Novel amphiphilic PEO-grafted cardo poly(aryl ether sulfone) copolymer: Synthesis, characterization and antifouling performance

Article abstract of DOI:10.1016/j.polymer.2015.09.024

A series of comb-like amphiphilic copolymers (PES-g-PEO) were synthesized through grafting poly(ethylene oxide) (PEO) to cardo poly(aryl ether sulfone) (PES-NH) backbone. By controlling the ratios of PEO and cardo poly(aryl ether sulfone), amphiphilic cop

Full text of DOI:10.1016/j.polymer.2015.09.024

Accepted Manuscript
Novel amphiphilic PEO-grafted cardo poly (aryl ether sulfone) copolymer: synthesis,
characterization and antifouling performance
Shuhua Hou, Jifu Zheng, Suobo Zhang, Shenghai Li
PII:
S0032-3861(15)30229-9
10.1016/j.polymer.2015.09.024
JPOL 18110
DOI:
Reference:
To appear in: Polymer
Received Date: 13 July 2015
Revised Date: 2 September 2015
Accepted Date: 9 September 2015
Please cite this article as: Hou S, Zheng J, Zhang S, Li S, Novel amphiphilic PEO-grafted cardo poly
(aryl ether sulfone) copolymer: synthesis, characterization and antifouling performance, Polymer (2015),
doi: 10.1016/j.polymer.2015.09.024.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Novel amphiphilic PEO-grafted cardo poly (aryl ether sulfone) copolymer: synthesis, characterization
and antifouling performance
Shuhua Hou, Jifu Zheng, Suobo Zhang*, Shenghai Li*
Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese
Academy of Science, Changchun 130022, China
∗
Corresponding author at: Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied
Chemistry, Chinese Academy of Sciences, Changchun 130022, China
(
86) 431-85262118, Fax: (86) 431-85685653.
E-mail address: lsh@ciac.ac.cn; sbzhang@ciac.ac.cn
Abstract: A series of comb-like amphiliphilic copolymers (PES-g-PEO) were synthesized through
grafting poly(ethyleneoxide) (PEO) to cardo poly(aryl ether sulfone) (PES-NH) backbone. By
controlling the ratios of PEO and cardo poly(aryl ether sulfone), amphiphilic copolymers with a range
of PEO side chain were obtained and were employed to ultrafiltration (UF) membranes. The
PES-g-PEO-XX materials showed high thermal stability (T >238 °C) and good mechanical properties
d
especially elongation at break reached to 150% compared to 23% of PES-NH. The contact angle of
o
o
PES-g-PEO-80 asymmetric membrane was decreased to a slow as 59 which was 30 lower than the
o
value of PES-NH membrane (90 ), indicating that PES-g-PEO-80 membrane exhibited remarkable
hydrophilic property. No protein adsorption was found on the surface of PES-g-PEO-60 and
PES-g-PEO-80 membranes, showing excellent antifouling properties compared to PES-NH. The results
of this work suggest that PES-g-PEO copolymers are promising materials for the fabrication of fouling
resistant membranes.
Keywords: PEO-grafted copolymers, membrane, Antifouling properties
1
.
Introduction
Polyethersulfone (PES) is one of the most favorable membrane materials in microfiltration (MF)
and ultrafiltration (UF) for water treatment, and also it is one of the few biomaterials that can withstand
all sterilization techniques as its excellent mechanical strength, suitable chemical resistance, good
thermal stability, etc[1-4]. Nevertheless, fouling and in particular biofouling is still an important issue
in the widespread implementation of PES membrane. The adsorption of serum proteins onto PES
membranes used in medical areas can cause serious or life-threatening disease. The inherent
hydrophobicity of PES membranes makes themselves easy to be fouled by biomacromolecules on
membrane surfaces and pore walls during the membrane separation process resulting in high-cost. It is
believed that the hydrophilic membranes are more resistant to fouling than hydrophobic
membranes[5-8]. Therefore, improving the hydrophilicity of PES membranes is of great interest, as
hydrophilic membranes can effectively reduce the interactions between the biological foulants and
membrane surfaces.

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In general, several methods including surface chemical grafting[9-14], surface coating[8, 15, 16]
and adding hydrophilic molecules[17, 18] have been widely used to increase the hydrophilcity of
membrane surface. However, many problems can arise with such surface modifications. Chemical
grafting is a difficult operation to control and detrimental to membranes, and the same is true for
surface coating using organic solvent in most cases. For adding hydrophilic molecules, hydrophilic
molecules will leach out slowly from the membranes surface due to their water soluble properties,
resulting in short-term effects. An alternative approach is the utilization of hydrophilic polymers for
fabrication of membranes[19], as hydrophilic materials can overcome the chemical process during the
membrane fabrication processes and can stay steadily during the membrane separation processes.
It has been shown that poly(ethyleneoxide) (PEO) chains are highly resistant to hydrophobic or
large molecules adsorption on membrane surfaces, as PEO is antifouling with the properties of
uncharged and hydrophilicity. As a result, PEO materials have been extensively used for the surface
modification of membranes in recent years for their remarkable antifouling properties[20-22]. However,
there are still some trouble in PEO materials for membrane fabrication, such as poor mechanical and
crystallinity properties. The use of PEO-grafted polymers is an especially convenient method to
enhance the mechanical strength and minimize the crystalline regions in PEO[23, 24]. In our previous
study, a series of cardo poly(aryl ether sulfone) materials have been synthesized[7, 24-28]. Grafting
function group to cardo poly(aryl ether sulfone) is an especially convenient method to attain PES
copolymers. Amphiphilic poly(ethylene oxide)-grafted cardo poly(aryl ether sulfone) copolymers were
obtained by first grafting 1,2-epoxypropane group to cardo poly(aryl ether sulfone), and then by the
reaction of glycidyl groups with methanamine-terminated poly(ethylene oxide)-methoxy
(
MeO-PEO-NHCH ), showing improved hydrophilicity of the membranes[24]. However, the route of
3
synthesis the copolymers which involved two grafting process to cardo poly(aryl ether sulfone) is hard
to control, thus it is not suitable for prepare membrane materials.
In view of what has been previously outlined, we successfully synthesized a series of novel
comb-like amphiphilic copolymers (PES-g-PEO) consisting of branch-like functional chains of
poly(ethyleneoxide) (PEO) and cardo poly(aryl ether sulfone)(PES-NH)-based root-like hydrophobic
chains. PES-g-PEO copolymers were obtained by one-step reaction between cardo poly(aryl ether
sulfone) and tosylated poly (ethylene glycol)-methoxy as shown in Fig. 1. The properties of the
PEO-grafted polymers were studied, such as the solubility, thermal stability and mechanical properties.
Asymmetric membranes were successfully prepared using these different grafted PES-g-PEO
copolymers. Interestingly, the PES-g-PEO membrane showed dramatically hydrophilicity compared to
PES-NH. The antifouling performances of the membranes were determined using bovine serum
albumin (BSA) as a model protein. It was worth to note that PES-g-PEO membranes exhibited
excellent antifouling property.
2
.
Experimental
.1 Materials
Phenolphthalein (PPH) was purchased from Beijing Chemical Reagent Company, and purified by
2
recrystallization from mixed solvent of ethanol and water. 4, 4-Difluorodiphenyl sulfone (DFDPS) was
purchased from Aldrich. Methoxy-terminated poly(ethylene oxide) (M=350) were purchased from

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Aladdin and used as received. N-Methylpyrrolidinone (NMP) was firstly dried with CaH and then
2
distilled under reduced pressure before use. Anhydrous potassium carbonate was finely powdered prior
to use. Bovine serum albumin (BSA, pI = 4.8, Mw= 67 kDa) was purchased from Sino-American
Biotechnology Co., Ltd. All other chemicals were reagent grade and used as received.
2
.2 Synthesis and characterization of PES-g-PEO
Fig. 1 Synthesis of tosylated poly (ethylene glycol)-methoxy and PES-g-PEO
.2.1 Synthesis of 3, 3-bis (4-hydroxyphenyl)isoindolin-1-one (PPH-NH)
The monomer PPH-NH was prepared according to the method of Wang et al[29].
.2.2 Synthesis of tosylated poly (ethylene glycol)-methoxy
2
2
A
500 mL three-necked round bottom flask was charged with
a
solution of
PEO(CH (OCH CH ) OH, 70 g, 0.20 mol) in 60 mL of tetrahydrofuran. Upon vigorous stirring at 0°C,
3
2
2 7
sodium hydroxide (16 g, 0.40mol) dissolved in 60 mL of water was added. To this mixture, a solution
of tosyl chloride (50 g, 0.27mol) in 80 mL of dry tetrahydrofuran was added dropwise over 1 h at 0°C.
The reaction mixture was allowed to warm to room temperature and stirred for 16 h. Subsequently, 300
mL of dichloromethane was added and the organic layer was separated and washed with 1 M aqueous
NaOH (3 x 50 mL). Again, the organic layer was washed with water (2 x 50 mL), dried over MgSO4,
1
followed by evaporation and drying in vacuo, to yield the title compound as a colorless liquid. H NMR
(
(
CDCl , 500 MHz), δ (ppm): 7.82 (d, J=7.3 Hz, 2H), 7.4 (d, J=7.3 Hz, 2H), 4.13 (t, J=4.5 Hz, 2H), 3.6
3
m, 26H), 3.25 (s, 3H), 2.4 (s, 3H).
2
.2.3 Synthesis of cardo poly(aryl ether sulfone)s (PES-NH)
To a 1000 mL three-necked round bottom flask equipped with mechanical stirrer and N inlet,
2
PPH-NH (38.05g, 0.12 mol), DFDPS (30.51g, 0.12 mol), anhydrous K CO (41.16 g, 0.3 mol), 340 mL
2
3
NMP and 170 mL cyclohexane were added. The reaction mixture was heated with stirring at 120 °C for
h. After the cyclohexane and water had been removed by azeotropic distillation, the temperature was
4
raised to 145 °C and allowed to react at this temperature for 8 h. The system was cooled to room
temperature and diluted with NMP. The solution was filtrated to remove inorganic salts. The filtrate
was poured into water to give white flake of the product, which was washed with hot water several
times and extracted with ethanol. The resulting product was dried under vacuum at 120 °C for 24 h.

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1
The yield was 97%. H NMR (DMSO-d , 300 MHz), δ(ppm): 9.80 (s, 1H), 7.87 (m, 4H), 7.78-7.56 (m,
6
4
2
H), 7.07-7.10 (m, 8 H).
.2.4 Synthesis of cardo poly(aryl ether sulfone)s with poly (ethylene oxide) group (PES-g-PEO-XX)
The PEO grafted cardo poly(aryl ether sulfone)s are denoted as PES-g-PEO-XX, where XX
represents the molar percent of PEO groups. A typical synthetic procedure for PES-g-PEO-60 is
illustrated as follows. PES-NH (8.0 g, 0.015 mol) and NaH (0.43 g, 0.018 mol) were added to 80 mL of
DMAc at room temperature and stirred for 30 min. Then tosylated poly (ethylene glycol)-methoxy (4.5
g, 0.009 mol) was added and the reaction was allowed to proceed at room temperature for 24 h. The
viscous solution was precipitated into deionized (DI) water. The polymer was separated by filtration
and dried in a vacuum oven at 100 °C for 24 h.
2
2
.3 Membrane preparation
.3.1 Dense membranes
In a typical dense membrane preparation process, the polymer was dissolved in DMAc to form a
0.0 wt% solution. After filtrated and degassed, the solution was cast onto a clean glass substrate, and
1
the solvent was evaporated over 24 h at 60°C. The as-cast membrane was dried further under vacuum
for 24 h at 120 °C. Then the membrane was immersed into deionized water and peeled off. Finally, the
resulting dense membrane was dried for another 24 h at 120 °C under vacumm. The as-made dense
membrane was used to tensile measurements.
2
.3.2 Asymmetric membranes for antifouling performance
Asymmetric membranes were prepared by the well-known phase inversion process. The dope
solutions with polymer concentration of 18.0 wt% in DMAc were cast onto clean glass plates using a
casting knife with a 150 ꢀm gate gape, and the glass plates were then immersed immediately into a
coagulation bath of deionized water. The film samples were kept in deionized water prior to testing.
2
.4 Measurements
1
H NMR was recorded on Varian Unity spectrometer at 300 MHz with tetramethylsilane (TMS) as
the internal standard and DMSO-d /CDCl as the solvent, respectively. Inherent viscosities of all
6
3
polymers were determined at 30 ± 0.1 °C using Ubbelodhe viscometer with 0.5 dL/g concentration in
DMAc. Attenuated total reflectance infrared (ATR-IR) characterization was made with a Bio-Rad
digilab Division Fst-80 spectrometer. The thermogravimetric analyses (TGA) were obtained in nitrogen
with a Perkin Elmer TGA-2 thermogravimetric analyzer (Inspiratech 2000 Ltd., UK) at a heating rate
of 10 °C/min. All the samples were first vacuum-dried and kept in the TGA furnace at 150 °C in a
nitrogen atmosphere for 30 min to remove water before TGA characterization. Thermal behaviors of
PEO-grafted cardo poly (aryl ether sulfone) copolymers were evaluated by differential scanning
calorimetry (DSC) (TA Instruments DSC Q20 USA) at a heating rate of 10 °C/min under N2
atmosphere. Tensile measurements were performed with a mechanical tester Instron-1211 instrument
(
Instron Co., USA) at a speed of 2 mm/min at ambient humidity.
2
.5 Water contact angles
The static contact angle measurements were carried out to evaluate the hydrophilicity of the
membranes by a contact angle goniometer (JC2000C Contact angle Meter, Powerach Co., Shanghai,
China). Distilled water was dropped onto the surface of the membrane samples, and the contact angles

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of the drops were measured at several spots on the same membrane piece for at least three pieces of
each membrane at room temperature. Finally, the average contact angle was calculated.
2
.6 Protein fouling test
FITC-labeled BSA (BSA-FITC) was prepared according to reported method[30]. Asymmetric
membranes (1 cm × 1 cm) were washed three times with PBS (phosphate buffer saline) solution, and
then immersed in 1 mL 1 mg/mL FITC-BSA PBS solution at room temperature for 4 h to allow protein
surface adsorption. After the protein incubation, the membranes were then rinsed gently with PBS
buffer to remove any loosely bound surface BSA. Finally, membrane surface fluorescence was
visualized using Leica TCS SP2 Confocal fluorescence microscopy.
2
.7 Ultrafiltration experiments
Ultrafiltration membranes were tested using a cross flow filtration cell, and the effective area of
2
the membranes was 23.7 cm . At first, each membrane was compacted at 0.2 MPa for 1 h. Then the
operation pressure was lowered to 0.1 MPa. After compacted, deionized water was passed through the
2
ultrafiltration membranes for 0.5 h to obtain the beginning pure water flux J (L/(m h)), which was
1
calculated by the following equation:
V
(1)
=
1
J
A∆t
2
Where V was the volume of permeated water (L), A was membrane area (m ) and ∆t was
permeation time (h).
The rejections of BSA were calculated according to the feed and the permeate concentration via
UV spectrophotometer at 280 nm according to the following equation:



c
c
p
f

(2)
R = 1−
×100%




Where C and C (mg/mL) refer to the concentration of BSA in permeate and feed solutions
p
f
respectively.
3
.
Result and discussion
3
.1 Synthesis of amphiphilic polymer
In our former work, a series poly(ethylene oxide)-grafted cardo poly (aryl ether sulfone)
copolymers were synthesized through multiple-step process. First, epoxide group was introduced to the
cardo poly(aryl ethyl sulfone), and then methylamine-terminated monomer (MeO-PEO-NHCH3)
obtained through two-step process was grafted to the epoxide-grafted cardo poly(aryl ethyl sulfone).
This proposal is not suitable to prepare the membrane materials due to it was laborious and difficult to
control the two grafting processes. In this work, poly(ethylene oxide)-grafted cardo poly (aryl ether
sulfone) copolymers were synthesized via the reaction of amide group with tosylated poly(ethylene
glycol)-methoxy which are more active than mesylated poly(ethylene glycol)-methoxy. Synthesis of
tosylated poly (ethylene glycol)-methoxy was accomplished using tosyl chloride (1.3 eq) and NaOH as
1
the base in a yield of 90%. Fig. 2 shows the hydrogen signal assignment in the H NMR spectra of
MeO-PEO-OH and tosylated poly(ethylene glycol)-methoxy. The -OH peak at 2.9 ppm disappeared,
and three typical peaks of tosylate group were observed at δ 2.4 ppm, 7.4 ppm and 7.8 ppm. The peak
of -CH - near the tosylate group moved to 4.1 ppm from 3.6 ppm, indicating the successful synthesis of
2

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tosylated poly(ethylene glycol)-methoxy.
1
Fig. 2 H NMR spectra of MeO-PEO-OH, and tosylated poly (ethylene glycol)-methoxy in CDCl3
The cardo poly(aryl ether sulfone) (PES-NH) copolymer containing amide groups was synthesized
using PPH-NH and DFDPS. Different graft ratio PES-g-PEO-XX copolymers were obtained by
treatment of PES-NH copolymer with NaH in NMP in the presence of tosylated poly (ethylene
glycol)-methoxy. The mole ratios of amide groups to tosylated poly(ethylene glycol)-methoxywere set
to 1:0.2, 1:0.4, 1:0.6, 1:0.8 respectively. The chemical structure of the amphiphilic copolymers
1
PES-g-PEO-XX were analyzed by H NMR as shown in Fig. 3. The chemical shifts at δ=3.01 ppm,
δ=3.32 and δ=3.63 could be assigned to -N-CH -, -O-CH and -O-CH - of PEO respectively. The peaks
2
3
2
observed at δ=6.99 and δ=7.02 were assigned to the protons ortho to the diphenyl ether unit. The unit
number (XX) of PEO in PES-g-PEO-XX was calculated using the equation:
XX= [Iδ=3.01 /2]/[( Iδ=6.99+ Iδ=7.02) / 8]
Where Iδ=3.01, Iδ=6.99 and Iδ=7.02 are proton peak intensities of -N-CH - , protons ortho to phenolic
2
bridge, respectively. The value of XX is 78.4% with the mole ratio of amide group to tosylated
poly(ethylene glycol)-methoxy was 1:2, which indicated that PEO is grafted to the PES backbone
successful. Table 1 shows the molecular weight, grafting degree, and inherent viscosity of each
polymer.

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1
Fig. 3 H NMR spectra of amphiphilic polymer PES-g-PEO in CDCl
3
Table 1. Molecular weight, grafting degree, viscosity of polymers
Polymer
Mn
Mw
Grafting
Viscosity
4
4
(
10 ) (10 )
degree(%) (dL/g)
0.53
PES-NH
5.9
13.0
14.5
15.9
17.8
20.1
PES-g-PEO-20 6.3
PES-g-PEO-40 6.6
PES-g-PEO-60 7.0
PES-g-PEO-80 7.2
18
33
52
78
0.58
0.62
0.67
0.72
In agreement with the NMR results, the ATR-IR spectra of PES-g-PEO-80 (Fig. 4) revealed a new
-1
vibrational band at 1105 cm , due to the C-O stretch of the PEO side chains. The new absorptions at
-1
1
372 and 1409 cm were the aliphatic C-H bends of the PEO. Other new absorptions at 2870 and 2925
-1
1
cm were assigned to the aliphatic C-H stretch of the PEO side chains. In conclusion, both H NMR
and ATR-IR spectra indicated that the PEO side chains were successfully grafted onto the poly(aryl
ether sulfone) backbone.
Fig. 4 ATR-IR spectra of the membranes

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3
.2 Physical and chemical properties
Solubility is very important for polymers, as it determines the applications of polymer materials.
The solubility properties of the copolymers were qualitatively tested in various organic solvents, and
the results are summarized in Table 2. None of the polymers were soluble in methanol or water. As
shown in Table 2, both PES-NH and PES-g-PEO-XX were soluble in polar aprotic solvents, such as
NMP, DMF and DMAc. However, PES-g-PEO-XX (XX≥60) showed significantly different solubility
properties compared with the PES-NH. PES-g-PEO-XX (XX≥60) copolymers were soluble well in low
boiling point solvents, such as tetrahydrofuran, CHCl , CH Cl , or acetone. The solubilities increased
3
2
2
in low boiling point solvent with the increased PEO amount. The good solubilities of PES-g-PEO-XX
polymers were attributed to the PEO side chains.
Table 2. Solubility of the polymer
Polymer
Acetone Tetrahydrofuran CHCl3 CH Cl2 NMP DMSO DMF DMAc
2
PES-NH
_
_
±
±
+
_
_
±
+
+
_
_
+
+
+
_
_
+
+
+
+
+
+
+
+
+
+
±
±
±
+
+
+
+
+
+
+
+
+
+
PES-g-PEO-20
PES-g-PEO-40
PES-g-PEO-60
PES-g-PEO-80
_
The tests were performed at concentration of 0.05 g/mL (+) soluble; (±) partially soluble; ( )
insoluble
The thermal properties of the PES-NH and PES-g-PEO-XX copolymers are shown in Fig. 5.
PES-NH exhibited a single decomposition event and the starting decomposition temperatures of 498 °C,
corresponding to the decomposition of the polymer backbone. Two major steps of degradation were
found in PES-g-PEO-XX copolymers. The first decomposition starts at 238 °C, corresponding to the
cleavage of PEO side chains. The second decomposition stage was observed at 450 °C and was
assigned to the degradation of the main chains.
Fig. 5 TGA traces of PES-NH and PES-g-PEO-XX recorded under a nitrogen atmosphere.
The mechanical properties of the PES-NH and PES-g-PEO-XX membranes were measured as
shown in Table 3. The PES-NH membrane yielded a tensile strength at 48.6 MPa, Young’s modulus of
1
677 MPa, and elongation at break of 23%. After introducing the flexible PEO side chains, the tensile

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strength, Young’s modulus, and elongation at break of the PES-g-PEO-XX membranes ranged over
2
2-43 MPa, 1480-794 MPa, and 50-150%, respectively, which indicated that the materials possessed
sufficient strength for membrane application. With the increasing PEO amount, the tensile and the
modulus of the membranes decreased and the elongation at break increased, indicating that the
mechanical properties could be controlled by grafting different amount of PEO. The glass transition
temperature (Tg) of the graft polymers were also measured using DSC. The Tg value of the PES-NH
was 294 °C. After grafting the flexible PEO side chain, the Tg value of PES-g-PEO-80 decreased to
1
73 °C (Table 3), indicating the increase in chain mobility of grafted polymers.
Table 3. Mechanical properties and Tg values of the PES-NH and PES-g-PEO-XX dense membranes in
the dry state
Polymers
Tensile
Young’s
modulus
Elongation
Tg (°C)
strength (MPa)
at break (%)
(
MPa)
PES-NH
48.6
43.2
37.5
30.8
22.5
1677
1480
1266
1038
794
23
50
294
232
190
178
173
PES-g-PEO-20
PES-g-PEO-40
PES-g-PEO-60
PES-g-PEO-80
83
115
150
Hydrophilicity of membrane surface has an effect on membrane fouling and other vital properties.
Water contact angle measurement provided an effective approach to measure the hydrophilicity of a
membrane surface. Thus static water contact angle of asymmetric membranes was measured in order to
investigate the hydrophilicity of the surfaces and the results were shown in Fig. 6. It can be seen that
the contact angle of membranes decreased with the increasing the PEO amount. The contact angle of
o
PES-g-PEO-80 was decreased to as low as 59 which was lower than the value of PES-NH and other
o
o
o
reported membranes such as PSf (90.6 )[29], PES (89 )[30], PVDF(93.8 )[31], indicating that
membranes exhibited remarkable hydrophilic property. The decrease of the water contact angle can be
attributed to the increased surface coverage of hydrophilic PEO domains on the asymmetric membrane.
In a word, these results revealed that grafting PEO to PES-NH backbone could effectively enhance the
hydrophilicity of membranes.

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Fig. 6 The contact angles of (a) PES-NH, (b) PES-g-PEO-80, (c) PES-NH, and PES-g-PEO-XX.
.3 Protein antifouling
3
The biofouling formation onto the surface of a membrane is critical issue for most filtration
processes such as water treatments and membrane bioreactor applications. It is generally believed that
the non-specific, irreversible attachment of protein can cause the membrane fouling. To test the ability
of PES-g-PEO-XX membranes to resist protein fouling, a protein adsorption assay was carried out to
measure the nonfouling property of the membranes. PES-NH was used as controls in the assay. Bovine
serum albumin was used as a model to investigate the ability of protein adsorption on membrane
surface. All the membranes were briefly rinsed with PBS, and then soaked in 1 mg/mL Fluorescein
Isothiocyanate labeled bovine serum albumin (FITC-BSA) for 4 h. After the socking, membranes were
gently washed again with PBS to remove any loosely bound surface BSA. Finally, the pictures of five
membranes were taken under a fluorescent microscope with the same excitation light intensity and
exposure time. The images of accumulated BSA on the membrane surfaces are shown in Fig. 7. The
PES-NH membrane exhibited a high protein attachment after 4 h, which could be attributed to its
hydrophobic property. Significant quantitative decreases protein adsorptions were observed on
PES-g-PEO-XX membranes compared to the PES-NH membrane. There were no protein adsorptions
on membrane surface when the XX reached 60. The high protein antifouling performance of the
membranes was ascribed to its hydrophilic nature. In view of these results, it can be concluded that the
incorporation of PEO side chains to PES-NH backbone greatly improves the hydrophilicity and protein
fouling resistance of PES-NH, and therefore PES-g-PEO-XX are suitable for their intended purpose
such as processed as UF membranes.

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Fig. 7 Confocal microscopic images of FITC-BSA adsorption on the surfaces of the (a) PES-NH,
b) PES-g-PEO-20, (c) PES-g-PEO-40, (d) PES-g-PEO-60, (e) PES-g-PEO-80 membranes.
(
3
.4 Pure water permeation and BSA rejection
The rejections for BSA and the pure water flux of the asymmetric membranes with different PEO
content in PES-g-PEO-XX (0, 20, 40, 60) were plotted in Fig. 8. According to Fig. 8, it could be
concluded that PES-g-PEO-XX had a good performance on BSA rejection. It was also observed that
pure water flux increased as the content of PEO increased. The water flux of PES-g-PEO-60 was as
2
2
high as 338.6 L/m h compared to 98.5 L/m h of PES-NH, which was in agreement with the results of
water contact angle and surface hydrophilicity. All these results indicated that PES-g-PEO-XX
copolymers are promising materials for ultrafiltration membrane.
Fig. 8 Pure water flux and rejection for BSA of PES-NH and PES-g-PEO-XX membranes
4
.
Conclusion
In conclusion, a series of comb-like amphiliphilic copolymers (PES-g-PEO) were synthesized
using cardo poly(aryl ether sulfone) as hydropholic backbone and PEO as the hydrophilic side chains.

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By controlling the ratios of PEO and cardo poly(aryl ether sulfone), amphiphilic copolymers with a
range of PEO side chain were obtained. The graft copolymers showed excellent solubility, high thermal
stability and good mechanical properties. It is found that the hydrophilicity of PES-g-PEO-XX
membranes increased as the content of PEO increased. The contact angle of PES-g-PEO-80
o
o
asymmetric membrane was 30 lower than the value of PES-NH membrane (90 ), indicating that
membrane exhibited remarkable hydrophilic property. Furthermore, it is also found that protein
adsorption decreased dramatically with the increasing the content of PEO. No protein adsorption was
found on the surface of PES-g-PEO-60 and PES-g-PEO-80 membrane, indicating PES-g-PEO
membranes exhibited very good antifouling properties compared to PES-NH. The results of this work
indicated that PES-g-PEO copolymers are promising materials for the fabrication of fouling resistant
membranes.
5
.
Acknowledgments
We thank the National Basic Research Program of China (2015CB655302), the National Science
Foundation of China (No. 51473163, 51321062, 51133008). Chinese Academy of Sciences-Wego
Group High-tech Research & Development Program (ZKYWG2013-02), Science and Technology
Service Network Initiative (KFJ-EW-STS-047), and Scientific Development Program of Jilin Province
(
Project number: 20130204027GX).
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A series of novel comb-like amphiliphilic copolymers (PES-g-PEO) were synthesized.
The PES-g-PEO copolymers are promising materials to fabricate ultrafiltration membranes.
The PES-g-PEO membranes exhibited remarkable hydrophilic properties and antifouling
performances.