Synthesis and properties of poly(aryl ether sulfone)s incorporating cage and linear organosiloxane in the backbones

Article abstract of DOI:10.1016/j.polymer.2015.02.028

A series of novel copoly(aryl ether sulfone)s with polydimethyl (PDMS) and double-decker-shaped silsesquioxane (DDSQ) in the main chain were synthesized by nucleophilic substitution polymerization approach. Dihydroxy terminated eugenosiloxanes (2OH-PDMS-n

Full text of DOI:10.1016/j.polymer.2015.02.028

Polymer 62 (2015) 77e85
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Polymer
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Synthesis and properties of poly(aryl ether sulfone)s incorporating
cage and linear organosiloxane in the backbones
Jiuduo Xu, Weihai Zhang, Qiyang Jiang, Jianxin Mu*, Zhenhua Jiang
College of Chemistry, The Key Lab of High Performance Plastics, Ministry of Education, Jilin University, ChangChun 130012, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel copoly(aryl ether sulfone)s with polydimethyl (PDMS) and double-decker-shaped sil-
sesquioxane (DDSQ) in the main chain were synthesized by nucleophilic substitution polymerization
approach. Dihydroxy terminated eugenosiloxanes (2OH-PDMS-n) and 3,13-di(2-methoxy-4-
propylphenol)octaphenyl DDSQ (2OH-DDSQ) were synthesized. These two difunctional oligomers
were used to copolymerize with 4-fluorophenyl sulfone to obtain poly(aryl ether sulfone) containing
cage and linear organosiloxane (Si-PES) through one-step high-temperature solution method. Si-PES
with multiple PDMS and DDSQ contents in the main chains were obtained by adjusting the molecular
weight of 2OH-PDMS-n and controlling the molar ratio of 2OH-DDSQ to 2OH-PDMS-n. The dielectric
constants sharply decreased as organosiloxane was introduced compared with traditional PES which the
lowest value was achieved at 5% DDSQSiePES (2.36 at 1 MHz). In addition, enhanced hydrophobic ca-
pacity peaks were obtained at 50% DDSQSi-PES surface hydrophobicity (113ꢀ) as the synergies of both
linear organosiloxane and DDSQ. Furthermore, thermal and crystallization behaviors, as well as surface
properties, were investigated.
Received 9 October 2014
Received in revised form
13 January 2015
Accepted 16 February 2015
Available online 21 February 2015
Keywords:
Poly(aryl ether sulfone)s
Organosiloxane
Low dielectric constant
© 2015 Elsevier Ltd. All rights reserved.
1. Introduction
group to the terminal of polymer chains is difficult to get the
polymer with high POSS content. For the third method, there have
Polyhedral oligomeric silsesquioxanes (POSS), having an inner
cage with an inorganic silicon and oxygen framework which is
covered externally by organic substituents, are cube-octameric
molecules of nanoscale dimensions that may be functionalized
with reactive groups suitable for the synthesis of new organic-
inorganic hybrids as well as their application in optics, catalysis,
and electronics [1e5]. In the past years, there has been ample
literature to report the preparation of POSS-containing composites,
including (i) POSS macromers bearing single polymerizable (or
reactive) groups were grafted onto polymer chains; (ii) A reactive
grafing approach copolymerizes with other monomers' ends of
organic polymers; and (iii) Prepare POSS-containing nano-
composites by the use of multi-functional POSS macromers. POSS-
containing composites obtained by first method, sometimes,
exhibit an ill defined structure as incomplete grafting reaction. The
second method could get the end modification composite, but only
capped POSS macromers bearing single polymerizable (or reactive)
been some reports on the preparation of POSS-containing nano-
composites by the use of multi-functional POSS macromers [6e10].
Because of multiple sites on POSS with equivalent reactivity it is
rather difficult to introduce only two functional groups, so poly-
merization from the POSS monomers typically generates insoluble
cross-linked polymers [11e13]. And the cross-linked polymers
cannot be processed as linear polymers [14e16]. It is expected that
linear organic-inorganic copolymers with POSS in the main chains
can be accessed via one-step polymerization while difunctional
POSS macromers are utilized. Double-decked silsesquioxane
(DDSQ) is a kind of difunctional POSS [17e25]. For many applica-
tions, the preparation of organic-inorganic hybrids with DDSQ in
the main chains is desirable owing to the simplicity in the materials
processing and the good symmetry to ensure high chain regularity
and POSS content of the hybrids [22,26e31].
Poly(aryl ether sulfone) (PES) is an engineering thermoplastic
used in aviation, military, and electronic field. PES exhibits many
excellent properties, such as high service temperature, resistance to
chlorinated disinfectants, hydrolysis, and oxidation, as well as
certain mechanical properties. However, as common traditional
thermoplastics, PES could behave in poor hydrophobic (CA ¼ 80ꢀ)
* Corresponding author.
E-mail address: jianxin_mu@jlu.edu.cn (J. Mu).
http://dx.doi.org/10.1016/j.polymer.2015.02.028
0032-3861/© 2015 Elsevier Ltd. All rights reserved.

78
J. Xu et al. / Polymer 62 (2015) 77e85
manner as O]S]O and ether bond [32]. Moreover, dielectric
constant of PES (k ¼ 3.4) can not be satisfied the demand in elec-
tronic packaging and large scale integrated circuit. According to the
previously reports, incorporating DDSQ into the main chains of
polymer can significant lower the dielectric constant as DDSQ
having an inner cage with an inorganic silicon and oxygen frame-
work [18,24,28]. However, the copolymers with DDSQ in the main
chains are highly rigid because their bulky side groups may inter-
fere with each other, which give rise to very low number of
macromolecular conformations and the macromolecular have poor
toughness [24]. On the other hand, with the same compositions of
DDSQ, linear organosiloxane polydimethysiloxanes (PDMSs) serve
as good toughening and hydrophobic agents for organic-inorganic
copolymers because of the silicon-based spiral arrangement of
the molecular chains, which lead to strong chain flexibility and high
surface energy [33]. Therefore, PDMSs have attracted significant
attention on the PES modification [34]. Patel, Noshay, and Gorfield
employed condensation of PDMS with PES series to gain tougher
PES [35]. In addition, Auman, Madec, and Nagase introduced SieC
instead of SieOeSi linkages, the copolymer was difficult to hy-
drolyze, and its physical properties were excellent [36e39].
at room temperature (25 ꢀC). The samples were scanned within the
range of 400 cmꢁ1-4000 cmꢁ1. Gel permeation chromatograms
were obtained using
a Waters 410 instrument with Dime-
thylformamide (DMF) as an eluant, at a flow rate of 1 mL minꢁ1
using polystyrene as a standard. The density of the polymers was
obtained by ALFA MIRAGE SD-200L Density tester. Differential
Scanning Calorimeter (DSC) measurements were performed using a
Mettler Toledo DSC821e instrument at a heating rate of 10 ꢀC/min
from 0 ꢀC to 300 ꢀC under nitrogen atmosphere. 1H NMR spectra
was obtained using Brüker Advance 300 spectrometer (300 MHz),
whereas 29Si NMR was obtained using a Brüker 510 NMR spec-
trometer (500 MHz). The chemical shifts relative to tetramethylsi-
lane, which is used as an internal reference. Solid-state 29Si NMR
experiment was performed on a Varian Infinity plus 400WB spec-
trometer with BBOMAS probe operating at a magnetic field
strength of 9.4 T. The resonance frequency in this field strength was
79.5 MHz for 29Si NMR. Chemical shifts were referenced to 1.0 M
2,2-dimethyl-2-ilapentane-5-sulfonate sodium salt, and the spin-
ning rate of the samples at the magic angle was 4 kHz. The MALDI-
TOF-MS experiment was performed using Shimadzu/AMIMA-CFR.
The matrix 2,5-dihydroxybenzoicacid (98% purity) was dissolved
in THF (10 mg/mL) and mixed with the sample solution (0.5 mg/
mLe1.0 mg/mL in THF) at 1:1 v/v. The samples were dried in air for
at least 30 min, and the measurements were obtained in linear
mode using a UV laser (337 nm). The spectra were calibrated using
bradykinin dissolved in THF (10 mg/mL) and mixed with the sample
So, in this study, dihydroxy terminated cage (DDSQ) and linear
organosiloxane (PDMS) oligomers were used to copolymerize with
4-fluorophenyl sulfone to obtain poly(aryl ether sulfone) contain-
ing cage and linear organosiloxane (Si-PES) through one-step high-
temperature solution method.
A research was conducted to
investigate the effect of organosiloxane content and structure on
the dielectric, thermal behavior, and surface properties of hybrid
copolymers.
solution at 0.5 mg/mLe1.0 mg/mL. The ks of the polymer films
(coated with silver through vacuum evaporation method) were
obtained using a HewlettePackard 4285A apparatus at room tem-
perature and at frequency of 103 Hze106 Hz. The crystallization
behavior of hybrid polymers were studied using a Rigaku D/max-
2. Experimental
2500 X-ray diffractometer with CuK
a
radiation (
l
¼ 0.154 nm) as
2.1. Materials
the X-ray source. Contact angle (CA) measurements were obtained
at room temperature using a POWEREACH/JC2002C2 CA meter
with pure water as probe liquid. The dispersion of POSS clusters in
the polymer matrix was observed using SSX-550 Shimadzu Scan-
ning Electron Microscope.
2OH-DDSQ was synthesized in our laboratory according to the
literature [24]. 1,1,3,3-Tetramethyldisiloxane (AR), methyldi-
chlorosilane (AR), and BPA were purchased from Aladdin Industrial
Corporation and immediately used upon receipt. Octamethylcy-
clotetrasiloxane was obtained from Hangzhouzhixin Chemical In-
dustry and was further purified. The Kg-23 chain extender was
acquired from Mendeleyev University of Chemical Technology in
Russia. Phenyltrimethoxysilane was purchased from Energy
Chemical and was immediately used upon receipt. Anhydrous
magnesium and anhydrous calcium chloride were purchased from
Guangdong Xilong Chemical. Triethylamine (AR) was purchased
from Tianjin Fuyu Fine Chemical. Tetrahydrofuran (THF) (AR) was
purchased from Tianjin Tiantai Fine Chemicals. Toluene (AR), ethyl
acetate (AR), chloroform (AR), sodium hydroxide (AR), N,N-
dimethylacetamide (DMAc; AR), 2-propanol (AR), and dimethyl
sulfoxide (DMSO; AR) were purchased from Beijing Chemical
Works. Potassium carbonate (AR) and N-methyl-2-pyrrolidinone
(NMP; AR) were obtained from Tianjin BODI chemicals. NMP was
further purified.
2.3. Oligomers synthesis
2.3.1. Synthesis of dihydroxy-terminated eugenosiloxanes
1,1,3,3-Tetramethyldisiloxane
(1.3432
g,
10
mmol),
octamethylcyclotetra-siloxane (2.966 g, 10 mmol), and Kg-23
catalyst (0.2155 g) were placed in a 25 mL two-necked, round-
bottomed flask equipped with a magnetic stirrer, a nitrogen inlet
containing thermometer, and an anhydrous calcium chloride dry-
ing tube, which was connected to a reflux condenser. The reaction
system was heated to 80 ꢀC under nitrogen atmosphere for 12 h.
After removing toluene through rotary evaporation, and it was then
purified at 120 ꢀC in a vacuum for 24 h. Viscous transparent oil
hydrogenterminated eugenosiloxanes monomer, which has six Si
atoms in its chemical formula (2H-PDMS-6), was obtained. Yield:
93%. Meanwhile, dihydroxy terminated eugenosiloxanes, which
has n Si atoms in the chemical formula (2OH-PDMS-n), was syn-
thesized using the method of Islam Mollah et al. [39]. Generally, the
oil hydrosilylated with eugenol, catalyzed by Karstedt's catalyst
with toluene dried exist, as shown in Scheme 1.
2.2. Characterization techniques
Thermogravimetric analysis (TGA) was performed to assess the
thermal stability of membranes using a Perkin Elmer Pryis 1 TGA
thermal analyzer under nitrogen atmosphere. Before performing
the analysis, the samples were dried and kept inside the TGA
furnace, which was isothermal at 100 ꢀC for 20 min. Then, the
samples were reheated up to 800 ꢀC at 10 ꢀC/min, and the tem-
peratures that resulted in 5% and 10% weight loss were recorded for
each sample. IR spectra (KBr pellets or films) were conduct on a
Nicolet Impact 410 Fourier Transform Infrared Spectrometer (FTIR)
Meanwhile, 2H-PDMS-6 (7.5934 g, 10 mmol), eugenol (1.806 g,
11 mmol), platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane
complex (Karstedt's catalyst) (0.05 g, 10ꢁ5 mol), and toluene
without water (38 mL) were placed in a 50-mL three-necked flask,
equipped with a mechanical stirrer, a nitrogen inlet, and a
condenser, and refluxed for 24 h. After which, toluene was removed
through rotary evaporation. A transparent, little yellow product
was obtained. Yield: 89%. 1H NMR (300 MHz, DMSO-d6,
d, ppm):

J. Xu et al. / Polymer 62 (2015) 77e85
79
Table 1
Synthesis parameters and yield of polymers.
Samples
4-Fluorophenyl 2OH-PDMS-6 2OH-DDSQ Yield (%)
sulfone(mol)
(mol)
(mol)
0% DDSQSi-PES
5% DDSQSi-PES
10% DDSQSi-PES
30% DDSQSi-PES
50% DDSQSi-PES
0.004
0.004
0.004
0.004
0.004
0.004
0.0038
0.0036
0.0028
0.0020
0
0
92.3%
89.9%
89.5%
92.1%
88.0%
90.5%
0.0002
0.0004
0.0012
0.0020
0.004
100% DDSQSi-PES 0.004
were synthesized in the main chain as shown in Scheme 2. More-
over, for the preparation of 30% DDSQeSi-PES copolymer, 4-
fluorophenyl sulfone 1 (2.543 g, 10 mmol), 2OH-DDSQ (4.4465 g,
3 mmol), and 2OH-PDMS-6 (5.3154 g, 7 mmol) were placed in a
100-mL three-necked flask equipped with a mechanical stirrer, a
nitrogen inlet with a thermometer, and a DeaneStark trap with a
condenser. The mixture was then dissolved in NMP (49 mL) and
toluene (25 mL). The solution was refluxed for 3 h after adding
K2CO3 (1.659 g, 12 mmol) under nitrogen atmosphere. A substantial
amount of the resulting water and toluene were removed. The re-
action system continued to react for 6 h at 160 ꢀC. The viscous
solution was then poured into a container with deionized water
and a flexible thread-like precipitate was produced for a period of
time before pulverizing into powder using a blender. The polymer
was refluxed in deionized water and ethanol for several times to
remove salts and solvents. It was then dried at 110 ꢀC for 24 h to
obtain a constant weight. Yield was 92%.
The procedure for the synthesis of other Si-PES copolymers was
conducted using the same method, while modifying the feed ratio
of 2OH-DDSQ. All the organic-inorganic Si-PES with DDSQ in the
main chains were subjected to gel permeation chromatography
(GPC) to measure their molecular weights. The GPC profiles were
shown in Table 2. In all cases, high-molecular-weight products
were obtained. Similar results of polymerization have been re-
ported in other organiceinorganic copolymers with POSS in the
main chains [2,41].
Scheme 1. Synthesis of dihydroxy terminated eugenosiloxanes.
0.012 to 0.048 (m, 36H, eSieCH3), 0.525 (t, 4H,
SieCH2eCH2eCH2e), 1.494e1.601 (m, 4H, SieCH2eCH2eCH2e),
2.434e2.485 (t, 4H, eCH2eCH2eCH2e), 3.716 (s, 6H, eOCH3),
6.504e6.682 (m, 4H, ArH), 8.614 (s, 2H, ArH).
The procedure for the synthesis of other dihydroxy terminated
eugenosiloxanes containing n Si atoms in the chemical formula
(2OH-PDMS) oligomers was conducted using the same method,
only modifying the feed ratio of 2OH-DDSQ.
2.4. Polymer synthesis
2.5. Film preparation for the measurement
2.4.1. Synthesis of copoly(aryl ether sulfone)s having PDMS and
DDSQ in the main chain (Si-PES)
The polymer solutions were dissolved in DMAc (1 g/10 mL). A
2OH-DDSQ was synthesized based on the method used by Mu
et al. [24]. 4-Fluorophenyl sulfone at various molar ratios was
copolymerized to form 2OH-PDMS. Different copoly(aryl ether
sulfone)-containing structures with different silicone contents
Teflon syringe filter, with a pore size of 0.22 mm, was used to filter
the solution onto an 8 cm ꢂ 8 cm smooth Teflon plate with a
programmed procedure (60 ꢀC, 12 h; 80 ꢀC, 12 h; 120 ꢀC, 6 h). The
temperature is maintained at 120 ꢀC for another 6 h, wherein
Scheme 2. Synthesis of copoly(aryl ether sulfone)s incorporating organosiloxane in the backbone.

80
J. Xu et al. / Polymer 62 (2015) 77e85
Table 2
Summary of the properties of the Si-PES.
c
e
Samples
Tg (ꢀC)a
Td5 (ꢀC)b
Td10 (ꢀC)b
CA (deg)
Dielectric constant (
k)
Residue (%)d
Mn
PDIf (Mw/Mn)
Densityg (g/cm3)
0% DDSQSi-PES
5% DDSQSi-PES
10% DDSQSi-PES
30% DDSQSi-PES
50% DDSQSi-PES
100% DDSQSi-PES
55
70
72
84
103
130
440.0
354.2
376.6
362.9
367.7.
377.3
437.5
421.2
425.8
413.1
448.2
472.9
103.2
104.5
105.8
107.5
114.2
97.5
2.74
2.36
3.05
2.81
2.75
2.68
11.65
20.67
25.29
28.84
31.86
38.41
38,876
54,448
36,962
22,012
23,474
9861
1.61
2.67
1.89
1.39
1.69
1.32
1.0525
1.0759
1.1491
1.2233
1.2732
1.3028
a
DSC at a heating rate of 10 ꢀC/min in nitrogen.
b
c
d
e
f
Temperature at which 5% weight loss was recorded by thermogravimetry at a heating rate of 10 ꢀC/min in nitrogen.
was measured at 1 MHz.
The yields of degradation residues were obtained at 800 ꢀC in nitrogen.
Mn values were determined by GPC in DMF with PS as standard.
PDI values (Mw/Mn) were determined by GPC in DMF with PS as standard.
Density values were determined by density tester.
k
g
certain level of transparency, smoothness, and toughness were
obtained on the films.
Fig. 3. The molecular weight distribution in a narrow spectrum and
its concentration around the number 781.28 is shown in the
spectrum. The monomer spectra perfectly matched the value
calculated based on the structural formula (Scheme 1). The MALDI-
TOF mass spectra of the 2OH-PDMS presented in Fig. 3 show
intense mass peaks at constant mass increments of 74 Da corre-
sponding to the -Si(CH3)2O- group. In MALDI-TOF mass spectra two
fragment ion distributions were observed, which were assigned to
the series A and B. Base on the molecular masses of the fragment
were assigned (Table 4). The fragment A and B were caused by
cleavage between a silicon and oxygen atom. From the peak of n ¼ 1
(557.1) to n ¼ 13 (1465.4) can really be distinguished in the figure.
The value and structure of end-groups (M1 ¼ 238, M2 ¼ 223) can be
identified through the analysis of the calculation formula:
3. Results and discussion
3.1. Synthesis and characterizations
The synthesis of 2OH-PDMS-n were obtained via two stages,
namely, cationic ring opening polymerization to allow hydrosilyl-
terminated polydimethylsiloxane prepolymer and hydrosilylation
with eugenol using a platinum catalyst. The molar mass and the
molecular chain length of 2OH-PDMS-n were controlled by
changing the mass ratio of 1,1,3,3-tetramethyldisiloxane as end-
capper.
1H NMR spectra of 2OH-PDMS-6 are shown in Fig. 1. The ratio of
the integration intensity of signals at 2.458, 1.547, and 0.553 ppm is
1:1:1. The data matches well with the value calculated rely on
structural formula. Signals of resonance disappeared at 4.75 ppm,
which were assigned to the protons of SieH group in 2H-PDMS-6
suggesting that the hydrosilylation has completed.
Mend ¼ Mpeak ꢁ Mcat ꢁ nMre
MPeak is the value of the corresponding peak; Mcat is Cationic
quality; Mre represents a repetitive unit value [40]. The results of
29Si NMR, 1H NMR, and mass spectroscopy indicate that 2OH-
PDMS-6 was successfully obtained.
2OH-PDMS-ns were synthesized and utilized to copolymerize
with 4-fluorophenyl sulfone and 2OH-DDSQ in NMP through a one-
step high-temperature solution method using a series of molar
ratios (Table 1). Si-PES was characterized by FTIR, 1H NMR, and 29Si
NMR spectra. Based on the Fig. 4 of FTIR spectrum, the peaks at
1086 cmꢁ1 and 480 cmꢁ1 were attributed to SieO band of the 2OH-
PDMS and 2OH-DDSQ. The peaks at 1259 cmꢁ1 and 725 cmꢁ1 were
The 29Si NMR spectrum of 2OH-PDMS-6 is shown in Fig. 2 in
which the orthopositioned OeSieCH2e groups appeared at ꢁ21.59
and ꢁ22.12 ppm at the downfield of the spectra. The resonance at
7.67 ppm was ascribed toeSieOeSie.
2OH-PDMS-6 was subjected to MALDIeTOFeMS spectroscopy
to derive its molecular weight. The mass spectrum is presented in
Fig. 1. 1H NMR spectrum of 2OH-PDMS-6 in d6-DMSO.
Fig. 2. 29Si NMR spectrum of 2OH-PDMS-6 in d6-DMSO.

J. Xu et al. / Polymer 62 (2015) 77e85
81
Intens.
[%]
+MS, 0.1min #4
781.3
100
80
707.3
855.3
929.3
60
40
20
0
1003.3
1077.4
1152.4
633.2
467.1
1226.4
557.1
1316.4
371.1
318.3
1390.4
1400
1465.4
400
600
800
1000
1200
1600
m/z
Fig. 3. MALDIeTOFeMS spectrum of 2OH-PDMS-6.
attributed to SieC band. Meanwhile, 1504 cmꢁ1 and 1591 cmꢁ1
were attributed to methylene. Lastly, the peak at 2936 cmꢁ1 was
attributed to SieMe band.
temperatures at 10% weight loss (Td 10%) are above 390 ꢀC under
N2. From Fig. 7, the temperatures at maximum rate of degradation
of all polymers were increased as the content of DDSQ increased.
Copolymers displayed two steps in degradation progress. During
first step, weight loss at 330 ꢀC was attributed to the cleavage of
alkyl chains. The second step was assigned to POSS cage and aro-
matic ring. The temperatures at maximum rate of degradation of all
copolymers were significantly higher than those of polymers
without the DDSQ. This suggests that the presence of POSS moiety
in the main chains retarded the random-chain scission. Organ-
iceinorganic copolymers displayed higher residuals of degradation
than polymers without the DDSQ, and the yields of degradation
residues increased as POSS content increased. The increased yields
of degradation residues were attributed to the ceramic formation
on POSS moiety during thermal decomposition. Thus, the thermal
stability of Si-PES membranes could be used in most functional
materials.
The structures of the copolymer were subjected to 1H NMR and
29Si NMR spectra. Fig. 5 shows the 1H NMR spectra obtained using
300 MHz Bruker 510 spectrometer and deuterated dimethylsulf-
oxide as a solvent. The organic-inorganic Si-PES characteristic sig-
nals of proton at 0.02, 0.54e2.58, and 3.63 ppm were assigned to
the protons of methyl, methylene, and methoxy, respectively. The
peaks at 6.5 ppme8.0 ppm were assigned to the protons of aro-
matic ring. The intensity of the peak at 7.3 ppm was increasing,
whereas at 0.1 ppm, it was decreasing. The constant increase in
DDSQ also confirms that DDSQ nanoparticles and PDMS were
successfully introduced into the main chains of the polymer by
covalent bonds. Based on solid-state 29Si NMR spectrum of 30%
DDSQSi-PES (Fig. 6), three resonance signals appeared
at ꢁ76.5, ꢁ17.55, and 10.1 ppm, which indicate the presence of the
structural units of eO1.5Si(Ph)- and eO1.5Si(Me)2-.
3.3. The crystallization behavior of Si-PES
3.2. Thermal properties of Si-PES copolymers
The aggregation of organic-inorganic copolymer films, with
DDSQ and PDMS in the main chains, were subjected to wide-angle
X-ray diffraction (WAXRD), and the WAXRD curves are shown in
Thermal properties of Si-PES were evaluated using DSC and TGA.
The thermal performance data of all Si-PES are shown in Table 3.
The test results indicated that the Tg values of the copolymer
increased as the content of DDSQ in the main chain of copolymers
increased. The Tg of 0%DDSQSi-PES was about 55 ꢀC, and Tg of 100%
DDSQSi-PES was about 130 ꢀC. This phenomenon was due to the
nano reinforcement of POSS cages in the main chains, which
limited the movement of the chain segment. The thermal stability
of Si-PES copolymers was investigated using TGA in a nitrogen at-
mosphere, as shown in Fig. 7. No obvious weight loss was observed
prior to 330 ꢀC for all polymers, which suggested they were
excellent, thermally stable materials. As summarized in Table 2,
temperatures at 5% weight loss (Td 5%) are above 370 ꢀC, whereas
Fig. 8. All WAXRD curves show that the 2q had two broad amor-
phous peaks, about 6.6ꢀe7.1ꢀ and 16.7ꢀe18.6ꢀ because of the
nanoscale dimensions in the polymer main chain of DDSQ moiety.
No crystalline behavior was observed because of the absence of
sharp peaks. However, we can see that the increase in DDSQ con-
tent resulted in the increase in the first peak (2
q
¼ 7.3ꢀ) intensity
and the decrease in halfpeak width. This phenomenon revealed
that the copolymer, which has a higher amount of DDSQ, has better
chain regularity. Corresponding molar ratio of DDSQ and PDMS has
been introduced into the main chain of the copolymers.
Table 4
Table 3
Representation of the assigned structure of the fragmentation series of 2OH-PDMS,
n ¼ number of repeat units.
Solubility of Si-PES.
Samples
DMAc DMSO DMF THF Chloroform Acetone Methanol
Series assigned structures
[M þ ion](Da)
0% DDSQSi-PES
5% DDSQSi-PES
10% DDSQSi-PES þꢁ
20% DDSQSi-PES þꢁ
50% DDSQSi-PES þꢁ
100% DDSQSi-PES þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
þꢁ
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
238(M1)þ74nþ223(M2)þ
23(Na) ¼ 484 þ 74n
238(M1)þ74nþ223(M2)þ
39(K) ¼ 500 þ 74n
Solubility under a mass of liquid: 0.1 g/mL; (þ) soluble at room temperature; (ꢁ)
insoluble even on heating; (þꢁ) partially soluble or swelling on heating.

82
J. Xu et al. / Polymer 62 (2015) 77e85
Fig. 6. Solid-state 29Si NMR spectrum of Si-PES.
PES (CA ¼ 80.5ꢀ). The static surface CAs of 50%DDSQSi-PES was as
high as 113ꢀ, showing that the hydrophobicity of the copolymer
was significantly enhanced. The water CAs initially increased with
the increase in large molecular weight monomer DDSQ content,
whereas the molar ration of hydrophilic O]S]O and ether groups
rapidly decreased (Fig. 9). During this process, the silicone content
was also decreasing, which led to the secondly decrease in 50%
DDSQ molar ratio. The CA value (>90ꢀ) indicated that the materials
had hydrophobic properties. This suggested that the surfaces of
organic-inorganic copolymers were saturated by organosilicon
moieties (viz. POSSs) and might have potential applications in hy-
drophobic materials. The solubility of Si-PES copolymers is shown
in Table 3. With the introduction of nanoscale POSSs into the main
chain of polymers, improvement in solvent resistance was
obtained.
Fig. 4. IR spectra of (a) 0% DDSQSi-PES, (b) 10% DDSQSi-PES, (c) 30%DDSQSi-PES, (d)
50% DDSQSi-PES, and (e) 100%DDSQSi-PES.
3.4. Surface properties and solubility of Si-PES copolymers
The wettability of the resulting surface was evaluated using
water CA measurements as shown in Fig. 9. The water droplet on a
highly hydrophobic surface displayed a higher CA because it has a
lower surface energy against the surface tension of water as probe
liquids. The incorporation of hydrophobic silicone into the polymer
lowers the surface energy and eventually lowers wettability. In this
work, synthesized Si-PES provided a higher CA than that of pure
Fig. 5. 1H NMR spectra of (a) 0%DDSQSi-PES, (b) 5%DDSQSi-PES, (c) 10%DDSQSi-PES, (d) 20%DDSQSi-PES, and (e) 30%DDSQSi-PES copolymer in DMSO-d6.

Fig. 7. TGA curves of non-POSS-Si-PES and the POSS-containing Si-PES copolymers.
Fig. 8. WAXRD profiles of (a) 0%DDSQSi-PES, (b) 5%DDSQSi-PES, (c) 10%DDSQSi-PES,
(d) 30%DDSQSi-PES, (e) 50%DDSQSi-PES, and (f) 100%DDSQSi-PES hybrids membranes.
Fig. 10. (a) Frequency dependence of ks of DDSQSi-PES hybrid films; (b) plot of ks at
1 MHz as a function of the content of POSS and PDMS in the organic-inorganic co-
polymers; (c) frequency dependence of dielectric loss of DDSQSi-PES hybrid films.
3.5. Dielectric constant (k) of Si-PES copolymer hybrid films
Low dielectric property is an important factor for a material to
be used in microelectronics. It overcomes increasing signal delay
and energy loss with IC miniaturization [42]. The
k value of the
copolymer hybrid films tested at frequency ranging from 1000 Hz
to 1 MHz is shown in Fig. 10 (a). Meanwhile, Fig. 10 (b) summarizes
the variation of their
Based on the curves, the
k
along with the contents of POSSs at 1 MHz.
of 0%DDSQSi-PES is as low as 2.73. It
k
relies on the number of non-polar and highly flexible PDMS in the
main chain. The interatomic distances of PDMS were as large as the
spiral arrangement of molecular chains, and it led to a lower
Fig. 9. Plot of surface water CAs as a function of the ratio of DDSQ in organiceinorganic
copolymers.

84
J. Xu et al. / Polymer 62 (2015) 77e85
Fig. 11. SEM images showing morphology of Si-PES composites: (a) 0%DDSQSi-PES, (b) 3%DDSQSi-PES, (c) 5%DDSQSi-PES, (d) 7%DDSQSi-PES, (e) 10%DDSQSi-PES, (f) 30%DDSQSi-
PES, (g) 50%DDSQSi-PES, and (h) 100%DDSQSi-PES.
polymer density, as well as a low
k
. High dielectric permittivity
fluorophenyl sulfone, and series of dihydroxy terminated euge-
nosiloxanes (2OH-PDMS-n) with flexible chain length using one-
step high temperature solution method. These Si-PES co-
polymers showed excellent chemical resistance to common
organic solvents, high thermal stability, good chain regularity, and
outstanding hydrophobic properties. DSC and TGA indicated that
the stability of copolymers significantly improved. The co-
polymers possessed high glass transition temperatures and
decomposition temperatures with the increase in POSS content.
Synergies between the two components affect the performance.
The decrease in hydrophobic property value was due to the silicon
content when organosiloxane in the main chain was low. The
increasing trend was due to the decreasing hydrophilic group as
change trends from 0%DDSQSi-PES to 100%DDSQSi-PES resulted
from the remarkable interfacial polarization between POSS and
organic particles. Because of the immiscibility between organic
chains and POSS portion, POSS blocks could be self-assembled into
microdomains, which could display a similar diffraction profile as
POSS as shown in Fig. 8,
k initially increased and then decreased in
the specter from 5% DDSQ content to 10% DDSQ content and 10%
DDSQ content to 100% DDSQ content without linear organo-
siloxane. And scanning electron microscopy (SEM) is an intuitive
and convenient method to observe the microstructure of the hybrid
films. Fig. 11 shows the SEM photographs of the fracture surfaces of
silicon-containing PES hybrid films. From Fig. 11ceh, it could be
seen that the POSS clusters had been well coated and homoge-
neously distributed in the silicon-containing PES polymer matrix
and the size of the visible particles achieved nanoscaled dispersion.
In Fig. 11aeb, the smaller cluster distribution shows the compati-
bility of linear organosiloxane was obvious [43]. The increase may
be caused by interfacial polarization and to a certain extent, clusters
has fewer interface, which led to a decreasing trend of change from
10% DDSQ content to 100% DDSQ content [40]. A similar trend in
shown on Fig. 10 from 5%DDSQSi-PES (2.36, 1 MHz) to 10%DDSQSi-
PES (3.1, 1 MHz) and 10%DDSQSi-PES to 100%DDSQSi-PES (2.68,
1 MHz). Besides, the change from 0%DDSQSi-PES (2.73, 1 MHz) to
5%DDSQSi-PES (2.36, 1 MHz) was not a definite attribute for the
improved performance of interface between DDSQ and organic
phases because the compatible linear organosiloxane exist. With
the decrease in DDSQ content, the compatibility was more obvious.
From the SEM Fig. 11c of 5%DDSQ-PES, it could be seen that the
POSS had been well coated and homogeneously distributed in the
silicon-containing PES polymer matrix and the size of the visible
particles achieved nanoscaled dispersion. The introduction of
vacant cage-like structure of the POSS macromer into the main
chains of copolymers simultaneously resulted in the increase in the
ether bond and sulfone dominated. Meanwhile, in hybrid films,
k
was affected by the combined effects of interfacial polarization
and clusters of POSS in the main chain. When POSS content in the
main chain was low, the linear organosiloxane as compatibilizer
reduced interfacial polarization. Meanwhile, when the POSS con-
tent was very high, the number of clusters in the copolymer was
decreased. The incorporation of cage and linear organosiloxane
coexist structure resulted in excellent dielectric and hydrophobic
properties of PES, which paved way to the development of a new
synthetic approach in preparing wave-transparent materials with
comprehensive performance [44].
Acknowledgments
The authors gratefully acknowledge the financial support from
the International Science and Technology Cooperation program of
China (2012DFR50300).
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