Telechelic polynorbornenes with hydrogen bonding moieties by direct end capping of living chains

Article abstract of DOI:10.1002/pola.24362

We present two novel symmetric olefins bearing hydrogen bonding moieties for the direct capping of living ring opening metathesis polymerization-chains using Grubbs catalyst 1st-and 3rd-generation. The symmetric olefins are generated via homo metathesis of the corresponding α-olefins under aid of microwave irradiation and are used to prepare polynorbornene-chains (M _n = 4,000-10,000 g/mol, M_w/M_n = 1.1-1.4) bearing barbiturate and thymine-moieties. A qualitative and quantitative analysis of the generated polymers is done via MALDI-TOF MS proving the introduction of hydrogen-bonding moieties into the polymer chain and revealing the strong dependence of the desorption on the chemical structure of the different polymer species and high efficiencies for the end group introduction (90-99%). The efficiency of this process depends strongly on the reaction time and the equivalents of terminating agent with respect to the living end. The best results for the end group introduction are achieved by reacting the living chains with an excess of the terminating agent (5-20 equiv) for 100 h.

Full text of DOI:10.1002/pola.24362

Telechelic Polynorbornenes with Hydrogen Bonding Moieties by Direct
End Capping of Living Chains
STEFFEN KURZHALS, WOLFGANG H. BINDER
Martin-Luther-Universit a¨ t Halle-Wittenberg, Naturwissenschaftliche Fakult a¨ t II Chemie u. Physik, Inst. f. Chemie,
Lehrstuhl f u¨ r Makromolekulare Chemie, von Danckelmann Platz 4, D-06120 Halle/Saale, Germany
Received 27 August 2010; accepted 27 August 2010
DOI: 10.1002/pola.24362
Published online 15 October 2010 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: We present two novel symmetric olefins bearing
hydrogen bonding moieties for the direct capping of living ring
opening metathesis polymerization-chains using Grubbs cata-
lyst 1st- and 3rd-generation. The symmetric olefins are gener-
ated via homo metathesis of the corresponding a-olefins under
aid of microwave irradiation and are used to prepare polynor-
different polymer species and high efficiencies for the end
group introduction (90–99%). The efficiency of this process
depends strongly on the reaction time and the equivalents of
terminating agent with respect to the living end. The best
results for the end group introduction are achieved by reacting
the living chains with an excess of the terminating agent (5–20
equiv) for 100 h. VC 2010 Wiley Periodicals, Inc. J Polym Sci
bornene-chains (M
n
¼ 4,000–10,000 g/mol, M
w
/M
n
¼ 1.1–1.4)
bearing barbiturate and thymine-moieties. A qualitative and
quantitative analysis of the generated polymers is done via
MALDI-TOF MS proving the introduction of hydrogen-bonding
moieties into the polymer chain and revealing the strong de-
pendence of the desorption on the chemical structure of the
Part A: Polym Chem 48: 5522–5532, 2010
KEYWORDS: cross metathesis; direct capping; functionaliza-
tional polymers; hydrogen bonding moieties; living polymer-
ization; MALDI; ROMP; symmetric olefins
INTRODUCTION Living ring opening metathesis polymeriza-
tion (ROMP) has become a valuable tool for the synthesis of
homo and block copolymers, as a large number of functional
groups can be introduced easily and with high precision into
chain, which can be achieved with different methods often
including the reaction of the respective living chain end
5
,11–18
19
with functionalized enolethers
or oxygen.
Other
approaches to such telechelic polymers rely on the use of
1
,2
17
20,21
the main-chain of the resulting polymers. With the advent
of well-defined catalysts based on molybdenum and ruthe-
nium a large plethora of different polymeric architectures
functionalized catalysts, chain transfer agents,
cial synthesis
sacrifi-
2
2,23
24
or the quench with vinyllactones. How-
ever, most of the introduced functional groups are simple in
their chemical structures, containing only alkyl- or carbonyl-
type moieties. A significant progress in this respect has been
3
could be prepared, with the Grubbs-catalysts based on
ruthenium being often better suited due to their broader
tolerance of functional groups. Especially within the field of
supramolecular chemistry, the introduction of complex func-
tional groups at the specific positions of a polymer chain is
1
6,17
accomplished by Weck and coworkers,
who has used
functionalized enolethers to introduce pyridine and cyanu-
rate-end groups into polynorbornenes. In a similar manner
telechelic polymers from cycloctene with a chain transfer
4
an important task to be fulfilled precisely. Among the many
2
5
agent bearing thymine and palladated sulfur-moieties were
prepared. However, the synthesis of the respective function-
alized enolethers requires multistep-procedures, which
therefore preclude a general application of this methodology.
supramolecular moieties known, hydrogen bonding moieties
have gained special interest since they can be used to trans-
form a random chain assembly into an ordered supramolecu-
5
lar structure. Thus, we have accomplished the introduction
of complex hydrogen-bonding moieties via a combination of
Recently, Grubbs and Matson published the direct capping of
6
–8
26,27
ROMP with ‘‘click’’-chemistry methods,
as the direct
living chains with internal olefins
using ꢀ5 equivalents
copolymerization of many monomers with complex func-
tional groups, such as hydrogen bonds or nitroxide-moieties
often leads to uncontrolled polymerization reactions with
of a symmetric olefin and moderate reaction times of ꢀ6 h.
Efficiencies for the end group introduction in most cases
reached ~9 0% and more, depending on the moieties pendant
to the respective cis-olefin. As catalysts, Grubbs catalyst 3rd-
generation and Grubbs-Hoveyda 2nd-generation were
9
,10
sometimes broad molecular weight distributions.
A still
challenging task however, is the introduction of a functional-
ized end group via ROMP to one or both sides of a polymer
2
8
applied. Using this methodology, Madkour et al. attached
Additional Supporting Information may be found in the online version of this article. Correspondence to: W. H. Binder (E-mail: wolfgang.binder@
chemie.uni-halle.de)
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 5522–5532 (2010) V
2010 Wiley Periodicals, Inc.
C
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ARTICLE
SCHEME 1 General reaction scheme for the end functionalization of ROM-polymers.
fluorescent dyes on polyoxonorbornenes with terminating
agents based on cis-1,4-dihydroxy-2-butene. Of course, the
advantage of the direct capping of living chains lies in the
simple one step reaction and the avoidance for subsequent
post functionalization processes.
– ‘‘blue stain’’ – [1 g Ce(SO ) ꢁ 4H O, 2.5 g (NH ) Mo O
ꢁ
4
2
2
4 6
7 24
4H O, 6 mL conc. H SO and 90 mL H O] and a solution of
2
2
4
2
[1 g Ce(SO ) ꢁ 4H O, 2.75 mL conc. H SO and 47 mL H O]
4
2
2
2
4
2
were used.
Microwave Reactions
In the present publication we report on the introduction of
hydrogen bonding moieties via a direct quench of living
ROMP-polymers using symmetric olefins with hydrogen
bonding moieties as shown in Scheme 1.
Microwave reactions were performed with a CEM Discover
908010 in sealed tubes equipped with a Teflon-coated stir-
ring bar.
GPC Measurements
Conceptually, we needed an attachment of the hydrogen
bonding moieties to the polymer via CAC-bonds, which pro-
vides a higher thermal stability when compared to the often
GPC measurements were done at Viscotek GPCmax VE 2001
with a Styragel linear column GMHHR; THF was used as car-
rier-solvent at 1 mL/min at RT. The sample concentration
26–28
used ether- and ester-bonds in other synthetic strategies.
was ꢀ3 mg/mL. Polystyrene standards (Mp
¼
1050–
Besides the purely synthetic approach, the analysis of the
quenching reaction and the evaluation of the quenching effi-
ciency is reported, relying on a previously developed MALDI-
1
,870,000 g/mol) were used for conventional external cali-
bration standards, using a Waters RI 3580 refractive index
detector.
9
method, which enables a relatively precise evaluation of the
MALDI-TOF MS Measurements
individual species during and after the quenching reaction.
MALDI-TOF MS measurements were done at Bruker Autoflex
III Smartbeam, equipped with a nitrogen laser (337 nm), in
the linear positive mode. As matrix dithranol was used as so-
lution of 20 mg/mL in THF. Polymer samples were dissolved
in THF at a concentration of 10 mg/mL. As salts sodium tri-
fluoroacetate was used as solution of 20 mg/mL in THF. In a
typical sample preparation a solution was mixed with a ratio
of 100:40:10 with regard to matrix:polymer:salt and spotted
on the MALDI-target.
EXPERIMENTAL
All chemicals were purchased from Sigma Aldrich and were
used without further purification. Dichloromethane and
dimethylsulfoxide were predried over calcium chloride. Tet-
rahydrofuran was predried over KOH. Dichloromethane and
dimethylsulfoxide were distilled over calcium hydride and
degassed with argon prior to use. Tetrahydrofuran was dis-
tilled over sodium, benzophenone, and degassed with argon
prior to use. Grubbs catalysts 1st-, 2nd- and 3rd-generation
were purchased from Sigma Aldrich. Catalyst 4 was prepared
3
1
Diethyl-2-ethyl-2-(undec-10-enyl)malonate (9)
All reaction steps were performed under an atmosphere of
argon. Sodium hydride (60% mineral oil dispersion, 650 mg,
2
9
analogously to the literature. Monomer 5 was prepared
3
0
16.32 mmol) was dissolved in 17 mL of anhydrous tetrahy-
analogously to the literature. NMR-spectra were measured
on Varian Gemini 2000 FT NMR spectrometer (200 and 400
MHz, 500 MHz) using chloroform (Isotec 99.8 atom% D) as
solvent. For analysis of the FIDs Mestrec-software 4.7.0.0
was used. Chemical shifts were recorded in parts per million
drofuran. To this mixture a solution of 2-ethyl-malonic acid
diethyl ester (3.23 g, 17.18 mmol) in 3 mL anhydrous THF
was added dropwise at room temperature. After the evolu-
tion of hydrogen gas ceased, 11-bromoundecene (2.67 g,
11.45 mmol) were added in one shot to the reaction mixture.
(
7
3
d) and referenced to residual protonated solvent [CDCl :
.26 ppm ( H), 77.0 ppm ( C)].
1
13
The later was refluxed and the conversion was monitored
via TLC. After complete conversion, the solvent was removed.
Thin Layer Chromatography
3
The crude product was dissolved in CHCl (100 mL). After
Thin layer chromatography (TLC) was performed with TLC
aluminium sheets silica gel 60 F254 being purchased from
addition of a small amount of water the phases were allowed
to separate in a separation funnel. The organic layer was
‘‘Merck.’’ As oxidation reagents a cerium molybdate solution
dried with brine and Na SO4 and concentrated under
2
TELECHELIC POLYNORBORNENES WITH HYDROGEN BONDING MOIETIES, KURZHALS AND BINDER
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
reduced pressure. Final purification was performed via silica
gel chromatography (hexane/ethylacetate ¼ 10/1) giving the
product (9) as colorless oil (3.7 g, 63%).
5-Methyl-1-undec-10-enyl-1H-pyrimidine-2,4-dione (11)
A mixture of thymine (1.12 g, 8.9 mmol), 1,1,1,3,3,3-hexame-
thyldisilazane (HMDS, 5.7 mL, 27 mmol), and trimethylchlor-
osilane (TMSCl) (1.1 mL, 8.9 mmol) was refluxed under
nitrogen atmosphere until a clear solution was obtained. The
excess of HMDS was then evaporated with a rotary evapora-
1
ꢂ
H NMR (400 MHz. CDCl
3
, 27 C, ppm) 5.80 (tdd, J
1
¼ 6.7
Hz, J2 ¼ 10.2 Hz, J ¼ 16.9 Hz, 1H), 4.98 (d, J ¼ 17.1 Hz,
3
1
H), 4.92 (d, J ¼ 10.2 Hz, 1H), 4.17 (q, J ¼ 7.1 Hz, 4H), 2.03
ꢂ
tor (10 mbar, 40 C). To the resulting crude 2,4-bis(trime-
(
1
q, J¼ 6.9 Hz, 2H), 1.92 (q, J ¼ 7.5 Hz, 2H), 1.85 (m, 2H),
1
3
thylsilyl)thymine were added dry DMF (7.5 mL) and 11-
bromo-1-undecene (2.5 g, 10.7 mmol). The mixture was
.24 (m, 20H), 0.81 (t, J ¼ 7.5 Hz, 3H), C NMR (100 MHz,
ꢂ
CDCl , 27 C, ppm) 171.8, 139.1, 114.0, 60.8, 58.0, 33.8, 31.6,
3
ꢂ
stirred for 11 days at 80 C under an inert atmosphere. After
29.9, 29.5, 29.4, 29.3, 29.1, 28.9, 25.2, 23.9, 14.1, 8.4.
removal of the solvent, the remaining solid was chromato-
graphed (hexane/ethylacetate ¼ 20/1) to yield 2.1 g (61%)
of compound 11.
3
1
5-Ethyl-5-(undec-10-enyl)pyrimidine-2,4,6-trione (10)
1
ꢂ
Sodium hydride (60% mineral oil dispersion, 0.94 g, 23.50
mmol) was added to a solution of urea (7.2 g, 117.4 mmol)
in 25 mL anhydrous DMSO. After the evolution of hydrogen
gas ceased, compound 9 (2.0 g, 5.88 mmol) was added drop
wise via a dropping funnel. The reaction mixture was stirred
at room temperature for 6 days during which the conversion
was monitored via TLC. After showing complete conversion
the reaction mixture was poured onto 200 mL ice water and
H NMR (400 MHz, CDCl , 27 C, ppm) 8.39 (s, 1H), 6.96 (s,
3
1
3
2
H), 5.81 (m, 1H), 4.96 (dd, J ¼ 13.6 Hz, J ¼ 23.0 Hz, 2H),
1
2
.68 (t, 2H, J ¼ 4.5 Hz), 2.04 (dd, J
1
¼ 6.9 Hz, J ¼ 14.0 Hz,
2
13
H), 1.92 (s, 3H), 1.67 (m, 2H), 1.28 (m, 12H), C NMR
ꢂ
(100 MHz, CDCl , 27 C, ppm) 164.0, 150.7, 140.4, 139.1,
3
1
2
14.1, 110.5, 48.6, 33.8, 29.4, 29.3, 29.3, 29.1, 29.1, 29.0,
8.9, 26.4, 12.3.
0
1
,1 -(Eicos-10-ene-1,20-diyl)bis(5-methyl-1H-pyrimidine-
,4-dione) (7)
the resulting solution was neutralized with KHSO . After
4
2
extracting the solution with chloroform (overall 1L) the com-
bined organic layers were concentrated under reduced pres-
sure. The crude product was dissolved in ethyl acetate. To
Compound 11 (200 mg, 0.72 mmol) and Grubbs catalyst
nd-generation (30 mg, 0.036 mmol) were weighed into a
2
vial equipped with a magnetic stir bar. After flushing with
argon the vial was sealed with a rubber septum. The mixture
was dissolved with dry dichloromethane (5 mL) and was
then placed in a microwave oven (heating up with 100 W to
this solution was added 100 mL, 10% aqueous NH Cl solu-
4
tion. After drying with brine and Na SO the solvent was
2
4
removed under reduced pressure. Pure compound 10 was
obtained after silica gel chromatography (hexane/ethylace-
tate ¼ 3/1) as white solid (1.3 g, 63%).
ꢂ ꢂ
00 C, 30 W, 100 C for 15 h). Gaseous ethylene was
1
removed by purging the solution every 2 h with argon. The
mixture was quenched with ethylvinylether and after solvent
evaporation the crude mixture was purified via silica gel
chromatography (ethyl acetate/hexane, 1/1). (114 mg, Yield
1
ꢂ
H NMR (400 MHz. CDCl , 27 C, ppm) ppm 8.89 (s, 2H),
3
5
.80 (tdd, J
1
¼ 6.7 Hz, J
2
¼ 10.1 Hz, J ¼ 16.9 Hz, 1H), 4.98
3
(
1
d, J ¼ 17.1 Hz, 1H), 4.92 (d, J ¼10.2 Hz, 1H), 2.03 (m, 6H),
1
3
.23 (m, 14H), 0.89 (t, J ¼ 7.4 Hz, 3H), C NMR (100 MHz,
60%).
ꢂ
CDCl , 27 C, ppm) 172.6, 148.9, 139.1, 114.1, 57.46, 38.8,
3
1
ꢂ
H NMR (400 MHz. CDCl
3
, 27 C, ppm) 8.71 (s, 2H), 6.97 (s,
33.7, 32.5, 29.5, 29.4, 29.4, 29.2, 29.1, 28.9, 25.2, 9.5.
2
1
1
2
H), 5.37 (m, 2H), 3.68 (m, 4H), 1.92 (s, 6H), 1.65 (m, 4H),
1
3
ꢂ
.31 (m, 28 H), C NMR (100 MHz, CDCl , 27 C, ppm)
3
0
63.9, 150.6, 140.2, 130.2, 110.4, 109.9, 48.6, 32.6, 29.6,
9.4, 29.3, 29.2, 29.1, 26.5, 12.4.
5
,5 -(Icos-10-ene-1,20-diyl)bis(5-ethylpyrimidine)-2,4,6-
trione (6)
Compound 10 (200 mg, 0.65 mmol) and Grubbs catalyst
ROMP Polymerization
2nd-generation (27 mg, 0.032 mmol) were weighed into a
The polymerization of monomer 5 with Grubbs-1st-genera-
tion catalyst is provided as an example with quencher 6.
Thus, a heated out vial equipped with a magnetic stir bar
was charged with monomer 5 (50 mg, 0.24 mmol), flushed
with argon and sealed with a rubber septum. 1st-generation
Grubbs catalyst (7.8 mg, 0.0095 mmol) was dissolved in an-
hydrous dichloromethane (1.5 mL) and was injected into the
vial. The resulting solution was stirred for 1 h to complete
the polymerization. Compound 6 (26.8 mg, 0.047 mmol) was
dissolved in anhydrous dichloromethane and injected into
the polymerization solution. The resulting solution was
stirred for 100 h, after which all of the monomer had been
consumed. Final quenching was done by adding cold ethylvi-
nylether (3 drops) and stirring for another hour. After sol-
vent evaporation the crude mixture was purified by column
chromatography with hexane/ethylacetate (3:1) to remove
vial equipped with a magnetic stir bar. The vial was flushed
with argon and sealed with a rubber septum. After dissolv-
ing the mixture with dry dichloromethane (5 mL) the vial
was placed in a microwave oven (heating up with 100 W to
ꢂ ꢂ
00 C, 30 W, 100 C for 15 h). Formed ethylene was
1
removed by purging the solution every 2 h with argon. Final
quenching was done with ethylvinylether. The solvent was
evaporated and the crude mixture was purified via silica gel
chromatography (ethyl acetate/hexane ¼ 1/1). (140 mg,
Yield 74%).
1
ꢂ
H NMR (400 MHz. CDCl , 27 C, ppm) ppm 8.81 (s, 4H),
3
5
.36 (m, 2H), 2.05 (m, 12H), 1.23 (m, 28H), 0.89 (t, J ¼ 7.4
13
Hz, 6H), C NMR (100 MHz, CDCl , ppm) 172.8, 149.1,
3
1
2
30.3, 129.8, 57.5, 38.9, 32.5, 29.6, 29.5, 29.4, 29.3, 29.2,
9.1, 28.9, 28.8, 27.1, 25.3, 9.6.
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ARTICLE
SCHEME 2 End functionalization of polynorbornenes via symmetric terminating agents.
4
,6–8,32–36
25,37–42
the excess of compound 6. The polymer was obtained by
us
and others.
Terminating agent (8) was
flushing the column with ethylacetate.
used as a model system for the introduction of end
groups via direct end capping since it is commercial avail-
Alternatively, the polymer was separated by removing the
solvent, dissolving in a minimum amount of dichloromethane
and precipitation in methanol. The fine precipitate was sepa-
2
7
able. Recent works by Matson and Grubbs showed that
compound 8 and its derivatives can be successfully applied
for the direct end capping of living chains. The bivalent,
internal olefins 6 and 7 were used as terminating agents
since the respective a-olefins tend to generate exclusively
vinyl capped polymer (vide infra), which can be explained
by complexation of the polar groups to the ruthenium
core or steric hindrance. Therefore, a simple approach to-
ward symmetric olefins bearing the respective hydrogen-
bonding moieties was investigated before conducting the
quenching reactions on the polymer (Scheme 3).
rated by ultracentrifugation. Yield: 34 mg (62%) (M
g/mol, M /M
¼ 1.3).
n
¼ 4400
w
n
RESULTS AND DISCUSSION
The concept of the presented synthetic approach relies on
the use of the bivalent quenching agents 6, 7 which are pre-
pared by a crossmetathesis reaction of the respective mono-
valent olefins bearing the respective hydrogen bonding moi-
eties using Grubbs catalyst 2nd-generation (2) as catalyst
Synthesis of the Terminating Agents
(
Scheme 2). Monomer 5 was chosen, as it can be polymer-
Quencher 6 was synthesized in a three step process starting
from commercial available diethyl-2-ethylmalonate which
was converted to compound 9 by nucleophilic substitution
with 11-bromoundecene, followed by ring closing with urea
to give compound 10. Compound 11 was prepared by pro-
tection of thymine with HMDS and TMSCl and subsequent
nucleophilic substitution with 11-bromoundecene. The
9
ized well with the catalysts 1, 3 and 4 and the resulting
polymers can be easily analyzed via MALDI-TOF-MS methods,
9
,10
as demonstrated by us recently.
Thymine and barbituric acid moieties 6, 7 were selected
as end groups, as they represent often used hydrogen
bonding motives in supramolecular polymer chemistry by
SCHEME 3 Synthesis of the ter-
minating agents 6 and 7; (a) 11-
bromoundecene, sodium hydride
(
(
63%), (b) urea, sodium hydride
63%), (c) Grubbs catalyst 2nd-
generation (74%), (d) HDMS,
TMSCl, 11-bromoundecene
61%), (e) Grubbs catalyst 2nd-
generation (60%).
(
TELECHELIC POLYNORBORNENES WITH HYDROGEN BONDING MOIETIES, KURZHALS AND BINDER
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
1
FIGURE 1 H NMR spectra of symmetric terminating agents 6 and 7, (a) compound 6, (b) compound 7.
respective mono-olefinic compounds 10 and 11 were then
converted to the symmetric bivalent olefins 6 and 7 in a
homometathesis step probing several Grubbs-catalysts. The
best results in this metathesis step were achieved with
Grubbs 2nd-generation catalyst in dichloromethane at 100
polymer can be desorbed well using MALDI-methods, thus
representing an ideal model system for proving the final end
9
,10
group-functionalization.
Grubbs catalyst 2nd-generation
could not be applied since it is generating high molecular
4
4
weight poly-5 due to the known small k /kp ratio. The
i
ꢂ
C with a microwave-irradiation power of 30 W. The forma-
generated polymers have molecular weights of 4000 to
tion of the internal olefins 6 and 7 can be observed by the
formation of the resonance at 5.36 and 5.37 ppm, respec-
tively (Fig. 1), together with a disappearance of the resonan-
ces of the vinyl-group from the a-olefins 10 and 11. The gen-
erated products are a mixture of cis- and trans-olefins, e.g.,
compound 6 displays two resonances in the carbon-NMR at
10,000 g/mol with polydispersities M /Mn ¼ 1.1 to 1.4
w
(Tables 1–3).
First, we reacted poly-5 with the a-olefin 10 as a model-sys-
tem. The formation of vinyl-terminated polymer is preferred
but in a subsequent step the polymer acts itself as a-olefin
and reacts in a cross metathesis step with the functionalized
catalyst. The quenching efficiency was calculated to be 38%
(Table 1, entry 1), (Supporting Information Fig. S9). The
MALDI-TOF spectrum (Supporting Information Fig. S9) dis-
plays two series which could be assigned to vinyl capped
poly-5 ionized with sodium (main series) and barbiturate
capped poly-5 ionized with sodium (side series). Since this
reaction did not lead to satisfying results, we concluded that
internal olefins are better suitable to generate end capped
polymers. This can be easily explained due to the symmetric
structure of these olefins which generate just one set of
products.
130.35 and 129.86 ppm which could be assigned to carbons
of a trans- and cis-double bond, respectively (see Supporting
4
3
Information Fig. S5). The ratio of trans- to cis-double bonds
can be estimated to be 3.3 to 1 for compound 6 and 2.1 to 1
for compound 7.
Quenching Reactions
As a test system of the end groups introduction we have
chosen poly-5 initiated with Grubbs catalyst 1st-generation
(1) and Grubbs catalyst 3rd-generation (3). The polymeriza-
tion yielded living polymers with narrow PDI’s and controlla-
9
ble molecular weight as described earlier. Moreover this
TABLE 1 GPC and MALDI-TOF MS Results for Polymers Quenched with Compounds 8 and 10
a
a
b
Equiv
TA
Time
(h)
M
n
(GPC)
PDI
M
n
MALDI
PDI
M
P
MALDI
I(vin)/
c
Entry
Cat.
TA
(g/mol)
(GPC)
m/z
MALDI
m/z
I(eg)
1
2
3
4
a
1
1
3
4
10
8
10
10
10
10
24
24
24
24
4200
5000
9700
6400
1.18
1.21
1.19
1.39
e
3,993
1.11
1.13
1.05
1.24
3,911.1
49
4,614
13,317
8,200
5,228.4
14,917.5
8,920.6
0.21
d
8
e
8
Calculated with Polytools software.
Ratio monotelechelic to telechelic acetoxy capped polymer ¼ 0.09,
monomer to initiator ratio (calculated molecular weight): 25 (5640 g/
mol) for entry 1, 25 (5431 g/mol) for entry 2, 30 (6482) for entry 3, 25
(5530 g/mol) for entry 4.
b
c
Mass of the peak with the highest intensity.
Ratio of intensities of vinyl terminated poly-5 and poly-5 bearing func-
tionalized end group.
d
Full conversion, no vinyl-species detected.
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ARTICLE
TABLE 2 GPC and MALDI-TOF MS Results for Polymers Quenched with Compound 6
a
a
b
Equiv
TA (6)
Time
(h)
M
n
(GPC)
PDI
M
n
MALDI
PDI
M
P
MALDI
I(vin)/
Corrected
c
d
Entry
Cat.
g/mol
(GPC)
m/z
MALDI
m/z
I(barb)
Value
1
2
3
4
5
6
7
8
9
a
1
1
1
1
1
1
3
3
3
1
2
2
2
5,500
5,400
5,400
5,200
6,500
4,400
8,000
7,600
6,400
1.15
1.31
1.23
1.22
1.24
1.32
1.18
1.19
1.15
5,969
1.05
1.05
1.05
1.03
1.06
1.03
1.05
1.07
1.03
4,750.6
50
1.61 (38.5%)
0.47 (68.0%)
0.11 (90.0%)
0.077 (93.0%)
0.050 (95.2%)
0.046 (95.6%)
0.064 (93.8%)
0.015 (98.5%)
0.005 (99.5%)
5,861
5,724
5,907
6,172
4,661
10,583
9,867
7,429
d
4,960.8
5,380.9
5,590.4
4,751.3
4,332.8
11,547.0
11,267.1
7,346.2
14.3
3.2
5
2
10
5
2
2.4
20
100
50
50
100
1.6
5
1.4
5
2.0
20
20
0.47
0.17
Calculated with Polytools software.
Corrected intensity ratio by applying the desorption ratio from the
b
c
Mass of the peak with the highest intensity.
Ratio of intensities of vinyl terminated poly-5 and poly-5 bearing bar-
quantification, monomer to initiator ratio (calculated molecular weight):
25 (5640 g/mol) for entries 1–6, 30 (6691 g/mol) for entries 7–9.
biturate end group.
The first reactions with internal olefins were conducted
The system was then expanded to the terminating agents
(TA) 6 and 7 which were reacted in a cross metathesis
step with living poly-5-chains initiated with catalysts 1 and
3. After addition of the terminating agents 6 or 7, ethylvi-
nylether was added as a final quencher to terminate the
remaining chains. The excess of the terminating agent was
subsequently removed by column chromatography or pre-
cipitation. Reaction conditions were varied in time and
amount of compounds 6 and 7, probing ratios of the
quenching agents with respect to the living end group of
1/1 up to 20/1 (see Table 2, entries 1, 4, 8) and (Table 3,
entries 1, 3). The incorporation of the end group could be
proven by NMR-spectroscopy as shown in Figure 3 for
poly-5 reacted with 2 equiv of compound 6 for a reaction
time of 2 h. Thus, at 6.40 ppm the protons (b) in a-position
to the phenyl group can be seen. The resonances d and i at
4.99 and 0.87 ppm can be assigned to the methylidene pro-
tons and the methyl group of the barbiturate end group,
respectively. The integration of these resonances gives a ra-
tio of 1.33/1 of the barbiturate-end groups vs. the vinyl-
end groups thus indicating an efficiency of the quenching
reaction of 57%.
with cis-1,4-bisacetoxy-2-butene (8) (Table 1, entry 2–4),
27
similar to the work of Matson and Grubbs. This compound
showed high reactivity toward the living chains generating
monotelechelic acetoxy capped poly-5. In the case of
Grubbs catalyst 1st-generation (1) the MALDI-TOF spectrum
[
Fig. 2(a)] shows acetoxy capped poly-5 ionized with sodium
þ
[(C H O ) C H O Na] as main series, a side series can be
11 14 4 19 11 12 2
assigned to vinyl terminated poly-5 ionized with sodium
þ
[
(C H O ) C H Na] . Complete conversion was achieved
1
1 14 4 20 8 8
with Grubbs catalyst 3rd-generation (3) where the MALDI-TOF
spectrum [Fig. 2(b)] displays just one series which could be
assigned to acetoxy capped poly-5 ionized with sodium
þ
[
(C H O ) C H O Na] . Telechelic acetoxy capped polymer
1
1 14 4 62 11 12 2
could be prepared with the bivalent catalyst 4. Besides the
main series showing telechelic acetoxy capped poly-5 ionized
þ
with sodium [(C H O ) C H O Na] a side-series could be
1
1 14 4 28 16 18 4
assigned to monotelechelic acetoxy capped poly-5 ionized with
þ
sodium [(C H O ) C H O Na] [Fig. 2(c,d)]. These results
1
1 14 4 29 13 14 2
27
are in good agreement with the work of Matson and Grubbs,
showing efficiencies for the end group introduction for com-
pound 8 of upto 97% as proven by NMR-spectroscopy.
TABLE 3 GPC and MALDI-TOF MS Results for Polymers Quenched with Compound 7
a
a
b
Equiv
TA (7)
Time
(h)
M
n
(GPC)
PDI
M
n
MALDI
PDI
M
P
MALDI
I(vin)/
Corrected
c
d
Entry
Cat.
(g/mol)
(GPC)
m/z
MALDI
m/z
I(thym)
Value
1
2
3
4
a
1
1
1
3
1
2
100
100
100
100
5,600
5,900
5,800
8,700
1.22
1.19
1.22
1.15
4,929
5,106
5,695
8,682
e
1.12
1.12
1.12
1.03
4,961.7
4,962.1
4,961.7
9,166.4
2.03
2.00
1.49
0.113 (89.9%)
0.111 (90.0%)
0.083 (92.3%)
0.134 (88.2%)
ꢂ
5 (35 C)
e
5
2.42
Calculated with Polytools software.
Only the sodium series were considered for the quantification, mono-
b
c
Mass of the peak with the highest intensity.
Ratio of intensities of vinyl terminated poly-5 and poly-5 bearing thy-
mer to initiator ratio (calculated molecular weight): 25 (5610 g/mol) for
entries 1–3, 30 (6661 g/mol) for entry 4.
mine end group.
d
Corrected intensity ratio by applying the desorption ratio from the
quantification.
TELECHELIC POLYNORBORNENES WITH HYDROGEN BONDING MOIETIES, KURZHALS AND BINDER
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 2 MALDI-TOF MS spectra of poly-5 quenched with cis-1,4-bisacetoxy-2-butene (8), (a) with Grubbs catalyst 1st-generation,
1
0 equiv of 8, 24 h, enlargement from 4175 to 4425 m/z, (b) initiated with Grubbs catalyst 3rd-generation, 10 equiv of 8, 24 h,
enlargement from 13150 to 13500 m/z, (c) with bivalent catalyst 4, 10 equiv of 8, 24 h, full spectrum, (d) enlargement from 6100 to
500 m/z.
6
The resulting polymers were intensively investigated via
MALDI-TOF MS as mass spectrometric methods have become
important tools for the characterization of synthetic poly-
inverse picture compared to poly-5 initiated with Grubbs
catalyst 1st-generation. The best results for the terminating
agent 6 were achieved with catalyst 3 and reaction with an
excess of terminating agent (20 equiv) for 100 h (Table 2,
entries 8 and 9). These results can be explained due to the
higher reactivity of catalyst 3 toward internal olefins.
9
,45
mers.
The mass-spectra (Figures 4–6) of the end func-
tionalized polymers showed in the most cases two series,
which could be assigned to the functionalized polymer and
vinyl capped polymer. The peaks of each series are separated
by m/z ¼ 210 Da which corresponds to the mass of mono-
mer 5. The MALDI-TOF spectrum of poly-5 initiated with cat-
alyst 1 and quenching with terminating agent 6 (5 equiv,
1
4
00 h) is shown in Figure 4. The enlarged spectrum [Fig.
(b)] displays two series, which could be assigned to vinyl-
þ
capped poly-5 ionized with sodium [(C H O ) C H Na]
1
1 14 4 20 8 8
as main series and barbiturate capped poly-5 ionized with
þ
sodium [(C H O ) C H N O Na] as side series. Figure
1
1 14 4 19 23 32 2 3
5
displays the MALDI-TOF spectrum of poly-5 initiated with
catalyst 3 and quenching with terminating agent 6 (20 equiv,
00 h). The enlarged spectrum [Fig. 5(b)] displays three se-
1
ries with the barbiturate capped poly-5 ionized with sodium
þ
[
(C H O ) C H N O Na] as main series. Barbiturate
1
1 14 4 32 23 32 2 3
capped poly-5 ionized with lithium [(C H O ) -
1
1 14 4 32
þ
C H N O Li]
and vinyl-capped poly-5 ionized with
sodium [(C H O ) C H Na] could be assigned as side se-
2
3 32 2 3
þ
1
1 14 4 33 8 8
ries. In the case of terminating agent 6 the change from
Grubbs catalyst 1st (1) to Grubbs catalyst 3rd-generation (3)
leads to a significant decrease of the vinyl capped species in
the MALDI-TOF spectra [Figs. 4(b), 5(b)], showing nearly an
1
FIGURE 3 H NMR-spectrum for poly-5 initiated with Grubbs
catalyst 1st-generation, quenched with 2 equiv of compound 6
for 2 h.
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WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

ARTICLE
FIGURE 4 MALDI-TOF MS spectrum of poly-5 initiated with Grubbs catalyst 1st-generation and quenched with TA 6, 5 equiv, 100
h, (a) full spectrum (b) enlargement from 4310 to 4430 m/z. [Color figure can be viewed in the online issue, which is available at
www.wileyonlinelibrary.com.]
Terminating agent 7 was reacted analogously with poly-5
initiated with catalyst 1 and 3 with a reaction time of 100 h.
In Figure 6(a) the enlarged MALDI-TOF spectrum of poly-5
initiated with catalyst 1 and quenched with compound 7 (5
a significant change in the intensity ratio of vinyl capped to
thymine capped poly-5-species (Table 3, entries 3, 4), [Fig.
6(a,b)]. In the case of catalyst 3 additional polymer-species
ionized with lithium appear in the mass spectrum.
equiv, 100 h) is shown. The main series is vinyl capped poly-
þ
5
ionized with sodium [(C H O ) C H Na] , the side se-
MALDI-TOF Analysis
1
1 14 4 23 8 8
ries could be assigned to thymine capped poly-5 ionized
The fraction of functionalized polymer increases with
increasing reaction-time and amount of added terminating
agent 6 (Table 2, entries 1, 3, 4, 6). A further increase by
prolonging the reaction time after 100 h was not observed.
By changing from catalyst 1 to 3 and by using higher excess
of the terminating agent the fraction of barbiturate capped
polymer could be further increased (Table 2, entries 8, 9).
Similar observations were made for the reaction of living
poly-5 with terminating agent 7. The fraction of thymine-
capped poly-5 could be increased by using higher amounts
of the terminating agent (Table 3, entries 1 and 3). No fur-
ther increase in the fraction of thymine-capped poly-5 was
observed by changing from catalyst 1 to catalyst 3 (Table 3,
þ
with sodium [(C H O ) C H N O Na] . Figure 6(b)
1
1 14 4 22 22 30 2 2
shows the enlarged MALDI-TOF spectrum of poly-5 initiated
with catalyst 3 and quenched with compound 7 (5 equiv,
1
00 h). The main series is vinyl capped poly-5 ionized
þ
with sodium [(C H O ) C H Na] , two other series could
1
1 14 4 42 8 8
be assigned to thymine capped poly-5 ionized either
þ
with lithium [(C H O ) C H N O Li] or with sodium
1
1
14 4 41 22 30
þ
2
2
[
(C H O ) C H N O Na] . The fourth series could not
1
1 14 4 41 22 30 2 2
be assigned but it might overlap with vinyl capped poly-5
þ
ionized with potassium [(C11
H
14
O
4
)
42
C
8
H
8
K] . In contrast to
terminating agent 6 the change from Grubbs catalyst 1st-
generation to Grubbs catalyst 3rd-generation did not lead to
FIGURE 5 MALDI-TOF MS spectrum of poly-5 initiated with Grubbs catalyst 3rd-generation and quenched with TA 6, 20 equiv, 100
h (a) full spectra (b) enlargement from 7000 to 7200 m/z. [Color figure can be viewed in the online issue, which is available at
www.wileyonlinelibrary.com.]
TELECHELIC POLYNORBORNENES WITH HYDROGEN BONDING MOIETIES, KURZHALS AND BINDER
5529

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 6 MALDI-TOF MS spectra of poly-5 quenched with terminating agent (7), (a) initiated with catalyst (1), 5 equiv (7), 100 h,
enlargement from 4950 to 5200 m/z, (b) initiated with catalyst (3), 5 equiv (7), 100 h, enlargement from 8950 to 9170 m/z.
entries 3 and 4). Since desorption of the specific polymer-
species depends strongly on the chemical structure, a quanti-
fication of the different polymer species was done via
MALDI-TOF MS. This method was already applied for the
quantification of block copolymers in one of our previous
tion ratio to give an estimation of the content of function-
alized polymer. For the quantification just the species ion-
ized with sodium were taken into consideration. By
applying this correction we could determine that the frac-
tion of barbiturate capped polymer in the mixture is
between 38 and 99%. The best result with quencher 6
could be achieved by using the more reactive catalyst 3
with an excess of 20 equivalents of terminating agent and
a reaction time of 100 h to get a fraction of functionalized
polymer of 99% (Table 2, entry 9). For the polymers
quenched with terminating agent 7 the fraction of thy-
mine-capped poly-5 is between 88 and 92%. No significant
difference between the terminating agents 6 and 7 could
be noticed comparing the conversion with 5 equivalents of
terminating agent and a reaction time of 100 h for poly-5
initiated with catalyst 1 (Table 2, entry 6), (Table 3, entry
3) showing a fraction of functionalized polymer of 96 and
92%, respectively.
9
46,47
papers based on the works of Chen et al.
For the quan-
tification a sample of the end functionalized polymer was
measured in different mixtures with vinyl capped poly-5.
The slope of the curve (Fig. 7) gives the desorption ratio
between vinyl capped poly-5 and poly-5 with the functional
end group. As the curves have a linear slope showing values
of 18 for thymine and 30 for barbiturate the capped poly-
mer, respectively, these values indicate that the vinyl capped
polymer is preferentially desorbed. Therefore, the fraction of
the end functionalized polymer is strongly underestimated
by the determined factor. The values for the intensity ratio
of vinyl capped poly-5 against end group functionalized
poly-5 in Tables 2 and 3 were then corrected by the desorp-
FIGURE 7 Quantification curves for poly-5 (a) capped with barbiturate end group (6), (b) capped with thymine-end group (7),
I(vinyl)/I(barb): intensity ratio of poly-5 capped with vinyl-group against poly-5 capped with barbiturate end group, w(vinyl)/
w(barb): mixing ratio of poly-5 capped with vinyl-group against poly-5 capped with barbiturate end group, I(vin)/I(thym): intensity
ratio of poly-5 capped with vinyl-group against poly-5 capped with thymine end group, w(vin)/w(thym): mixing ratio of poly-5
capped with vinyl-group against poly-5 capped with thymine end group.
5530
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ARTICLE
CONCLUSIONS
11 Chen, B.; Metera, K.; Sleiman, H. F. Macromolecules 2005,
3
8, 1084–1090.
In this article, we presented the successful synthesis of two
new terminating agents 6 and 7 bearing hydrogen bonding
moieties and their use for the end functionalization of living
ROM-polymers. The terminating agents were prepared by
the homo metathesis of the corresponding a-olefins with aid
of microwave irradiation. Incorporation of the functional
moieties onto the polymer backbone was proven by NMR-
spectroscopy and MALDI-TOF MS. The efficiency of this pro-
cess depends on the reaction time and on the amount of
added terminating agent and can be quantified via MALDI-
TOF MS. Polymers with a fraction of 99% of barbiturate-end
groups could be prepared by reacting the living chains, initi-
ated with catalyst 3, with an excess of terminating agent 6
1
2 Gestwicki, J. E.; Cairo, C. W.; Mann, D. A.; Owen, R. M.;
Kiessling, L. L. Anal Biochem 2002, 305, 149–155.
13 Gordon, E. J.; Gestwicki, J. E.; Strong, L. E.; Kiessling, L. L.
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4 Katayama, H.; Yonezawa, F.; Nagao, M.; Ozawa, F. Macro-
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5 Owen, R. M.; Gestwicki, J. E.; Young, T.; Kiessling, L. L. Org
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(
20 equiv) and a reaction time of 100 h. With terminating
agent 7, it was possible to prepare polymer with a fraction
of 92% of thymine-end groups by reacting the living chains,
initiated with catalyst 1, with an excess of terminating agent
18 Ambade, A. V.; Burd, C.; Higley, M. N.; Nair, K. P.; Weck, M.
Chem Eur J 2009, 15, 11904–11911.
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9 Biagini, S. C. G.; Gareth Davies, R.; Gibson, V. C.; Giles, M.
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catalysts can be applied on an array of functional moieties
due to the tolerance of these catalysts on functional groups.
Symmetric olefins acting as terminating agents represent a
simple approach for the end group introduction by the direct
capping of living chains, thus circumventing multistep or-
ganic syntheses of reactive olefinic moieties. We will further
investigate this method for the preparation of supramolecu-
lar polymers.
2
0 Maughon, B. R.; Morita, T.; Bielawski, C. W.; Grubbs, R. H.
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DFG INST 271/249-1; INST 271/247-1; INST 271/248-1 for
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