Synthesis of ethylene/vinyl ester copolymers with pendent linear branches via ring-opening metathesis polymerization of fatty acid-derived cyclooctenes

Article abstract of DOI:10.1002/pola.28606

Fatty acid-derived cyclooctenes, including n-hexanoic acid (M1), n-octanoic acid (M2), lauric acid (M3), and palmitic acid (M4), were prepared as monomers and polymerized by ring-opening metathesis polymerization (ROMP) using Grubbs second-generation cata

Full text of DOI:10.1002/pola.28606

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Synthesis of Ethylene/Vinyl Ester Copolymers with Pendent
Linear Branches via Ring-Opening Metathesis Polymerization
of Fatty Acid-Derived Cyclooctenes
Yuchen Feng, Suyun Jie, Bo-Geng Li
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou
10027, China
3
Correspondence to: S. Jie (E-mail: jiesy@zju.edu.cn)
Received 10 January 2017; accepted 24 March 2017; published online 00 Month 2017
DOI: 10.1002/pola.28606
1
13
ABSTRACT: Fatty acid-derived cyclooctenes, including n-hexa-
noic acid (M1), n-octanoic acid (M2), lauric acid (M3), and pal-
mitic acid (M4), were prepared as monomers and polymerized
by ring-opening metathesis polymerization (ROMP) using
Grubbs second-generation catalyst (G2). In all the cases, the
regio-irregular unsaturated polymers with pendent linear
branches were obtained, which could be saturated by chemical
hydrogenation with TSH/TPA in high conversion, yielding ethyl-
ene/vinyl ester copolymers with pendent linear branches on pre-
cisely every eighth backbone carbon. Both unsaturated and
saturated polymers were amorphous, and their structures were
characterized by FTIR, H and C NMR spectra, and elemental
analysis. Differential scanning calorimetry (DSC) and thermo-
gravimetric analysis (TGA) were used to study their thermal
properties. The chain length of branches greatly affected the
thermal properties of polymers. After hydrogenation, the
thermal degradation stability of polymers was relatively
improved. V
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KEYWORDS: branches; ethylene/vinyl ester copolymers; hydro-
genation; ROMP
1
6,17
INTRODUCTION Polyethylene (PE) is widely used in our daily
ring-opening metathesis polymerization (ROMP)
clic diene metathesis polymerization (ADMET)
or acy-
1
8– oˆ 20
life as one of the most chemically stable and most important
followed
1
commercial polymers. However, its fully saturated hydrocar-
by hydrogenation. Without any reactive groups in the non-
functionalized PEs, the chemical modifications of inert CAH
bonds generally require harsh conditions. This may also
cause the occurrence of many undesirable side reactions,
such as crosslinking or chain scission, which thus severely
alter the properties of polymers. In addition, the postfunc-
tionalization is often hindered by the poor solubility of PE,
multisteps, and low functionality. The direct copolymeriza-
tion always suffers from a special catalytic system with
good tolerance to polar monomers and the largely different
reactivity between ethylene and polar vinyl monomers.
bon skeleton and the absence of polar functional groups usu-
ally lead to its poor adhesion and incompatibility with other
materials. The introduction of polar functionalities into PE
has a tremendous effect on its properties, and the functional-
ization of PE has been extensively studied for the purpose of
2
– oˆ 10
expanding its application fields.
Based on their different
structures, the functionalized PEs mainly include the follow-
ing categories: (a) randomly functionalized copolymers with
either branched or linear structures, (b) end-functionalized
2
– oˆ 10
polymers, (c) block copolymers, (d) graft copolymers.
Due to the random distribution of monomers along the back-
bone, randomly functionalized PEs exhibit completely differ-
ent properties, depending on the different type and amount
of functional groups or different microstructures. The func-
tionalized PEs with linear structures are very interesting
because they can be regarded as a functionalized form of
The preparation of linear functionalized polyolefins by ROMP
of functionalized cyclooctenes and subsequent hydrogenation
1
6– oˆ 21
is of particular interest.
Although the presence of func-
tional groups in cyclooctenes may slow down the polymeri-
2
2– oˆ 25
zation rate in some extent,
the field is rapidly growing
because of the breakthrough of more efficient and tolerant
2
,10
26,27
high-density polyethylene (HDPE).
In general, the random
catalysts.
In this way, the functionalized polyolefins bear-
PE copolymers could be achieved in a variety of ways, such
ing various functional groups in a precise sequence distribu-
3
,11
as postfunctionalization of preformed PE,
direct copoly-
tion have been prepared, theoretically containing 25 mol %
1
1– oˆ 15
16,17,25
merization of ethylene with polar vinyl monomers,
and
of polar vinyl monomers.
For example, the linear VAE
V
C
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copolymers of vinyl acetate/ethylene have been achieved by
the combination of ROMP of acetoxy-substituted at the 3-
or 5-position of cyclooctene using Grubbs catalysts and
to use. Tetrahydrofuran (THF) and dichloromethane were
purified by passing through solvent purification systems
(MB-SPS, MBRAUN). Grubbs second-generation catalyst {G2:
[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro
(phenylmethylene)(tricyclohexylphosphine)ruthenium(II)} and
Grubbs third-generation catalyst {G3: dichloro[1,3-bis(2,4,6-
trimethylphenyl)-2-imidazolidinylidene]-(benzylidene)bis(3-
bromopyridine)ruthenium(II)} were purchased from Shanghai
Coachchem and used directly. Cyclooctadiene monoepoxide and
2
8– oˆ 32
hydrogenation.
The 3-acetoxycyclooctene (3AcCOE)
with a sufficiently bulky functional group afforded regio-
regular and isotactic VAE copolymers, whereas the VAE ana-
logues from 5-acetoxycyclooctene (5AcCOE) were regio-
irregular and atactic.
Recently, the interest in synthesizing and utilizing biomass-
derived polymers is growing significantly, and fatty acid-
derived monomers have been broadly used in the synthesis of
2
8,43
cyclooct-4-enol were prepared according to the literature.
Synthesis of Monomers (M1–M4)
Cyclooct-4-enyl Hexanoate (M1)
3
3–
renewable materials using various polymerization methods.
oˆ 42
In this study, a series of 5-substituted fatty acid-derived
cyclooctenes and their corresponding polymers via ROMP with
Grubbs second-generation catalyst (G2) were synthesized. The
resulting polymers were converted to the hydrogenated poly-
mers by chemical hydrogenation, which represent a class of
precision ethylene/vinyl ester copolymers with pendent linear
branches on precisely every eighth backbone carbon. The
Monomer M1 was prepared via the esterification reaction
between cyclooct-4-enol and n-hexanoic acid according to
the literature method as a clear liquid in 98% yield.
4
4
1
H NMR (400 MHz, CDCl ), d (ppm): 5.71–5.57 (m, 2 H,
3
ACH@), 4.85–4.79 (m, 1 H, ACHOA), 2.36–2.31 (m, 1 H,
ACH CH@), 2.24 (t, J 5 7.6 Hz, 2 H, ACH C(O)A), 2.18–2.13
(m, 2 H, ACH CH C(O)A), 2.11–2.03 (m, 1 H, ACH CH@),
1.90–1.79 (m, 2 H, ACH CH@), 1.71–1.54 (brm, 6 H, ACH
in cyclooctene), 1.33–1.25 (m, 4 H, ACH A in side chain),
.88 (t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
2
2
1
13
structures of polymers were characterized by FTIR, H and
C
2
2
2
NMR spectra, and elemental analysis and the thermal proper-
ties were investigated by DSC and TGA.
2
A
2
2
1
3
0
3
EXPERIMENTAL
(ppm): 173.25 (C@O), 129.73 (ACH@), 129.58 (ACH@),
5.30 (ACHOA), 34.67, 33.73, 33.59, 31.27, 27.98, 25.50,
4.78, 24.70, and 22.29 (ACH A), 13.88 (ACH ). ELEM. ANAL.
7
2
Methods and Materials
The molecular weight and molecular weight distribution of
polymers were measured by gel permeation chromatography
2
3
calcd (%) for C H O (224.34): C 74.95, H 10.78; found: C
1
4 24 2
75.02, H 10.48.
(
GPC) using Waters 2414 series system in THF at 25 8C cali-
brated with polystyrene standards. FTIR spectra were
recorded on a Perkin-Elmer FTIR 2000 spectrometer by
Cyclooct-4-enyl Octanoate (M2)
Cyclooct-4-enol (4.74 g, 36.60 mmol) was combined with 1.2
equiv. of n-octanoic acid (6.33 g, 43.92 mmol), dicyclohexylcar-
boimide (DCC, 9.30 g, 45.07 mmol), and dimethylaminopyri-
dine (DMAP, 0.56 g, 4.58 mmol) in 100 mL of dichloromethane
in a 250-mL round-bottom flask. The reaction mixture was
stirred at ambient temperature for 24 h. The solvent was
removed by rotate evaporation under reduced pressure, and
the residual crude product was purified by column chromatog-
raphy (silica, petroleum ether/ethyl acetate 3:1). The desired
product was obtained as a clear liquid in 99% yield (9.20 g).
1
13
using liquid films. The H and
recorded on a Bruker DMX-400 instrument in CDCl
C NMR spectra were
with
3
TMS as the internal standard at room temperature. Thermog-
ravimetric analysis (TGA) was carried out in nitrogen atmo-
sphere on a TA Q500 TGA analyzer. The differential scanning
calorimetry (DSC) analysis was recorded on a TA Q200 ther-
mal analyzer under N2 atmosphere. The samples were first
cooled from ambient temperature to 2100 8C at 50 8C/min
and then heated to 120 8C at 10 8C/min to remove the ther-
mal history. After isotherm at 120 8C for 3 min, the samples
were subsequently cooled to 2100 8C at 10 8C/min and
reheated to 120 8C at 10 8C/min.
1
H NMR (400 MHz, CDCl ), d (ppm): 5.72–5.58 (m, 2 H,
3
ACH@), 4.85–4.80 (m, 1 H, ACHOA), 2.37–2.28 (m, 1 H,
ACH CH@), 2.24 (t, J 5 7.6 Hz, 2 H, ACH C(O)A), 2.19–2.14
2
2
All the chemical reagents were obtained commercially and used
without further purification unless otherwise stated, including
(
m, 2 H, ACH CH C(O)A), 2.12–2.05 (m, 1 H, ACH CH@),
2 2 2
1
.90–1.80 (m, 2 H, ACH CH@), 1.71–1.54 (brm, 6 H, ACH A
2
2
1
,5-cyclooctadiene (COD, 99.5%), LiAlH (1 mol/L solution in
4
in cyclooctene), 1.31–1.27 (m, 8 H, ACH A in side chain),
2
THF), and p-toluenesulfonyl hydrazide (TSH, 98%) from J&K
Scientific, 3-chloroperbenzoic acid (mCPBA, 75%), dicyclohexyl-
carboimide (DCC, 99%), dimethylaminopyridine (DMAP, 99%),
n-hexanoic acid (AR), and n-octanoic acid (AR) from Aladdin
chemistry, lauric acid (AR), palmitic acid (AR), chloroform (AR),
petroleum ether (AR), ethyl acetate (AR), and diethyl ether (AR)
from Sinopharm Chemical Reagent. Tri-n-propylamine (TPA,
13
0
.87 (t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
3
(
7
2
(
ppm): 172.94 (C@O), 129.48 (ACH@), 129.36 (ACH@),
5.08 (ACHOA), 34.46, 33.56, 33.39, 31.47, 28.89, 28.75,
5.33, 24.83, 24.61, 22.39, and 22.11 (ACH A), 13.81
ACH ). ELEM. ANAL. calcd (%) for C H O (252.40): C
2
3
16 28 2
76.14, H 11.18; found: C 76.15, H 10.95.
99%, Aladdin chemistry) was purified by CaH2 and distilled
Cyclooct-4-enyl Dodecanoate (M3)
under vacuum at 65–70 8C. o-Xylene (98%, Aladdin Chemistry)
was immersed with activated 4Å molecular sieves for 24 h prior
Monomer M3 was synthesized by using a similar procedure as
described for the preparation of M2 starting with cyclooct-4-enol
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and lauric acid. The desired product was collected as a clear
liquid in 99% yield.
4 H, ACH CH@), 1.64–1.47 (m, 6 H, ACH A in main chain),
2
2
1.34–1.24 (m, 6 H, ACH A in side chain), 0.88 (t, J 5 6.8 Hz,
2
1
3
3
H, ACH3). C NMR (100 MHz, CDCl ), d (ppm): 173.53
3
1
H NMR (400 MHz, CDCl ), d (ppm): 5.71–5.57 (m, 2 H,
3
(C@O), 130.23 (ACH@), 129.68 (ACH@), 73.35 (ACHOA),
ACH@), 4.85–4.79 (m, 1 H, ACHOA), 2.36–2.28 (m, 1 H,
ACH CH@), 2.23 (t, J 5 7.6 Hz, 2 H, ACH C(O)A), 2.18–2.13
34.59, 34.02, 33.64, 32.37, 31.31, 28.41, 25.16, 24.78, and
2
2
2
2.30 (ACH A), 13.91 (ACH ). ELEM. ANAL. calcd (%) for
2
3
(
m, 2 H, ACH CH C(O)A), 2.12–2.03 (m, 1 H, ACH CH@),
2
2
2
(
C H O ) : C 74.95, H 10.78; found: C 74.34, H 10.89.
14 24 2 n
1
.90–1.80 (m, 2 H, ACH
2
2
CH@), 1.72–1.54 (brm, 6 H, ACH A
1
in cyclooctene), 1.30–1.24 (m, 16 H, ACH A in side chain),
Poly(cyclooct-4-enyl octanoate) (P2): H NMR (400 MHz,
2
1
3
0
.87 (t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
CDCl ), d (ppm): 5.37–5.32 (m, 2 H, ACH@), 4.88–4.85 (m,
3
3
(
7
2
(
(
ppm): 173.08 (C@O), 129.66 (ACH@), 129.53 (ACH@),
5.19 (ACHOA), 34.65, 33.71, 33.55, 31.84, 29.53, 29.39,
9.27, 29.21, 29.07, 25.47, 24.98, 24.75, 22.62, and 22.26
ACH A), 14.03 (ACH ). ELEM. ANAL. calcd (%) for C20
308.51): C 77.87, H 11.76; found: C 77.20, H 11.94.
1 H, ACHOA), 2.27 (t, J 5 7.4 Hz, 2 H, ACH C(O)A), 2.00–
2
1
.96 (m, 4 H, ACH CH@), 1.63–1.47 (m, 6 H, ACH A in
2
2
main chain), 1.35–1.27 (m, 10 H, ACH A in side chain), 0.87
2
1
3
2
3
36 2
H O
(
t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
3
(
ppm): 173.57 (C@O), 130.25 (ACH@), 129.69 (ACH@),
7
3.37 (ACHOA), 34.65, 34.05, 33.68, 32.41, 31.67, 29.12,
Cyclooct-4-enyl Palmitate (M4)
28.93, 28.43, 25.20, 25.12, and 22.58 (ACH A), 14.06
2
Monomer M4 was synthesized by using a similar procedure
as described for the preparation of M2 starting with
cyclooct-4-enol and palmitic acid. The desired product was
collected as a clear liquid in 98% yield.
(ACH ). ELEM. ANAL. calcd (%) for (C H O ) : C 76.14, H
3
16 28 2 n
11.18; found: C 76.20, H 10.98.
1
Poly(cyclooct-4-enyl dodecanoate) (P3): H NMR (400 MHz,
CDCl ), d (ppm): 5.37–5.32 (m, 2 H, ACH@), 4.88–4.85 (m, 1 H,
ACHOA), 2.26 (t, J 5 7.6 Hz, 2 H, ACH C(O)A), 2.00–1.95 (m,
1
3
H NMR (400 MHz, CDCl ), d (ppm): 5.71–5.57 (m, 2 H,
3
2
ACH@), 4.84–4.79 (m, 1 H, ACHOA), 2.35–2.27 (m, 1 H,
ACH CH@), 2.23 (t, J 5 7.6 Hz, 2 H, ACH C(O)A), 2.18–2.12
4
1
3
H, ACH CH@), 1.67–1.49 (m, 6 H, ACH A in main chain),
2
2
2
2
.34–1.25 (m, 18 H, ACH A in side chain), 0.87 (t, J 5 6.8 Hz,
2
(
m, 2 H, ACH CH C(O)A), 2.11–2.02 (m, 1 H, ACH CH@),
2
2
2
13
3 3
H, ACH ). C NMR (100 MHz, CDCl ), d (ppm): 173.53
1
.90–1.79 (m, 2 H, ACH
2
2
CH@), 1.71–1.53 (brm, 6 H, ACH A
(
C@O), 130.24 (ACH@), 129.69 (ACH@), 73.36 (ACHOA),
34.64, 34.05, 33.69, 32.41, 31.89, 29.59, 29.48, 29.32, 29.28,
9.18, 28.44, 25.22, 25.12, and 22.67 (ACH A), 14.10 (ACH ).
in cyclooctene), 1.30–1.24 (m, 24 H, ACH A in side chain),
2
1
3
0
.86 (t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
3
2
2
3
(
ppm): 173.07 (C@O), 129.66 (ACH@), 129.52 (ACH@),
5.19 (ACHOA), 34.64, 33.71, 33.56, 31.87, 29.63, 29.60,
9.59, 29.54, 29.41, 29.22, 29.08, 25.48, 24.99, 24.75, 22.63,
and 22.27 (ACH A), 14.04 (ACH ). ELEM. ANAL. calcd (%) for
ELEM. ANAL. calcd (%) for (C H O ) : C 77.87, H 11.76; found:
C 77.57, H 11.85.
2
0 36 2 n
7
2
2
3
1
Poly(cyclooct-4-enyl palmitate) (P4): H NMR (400 MHz,
CDCl ), d (ppm): 5.37–5.32 (m, 2 H, ACH@), 4.88–4.85
C H O (364.61): C 79.06, H 12.16; found: C 78.67, H
2
4 44 2
3
11.95.
(m, 1 H, ACHOA), 2.27 (t, J 5 7.4 Hz, 2 H, ACH C(O)A),
2
2
.00–1.95 (m, 4 H, ACH CH@), 1.62–1.49 (m, 6 H, ACH A
2
2
General Procedure of Ring-Opening Metathesis
Polymerization
in main chain), 1.33–1.25 (m, 26 H, ACH A in side chain),
0
2
1
3
.87 (t, J 5 6.8 Hz, 3 H, ACH3). C NMR (100 MHz, CDCl ), d
A typical procedure of ring-opening metathesis polymerization
was as follows: To a three-necked round-bottom flask with a
magnetic stir bar which was predried under vacuum, the
monomer cyclooct-4-enyl hexanoate (M1, 1.24 g, 5.5 mmol)
was added. The flask was purged three times with nitrogen
through the vacuum-nitrogen system and then placed into a
water bath set at 30 8C. An aliquot of a solution containing
Grubbs second-generation catalyst (G2) (9.3 mg, 11.0 lmol,
3
(
ppm): 173.53 (C@O), 130.24 (ACH@), 129.69 (ACH@),
3.36 (ACHOA), 34.65, 34.07, 33.71, 32.42, 31.91, 29.69,
9.66, 29.62, 29.50, 29.36, 29.30, 29.20, 28.45, 25.21, 25.13,
and 22.68 (ACH A), 14.11 (ACH ). ELEM. ANAL. calcd (%) for
7
2
2
3
(
C24H44O2)n: C 79.06, H 12.16; found: C 78.65, H 11.95.
General Procedure for the Hydrogenation
of Unsaturated Polymers
The sealed flask loaded with the unsaturated polymers
[
M] /[G2] 5 500) in CH Cl was rapidly and completely added
0 2 2
via syringe into the flask. After the reaction solution was
stirred at 30 8C for 30 h, an excess of ethyl vinyl ether was
added and the solution was stirred for another 30 min and was
then poured into a large amount of ethanol to precipitate the
desired polymers. The polymers were collected by filtration,
washed multiple times with ethanol, and dried overnight
under vacuum. The following spectral properties were
observed for each polymer.
(
0.16 g) was purged three times with nitrogen through a nitro-
gen system. The solvent o-xylene was added into the flask to
dissolve the polymers. Upon the complete dissolution of poly-
mers, p-toluenesulfonyl hydrazide (TSH) and tri-n-propyl
amine (TPA) were added and the 2/2/1 molar ratio of TSH/
TPA/C@C double bonds was used in the hydrogenation
reaction. The reaction mixture was refluxed at 135–140 8C for
4
h. The color of reaction solution changed from colorless to
1
Poly(cyclooct-4-enyl hexanoate) (P1): H NMR (400 MHz,
deep orange in the end. Finally, the cooled solution was poured
into cold ethanol to precipitate the product. The hydrogenated
polymers were filtered, washed several times with ethanol,
CDCl ), d (ppm): 5.36–5.31 (m, 2 H, ACH@), 4.87–4.85 (m, 1 H,
3
ACHOA), 2.26 (t, J 5 7.4 Hz, 2 H, ACH C(O)A), 1.99–1.95 (m,
2
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SCHEME 1 Synthesis of monomers and the corresponding polymers via ROMP, followed by hydrogenation. Reagents and condi-
tions: (i) Epoxidation: mCPBA, CHCl , THF, 0 8C !r.t., 12 h; (iii) Esterification: DCC, DMAP,
, 0 8C !r.t., 12 h; (ii) Reduction: LiAlH
CH Cl , r.t., 24 h; (iv) Polymerization: G2 catalyst, CH Cl , 30 h; (v) Hydrogenation: TSH/TPA, o-xylene, 135–140 8C, 4 h.
3
4
2
2
2
2
and dried overnight under vacuum. The following spectral
properties were observed for each polymer.
29.29, 29.18, 25.35, 25.15, and 22.67 (ACH A), 14.10
2
(ACH
). ELEM. ANAL. calcd (%) for (C20H O ) : C 77.36, H
3
38 2 n
1
2.34; found: C 77.59, H 12.18.
1
HP1: H NMR (400 MHz, CDCl ), d (ppm): 4.85 (m, J 5 6.0
3
1
Hz, 1 H, ACHOA), 2.27 (t, J 5 7.4 Hz, 2 H, ACH C(O)A), 1.61
m, J 5 7.4 Hz, 2 H, ACH CH C(O)A), 1.49–1.48 (m, 4 H,
ACH A next to side chain), 1.31–1.24 (m, 14 H, ACH A in
main chain and side chain), 0.89 (t, J 5 6.8 Hz, 3 H, ACH ).
C NMR (100 MHz, CDCl ), d (ppm): 173.66 (C@O), 73.98
ACHOA), 34.65, 34.17, 31.31, 29.48, 25.32, 24.81, and
2.31 (ACH A), 13.91 (ACH ). ELEM. ANAL. calcd (%) for
HP4: H NMR (400 MHz, CDCl
Hz, 1 H, ACHOA), 2.27 (t, J 5 7.8 Hz, 2 H, ACH
(m, J 5 7.4 Hz, 2 H, ACH CH C(O)A), 1.49–1.48 (m, 4 H,
ACH A next to side chain), 1.30–1.25 (m, 34 H, ACH A in
main chain and side chain), 0.88 (t, J 5 6.8 Hz, 3 H, ACH ).
), d (ppm): 173.65 (C@O), 73.98
(ACHOA), 34.70, 34.23, 31.92, 29.69, 29.66, 29.62, 29.55,
29.51, 29.36, 29.30, 29.19, 25.37, 25.16, and 22.68 (ACH A),
4.11 (ACH ). ELEM. ANAL. calcd (%) for (C H O ) : C 78.63,
3
), d (ppm): 4.85 (m, J 5 6.0
2
(
2
C(O)A), 1.61
2
2
2
2
2
2
3
2
2
1
3
3
3
1
3
(
C NMR (100 MHz, CDCl
3
2
2
3
(
C H O ) : C 74.29, H 11.58; found: C 74.02, H 11.75.
2
1
4
26 2 n
1
3
24 46 2 n
1
HP2: H NMR (400 MHz, CDCl ), d (ppm): 4.85 (m, J 5 6.0
3
H 12.65; found: C 78.54, H 12.69.
Hz, 1 H, ACHOA), 2.27 (t, J 5 7.4 Hz, 2 H, ACH C(O)A), 1.61
2
(
m, J 5 7.4 Hz, 2 H, ACH CH C(O)A), 1.49–1.48 (m, 4 H,
2 2
RESULTS AND DISCUSSION
ACH A next to side chain), 1.30–1.24 (m, 18 H, ACH A in
2
2
Synthesis of Monomers M1–M4
The monomers, fatty acid derived cyclooctenes (M1–M4),
were prepared from the starting material 1,5-cyclooctadiene
main chain and side chain), 0.87 (t, J 5 6.8 Hz, 3 H, ACH ).
3
1
3
C NMR (100 MHz, CDCl ), d (ppm): 173.66 (C@O), 73.98
3
(ACHOA), 34.69, 34.19, 31.67, 29.51, 29.11, 28.93, 25.36,
(COD). One of the C@C double bonds in 1,5-cyclooctadiene
2
5.14, and 22.57 (ACH A), 14.05 (ACH ). ELEM. ANAL. calcd
2
3
was first transformed into epoxy group by using 3-
chloroperbenzoic acid (mCPBA) as an epoxidation reagent,
yielding cyclooctadiene monoepoxide, which was then
reduced into cyclooct-4-enol by LiAlH4.
(
%) for (C H O ) : C 75.54, H 11.89; found: C 75.34, H
16 30 2 n
11.92.
1
28,43
HP3: H NMR (400 MHz, CDCl ), d (ppm): 4.85 (m, J 5 6.0
The esterification
3
Hz, 1 H, ACHOA), 2.27 (t, J 5 7.8 Hz, 2 H, ACH C(O)A), 1.61
reaction of cyclooct-4-enol with fatty acids, including n-hexa-
2
4
4
(m, J 5 7.4 Hz, 2 H, ACH
2
CH
2
C(O)A), 1.49–1.48 (m, 4 H,
noic acid, n-octanoic acid, lauric acid and palmitic acid,
generated the corresponding fatty acid derived cyclooctenes
(M1–M4) in the presence of DCC and DMAP (Scheme 1).
The structure and purity of monomers were determined by
ACH A next to side chain), 1.30–1.25 (m, 26 H, ACH A in
2
2
main chain and side chain), 0.88 (t, J 5 6.8 Hz, 3 H, ACH ).
3
1
3
C NMR (100 MHz, CDCl ), d (ppm): 173.65 (C@O), 73.98
3
1
13
(ACHOA), 34.70, 34.22, 31.90, 29.60, 29.54, 29.49, 29.33,
FTIR, H and C NMR spectra, and elemental analysis.
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1
13
FIGURE 1 H NMR (a) and C NMR (b) spectra of M3, P3, and HP3. *Impurity. [Color figure can be viewed at wileyonlinelibrary.
com]
1
In the H NMR spectra of monomers [Fig. 1(a)], the multiple
peaks at 5.71–5.57 ppm corresponded to the protons in the
C@C double bonds of cyclooctenes and the multiple peaks at
bonds had a little different chemical shifts (129.7 and 129.5
ppm) due to the presence of side chain at the 5-position of
cyclooctene. The signal of ACHA carbon atom connected to
the side chain located at 75.2 ppm. The signals of saturated
carbon atoms in the methylene groups appeared in the range
of 35.0–22.0 ppm and the peak of methyl groups located
around 14.0 ppm.
4
.85–4.79 ppm were assigned to the ACHA proton con-
nected to the side chain. The signals of methylene protons
next to the carbonyl group and methyl protons in the side
chain appeared at 2.24 and 0.87 ppm as the triplet peaks,
respectively. Besides, the signals of residual methylene pro-
tons could be also clearly found in the spectra. The C NMR
spectra also confirmed the structure of monomers [Fig.
1
3
Polymerization of Monomers M1–M4
The Grubbs second-generation catalyst (G2) was chosen for
all the polymerization reactions because no large influence
on the polymerization between catalysts G2 and G3 was
1
1
(b)]. The signal of carbonyl-C atom showed up around
73.0 ppm and the two carbon atoms in the C@C double
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a
TABLE 1 The ROMP of Monomers M1–M4 Using Catalyst G2
c
M
n
b
21
c
Entry Monomer [M]
0
/[G2] Yield (%) (kgꢀmol
)
w n
M /M
1
2
3
4
5
6
7
8
9
1
1
1
M1
M1
M1
M2
M2
M2
M3
M3
M3
M4
M4
M4
500
37
58
64
59
65
73
68
73
75
67
76
82
22.8
2.00
1.89
1.94
1.89
1.71
2.34
1.80
1.69
2.03
1.92
2.10
2.05
750
43.7
1000
500
70.2
83.2
750
139.8
138.8
80.6
1000
500
750
116.9
166.5
93.7
1000
500
0
1
2
750
124.3
126.7
1000
a
2 2
Polymerization conditions: G2: 9.3 mg, 11.0 lmol; CH Cl : 15 mL; reac-
1
3
FIGURE 3 The olefinic region of C NMR spectra of polymers
P1–P4. [Color figure can be viewed at wileyonlinelibrary.com]
tion temperature: 30 8C; reaction time: 30 h. Ethyl vinyl ether was used
as the polymerization terminator.
b
Isolated yield.
c
Determined by GPC using polystyrene standards in THF at 25 8C and
monomer concentration. The GPC traces exhibited a unimo-
dal, and the molecular weight distribution ranged from 1.69
to 2.34 (Fig. 2). In addition, the higher isolated yield was
obtained for the monomer with longer side chains.
reported without calibration.
found. The ROMP of monomers was carried out in dichloro-
methane with G2 at 30 8C for 30 h and the results were
summarized in Table 1. In all the cases, the polymerization
reactions were homogeneous and the reaction mixtures
turned to be deep purple during the polymerization. The
polymerization was finally quenched by adding an excess of
ethyl vinyl ether and being stirred for another 30 min. All
the polymers were isolated by precipitation in ethanol as
extremely viscous semisolids. (P4 became wax-like solid
when ambient temperature was below 10 8C.) All the mono-
mers were polymerized under the similar conditions at a
The two overlapping sets of peaks centered at 5.32 and 5.37
1
ppm in the olefinic region of the H NMR spectra were
observed and assigned to the protons in the C@C double
bonds in the main chains of polymers for cis and trans
repeat units, respectively [Fig. 1(a)]. The cis/trans ratio was
calculated to be approximately 20/80, which was close to
3
1
the ratio observed in the poly(5AcCOE). In comparison
with the corresponding monomer, the multiple peaks
assigned to the ACHA proton connected to the side chain
1
molar ratio of [M] /[G2] 5 500, 750, and 1000. For each
appeared with the similar chemical shift in the H NMR spec-
0
monomer, the isolated yield and molecular weight of resulted
polymers increased gradually as the increase in the
tra. The chemical shifts of the methylene protons next to the
C@C double bonds were found at 2.00–1.95 ppm. The triplet
peaks of methylene protons next to the carbonyl group and
methyl protons in the branch ends also showed up at 2.26
and 0.87 ppm, respectively. The chemical shifts of the other
methylene protons were found in the range of 1.67–1.25
ppm.
Homopolymerization of 5-subsituted cyclooctenes have been
reported to generate polymers theoretically containing
25 mol % of polar vinyl monomers, in which polar groups
were separated by either 6 (tail-to-tail, TT), 7 (head-to-tail,
HT), or 8 (head-to-head, HH) methylene units depending on
2
8,29,45
the different regio-addition of monomers.
For each
polymer synthesized in this work, eight resonances were
1
3
observed in the olefinic region of the C NMR spectra
Fig. 3), which was in accordance with the presence of the
(
three possible regio-isomers (HH, HT, and TT) as well as the
concurrence of cis and trans C@C double bonds in the main
chain. These results revealed that the resulted polymers
were completely regio-irregular. The lack of regiospecificity
FIGURE 2 GPC traces of P3 polymers.
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The FTIR spectra confirmed that the C@C double bonds were
hydrogenated with the evidence of disappeared CAH stretch-
ing vibration bands and CAH out-of-plane bending vibration
2
1
at 967 cm
in the double bonds (Fig. 4). In addition, the
21
stretching vibration of carbonyl group kept at 1733 cm
whether for the monomers or corresponding polymers.
1
In the H NMR spectra [Fig. 1(a)], the various peaks related
to the protons in the C@C double bonds at 5.37–5.32 ppm
and in the methylene groups next to the C@C double bonds
at 2.00–1.95 ppm disappeared completely after hydrogena-
tion. The resonances of saturated methylene protons merged
into an intensive peak at 1.28 ppm. The multiple peaks of
the ACHA proton connected to the side chain (4.85 ppm),
the triplet peaks of methylene protons next to the carbonyl
FIGURE 4 FTIR spectra of M3, P3, and HP3. [Color figure can
group (2.27 ppm) and methyl protons in the branch ends
be viewed at wileyonlinelibrary.com]
13
(
0.87 ppm) kept almost unchanged. In the C NMR spectra
[
Fig. 1(b)], all the resonances of C@C carbon atoms entirely
disappeared and turned into methylene carbon atoms, show-
ing up around 30.00 ppm, which also confirmed the com-
plete hydrogenation of unsaturated polymers. The similar
signals of carbonyl-C atom at 173.0 ppm and ACHA carbon
atom connected to the branches at 74.0 ppm also indicated
that the hydrogenation reaction had almost no influence on
the branches. Because all the monomers are racemic, both
unsaturated and saturated polymers obtained are expected
could be ascribed that the substituent at the 5-position of
cyclooctene was probably too far away from the double
bond to affect the catalyst orientation during the propagation
1
3
step. In the C NMR spectra of polymers [Fig. 1(b)], the sig-
nal of carbonyl-C atom kept around 173.0 ppm. The signal of
ACHA carbon atom connected to the side chain shifted a lit-
tle to 73.4 ppm. The signals of the saturated carbon atoms
in the methylene groups appeared in the range of 34.6–22.7
ppm and the peak of methyl group in the branch ends still
located around 14.0 ppm. The characteristic CAH out-
of-plane bending absorptions in the double bonds at 967
1
3
to be atactic. The
C NMR spectra of hydrogenated
polymers HP1–HP4 gave the multiple signals at 74.0 ppm for
the methine carbon atoms, indicating their regio-irregularity
(
Fig. 5). The hydrogenated polymers are the equivalents of a
2
1
series of ethylene/vinyl ester copolymers with pendent linear
branches on precisely every eighth backbone carbon.
(
trans, mainly) and 722 cm (cis) were observed in the IR
spectra of polymers, respectively (Fig. 4).
Thermal Properties
Hydrogenation of the Unsaturated Polymers
Differential scanning calorimetry (DSC) was applied to analyze
the thermal properties of unsaturated and hydrogenated poly-
mers. The DSC curves of polymers were shown in Figure 6, and
the results were summarized in Table 2. Both glass transition
temperature (T ) and melting point (T ) values were deter-
mined on the heating scan and crystallization temperature (Tc)
values were determined on the cooling scan. The results indi-
cated that the chain length of branches had great influence on
the thermal properties of obtained polymers. Both unsaturated
polymers (P1, P2) and hydrogenated polymers (HP1, HP2)
The unsaturated polymers via ROMP could be successfully
saturated by the chemical hydrogenation reaction using p-
toluenesulfonyl hydrazide (TSH) as a hydrogenation regent
1
7,46
(
Scheme 1), as previously reported.
saturated polymers were obtained in high conversion
>99%, Table 2) and the branches were not influenced as
In all the cases, the
g
m
(
indicated by NMR spectroscopy. After hydrogenation, the sat-
urated polymers were still viscous semisolids but a little less
sticky than the corresponding unsaturated precursors.
TABLE 2 Characterization of Hydrogenated Polymers and Their Precursors
c
Hydrogenated Polymers
Unsaturated Precursors
a
b
d
d
m
d
d
d
m
d
Conv. (%)
Yield (%)
T
g
(8C)
T
(8C)
T
c
(8C)
T
g
(8C)
T
(8C)
T
c
(8C)
HP1
HP2
HP3
HP4
>99
>99
>99
>99
53
98
98
73
258.6
262.9
262.5
-
-
-
-
-
P1 (1)
P2 (4)
P3 (7)
P4 (10)
261.4
266.0
256.8
-
-
-
-
-
232.8, 24.9
245.8
23.1
230.6
242.9
7.9
10.6
0.8
a
1
c
Determined by H NMR spectroscopy from the ratio of integral areas
between the remaining and original double bond.
The numbers in brackets are the entries in Table 1.
d
Determined by DSC on the second heating/cooling cycle at 10 8C/min.
b
Isolated yield.
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1
3
FIGURE 5 C NMR spectra of saturated polymers HP1–HP4. [Color figure can be viewed at wileyonlinelibrary.com]
with shorter branches were completely amorphous materials
was in good agreement with other polymers bearing the satu-
3
7– oˆ 39,49
with T values below 255 8C. A slightly decreased T with the
rated fatty acid-derived side chains.
As a result, the Tm
g
g
increase in the chain length of branches was observed and this
tendency was consistent with the other poly(vinyl ester)s con-
values at 230.6 and 10.6 8C were observed for the unsaturated
polymers P3 and P4, respectively. As the chain length of pen-
dant linear branches increased, the crystallization of side
4
7,48
taining fatty acid side chains.
of unsaturated polymers to those of saturated polymers, the
hydrogenation of polymers led to slightly higher T values.
By comparing the T values
g
chains might be enhanced, leading to the higher T values and
m
3
7– oˆ 39,49
g
crystallinity of polymers.
After the saturation of the
However, because of the presence of longer linear alkyl side
chains, the polymers with the branches of 12 or 16 carbon
atoms started to crystallize with the lower Tm values, which
backbone, the Tm values for the saturated polymers HP3 and
HP4 increased slightly, and there were two endothermic peaks
observed for HP3 (–32.8 and 24.9 8C) and a shoulder peak
FIGURE 6 DSC curves of obtained polymers. (a) Unsaturated polymers P1–P4; (b) saturated polymers HP1–HP4. [Color figure can
be viewed at wileyonlinelibrary.com]
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branches were below 255 8C, whereas no significant T was
g
observed for the polymers with longer linear alkyl branches
(P4 and HP4), indicating that the length of branches had
great influence on the thermal properties. The hydrogenated
polymers had relatively better thermal degradation stability
than the unsaturated polymers.
ACKNOWLEDGEMENTS
The work was supported by the Zhejiang Provincial Natural Sci-
ence Foundation (No. LY16B040001) and the National Natural
Science Foundation of China (No. 21536011).
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