Synthesis and characterization of precisely-defined ethylene-co-aryl ether polymers via ADMET polymerization

Article abstract of DOI:10.1016/j.polymer.2015.03.039

A new family of polyolefins containing various aryl ether units have been designed and synthesized, and their thermal properties were studied. We prepared six acyclic diene monomers di(undec-10-enyloxy)aryl ether by a two-step approach and the corresponding homopolymers and copolymers with 1,9-decadiene by ADMET. Subsequent hydrogenation gave the corresponding ethylene-co-aryl ether polymers. The structures of these polymers were confirmed by ¹H NMR, ¹³C NMR and FT-IR. Additionally, crystallization behaviors and thermal properties were investigated by differential scanning calorimetry (DSC), X-ray diffraction and thermal gravimetric analysis (TGA). The results show that incorporation of these aryl ether units has improved the thermal stability of polymers. And these polymers show a tendency of semicrystallinity to amorphous state with the insertion of more rigid phenyl rings in functional sites of polymers' main chain. Interestingly, DSC analysis reveals that a sequence of melting/crystallization phenomenon occurs in the crystalline saturated homopolymers.

Full text of DOI:10.1016/j.polymer.2015.03.039

Polymer 64 (2015) 76e83
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Synthesis and characterization of precisely-defined ethylene-co-aryl
ether polymers via ADMET polymerization
,
,
,
, b, *
Shaofei Song a b, Weijun Miao a b, Zongbao Wang a b, Dirong Gong a
,
Zhong-Ren Chen a
, b, *
a Department of Polymer Science and Engineering, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China
b Key Laboratory of Specialty Polymers, Grubbs Institute, Ningbo University, Ningbo 315211, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new family of polyolefins containing various aryl ether units have been designed and synthesized, and
their thermal properties were studied. We prepared six acyclic diene monomers di(undec-10-enyloxy)
aryl ether by a two-step approach and the corresponding homopolymers and copolymers with 1,9-
decadiene by ADMET. Subsequent hydrogenation gave the corresponding ethylene-co-aryl ether poly-
mers. The structures of these polymers were confirmed by 1H NMR, 13C NMR and FT-IR. Additionally,
crystallization behaviors and thermal properties were investigated by differential scanning calorimetry
(DSC), X-ray diffraction and thermal gravimetric analysis (TGA). The results show that incorporation of
these aryl ether units has improved the thermal stability of polymers. And these polymers show a
tendency of semicrystallinity to amorphous state with the insertion of more rigid phenyl rings in
functional sites of polymers' main chain. Interestingly, DSC analysis reveals that a sequence of melting/
crystallization phenomenon occurs in the crystalline saturated homopolymers.
Received 5 December 2014
Received in revised form
27 February 2015
Accepted 12 March 2015
Available online 21 March 2015
Keywords:
ADMET
Ethylene-based materials
Poly (aryl ether)
© 2015 Published by Elsevier Ltd.
1. Introduction
ether polymers have been rarely reported. Actually, poly (aryl
ether) is a class of engineering plastics with integrated high per-
The structureeproperty relationship of ethylene-based mate-
rials has attracted increasing attention. The physical and chemical
properties of corresponding ethylene-based polymers can be
widely modulated by manipulating the microstructural parame-
ters, such as the nature, length and placement of the branches
along the backbone. For instance, introduction of non-polar or polar
functionalities via copolymerization or post-functionalization like
alkyl, halogen, cyano, phenyl, hydroxyl, and carboxyl, would endow
polymers with unique properties such as crystallinity, flexibility,
flame retardancy, chemical resistance, impact strength, process-
ability and adhesion [1e8]. Also, some special ethylene-based
functional materials like ionomers [9,10], poly (thienylene vinyl-
ene)s (PTVs) [11], and polymer light emitting diodes (PLEDs) [12,13]
received considerable attention in recent years for their potential
application as electroactive materials. However, ethylene-co-aryl
formance such as good mechanical properties, heat resistance, and
corrosion resistance, thus it has been widely used in aerospace,
electronics, mechanical instruments and other fields [14,15].
Therefore it will be interesting to know if introducing the aryl ether
units into the main chain of polyethylene would bring about
excellent properties from both poly (aryl ether) and polyethylene.
Williamson ether synthesis [16], Claisen rearrangement [17,18]
and Ullmann condensation reaction [19e21] are the general
methods access to small aryl ether molecules and even polymers
with only short ethylene segments incorporated. However, syn-
thesizing ethylene-based polymers with longer ethylene segments
via these methods would require long reaction time, heating and
often suffer from low yields. Typical polymerization strategies for
the preparation of ether incorporated polyolefins could also include
transition-metal-catalyzed coordination-insertion polymerization
and free radical processes, but the oxophilicity of the transition-
metal polymerization catalysts which generally leads to poisoning
by strong s-coordination of the Lewis basic moiety of a polar vinyl
* Corresponding authors. Department of Polymer Science and Engineering, Fac-
ulty of Materials Science and Chemical Engineering, Ningbo University, Ningbo
315211, China.
E-mail addresses: gongdirong@nbu.edu.cn (D. Gong), chenzhongren@nbu.edu.
cn (Z.-R. Chen).
monomer or poor control over branching ratios, and distribution of
the polar functional groups in the polymer chain. Alternatively,
ring-opening metathesis polymerization (ROMP) of functionalized
http://dx.doi.org/10.1016/j.polymer.2015.03.039
0032-3861/© 2015 Published by Elsevier Ltd.

S. Song et al. / Polymer 64 (2015) 76e83
77
cyclooctenes [22e24] or acyclic diene metathesis (ADMET) of
functionalized dienes [25e27] represents potentially ideal
concentration using a 150
m
L injection volume. In the case of uni-
a
versal calibration, retention times were calibrated against narrow
molecular weight polystyrene standards to produce number
average molecular weight (Mn) and weight average molecular
weight (Mw) values. Thermal gravimetric analysis (TGA) was per-
formed using a TA Instruments Q4000 series instruments with
nitrogen purging rate set at 50 mL/min. Measurements were con-
ducted from room temperature to 800 ꢀC. DSC analysis was per-
formed using a DSC equipped with a controlled cooling accessory at
a heating rate of 10 ꢀC/min unless otherwise noted. Transition
temperatures were referenced to indium and freshly distilled n-
octane and transition enthalpies were referenced to indium. The
samples were scanned for multiple cycles to remove recrystalliza-
tion differences between the samples and the results reported were
of the third scan in the cycle. XRD data were obtained on a Bruker
method for the controlled synthesis of functional polyolefins in a
single step, particularly, precisely control the identity and distri-
bution of branches along the backbone of polyethylene, as well as
functional groups incorporated in the main chain, including model
copolymers of ethylene with acrylates [28], styrene [29], vinyl ac-
etate [30], and vinyl halide [31], silicon-containing polymers [32]
and chiral polymers [33] have been unprecedently achieved in
the presence of Schrock' catalyst and Grubbs' series of catalysts.
The bisphenols with two hydroxyphenyl functionalities are
potentially good candidates for constructing aryl ether architecture
in polymer chain. In this research, we have selectively introduced
1,4-benzenediol group, 4,40-biphenol group and other four types of
bisphenol groups as co-monomers to form corresponding
ethylene-co-aryl ether polymers via ADMET. The nomenclature of
polymers is expressed in the following manner: “BP” stands for
polymers containing bisphenols units, the digital or letter following
the “BP” refers to the type of bisphenols units, subsequent “P”
stands for unsaturated polymer, and “HP” refers to hydrogenated
polymer, the final digital stands for serial number. For example,
“BPF-HP4” refers to hydrogenated polyolefin 4 with bisphenol F
(4,40-Dihydroxydiphenylmethane). Additionally, “dd” is added to
the abbreviations for copolymer with 1,9-decadiene, like BPFdd-
HP8. All polymers' chemical structures have been characterized by
FT-IR, 1H and 13C NMR techniques, and their thermal properties,
crystallization behaviors were also systematically investigated by
DSC, TGA and X-ray diffraction.
D8 diffractometer, using the Cu K
induced by a generator operating at 40 kV and 40 mA. Diffraction
patterns were recorded for 2
a
radiation (
l
¼ 0.15417 nm)
q
-values ranging from 5ꢀ to 60ꢀ.
2.3. Synthesis
2.3.1. Synthesis of 11-bromo-undec-1-ene
11-Undecen-1-ol (140 g, 0.82 mol) and CBr4 (300 g, 0.90 mol)
were dissolved in CH2Cl2 (500 mL) in Schlenk flask and triphenyl-
phosphine (237 g, 0.90 mol) was then added dropwise over 15 min
at ꢁ5 ꢀC. The system was stirred at ꢁ5 ꢀC for 2 h, and raised to room
temperature for 12 h. The solution was concentrated and a white
precipitate formed which was removed by filtration. The resultant
solution was fractionally distilled under reduced pressure to get a
purified and colorless liquid product (177 g). Yield: 93%. 1H NMR
2. Experimental
(400 MHz, CDCl3, ppm):
d
¼ 5.83 (ddt, J ¼ 16.9,10.1, 6.7 Hz,1H), 4.98
2.1. Materials
(dd, J ¼ 25.0, 13.6 Hz, 2H), 3.42 (t, J ¼ 6.9 Hz, 2H), 2.06 (q, J ¼ 6.9 Hz,
2H), 1.97e1.75 (m, 2H), 1.65e1.11 (m, 12H). 13C NMR (125 MHz,
Anhydrous 1,2-dichloromethane was obtained using a solvent
purification system (Innovative Technologies). Anhydrous N,N-
Dimethylformamide (DMF) was refluxed over CaH2 and distilled
in presence of molecular sieves. 1,2-Dichlorobenzene was distilled
and degassed prior to use. All the bisphenols were purified by
recrystallization in hexane. Grubbs catalyst bis(tricyclohex-
ylphosphine)- benzylidineruthenium(IV) dichloride was obtained
from Sigma Aldrich. All other chemicals were used as received from
Tokyo Chemical Industry Co., Ltd. ADMET polymerization and hy-
drogenation were performed under nitrogen using standard
Schlenk techniques.
CDCl3, ppm):
28.2.
d
¼ 139.0, 114.1, 33.8, 33.7, 32.9, 29.4, 29.1, 28.9, 28.8,
2.3.2. General procedure for the synthesis of monomers
p-Benzenediol (Hydroquinone, defined as BP1 here) (2.2 g,
20 mmol) and sodium hydroxide (2.4 g, 60 mmol) were dissolved in
120 mL DMF in a 250-mL round bottomed Schlenk flask, then the
mixture was stirred for 30 min, and a solution of 11-bromo-1-
undecene (12 g, 51.5 mmol) in DMF (120 mL) was added drop-
wise over 10 min. The resulting reaction mixture was heated at
70 ꢀC and left stirring for more than 8 h. Subsequently, the reaction
was cooled to RT and quenched with addition of diethyl ether
(100 mL) and water (100 mL). The aqueous phase was extracted
with diethyl ether (300 mL ꢂ 2), and the combined organic frac-
tions were washed with brine and dried over MgSO4 and concen-
trated. The residue was recrystallized from EtOH twice to obtain
2.2. Instrumentation
High temperature 1H NMR (300 MHz) and 13C NMR (75 MHz)
spectra for saturated polymers were recorded on a Varian Associ-
ates Mercury 300 spectrometer, and 1H NMR (400 MHz) and 13C
NMR (100 MHz) spectra for monomers and unsaturated polymers
were recorded on Bruker ARX400 spectrometer. Chemical shifts for
1H and 13C NMR were referenced to residual signals from CDCl3 (1H:
6.1 g BP1-M1. Yield: 74%. 1H NMR (400 MHz, CDCl3, ppm):
d
¼ 6.82
(s, 2H), 5.93e5.70 (ddt, J ¼ 16.9,10.2, 6.7 Hz,1H), 5.23e4.72 (m, 2H),
3.90 (t, J ¼ 6.6 Hz, 2H), 2.05 (q, J ¼ 6.9 Hz, 2H), 1.84e1.64 (m, 2H),
1.58 1.13 (m,13H). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 153.2,139.2,
d
¼ 7.26 ppm and 13C:
d
¼ 77.23 ppm) or toluene-d8 (1H:
d
¼ 7.09,
115.4, 114.1, 68.7, 33.8, 29.5, 29.4, 29.4, 29.4, 29.1, 28.9, 26.1.
7.00, 6.98 and 2.09 ppm and 13C:
d
¼ 137.86, 129.24, 128.33, 125.49
and 20.4 ppm). Thin layer chromatography (TLC) performed on
EMD silica gel coated (250 m thickness) glass plates was used to
2.3.3. General procedure for the synthesis of unsaturated
homopolymers
m
monitor all monomer synthesis. TLC plates were developed to
produce a visible signature by both of ultraviolet light and iodine.
FT-IR spectroscopy was also carried out for monomers, unsaturated
and saturated polymers characterization.
Taking BP1-M1 as example, BP1-M1 (4 g, 9.66 mmol) was
placed in a 25 mL flame dried Schlenk flask under nitrogen. Grubbs'
first generation catalyst (79.5 mg, 1.0 mol %) was added and the
mixture was stirred at 75 ꢀC under high vacuum. The reaction flask
was heated to 90 ꢀC as it became viscous. After 48 h, the reaction
was terminated by 5 mL vinyl ethyl ether. The polymer was
precipitated by acidic methanol, filtered, washed with methanol
and finally dried as a white solid, BP1eP1 (3.6 g). Yield: 91%. 1H
Gel permeation chromatography (GPC) was performed at 150 ꢀC
using two columns (10 microns PD, 7.8 mm ID, 300 mm length)
with HPLC grade 1,2,4-trichlorobenzene as the mobile phase at a
flow rate of 1.0 mL/min. Injections were made at 0.3% w/v sample

78
S. Song et al. / Polymer 64 (2015) 76e83
NMR (300 MHz, Toluene-d8, ppm):
d
¼ 6.83 (s, 4H), 5.65e5.31 (m,
hydride as the base in dry and air free DMF at 40 ꢀCe65 ꢀC.
Subsequent ADMET polymerization with Grubbs' first generation
catalyst were carried out in bulk polymerization, in 1,2-
dichlorobenzene under vacuum for removing ethylene, or in
CH2Cl2 at 45 ꢀC (Scheme 1). Grubbs' first generation was prefer-
entially chosen for linear polymer with perfectly spaced aryl
ether units. Considering hydrogenation catalyzed by Wilkinson's
catalyst consumed long time under harsh condition, exhaustive
hydrogenation by using tripropylamine and TsNHNH2 (4-
methylbenzene-sulfonhydrazide) was applied to all the nine
polymers in p-xylene at 130 ꢀC.
As shown in Scheme 1, we view the 3 as monomer, 4 as repeat
units of unsaturated polymers, and 5 as the repeat unit of the
desired saturated homopolymer. These aryl ether containing ho-
mopolymers could also be viewed as alternative copolymer of
eicosane and aryl ether. From this point of view, it would be
interesting if we would know the effect of sequence distribution
and additional ethylene units on the structureeproperty relation-
ship of ethylene copolymers with aryl ether, therefore we also
synthesized monomers and random copolymers of ethylene with
aryl ether as shown in Scheme 2. Previous work by Kenneth B.
Wagener has demonstrated that ADMET random copolymerization
of 1,9-decadiene with branched alkenes is an available method to
change the density of branched alkyl units along the polymer's
backbone [34], for which we chose three relatively typical mono-
mers to copolymerize with 1,9-decadiene with the feeding ratio of
1:5 (monomer:1,9-decadiene) (Scheme 2).
2H), 3.81 (t, J ¼ 6.4 Hz, 4H), 2.23e2.11 (m, 5H), 1.80e1.61 (m, 4H),
1.57e1.18 (m, 19H). 13C NMR (75 MHz, Toluene-d8, ppm):
d
¼ 154.5,
131.0, 130.4, 116.4, 69.4, 33.1, 30.3, 30.2, 30.0, 29.8, 26.7. GPC: Mn:
5300, Mw: 12,100, PDI: 2.3. TGA: 399 ꢀC (5% weight loss). DSC: Tm:
81.8 ꢀC, 103.9 ꢀC.
2.3.4. General procedure for the hydrogenation of unsaturated
homopolymers
Unsaturated polymer BP1eP1 (2 g), p-toluenesulfonohydrazide
(TSH) (4.5 mg, 24.2 mmol), tripropylamine (TPA) (3.47 mg,
24.2 mmol), were dissolved in 40e50 mL of p-xylene at a 100-mL
Schlenk flask. The flask was placed in an oil bath set at 130 ꢀC
under vigorous stirring and N2. After 12 h, the reaction was cooling
to room temperature and another supply of TSH and TPA was
added, and the reaction was preceded for another 12 h. The viscous
solution was poured into about 100 mL of cold methanol to obtain a
white precipitate. After filtration and washed by p-xylene and cold
methanol, 1.86 g BP1-HP1 of polymer was obtained. Yield: 93%. 1H
NMR (300 MHz, Toluene-d8, ppm):
d
¼ 6.93 (s, 4H), 3.89 (t,
J ¼ 6.4 Hz, 4H), 3.89 (t, J ¼ 6.4 Hz, 4H), 1.90e1.74 (m, 5H), 1.48 (dd,
J ¼ 22.0, 15.5 Hz, 38H). 13C NMR (75 MHz, Toluene-d8, ppm):
d
¼ 154.2, 116.1, 69.1, 30.0, 29.9, 29.7, 26.4. GPC: Mn: 5000, Mw:
11,700, PDI: 2.3. TGA: 416 ꢀC (5% weight loss). DSC: Tm: 123.3 ꢀC,
134.9 ꢀC.
2.3.5. General procedure for the synthesis of unsaturated
copolymers
The obtained monomers and polymers were characterized by
1H NMR and 13C NMR. Monomer BP1-M1 is featured with one
distinct aromatic signal at 6.82 ppm, and the two signals of ter-
minal alkenes appearing at 5.0 and 5.8 ppm (Fig. 1). The corre-
sponding polymer BP1eP1 exhibits signals of internal alkenes at
5.5 ppm (the cis-trans ratio of the internal alkenes was about 1:3),
meanwhile, signals of the terminal alkene is invisible in the 1H
NMR spectrum, indicative of high molecular weight of unsaturated
polymer. After exhaustive hydrogenation of the unsaturated
polymer, BP1-HP1 is characterized by complete disappearance of
the signals of internals alkenes at 5.5 ppm. Similarly, other
monomers and their corresponding unsaturated and saturated
polymers were also confirmed by 1H NMR. 13C NMR shifts of series
products of BPBP were studied (Fig. 2). Eight aromatic carbons
appear at 157.1, 147.4, 139.0, 132.1, 131.1, 127.4, 125.8, and
113.2 ppm. The bridgehead carbon between the two phenyl groups
appears at 63.6 ppm, upfield with increasing number of the aro-
matic ring attached directly. After polymerization, the terminal
alkenes at 139.2 and 114.1 ppm disappear with the emergence of
internal alkenes at 131.0 and 130.4 ppm. After exhaustive hydro-
genation, the signals of internals alkenes at 131.0 and 130.4 ppm
disappear completely.
The GPC data of saturated polymer were calculated and
collected in Table 1, and GPC curve was also depicted in Sup-
plementary Data Fig. S1. The series products of BPF were char-
acterized by IR (Supplementary Data Fig. S2) and the ratio BP1-
M1 to 1,9-decadiene was calculated via 1H NMR (Supplementary
Data Fig. S3), the integration of the aromatic ring at 6.8 ppm is
compared with the integration of the olefin protons at 5.4 ppm,
and the ratio is 1:2.69 in BP1dd-P7 (1:2.45 in BPFdd-P8 and
1:2.05 in BPBPdd-P9), which corresponds to an actually exper-
imental reaction ratio of one BP1-M1 to 4.4 equivalent 1,9-
decadiene (this ratio is 1:3.9 for BPFdd-P8 and 1:3.1 for
BPBPdd-P9). The final composition in the copolymers is devia-
tion from the initial monomer feeding ratio, mainly due to
different incorporation reactivities of two monomers, and an
inevitable loss for 1,9-decadiene under vacuum should also be
considered.
The same method as described above for ADMET homo-
polymerization was used with a degassed solution of 1.38 g 1,9-
decadiene and 828 mg BP1-M1 (1:5 ¼ BP1-M1: 1,9-decadiene,
monomer ratio) in 1,2-dichlorobenzene (2 mL) with 1.0 mol%
Grubbs' first generation catalyst (10 mg). After 48 h of reaction,
polymerization was terminated by adding the degassed ethyl vinyl
ether (3 mL), and the solution was allowed to stir for 1 h. Then the
solution was poured into acidic methanol to precipitate the poly-
mer. The polymer was filtered, re-dissolved and re-precipitated two
more times to remove the traces of catalyst. Polymer BP1dd-P7
(1.8 g) was recovered as a white solid. Yield: 91%. 1H NMR
(400 MHz, CDCl3, ppm):
J ¼ 6.6 Hz, 2H), 2.14e1.84 (m, 10H), 1.83e1.68 (m, 2H), 1.68e1.50 (m,
2H), 1.50e1.16 (m, 27H). 13C NMR (100 MHz, CDCl3, ppm):
130.3, 129.9, 115.4, 68.7, 32.6, 32.5, 29.8, 29.6, 29.6, 29.5, 29.4, 29.3,
29.2, 29.0, 28.8, 28.7, 27.2, 26.1. GPC: Mn: 2600, Mw: 8600, PDI: 3.3.
TGA: 419 ꢀC (5% weight loss). DSC: Tm: 33.6e66.6 ꢀC.
d
¼ 6.81 (s, 2H), 5.48e5.29 (m, 5H), 3.89 (t,
d
¼ 153.2,
2.3.6. General procedure for the hydrogenation of unsaturated
copolymers
The same method described for BP1-HP1 was used. 1.2 g of
saturated polymer BP1dd-HP7 was obtained. Yield: 96%. 1H NMR
(300 MHz, Toluene-d8, ppm):
d
¼ 6.93 (s, 4H), 3.90 (t, J ¼ 6.4 Hz,
4H), 2.24 (dt, J ¼ 4.4, 2.2 Hz, 6H), 1.96e1.72 (m, 5H), 1.48 (s, 92H),
1.04 (t, J ¼ 6.6 Hz, 3H). 13C NMR (75 MHz, Toluene-d8, ppm):
d
¼ 154.2,116.1, 69.1, 32.1, 30.0, 29.9, 29.7, 29.5, 26.4. GPC: Mn: 3500,
Mw: 7000, PDI: 2.0. TGA: 422 ꢀC (5% weight loss). DSC: Tm: 99.6 ꢀC,
106.8 ꢀC.
More synthesis procedures and NMR data of other products
could be available in Supplementary Data.
3. Results and discussion
3.1. Synthesis and characterization of monomers and polymers
All the six monomers were synthesized via standard Wil-
liamson ether synthesis with sodium hydroxide or sodium

S. Song et al. / Polymer 64 (2015) 76e83
79
Scheme 1. Synthetic route of polyethylene periodically spaced with aromatic ether.
3.2. Thermal properties
128 ꢀC, and re-melts at 134.9 ꢀC. BPF-HP4 exhibits the similar
behavior. In fact, this similar phenomenon has also been found in
reported polymers [35,36], but here it still shows distinct features.
To explain this phenomenon, we propose two possible mecha-
nisms. The first hypothesis involves the melting of the smaller
imperfect crystals, followed by recrystallization to more perfect and
larger crystals, and eventually the melting of these larger crystals at
a higher temperature. The second hypothesis suggests trans-
formation of crystal forms at elevated temperature, as one crystal
form is melted at low temperatures, and the other form is crys-
tallized and subsequently melted at high temperatures.
In order to verify the first hypothesis, we obtained the DSC
curves of BP1-HP1 as different heating rates. As shown in Fig. 4(b),
the crystallizing peak of the heating run becomes bigger with
decreasing heating rate. BP2-HP2 exhibits similar behavior
(Supplementary Data Fig. S4). On the other hand, as the heating rate
increases, the crystallizing peak is diminishing, and completely
disappears at the heating rate of 30 ꢀC/min. We suspect that the
Thermal properties of saturated polymers were systematically
studied with TGA and DSC, and the data were collected in Table 1.
Polymer decomposition temperatures (Td) were presented as the
5% weight loss temperature under nitrogen. Glass transition tem-
peratures (Tg), melting points (Tm) and crystallization behaviors of
these polymers were measured by DSC, all the samples were pro-
cessed through a heating-cooling-heating procedure unless other-
wise noted. The first heating runs from room temperature to the
temperatures 30 ꢀC above their melting points were performed to
eliminate the thermal history of the samples. The actual heating
curves and data came from the second heating runs.
The results of the cooling run are shown in Fig. 3(a), indicating a
distinct single peak for all three polymers BP1-HP1, BP2-HP2 and
BPF-HP4. Surprisingly, the subsequent heating curves shown in
Fig. 3(b) reveal unusual melting behaviors for these polymers. For
example, BP1-HP1 first melts at 123.3 ꢀC, but then it crystallizes at
Scheme 2. Copolymerization and hydrogenation of random copolymers, BP1dd-HP7 (corresponding monomer BP1-M1), BPFdd-HP8 (corresponding monomer BPF-M4) and
BPBPdd-HP9 (corresponding monomer BPBP-M6).

80
S. Song et al. / Polymer 64 (2015) 76e83
Fig. 1. 1H NMR of BP1. (a) Monomer, BP1-M1, (b) Unsaturated polymer, BP1eP1, and (c) Saturated polymer, BP1-HP1.
large rigid aryl ether units restrict the movement of polymer
chains, and if high cooling rate is applied, there may be no enough
time for crystallizing, thus these units prevent polymers from
forming larger crystals during the cooling run.
To provide evidence for the second hypothesis, BP1-HP1 sam-
ples with three different thermal histories were prepared for XRD.
BP1-HP1-a is collected after cooling run, BP1-HP1-b is quenched
after annealing at 60 ꢀC for 10 min, another sample BP1-HP1-c is
quenched at 128 ꢀC marked by asterisk in Fig. 3(b) where it ac-
complishes crystallization. If the crystal form transformation
hypothesis is valid, we expect that the sample BP1-HP1-a has both
forms, sample BP1-HP1-b has mainly the first crystal form, and
sample BP1-HP1-c has mostly the second crystal from. However,
after XRD test as shown in Fig. 5, all three samples have the same
orthorhombic unit cell structure with two characteristic crystal-
lizing peaks observed at 2
q
¼ 21.5ꢀand 24.0ꢀ, corresponding to
reflection planes (110) and (200) respectively. Therefore, this
sequence of melting/crystallization phenomenon should not be due
to transformation of crystal forms. X-ray diffractograms for BP2-
HP2 and BPF-HP4 were shown in Supplementary Data Fig. S5.
Fig. 2. 13C NMR of BPBP. (a) Monomer, BPBP-M6, (b) Unsaturated polymer, BPBP-P6, and (c) Saturated polymer, BPBP-HP6.

S. Song et al. / Polymer 64 (2015) 76e83
81
Table 1
Summary of saturated polymer molecular weights and thermal properties.
Polymer
Tm (ꢀC)a
Tg (ꢀC)a Td (ꢀC)b Mn (kDa)c Mw (kDa)c PDI
BP1-HP1
BP2-HP2
123.3, 134.9
128.2, 133.1
77.6, 90.4
127.2, 132.4
e
e
416
422
411
426
425
406
422
418
430
5.0
19.3
6.7
11.7
26.9
18.1
22.4
18.4
19.8
7.0
2.3
1.4
2.7
2.8
1.5
1.9
2.0
2.3
2.4
e
BPA-HP3
BPF-HP4
BPAP-HP5
BPBP-HP6
BP1dd-HP7
BPFdd-HP8
e
e
8.0
ꢁ6
20
e
12.2
10.4
3.5
13.5
5.6
e
99.6, 106.8
102.6
e
30.5
13.6
BPBPdd-HP9 88.4
e
a
Determined via DSC, 10 ꢀC/min scan rate, values determined from the second
scan data, Tm is defined as the peak value, Tg is from the heating curve.
b
Given as the 95% weight loss temperature, 10 ꢀC/min.
Determined via GPC (1 mL/min in trichlorobenzene) with curves shown in
c
Supplementary Data Fig. S1, 3
‰ concentration, using polystyrene calibration.
The melting behavior of BPA-HP3 is similar with above samples,
but the melting point of BPA-HP3 (Fig. 6), Tm2 ¼ 90.4 ꢀC, is lower
than that of BP1-HP1, BP2-HP2 and BPF-HP4. This may be because
that the two methyl groups inserted between the two phenyl rings
in every aryl ether unit, reduces the effect from rigidity of the aryl
Fig. 4. DSC curves of BP1-HP1 in different scanning rate. Cooling run (a) and Heating
run (b).
ether units and offers a relative better flexibility for the polymers.
Therefore, the melting point is decreased. This trend from BP1-HP1,
BP2-HP2 and BPF-HP4 to BPA-HP3 indicates that methyl groups
and methylene unit between the two phenyl groups have a large
effect on the structure and thermal behavior of polymers.
DSC also reveals glass transitions temperatures (Tg) of series
polymers of BPAP and BPBP of Scheme 1. Unlike polymers dis-
cussed above, polymers of BPAP and BPBP show amorphous after
the incorporation of one or two more aromatic rings
(Supplementary Data Fig. S6). And hydrogenation brings the Tg up
to high values. Glass transition temperature of polyethylene ranges
from ꢁ150 ꢀC to ꢁ50 ꢀC [37], herein the ethylene-co-aryl ether
polymers show higher Tg values than polyethylene, which is
probably due to that rigid groups like these aryl ether units enhance
the rigidity of polymers, thus the decreased flexibility leads to
improving Tg.
The random copolymers exhibit Tg and Tm in a typical way (Fig. 7
and Supplementary Data Fig. S7). BPFdd-P8 exhibits semi-
crystallinity with Tm ¼ 40.6 ꢀC, and hydrogenation brings the Tm to
102.6 ꢀC. However, BPBPdd-P9 are amorphous with Tg ¼ 8 ꢀC,
which is higher than the corresponding unsaturated homopolymer
BPBP-P6 (Supplementary Data Fig. S6), and hydrogenation
Fig. 3. DSC curves of BP1-HP1, BP2-HP2, and BPF-HP4. Cooling run (a) and heating
run (b), 10 ꢀC/min.

82
S. Song et al. / Polymer 64 (2015) 76e83
Fig. 5. XRD of BP1-HP1 after different heat treatment process, BP1-HP1-a is collected
after cooling run, BP1-HP1-b is quenched after annealing at 60 ꢀC for 10 min, another
sample BP1-HP1-c is quenched at 128 ꢀC marked by asterisk in Fig. 3(b) where it
finishes crystallization.
Fig. 7. DSC curves of BPFdd-HP8 and BPBPdd-HP9.
Decomposition temperature (Td) of unsaturated polymers var-
ied from 169 ꢀC in BPAP-P5 to 410 ꢀC in some polymers
(Supplementary Data Fig. S9), since it is possible that a small
amount of solvent remains trapped within BPAP-P5, which could
account for the lower Td around the boiling point of 1,2-
dichlorobenzene (180.4 ꢀC), and its Td could be inferred as about
420 ꢀC at 10% weight loss from the curve. Decomposition temper-
ature (Td) of saturated polymers varied from 406 ꢀC in BPBP-HP6 to
430 ꢀC in BPBPdd-HP9 (Fig. 8). Other polymers displayed inter-
mediate values. Overall, the polymers exhibited higher thermal
stability on average than the commercial polyethylene with Td of
about 300 ꢀC [38], which indicates that inserting such aryl ether
units into the main chains of polyethylene has introduced the heat
resistance property of poly (aryl ether) into polyethylene.
transforms it to semicrystallinity with Tm ¼ 88.4 ꢀC. Not surpris-
ingly, the copolymer BPBPdd-HP9 exhibits semicrystallinity when
the methylene distance is increased after the disappearance of
internal alkenes since crystalline chain segments become
longer. Both BP1dd-HP7 and its corresponding unsaturated
copolymer BP1dd-P7 exhibit wide melting/crystallization range
(Supplementary Data Fig. S8). This could possibly be caused by
heterogeneous composition and the relatively low molecular
weight of BP1dd-P7 and BP1dd-HP7. Here, reducing the density of
aryl ether units in the main chain of polymers weakens their effects
on the thermal behaviors shown above, and ethylene segments
exhibit an increasingly dominant influence.
By regulating the identity and distribution of the aryl ether units
inserted in the main chains of polyethylene, promisingly, control-
ling of the melting point and secondary structures even the ag-
gregation state of the new series of polymers could be achieved,
which can be a reference for design of well-defined polymer to
study the structureeproperty relationship.
4. Conclusion
Ethylene-co-aryl ether polymers periodically containing a series
of aryl ether units was successfully synthesized via ADMET poly-
merization followed by hydrogenation. The structureeproperty
relationship has been systematically investigated by tuning the
Fig. 6. DSC of BPA-HP3 with 10 ꢀC/min as heating and cooling rate.
Fig. 8. TGA traces of the saturated homopolymers and copolymers.

S. Song et al. / Polymer 64 (2015) 76e83
[8] Steinmann M, Markwart J, Wurm FR. Macromolecules 2014;47:8506e13.
83
steric bulkiness of aryl ether units incorporated in the ethylene
segment. Morphology of semicrystallinity to amorphous state was
found by periodical insertion of larger aryl ether units into specific
location in the main chain. BP1-HP1, BP2-HP2 and BPF-HP4 display
a sequence of melting/crystallization phenomenon, irrelevance of
the aryl ether units in the functional sites of main chain. Typical
orthorhombic unit cell structure has been revealed by XRD in those
semicrystallinity polymers. The more bulky aryl ether groups based
BPA-HP3 exhibits a weak crystallization behavior, while polymers
of BPAP and BPBP with more phenyl rings in every aryl ether units
show amorphous state. Three random copolymers obtained from
BP1-M1, BPF-M4, BPBP-M6 copolymerizing with 1,9-decadiene
also exhibit semicrystallinity, as the longer ethylene segments were
incorporated in the main chain of polymers. Notably, incorporation
of these aryl ether units has also increased the thermal stability of
polymers, demonstrating the heat resistance property of poly (aryl
ether) was successfully introduced into polyethylene.
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Acknowledgment
We thank Professor Yongfeng Men (Changchun Institute of
Applied Chemistry, Chinese Academy of Sciences) for helpful dis-
cussion on the sequence of melting/crystallization phenomenon of
polymers. This work is financially supported by National Natural
Science Foundation of China (No. 21274070), the Ningbo “3315”
Program (Class A) (No. 2012S0001), the Program for Zhejiang
Leading S&T Innovation Team (2011R50001), the Ningbo S&T Pro-
gram (No. 2011A31002), and the Global Recruitment Program of
Foreign Experts (No.2013-211).
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