Nanostructured poly(ethylene oxide)-like dendron-block-linear poly(ethylene-alt-propylene) copolymers: Design, synthesis, and thermal and assembling properties

Article abstract of DOI:10.1039/c2sm07240h

A series of self-assembling dendron-coil block copolymers with well-defined molecular structures were prepared via a divergent method. The hydrophilic and hydrophobic blocks are composed of PEO-like dendrons and poly(ethylene-alt- propylene) (PEP) linear coils, respectively. A dendron-coil, 2G-2400 (2G and 2400 indicate the dendron generation and PEP molecular weight, respectively), showed a melting transition of the peripheral PEO chains. In contrast, the dendron-coils containing the 3^rd generation dendron did not show any melting transition because of the plasticization effect of the tri(ethylene oxide) branches. Due to the strong immiscibility between the PEO-like dendron and PEP blocks, diverse microphase-separated morphologies were observed. 2G-2400 displayed a lamellar mesophase with an interdigitated dendron packing structure. For the larger 3^rd generation dendron series, A15 micellar cubic (Pm3n space group), hexagonal columnar, and lamellar morphologies were revealed depending on the PEP coil length and/or temperature. For the columnar mesophases, the molecular wedge angles (α) were calculated to be 46.8° and 34.6° for 3G-2400 and 3G-3400, respectively. This suggests that the longer PEP coil of 3G-3400 is conformationally more deformed in the columnar structure. As a consequence, the columnar phase was transformed into an interdigitated lamellar structure as the temperature increased. This order to order transition is a reversal of the well-known phase sequence of linear block copolymers. This unusual morphological behavior is mainly attributed to the unique molecular arrangement associated with non-conventional dendron-coil chain architecture. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2sm07240h

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PAPER
Nanostructured poly(ethylene oxide)-like dendron-block-linear
poly(ethylene-alt-propylene) copolymers: design, synthesis, and thermal
and assembling properties
*
Jie Song and Byoung-Ki Cho
Received 24th November 2011, Accepted 9th January 2012
DOI: 10.1039/c2sm07240h
A series of self-assembling dendron-coil block copolymers with well-defined molecular structures were
prepared via a divergent method. The hydrophilic and hydrophobic blocks are composed of PEO-like
dendrons and poly(ethylene-alt-propylene) (PEP) linear coils, respectively. A dendron-coil, 2G-2400
(2G and 2400 indicate the dendron generation and PEP molecular weight, respectively), showed
a melting transition of the peripheral PEO chains. In contrast, the dendron-coils containing the 3rd
generation dendron did not show any melting transition because of the plasticization effect of the
tri(ethylene oxide) branches. Due to the strong immiscibility between the PEO-like dendron and PEP
blocks, diverse microphase-separated morphologies were observed. 2G-2400 displayed a lamellar
mesophase with an interdigitated dendron packing structure. For the larger 3rd generation dendron
series, A15 micellar cubic (Pm3n space group), hexagonal columnar, and lamellar morphologies were
revealed depending on the PEP coil length and/or temperature. For the columnar mesophases, the
molecular wedge angles (a) were calculated to be 46.8ꢀ and 34.6ꢀ for 3G-2400 and 3G-3400, respectively.
This suggests that the longer PEP coil of 3G-3400 is conformationally more deformed in the columnar
structure. As a consequence, the columnar phase was transformed into an interdigitated lamellar
structure as the temperature increased. This order to order transition is a reversal of the well-known
phase sequence of linear block copolymers. This unusual morphological behavior is mainly attributed to
the unique molecular arrangement associated with non-conventional dendron-coil chain architecture.
<10 kg molꢁ1, displayed a variety of mesophases such as lamellar,
Introduction
perforated lamellar, bicontinuous cubic, and hexagonal columnar
structures.3 Despite such rich phase behavior, only a crystalline
lamellar morphology was observed at room temperature (RT),
due to the crystallization of the linear PEO coil. This PEO crys-
tallization occurring above a room temperature is a critical
drawback for practical purposes, because a certain material
function can be maximized depending on the morphological
feature. Therefore, in order to utilize as many structures as
possible at room temperature for material applications, an
amorphous block has to be used instead of a crystalline one.
In this context, a modification of the linear crystalline PEO
into a branched PEO could be an approach for solving the
crystallization problem. As a way, we could design PEO-like
dendrons based upon tri(ethylene oxide) (TEO) spacers, phlor-
oglucinol branching junctures, and peripheral PEOs. Then,
a combination of this type of PEO-like dendron and an appro-
priate polyalkylene will provide fully amorphous amphiphilic
block copolymers. To this end, we prepared a novel series of
dendron-coil block copolymers (Fig. 1 and Scheme 2). As
a hydrophobic block, we employed linear poly(ethylene-alt-
propylene)s (PEPs) because this is amorphous and easy to
prepare via a hydrogenation of polyisoprene (PI). To date, only
The variation of polymer chain topology into non-conventional
types has a great influence on the phase behavior in a block
copolymer system. Among the possible block copolymer archi-
tectures, a dendron-coil architecture is particularly interesting
because the two molecular extremes are covalently combined.1
These blocks are known to have distinct thermal properties such
as melting and glass transition temperatures.2 In comparison to
linear polymers, the branched counterparts have lower melting
and glass transition temperatures, and they become completely
amorphous in some cases.
Amphiphilic block copolymers, consisting of polyalkylene and
poly(ethylene oxide) (PEO) blocks, have a strong segregation
tendency in both bulk and solution states. Due to the great
immiscibility between the blocks, they are able to form ordered
molten structures (mesophases) in a relatively small molecular
weight regime. For example, poly(ethyl ethylene)-b-poly(ethylene
oxide) (PEE-b-PEO) copolymers, with molecular weights of
Department of Chemistry and Institute of Nanosensor and Biotechnology,
Dankook University, Gyeonggi-Do, 448-701, Korea. E-mail: chobk@
dankook.ac.kr; Fax: +82 31 8005 3148; Tel: +82 31 8005 3153
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Fig. 1 Schematics of dendron-coils consisting of amorphous PEO-like
dendrons and linear PEPs.
a few block copolymers were reported to contain PEO-like
dendron blocks, perhaps because of the difficulty of synthesis.4 In
most block copolymers, linear PEOs were used as the hydrophilic
block.5 Therefore, our dendron-coils are topologically unique
block copolymers, and this structural feature has a significant
influence on the thermal and assembling properties. In this
paper, we present the details of the divergent synthesis, and the
thermal and self-assembling properties of a series of dendron-
coils. To manipulate the mesomorphic behavior, we varied the
dendron size and PEP coil length as molecular parameters. One
interesting finding was that we observed an unusual phase
change (i.e., a columnar-to-lamellar transition) upon heating,
and this mechanism was addressed.
Scheme 1 Synthesis of (a) linear PEP coils (2a–c), (b) AB2- and AB4-
type branching units (5 and 7), and (c) diPEGylated phloroglucinol (11).
Reagents and conditions: (i) C6H12; (ii) ethylene oxide; (iii) methanolic
HCl; (iv) 10% Pd/C, H2, 30 psi, C6H12; (v) TsCl, pyridine, CH2Cl2; (vi)
10% Pd/C, H2, 30 psi, MeOH/CHCl3; and (vii) K2CO3, KI, CH3CN.
Results and discussion
Synthesis
branching precursors, the hydroxyl end of the PEP-OH was
converted into a tosyl group.
Dendron-coils consist of three structural components: linear
PEP, TEO dendritic spacers, and PEO peripheries. In the
synthesis, the growth of the branched chain was done mostly
with Williamson etherification, debenzylation, and tosylation.
These elemental reactions are known to be conventional and free
of side reactions, and their resulting yields were revealed to be
very quantitative, generally more than 70%.
Hydrophilic branching (5 and 7) and peripheral (11) precur-
sors were prepared, as shown in Schemes 1(b) and (c). The reason
for the preparation of the tetrabranched branching component
(7) is to simplify the reaction procedure for the 3rd generation
dendron-coils. Although a stepwise protocol, starting from
dibranched compound 5, could also be applied in the higher 3rd
generation series, tosylation and etherification have to be
implemented in each 3rd generation divergent synthesis, which
would be tedious in terms of the synthetic scheme.
Before the divergent dendritic growth, each part was individ-
ually prepared, as outlined in Scheme 1. First, linear PEP blocks
(2a–c) with a tosyl end were prepared by a combination of living
anionic polymerization of isoprene, catalytic hydrogenation, and
the subsequent tosylation of the hydroxyl end group (Scheme
1(a)). Isoprene was polymerized in cyclohexane using sec-butyl-
lithium as the initiator. The polyisoprene (PI) end was then
capped with one ethylene oxide unit, and protonated with
degassed methanolic HCl, yielding hydroxylated polyisoprenes
(PI-OHs).5b The resulting PI-OHs contained 1,4-regioisomeric
repeating units (ca. 91%), as characterized by the 1H NMR
technique. The PI-OHs were then hydrogenated in cyclohexane
using Pd/C and H2. Complete saturation was reached after
48 hours in all cases, as confirmed by no olefin signal at 5.35–
4.62 ppm in the 1H NMR spectra. The number average molecular
weights (Mn) and the polydispersities (Mw/Mn) of the resulting
PEP-OHs are presented in Table 1. The polydispersities, in all
cases, were less than 1.08, which is indicative of their narrow
molecular weight distributions. For the next coupling step with
Dibranched (AB2-type) and tetrabranched (AB4-type)
components 5 and 7 possess one phenol (A) at the focal point, as
well as two and four peripheral aliphatic alcohol groups (B),
Table 1 Characterization of PI-OHs and PEP-OHs (1a–c)
a
b
Sample
Mn /g molꢁ1
Mw/Mn
DPa
P1 precursor of 1a
1a
P1 precursor of 1b
1b
P1 precursor of 1c
1c
1390
1430
2340
2410
3280
3380
1.11
1.08
1.05
1.05
1.03
1.03
20
20
34
34
48
48
a
Determined from the end-group analysis of 1H-NMR spectra.
Determined by the GPC data.
b
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respectively. Due to the different pKa values, only the phenol
group can be deprotonated under potassium carbonate (K2CO3)
and thereby participate in the Williamson etherification, e.g. the
etherification between 4 and 5 in Scheme 1(b). After the chain
growth, the focal phenolic group can be regenerated by deben-
zylation using Pd/C and H2.
Similarly, the peripheral component, i.e. diPEGylated phlor-
oglucinol (11), consisting of two poly(ethylene glycol) mono-
methyl ethers (DP ¼ 7), was prepared by the etherification of
monobenzylated phloroglucinol with tosylated PEO coils and
subsequent debenzylation (Scheme 1(c)).
The Williamson etherification and the tosylation of terminal
alcohols were identically applied to the divergent synthesis of the
final dendron-coils (Scheme 2). The PEP coils with tosyl ends (2b
and 2c) were reacted with the excess of dibranched and tetra-
branched branching components (5 and 7) in the presence of
K2CO3, yielding intermediate compounds 12 and 14b–c. It is
because the remaining branching components were easily
removed by the selective precipitation of the products in meth-
anol. On the other hand, another intermediate 14a, with the
shortest PEP block, was not precipitated in methanol. Thus, in
the coupling reaction with 7, the excess of 2a was used for
a convenient column chromatography. In the TLC, after the
reaction, the leftover of hydrophobic 2a had a much larger
Rf value than 14a.
Next, the conversion of the terminal alcohols of 12 and 14a–c
into tosyl ends and the subsequent etherification with the excess
of the peripheral component (11) resulted in the final dendron-
coil copolymers. The purification of the final dendron-coils was
performed by a combination of silica-column chromatography
and preparative gel permeation chromatography (GPC) tech-
niques. After purification, the dendron-coils were characterized
by NMR spectroscopies, GPC, and matrix-assisted laser
Scheme 2 Divergent synthetic routes of (a) 2G-2400 and (b) 3rd gener-
ation series (3G-1400, 3G-2400, and 3G-3400). Reagents and conditions:
(i) K2CO3, KI, CH3CN and (ii) TsCl, pyridine, CH2Cl2.
desorption/ionization
time-of-flight
mass
spectrometry
All dendron-coils showed narrow molecular weight distribu-
tions (Mw/Mn) of less than 1.02 in the GPC data, indicative of
high purities (Fig. 3(a) and Table 2). It is interesting to note that
2G-2400 showed a smaller retention volume than 3G-1400, which
(MALDI-TOF MS).
The H- and 13C-NMR spectra of the final dendron-coils are
shown in Fig. 2. By comparing the integration areas of aromatic
(assigned as c) and ethylene oxide parts, the numbers of the
phloroglucinol protons were calculated to be 9 and 21 for
2G-2400 and the 3rd generation series, respectively. In addition,
the integration value of the terminal methoxy protons (assigned
as i) of 3G-2400 with respect to the identical PEP (assigned as
a and b) is nearly twice as large as 2G-2400 (Fig. 2(a) and (c)).
These 1H NMR data strongly suggest that the peripheral
components (11) were completely coupled with 13 and 14a–c in
the final Williamson reaction, and thus the resulting dendron-
coils have no structural defects on the periphery. At the same
time, the integration area of the PEP part (assigned as a and b)
relative to the identical aromatic proton area increases propor-
tionally to the PEP molecular weight. The number-average
degree of polymerization (DP) of the linear PEP was calculated
to be 20, 34, and 48 for 3G-1400, 3G-2400, and 3G-3400,
respectively (Fig. 2(b)–(d)). On the basis of these integration
analyses, the number average molecular weights (Mn) were
calculated, and they quantitatively matched the expected values
(Table 2). In addition to the proton NMR results, eleven distinct
carbon signals were observed in the 13C NMR spectra of the
dendron-coils, which corroborates the successful synthesis as
designed (Fig. 2(e)–(h)).
1
1
is in contrast to the molecular weights calculated from the H
NMR spectra (Fig. 3(a) and Table 2). This mismatch is
Fig. 2 1H-(left) and 13C-(right) NMR spectra of (a and e) 2G-2400,
(b and f) 3G-1400, (c and g) 3G-2400, and (d and h) 3G-3400.
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Table 2 Characterization of dendron-coils
Mn/g molꢁ1
Hydrophilic volume
fraction (f)
c
Dendron-coil
NMRa
MSb
Mw/Mn
Morphologyd
Lattice parameter/nm
TODT/ꢀC
2G-2400
3G-1400
3G-2400
3G-3400
4300
5570
6550
7520
4320
5560
6560
7520
1.02
1.02
1.02
1.02
0.37
0.69
0.57
0.48
LAM
MC
COL
COL
LAM
11.1e
22.4f
14.9e
18.8e
11.3g
183
158
Not shownh
Not shownh
a
b
c
d
1
Determined from the H-NMR spectra. Determined from the MALDI-TOF MS data. Determined from the GPC data. LAM: lamellar, MC:
micellar cubic, COL: columnar. e Determined at 30 ꢀC. f Determined at 155 ꢀC. g Determined at 200 ꢀC. h No TODT was detected up to 200 ꢀC.
attributed to the more compact globular shape of highly
branched 3G-1400 than 2G-2400 in the THF solution.6 Indeed,
the accurate molecular weights were determined by the MALDI-
TOF MS. Fig. 3(b) shows the narrow and symmetric MALDI-
TOF MS spectra, which provide the direct evidence that there are
no structural defects. The molecular weights of the highest peak
are 4320 g molꢁ1, 5560 g molꢁ1, 6560 g molꢁ1, and 7520 g molꢁ1
for 2G-2400, 3G-1400, 3G-2400, and 3G-3400, respectively.
To interpret the morphological behavior of the final dendron-
coils in the next section, it would be helpful to determine the
dendron volume fractions (f). In the f calculations, we assumed
that the densities of the hydrophobic PEP and the hydrophilic
part (PEO-like dendritic branches plus peripheral PEOs) are 0.79
g cmꢁ3 and 1.06 g cmꢁ3, respectively.7 The calculated fs were 0.37,
0.69, 0.57, and 0.48 for 2G-2400, 3G-1400, 3G-2400 and 3G-
3400, respectively.
the melting of the peripheral PEO chains. The heat of fusion was
estimated to be 18.8 J gꢁ1, on the basis of which its crystallinity
was calculated to be 38.7%, by comparing the heat of fusion of the
perfect crystalline PEO chain.8 In contrast, the 3rd generation
series with the larger dendron exhibited no PEO melting transi-
ꢀ
tion, while the Tgs were observed near ꢁ51 C in all cases. This
might be because the semi-crystalline peripheral PEOs were
plasticized by the larger 3rd generation dendritic core, resulting in
the complete suppression of PEO crystallization.9
The incompatibility between hydrophobic PEP and PEO
blocks led to ordered phases (i.e., mesophase) in the melt. As
consistent with the polymer design concept in the Introduction,
all mesophases could be observed at ambient temperature, and
persisted up to temperatures above 150 ꢀC. The temperature-
variable small angle X-ray scattering (SAXS) and dynamic
mechanical spectroscopy (DMS) experiments verified order–
order and order–disorder transition temperatures (OOT and
TODT), and the structural information in each mesophase. 2G-
2400 and 3G-1400 exhibited their TODTs at 183 ꢀC and 158 ꢀC,
respectively, while 3G-2400 and 3G-3400 maintained their
ordered phases up to the experimentally accessible temperature
of 240 ꢀC.
Thermal and self-assembling properties
Melting and glass transition temperatures (Tm and Tg) were
investigated by differential scanning calorimetry (DSC), scanning
from ꢁ70 to 50 ꢀC (Fig. 4). Among the polymers, only 2G-2400,
with the smaller 2nd generation dendron, showed a Tm at ꢁ3.1 ꢀC.
Considering the molecular composition, the Tm corresponds to
2G-2400 with f ¼ 0.37 formed a mesophase that turned into
a disordered liquid at 183 ꢀC (Fig. 5). The SAXS pattern at 30 ꢀC
showed four reflections with q-spacing ratios of 1 : 2 : 3 : 4,
indicative of a lamellar structure (Fig. 6(a)). It has been known
that the elastic modulus (G0) representing the overall elasticity of
Fig. 3 (a) GPC elugrams and (b) MALDI-TOF MS data of dendron-
coils.
Fig. 4 DSC thermograms of dendron-coils.
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a system increases as the structural dimensionality increases.10
Therefore, the SAXS result is consistent with the DMS data
where the mesophase exhibits relatively low G0 near 104 Pa.
Because lamellar morphology is one-dimensionally periodic, the
degree of shear-induced deformations in a polydomain lamellar
sample is smaller than two-dimensionally periodic cylindrical
and three-dimensionally cubic structures.
From the observed primary peak, d-spacing was estimated to
be 11.1 nm (Table 2). To understand the packing structure, e.g.,
bilayered or interdigitated monolayered, in the lamellar meso-
phase, we calculated the molecular section which was assumed to
be a square column. By comparing the height of the molecular
section with the d-spacing, we could determine the molecular
packing of the lamellar structure. In the calculation, the fully
stretched length of the peripheral PEO chain was estimated to be
3.2 nm from the CPK model, and the cross-sectional area of the
square column was determined to be 0.71 nm2. Then, by dividing
the molecular volume by the cross-sectional area, the height of
the molecular section was found to be 10.7 nm, which is almost
identical to the d-spacing of 11.1 nm from the SAXS data.
Therefore, 2G-2400 self-assembles into an interdigitated mono-
layer, which contrasts the bilayered lamellar structure of linear
block copolymers (Fig. 7). The formation of an interdigitated
monolayer rather than the bilayered packing is driven by the
conformational entropy of the longer PEP coil; otherwise, the
bilayered structure would be enthalpically favored because of
the minimal interfacial area between the two blocks. As
compared to the bilayered lamellar, the cross-section of the PEP
coil in the interdigitated packing is twice larger, by which PEP
coils reside in a less anisotropic space (Fig. 7). Consequently, the
PEP coil is less stretched.
Fig. 6 SAXS data of (a) 2G-2400, (b) 3G-1400, (c) 3G-2400, and
(d and e) 3G-3400.
three-dimensional cubic lattices.1e,11 Therefore, the DMS data
suggest a cubic mesophase.
The SAXS data of 3G-1400 at 155 ꢀC showed a large number
of reflections (Fig. 6(b)). These SAXS peaks can be indexed as the
(110), (200), (210), (211), (220), (310), (321), (400), and (420) of
a Pm3n cubic symmetry (Table 3), which is consistent with the
DMS results. From the dimension of the (200) reflection, the
cubic lattice parameter was calculated to be 22.4 nm.
As the PEP length increased, 3G-2400 with f ¼ 0.57 displayed
seven
peaks
with
q-spacing
ratios
of
ꢀ
1 : O3 : O4 : O7 : O12 : O13 : O19 at 30 C (Fig. 6(c)). The reflec-
tions can be assigned as the (100), (110), (200), (210), (220), (310),
and (320) planes of a 2-D hexagonal columnar structure (Table
3). The observed multiple reflections are not common in typical
hexagonal columnar mesophases, which usually show three or
four reflections at most. The SAXS results indicate that micro-
phase-separated cylinders well-organize into a 2-D hexagonal
lattice, which might be due to the great immiscibility between the
hydrophilic PEO-like dendrons and the hydrophobic PEP coils.
From the d-spacing of the (100) plane, the inter-columnar
distance (a) was calculated to be 14.9 nm.
Morphological behavior in the 3rd generation series with the
identical dendron can be elucidated as a function of the dendron
volume fraction (f). The SAXS spectra of the 3rd generation series
are presented in Fig. 6.
3G-1400 with f ¼ 0.69 exhibited a mesophase before dis-
ordering at 158 ꢀC in the DMS data (Fig. 5). In addition, the G0
values in this mesophase were above 106 Pa, which indicates the
high elasticity of the mesophase. This magnitude in G0 is typically
observed in cubic mesophases, because of the large free energy
cost occurring from the deformations of highly symmetric
As the PEP length further increased, 3G-3400 with f ¼ 0.48
displayed two different mesophases as a function of temperature.
ꢀ
As shown in the DMS data, the G0 began to drop near 90 C,
after which another plateau region appeared. By considering the
Fig. 5 Dynamic mechanical spectroscopy data of dendron-coils as
a function of temperature.
Fig. 7 Interdigitated lamellar model of 2G-2400.
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Table 3 The measured distances (dmeas ¼ 2p/q) and corresponding (hkl)
indexation data of the observed SAXS reflections for the micellar cubic
and hexagonal columnar phases. dcalcd is the calculated distance based on
the lattice parameter of each structure
linear block copolymers which display a body-centered micellar
cubic structure.9,12 In the proposed structure, the micellar core is
comprised of hydrophobic PEPs, while hydrophilic dendrons
constitute the outer matrix. On the basis of the SAXS data and
the molecular volume, the number (Nm) of molecules occupying
a single micelle and the solid angle of the cone-shape molecule
was calculated to be approximately 158 and 2.28ꢀ,
respectively.1a,13
a
Hexagonal columnarb
ꢁ
Pm3n cubic
3G-1400
3G-2400
3G-3400
hkl dmeas/nm dcalcd/nm dmeas/nm dcalcd/nm dmeas/nm dcalcd/nm
ꢀ
On the basis of the SAXS data, 4.6 A thick column stratum
100
110 13.8
12.9
7.5
6.5
4.9
12.9
7.4
6.5
4.9
16.3
9.4
8.1
6.2
16.3
9.4
8.2
6.2
and relevant densities, the numbers of molecules per column
cross-section could be obtained using the following equation:
13.8
9.7
8.6
7.9
200
210
211
300
220
310
320
321
400
420
9.7
8.6
7.9
ꢀ
Nc ¼ 4.6 A ꢂ a ꢂ d(100)/Vm, where a and Vm are the lattice
parameter and molecular volume, respectively.14 The numbers
were calculated to be 7.7 and 10.4 for 3G-2400 and 3G-3400,
respectively. The increase in Nc can be explained by a molecular
wedge angle (a) depending on the PEP coil length. From the Nc,
the angles were calculated to be 46.8ꢀ and 34.6ꢀ for 3G-2400 and
3G-3400, respectively. For the identical 3rd generation dendron,
the increase of the PEP coil length decreases the molecular wedge
angle in the columnar structure (Fig. 9).
5.4
4.7
4.5
3.7
5.4
4.7
4.5
3.7
7.0
6.3
6.9
6.2
3.7
3.6
2.9
3.7
3.6
3.0
5.3
4.8
4.2
5.2
4.9
4.3
3.1
3.1
a
Data at 155 ꢀC. b Data at 30 ꢀC.
Considering the observed morphological results as a function
of f, the introduction of the dendritic block shifts the phase
boundaries toward smaller dendron volume fractions (i.e. larger
volume fractions of linear PEP) when compared to conventional
linear block copolymers.15 The above phase boundary argument
is even manifested in the 3rd generation series, as the asymmetric
factor becomes greater due to the larger 3rd generation dendron.
Our dendron-coil system is also different from block copoly-
mers bearing rigid p-conjugated dendrons. Since our polyether
dendrons are conformationally flexible, the dendron conforma-
tion can be tuned depending on the PEP coil length, resulting in
the various morphologies. In contrast, shape-persisted dendrons
preferentially lead to 2-D columnar structures with inherent
curvature. Indeed, a dendron-coil system based on dendritic
poly(phenylazomethine)s exclusively showed 2-D columnar
structures over a wide range of dendron volume fractions, 0.38 <
f < 59.16
magnitude of the elastic modulus in each mesophase, the
morphologies in the lower and higher temperatures can be sug-
gested to be hexagonal columnar and lamellar structures,
respectively. Indeed, the SAXS data exhibited the expected 2-D
hexagonal columnar and lamellar reflection patterns (Fig. 6(d)).
The columnar phase of 3G-3400 displayed an even larger number
of well-resolved reflections than that of 3G-2400 (Table 3). The
inter-columnar distance (a) of the columnar mesophase at 30 ꢀC
was 18.8 nm, and the periodic layer thickness of the lamellar
mesophase at 200 ꢀC was 11.3 nm. By a similar lamellar packing
consideration to 2G-2400, the height of the molecular section was
calculated to be 9.2 nm. Thus, the observed periodic dimension
suggests an interdigitated monolayer.
At the identical 3rd generation dendron, the increase of the PEP
coil length (i.e. the decrease of f) must lead to continuous PEP
domains. Therefore, the cubic morphology of 3G-1400 strongly
suggests a micellar cubic structure because 3G-2400 and 3G-3400
with longer PEP coils exhibited columnar structures. The phase
sequence of micellar to columnar structures with decreasing f is
the most plausible option. The micellar cubic phase with Pm3n
symmetry is referred to as A15 phase consisting of eight micelles
in a unit cell (Fig. 8). This micellar cubic structure was frequently
found in dendritic molecules, but it has not been observed in
It should be noted that the temperature-dependent trans-
formation in 3G-3400 is the complete reversal of the phase
sequence (i.e. from lamellar to gyroid, columnar, and micellar
Fig. 8 Formation of the micellar cubic mesophase with Pm3n symmetry
of 3G-3400. For clarity, the hydrophilic matrix is omitted in the picture
on the right.
Fig. 9 Molecular wedges of 3G-2400 and 3G-3400 in the columnar
structure.
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temperature increased. An unusual phase transition from
columnar to lamellar structures was observed in 3G-3400. This
temperature dependent phase transition is the complete reversal
of the phase sequence of linear block copolymers. Remarkably,
in the observed micellar and columnar morphologies in this
study, the continuous matrix consists of hydrophilic dendrons,
which can be an excellent structural platform for the next-
generation electrolyte materials.
Experimental
General methods
1H- and 13C-NMR spectra were recorded at room temperature on
Varian 200 and Varian 500 spectrometers, using chloroform-
d (CDCl3) as the solvent and tetramethylsilane (TMS) as the
internal reference for chemical shifts. The final products were
purified with a LC-9201 recycling preparative HPLC (Japan
Analytical Industry) equipped with a PI-50 pump, a UV detector/
310, a RI detector/RI-50s, and three JAIGEL-1H, 2H, 2.5H
columns (600 ꢂ 20 mm2). Chloroform was used as the eluent at
a flow rate of 3.5 mL minꢁ1. The purity of the products was
checked by thin-layer chromatography (TLC; Merck, silica gel
60). Gel permeation chromatography (GPC) measurements were
conducted in THF and N,N0-dimethylacetamide (99.9%)
(98 : 2 volume ratio) using a Waters 401 instrument equipped
with KF-802, KF-803, AT-G and AT-804S Shodex columns at
a flow rate of 1.0 mL minꢁ1. Monodisperse linear polystyrene
standards were used for calibration. THF (with 2% v/v N,N-
dimethylacetamide) ꢀwas used as the eluent, and the rate was
1.0 mL minꢁ1 at 35 C. Matrix-assisted laser desorption ioniza-
tion time-of-flight (MALDI-TOF) mass spectra were obtained
on a Perceptive Biosystems Voyager-DE STR system equipped
with a 337 nm nitrogen laser, using dithranol as the matrix. Mass
spectra were acquired in reflector mode at an acceleration voltage
of +20 kV. A Perkin Elmer DSC-7 was used to determine thermal
transitions. In all cases, heating and cooling scans were measured
Fig. 10 Principal d-spacing (d*) of 3G-3400 as
a function of
temperature.
upon heating) in linear block copolymers.17 This remarkable
contrast can be explained in terms of chain topologies. For the
columnar morphology of linear block copolymers, a longer coil
occupies the outer matrix, while a shorter block is located in the
inner core. In this arrangement, the longer coil adopts more
stable conformations at the expense of the conformational
energy of the shorter coil, which reduces the overall free energy.
In contrast, for the columnar structure of the dendron-coil
system in this study, the dendron block tends to be located in the
outer matrix, while the longer PEP coil is in the inner core
(Fig. 9). By considering the above-mentioned wedge angles, the
longer PEP coil of 3G-3400 can be thought to be more stretched
than the PEP coil of 3G-2400. This must be the reason for the
thermally induced transition from columnar to lamellar struc-
tures in 3G-3400. As the temperature increases, however, the
conformational energy of the stretched PEP coil in the columnar
phase becomes destabilized. In the end, the columnar
morphology has to be converted into the interdigitated lamellar
structure, which allows the PEP coil to be less stretched. This
argument can be confirmed by a plot of the principal d-spacing
(d*) as a function of temperature. The d* are the d(100) and d(001)
spacings for the columnar and lamellar structures, respectively.
As shown in Fig. 10, a sudden reduction in d* can be observed.
This spacing decrease at the transition indicates that highly
stretched PEP conformations change into less-stretched ones.
at a rate of 10 C minꢁ1. X-Ray scattering measurements were
ꢀ
performed in transmission mode with synchrotron radiation at
the 10C1 beam line of the Pohang Accelerator Laboratory
(PAL), Korea. The sample was held in an aluminium sample
holder with films on both sides. All dynamic mechanical spec-
troscopy (DMS) data were recorded on a Rheometrics Solid
Analyzer RSA 2 equipped with a shear sandwich geometry
(0.5 mm thickness). Dynamic mechanical spectrometer was
operated at small strain (1%) and low frequency (1 rad sꢁ1), and
temperature ramps were conducted at 2 ꢀC minꢁ1. Dynamic
elastic (G0) moduli were recorded as a function of temperature.
Conclusions
We prepared a series of dendron-coil block copolymers without
any structural defect by way of a divergent method. The dendritic
and linear blocks are hydrophilic polyether dendrons with 2nd
and 3rd generations and hydrophobic PEP coils with different coil
lengths, respectively. 2G-2400 with a 2nd generation exhibited
a PEO melting transition, while no PEO melting transition was
shown in the 3rd generation series, i.e. 3G-1400, 3G-2400, and 3G-
3400. Depending on the dendron generation and the dendron
volume fraction (f), diverse miscrophase-separated morphologies
were revealed due to the strong segregation tendency between the
PEO-like dendron and PEP blocks. The 2nd generation dendron-
coil, 2G-2400 with f ¼ 0.37, self-assembled into a lamellar
structure with an interdigitated dendron packing. For the 3rd
generation series, A15 micellar cubic, hexagonal columnar, and
lamellar morphologies were shown as the PEP coil length and/or
Synthesis
The general synthetic procedures are outlined in Schemes 1 and 2.
Compounds 2a–c. Hydroxyl-terminated poly(ethylene-alt-
propylene)s, PEP-OHs (1a–c), with three different number-
average molecular weights were synthesized according to
a literature method.18 Compounds 2a–c were synthesized using
the same procedure. A representative synthesis is described for
compound 2a. 1a (Mn ¼ 1430 g molꢁ1, 8.0 g, 5.6 mmol, 1.0
equiv.), 4-toluenesulfonyl chloride (5.34 g, 28 mmol, 5.0 equiv.)
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and pyridine (2.21 g, 28 mmol, 5.0 equiv.) were dissolved in
60 mL of anhydrous CH2Cl2. The reaction mixture was stirred
for 24 h at room temperature. The resulting mixture was treated
with 1 M HCl solution, and washed with brine. After removal of
the solvent under reduced pressure, the residue was purified
thrice by dissolution/precipitation with CH2Cl2/methanol to
(m, 5H), 6.17 (d, J ¼ 2.0 Hz, 2H), 6.11 (m, 7H), 4.97 (s, 2H), 4.05
(m, 16H), 3.81 (m, 16H), 3.68 (m, 32H), 3.58 (m, 8H), 2.96 (br,
4H). 13C-NMR (125 MHz, CDCl3, d, ppm): 160.4, 136.8, 128.5,
127.9, 127.5, 94.4, 72.5, 70.7, 70.3, 69.9, 69.6, 67.3, 61.6. Anal.
calcd for C61H92O25: C, 59.79; H, 7.57%, found: C, 59.73; H,
7.53%.
1
yield a colourless viscous oil (7.9 g, 90%). H NMR (CDCl3, d,
ppm): 0.85 (m, 60H, CH3), 0.97–1.45 (br, 140H, CH and CH2),
2.45 (s, 3H), 4.04 (t, 2H), 7.34 (d, 2H), 7.79 (d, 2H). Mw/Mn
(GPC) ¼ 1.08.
Compound 7. To a solution of compound 6 (3.1 g, 20 mmol)
in anhydrous CH3OH (35 mL) was added 10% Pd/C (40 wt%,
1.24 g). The reaction solution was degassed 5 times with
hydrogen gas and was stirred at room temperature for 24 hours
in the presence of H2. Then, the Pd catalyst was filtered off and
the filtrate was concentrated under reduced pressure. The
residue was purified by silica column chromatography
(CH2Cl2 : CH3OH ¼ 97 : 3 to 93 : 7) to yield a colourless oil
(2.3 g, 79%). 1H NMR (CDCl3, d, ppm): 6.09 (s, 7H), 6.03 (s, 2H),
4.05 (m, 16H), 3.80 (m, 16H), 3.69 (br, 32H), 3.60 (m, 8H), 2.89
(br, 4H). 13C NMR (CDCl3, d, ppm): 160.5, 160.4, 158.2, 95.3,
94.6, 93.8, 72.6, 70.8, 70.4, 69.8, 67.4, 61.8.
Compound 2b. Yield: 86%. 1H NMR (CDCl3, d, ppm): 0.85 (m,
102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 4.04 (t, 2H),
2.45 (s, 3H), 7.34 (d, 2H), 7.79 (d, 2H). Mw/Mn (GPC) ¼ 1.05.
Compound 2c. Yield: 91%. 1H NMR (CDCl3, d, ppm): 0.85 (m,
144H, CH3), 0.97–1.45 (br, 336H, CH and CH2), 2.45 (s, 3H),
4.04 (t, 2H), 7.34 (d, 2H), 7.79 (d, 2H). Mw/Mn (GPC) ¼ 1.03.
Compound 4. Compound 3 (ref. 19) (4.5 g, 9.37 mmol), 4-tol-
uenesulfonyl chloride (9.0 g, 47 mmol) and pyridine (3.7 g,
47 mmol) were dissolved in 60 mL of anhydrous CH2Cl2 at room
temperature. The reaction mixture was stirred for 3 days. After
removal of the solvent under reduced pressure, the resulting
mixture was dissolved with CH2Cl2 and treated with diluted HCl.
Then, the solution was washed with brine and concentrated
under reduced pressure. The residue was purified by silica
column chromatography (CH2Cl2 : ethyl acetate ¼ 9 : 1) to yield
a brownish oil (5.8 g, 78%). 1H NMR (CDCl3, d, ppm): 7.78 (d,
J ¼ 8.2 Hz, 4H), 7.32 (m, 5H), 7.31 (d, J ¼ 8.2 Hz, 4H), 6.16 (d,
J ¼ 1.6 Hz, 2H), 6.11 (d, J ¼ 1.6 Hz, 1H), 4.99 (s, 2H), 4.15 (m,
4H), 4.05 (m, 4H), 3.78 (m, 4H), 3.69 (m, 12H), 2.42 (s, 6H). 13C-
NMR (CDCl3, d, ppm): 160.5, 144.8, 136.8, 133.0, 129.9, 128.6,
128.0, 127.6, 94.6, 94.4, 70.9, 70.1, 69.8, 69.4, 68.8, 67.5, 21.8.
Compound 9. To a solution of poly(ethylene glycol) mono-
methyl ether (Mn ¼ 350 g molꢁ1, 30 g, 85.7 mmol, 1.0 equiv.) and
4-toluenesulfonyl chloride (49 g, 258 mmol, 3.0 equiv.) in
anhydrous CH2Cl2 (100 mL) was added pyridine (20.8 mL,
258 mmol, 3.0 equiv.), and the reaction mixture was stirred for
18 h at room temperature. The resulting mixture was treated
with diluted aqueous HCl solution and washed with brine. After
removal of the solvent under reduced pressure, the residue was
purified by silica-column chromatography (CH2Cl2 to
CH2Cl2 : CH3OH ¼ 8 : 1) to yield a colourless viscous oil (39 g,
90%). 1H NMR (CDCl3, d, ppm): 2.43 (s, 3H), 3.36 (s, 3H), 3.4–
3.8 (m, 26H), 4.14 (t, 2H), 7.32 (d, 2H), 7.78 (d, 2H). 13C NMR
(CDCl3, d, ppm): d 21.7, 59.0, 68.7, 69.3, 70.6, 71.9, 127.9, 129.8,
132.9, 144.7.
Compound 5. To a solution of compound 3 (9.6 g, 20 mmol) in
anhydrous CH3OH (45 mL) was added 10% Pd/C (20 wt%,
1.92 g), and the reaction solution was degassed for 5 times with
hydrogen. Then, the reaction mixture was stirred at room
temperature for 24 hours in the presence of H2. Then, the Pd
catalyst was filtered off and the filtrate was concentrated under
reduced pressure. The residue was purified by silica column
chromatography (ethyl acetate : CH3OH ¼ 19 : 1 to 8 : 1) to
yield a colourless oil (6.5 g, 83%). 1H NMR (CDCl3, d, ppm): 6.07
(s, 2H), 6.04 (s, 1H), 4.05 (m, 4H), 3.80 (m, 4H), 3.69 (br, 12H),
3.60 (m, 4H), 3.10 (br, 1H), 1.99 (br, 1H). 13C-NMR (CDCl3, d,
ppm): 160.5, 158.0, 95.6, 94.3, 72.5, 70.8, 70.4, 69.8, 67.5, 61.8.
Compound 10. To a solution of 5-benzyloxy resorcinol (8)
(2.3 g, 10.65 mmol, 1.0 equiv.) and tosylated PEO (9) (12.33 g,
24.5 mmol, 2.3 equiv.) in anhydrous acetonitrile (100 mL) were
added K2CO3 (4.41 g, 31.9 mmol, 3.0 equiv.) and KI (1.77 g,
10.64 mmol, 1.0 equiv.). The reaction mixture was stirred for 24 h
at 95 ꢀC under nitrogen. The resulting solution was cooled to
room temperature and concentrated under reduced pressure. The
resulting mixture was re-dissolved in CH2Cl2 and carefully
treated with diluted aqueous HCl solution. The organic layer was
then washed with brine and concentrated under reduced pres-
sure. The residue was purified by silica-column chromatography
(EtOAc : CH3OH ¼ 3 : 2) to yield a colourless viscous oil (5.8 g,
62%). 1H NMR (CDCl3, d, ppm): 3.35 (s, 6H), 3.52 (t, 4H), 3.55–
3.75 (m, 44H), 3.79 (t, 4H), 4.03 (t, 4H), 4.97 (s, 2H), 6.09 (s, 1H),
6.15 (s, 2H), 7.27–7.41 (m, 5H). 13C NMR (CDCl3, d, ppm): 59.1,
67.4, 69.7, 70.1, 70.6, 71.9, 94.4, 94.5, 127.5, 127.9, 128.5, 136.8,
160.5.
Compound 6. To a solution of 4 (2.9 g, 3.67 mmol) and 5 (3.2 g,
8.2 mmol) in anhydrous acetonitrile (40 mL) were added K2CO3
(1.78 g, 12.8 mmol) and KI (0.61 g, 3.67 mmol), and the reaction
ꢀ
mixture was stirred at 95 C for 30 hours under nitrogen. The
resulting solution was cooled to room temperature and concen-
trated under reduced pressure. The resulting mixture was dis-
solved with CH2Cl2, carefully treated with diluted HCl, washed
with brine, and concentrated under reduced pressure. The
residue was purified by silica column chromatography (ethyl
acetate : CH3OH ¼ 9 : 1 to 3 : 2) to yield a yellowish viscous
Synthesis of 11. To a solution of compound 10 (10.5 g, 11.93
mmol) in anhydrous CH3OH (50 mL) and CHCl3 (50 mL) was
added 10% Pd/C (20 wt%, 2.1 g). The reaction solution was
deoxygenated by five vacuum-refill cycles with hydrogen gas. The
reaction mixture was stirred for 38 h at room temperature in the
presence of H2 (30 psi). Then, the Pd catalyst was filtered off and
1
liquid (3.7 g, 82%). H NMR (500 MHz, CDCl3, d, ppm): 7.36
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the filtrate was concentrated under reduced pressure. The residue
was purified by silica-column chromatography (CH2Cl2 to
CH2Cl2 : CH3OH ¼ 19 : 1) to yield a colourless viscous oil (8.0 g,
85%). 1H NMR (CDCl3, d, ppm): 3.35 (s, 6H), 3.52 (t, 4H), 3.55–
3.75 (m, 44H), 3.79 (t, 4H), 4.03 (t, 4H), 5.99 (s, 1H), 6.05 (s, 2H),
7.53 (br, 1H). 13C NMR (CDCl3, d, ppm): 59.1, 67.4, 69.7, 70.6,
71.9, 93.7, 95.4, 158.4, 160.5.
ppm): 0.85 (m, 144H, CH3), 0.97–1.45 (br, 336H, CH and CH2),
2.58 (t, 4H), 3.61 (m, 8H), 3.71 (m, 32H), 3.84 (m, 16H), 3.89 (t,
2H), 4.07 (m, 16H), 6.08 (s, 4H), 6.11 (s, 5H). 13C NMR (CDCl3,
d, ppm): 19.9, 24.6, 33.0, 33.3, 37.7, 61.9, 67.5, 69.8, 70.6, 71.0,
72.7, 94.6, 160.5. Mw/Mn (GPC) ¼ 1.02.
Compounds 13 and 15a–c. Compounds 13 and 15a–c were
synthesized using the same procedure. A representative synthesis
is described for compound 15a. To a solution of 14a (1.34 g,
0.52 mmol, 1.0 equiv.) and 4-toluenesulfonyl chloride (1.97 g,
10.4 mmol, 20 equiv.) in anhydrous CH2Cl2 (60 mL) was added
pyridine (0.84 mL, 10.4 mmol, 20 equiv.). The reaction mixture
was stirred for 24 h at room temperature. The resulting mixture
was treated with diluted aqueous HCl solution and washed with
brine. After removal of the solvent under reduced pressure, the
residue was purified by flash silica-column chromatography
(CH2Cl2 : EtOAc ¼ 9 : 1 to 7 : 3) to yield a yellowish viscous
solid (1.34 g, 81%). Mw/Mn (GPC) ¼ 1.03. 1H NMR (CDCl3, d,
ppm): 0.85 (m, CH3), 0.97–1.45 (br, CH and CH2), 2.42 (s, 12H),
3.56–3.98 (m, 48H), 4.03 (m, 16H), 4.15 (t, 8H), 6.08 (s, 4H), 6.11
(s, 5H), 7.32 (d, 8H), 7.78 (d, 8H).
Compounds 12 and 14a–c. Compounds 12 and 14a–c were
synthesized using the similar procedure except for the stoichi-
ometry of reactants and purification. A representative synthesis
is described for compound 14a. To a solution of compound 2a
(1.97 g, 1.24 mmol, 2.0 equiv.), 7 (0.7 g, 0.62 mmol, 1.0 equiv.) in
anhydrous acetonitrile (7 mL) and THF (21 mL) were added
K2CO3 (256 mg, 1.85 mmol, 3.0 equiv.) and KI (205 mg,
1.23 mmol, 2.0 equiv.). The reaction mixture was stirred for 48 h
at 95 ꢀC under nitrogen. The resulting solution was cooled to
room temperature and concentrated under reduced pressure. The
resulting mixture was dissolved with CH2Cl2, carefully treated
with diluted aqueous HCl solution, and washed with brine. After
removal of the solvent under reduced pressure, the residue was
purified by silica-column chromatography (CH2Cl2 : CH3OH ¼
1
19 : 1) to yield a colourless viscous oil (1.42 g, 89%). H NMR
Compound 13. Yield: 92%. 1H NMR (CDCl3, d, ppm): 0.85 (m,
102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 2.42 (s, 6H),
3.56–3.98 (m, 12H), 4.03 (m, 4H), 4.15 (t, 4H), 6.08 (s, 3H), 7.32
(d, 4H), 7.78 (d, 4H). Mw/Mn (GPC) ¼ 1.03.
(CDCl3, d, ppm): 0.85 (m, CH3), 0.97–1.45 (br, CH and CH2),
2.58 (t, 4H), 3.61 (m, 8H), 3.71 (m, 32H), 3.84 (m, 16H), 3.89 (t,
2H), 4.07 (m, 16H), 6.08 (s, 4H), 6.11 (s, 5H). 13C NMR (CDCl3,
d, ppm): 19.9, 24.7, 32.9, 33.3, 37.6, 61.9, 67.5, 69.8, 70.5, 70.9,
72.7, 94.6, 160.6. Mw/Mn (GPC) ¼ 1.03.
1
Compound 15b. Yield: 55%. H NMR (CDCl3, d, ppm): 0.85
(m, 102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 2.42
(s, 12H), 3.56–3.98 (m, 48H), 4.03 (m, 16H), 4.15 (t, 8H),
6.08 (s, 4H), 6.09 (s, 5H), 7.32 (d, 8H), 7.78 (d, 8H). Mw/Mn
(GPC) ¼ 1.02.
Compound 12. Reaction conditions: compound 2b (5.4 g, 2.16
mmol, 1.0 equiv.), compound 5 (2.53 g, 6.48 mmol, 3.0 equiv.),
K2CO3 (1.35 g, 9.72 mmol, 4.5 equiv.), KI (360 mg, 2.16 mmol,
1.0 equiv.) in anhydrous acetonitrile (30 mL) and THF (60 mL)
ꢀ
1
Compound 15c. Yield: 66%. H NMR (CDCl3, d, ppm): 0.85
at 95 C for 48 h. Purification: a repetitive dissolution/precipi-
tation method with CH2Cl2/methanol. Yield: 96%. 1H NMR
(CDCl3, d, ppm): 0.85 (m, 102H, CH3), 0.97–1.45 (br, 238H, CH
and CH2), 2.58 (t, 2H), 3.61 (m, 4H), 3.71 (m, 12H), 3.84 (m, 4H),
3.89 (t, 2H), 4.07 (m, 4H), 6.09 (s, 2H), 6.13 (s, 1H). 13C NMR
(CDCl3, d, ppm): 19.9, 24.7, 33.0, 37.6, 61.9, 67.5, 69.8, 70.6,
71.0, 72.6, 113.1, 113.2, 160.5. Mw/Mn (GPC) ¼ 1.03.
(m, 102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 2.42
(s, 12H), 3.56–3.98 (m, 48H), 4.03 (m, 16H), 4.15 (t, 8H),
6.08 (s, 4H), 6.09 (s, 5H), 7.32 (d, 8H), 7.78 (d, 8H). Mw/Mn
(GPC) ¼ 1.02.
Dendron-coils. Dendron-coils were synthesized using the same
procedure. A representative synthesis is described for 3G-1400.
To a solution of 15a (1.27 g, 0.39 mmol, 1.0 equiv.) and 11
(1.88 g, 2.38 mmol, 6.0 equiv.) in anhydrous acetonitrile (13 mL)
and THF (32 mL) were added K2CO3 (495 mg, 3.57 mmol,
9.0 equiv.) and KI (132 mg, 0.79 mmol, 2.0 equiv.). The reaction
mixture was stirred for 48 h at 95 ꢀC under nitrogen environ-
ment. The resulting solution was cooled to room temperature
and concentrated under reduced pressure. The resulting mixture
was redissolved with CH2Cl2 and carefully treated with diluted
aqueous HCl solution. The organic layer was washed with brine.
After removal of the solvent under reduced pressure, the residue
was purified by flash silica-column chromatography
(CH2Cl2 : CH3OH ¼ 49 : 1 to 19 : 1) and a preparative GPC to
yield a yellowish viscous solid (1.47 g, 66%). 1H NMR (CDCl3, d,
ppm): 0.85 (m, 60H, CH3), 0.97–1.45 (br, 140H, CH and CH2),
3.37 (s, 24H), 3.53 (t, 16H), 3.60–3.79 (br, 232H), 3.82 (m, 40H),
4.05 (t, 40H), 6.08 (s, 21H). 13C NMR (CDCl3, d, ppm): 19.6,
24.4, 32.7, 37.5, 59.0, 67.3, 69.6, 70.5, 94.2, 160.4. Mw/Mn
(GPC) ¼ 1.02.
Compound 14b. Reaction conditions: compound 2b (1.91 g, 0.75
mmol, 1.0 equiv.), compound 7 (1.27 g, 1.12 mmol, 1.5 equiv.),
K2CO3 (467 mg, 3.38 mmol, 4.5 equiv.), KI (104 mg, 0.75 mmol,
1.0 equiv.) in anhydrous acetonitrile (7 mL) and THF (28 mL) at
95 ꢀC for 48 h. Purification: a repetitive dissolution/precipitation
method with CH2Cl2/methanol. Yield: 92%. 1H NMR (CDCl3, d,
ppm): 0.85 (m, 102H, CH3), 0.97–1.45 (br, 238H, CH and CH2),
2.58 (t, 4H), 3.61 (m, 8H), 3.71 (m, 32H), 3.84 (m, 16H), 3.89 (t,
2H), 4.07 (m, 16H), 6.08 (s, 4H), 6.11 (s, 5H). 13C NMR (CDCl3,
d, ppm): 20.0, 24.7, 33.0, 33.3, 37.6, 61.9, 67.5, 69.8, 70.6, 71.0,
72.7, 94.6, 160.5. Mw/Mn (GPC) ¼ 1.02.
Compound 14c. Reaction conditions: compound 2c (1.89 g, 0.54
mmol, 1.0 equiv.), compound 7 (0.76 g, 0.67 mmol, 1.24 equiv.),
K2CO3 (277 mg, 2.0 mmol, 3.9 equiv.), KI (91 mg, 0.54 mmol,
1.0 equiv.) in anhydrous acetonitrile (7 mL) and THF (35 mL) at
95 ꢀC for 48 h. Purification: a repetitive dissolution/precipitation
method with CH2Cl2/methanol. Yield: 74%. 1H NMR (CDCl3, d,
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1
2G-2400. Yield: 71%. H NMR (CDCl3, d, ppm): 0.85 (m,
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102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 3.37 (s, 12H),
3.53 (t, 8H), 3.60–3.79 (br, 112H), 3.82 (m, 16H), 4.05 (t, 16H),
6.08 (s, 9H). 13C NMR (CDCl3, d, ppm): 19.8, 24.5, 32.8, 37.5,
59.0, 67.4, 69.7, 70.7, 71.9, 94.3, 160.5. Mw/Mn (GPC) ¼ 1.02.
1
3G-2400. Yield: 62%. H NMR (CDCl3, d, ppm): 0.85 (m,
102H, CH3), 0.97–1.45 (br, 238H, CH and CH2), 3.37 (s, 24H),
3.53 (t, 16H), 3.60–3.79 (br, 232H), 3.82 (m, 40H), 4.05 (t, 40H),
6.08 (s, 21H). 13C NMR (CDCl3, d, ppm): 19.6, 24.4, 32.7, 37.5,
59.0, 67.3, 69.6, 70.5, 94.2, 160.4. Mw/Mn (GPC) ¼ 1.02.
€
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1
3G-3400. Yield: 74%. H NMR (CDCl3, d, ppm): 0.85 (m,
144H, CH3), 0.97–1.45 (br, 336H, CH and CH2), 3.37 (s, 24H),
3.53 (t, 16H), 3.60–3.79 (br, 232H), 3.82 (m, 40H), 4.05 (t, 40H),
6.08 (s, 21H). 13C NMR (CDCl3, d, ppm): 19.7, 24.4, 32.7, 37.5,
59.0, 67.3, 69.6, 70.6, 94.2, 160.4. Mw/Mn (GPC) ¼ 1.02.
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Acknowledgements
This work was supported by the Core Research Program (2009-
0084501) through the National Research Foundation (NRF)
funded by the Ministry of Education, Science and Technology
(MEST), Republic of Korea. We acknowledge the Pohang
Accelerator Laboratory (Beamline 10C1), Korea. We thank
Prof. Jin Kon Kim at Pohang University of Science and Tech-
nology (POSTECH) for dynamic mechanical spectroscopy
measurements.
€
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3428 | Soft Matter, 2012, 8, 3419–3428
This journal is ª The Royal Society of Chemistry 2012