Hyperbranched pyridylphenylene polymers based on the first-generation dendrimer as a multifunctional monomer

Article abstract of DOI:10.1039/c5ra16847c

An A₆ + B₂ approach was applied for the first time to synthesize novel hyperbranched pyridylphenylene polymers by Diels-Alder cyclocondensation reaction. For this, the first-generation pyridylphenylene dendrimer with six ethynyl functionalities (A₆) was used as a branching core for the molecule growth. The phenyl-substituted bis(cyclopentadienone)s (B₂) of different structures were used as co-monomer in the reaction. A careful choice of reaction conditions allowed us to obtain high molecular weight polymers without undesirable gelation. The molecular weight of the polymers varied in the range of 10800-80100 with a polydispersity degree of 1.69 to 4.07 according to SEC analysis. The ¹H and inverse-gated decoupling ¹³C NMR combined with heteronuclear single quantum correlation and heteronuclear multiple bond correlation measurements were used to estimate the branching degree of the polymers synthesized.

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Hyperbranchedpyridylphenylene polymers based on the first
generation dendrimer as a multifunctional monomer
a
a
a
b
a
a
Received 00th January 20xx,
Accepted 00th January 20xx
N. V. Kuchkina, M. S. Zinatullina, E. S. Serkova, P. S. Vlasov, A. S. Peregudov andZ. B. Shifrina †
An A
Alder cyclocondensation reaction. For this, the pyridylphenylene dendrimer of the first generation with six ethynyl
functionalities (A ) was used as a branching core for the molecule growth. The phenyl-substituted bis(cyclopentadienone)s
) of different structures were used as a co-monomer in the reaction. A careful choice of reaction conditions allowed us
6 2
+B approach was applied for the first time to synthesize novel hyperbranched pyridylphenylene polymers by Diels-
DOI: 10.1039/x0xx00000x
6
www.rsc.org/
(B
2
to obtain high molecular weight polymers without undesirable gelation. The molecular weight of the polymers varied in
1
the range of 10-80 kDa with polydispersity degree of 1.69 to 4.07 according to SEC analysis. The H and inverse-gated
1
3
decoupling C NMR combined with Heteronuclear Single Quantum Correlation and Heteronuclear Multiple Bond
Correlation measurements were used to estimate a branching degree of the polymers synthesized.
2
polyurethanes and polycarbosilanes were synthesized by
2
23
Introduction
polycondensation of AB monomers. Various hyperbranched
n
2
4-26
polyacrylates,
hyperbranched
azobenzene-containing
28
Hyperbranched
polymers(HBP)
received
considerable
2
polymers, hyperbranched glycopolymers were prepared via
7
attention of academia researchers and industry in the last
twenty years. They arecharacterized by higher solubility
compared to that of linear polymers, low viscosity, and a
2
9,
30
SCVP.
Hyperbranched
3
polyamines,
33, 34
and polyesters
hyperbranched
1, 32
polyethers
were synthesized through
1
-5
SCROP. Hyperbranched polyesters with epoxy or hydroxyl end
36
generous amount of functional groups. Typically, the HBP
are obtained by an one-pot procedure, which limits the ability
to control the molecular weight and leads to "heterogeneous"
products with a broad molecular weight distribution and
differences inbranchingcompared todendrimers which are
monodisperse macromoleculesin regard of both size and
3
5
groups and hyperbranched polysiloxanes were synthesized
through PTP. DMM is based on the use of a pair of monomers
n 2
such as A (n≥3) andB . For example, hyperbranched aromatic
3
7
polyamide, pyrimidine-based hyperbranched polyimides,
38
3
9
hyperbranched polybenzoxazole
and hyperbranched
were synthesied by +B
3 3
and A +B methods were also used
4
0
6
polyacenaphthenequinones
A
3
2
structure. The main advantages of HBPover dendrimers area
4
1-43
44
approach. The A
4
+B
2
facile synthesis and alow cost of the final product. HBP have
7
-9
10
been applied in catalysis, opto-electronic materials, drug
for the synthesis of hyperbranched polymers.
1
1-13
A wide assortment of organic reactions is known for
4
release
etc.There are two scenariosfor the synthesis of
5-51
construction of HB polymers.
Among them the Diels-Alder
HBP:the single-monomer methodology (SMM) and the double-
1
monomer methodology (DMM). SMM is based on the use of
reaction has been successfully used for the synthesis of HB
5
2, 53
2 3 2
polyphenylenes using the AB or A +B approaches.
AB monomer type (n≥2).According to the reaction mechanism,
n
The main challenge in the HBP synthesisis to obtain the perfect
dendritic polymer structure by aone-pot procedure; therefore,
the known methods of synthesis are constantly improving. It
was proposed to combine the advantages of dendrimers and
hyperbranched polymers. In this way the synthesis is becoming
4- much easier than that of high generation dendrimers and the
21 polymer defects are becoming less pronounced than those of
HBP synthesized via a routine monomer method. Dendrons
have been used to design branched polymers, named
theSMM strategy includes at least four approaches:
(
1)polycondensation of ABn monomers; (2) self-condensing
vinyl polymerization (SCVP); (3) self-condensing ring-
openingpolymerization (SCROP); (4) proton-transfer
polymerization (PTP). A broad range of hyperbranched
1
polymers,
1
including
17 18
polyethers, polyesters, polyamides,
hyperbranchedpolyphenylenes,
19, 20
6
polycarbonates,
5
4
"
dendronized polymers". Usually it is a linear polymer with
5
4, 55
dendritic units in side chains.
6 2
In this paper for the first time we report the A +B approach
based on a Diels-Alder polycycloaddition of the first generation
six-functional pyridine containing polyphenylene dendrimer
with the aromatic bis(cyclopentadienone)s of different
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-1
structures, leading to novel hyperbranchedpolyphenylenes monomer concentrations of 0.01 – 0.05mol·L , at various
with pyridine moieties. The structure of the HB polymers molar ratios of monomers. The amounts of reagents employed
synthesized was characterized by NMR spectroscopy, while are given in Table 1. In typical procedure, 0.050 g (0.073 mmol)
molecular weight and polydispersity degree were evaluated by of
size exclusion chromatography (SEC). The branching degree of dien-1-one) (B
the polymers synthesized was unambiguously defined by a dendrimer G1-6N-ethyn (A
3,3'-(1,4-phenylene)-bis-(2,4,5-triphenylcyclopenta-2,4-
) and 0.1 g (0.073 mmol) of first generation
) were dissolved in 14.6mL of
2
6
combination of 1D and 2D NMR techniques.
diphenyl ether at 160°C (Table 1, entry 1, a). All reactions were
carried out for 6.5 hrs, and then the mixture was allowed to
cool. The cold reaction mixture was diluted with chloroform
and added dropwise into ethanol. A white precipitate was
filtered, washed with ethanol and reprecipitated twice from
chloroform into ethanol. Polymers were dried in vacuum at
Experimental section
Materials. 1,3,5-triethynylbenzene (98%), Bu
4
NF (1M solution
in
tetrahydrofuran),
N-methylpyrrolidone (99%),
1
20°C.
tetrahydrofuran (anhydrous, 99.9%), diphenyl ether (99%), o-
xylene (anhydrous, 97%) were purchased from Aldrich and
used as received.
Table 1. The synthesis parameters for polymer preparations
a
1
13
N
1
A6:B2
A6, g
B2, g
B2
C ,
Measurements. H NMR and C NMR spectra were recorded
-
1
(
molar
(mmol) (mmol)
mol·L
on Avance-IIIHD-500MHz NMR spectrometer operating at
1
13
ratio)
5
00.13 MHz for H and at 125.76 MHz for C. Chemical shifts
are given in parts per million (ppm), using the solvent signal as
a reference. CD Cl was used as solvent for all standard 1D and
D NMR measurements [δ( H)=5.35 ppm; δ( C)=53.4 ppm].
D spectra: Heteronuclear Single Quantum Correlation(HSQC)
a)0.010
b)0.020
c)0.033
d)0.050
a)0.010
b) 0.020
c)0.033
d)0.050
a)0.050
b)0.033
a)0.010
b)0.033
c)0.050
a)0.033
b)0.050
0
.100
0.050
1:1
2
2
(
0.073)
(0.073)
1
13
2
2
2
and Heteronuclear Multiple Bond Correlation (HMBC) were
recorded by using the standard pulse sequences of the Bruker
0
.100
0.075
1
:1.5
(0.073)
(0.109)
1
1
3
software. The inverse-gated decoupling C NMR spectra were
obtained at 25°C, 30° pulse angel, inverse-gated decoupling
with 5.0 s delay, and 5,000 scans.
0
.100
0.101
3
4
1:2
1:3
(0.073)
(0.146)
Size-exclusion chromatography (SEC) analyses were carried out
using chromatograph Shimadzu LC-20AD equipped with TSKgel
G5000HHR 7.8 mm×30 cm (Tosoh Bioscience) and with TSKgel
HHR-L. Detection was achieved with refractive index detector.
SEC was performed in tetrahydrofuran at a flow rate of 1.0
mL/min with polystyrene as a standard.
0
.100
0.151
(0.073)
(0.219)
5
6
0.100
0.057
1
:1
(0.073)
.100
(0.073)
a)0.010
b)0.020
c)0.050
a)0.01
0
0.085
The intrinsic viscosity [η] measurements were performed with
an Ubbelohde viscometer at 25°C in N-methylpyrrolidone
1:1.5
1:2
2
(0.073)
(0.109)
(NMP). The samples were dissolved at room temperature.
7
8
0.100
0.114
(0.073)
(0.146)
b)0.02
Mass spectral analysis was carried out on the Bruker Biflex III
MALDI-TOF instruments. MALDI-TOF mass spectra were
a)0.010
b)0.033
c)0.050
a)0.010
b)0.020
c)0.033
d)0.050
a)0.01
0
.100
0.058
measured by using
a
337 nm nitrogen laser and
1:1
(0.073)
(0.073)
tetracyanoquinodimethane (TCNQ) as a matrix.
Synthetic procedures. Synthesis of monomers. 3,3'-(1,4-
9
Phenylene)bis(2,4,5-triphenylcyclopenta-2,4-dien-1-one)
,3’-(oxydi-1,4-phenylene)bis(2,4,5-triphenylcyclopenta-2,4-
dien-1-one) ), 3,3’-(carbonyldi-1,4-phenylene)-bis(2,4,5-
triphenylcyclopenta-2,4-dien-1-one) (Scheme 1) were
synthesized according to procedure described in paper.
First generation dendrimer G1-6N-(ethyn) ) (Scheme 1) was
synthesized according to procedure described by us
(
1
),
0.100
0.087
1
:1.5
(0.073)
(0.109)
3
3
(
2
1
0
1
1:2
0.100
0.116
(3)
5
6
(0.073)
(0.146)
b)0.02
1
a)0.010
b)0.033
c)0.050
6
(
4
0
.100
0.073)
0.174
1
:3
(
(0.219)
5
7
elsewhere.
G1-6N-(ethyn)
1
: H NMR spectrum (500 MHz, CD
a
6
2
Cl
2
): 8.64 (d,
6 2
total concentration of monomers A and B
3
4
1
4
H, PyH), 8.02 (d, 3H, PyH), 7.81 (s, 3H, ArH), 7.45 -6.55 (m,
5H, ArH), 3.01, 2.97 (2s, 6H, acetylenes). MALDI-TOF, m/e:
370 (M+, calcd. 1369.66). Elem. anal. found, %: C 88.65; H Results and discussion
, %: C 89.45; H 4.42; N 6.14.
60 6
.35; N 6.05. Calcd. for C102H N
Polymer synthesis
Hyperbranched aromatic polymers were synthesized by a
Diels-Alder reaction using an A +B approach. For this, the
Synthesis of hyperbranched pyridylphenylene polymers. All
procedures were performed using a Schlenk flask under an
argon atmosphere in diphenyl ether at 160°C using total
6
2
2
| J. Name., 2012, 00, 1-3
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PleaseRd So Cn oA t da vd aj un s ct ems argins
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DOI: 10.1039/C5RA16847C
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ARTICLE
pyridylphenylene dendrimer of the first generation with six molecular weight 40300 (Table 2, polymer 10). At higher
terminal acetylene functionalities -monomer A - was used as a concentrations the gelation was observed for the polymers
branching point for the molecule growth (Scheme 1, (Table 2, polymers and ). A further decrease of the
compound ). Bis(cyclopentadienone)s (B of different concentration led to the polymer molecular weight drop at the
structures (Scheme 1, compounds 1, 2, and 3) were used as a same monomer ratio (Table 2, polymer 11).
second monomer in the reaction. Dendrimer G1-6N-ethyn ( At the equimolar monomer ratio the soluble polymers were
was synthesized according to the protocol described by us prepared at the total monomer concentration of 0.033 mol·L
6
8
9
4
2
)
4)
-1
5
7
previously.
obtained by the Knoevenagel condensation of bis(
with two-fold molar amounts of diphenylacetone according to of the polymers as well.
The aromatic bis(cyclopentadienone)s were and below (Table 2, polymers 13, 14, and 15). Here the drop of
͕
-diketones) the monomer concentrations led to lower molecular weights
5
6
the procedure described in ref. . In this way 3,3'-(1,4- Based on the above observations we determined that the
phenylene)bis(2,4,5-triphenylcyclopenta-2,4-dien-1-one)
(
1
), monomer concentration dramatically effects the soluble
3,3’-(oxydi-1,4-phenylene)-bis(2,4,5-triphenylcyclopenta-2,4- polymer formation. Moreover, the effect is more pronounced
2 6
dien-1-one) (2) and 3,3’-(carbonyldi-1,4-phenylene)-bis(2,4,5- for the high B :A monomer ratio. In some cases, the soluble
triphenylcyclo-penta-2,4-dien-1-one) (
3) were synthesized.
polymers were obtained only when the reaction time was
reduced (Table 2, polymer 4 and 7).
Using the above findings we synthesized the polymers based
on monomers A6 and B2 (compounds (2) and (3), Scheme 1)
having bridging groups. At the monomer ratio 1:1, the
polymers with higher molecular weights were obtained at
-1
C
total= 0.033 mol·L (Table 2, polymers 20 and 25) as compared
to that based on monomer 1 (polymer 13). This effect can be
ascribed to a more flexible structure of B monomers,
providing the favourable polymer growth due to lower steric
constraints. At the same time, at a higher B content
:B =1:2 or 1:1.5) the soluble polymers were obtained only
at Ctotal= 0.01mol·L (Table 2, polymers 17
both B monomers.
According to SEC the highest molecular weight polymer
80100) was obtained by reacting of 3,3'- (carbonyl-di-1,4-
phenylene)-bis(2,4,5-triphenylcyclopenta-2,4-dien-1-one)
with G1-6N-ethyn ( ) (Table 2, polymer 25), probably due to
the higher reactivity of the compared with and 2.
All polymers showed good solubility in common organic
solvents such as chloroform, dichloromethane,
2
2
(
A
6
2
-
1
,
19, 22, and 24 )for
2
Scheme1.Synthesis of hyperbranchedpyridylphenylene polymers
(
(3)
The polycyclocondensation of multifunctional monomers may
lead to rapid undesirable gelation which can be controlled by
reaction parameters such as temperature, reaction time,
concentration of monomers, etc. To establish dependences of
the reaction parameters on the polymer structure, the Diels-
Alder polycyclocondensation was carried out using a pair of
4
3
1
tetrahydrofuran, toluene, benzene, and N-methyl-2-
pyrrolidone.
monomers:
B ,
2
3,3'-(1,4-phenylene)-bis(2,4,5-triphenyl-
) and A , G1-6N-ethyn ( ). Since
The intrinsic viscosity ([ꢀ]) of the polymers synthesized
cyclopenta-2,4-dien-1-one) (
1
4
6
measured in N-MP at 25 °C was rather low (Table 2) which is
characteristic of hyperbranched polymers. It is well known that
the intrinsic viscosities of the hyperbranched polymers are
much lower compared to that of linear polymer of the same
we observed gelation at 180°C already in one hour, the
synthesis of the polypyridylphenylenes was performed at
160°C for 6.5 hrs. The molar ratios of the A :B monomers
6 2
employed were 1:1, 1:1.5, 1:2, and 1:3. When the A :B molar
6
2
molecular weight. For linear polymers in a good solvent [ꢀ]
increases monotonically with a molecular weight following the
ratio was 1:3, complete gelation occurred at all monomer
-
1
concentrations (0.010-0.050 mol·L ) (Table 2, polymers
and ). However, when the reaction time was decreased to 3
hrs, a soluble polymer with a molecular weight 23500
according to SEC) was obtained, at the total monomer
1, 2,
5
8
Mark-Houwink equation with α=0.7. On the other hand,
dendrimers and hyperbranched polymers demonstrate
3
unusual viscosity behaviour. For example, [ꢀ] of some
dendrimers increases initially and then decreases after a
(
-1
concentration of 0.033 mol·L (Table 2, polymer
4).The same
5
9
maximum is reached at a certain generation. The intrinsic
viscosity of star and hyperbranched polymers generally has a
lesser dependence on the molecular weight than that of
trend was observed for the A :B molar ratio of 1:2. The
6
2
gelation has occurred at the concentrations of 0.050 and 0.033
-
1
mol·L (Table 2, polymers
5 and 6), while a soluble polymer of
6
0, 61
corresponding linear polymers.
on the molecular weight was also observed for the polymers
synthesized (Table 2). The [ ] values of these polymers are
A small dependence of [ꢀ]
the molecular weight 17900 was prepared, when the reaction
time was decreased to 3 hrs, at the total monomer
-
1
ꢀ
concentration of 0.033 mol·L (Table 2, polymer
7).
quite low and the increase of the molecular weight of the
At the A :B =1:1.5 molar ratio the soluble polymer was
6
2
-1
polymers obtained at the same molar concentrations but at
obtained at Ctotal= 0.02 mol·L after the 6.5 h reaction with the
the different molar ratio of monomers (compare pairs
4 and 7,
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6
3
1
0
and 14
significant change in
macromolecules of a compact shape.
,
17 and 19
,
22 and 24, Table 2) does not lead to a assessment of the DB. Typically, the DB of polymers is
[
ꢀ
], indicating the formation of determined by comparing the NMR spectra of suitable model
6
2
64, 65
compounds and a polymer.
For this, model compounds
It is worth noting that the average yields of the polymers are in mimicking branched, linear, and terminal polymer fragments
the range of 63-79% (Table 2). We assume that these should be synthesized. In order to determine the DB of
comparatively low yields can be because monomer A
fully participate in the reaction with B due to lower solubility synthesize partially substituted monomer A
or slow solubilization of the former. Indeed, during the work- containing from one to five terminal acetylene groups (Figure
up procedure A is isolated in practically all cases. This effect is S1, the Electronic Supplementary Information, ESI). While
especially pronounced for polymers obtained at the 1:1 molar mono- or disubstituted monomers A (Figure S1, a and b,
6
does not hyperbranched polypyridylphenylenes it was necessary to
2
6
, i.e., models
6
6
ratio. Instead of expected predominantly linear polymers, a respectively) were obtained with a high yield and purity, the
branched polymers are formed apparently as a result of further substitution (Figure S1, c, d, and e) led to the mixture
disturbance of the initial monomer loading ratio.
of differently substituted compounds that could not be
More accurate assessment of the polymer branching has been separated by column chromatography. Therefore, in this study
obtained from NMR data.
we used the NMR spectroscopy to estimate the relative
amount of free (unreacted) functional groups in the repeating
unit of the polymers synthesized that is directly related to the
branching degree of the polymer.
Table 2. The synthesis conditions and characterization data of different hyperbranched
pyridylphenylene polymers
A
6
:B
2
(
B
2
b
c
-3
Yield
%
As a proof of concept, we demonstrated the effect of the
molar ratio of monomers on the branching of the polymers
Poly-
С ,
[η] ,
M
w
×10 ,
a
molarr
atio)
1:3
-1
-1
-1
M
w
/M
n
mer
mol·L
dL·g
g·mol
synthesized, for the pair of monomers A
6
and B
10 and 13 obtained
6 2
at the molar ratios of monomers A :B =1:3, 1:2, 1:1.5 and 1:1,
2
(compound 1)
d
1
0.050
0.033
0.010
0.033
0.050
0.033
0.033
0.050
0.033
0.020
0.010
0.050
0.033
0.020
0.010
0.02
-
-
-
-
-
-
-
(Table 2). For this study, the polymers 4, 7,
d
2
1:3
-
-
-
-
d
3
1:3
-
e
respectively, were chosen.
1
All H NMR spectra of polymers
4
1:3
0.32
-
23.5
-
3.10
-
75
-
d
4,
7,
10, and 13 (Figure 1a and
5
1:2
d
Figure S2, a-c in ESI) show three groups of signals. The signals
at 8.61 (or 8.64) and 8.07 (or 8.01) ppm belong to α-protons
H(1) and H(1’) of nonequivalent pyridine moieties of the
polymer, the signals at 3.08 (or 3.02), 3.04 (or 2.99), and 3.00
6
1:2
-
-
-
-
e
7
1:2
0.30
-
17.9
-
2.15
-
77
-
d
8
1:1.5
1:1.5
1:1.5
1:1.5
1:1
1
d
9
-
-
-
-
(or 2.95) ppm correspond to the protons H(2) of the terminal
1
1
0
1
0.46
0.1
-
40.3
13.4
-
4.07
2.44
-
78
75
-
acetylene groups, while signals in the range of 7.7-6.25 ppm
are assigned to other aromatic protons of the polymer.
According to the integral ratio of the signals of the acetylene
protons and α-protons of pyridine fragments their ratio in
d
1
2
1
1
1
3
4
5
1:1
0.72
0.49
0.13
-
33.7
22.1
10.8
-
3.27
2.11
2.15
-
69
68
66
-
1:1
1:1
polymer 13 (A
2.34:6, in polymer
(A :B =1:3) it is 1.23:6. Therefore, an increase of the monomer
6
:B
2
=1:1) is 3:6, in polymer 10 (A
6 2
:B =1:1.5) it is
d
1
6
1:2
7
(A :B =1:2) it is 2:6, and in polymer 4
6
2
1
7
1:2
0.01
0.11
-
29.1
-
1.84
-
78
-
6
2
d
1
8
1:1.5
1:1.5
1:1
2
3
0.02
B2 content led to the decrease of the number of the unreacted
acetylene groups in polymers. Because every repeating unit of
polypyridylphenylenes contains six pyridyl moieties that come
1
2
9
0
0.01
0.12
0.29
-
17.1
40.3
-
1.69
2.94
-
79
63
-
0.033
0.02
d
2
1
1:2
6
from the branching monomer A , the ratio of the pyridyl
2
2
2
2
2
3
4
5
1:2
0.01
0.19
-
35.1
-
2.69
-
69
-
fragments and unreacted acetylene groups (which did not
participate in the growth of macromolecules) is directly related
to the branching of the polymers. Ideally, if the polymer
growth occurs in six directions (this might be accomplished at
A :B =1:3), the structure of the repeating unit of the polymer
1:1.5
1:1.5
1:1
0.02
0.01
0.17
0.37
18.4
80.1
1.85
3.90
70
66
0.033
a
syntheses were carried out in diphenyl ether at 160°Сfor 6.5 hrs
6
2
would be similar to the structure shown in Figure 2. In this
case, no signal of acetylene protons should be observed int he
b
total concentration of monomers A
6
and B
2
c
1
intrinsic viscosity of the polymer solution in NMP at 25°С
H NMR spectrum, and the branching degree should be 100%.
However, as it is discussed above, in the most branched
d
insoluble polymer
polymer
1.23:6, revealing that the macromolecule growth occurred
mostly in five directions (Figure 1) . Accordingly, for polymer
4 the ratio of the acetylene and pyridine fragments is
e
synthesis was carried out in diphenyl ether at 160°С for 3 hrs
7,
NMR analyses of polymers
macromolecule growth occurred mostly in four directions, for
polymer 10, in three or four directions, and for polymer 13, in
three directions, respectively. Here, it should be noted that the
NMR signal ratio is an average value and a mixture of different
The degree of branching (DB) is the most important
characteristic of hyperbranched polymers. NMR spectroscopy
has been proven to be the most powerful tool for the direct
4
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DOI: 10.1039/C5RA16847C
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ARTICLE
Figure 2. Proposed ideal structure of the repeating unit of the polymers.
possible repeating units may coexist in polymers (see Figures
S3-S6, ESI for illustration).
For more accurate signal assignment, we chose polymer 25
with highest molecular weight and combined 1D and 2D NMR
techniques. All signal assignments in the inverse-gated
1
3
decoupling С NMR spectrum of the polymer (Figure 3a) are
made with the help HSQC and HMBC spectra (Figures S7-
S10,ESI). The spectrum contains the signal at 196.4 ppm which
corresponds to the carbon C(3) of the carbonyl group in the
benzophenone unit of the polymer. The signal at 159.4 ppm is
assigned to quaternary carbon atoms C(4) and C(5) in the
pyridine fragments of the polymer. The signals at 149.6 and
1
48.9 ppm refer to the carbon atoms C(1, 1’) located at the α-
position of the pyridine fragments. The signals at 122.1 and
21.5 ppm are ascribed to the carbon atoms C(6) and C(7) in
1
pyridine, while the signals at 120.2 and 119.7 ppm refer to the
carbon atoms C(8) in phenyl rings bound to the acetylene
group of the polymer. The signals at 83.9 and 77.5 ppm refer
to the quaternary carbon atoms C(9) and the carbon atoms
C(2) of the terminal acetylene groups, respectively.
a
CD Cl
2
2
13
N 1'
Ñ NMR (CD
Cl
, 125 MHz)
2
2
1'
1
1
N
N
N
N 1'
2
N
1
N
1'
1
N
'
1
Ñ(3)
Ñ(4) Ñ(1)
Ñ(5) Ñ(1')
Ñ(6) Ñ(8)
Ñ(7)
Ñ(2)
Ñ(9)
1
N
2
2
N
N 1'
N
1
1'
N
1
N
'
1
1
N
N
1.11
5.72 6.04
6.00 3.12
120
3.19 3.04
80
N 1'
N
180
160
140
100
60
40
1'
2
1
N
Chemical Shift (ppm)
1
N
'
1
2
a
1
N
N
N 1'
N
1
b
1
Figure 1. H NMR spectrum (a) and the proposed structure of the polymer
4
(b). For polymers 7, 10, and 13, see ESI.
R
1
R:
O
O
2
3
N
b
N
N
N
N
13
Figure 3. C NMR spectrum (a) and the proposed structure of polymer 25
b).
N
(
R
R
Because the signal of a carbonyl group of cyclopentadienone
unit at about 200 ppm is not detected (signal at 196.4 ppm
2
belongs to the bridging carbonyl group of B ) and considering
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ARTICLE
Journal Name
the functionality of the monomers and the monomer loading The approach developed paves the way for the one-pot
ratio, we concluded that there are no unreacted functional synthesis of well-defined polymers bearing perfect dendritic
2
groups from the B monomer in polymer 25. To allow for fragments in the polymer backbone.
1
3
13
accurate integration of the C signals, the C spectrum was
recorded with proton decoupling only during the acquisition
period to avoid non-uniform enhancement of carbon signals
from proton (Nuclear Overhauser Effect). Thus, the integration
of the aromatic and acetylene carbon signals in the spectrum
in Figure 3a allows us to estimate the ratio of the terminal
acetylene and pyridine fragments in the polymer as 3:6. The
Acknowledgements
Financial support from Russian Foundation for Basic Research,
(grant No. 14-03-00876_a) and the European Community's 7th
Framework Programme for Research and Technological
Development under grant agreement no. 604296 (BIOGO for
Production) are gratefully acknowledged.
1
same ratio was obtained from the H NMR data (see Figure
S11, ESI).
The special attention is paid to the splitting in a "triplet" of the
signal at 3.00 ppm.The HSQC spectrum (Figure S8, ESI) Notes and references
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