High norbornene incorporation in ethylene-norbornene copolymerization with a bis(α-alkyloxoimine) titanium-MAO catalyst

Article abstract of DOI:10.1007/s11426-010-4021-0

A novel bis(α-alkyloxoimine) titanium(IV) complex was synthesized and used as a catalyst precursor to catalyze homo-and copolymerization of ethylene and norbornene. The titanium complex activated with methylalumoxane exhibits good activities for the homopolymerizations of ethylene and norbornene under high temperature to produce high-molecular-weight linear polyethylene and vinyl-type polynorbornene, respectively. Ethylene-norbornene copolymers with high molecular weight can also be produced by this catalyst. The incorporation of norbornene from 0 to 76 mol% in the copolymers can be controlled by varying the charged norbornene. ¹³C NMR analyses show that the microstructures of the ethylene-norbornene copolymers with low norbornene incorporation are predominantly alternated and isolated norbornene units, while those with high norbornene incorporation are random polymers containing long norbornene sequences. Science China Press and Springer-Verlag Berlin Heidelberg 2010.

Full text of DOI:10.1007/s11426-010-4021-0

SCIENCE CHINA
Chemistry
August 2010 Vol.53 No.8: 1634–1640
doi: 10.1007/s11426-010-4021-0
• ARTICLES •
· SPECIAL TOPIC · Advances in Principles of Polymerization
High norbornene incorporation in ethylene-norbornene
copolymerization with a bis(-alkyloxoimine)
titanium-MAO catalyst
GAO HaiYang1,2, HU Hao1 & WU Qing1,2*
1Institute of Polymer Science, School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University,
Guangzhou 510275, China
2Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education; Sun Yat-Sen (Zhongshan) University,
Guangzhou 510275, China
Received February 28, 2010; accepted April 28, 2010
A novel bis(-alkyloxoimine) titanium(IV) complex was synthesized and used as a catalyst precursor to catalyze homo- and
copolymerization of ethylene and norbornene. The titanium complex activated with methylalumoxane exhibits good activities
for the homopolymerizations of ethylene and norbornene under high temperature to produce high-molecular-weight linear
polyethylene and vinyl-type polynorbornene, respectively. Ethylene-norbornene copolymers with high molecular weight can
also be produced by this catalyst. The incorporation of norbornene from 0 to 76 mol% in the copolymers can be controlled by
varying the charged norbornene. 13C NMR analyses show that the microstructures of the ethylene-norbornene copolymers with
low norbornene incorporation are predominantly alternated and isolated norbornene units, while those with high norbornene
incorporation are random polymers containing long norbornene sequences.
catalyst, ethylene, norbornene, polymerization, copolymerization
copolymerization of ethylene and norbornene [7–9], more
attention has been concentrated on group 4 titanium and
zirconium catalysts [10–15].
1 Introduction
Cyclic olefin copolymers (COCs) like poly(ethylene-co-
norbornene)s have attracted considerable attention with re-
markable properties, such as thermal resistance (high glass
transition temperature, Tg), excellent optical transparency,
and high refractive indices [1–6]. These properties can be
precisely controlled by varying monomer composition, se-
quence distribution, and the stereoregularity of norbornene
units in the copolymers, which depends on the different
structure of the employed catalyst including metal center
and ligand structure. Since Kaminsky initially reported ho-
mogeneous metallocene/methylaluminoxane (MAO) for the
Both group 4 metallocenes [16–18] and constrained-
geometry catalysts (CGCs) [19–21] showed high catalytic
activities for copolymerization of ethylene and norbornene
(NBE). Many non-metallocenes titanium complexes such as
bis(pyrrolide-imine) titanium [22, 23], bis(imino-indolide)
titanium [24], bis(-enaminoketonato) titanium [25], [2-
(2,6-dialkylphenylamino)-1-phenylethoxy TiCl2] [26], tita-
nium complexes bearing tridentate [ONXR] (X = S, O, Se,
P) ligands [27, 28], and bis(-diketiminato) titanium [29]
were also used to effectively copolymerize ethylene (E) and
norbornene (NBE) in the presence of MAO or MMAO.
However, fewer successful examples have appeared for the
efficient synthesis of random, high-molecular-weight co-
*Corresponding author (email: ceswuq@mail.sysu.edu.cn)
© Science China Press and Springer-Verlag Berlin Heidelberg 2010
chem.scichina.com
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GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
1635
polymers with high NBE contents (> 50 mol%), which
typically possess high Tg (> 150 °C). This is not only be-
cause both the polymerization activity and molecular
weights of the products generally decrease with increasing
the NBE contents, but also because the microstructure of the
copolymer mainly possesses alternating E-NBE sequences
and the isolated NBE units due to the difficulty of achieving
successive insertion of NBE. Increasing NBE incorporation
in E-NBE copolymer and synthesis of random E–NBE co-
polymers with high Tg (>150 °C) thereby remain a great
challenge.
Our previous study shows that the bis(benzoin) titanium
catalyst bearing a keto-alkoxide ligand can effectively cata-
lyze the copolymerization of ethylene and norbornene to
produce E-NBE copolymers with high incorporated content
of NBE (51 mol%). The dyad (NN), and triad (NNN) se-
quences of NBE were also determined in the microstructure
of the copolymer because the electronegative alkoxide
group makes the titanium center prone to be attacked by
norbornene monomers [30]. In this paper, we synthesized a
new [N,O] bis(-alkyloxoimine) titanium complex on the
basis of the structure of bis(benzoin) titanium, and investi-
gated its catalytic properties on homo- and copolymeriza-
tion of ethylene and norbornene. Random E-NBE copoly-
mers with high norbornene incorporation (76 mol%) were
first prepared in good catalytic activity.
spectrometry using electrospray ionization (EI) with CH3CN
as the fluent phase. H NMR spectra were carried out on
1
Mercury-plus 300 MHz NMR spectrometers at room tem-
perature in CDCl3 solution for organic compounds. 1H
NMR spectrum of the polynorbornene was recorded on
Mercury-plus 300 MHz NMR spectrometer at 80 °C with
o-dichlorobenzene-d4 as the solvent. 13C NMR spectra of
the polymer samples were recorded on a Varian INOVA
500 MHz spectrometer in a 4:1 mixture of o-dichlorobenzene
and o-dichlorobenzene-d4 (2.5 mL) at 120 °C with o-di-
chlorobenzene-d4 as the reference. The norbornene contents
in the copolymer were calculated from the 13C NMR spectra
using the following eq. (1) [20]:
XN  1 3 IC1/C4  IC2/C3  2IC7 ICH2
(1)


where IC1/C4 is integral of signals between 37.0 and 44.0
ppm, IC2/C3 is integral of signals between 44.5 and 56.0 ppm,
IC7 is integral of signals between 33.0 and 36.5 ppm, and
ICH2 is integral of signals between 28.0 and 32.5 ppm. The
molecular weight and molecular weight distribution of the
polymer samples were determined at 135 °C by a Waters
Alliance GPC2000 type high-temperature chromatograph.
1,2,4-Trichlorobenzene (TCB) was employed as the solvent
at a flow rate of 1.0 mL/min. The calibration curve was es-
tablished with polystyrene standards. The molecular weight
of the PE samples was estimated by viscosimetric analysis,
and the intrinsic viscosity of the polymer samples was
measured in decalin at 135 °C using an Ubbelohde visco-
simeter. The Mark-Houwink constants were taken from
previous reports, and the viscosity-average molecular
2 Experimental
weights (Mv) were calculated using equation (2) for PE30
All manipulations involving air and moisture sensitive
compounds were carried out under an atmosphere of dried
and purified nitrogen with standard vacuum-line, Schlenk,
or glovebox techniques.
,
0.7
  6.2 104 M
(2)
 
v
DSC analysis was conducted with a Perkin Elmer DCS-7
system. The DSC curves were recorded at second heating
curves from 50 to 350 °C at a heating rate of 10 °C/min
and a cooling rate of 10 °C/min.
2.1 Materials
Solvents were purified using standard procedures. Methyl-
ene chloride was distilled from calcium hydride, and hexane
was distilled from P2O5 under nitrogen. The n-butyllithium
(n-BuLi) solution in hexane (2.86 M) was purchased from
Aldrich. Norbornene (bicyclo[2.2.1] hept-2-ene; Acros) was
purified by distillation over potassium and used as a solu-
tion in toluene. Benzoin was recrystallized from ethanol
before use. Titanium tetrachloride was distilled prior to use.
MAO was prepared by partial hydrolysis of trimethylalu-
minum (TMA) in toluene at 0–60 °C with Al2(SO4)318H2O
as the water source. Other commercially available reagents
were purchased and used without purification.
2.3 Synthesis of complex 4
Benzoin 1 (2.5 g, 11.9 mmol), 1.11 g (11.9 mmol) aniline,
catalytic amount of formic acid, and 15 mL ethanol were
placed in a 50 mL flask equipped with a condenser. After
refluxing for 8 h, the mixtures were allowed to cool to room
temperature to yield yellow solid. The crude product was
recrystallized from ethanol to yield compound 2 in 68%
1
yield. H NMR (300 MHz, CDCl3, ppm) : 7.92–6.50 (m,
15H). EI-MS (m/z): 286 (M+1). Anal. calcd for C20H15NO: C
84.19; H 5.30; N 4.91. Found: C 84.12; H 5.28; N 4.97.
To a stirred solution of 2 (1.00 g, 3.48 mmol) in toluene
(60 mL) at 78 °C was added a 2.86 M n-BuLi hexane solu-
tion (1.22 mL, 3.49 mmol) dropwise over 5 min. The mix-
tures were allowed to warm to room temperature slowly and
stirred for 2.5 h. TiCl4 (0.191 mL, 1.74 mmol) in toluene
2.2 Measurement
Elemental analyses were performed on a Vario EL micro-
analyzer. Mass spectrum for the complex was measured on
a Thremo LCQ DECA XP liquid chromatography-mass

1636
GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
(30.0 mL) was dropped into the resulting mixture at 78 °C
with stirring over 30 min. The mixtures were allowed to
warm to room temperature slowly and stirred for 16 h, and
then filtered. The filtrate was concentrated in vacuum to
10 mL. Dried hexane (40.0 mL) was added into the concen-
trated solution, and the mixture was stirred for 10 min and
then filtered. The residual solid was washed three times
with hexane. Drying in vacuo produced 1.18 g of the de-
1
sired titanium complex 4. Yield: 84.3%. H NMR (300
MHz, CDCl3): 7.99–6.52 (m, 30H), 2.53 (t, 4H), 1.34 (m,
4H), 0.83 (m, 4H), 0.38 (t, 6H). EI-MS (m/z): 983.4
(MCl+3CH3CN+C7H8)+, 942.4(MCl+2CH3CN+C7H8)+,
344.2 (Ligand+H)+. Anal. calcd for C48H48Cl2N2O2Ti: C
71.73; H 6.02; N 3.49. Found: C 71.15; H 5.93; N 3.40.
Scheme 1 The synthetic route of bis(-alkyloxoimine)titanium complex 4.
2.4 Norbornene polymerization
tained by reduction of carbonyl. Reaction of the lithium salt
3 with TiCl4 in toluene yielded titanium(IV) complex 4
chelating two ligands in high yield (84.3%). The structure
In a typical procedure, the appropriate MAO solid was in-
troduced into a 50 mL round-bottom glass flask placed in an
oil bath at a prescribed temperature, and then the desired
amount of NBE and toluene was added via a syringe. The
polymerization was started by injecting a precursor 4 solu-
tion and the reaction mixture was continuously stirred for an
appropriate period at the polymerization temperature. Po-
lymerizations were terminated by the addition of acidic
ethanol (ethanol-HCl, 95:5). The resulting precipitated poly-
mers were collected and treated by filtering, washing with
ethanol several times, and drying under vacuum at 60 °C to a
constant weight.
1
of complex 4 was fully characterized by H NMR, EI-MS
and elemental analysis (see Experimental). Four peaks at
the aliphatic region from 2.53 to 0.38 ppm appear in the 1H
NMR spectrum of 4, which is indicative of the presence of
butyl group.
3.2 Ethylene homopolymerization
In the presence of MAO, bis(-alkyloxoimine) titanium
complex 4 was investigated as a catalyst precursor for eth-
ylene polymerization and the polymerization data are sum-
marized in Table 1. It shows that under a constant [Al]/[Ti]
mole ratio ([Al]/[Ti] = 300), the catalytic activity for ethyl-
ene polymerization increased with a gradual increase of
reaction temperature and reached a maximal value of 0.53 ×
105 gPE (mol Ti h)1 at 70 °C. Typically, an apparent de-
crease in catalytic activity can be observed at relatively high
temperature due to thermal instability of the active species
[31] and low ethylene solubility in solvent [32]. Previously,
we reported that bis(benzoin) titanium catalyst exhibits the
highest activity for ethylene polymerization at 30 °C, and
higher temperature leads to a decrease in activity [30]. Ap-
parently, bis(-alkyloxoimine) titanium catalyst has better
thermal stability than bis(benzoin) titanium catalyst. A rea-
sonable explanation is that the imine group in -alkyloxo-
imine ligand has the stronger coordination interaction with
titanium metal than carbonyl group in benzoin ligand. Be-
sides, high temperature is favorable for activation of tita-
nium complex 4, thus high activities can be observed at
high temperatures [26, 33].
2.5 Ethylene polymerization and ethylene-norbornene
copolymerization
A 50 mL round-bottom glass flask was charged with tolu-
ene, prescribed amount of MAO and NBE (for copolymeri-
zation of ethylene and norbornene) at initialization tem-
perature. The system was maintained by continuously stir-
ring for 5 min, and then the titanium complex solution was
charged into the flask. The pressure was maintained by con-
tinuously feeding ethylene gas and the reaction was carried
out for a certain time. Polymerization was terminated by the
addition of acidic ethanol (ethanol-HCl, 95:5). The resulting
precipitated polymers were collected and treated by filtering,
washing with ethanol several times, and drying under vac-
uum at 60 °C to a constant weight.
3 Results and discussion
3.1 Synthesis of bis(-alkyloxoimine) titanium complex 4
13C NMR analysis of the PE prepared at 50 °C shows
solely one peak at 30.0 ppm, and no signals of branching
carbons can be observed (Figure 1). DSC analysis shows
that the polymer products display a range of the melting
temperatures (Tm) from 134.4 to 137.3 °C and high crystal-
The synthetic route of bis(-alkyloxoimine) titanium com-
plex 4 is shown in Scheme 1. Condensation of benzoin 1
with 1.0 equiv aniline afforded the keto-imine compound 2
in high yield. Compound 2 was treated with 1.0 equiv
n-BuLi, and -alkyloxoimine lithium compound 3 was ob-

GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
1637
Table 1 Ethylene polymerizations with 4/MAO
Table 2 Norbornene polymerizations with 4/MAO
b)
Entry Tp (°C) Yield (g) Activity a)
Mv
Tm c) (°C) Xc d) (%)
Entry
NBE (g)
Tp (°C)
10
Yield (g)
0.018
0.029
0.90
Activity a)
1
2
3
4
10
30
50
70
0.13
0.21
0.35
0.53
0.13
0.21
0.35
0.53
1.44
1.30
1.11
0.97
135.0
137.3
136.2
134.4
63.2
64.1
61.8
60.4
1
4
4
4
4
2
1
0.02
0.03
0.90
2.95
0.66
0.28
2
30
3
4 b)
50
70
0.59
Polymerization conditions: complex 4, 10 mol; [Al]/[Ti] = 300; ethyl-
ene, 0.05 MPa; reaction time, 60 min, solvent, toluene; total volume, 20
mL. a) In unit of 105 gPE (mol Ti h)1. b) In unit of 106 g/mol, the intrinsic
viscosities were measured in decalin at 135 °C according to eq. (2). c)
Determined by DSC. d) Determined by DSC, calculated with respect to
standard Hf = 293 J/g of polyethylene single crystal.
5
70
0.66
6
70
0.28
Polymerization conditions: complex 4, 10 mol; [Al]/[Ti]=300; reaction
time, 60 min; solvent, toluene; total volume, 20 mL. a) In unit of
105gPNBE (mol Ti h)1. b) Reaction time, 12 min
(entries 5, 6 in Table 2). These results further confirm that
bis(-alkyloxoimine) titanium catalyst has a good thermal
stability. Most previous publications reported that non-
metallocene titanium complexes had no activity or low ac-
tivity for norbornene homopolymerization [22–25, 29],
while bis(-alkyloxoimine) titanium 4 exhibited good activ-
ity for NBE polymerization at high temperature. This pro-
vides a possibility for synthesis of the ethylene-norbornene
copolymer with high norbornene incorporation.
The obtained polynorbornenes (PNBEs) are white solid
with poor solubility in common organic solvents, thus the
molecular weight of PNBEs is hardly determined by GPC.
The IR spectrum revealed no traces of double bonds, which
often appear at 1620–1680, 966 and 735 cm1, while it re-
vealed the existence of vibration bands of bicyclics of no-
Figure 1 13C NMR spectrum of PE catalyzed by 4/MAO at 50 °C.
linities (Xc > 60%), indicating that the produced polymers
possess linear structures with virtually no branching. The
poor solubility of the high-molecular-weight linear PEs in
trichlorobenzene made it difficult to analyze by high tem-
perature GPC, thus the molecular weight was calculated
from the viscosity determined by an Ubbelohde viscosime-
ter in decalin at 135 °C. The data listed in Table 1 indicate
that the molecular weights of the obtained PEs are very high
up to 106 g/mol, and decrease uniformly with the increase of
polymerization temperature because of an acceleration of
chain termination reaction.
1
rbornene at 941 cm1. H NMR spectrum of the PNBE ob-
tained at 50 °C (0.86–2.38 ppm) (Figure 2) further demon-
strated no traces of any double bond, ensuring the occur-
rence of vinyl-type polymerization rather than ring-opening
metathesis polymerization [34–37].
3.4 Ethylene-norbornene copolymerization
High activity of bis(-alkyloxoimine) titanium-MAO cata-
lyst for norbornene homopolymerization allows us to pre-
pare the ethylene-norbornene copolymers with various mi-
crostructures. Copolymerizations of ethylene and NBE were
carried out with 4 activated with MAO at various NBE
feeds under 70 °C and 0.05 MPa ethylene pressure. Co-
polymerization data in Table 3 show that the copolymeriza-
tion activity and NBE incorporation in the copolymer are
3.3 Norbornene homopolymerization
Norbornene polymerizations were also carried out using
4/MAO, and the results are listed in Table 2. Polymerization
results illustrate that increasing temperature also leads to a
significant increase in catalytic activity for norbornene po-
lymerizations. For example, when norbornene polymeriza-
tions were carried out below 30 °C, low catalytic activities
were observed. When the polymerization temperature was
50 °C, a significant increase in the activity was observed in
the factor of 30. Furthermore, we discovered that the po-
lymerization was so rapid at 70 °C that stirring was stopped
within 12 min, and complex 4 exhibited the highest activity
(2.95 × 105 gPNBE (mol Ti h)1) for NBE polymerization.
Reducing the monomer concentration allows long-standing
polymerization (60 min) and leads to a decrease in polym-
erization activity, while good activities can still be achieved
Figure 2 1H NMR spectrum of polynorbornene prepared by 4/MAO at
50 °C.

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GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
Table 3 Ethylene-norbornene copolymerizations with 4/MAO
d)
Entry
NBE (g)
Yield (g)
0.64
Activity a)
0.64
XN b) (mol%)
12.7
Tg/Tm c) (°C)
30.5/122.4
39.2/124.1
67.0/124.7
68.0/124.7
110.0/123.6
165.4/-–
Mw d) (106 g/mol)
Mw/Mn
2.18
2.11
2.25
n.d.
1
2
3
4
5
6
7
8
0.2
0.4
0.8
1
0.52
0.72
0.91
n.d.e)
n.d.
0.64
0.64
19.0
0.61
0.61
25.3
0.63
0.63
30.0
2
0.75
0.75
35.4
n.d.
3
1.06
1.06
52.9
n.d.
n.d.
4
1.34
1.34
75.7
242.5/–
n.d.
n.d.
8
2.67
2.67
76.0
244.8/–
n.d.
n.d.
Polymerization conditions: complex 4, 10 mol; MAO, [Al]/[Ti] = 300; ethylene, 0.05 MPa pressure; reaction temperature, 70 °C; reaction time, 60 min;
solvent, toluene; total volume, 20 mL. a) In unit of 105 g E-NBE (mol Ti h)1. b) Incorporated NBE content in copolymer, calculated by 13C NMR. c) Deter-
mined by DSC. d) Determined by GPC. e)Not determined.
affected by the quantities of charged NBE. Unlike bis (pyr-
rolide-imine) titanium catalysts [22, 23], bis(-diketiminato)
titanium catalysts [29], and bis(benzoin) titanium catalyst
[30], as the quantities of charged NBE increases (and
thereby the NBE/E molar ratio increases), the catalytic
activity remains practically unchanged and then increases
apparently. This result is likely to arise from good perform-
ance of bis(-alkyloxoimine) titanium catalyst for NBE
polymerization. Besides, increasing the charged NBE
monomer raised the incorporation of NBE in the copolymer.
The NBE content in the copolymer reached a maximal
value of around 76%. It is the first successful example of
synthesis of ethylene–norbornene copolymerization with
above 60% NBE incorporation using titanium based cata-
Figure 3 13C NMR spectra of E-NBE copolymers produced by 4/MAO.
lysts. Additionally, molecular weights of the obtained co-
(a) XN = 19.0 mol%; (b) XN = 35.4 mol%; (c) XN = 75.7 mol%.
polymers are very high (106 g/mol) and increase with an
increase in the quantities of charged NBE (entries 1–3 in
observed in low intensity. The signals at 29.7, 31.4, 28.3,
31.7 ppm (C5/C6), 33.7 ppm (C7), 41.2 and 42.7 ppm
(C1/C4), 50.3 and 49.3 ppm (C2/C3) can be assigned to
racemic- and meso-ENNE sequences. 13C NMR spectrum
(Figure 3(c)) of the E-NBE copolymer with 75.7% NBE
incorporation is apparently different from those shown in
Figures 3(a) and (b). Resonances at regions from 56 to 50
ppm and 41 to 30 ppm can be unambiguously assigned to
long successive NBE sequences ((N)n, n > 6) [36], sug-
gesting that long NBE runs present in the copolymer. The
existence of long successive NBE sequences in the copoly-
mers arises from the high activity of bis(-alkyloxoimine)
titanium catalyst for NBE polymerization.
As shown in Figure 4, the DSC curves of the copolymers
exhibit different glass transition temperatures (Tg) depend-
ing upon NBE incorporation in the copolymers. The co-
polymers containing high NBE incorporation show a single
Tg, while those containing low NBE incorporation show
simultaneously Tg and melting temperature (Tm). As shown
in Figure 5, there is a linear relationship between NBE incor-
poration in the copolymer and Tg. The copolymers with low
NBE incorporation show apparent melting peaks (120 °C),
Table 3). Higher quantities of charged NBE lead to higher
molecular weights of the copolymers, thus the copolymers
are poorly soluble in solvent and their molecular weights
are not determined by high temperature GPC. The molecu-
lar weight distributions of the copolymers are close to 2 and
appear as a unimodal, indicating that the polymerization
products are the true copolymers instead of blends of the
homopolymers.
Microstructures of the E-NBE copolymers with various
NBE incorporations were investigated by 13C NMR spectra.
The signals are assigned according to the previous reports
[10, 20] and our results [29, 30]. As shown in Figure 3(a),
the spectrum of the copolymer containing 19% NBE units
displays solely eight major peaks respectively at 29.9 ppm
(successive E sequences), 30.4 ppm (isolated E + C5/C6),
30.9 ppm (C5/C6 + E sequence), 33.1 ppm (C7), 41.7, 42.2
ppm (C1/C4), 47.4 and 48.0 ppm (C2/C3), which are char-
acteristics of the NBE units existing as alternating (ENEN)
and isolated (ENEE) sequences. In the 13C NMR spectrum
(Figure 3(b)) of the E-NBE copolymer with a higher level
of NBE incorporation (NBE% = 35.4 mol%), several addi-
tional signals assigned to the norbornene dyad (NN) can be

GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
1639
ethylene and norbornene. The ethylene-norbornene copoly-
mers with different norbornene microstructures ranging
from alternated and isolated ones at low norbornene incor-
poration to random ones at high norbornene incorporation
can be synthesized by controlling the charged norbornene.
With 8 g norbornene addition at 70 °C, a random ethyl-
ene-norbornene copolymer with 76 mol% norbornene in-
corporation, which possesses high Tg of 244.8 °C, was first
synthesized, and long norbornene sequence was observed in
the copolymer.
This work was supported by the National Natural Science Foundation of
China (20734004 & 20974125), the Science Foundation of Guangdong
Province (8251027501000018), and the Ministry of Education of China
(Foundation for Ph. D. Training).
1
2
3
Cherdron H, Brekner MJ, Osan F. Cycloolefin copolymer: A new
class of transparent thermoplastics. Angew Makromol Chem, 1994,
223: 121–133
Kaminsky W, Engehause R, Kopf J. A tailor-made metallocene for
the copolymerization of ethene with bulky cycloalkenes. Angew
Chem Int Ed Engl, 1995, 34: 2273–2275
Rische T, Waddon AJ, Dickinson LC, McKnight WJ. Microstructure
and morphology of cycloolefin copolymers. Macromolecules, 1998,
31: 1871–1874
Figure 4 DSC curves of E-NBE copolymers prepared by 4/MAO. (a) XN
= 12.7 mol%; (b) XN = 19.0 mol%; (c) XN =25.3 mol%; (d) XN =30.0 mol%;
(e) XN = 35.4 mol%; (f) XN = 75.7 mol%.
4
5
6
Lamonte RR, Nally DM. Cyclic olefin copolymers. Adv Mater
Process, 2001, 159: 33–36
Kaminsky W. Olefin polymerization catalyzed by metallocenes. Adv
Catal, 2001, 46: 89–159
Kaminsky W, Beulich I, Arndt-Rosenau M. Copolymerization of
ethene with cyclic and other sterically hindered olefins. Macromol
Symp, 2001, 173: 211–225
7
Kaminsky W, Bark A, Arndt M. New polymers by homogenous zir-
conocene/aluminoxane catalysts. Makromol Chem, Macromol Symp
1991, 47: 83–93
8
9
Kaminsky W, Bark A, Steiger R. Stereospecific polymerization by
metallocene/aluminoxane catalysts. J Mol Catal, 1992, 74: 109–119
Kaminsky W, Noll A. Copolymerization of norbornene and ethene
with homogeneous zirconocenes/methylaluminoxane catalysts. Polym
Bull, 1993, 31: 175–182
10 Ruchats D, Fink G. Ethene-norbornene copolymerization using ho-
mogenous metallocene and half-sandwich catalysts: Kinetics and re-
lationships between catalyst structure and polymer structure. 2.
Comparative study of different metallocene- and half-sandwich/ me-
thylaluminoxane catalysts and analysis of the copolymers by 13C nu-
clear magnetic resonance spectroscopy. Macromolecules, 1998, 31:
4674–4680
11 Ruchats D, Fink G. Ethene-norbornene copolymerization with ho-
mogeneous metallocene and half-sandwich catalysts: Kinetics and
relationships between catalyst structure and polymer structure. 3.
Copolymerization parameters and copolymerization diagrams.
Macromolecules, 1998, 31, 4681–4683
Figure 5 Dependence of glass transition temperature (Tg) upon NBE
incorporation in the copolymer.
which is a result of relatively long ethylene sequences. The
melting temperatures of the copolymer are lower than those
of the polyethylenes, which can be attributed to long PE
sequences containing very low isolated NBE unit
((E)mN(E)n) [9, 30].
12 Ruchats D, Fink G. Ethene-norbornene copolymerization with ho-
mogeneous metallocene and half-sandwich catalysts: Kinetics and
relationships between catalyst structure and polymer structure. 4.
Development of molecular weights. Macromolecules, 1998, 31,
4684–4686
13 Bergstrom CH, Sperlich BR, Ruotoistenmaki J, Seppala JV. Investi-
gation of the microstructure of metallocene-catalyzed norbornene-
ethylene copolymers using NMR spectroscopy. J Polym Sci A: Polym
Chem, 1998, 36: 1633–1638
4 Conclusions
Bis(-alkyloxoimine) titanium (IV) complex is a novel
catalyst precursor for homo- and copolymerization of eth-
ylene and norbornene. The most striking feature of the
catalytic system is its good thermal stability. Increasing
polymerization temperature leads to a significant increase in
the catalytic activity for homo- and copolymerizations of
14 Lee BY, Kim YH, Won YC, Han JW, Suh WH, Lee IS, Chung YK, Song
KH. Synthesis of [2,2′-methylenebis(1,3-dimethyl cyclopentadienyl)]
zirconium dichloride and its reactivity in ethylene-norbornene

1640
GAO HaiYang, et al. Sci China Chem August (2010) Vol.53 No.8
copolymerization. Organometallics, 2002, 21: 1500–1503
8289–8296
15 Ruchats D, Fink G. Ethene-norbornene copolymerizations using two
different homogeneous metallocene catalyst systems and investiga-
tions of the copolymer microstructure. J Mol Catal A: Chem, 2003,
203: 101–111
27 Wang C, Sun XL, Guo YH, Gao Y, Liu B, Ma Z, Xia W, Shi LP,
Tang Y. Novel titanium catalysts bearing an [O, N, S] tridentate
ligand for ethylene homo- and copolymerization. Macromol Rapid
Commun, 2005, 26: 1609–1614
16 Nomura K, Tsubota M, Fujiki M. Efficient ethylene/norbornene
copolymerization by (aryloxo)(indenyl)titanium(IV) complexes-MAO
catalyst system. Macromolecules, 2003, 36, 3797–3799
17 Wang W, Tanaka T, Tsubota M, Fujiki M, Yamanaka S, Nomuraa K.
Effect of cyclopentadienyl fragment in copolymerization of ethylene
with cyclic olefins catalyzed by non-bridged (aryloxy) (cyclopenta-
dienyl) titanium(IV) complexes. Adv Synth Catal, 2005, 347:
433–446
28 Gao ML, Wang C, Sun XL, Qian CT, Ma Z, Bu SZ, Tang Y, Xie ZW.
Ethylene-norbornene copolymerization by new titanium complexes
bearing tridentate ligands: Sidearm effects on catalytic activity.
Macromol Rapid Commun, 2007, 28: 1511–1516
29 Li YF, Gao HY, Wu Q. Homo- and copolymerization of ethylene and
norbornene with bis(-diketiminato) titanium complexes activated
with methylaluminoxane. J Polym Sci A: Polym Chem. 2008, 46:
93–101
18 Nomura K, Wang W, Fujiki M, Liu JY. Notable norbornene (NBE)
incorporation in ethylene-NBE copolymerization catalyzed by non-
bridged half-titanocenes: Better correlation between NBE incorpora-
tion and coordination energy. Chem Commun, 2006, 2659–2661
19 McKnight AL, Waymouth RM, Ethylene/norbornene copolymeriza-
tions with titanium CpA catalysts. Macromolecules, 1999, 32:
2816–2825
20 Hasan T, Ikeda T, Shiono T. Ethene-norbornene copolymer with high
norbornene content produced by ansa-fluorenyl amidodimethyltita-
nium complex using a suitable activator. Macromolecules, 2004, 37:
8503–8509
30 Hu H, Gao HY, Song KM, Liu FS, Long JM, Zhang L, Zhu FM, Wu
Q. Novel bis(benzoin) titanium catalyst for homo- and copolymeriza-
tion of norbornene with ethylene: Synthesis, characterization and
catalytic properties. Polymer, 2008, 49: 4552–4558
31 Sudhakar P, Amburose CV, Sundararajan G, Nethaji M. A new class
of mono- and tetra-nuclear titanatranes: Synthesis, structure, and eth-
ylene polymerization studies. Role of single-sited active species.
Organometallics, 2004, 23: 4462–4467
32 Gao HY, Ke ZF, Pei LX, Song KM, Wu Q. Drastic ligand electronic
effect on anilido-imino nickel catalysts toward ethylene polymeriza-
tion. Polymer, 2007, 48: 7249–7254
21 Naga N. Copolymerization of ethylene with cycloolefins or cyclo-
diolefins by a constrained-geometry catalyst. J Polym Sci A: Polym
Chem, 2005, 43: 1285–1291
22 Yoshida Y, Saito J, Mitani M, Takagi Y, Matsui S, Ishii S, Nakano T,
Kashiwa N, Fujita T. Living ethylene/norbornene copolymerisation
catalyzed by titanium complexes having two pyrrolide-imine chelate
ligands. Chem Commun 2002, 1298–1299
23 Yoshida Y, Mohri J, Ishii S, Mitani M, Saito J, Matsui S, Makio H,
Nakano T, Tanaka H, Onda M, Yamamoto Y, Mizuno A, Fujita T.
Living copolymerization of ethylene with norbornene catalyzed by
bis(pyrrolide-imine) titanium complexes with MAO. J Am Chem Soc.
2004, 126: 12023–12032
24 Zuo WW, Sun WH, Zhang S, Hao P, Shiga A. Highly active ethylene
polymerization and copolymerization with norbornene using bis
(iminoindolide)titanium dichloride-MAO system. J Polym Sci A:
Polym Chem, 2007, 45: 3415–3430
33 Frediani M, Sé meril D, Comucci A, Bettucci L, Frediani P, Rosi L,
Matt D, Toupet L, Kaminsky W. Ultrahigh-molecular-weight poly-
ethylene by using a titanium calix[4]arene complex with high thermal
stability under polymerization conditions. Macromol Chem Phys
2007, 208: 938-945.
34 Gao HY, Guo WJ, Bao F, Gui GQ, Zhang JK, Zhu FM, Wu Q. Mo-
lecular structure, and solution-dependent behavior of nickel com-
plexes chelating anilido-imine donors and their catalytic activity to-
ward olefin polymerization. Organometallcs, 2004, 23: 6273-6280.
35 Gao HY, Zhang JK; Chen Y, Zhu FM, Wu Q. Vinyl-polymerization
of norbornene with novel anilido-imino nickel complexes/methylalu-
minoxane: Abnormal influence of polymerization temperature on
molecular weight of polynorbornenes. J Mol Catal A: Chem, 2005,
240: 178–185
36 Gao HY, Chen Y, Zhu FM, Wu Q. Copolymerization of norbornene
and styrene catalyzed by a novel anilido-imino nickel complex/methylalu-
minoxane system. J Polym Sci A: Polym Chem, 2006, 44: 5237–5246
37 Gao HY, Pei LX, Li YF, Zhang JK, Wu Q. Vinyl polymerization of
norbornene with nickel catalysts bearing [N,N] six-membered chelate
ring: Important influence of ligand structure on activity. J Mol Catal
A: Chem, 2008, 280: 81–86
25 Li XF, Dai K, Ye WP, Pan L, Li YS. New titanium complexes with
two -enaminoketonato chelate ligands: Syntheses, structures, and
olefin polymerization activities. Organometallics, 2004, 23: 1223–1230
26 Vijayakrishna K, Sundararajan G. Non-Cp type titanium precatalysts
for ethylene/norbornene copolymerization. Polymer, 2006, 47: