In-chain functionalized syndiotactic 1,2-polybutadiene by a Ziegler-Natta iron(III) catalytic system

Article abstract of DOI:10.1039/c9ra06499k

Copolymerization of 1,3-butadiene with four 1-substituted 1,3-diene comonomers bearing amino and alkyoxy groups by a Ziegler-Natta iron(iii) catalytic system to access in-chain functionalized syndiotactic 1,2-polybutadiene is reported herein. The polar co

Full text of DOI:10.1039/c9ra06499k

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In-chain functionalized syndiotactic 1,2-
polybutadiene by a Ziegler–Natta iron(III) catalytic
system†
Cite this: RSC Adv., 2019, 9, 33465
ab
c
c
b
bd
*
Huaqiang Zhang, Rixin Cong, Heng Liu, Feng Wang,
Shanshan Liang,
b
b
*
Yanming Hu and Xuequan Zhang
Copolymerization of 1,3-butadiene with four 1-substituted 1,3-diene comonomers bearing amino and
alkyoxy groups by a Ziegler–Natta iron(III) catalytic system to access in-chain functionalized syndiotactic
1,2-polybutadiene is reported herein. The polar comonomer content can be easily regulated by varying
the comonomer loadings or polymerization conditions, affording functionalized syndiotactic 1,2-
polybutadiene with different amounts of functionalities. The incorporation of a polar comonomer
showed little influence on the 1,2-content and stereoregularity of the resulting polymers, giving a 1,2-
structure as high as ꢀ85% and an rrrr pentad of 81.0%. Significantly improved surface properties of the
polymers was obtained after incorporation of polar comonomer, as revealed from the remarkably
decreased water contact angles.
Received 19th August 2019
Accepted 8th October 2019
DOI: 10.1039/c9ra06499k
rsc.li/rsc-advances
functionalized sPB, i.e. post functionalization of polymer
products and in situ functionalization by statistical copolymer-
Introduction
ization with polar monomers. In the past few years, colossal
advances have been made for the former strategy, due to the
presence of highly active pendent vinyl substituents.16–22 For
instance, Mecking, Ndoni, et al., presented efficient function-
alization of sPB via thiol–ene reaction, through which various
types of functional groups, including ester, L-cysteine, carbox-
ylic acid were successfully introduced;23–25 Linford and Tang
reported hydrosilation and hydrozirconation of 1,2-poly-
butadiene (1,2-PB) by Si–H and Zr–H reagents, and provided
a platform for accessing diversied functional 1,2-PBs.26,27
Despite of the facility and efficiency in these reports, all of them
were built on the sacrice of pendent double bonds, which
might cause irreversible damage to the inherent nature of sPB,
such as crystallinity,28 molecular weights,16 and even causing
cross-linking.28 On the other hand, incorporation of functional
groups through coordination copolymerization strategy not
only has a good control on the regio- and/or stereo-regularities,
but also is able to regulate the comonomer sequence and
content conveniently by varying the feed ratio. Nevertheless, up
to date, no reports on this strategy were involved, perhaps due
to the highly electrophilic nature of the active species, which are
likely to be deactivated in the presence of heteroatom-
containing polar comonomers. Moreover, directly coordina-
tion copolymerization of 1,3-butadiene with traditional polar
monomers, such as methyl methacrylate, vinyl acetate, etc., is
strikingly difficult due to the different mechanisms presented
in diene and monoene polymerization,29 alternative comono-
mers can be inspired from Cui's and Mecking's recent reports,
in which the preparation of in-chain functionalized cis-1,4
Syndiotactic 1,2-polybutadiene (sPB), a promising crystalline
material that bears alternately located vinyl groups on opposite
positions along the polymer main chain,1 was rstly synthesized
by Natta et al.,2 and later successfully industrialized by the Japan
Synthetic Rubber Co. Ltd. (JSR) by using a Co/AlR3/CS2 catalytic
system.3–7 Due to its unique mechanical properties that origi-
nate from the combination of properties of plastic and rubber,
sPB reveals a wide range of applications in the elds of bres,
lms, moulded articles, and recently has been used as synthetic
rubber reinforcing llers.8–12 Despite this, the inherent shortfall
of low surface energy makes sPB display inferior properties with
respect to adhesion, toughness, paintability, miscibility and
rheological properties. Improving the hydrophilicity and
developing functionalized sPB has been the long-term pursuit
for scientists.
Similar to achieving other functionalized polyolen mate-
rials,13–15 two strategies are generally available for accessing
aCollege of Material Science and Engineering, Shenyang University of Chemical
Technology, Shenyang 110142, China
bCAS Key Laboratory of High-Performance Synthetic Rubber and Its Composite
Materials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
5625 Renmin Street, Changchun 130022, P. R. China. E-mail: fengwang@ciac.ac.cn;
xqzhang@ciac.ac.cn
cLanzhou Petrochemical Research Center, Petrochemical Research Institute,
PetroChina, Lanzhou, 730060, China
dSchool of Chemical Engineering, Changchun University of Technology, Changchun,
Jilin, China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra06499k
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polydienes by using a type of new comonomers (Scheme 1).30–34
Alternatively, this unique comonomer, i.e. functional-group-
substituted 1,3-butadiene, can also be polymerized in a 3,4-
manner through a h3-coordinated p-allylic unit,35 and therefore
serves the best candidate for accessing functionalized sPB.
We have been interested in tapping effective Ziegler–Natta
iron(III) catalytic systems to syndiotactically polymerize 1,3-
butadiene,36–39 to circumvent the environmental toxicity and
bad-smelling issues that encountered in the industrialized
Co(II)-based systems. In the present study, we disclose the rst
example of functionalized sPB prepared through copolymeri-
zation strategy, detailed catalytic behaviours of the iron(III)
catalytic system together with various functionalized sPB with
different types and amounts of functionalities were systemati-
cally evaluated.
Synthesis and characterization of polar 1-substituted 1,3-dienes
All reactions were carried out under a nitrogen atmosphere in
ame-dried glassware with magnetic stirring. A general proce-
dure was as follows: allyltriphenylphosphonium bromide (20 g,
52.18 mmol) was reacted with potassium t-butoxide (molar ratio
1 : 1.2, dissolved in THF) in an ice bath for one hour, then 1.0
equivalent of the benzaldehyde derivative (52.18 mmol) was
slowly added over 10 minutes, and the reaction was continued
for 4 hours in room temperature. The reaction was quenched by
addition of 150 mL of saturated aqueous ammonium chloride
and then extracted with 100 mL ethyl acetate for 4 times to get
crude products. The crude products were puried by silica gel
chromatography (eluent: petroleum ether (or hexane) : ethyl
acetate ¼ 50 : 1) to give the target product.
1-(4-Methoxyl)phenyl-1,3-butadiene (a)
Experimental section
General considerations
1
Yield: 7.79 g, 65%. Z : E ¼ 60 : 40. For E isomer: H NMR (400
MHz, CDCl3, ppm): 7.36 (d, 2H, Hph); 6.89 (d, 2H, Hph); 6.68 (m,
1H, –CH); 6.55–6.45 (m, 2H, –CH); 5.35 (d, 1H, –CH2); 5.20 (d,
1H, –CH2); 3.80 (s, 3H, –CH3); for Z isomer: 1H NMR (400 MHz,
CDCl3, ppm): 7.29 (d, 2H, Hph); 6.92 (m, 1H, –CH); 6.89 (d, 2H,
Iron(III) acetylacetonate (Fe(acac)3) and diethyl phosphite (DEP)
were purchased from J&K (Beijing, China) and diluted to
0.06 mol Lꢁ1 solution in toluene. Al(iBu)3 (1.0 mol Lꢁ1 in
toluene) was a commercial product of Akzo Nobel and used as
received. 1,3-Butadiene was supplied by Jinzhou Petrochemical
Corporation in China and puried by passing through four
H
ph); 6.41 (m, 1H, –CH); 6.20 (t, 1H, –CH); 5.29 (d, 1H, –CH2);
5.17 (d, 1H, –CH2); 3.82 (s, 3H, –CH3). 13C NMR (400 MHz,
CDCl3, ppm): 159.38; 158.78; 137.48; 133.44; 132.51; 131.42;
130.33; 130.03; 129.41; 127.70; 118.97; 116.43; 114.10; 113.74;
55.23. EI-MS for C11H12O (m/z): 161.0 (M + H+).
˚
columns packed with activated molecular sieves (4 A) and KOH
prior to use. Toluene and THF were reuxed over sodium/
diphenylketyl under nitrogen and then distilled before use. All
other commercial chemicals were used as received.
1H NMR spectra were recorded on a Varian Unity-400 MHz
1-(4-N,N-Dimethylamino)phenyl-1,3-butadiene (b)
ꢂ
spectrometer at 125 C in C6D4Cl2. IR spectra was recorded on
1
Yield: 7.93 g, 68%. Z : E ¼ 57 : 43. For E isomer: H NMR (400
BRUKE Vertex-70 FIR spectrophotometer. The molecular
weights and molecular weight distributions of the polymers
were estimated by gel permeation chromatography (GPC) on
a PL-GPC 220 high-temperature chromatograph at 150 ꢂC. 1,2,4-
Trichlorobenzene containing 0.05% (w/v) BHT was used as
eluent at a ow rate of 1.0 mL minꢁ1 and the values of Mn and
Mw/Mn were calculated by using polystyrene calibration. The
melting points were estimated on a Q100 DSC (TA Instruments)
MHz, CDCl3, ppm): 7.32 (d, 2H, Hph); 7.00 (m, 1H, –CH); 6.73–
6.60 (m, 2H, Hph); 6.54–6.45 (m, 2H, –CH); 5.34 (d, 1H, –CH2);
5.18 (d, 1H, –CH2); 2.97 (s, 6H, –N(CH3)2); for Z isomer: 1H NMR
(400 MHz, CDCl3, ppm): 7.27 (d, 2H, Hph); 6.65 (m, 1H, –CH);
6.73–6.60 (m, 2H, Hph); 6.38 (m, 1H, –CH); 6.13 (t, 1H, –CH);
5.25 (d, 1H, –CH2); 5.06 (d, 1H, –CH2); 2.97 (s, 6H, –N(CH3)2). 13
NMR (400 MHz, CDCl3, ppm): 149.97; 149.45; 137.78; 133.79;
130.54; 130.03; 127.64; 127.44; 125.74; 125.48; 117.77; 114.87;
112.29; 111.99; 40.30. EI-MS for C12H15N (m/z): 174.1 (M + H+).
C
under nitrogen atmosphere. The ꢁs1amples were heated and
ꢂ
cooled down at a rate of 10 C min
.
1-(4-Propoxyl)phenyl-1,3-butadiene (c)
1
Yield: 4.47 g, 46%. Z : E ¼ 83 : 17. For E isomer: H NMR (400
MHz, CDCl3, ppm): 7.34 (d, 2H, Hph); 6.89 (d, 2H, Hph); 6.68 (m,
1H, –CH); 6.53 (t, 1H, –CH); 6.49 (t, 1H, –CH); 5.37 (d, 1H, –CH2);
5.21 (d, 1H, –CH2); 3.92 (s, 2H, –O–CH2–); 1.75 (m, 2H, –CH2–);
1.05 (t, 3H, –CH3); for Z isomer: 1H NMR (400 MHz, CDCl3,
ppm): 7.29 (d, 2H, Hph); 6.92 (m, 1H, –CH); 6.89 (d, 2H, Hph);
6.41 (d, 1H, –CH); 6.21 (t, 1H, –CH); 5.30 (d, 1H, –CH2); 5.12 (d,
1H, –CH2); 3.95 (s, 2H, –O–CH2–); 1.75 (m, 2H, –CH2–); 1.05 (t,
3H, –CH3). 13C NMR (400 MHz, CDCl3, ppm): 158.76; 158.15;
137.29; 133.23; 132.35; 130.11; 129.90; 129.69; 129.07; 127.46;
127.36; 118.67; 116.11; 114.48; 114.12; 69.17; 22.47; 10.40. EI-
MS for C13H16O (m/z): 188.1 (M+).
Scheme 1 Polymerization of functional-group-substituted 1,3-buta-
diene (1-substiuted 1,3-diene was taken as an example).
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1-(2-Methoxyl)phenyl-1,3-butadiene (d)
Results and discussion
1
Yield: 3.68 g, 44%. Z : E ¼ 80 : 20. For E isomer: H NMR (400
MHz, CDCl3, ppm): 7.49 (d, 1H, –CH); 7.33–6.74 (m, 4H, Hph);
6.61–6.29 (m, 2H, –CH); 5.38–5.29 (m, 1H, –CH2); 5.19–5.13 (m,
The 1-substituted 1,3-diene comonomers bearing different
types of functionalities, including 1-(4-methoxyl)phenyl-1,3-
butadiene (a), 1-(4-N,N-dimethylamino)phenyl-1,3-butadiene
(b), 1-(4-propoxyl)phenyl-1,3-butadiene (c), 1-(2-methoxyl)
phenyl-1,3-butadiene (d), were prepared by Wittig reaction
between allyltriphenylphosphonium bromide and substituted
benzaldehydes (Scheme 2). Further purication by ash column
chromatography afforded the targeted compounds a–d in high
yields (for detailed procedures and NMR spectra cf. Experi-
1
1H, –CH2); 3.86 (d, 3H, –O–CH3); for Z isomer: H NMR (400
MHz, CDCl3, ppm): 6.95 (d, 1H, –CH); 7.33–6.74 (m, 4H, Hph);
6.61–6.29 (m, 2H, –CH); 5.38–5.29 (m, 1H, –CH2); 5.19–5.13 (m,
1H, –CH2); 3.84 (d, 3H, –O–CH3). 13C NMR (400 MHz, CDCl3,
ppm): 156.97; 156.68; 137.84; 133.44; 130.48; 130.03; 128.47;
127.55; 126.36; 126.10; 120.57; 119.89; 118.76; 116.79; 110.75;
110.28; 55.25. EI-MS for C11H12O (m/z): 161.0 (M + H+).
1
mental section and ESI†). As evidenced from H NMR spectra,
two isomers were obtained for each of the comonomer, with E/Z
ratios of 40/60, 43/57, 17/83, and 20/80 for a–d, respectively.
Copolymerizations of 1,3-butadiene with comonomers a–
d were carried out by using syndiotactically 1,2-selective cata-
lytic system, Fe(acac)3/Al(iBu)3/phosphorous compound. To
optimize the polymerization conditions, the inuences of the
types and/or amounts of phosphorous donors and cocatalysts
Copolymerization procedure of 1,3-butadiene and 1-substituted
1,3-dienes
All the manipulations were performed under an atmosphere of
dry nitrogen. 1,3-Butadiene in toluene (1.85 mol Lꢁ1) and
quantitative 1-substituted 1,3-dienes were placed in an oxygen-
and moisture-free ampule capped with a rubber septum. Then,
Fe(acac)3, DEP, and Al(iBu)3 at designed ratios were injected
sequentially. The polymerization was kept at 50 ꢂC for 4 h, then
terminated by adding 2.0 mL of acidied ethanol containing
1.0 wt% 2,6-di-tert-butyl-4-methylphenol (BHT) as stabilizer.
The resulting products were repeatedly washed with ethanol
were
studied
with
1-(4-N,N-dimethylamino)phenyl-1,3-
butadiene (b) as a comonomer. As the results shown in Table
1, in the presence of 10 mol% polar comonomer b, the poly-
merization proceeded smoothly, affording copolymers from
mediate to high yields, and the catalytic activity and the prop-
erties of the resulting polymers were found to be highly
dependent on the cocatalysts and phosphorous donors. When
the polymerizations were undertaken at smaller cocatalyst/Fe
ratios (Al/Fe < 15), only a small amount of copolymers were
isolated, perhaps due to the insufficiency of cocatalyst to acti-
vate the active species or due to the poison of catalytic active
species by dimethylamino functionality in comonomer b. These
speculations can also be shed light from increment of como-
nomer contents in the resultant copolymers with an increasing
Al/Fe ratio, in which Lewis acidic aluminum cocatalyst would
bond with dimethylamino group and thus hinder it from
decomposing iron(III) active centres. Moreover, polymerization
ꢂ
and dried under vacuum at 40 C to constant weight.
Scheme 2 Copolymerization of 1,3-butdiene with 1-substituted 1,3-
dienes a–d.
Table 1 Copolymerization of 1,3-butadiene with b under different conditionsa
Microstructure
of PBd
Comon. content
Pb
P/Fe
Al/Fe
Yield (%)
Mn ꢃ 10ꢁ3c
PDIc
in polymerd (%)
1,2-
Trans-1,4-
Xce (%)
f
Tm (ꢂC)
Run
1
2
3
4
5
6
7
8
9
10
DEP
DEP
DEP
DEP
DEP
DEP
DEP
DBP
TBP
TPP
3
3
3
3
1
5
10
3
3
3
5
<5%
22
14
54
65
90
<5%
78
<5%
28
—
9.3
6.4
40.2
32.5
4.1
—
—
—
—
—
—
—
14.74
23.71
—
—
16.19
—
—
—
—
157
157
—
—
158
—
10
15
30
30
30
30
30
30
30
2.32
2.67
3.19
2.29
2.90
2.45
1.96
2.37
2.06
3.14
4.00
4.51
2.89
6.69
6.32
2.48
1.32
1.02
64.94
59.52
75.19
81.30
53.76
61.35
84.75
33.33
77.52
35.06
40.48
24.81
18.7
46.24
38.65
15.25
66.67
22.48
6.4
50.5
30.3
70.2
12.66
167
a
Polymerization conditions: solvent, toluene; polymerization time, 4 h; T: 50 ꢂC; 1,3-butadiene, 1.85 mol Lꢁ1; [M]/[Fe] ¼ 1000; comonomer b,
b
c
1.665 mmol (Bd/b ¼ 9/1). DEP: diethyl phosphite; DBP: dibutyl phosphite; TBP: tributyl phosphite; TPP: triphenyl phosphite. Determined by
d
1
e
GPC in trichlorobenzene vs. polystyrene standards. Determined by H NMR analysis.36 Estimated by the formula of DH/DH0, DH was
calculated by DSC and DH0 referred to standard enthalpy of 1,2-polybutadiene with 100% crystallinity, equal to 60.7 J gꢁ1
.
Determined by DSC
f
at heat rate of 10 ꢂC minꢁ1
.
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Table 2 Copolymerization of 1,3-butadiene with different polar 1-substituted 1,3-diene derivativesa
Microstructure
of PBd
Comon. content
in polymerd (%)
Comon./Bdb
Yield (%)
Mn ꢃ 10ꢁ3
PDIc
1,2-
Trans-1,4-
Xce (%)
c
f
Tm (ꢂC)
Run
Comon.
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
—
a
a
a
a
0/100
2/98
5/95
10/90
20/80
30/70
2/98
93
90
83
75
61
47
82
66
54
Oligomer
77
66
47
79
66
48
22.8
37.3
38.1
41.0
45.0
62.7
75.6
55.2
40.2
—
30.6
72.2
67.1
95.6
176.4
102.9
2.22
1.79
3.93
3.69
2.97
2.26
1.78
5.62
3.19
—
2.26
2.57
2.41
2.49
2.08
2.16
0
85.47
84.71
80.65
80.00
74.92
72.46
84.03
80.65
75.19
—
80.65
78.13
75.76
81.30
78.74
77.52
14.53
15.29
19.35
20.00
25.08
27.54
15.97
19.35
24.81
—
19.35
21.87
24.24
18.70
21.26
22.48
42.75
35.25
28.19
12.14
9.41
165
167
157
154
147
140
158
158
157
—
163
161
159
163
156
152
1.63
3.63
7.40
8.88
17.18
0.83
1.84
4.51
—
1.59
3.03
5.71
2.12
4.00
6.29
a
6.40
b
b
b
b
c
c
c
d
d
d
30.97
24.18
14.74
—
31.83
30.61
21.37
30.64
23.94
13.99
5/95
10/90
20/80
5/95
10/90
20/80
5/95
10/90
20/80
a
Polymerization conditions: solvent, toluene; polymerization time, 4 h; T: 50 ꢂC; 1,3-butadiene, 1.85 mol Lꢁ1; [M]/[Fe]/[Al]/[P] ¼ 1000/1/30/3.
b
c
d
1
e
Molar ratio. Determined by GPC in trichlorobenzene vs. polystyrene standards. Determined by H NMR analysis.36 Estimated by the
formula of DH/DH0, DH was calculated by DSC and DH0 referred to standard enthalpy of 1,2-polybutadiene with 100% crystallinity, equal to
f
60.7 J gꢁ1
. .
Determined by DSC at heat rate of 10 ꢂC minꢁ1
at Al/Fe ratio lower than 15 gave amorphous rubber-like 1,2-PB, comonomers a–d were added into the system, the isolated
whereas crystalline syndiotactic sPB was obtained when higher copolymer yields dropped signicantly from 93% for 1,3-buta-
Al/Fe is employed. This result agrees with our previous research diene homopolymerization to 83%, 66%, 77%, and 79% for
on Fe(III)-mediated 1,3-butadiene homopolymerization.40
copolymerizations with a, b, c, and d, respectively. Further
External phosphorous donors also signicantly inuenced increasing the comonomer/Bd ratio led to gradual reduction in
the copolymerization performances. Increasing the P/Fe ratio the polymer yields. For instance, the presence of 30% como-
from 1 to 10 rst led to the formation of sPB and then produced nomer a gave the polymer yield almost half of that in the 1,3-
amorphous 1,2-PB rubber, this is consistent with our previous butadiene homopolymerization (46.5% vs. 92.9%); and the
conclusion that higher P/Fe molar ratio favours the formation of presence of 20% b poisoned the active species signicantly, and
amorphous 1,2-polybutadiene.41 Although the best catalytic only oligomers, rather than copolymers, were produced even-
activity was observed when P/Fe ¼ 5 in the present study, sPB tually. The decrement of polymer yield in the copolymerizations
can only be formed when P/Fe ¼ 1 or 3, therefore, P/Fe ¼ 3 was can be explained by the formation of relatively stable interme-
applied in the following study. Moreover, it was observed that diates through coordination of heteroatoms to iron(III) center,
the molecular weights of the resultant amorphous 1,2-PBs were which retards subsequent insertion reaction. In spite of these
much lower than that of crystalline sPB, which might be due to results, to our knowledge, the synthesis of polar group-
the over-coordination of DEP slowed down coordination of 1,3-
butadiene monomer to the vacant site of active centre and thus
reduced chain propagation rate. Different types of phosphorous
donors were also investigated, and dibutyl phosphite (DBP) was
found to give the highest polymer yield (78%), and simulta-
neously affording sPB with high 1,2-contents. Whereas tributyl
phosphite (TBP) and triphenyl phosphite (TPP)-based systems
showed much lower catalytic activities under identical condi-
tions; the polymer yields were <5% and 28%, respectively.
Copolymerizations were then expanded to other 1-
substituted 1,3-dienes to evaluate the inuence of different
functionalities on copolymerization behaviour. As the results
summarized in Table 2, the presence of a small amount of polar
comonomer could deactivate the active species obviously, in
spite of the relative lower electrophilicity of late-transition metal
iron(III) center, when comparing to early-transition or lantha-
nide metal counterparts. For instance, when 5% of
Fig. 1 1H NMR spectra of the copolymers obtained from 1,3-buta-
diene and comonomer a.
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functionalized sPB via direct polymerization approach has not
been reported thus far, this is the rst example in this eld.
Regarding the effect of functionality on copolymerization
performances, an order of a > c ꢀ d > b was revealed from the
catalytic activities. The most unreactive comonomer b was
ascribed to the strongest electro-donating ability of dimethyla-
mino group, which displayed high coordination capability with
the electrophilic active species and/or the alkyl aluminum
cocatalyst. Similar reasons can also be explainable for the
inferior reactivity of monomers c, when comparing with a, the
presence of long alkyl group generally imparts them more
pronounced electron-donating ability. Nevertheless, the relative
smaller reactivity of d was ascribed to steric effect, i.e., 2-
substituted phenyl groups brought in a sterically hindered Fig. 3 X-ray spectra of the resultant copolymer products (runs 11, 13,
16).
space, which thus prohibited itself being coordinated to the
metal center.
Incorporation of polar 1-substituted 1,3-diene comonomer
the slight decrease of 1,2-structure didn't affect the stereo-
regularity of the resultant copolymers. As the representative
13C NMR shown in Fig. 2, when 10% comonomer b was incor-
porated into the polymer chain, the syndiotactic rrrr pentad was
maintained as high as 81.0%, which is about same with that of
sPB homopolymers,35 implying that the presence of polar
comonomer displayed subtle inuence on the stereoselectivity
of the iron(III) catalytic active species.
The incorporation of polar 1-substituted 1,3-diene como-
nomer into sPB resulted in, as expected, a decrease in the crys-
tallinity degree Xc and melting temperature Tm of the resulting
copolymers. Fig. 3 shows the WXRD spectra of the resultant
copolymer, the diffraction peaks at 2q ¼ 13.50, 16.17, 21.22, and
23.50ꢂ ascribed to 1,2-syndiotactic PB,42 clearly weakened with an
increasing incorporation amount of comonomer a. Fig. 4 illus-
trates the DSC analysis curves, in which a gradual decrease of Tm
and gradual broadening of the melting transition were observed
when more comonomer was in cooperated.
was clearly observed for all the copolymerization studies. When
comonomer a/Bd ¼ 2/98 in the feed ratio, the resulting copol-
ymer contained ca. 1.63% of comonomers. The increase in the
comonomer feed resulted in the increment of comonomer
content in the resulting polymer. Fig. 1 illustrated the 1H NMR
spectra of the resultant copolymers, in which the resonance
peaks at 3.81 ppm assignable to the methoxyl group gradually
increased if more a was incorporated into the copolymer.
Moreover, the resonance peaks of phenyl protons at 6.92 ppm,
can also be clearly observed. For other comonomers b–d,
a monotonous increasing of incorporation content could also
be witnessed if more comonomer feed ratio was applied.
Increasing the amount of comonomer a from 2% to 30% led
to slight decrement of 1,2-content in the resultant copolymers
from 84.71% to 72.46%, while the rest microstructure was kept
as trans-1,4- moiety. Similar results were also observed for other
comonomer b, c, and d. While the increase in the comonomer
feed led to a decrement in the catalytic activity (vide supra) and
1,2 selectivity, the catalytic system still exhibited syndio 1,2-
selectivity, affording in-chain functionalized sPBs. As the
tendency revealed from Fig. 1, the resonance peaks, that
assigned to the vinyl protons, at 5.75, 5.14 ppm revealed a clear
decrement. Similar conclusion can also be made for other
comonomers, as revealed from Fig. S9–S11.† It is of note that,
In order to clearly elucidate of the improved surface property
upon incorporation of polar monomer, static water contact
angles of the resultant copolymers was tested. The results
demonstrated that the static water contact angle of the copol-
ymers decreased from 115.1ꢂ (run 11) to 104.2ꢂ (run 14) with an
addition of 10 mol% a. Analogous results were observed for
Fig. 2 13C NMR spectrum (olefinic region) of the resultant copolymers
(run 19).
Fig. 4 DSC curves of the resultant copolymer products (runs 11–16).
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3 H. Ashitaka, H. Ishikawa, H. Ueno and A. Nagasaka, J. Polym.
Sci., Polym. Chem. Ed., 1983, 21, 1853–1860.
4 M. Ichikawa, Y. Takeuchi, A. Kogure and H. Kurita, US Pat.,
3498963A, 1970.
5 K. Makino, K. Komatsu, Y. Takeuchi and M. Endo, US Pat.,
4182813A, 1980.
6 S. Luo, US Pat., 6331594, 2001.
7 S. Luo, US Pat., 6528588, 2003.
8 H. Ashitaka, Y. Kusuki, S. Yamamoto, Y. Ogata and
A. Nagasaka, J. Appl. Polym. Sci., 1984, 29, 2763–2776.
9 X. Hao and X. Zhang, Mater. Lett., 2007, 61, 1319–1322.
10 M. Hitrik, V. Gutkin, O. Lev and D. Mandler, Langmuir, 2011,
27, 11889–11898.
11 W. Pan, H. Chen, J. Mu, W. Li, F. Jiang, G. Weng, Y. Hu,
D. Gong and X. Zhang, Polymer, 2017, 111, 20–26.
12 Y. Takahashi, X. Liang and K. Nakajima, J. Appl. Polym. Sci.,
2019, 136, 47934.
Fig. 5 Static water contact angle measurements for the resultant
copolymer products (runs 11, 14, 19, 25).
13 T. C. Chung, Prog. Polym. Sci., 2002, 27, 39–85.
14 P. Zinck, F. Bonnet, A. Mortreux and M. Visseaux, Prog.
Polym. Sci., 2009, 34, 369–392.
other comonomer b–d, implying the signicant increased
surface energy therein (Fig. 5).
15 N. M. G. Franssen, J. N. H. Reek and B. de Bruin, Chem. Soc.
Rev., 2013, 42, 5809–5832.
Conclusions
16 B. Marciniec, M. Lewandowski, C. Pietraszuk and
Z. Foltynowicz, Polymer, 1997, 38, 5169–5172.
17 M. I. Abdullin, A. B. Glazyrin, R. N. Asfandiyarov,
V. R. Akhmetova and V. N. Zaboristov, Polym. Sci., Ser. B,
2006, 48, 104–107.
18 M. I. Abdullin, A. B. Glazyrin, R. N. Asfandiyarov and
R. R. Muslukhov, Polym. Sci., Ser. B, 2009, 51, 303–308.
19 A. B. Glazyrin, M. I. Abdullin, R. R. Muslukhov and
V. A. Kraikin, Polym. Sci., Ser. A, 2011, 53, 110–115.
20 A. B. Glazyrin and M. I. Abdullin, Russ. J. Appl. Chem., 2016,
89, 1655–1661.
21 A. B. Glazyrin, M. I. Abdullin, E. R. Atnabaeva,
R. M. Sultanova, V. P. Volodina and V. A. Dokichev, Polym.
Bull., 2019, 76, 3643–3657.
22 F. Guo, K. Jankova, L. Schulte, M. E. Vigild and S. Ndoni,
Langmuir, 2010, 26, 2008–2013.
In-chain functionalized syndiotactic 1,2-polybutadiene via
copolymerization strategy is disclosed in this research. Through
changing copolymerization conditions, the Ziegler–Natta cata-
lytic system, Fe(acac)3/Al(iBu)3/P, was able to efficiently copoly-
merize 1,3-butadiene with 1-substituted 1,3-dienes containing
amino and alkoxy groups to produce functionalized syndiotactic
1,2-polybutadiene. Copolymerization conditions, including
phosphorous donors, cocatalyst, etc., imposed signicant inu-
ence on the copolymerization activities, as well as the properties
of resulting functionalized copolymers. Although slight
decreased 1,2-contents was revealed when increasing the
comonomer content, but the resultant copolymers still exhibited
syndiotactic structure. The incorporation of polar comonomers
greatly improved the energy surface of copolymer products.
˜
23 B. Korthals, M. C. Morant-Minana, M. Schmid and
Conflicts of interest
S. Mecking, Macromolecules, 2010, 43, 8071–8078.
24 A. Berthold, K. Sagar and S. Ndoni, Macromol. Rapid
Commun., 2011, 32, 1259–1263.
There are no conicts to declare.
25 L. Lotti, S. Coiai, F. Ciardelli, M. Galimberti and E. Passaglia,
Macromol. Chem. Phys., 2009, 210, 1471–1483.
26 T. D. Wickard, E. Nelsen, N. Madaan, N. ten Brummelhuis,
C. Diehl, H. Schlaad, R. C. Davis and M. R. Linford,
Langmuir, 2010, 26, 1923–1928.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (No. 21801236), PetroChina Company
Limited (2018B-2707), Joint Funds of the National Natural
Science Foundation of China (U186220053) and Jilin Provincial
27 J. Zheng, F. Liu, Y. C. Lin, Z. J. Zhang, G. C. Zhang, L. Wang,
Y. Liu and T. Tang, Macromolecules, 2012, 45, 1190–1197.
Science
and
Technology
Development
program
˜
28 B. Korthals, M. C. Morant-Minana, M. Schmid and
(20190103122JH).
S. Mecking, Macromolecules, 2010, 43, 8071–8078.
29 The growing active specieses are h3 and s1 coordinated
mode for diene and monoene monomers respectively.
30 C. Yao, N. Liu, S. Long, C. Wu and D. Cui, Polym. Chem.,
2016, 7, 1264–1270.
Notes and references
1 J. E. Mark, Handbook, Polymer Data, Oxford University Press,
New York, 1999.
2 V. G. Natta, Makromol. Chem., 1955, 16, 213–237.
31 S. Long, F. Lin, C. Yao and D. Cui, Macromol. Rapid
Commun., 2017, 38, 1700227.
33470 | RSC Adv., 2019, 9, 33465–33471
This journal is © The Royal Society of Chemistry 2019

View Article Online
Paper
RSC Advances
¨
32 H. Leicht, I. Gottker-Schnetmann and S. Mecking, J. Am. 38 W. Pan, H. Chen, R. Sun, D. Gong, X. Jia, Y. Hu and X. Zhang,
Chem. Soc., 2017, 139, 6823–6826. Ind. Eng. Chem. Res., 2016, 55, 7580–7586.
33 H. Leicht, I. Gottker-Schnetmann and S. Mecking, 39 D. Gong, W. Dong, J. Hu, X. Zhang and L. Jiang, Polymer,
Macromolecules, 2017, 50, 8464–8468. 2009, 50, 2826–2829.
34 H. Leicht, I. Gottker-Schnetmann and S. Mecking, ACS Macro 40 W. Zheng, F. Wang, J. Bi, H. Zhang, C. Zhang, Y. Hu, C. Bai
¨
¨
Lett., 2016, 5, 777–780.
35 C. Yao, H. Xie and D. Cui, RSC Adv., 2015, 5, 93507–93512.
and X. Zhang, J. Polym. Sci., Polym. Chem. Ed., 2015, 53,
1182–1188.
36 D. Gong, W. Dong, Y. Hu, J. Bi, X. Zhang and L. Jiang, 41 J. Lu, Y. Hu, X. Zhang, J. Bi, W. Dong, L. Jiang and B. Huang,
Polymer, 2009, 50, 5980–5986. J. Appl. Polym. Sci., 2006, 100, 4265–4269.
37 D. Gong, W. Pan, T. Zhu, H. Chen, Z. Zhou, F. Jiang, Y. Hu 42 J. Cai, Q. Yu, X. Zhang, J. Lin and L. Jiang, J. Polym. Sci., Part
and X. Zhang, Polymer, 2016, 98, 136–142.
B: Polym. Phys., 2005, 43, 2885–2897.
This journal is © The Royal Society of Chemistry 2019
RSC Adv., 2019, 9, 33465–33471 | 33471