice from methanol. Tetrahydrofuran (THF) was refluxed over
lithium aluminum hydride (LAH) and dichloromethane (DCM)
■
acetate (2:1 to 1:2) to give alcohol 5 as pale yellow oil (24.62 g, 30%).
1
H NMR (300 MHz, CDCl ): data of 4, 4.03−3.94 (m, 1H), 3.67−
3
3.46 (m, 12H), 3.37 (s, 6H); data of 5, 3.92−3.88 (m, 1H), 3.71−3.66
13
distilled from CaH for drying. Other reagents and solvents were
(m, 2H), 3.60−3.46 (m, 20H), 3.32 (m, 9H). C NMR (75 MHz,
2
purchased at reagent grade and used without further purification. All
reactions were run under a nitrogen atmosphere. Macherey-Nagel
precoated TLC plates (silica gel 60G/UV254, 0.25 mm) were used for
thin-layer chromatography (TLC) analysis. Silica gel 60 M (Macherey-
Nagel, 0.04−0.063 mm, 230−400 mesh) was used as the stationary
phase for column chromatography. Further abbreviations: DIEA, N,N-
diisopropylethylamine; DMAP, 4-dimethylaminopyridine; MAA,
methacrylic anhydride; MAC, methacryloyl chloride; TEA, triethyl-
amine.
CDCl ): data of 4 were reported in ref 19; data of 5, 78.8, 72.4, 71.8,
3
+
71.5, 71.4, 70.7, 69.6, 58.9. HRMS (ESI): m/z = 341.2171 ([M + H] ,
C H O ; calcd, 341.2170).
+
15
33
8
2,5,9,12-Tetraoxatridecan-7-yl Methacrylate (MG1). Esterifica-
tion Procedure (A) According to Reference 15a. Dendron 4 (5.00 g,
24.02 mmol), triethylamine (10.00 mL, 3.0 equiv), and DMAP (293
mg, 0.1 equiv) were dissolved in DCM (150.00 mL). Methacryloyl
chloride (6.92 mL, 3 equiv) was slowly added at 0 °C. The reaction
was allowed to warm to room temperature and stirred overnight. The
1
13
Measurements. H and C NMR spectra were recorded on a
mixture was then quenched with saturated aqueous NaHCO
extracted with DCM. The combined organic phases were dried over
MgSO and the solvent was evaporated to afford the crude product.
3
and
1
13
Bruker AV 300 ( H, 300 MHz; C, 75 MHz) spectrometer. Chemical
shifts are reported as δ values (ppm) and were calibrated according to
internal standard CHCl3 (7.26 ppm). High-resolution ESI-Q-TOF-
MS analyses (solvent, DCM/MeOH; ion polarity, positive; set
capillary, 4500 V) were performed on Bruker Daltonics maXis by
4
Purification by flash chromatography with hexane/ethyl acetate (2:1)
1
as eluent afforded MG1 as colorless oil (5.71 g, 86%). H NMR (200
MHz, CDCl ): 6.12 (s, 1H); 5.57 (t, 1.6 Hz, 1H); 5.23−5.18 (m, 1H);
3
the MS service of the Laboratorium fu
Zurich. Elemental analyses were performed by the Mikrolabor of the
Laboratorium fur Organische Chemie, ETH Zurich. Gel permeation
̈
r Organische Chemie, ETH
3.71−3.49 (m, 12H); 3.36 (s, 6H); 1.94 (s, 3H).
̈
2-((2,5,9,12-Tetraoxatridecan-7-yloxy)methyl)oxirane (6). To a
three-necked flask charged with NaH (60% in mineral oil, 0.40 g, 10
̈
̈
chromatography (GPC) measurements were carried out by using a
PL-GPC 220 instrument equipped with refractive index (RI), viscosity,
and light scattering (LS; 15° and 90° angles) detectors and a 2 × PL-
mmol, 1.0 equiv) and freshly distilled, dry THF (10.00 mL) under N
2
atmosphere was added a solution of dendron 4 (2.08 g, 10.00 mmol)
in THF (2.00 mL). After the mixture had been stirred for 2 h at room
temperature, epichlorohydrine (1.00 g, 10.50 mmol, 1.05 equiv.,) was
added to the solution via syringe. The resulting mixture was stirred for
16 h at room temperature and then heated to 65 °C for 4 h. After
cooling to room temperature the reaction was quenched with aqueous
−1
Gel Mix-B LS column set (2 × 30 cm) using DMF with LiBr (1 g L )
as the eluent at 45 °C. Universal calibration was performed with
poly(methyl methacrylate) standards in the range of M = 2680−3 900
p
0
00 (Polymer Laboratories Ltd., U.K.). Differential scanning
calorimetry (DSC) measurements were performed using the DSC
Q1000 differential scanning calorimeter from TA Instruments in a
temperature range of −95 ∼ +100 °C with a heating rate of 10 °C
NH Cl followed by extraction with DCM (3 × 50 mL). The combined
4
organic phases were dried over MgSO4 and the solvent was
evaporated. The crude material was then purified by flash
chromatography with hexane/ethyl acetate (2:1) to give the desired
−
1
min . Samples of a total weight ranging between 3 and 10 mg were
closed into aluminum pans of 40 μL, covered by a holed cap, and
analyzed under a nitrogen atmosphere. The glass transition temper-
product 6 as colorless oil (2.30 g, 88%).
1
H NMR (300 MHz, CDCl ): 3.88 (dd, 3.3 11.7 Hz, 1H); 3.76−
3
ature (T ) was taken in the second heating run. The AFM
3.72 (m, 2H); 3.63−3.53 (m, 12H); 3.37 (s, 6 H); 3.17−3.14 (m,
1H); 2.78 (dd, 3.9, 4.8 Hz, 1H); 2.62 (dd, 2.7, 5.1 Hz, 1H). C NMR
g
1
3
measurements were carried out on a Nanoscope IIIa Multi Mode
G
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
(
75 MHz, CDCl ): 78.6; 72.0; 71.6; 71.5; 71.4; 70.9; 59.1; 51.1; 44.6.
CDCl ): 6.11 (s, 1H); 5.55 (t, 1.5 Hz, 1H); 5.16−5.08 (m, 1H); 3.84−
3
3
+
+
HRMS (ESI): 265.1648 ([M + H] , C H O ; calcd, 265.1646
3.49 (m, 30H); 3.36 (s, 12H); 1.93 (s, 3H).
12
25
6
(
error, 0.7 ppm)).
-((2-Methoxyethoxy)methyl)-2,5,8,12,15-pentaoxahexadecan-
0-ol (5). Ethylene glycol monomethyl ether (0.79 mL, 2.0 equiv.,
0.00 mmol) was added to an aqueous solution of NaOH (19 mol/L;
.0 equiv) which was then heated to 55 °C before compound 6 (1.32
10,16-Bis((2,5,9,12-tetraoxatridecan-7-yloxy)methyl)-7,19-bis((2-
methoxyethoxy)methyl)-13-methylene-2,5,8,11,15,18,21,24-oc-
taoxapentacosane (9). This was prepared according to the
etherification procedure (B) from 8 (9.04 g, 19.2 mmol) and MDC
7
1
1
2
(1.20 g, 9.60 mmol). After 4 d, the reaction was quenched and purified
by flash chromatography with ethyl acetate/acetone (2:1−1:1, v/v) as
g, 5.00 mmol) was added. The reaction mixture was stirred overnight
at 55 °C and then extracted with DCM (3 × 40 mL). The combined
organic phases were dried over MgSO and the solvent was evaporated
to yield crude material, which was purified by flash chromatography
with hexane/ethyl acetate (2:1) to give dendron 5 as colorless oil (1.45
g, 85%).
1
eluent to give compound 9 as pale yellow oil (8.14 g, 85%). H NMR
(
300 MHz, CDCl ): 5.14 (s, 2H); 4.07 (s, 4H); 3.70−3.47 (m, 62H);
3
4
3
7
+
.34 (s, 24H). 13C NMR (75 MHz, CDCl ): 143.5; 113.3; 78.6; 77.6;
3
1.9; 71.3; 71.2; 70.8; 70.7; 70.2; 59.0. HRMS (ESI): 1014.6403 ([M
+
+
NH ] , C H NO ; calcd, 1014.6419 (error, −1.5 ppm)).
4
46 96
22
1
0,16-Bis((2,5,9,12-tetraoxatridecan-7-yloxy)methyl)-7,19-bis((2-
methoxyethoxy)methyl)-2,5,8,11,15,18,21,24-octaoxapentacosan-
3-ol (10). According to the ozonolysis/reduction procedure (C),
7
-((2-Methoxyethoxy)methyl)-2,5,8,12,15-pentaoxahexadecan-
1
0-yl Methacrylate (MG1.5). According to the esterification
1
procedure A, MG1.5 (0.90 g) was prepared from dendron 5 (0.85
g, 2.5 mmol) in 90% yield as colorless oil. H NMR (300 MHz,
CDCl ): 6.11 (s, 1H); 5.55 (t, 1.2 Hz, 1H); 5.18−5.14 (m, 1H); 3.80−
3
1
dendron 10 (8.01 g) was prepared from 9 (8.73 g, 8.76 mmol) as a
1
pale yellow oil (91%). H NMR (300 MHz, CDCl ): 3.90−3.82 (m,
3
3
13
1
H); 3.75−3.50 (m, 67H); 3.36 (s, 24H). C NMR (75 MHz,
CDCl ): 79.2; 78.7; 72.2; 72.0; 71.3; 71.2; 70.8; 70.5; 69.8; 59.1.
HRMS (ESI): 1018.6349 ([M + NH ] , C H NO ; calcd,
.48 (m, 21H); 3.35 (s, 9H); 1.93 (s, 3H).
3
7
,13-Bis((2-methoxyethoxy)methyl)-10-methylene-
+
+
4
45 96
23
2
,5,8,12,15,18-hexaoxanonadecane (7). Etherification Procedure
1
018.6368 (error, 1.8 ppm)).
0,16-Bis((2,5,9,12-tetraoxatridecan-7-yloxy)methyl)-7,19-bis((2-
methoxyethoxy)methyl)-2,5,8,11,15,18,21,24-octaoxapentacosan-
3-yl methacrylate (MG3). According to the esterification procedure
D) MG3 (0.91 g) was prepared from dendron 10 (1.00 g, 1.0 mmol)
(
B). To a suspension of NaH (60% in mineral oil, 3.78 g, 1.5 equiv. per
1
OH) and [15]-crown-5 (694 mg, 10 mol %) in freshly distilled, dry
THF (40.0 mL) under N atmosphere a solution of dendron 4 (13.1 g,
2
1
(
2
.0 equiv., 63.0 mmol) in THF (20.0 mL) was added. After the
mixture had been stirred for 2 h at 40 °C, KI (523 mg, 10 mol %),
18]-crown-6 (833 mg, 10 mol %) and MDC (3.94 g, 31.5 mmol)
1
as a pale yellow oil (85%). H NMR (300 MHz, CDCl ): 6.10 (s, 1H);
3
[
5
.54 (t, 1.5 Hz, 1H); 5.10−5.07 (m, 1H); 3.76−3.49 (m, 67H); 3.36
dissolved in THF (10.00 mL) were added to the solution. The
reaction mixture was stirred under reflux for 4 d, then cooled to room
temperature and quenched with saturated aqueous NH Cl. Extraction
with DCM (3 × 200 mL). The combined organic phases were dried
over MgSO and the solvent was evaporated to afford a crude material
which was further purified by flash chromatography with hexane/ethyl
acetate (2:1 to 1:1) to give the desired compound 7 as a pale yellow oil
13
(s, 24H); 1.93 (s, 3H); C NMR (75 MHz, CDCl ): 166.7; 136.5;
3
1
25.5; 79.0; 78.6; 72.9; 71.9; 71.2; 70.8; 70.3; 69.1; 59.0; 18.4. HRMS
+
+
4
(ESI): 1086.6614 ([M + NH ] , C H100NO24 ; calcd, 1086.6630
4 49
(error, −1.5 ppm)).
4
General Procedure for Polymerization (E). AIBN solution of
toluene or DMF with the concentration specified in Table 1 was
freshly prepared in advance. The required amount of the monomer
was added into a Schlenk tube, then the required AIBN solution was
added via a syringe. The reaction mixture was thoroughly
deoxygenated by several freeze-pump-thaw cycles and then stirred at
60 °C for the desired time. After cooling to room temperature, the
polymer was dissolved in DCM and purified by precipitation from n-
hexane.
1
(
12.5 g, 84%). H NMR (300 MHz, CDCl ): 5.16 (s, 2H); 4.13 (s,
3
13
4
H); 3.66−3.49 (m, 26H); 3.35 (s, 12H). C NMR (75 MHz,
CDCl ): 143.4; 114.0; 77.20; 72.0; 71.3; 70.8; 59.1. HRMS (ESI):
4
ppm)).
3
+
+
10
91.2819([M + Na] , C H NaO ; calc. 491.2827 (err., −1.5
22
44
7
,13-Bis((2-methoxyethoxy)methyl)-2,5,8,12,15,18-hexaoxano-
nadecan-10-ol (8). Ozonolysis/Reduction procedure (C). To a chilled
solution of 7 (10.00 g, 21.35 mmol) in DCM (150.0 mL)/ MeOH
According to general procedure for polymerization (E) from MG1
(1.00 g, 3.6 mmol), AIBN (0.1 mol %) and toluene (3.00 mL),
(
22.0 mL) (−78 °C) was bubbled O . After the mixture had turned
3
polymerization for 17 h afforded PG1 as a colorless sticky solid (0.80
1
light blue, ozonolysis was stopped and the ozone removed by letting
O or N pass through the solution. NaBH (1.21 g, 1.5 equiv., 32.0
g, 80%). H NMR (300 MHz, CDCl ): 4.85 (br., 1H); 3.59−3.51 (m,
3
1
3
2
2
4
); 3.36 (s, 6H); 1.82 (br., 1.6H); 1.05−0.93 (m, 2.6H). C NMR
75 MHz, CDCl ): 71.9; 70.7; 68.8; 59.0. Anal. Calcd (%) for
C H O ) (276.33) : C, 56.51; H, 8.75. Found: C, 56.32; H,
.97.PG1.5
12H
mmol) was added to the reaction mixture at −78 °C and the mixture
was then allowed to slowly warm to room temperature before being
stirred overnight. The reaction was quenched with 3 mL saturated
aqueous NH Cl solution and diluted with DCM, dried over MgSO ,
filtered, and concentrated in vacuum. The residue was purified by flash
chromatography with hexane/ethyl acetate (1:2) to afford compound
8
3
(
(
8
3
13
24
6
n
n
4
4
According to general procedure for polymerization (E) from MG1.5
(163.3 mg, 0.40 mmol), AIBN (0.2 mol %) and toluene (0.20 mL),
polymerization for 17 h afforded PG1.5 as a colorless sticky solid (140
1
1
as a colorless oil (9.58 g, 95%). H NMR (300 MHz, CDCl ): 3.94−
mg, 86%). H NMR (300 MHz, CDCl ): 4.77 (br., 1H); 3.84−3.43
3
3
13
13
.86 (m, 1H); 3.72−3.48 (m, 31H); 3.36 (s, 12H); C NMR (75
(m, 21H); 3.35 (s, 9H); 1.83 (br., 1.5H); 1.00−0.89 (m, 2.6H).
NMR (75 MHz, CDCl ): 78.6; 72.0; 71.0; 70.7; 70.6; 59.0. Anal.
C
MHz, CDCl ): 78.8; 72.2; 72.0; 71.9; 70.8; 69.8; 59.1. HRMS (ESI):
4
3
3
+
+
11
73.2955([M + H] , C H NaO ; calcd, 473.2956 (error, 0.2
Calcd (%) for (C H O ) (408.49) : C, 55.87; H, 8.88. Found: C,
22
45
19 36
9
n
n
ppm)).
55.71; H, 8.93.PG2
7
,13-Bis((2-methoxyethoxy)methyl)-10-((3-methylbuta-1,3-dien-
According to general procedure for polymerization (E) from MG2
(108 mg, 0.20 mmol), AIBN (0.2 mol %) and toluene (0.10 mL),
2
-yl)oxy)-2,5,8,12,15,18-hexaoxanonadecane (MG2). Esterification
procedure (D). To a solution of 8 (1.00 g, 1.0 equiv, 2.12 mmol) in
DCM (10.0 mL) were added DIEA (0.77 mL, 2.1 equiv, 4.45 mmol)
and DMAP (26 mg, 0.1 equiv) under N atmosphere. The mixture was
polymerization for 17 h afforded PG2 as a colorless sticky solid (100
1
mg, 93%). H NMR (300 MHz, CDCl ): 4.70 (br., 1H); 3.60−3.51
3
1
3
2
(m, 30H); 3.34 (s, 12H); 2.11 (br., 1.2H); 0.89 (br., 2.6H). C NMR
cooled to 0 °C and methacryloyl anhydride (0.63 mL, 2.0 equiv., 4.24
mmol) was slowly added neat. Thereafter the reaction mixture was
warmed to room temperature, then heated to 40 °C and stirred
overnight. The obtained solution was quenched with saturated
(75 MHz, CDCl ): 78.5; 71.9; 70.9; 70.8; 70.7; 58.9. Anal. Calcd (%)
3
for (C H O ) (540.65) : C, 55.54; H, 8.95. Found: C, 55.65; H,
25
48 12
n
n
9.02.PG3
According to general procedure for polymerization (E) from MG3
aqueous NaHCO and extracted with DCM. The organic phase was
(107 mg, 0.10 mmol), AIBN (0.5 mol %) and toluene (0.05 mL),
3
dried over MgSO and concentrated in vacuo. The residue was purified
polymerization for 17 h afforded PG3 as a colorless sticky solid (40
4
1
by flash chromatography with ethyl acetate/acetone (1:1, v/v) to
mg, 37%). H NMR (300 MHz, CDCl ): 4.64 (br., 0.8H); 3.60−3.50
3
1
13
afford MG2 as a pale yellow oil (0.94 g, 82%). H NMR (300 MHz,
(m, 61H); 3.33 (s, 24H); 1.94 (br., 0.9H); 0.82 (br., 2.4H). C NMR
H
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
(
(
9
75 MHz, CDCl ): 78.5; 72.0; 70.7; 58.9. Anal. Calcd (%) for
B.; Schlu
B 2013, 117, 6007−6017.
(8) (a) Fornera, S.; Balmer, T. E.; Zhang, B.; Schlu
P. Macromol. Biosci. 2011, 11, 1052−1067. (b) Grotzky, A.; Nauser, T.;
Erdogan, H.; Schluter, A. D.; Walde, P. J. Am. Chem. Soc. 2012, 134,
̈
ter, A. D.; Halperin, A.; Kro
̈
ger, M.; Aleman, C. J. Phys. Chem.
3
C H O ) (1069.28) : C, 55.04; H, 9.05. Found: C, 54.84; H,
4
9
96 24
n
n
.04.PG1co2
̈
ter, A. D.; Walde,
According to general procedure for polymerization (E) from MG1 (41
mg, 0.15 mmol), MG2 (81 mg, 0.15 mmol), AIBN (0.1 mol %) and
toluene (0.10 mL), polymerization for 17 h afforded PG1co2 (1:1) as
̈
1
1392−11395. (c) Fornera, S.; Kuhn, P.; Lombardi, D.; Schlu
D.; Dittrich, P. S.; Walde, P. ChemPlusChem. 2012, 77, 98−101.
d) Fornera, S.; Bauer, T.; Schluter, A. D.; Walde, P. J. Mater. Chem.
2012, 22, 502−511.
9) (a) Amjad, Z. Water Soluble Polymers: Solution Properties and
̈
ter, A.
1
a colorless sticky solid (89 mg, 73%). H NMR (600 MHz, CDCl ):
3
4
1
7
.84 (br., 1H); 4.73 (br., 1H); 3.70−3.52 (m, 42H); 3.36 (s, 18H);
(
̈
13
.82 (br., 2.4H); 1.01−0.89 (m, 5.7H). C NMR (75 MHz, CDCl ):
3
8.6; 72.0; 71.0; 70.8; 59.0.PG1co3
(
According to general procedure for polymerization (E) from MG1 (28
Applications; Kluwer Academic publishers: Dordrecht, The Nether-
lands, 2002. (b) Khayat, K. H. Cement Concrete Comp. 1998, 20, 171−
mg, 0.10 mmol), MG3 (107 mg, 0.10 mmol), AIBN (0.2 mol %) and
toluene (0.10 mL), polymerization for 17 h afforded PG1co3 (2:1) as
a colorless sticky solid (81 mg, 75%). H NMR (300 MHz, CDCl ):
1
88. (c) Nussinovitch, A. Water-soluble polymer applications in Foods;
1
3
Blackwell Science: Oxford, U.K., 2003. (d) Ye, Y.-S.; Rick, J.; Hwang,
k, J. Adv. Drug Delivery
4
1
7
.83 (br., 0.91H); 4.67 (br., 0.46H); 3.60−3.50 (m, 47H); 3.35 (s,
B.-J. Polymers 2012, 4, 913−963. (e) Kopece
̌
8H); 1.86 (br., 2.4H); 0.92 (br., 4.1H). 13C NMR (75 MHz, CDCl ):
3
Rev. 2013, 65, 49−59. (f) Nguyen, D.-D.; Devlin, L. P.; Koshy, P.;
8.5; 72.0; 71.0; 70.8; 59.0.PG2co3
Sorrell, C. C. J. Mater. Sci. 2014, 49, 923−951.
According to general procedure for polymerization (E) from MG2 (54
mg, 0.10 mmol), MG3 (107 mg, 0.10 mmol), AIBN (0.2 mol %) and
(10) (a) Lutz, J. F.; Akdemir, O.; Hoth, A. J. Am. Chem. Soc. 2006,
1
28, 13046−13047. (b) Lutz, J. F. J. Polym. Sci., Polym. Chem. 2008,
toluene (0.10 mL), polymerization for 17 h afforded PG2co3 (2:1) as
a colorless sticky solid (107 mg, 75%). H NMR (300 MHz, CDCl ):
4
0
5
1
46, 3459−3470. (c) Cheng, G.; Hua, F. J.; Melnichenko, Y. B.; Hong,
K.; Mays, J. W.; Hammouda, B.; Wignall, G. D. Macromolecules 2008,
41, 4824−4827. (d) Jia, Z. F.; Li, G. L.; Zhu, Q.; Yan, D. Y.; Zhu, X. Y.;
Chen, H.; Wu, J. L.; Tu, C. L.; Sun, J. Chem.Eur. J. 2009, 15, 7593−
3
.70 (br., 1H); 3.60−3.50 (m, 60H); 3.34 (s, 24H); 1.93 (br., 1.4H);
.88 (br., 2.7H). 13C NMR (75 MHz, CDCl ): 78.5; 72.0; 70.8; 70.7;
3
8.9.
7
600. (e) Qiao, Z. Y.; Du, F. S.; Zhang, R.; Liang, D. H.; Li, Z. C.
Macromolecules 2010, 43, 6485−6494. (f) Cheng, H. X.; Xie, S. A.;
ASSOCIATED CONTENT
■
Zhou, Y. F.; Huang, W.; Yan, D. Y.; Yang, J. T.; Ji, B. J. Phys. Chem. B
*
S
Supporting Information
2
010, 114, 6291−6299. (g) Yamanaka, J.; Kayasuga, T.; Ito, M.;
Yokoyama, H.; Ishizone, T. Polym. Chem. 2011, 2, 1837−1848.
h) Lutz, J. F. Adv. Mater. 2011, 23, 2237−2243. Bebis, K.; Jones, M.
W.; Haddleton, D. M.; Gibson, M. I. Polym. Chem. 2011, 2, 975−982.
i) Weiss, J.; Li, A.; Wischerhoff, E.; Laschewsky, A. Polym. Chem.
012, 3, 352−361. (j) Bai, L.; Li, W.; Chen, J.; Bo, F.; Gao, B.; Liu, H.;
Li, J.; Wu, Y.; Ba, X. Macromol. Rapid Commun. 2013, 34, 539−547.
k) Zhang, X.; Li, W.; Zhao, X.; Zhang, A. Macromol. Rapid Commun.
1
13
H and C NMR spectra of all new compounds and polymers.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(
(
2
AUTHOR INFORMATION
Corresponding Author
(A.D.S.) E-mail: dieter.schlueter@mat.ethz.ch.
Notes
■
*
(
2
013, 34, 1701−1707. (l) Mei, J.; Bao, Z. Chem. Mater. 2014, 26,
6
(
04−615.
The authors declare no competing financial interest.
11) (a) Li, W.; Zhang, A.; Feldman, K.; Walde, P.; Schlu
̈
ter, A. D.
ter,
Macromolecules 2008, 41, 3659−3667. (b) Li, W.; Zhang, A.; Schlu
̈
ACKNOWLEDGMENTS
■
A. D. Chem. Commun. 2008, 5523−5525. (c) Li, W.; Zhang, X.; Zhao,
We thank Prof. G. Wegner (Max Planck Institute for Polymer
Research, Mainz, Germany) for helpful discussions, Dr. T.
Schweizer (ETHZ) for valuable technical assistance and Prof.
N. D. Spencer (ETHZ) for access to the AFM instruments.
X.; Zhang, X.; Zhang, A. J. Polym. Sci., Part A: Polym. Chem. 2013, 51,
5143−5152. (d) Li, W.; Zhang, A.; Schlu
2008, 41, 43−49. (e) Wu, W.; Driessen, W.; Jiang, X. J. Am. Chem. Soc.
014, 136, 3145−3155. (f) Wang, L.; Kiemle, D. J.; Boyle, C. J.;
Connors, E. L.; Gitsov, I. Macromolecules 2014, 47, 2199−2213.
g) Simon-Gracia, L.; Pulido, D.; Sevrin, C.; Grandfils, C.; Albericio,
F.; Royo, M. Org. Biomol. Chem. 2013, 11, 4109−4121.
12) Junk, M. J. N.; Li, W.; Schluter, A. D.; Wegner, G.; Spiess, H.
W.; Zhang, A.; Hinderberger, D. Angew. Chem., Int. Ed. 2010, 49,
683−5687.
13) (a) Rajaram, S.; Choi, T. L.; Rolandi, M.; Frec
Chem. Soc. 2007, 129, 9619−9621. (b) Fiset, E.; Morin, J. F. Polymer
009, 50, 1369−1377. (c) Piunova, V. A.; Miyake, G. M.; Daeffler, C.
S.; Weitekamp, R. A.; Grubbs, R. H. J. Am. Chem. Soc. 2013, 135,
5609−15616.
14) (a) Zhang, Y. H.; Chen, Y. M.; Niu, H. J.; Gao, M. Y. Small
̈
ter, A. D. Macromolecules
2
(
́
REFERENCES
■
(
1) (a) Schlu
64−883. (b) Schlu
c) Frauenrath, H. Prog. Polym. Sci. 2005, 30, 325−384. (d) Rosen, B.
̈
ter, A. D.; Rabe, J. P. Angew. Chem., Int. Ed. 2000, 39,
ter, A. D. Top. Curr. Chem. 2005, 245, 151−191.
(
̈
8
̈
(
5
M.; Wilson, C. J.; Wilson, D. A.; Peterca, M.; Imam, M. R.; Percec, V.
Chem. Rev. 2009, 109, 6275−6540. (e) Chen, Y.; Xiong, X. Chem.
Commun. 2010, 46, 5049−5060. (f) Paez, J. I.; Martinelli, M.; Brunetti,
V.; Strumia, M. C. Polymers 2012, 4, 355−395.
(
́
het, J. M. J. J. Am.
2
(
2) Zhang, B.; Wepf, R.; Kro
Macromolecules 2011, 44, 6785−6792.
3) (a) Guo, Y.; van Beek, J. D.; Zhang, B.; Colussi, M.; Walde, P.;
Zhang, A.; Kroger, M.; Halperin, A.; Schluter, A. D. J. Am. Chem. Soc.
009, 131, 11841−11854. (b) Zhang, B.; Wepf, R.; Fischer, K.;
Schmidt, M.; Besse, S.; Lindner, P.; King, B. T.; Sigel, R.;
Schurtenberger, P.; Talmon, Y.; Ding, Y.; Kroger, M.; Halperin, A.;
Schluter, A. D. Angew. Chem., Int. Ed. 2011, 50, 737−740.
4) Schluter, A. D. Chimia 2013, 67, 804−810.
5) Kroger, A.; Zhang, B.; Rosenauer, C.; Schluter, A. D.; Wegner, G.
̈
̈
ger, M.; Halperin, A.; Schluter, A. D.
1
(
(
2
006, 2, 1314−1319. (b) Zhang, Y.; Li, X. K.; Deng, G. H.; Chen, Y.
̈
̈
M. Macromol. Chem. Phys. 2006, 207, 1394−1403. (c) Zhang, Y. H.;
Xu, Z. Z.; Li, X. K.; Chen, Y. M. J. Polym. Sci., Part A: Polym. Chem.
2
2
007, 45, 3303−3310. (d) Zhang, Y. H.; Xu, Z. Z.; Li, X. K.; Chen, Y.
M. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 3994−4001.
e) Rajaram, S.; Choi, T.-L.; Rolandi, M.; Frechet, J. M. J. J. Am. Chem.
̈
̈
(
(
(
̈
Soc. 2007, 129, 9619−9621. (f) Xiong, X. Q.; Chen, Y. M.; Feng, S.;
Wang, W. J. Polym. Sci.,Part A: Polym. Chem. 2010, 48, 3515−3522.
(g) Kim, K. O.; Choi, T.-L. Macromolecules 2013, 46, 5905−5914.
̈
̈
Colloid Polym. Sci. 2013, 2879−2892.
6) (a) Meller, A. Adv. Chem. Phys. 2012, 149, 251−268.
b) Oukhaled, A.; Bacri, L.; Pastoriza-Gallego, M.; Betton, J.-M.;
Pelta, J. ACS Chem. Biol. 2012, 7, 1935−1949.
7) (a) Bertran, O.; Zhang, B.; Schluter, A. D.; Halperin, A.; Kro
M.; Aleman, C. RSC Adv. 2013, 3, 126−140. (b) Bertran, O.; Zhang,
(
(
(15) (a) Krebs, A.; Bruchmann, B.; Mu
̈
ller-Cristadoro, A.; Al-Hellani,
R.; Schlu
̈
ter, A. D. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 1372−
(
̈
̈
ger,
1377. (b) Al-Hellani, R.; Bruchmann, B.; Schoenfelder, D.; Cristadoro,
A.; Leyrer, R. J.; Arisandy, C. WO 2011/006838, Patent Application,
I
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
BASF SE, 2011;. (c) Suen, T. J. US Patent 2,678,308, American
Cyanamid Co.: 1954.
(
16) Pasquino, R.; Zhang, B.; Sigel, R.; Yu, H.; Ottiger, M.; Bertran,
O.; Aleman, C.; Schluter, A. D.; Vlassopoulos, D. Macromolecules 2012,
5, 8813−8823.
17) (a) Yi, G. R.; Pine, D. J.; Sacanna, S. J. Phys.: Condens. Matter
013, 25, 193101. (b) Li, F.; Josephson, D. P.; Stein, A. Angew. Chem.,
Int. Ed. 2011, 50, 360−388.
18) Jayaraman, M.; Frechet, J. M. J. J. Am. Chem. Soc. 1998, 120,
2996−12997.
19) Wyszogrodzka, M.; Haag, R. Chem.Eur. J. 2008, 14, 9202−
214.
20) Shatzmiller, S.; Dolitzki, B.-Z. Liebigs Ann. Chem. 1991, 189−
94.
21) (a) Tsukahara, Y.; Hayashi, N.; Jiang, X.-L.; Yamashita, Y. Polym.
̈
4
(
2
(
́
1
(
9
(
1
(
J. 1989, 21, 377−391. (b) Tsutsumi, K.; Tsukahara, Y.; Okamoto, Y.
Polym. J. 1994, 26, 1318−1324. (c) Tsukahara, Y.; Ito, K.; Tsai, H.-C.;
Yamashita, Y. J. Polym. Sci., Part A: Polym. Chem. 1989, 27, 1099−
1
114.
22) (a) Zhang, A.; Zhang, B.; Wac
Schlu
ter, A. D. Chem.Eur. J. 2003, 9, 6083−6092. (b) Zhang, A.;
Okrasa, L.; Pakula, T.; Schluter, A. D. J. Am. Chem. Soc. 2004, 126,
658−6666.
(
̈
htersbach, E.; Schmidt, M.;
̈
̈
6
J
dx.doi.org/10.1021/ma5017192 | Macromolecules XXXX, XXX, XXX−XXX