Catalytic Living Ring Opening Metathesis Polymerisation: The Importance of Ring Strain in Chain Transfer Agents

Article abstract of DOI:10.1002/anie.201907921

A recently developed catalytic living ring opening metathesis polymerisation (ROMP) was investigated using a series of reversible chain transfer agents (CTA) carrying either cyclopentene or cyclohexene rings, differing only in ring strain. All cyclopentene derivatives examined showed significantly faster reaction rates than the corresponding cyclohexene derivatives. This resulted in lower molecular weight dispersities and better control of the molecular weight for the cyclopentene compared to the cyclohexene CTAs. Both Grubbs’ second and third generation catalysts could be employed in catalytic living ROMP using cyclopentene CTA derivatives. The kinetics of different CTAs were studied, block copolymers were synthesised and residual ruthenium quantified by ICP-OES. All polymers were fully characterised by NMR, GPC and MALDI-ToF mass spectrometry. The new cyclopentene CTAs are readily synthesised in a few straightforward steps and provide faster reaction kinetics than all previously reported reversible CTAs.

Full text of DOI:10.1002/anie.201907921

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Catalytic Living Ring Opening Metathesis Polymerisation: The
Importance of Ring Strain in Chain Transfer Agents
Authors: Peng Liu, Mohammad Yasir, and Andreas F.M. Kilbinger
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201907921
Angew. Chem. 10.1002/ange.201907921
Link to VoR: http://dx.doi.org/10.1002/anie.201907921
http://dx.doi.org/10.1002/ange.201907921

10.1002/anie.201907921
Angewandte Chemie International Edition
COMMUNICATION
Catalytic Living Ring Opening Metathesis Polymerisation: The
Importance of Ring Strain in Chain Transfer Agents
Peng Liu‡, Mohammad Yasir‡ and Andreas F.M. Kilbinger*
Numerous methods have been developed to reduce the level
catalyst in the final metathesis
Abstract:
A recently developed catalytic living ring opening
of
metathesis polymerisation (ROMP) was investigated using a series of
reversible chain transfer agents (CTA) carrying either cyclopentene or
cyclohexene rings, differing only in ring strain. All cyclopentene
derivatives examined showed significantly faster reaction rates than
the corresponding cyclohexene derivatives. This resulted in lower
molecular weight dispersities and better control of the molecular
weight for the cyclopentene compared to the cyclohexene CTAs. Both
Grubbs’ second and third generation catalysts could be employed in
catalytic living ROMP using cyclopentene CTA derivatives. The
kinetics of different CTAs were studied, block copolymers were
synthesised and residual ruthenium quantified by ICP-OES. All
polymers were fully characterised by NMR, GPC and MALDI-ToF
mass spectrometry. The new cyclopentene CTAs are readily
synthesised in a few straightforward steps and provide faster reaction
kinetics than all previously reported reversible CTAs.
products.12 , 13 , 14 , 15 , 16, 17 , 18 , 19 , 20, 21 , 22 , 23 , 24 , 25, 26 , 27 However, these
methods mostly rely on easy removal of the transition metal
complex or improved product separation. To date, only few
reports exist on catalytic metathesis polymerisations producing
multiple polymer chains per ruthenium complex. Acyclic diene
metathesis polymerisation (ADMET), pioneered by Wagener et al.
uses catalytic amounts of metal complex28,29,30 in a step-growth
process. Homotelechelic polymers prepared by ruthenium
complexes were first described by Grubbs and co-authors using
an irreversible chain transfer agent (CTA) in the presence of sub-
stoichiometric quantities of ruthenium complex. 31 , 32 , 33 , 34 , 35 , 36
Fewer examples have been reported on the synthesis of
heterotelechelic polymers using only catalytic quantities of
transition metal complex.37,38,39,40 However, none of the examples
given above can be considered as living, as molecular weight
distributions are typically broad, and block copolymers cannot be
made.
R
R
Ring opening metathesis polymerisation (ROMP), which uses
the metathesis of cyclic olefins to synthesise linear polymers, has
become a very important method for polymer synthesis in
cis
CTA10
trans
CTA11
CTA1 R = phenyl
CTA4 R = phenyl
CTA2
CTA3
CTA9
CTA5
CTA6
CTA7
CTA8
R = cyclohexyl
R = cyclopentyl
R = cyclopropyl
R = cyclohexyl
R = cyclopentyl
R = cyclopropyl
R = isopropyl
biomedical,
material,
academic
and
industrial
applications.1,2,3,4,5,6,7,8 Living ROMP, wherein irreversible chain-
transfer events and termination reactions are absent, is an
important polymerisation technique, due to its excellent control of
molecular weight and the narrow molecular weight distribution of
the resulting polymers. 9 , 10 , 11 For polymerisations, ruthenium
carbene complexes developed by Grubbs et al. (G2: (1,3-
bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene) dichloro (phe-
O
O
O
O
R
N R
N CH3
O
OTIPS
OTIPS
O
O
nylmethylene)(tricyclohexylphosphine)ruthenium
and
G3:
MNI R = methyl
MOMNI R = methyl ENC
EOMNI
NBSM
dichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]
HNI
PNI
R = n-hexyl
R = phenyl
R = ethyl
(benzylidene)bis(3-bromopyridine)ruthenium(II)) are frequently
used mainly due to their easy handling and high functional group
tolerance. However, in a typical living ROMP polymerisation, the
ruthenium catalyst will always be covalently bound to the end of
the growing polymer chain. It is, therefore, mechanistically
determined that each catalyst can only form one polymer chain,
which means stoichiometric amounts of the transition metal
complex are required with respect to the number of polymer
chains formed in a living ROMP. This can result in high catalyst
loadings, especially during the synthesis of low molecular weight
polymers, which is expensive and leads to potentially toxic
ruthenium residues in these polymers.
Figure 1 Top: Chain transfer agents (CTA1-CTA9) and model compounds
CTA10-11. Bottom: monomers (MNI, HNI, PNI, MOMNI, EOMNI, ENC, NBSM)
investigated in this study.
We recently described a mechanism for catalytic living ROMP
that relies on
a
degenerative reversible chain-transfer
polymerisation that required only a catalytic amount of ruthenium
carbene complex.41 Here, we report new CTAs (Figure 1) based
on either cyclopentene or cyclohexene derivatives and provide a
kinetic analysis that shows the importance of ring strain in CTAs
for degenerative chain transfer metathesis polymerizations.
Catalytic living ROMP41 is based on a degenerative chain
transfer mechanism in which a sub-stoichiometric quantity of a
*
P. Liu, M. Yasir and Prof. Dr. A. F. M. Kilbinger
Department of Chemistry, University of Fribourg
Chemin du Musée 9, CH-1700 Fribourg, Switzerland
E-mail: andreas.kilbinger@unifr.ch
propagating ruthenium carbene chain end of
a polymer
exchanges rapidly with other chain ends. This results in quasi-
simultaneous growth of all polymer chains leading to narrow
molecular weight distributions and control of molecular weight
(see Figure 2 B as an example with CTA7 and MNI).
‡
These authors contributed equally.
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
http://doi.org/xxxxxxxxxxxx
1
This article is protected by copyright. All rights reserved.

10.1002/anie.201907921
Angewandte Chemie International Edition
COMMUNICATION
A
slow monomer addition
[Ru]
MNI (0.075M, 5mL/h)
[Ru]
[Ru]
+
+
Ph
O
O
O
O
N
N
n
G2/G3
CTA 7
n
catalytic amount
Macromolecular CTA
catalytic amount
[Ru]
B
[Ru]
[Ru]
kCT
kCT
n
m
n
m
n
+
+
O
O
N
O
O
O
O
O
O
m
N
N
N
O
O
N
O
N
O
O
O
N
Macromolecular CTA
Macromolecular CTA
N
O
O
kp
kp
Figure 2 A) Polymerization of MNI in the presence of CTA7 under slow monomer addition conditions yields mainly polymer chains being end-functionalized with
the cyclopentenyl unit and a small number (catalytic amount) of propagating chains. B) The degenerative chain transfer mechanism41 exploited in this investigation
shown as an example using CTA7 and MNI. The polymer end group of the macromolecular CTA (shown in blue) exchanges with the propagating carbene end
group (polymer shown in red) via an intermediate (right) in a degenerate equilibrium. kp: propagation rate constant, kCT: chain transfer rate constant. [Ru]= G2 or G3
based propagating carbene complexes.
As previously reported, CTA141 (Figure 1) reacts only very
slowly with propagating ruthenium alkylidene complexes. It is for
this reason that it cannot be employed as a chain transfer agent
in catalytic living ROMP. In order to assign the low reactivity of
CTA1 to the cyclohexenyl group, CTA2-3 were synthesized both
of which carried the same endocyclic double bond as CTA1 but
different substituents (cyclohexyl and cyclopentyl groups)
attached to the exocyclic double bond.42 However, neither CTA2
nor CTA3 show a higher reactivity than CTA1 in time-resolved 1H-
NMR spectroscopic experiments (see supporting information). As
the low reactivity of CTA1-3 is caused by the endocyclic double
bond, common to all three CTAs, we decided to synthesize a
series of new CTAs carrying endocyclic double bonds within five-
membered rings (CTA4-8) in which the ring strain was assumed
to be higher. In addition to the common cyclopentenyl group,
CTA4-8 differ in the substituent attached to the exocyclic double
bond. CTA4 carries a phenyl group attached to the exocyclic
double bond and is therefore similar in structure to CTA1,
whereas CTA5 represents the saturated version of CTA4,
carrying a cyclohexyl substituent attached to the exocyclic double
bond.
open the five-membered ring, no ruthenium-alkylidene signal
could so far be recorded that would correspond to the ring-opened
intermediate indicating that such alkylidenes represent transient
structures that immediately undergo ring closing reactions.
Next, three further CTAs (CTA6-8) were investigated, all
carrying the ring strained cyclopentenyl group but yielding
different ruthenium alkylidenes upon reaction with the
propagating G3 complex (addition of 10 equiv of either CTA6,7 or
8 to a G3 initiated MNI (34 equiv) solution). It could be shown that
CTA6-8 all gave rapid and complete conversions to the new
1
alkylidene signals when followed by H-NMR spectroscopy. The
stability of the newly formed ruthenium alkylidenes also varied
significantly and decreased in the following order: Ru-
cyclopropylmethylidene (17.20 ppm, from CTA7)
benzylidene (19.04 ppm, from CTA4)
cyclopentylmethylidene (18.58 ppm, from CTA6)
>
Ru-
Ru-
Ru-
Ru-
>
>
=
cyclohexylmethylidene (18.97 ppm, from CTA5)
isopropylidene (18.66 ppm, from CTA8). However, in any catalytic
living ROMP reaction these stability differences are not important
as these ruthenium carbene complexes only exist for a very short
time at the pre-equilibrium stage (Figure 2 A).
In our previous investigation41 we could show that our CTA
reacted exclusively via the "endocyclic double bond first"
pathway. CTA7 carries a cyclopropyl group attached to the
exocyclic double bond that is sterically less demanding than the
residues of all other CTAs investigated here or previously. To
investigate whether CTA7 reacts via the edocyclic or exocyclic
double bond first, we synthesized model compounds CTA10 (cis)
and CTA11 (trans) differing in their exocyclic double bond
configuration but lacking the endocyclic double bond altogether.
Time-resolved 1H-NMR spectroscopic experiments revealed
(supporting information), however, that when a propagating (MNI)
G3 catalyst (1equiv) was exposed to CTA9-11 (10 equiv) CTA10
formed the new cyclopropylmethylidene carbene with 90%
conversion after 24min. whereas CTA11 only formed 64% (24
min.) and CTA9 62% (24 min.) of the new carbene. The
cyclohexene carrying CTA9 therefore shows reaction rates on the
same order of magnitude as the cross metathesis with the trans
configured CTA11. CTA7, however, forms the new
cyclopropylmethylidene under identical reaction conditions with a
conversion of 100% in 8 min. As the steric demand of cyclopentyl
or cyclohexyl groups is very similar,43 we estimated that the steric
hindrance of the exocyclic double bond in CTAs7,9 and 11 was
also similar. This would suggest that a very different mechanism,
In a catalytic living ROMP a commercial ruthenium benzylidene
complex first reacts with a reversible chain transfer agent (for
example CTA4-8) yielding a new ruthenium carbene complex
(carrying the group R, Figure 1 CTA4-8). A strained cyclic
monomer is then added slowly to this mixture of CTA and newly
formed ruthenium carbene complex (Figure 2A). Due to the low
monomer concentration, the propagation reaction and reaction
with the CTA become equally likely, leading to a reversible chain
transfer equilibrium (Figure 2 B) in which the polymer end groups
of two chains exchange as described previously. 41
To investigate the reactivity of CTA4-5 we followed the reaction
of propagating MNI and CTA4-5 by 1H-NMR spectroscopy
(addition of 10 equiv of CTA4 or CTA5 to a G3 initiated MNI (34
equiv) solution). We observed a fast and complete conversion of
the signal corresponding to the propagating MNI alkylidene (18.50
ppm) to the new carbene (a benzylidene (19.06 ppm) for CTA4
and cyclohexylmethylidene (18.97 ppm) for CTA5). We
furthermore observed that over time the G3-benzylidene (from
CTA4)
decomposed
less
rapidly
than
the
G3-
cyclohexylmethylidene (from CTA5). This initial investigation
showed clearly that CTA4-5 carrying the more strained
cyclopentenyl groups were dramatically more reactive than the
cyclohexenyl carrying CTA1-3. Despite the greater tendency to
2
This article is protected by copyright. All rights reserved.

10.1002/anie.201907921
Angewandte Chemie International Edition
COMMUNICATION
most likely the ring-opening-ring closing sequence is responsible
for this massively increased reaction rate.
or CTA7. The isotopically resolved MALDI-ToF MS spectra of all
polymers matched the two expected end groups of CTA5 or CTA7
(see Supporting Information, polymer 10-13).
Encouraged by these results, we next carried out the
polymerisation of MNI under catalytic living ROMP conditions
(see supporting information). Since the rate of propagation of ring-
strained monomers, such as norbornenes, is significantly faster
than the olefin metathesis reaction with the CTA (kCT≪kp, see
Figure 2B),44 the monomer concentration was kept low at all
times, which was realised by slow addition via a syringe pump.
Reaction conditions were optimised using CTA5.
Table 1 Catalytic Living ROMP using CTA1-8 a
b
c
d
#
1
2
3
4
5
6
7
8
polymer
CTA
Mncalc.
Mncalc.
5310
5310
5310
5310
5310
5310
5310
5310
Mnobs.
Đd
yield %
99
polymer 3 CTA1 53100
polymer 4 CTA2 53100
polymer 5 CTA3 53100
polymer 6 CTA4 53100
polymer 1 CTA5 53100
polymer 7 CTA6 53100
polymer 8 CTA7 53100
polymer 9 CTA8 53100
41000
38000
34000
9900
7100
7800
8900
9000
1.29
1.35
1.25
1.18
1.18
1.16
1.17
1.17
99
99
99
98
99
99
99
a All of the reactions were carried out with 4.45 mg G3 (0.005 mmol) and 10
equiv of CTA in 1.5 mL degassed DCM, followed by 300 equiv of MNI (266 mg.
1.5 mmol), which was dissolved in 20 mL degassed DCM (0.075 mol/L) added
by a syringe pump at 5 mL/h under Ar. b Mn under non-catalytic conditions was
calculated with a degree of polymerization Xn= [monomer]:[G3] = 300:1. c Mn
under catalytic living ROMP conditions was calculated using a degree of
Figure 3 MALDI-ToF mass spectrum (DCTB, AgTFA) of polymer 1. Left:
Chemical structure of polymer 1 with calculated mono-isotopic mass. Center:
Mass distribution. Right: Most intense peak of the distribution, isotopically
resolved.
polymerization Xn= [monomer]:[CTA]
= 30:1. d determined by GPC
(chloroform). Note that entries 1-3 employing cyclohexenyl carrying CTA1-3 did
not result in any molecular weight control.
When MNI (0.075 mol/L) was added slowly (5mL/h) to the
solution of Grubbs’ third-generation catalyst (G3) and CTA5, the
It is furthermore worth noting that when we used exo-N-methyl-
7-oxabicyclo[2.2.1]hept-4-methyl-5-ene-2,3-dicarboximide
(MOMNI, Figure 1) and exo-N-methyl-7-oxabicyclo[2.2.1]hept-4-
ethyl-5-ene-2,3-dicarboximide (EOMNI, Figure 1), carrying
sterically demanding groups on the bridge head carbon that slow
down propagation, polymerisations could be run in one pot (see
Supporting Information, polymer 14-15) without the need of a
slow monomer addition via a syringe pump. This feature will be
further investigated in the near future.
desired polymer was formed (polymer 1, Mn
(CHCl3) = 7100
GPC
g mol-1, Đ = 1.18, Mpeak (MALDI-ToF) = 4001.71 g mol-1). An
isotopically resolved MALDI-ToF mass spectrum matching the
polymer structure with both CTA5 end-groups (cyclohexyl and
cyclopentenyl) is shown in Figure 3.
As expected, the molecular weight of the produced polymer
was much lower than that calculated from the monomer:G3 ratio
(Mn = 53100 g mol-1) indicating that successful reversible chain
To prove that the monomer:CTA ratio determines the polymer
molecular weight and that the polymerisation fulfils living
characteristics, different molecular weight polymers were
synthesised by changing the MNI:CTA5 ratio (Figure 4). A linear
correlation between the molecular weight (Mn, GPC) and the
transfer had taken place. In case of
a
non-catalytic
polymerisation, the molecular weight of the polymer would have
been significantly higher (see Table 1). All of the optimisation
results can be found in the Supporting Information. Similar results
were obtained when Grubbs’ second-generation catalysts (G2)
was used under the optimised reaction conditions (supporting
information).
MNI:CTA5 ratio was obtained as expected for
polymerization under reversible chain transfer conditions.
a living
In order to compare the efficiency of CTA1-8 we carried out
eight different catalytic living ROMP polymerizations using
monomer MNI (see Table 1 and supporting information). As
expected, CTA1-3 (entries 1-3, Table 1) did not yield polymers
(polymer 3-5) with controlled molecular weights (see above).
Instead, the molecular weights obtained for these CTAs
resembled those of classical living ROMP emphasizing once
more that the chain transfer to CTA1-3 is too slow to control the
molecular weight in a catalytic fashion. CTA4-8, on the other
hand, gave excellent molecular weight control of the resulting
polymers (polymer1, polymer 6-9) and narrow molecular weight
dispersities. Isotopically resolved MALDI-ToF mass spectra
matched the masses for polymers with end groups corresponding
to the CTA employed (see supporting information).
To expand the applicability of catalytic living ROMP, different
monomers such as exo-N-hexyl norbornene imide (HNI, Figure
1), exo-N-phenyl norbornene imide (PNI, Figure 1), endo-5-
norbornene-2,3-bis(triisopropyl)silylmethanol (NBSM, Figure 1)
and exo-ethyl-5-norbornene carboxylate (ENC, Figure 1) were
polymerised under catalytic living ROMP conditions using CTA5
Figure 4 Plot of the molecular weight (Mn, GPC(CHCl3), black circles) and
molecular weight dispersity (Đ, blue squares) versus the [MNI]/[CTA5] ratio.
The ratios reported in brackets denote the [G3]/[CTA5] ratio.
a
The molecular weight dispersities of the resulting polymers was
low (Đ = 1.2-1.3) and the masses of the polymers matched the
assumed structures with CTA5 end groups (see above) which
3
This article is protected by copyright. All rights reserved.

10.1002/anie.201907921
Angewandte Chemie International Edition
COMMUNICATION
provides a strong indication that the polymerisation process is
indeed living (Figure 4, see also Supporting Information polymer
16-20).
the efficiency of our method: only 33 mg of polymer (Mn
GPC
(CHCl3) = 6900 g mol-1, Đ = 1.15) could be synthesised non-
catalytically using 4.45 mg of G3, while 266 mg of polymer (Mn
(CHCl3) = 7200 g mol-1, Đ = 1.20) was synthesised via
GPC
Furthermore, the G3:CTA5 ratio was also varied during the
experiment described above (see ratios in brackets in Figure 4).
For low molecular weight polymers a ratio of CTA5:G3=100 was
used, in other words, one molecule of 3rd generation Grubbs
catalyst was responsible for the synthesis of 100 living polymer
chains. This once more emphasises the significant reduction of
the amount of transition metal possible with this catalytic method.
catalytic living ROMP using the same amount of G3. Furthermore,
inductively coupled plasma optical emission spectroscopy (ICP-
OES) showed that 1.38 ppm of ruthenium remained in 3.5 mg of
the polymer prepared non-catalytically after two precipitations in
cold methanol whereas only 0.21 ppm ruthenium was left in 3.5
mg of the catalytically prepared polymer sample (Supporting
Information). This result sums up several advantages of the
catalytic living ROMP method, as with the same amount of G3
complex, more polymer at lower cost and with lower residual
transition metal contamination can be prepared.
In conclusion, we have developed a series of new chain
transfer agents which can be prepared in good yields and few
straightforward steps for a recently developed catalytic living ring
opening metathesis polymerisation method. Kinetic investigations
of the chain transfer agents clearly showed that their efficiency
during the degenerate chain transfer process depends highly on
their ring strain. While the cyclopentenyl carrying chain transfer
agents yielded well-controlled polymers with low molecular weight
dispersities, cyclohexenyl carrying chain transfer agents exhibited
only low reactivity. Grubbs’ second and third generation catalysts
were examined in catalytic living ROMP and produce polymers
with the expected end groups which are mechanistically defined
by the chain transfer agent employed. Block copolymers could be
synthesised either via continuous slow addition of two different
monomers or via chain extension of a separately prepared
macromolecular chain transfer agent. The lowest ruthenium
catalyst-to-CTA ratio examined in this report was 1:100. This
equates to a 100-fold saving of ruthenium carbene complex
compared to a classical living ROMP. The residual ruthenium in
the final polymer was also analysed by ICP-EOS and found to be
significantly reduced compared to non-catalytically prepared
metathesis polymers. Catalytic living ROMP combined with the
simplified chain transfer agent synthesis reported here offers a
huge potential especially for the synthesis of functional polymers
for biomedical, materials, industrial and academic use where very
low ruthenium contamination is crucial.
Figure 5 GPC trace of polymer 1 (black, Mn
(CHCl3) = 7100 g mol-1, Đ =
GPC
1.18) and block copolymer polymer 22 (red, Mn GPC (CHCl3) = 22500 g mol-1, Đ
= 1.36). Catalyst G3 and CTA5 were employed for this reaction.
One important feature of a living polymerisation is the ability to
prepare block copolymers. To further prove that our newly
developed chain transfer agents produced living polymers,
monomers MNI (300 equiv, 0.075 mol/L) and HNI (300 equiv,
0.075 mol/L) were added (5 mL/h) to the G3/CTA5 (1:10) mixture
sequentially. GPC (chloroform) analysis performed after addition
of both monomers showed a monomodal molecular weight
distribution and a molecular weight of 17900 g mol-1 (polymer 21,
Supporting Information) supporting a block copolymer formation.
A more rigorous proof for the proposed degenerate chain transfer
mechanism and block copolymer formation was obtained when
the polymer taken from the catalytic living ROMP of MNI, CTA5
and G3 was precipitated, dried and analysed and subsequently
redissolved and exposed to HNI (300 equiv, 0.075 mol/L, 5 mL/h)
and G3 (0.005 mmol) for the growth of a second polymer block
(Figure 5). GPC characterisation after polymerizing the first (Mn
Acknowledgements
(CHCl3) = 7100 g mol-1, Đ = 1.18) and second monomer (Mn
GPC
The authors thank the Swiss National Science Foundation for
financial support.
(CHCl3) = 22500 g mol-1, Đ = 1.36) revealed the formation of
GPC
a diblock copolymer (Figure 5).
Polymers obtained by catalytic living ROMP are noticeably less
coloured than those obtained by classical living ROMP
(Supporting Information). To quantify the residual ruthenium in
our catalytic living ROMP polymer, two similar molecular weight
and dispersity polymers were synthesised by catalytic and
classical living ROMP (Supporting Information). To emphasise
Keywords: living catalytic polymerization • olefin metathesis •
chain transfer agents • ring opening polymerization • ring strain
4
This article is protected by copyright. All rights reserved.

10.1002/anie.201907921
Angewandte Chemie International Edition
COMMUNICATION
COMMUNICATION
P. Liu, M. Yasir and Prof. Dr. A. F. M.
Kilbinger*
Page No. xxxx – Page No.xxxx
Catalytic Living Ring Opening
Metathesis Polymerisation:The
importance of Ring Strain in Chain
Transfer Agents
1
P. Liu, C. Ai, Industrial & Engineering Chemistry Research 2018, 57, 3807-3820.
Y. Chen, M. M. Abdellatif, K. Nomura, Tetrahedron 2018, 74, 619-643.
2
3
C. Slugovc in Industrial applications of olefin metathesis polymerization in Olefin Metathesis (Eds.: Grela, K.), John Wiley & Sons, Inc. Hoboken, N. J, 2014,
Ch. 10, pp. 329-333.
A. E. Madkour, A. H. R. Koch, K. Lienkamp, G. N. Tew, Macromolecules 2010, 43, 4557–4561.
K. D. Camm; D. E. Fogg, NATO Science Series, II: Mathematics, Physics and Chemistry 2007, 243, 285-303.
S. Hilf, A.F.M. Kilbinger, Nat. Chem. 2009, 1, 537-546.
J. M. Fishman, L. L. Kiessling, Angew. Chem. Int. Ed. 2013, 52, 5061-5064.
E. M. Kolonko, J. K. Pontrello, S. L. Mangold, L. L. Kiessling, J. Am. Chem. Soc. 2009, 131, 7327-7333.
K. Nomura, M. M. Abdellatif, Polymer 2010, 51, 1861-1881.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Y. Chen, M. M. Abdellatif, K. Nomura, Tetrahedron 2018, 74, 619-643.
S. Sutthasupa, M. Shiotsuki, F. Sanda, Polymer Journal 2010, 42, 905–915.
H. Clavier, K. Grela, A. Kirschning, M. Mauduit, S. P. Nolan, Angew. Chem. Int. Ed. 2007, 46, 6786–6801.
W. J. Sommer, M. Weck, Coord. Chem. Rev. 2007, 251, 860–873.
M. R. Buchmeiser, Chem. Rev. 2009, 109, 303–321.
J. H. Cho, B. M. Kim, Org. Lett. 2003, 5, 531–533.
H. Wang, S. N. Goodman, Q. Dai, G. W. Stockdale, W. M. Clark, Org. Process Res. Dev. 2008, 12, 226–234.
H. D.Maynard, R. H. Grubbs, Tetrahedron Lett. 1999, 40, 4137–4140.
Y. M. Ahn, K. L. Yang, G. I. Georg, Org. Lett. 2001, 3, 1411–1413.
L. A. Paquette, J. D. Schloss, I. Efremov, F. Fabris, F. Gallou, J. M. Andino, J. Yang, Org. Lett. 2000, 2, 1259–1261.
J. Mendez-Andino, L. A. Paquette, Org. Lett. 2000, 2, 1263–1265.
D. W. Knight, I. R. Morgan, A. J. Proctor, Tetrahedron Lett. 2010, 51, 638–640.
W. Liu, P. J. Nichols, N. Smith, Tetrahedron Lett. 2009, 50, 6103–6105.
A. Löber, A. Verch, B. Schlemmer, S. Höfer, B. Frerich, M. R. Buchmeiser, Angew. Chem. Int. Ed. 2008, 47, 9138–9141.
N. K. Yee, V.Farina, I. Houpls, N. Haddad, R. P. Frutos, F. Gallou, X. J. Wang, X. Wei, R. D. Simpson, X. Feng, V. Fuchs, Y. Xu, J. Tan, L. Zhang, J. Xu, L.
L. S. Keenan, J. Vitous, M. Ridges, E. M. Spinelll, M. Johnson, J. Org. Chem. 2006, 71, 7133–7145.
V. Farina, C. Shu, X. Zeng, X. Wei, Z. Han, N. K. Yee, C. H. Senanayake, Org. Process Res. Dev. 2009, 13, 250–254.
H. Wang, H. Matsuhashi, B. D. Doan, S. N. Goodman, X. Ouyang, W. M. Clark Jr, Tetrahedron 2009, 65, 6291–6303.
B. R. Galan, K. P. Kalbarczyk, S. Szczepankiewicz, J. B Keister, S. T. Diver, Org. Lett. 2007, 9, 1203–1206.
M. Lindmark-Hamberg, K. B. Wagener, Macromolecules 1987, 20, 2949–2951.
S. E. Lehman, K. B. Wagener, in Handbook of Metathesis (Eds.: Grubbs, R. H.), Wiley-VCH, 2003, Ch. 3.9, 283–353.
T. W. Baughman, K. B. Wagener, in Advances in Polymer Science (Eds.:Buchmeiser, M.), Springer, 2005, Vol. 176, 1–42.
M. A. Hillmyer, R. H. Grubbs Macromolecules 1993, 26, 872-874.
M. K. Mahanthappa, F. S. Bates, M. Hillmyer, Macromolecules 2005, 38, 7890-7894.
S. M. Banik, B. L, Monnot, R. L. Weber, M. K. Mahanthappa, Macromolecules 2011, 44, 7141-7148.
X. Michel, S. Fouquay, G. Michaud, F. Simon, J.-M. Brusson, J.-F. Carpentier, S. M. Guillaume, Polym. Chem. 2016, 7, 4810-4823.
X. Michel, S. Fouquay, G. Michaud, F. Simon, J.-M. Brusson, P. Roquefort, T. Aubry, J.-F. Carpentier, S. M. Guillaume, Polym. Chem. 2017, 8, 1177–1187.
C. W. Bielawski, D. Benitez, T. Morita, R. H. Grubbs, Macromolecules 2001, 34, 8610–8618.
M. R. Radlauer, M. E. Matta, M. A. Hillmyer, Polym. Chem. 2016, 7, 6269–6278.
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
H. Katayama, H. Urushima, F. Ozawa, Chem. Lett. 1999, 28, 369–370.
H. Katayama, Y. Fukuse, Y. Nobuto, K. Akamatsu, Macromolecules 2003, 36, 7020–7026.
P. Liu, M. Yasir, A. Ruggi, A. F. M., Kilbinger, Angew. Chem. Int. Ed. 2018, 57, 914-917.
M. Yasir, P. Liu, I. K. Tennie; A. F. M. Kilbinger, Nat. Chem. 2019, 11, 488-494.
R. A. Lyndon, G. Zwfifel, Synthesis 1974, 9, 658-659.
D.P. White, J.C. Anthony, A.O. Oyefeso J. Org. Chem. 1999, 64, 7707-7716.
J. B. Matson, S. C. Virgil, R. H. Grubbs, J. Am. Chem. Soc. 2009, 131, 3355–3362.
5
This article is protected by copyright. All rights reserved.