Materials Sciences and Applications, 2012, 3, 72-77
http://dx.doi.org/10.4236/msa.2012.32011 Published Online February 2012 (http://www.SciRP.org/journal/msa)
Structure Change of Polyethersulfone Hollow Fiber
Membrane Modified with Pluronic F127,
Polyvinylpyrrolidone, and Tetronic 1307
Nasrul Arahman1*, Bastian Arifin1, Sri Mulyati1,2, Yoshikage Ohmukai2, Hideto Matsuyama2
1Department of Chemical Engineering, Syiah Kuala University, Banda Aceh, Indonesia; 2Department of Chemical Science and Engi-
neering, Kobe University, Kobe, Japan.
Received October 9th, 2011; revised January 21st, 2012; accepted February 5th, 2012
ABSTRACT
Hydrophilic polyethersulfone (PES) hollow fiber membranes were prepared via non-solvent induced phase separation
(NIPS) by addition of polymeric additives as a membrane modifying agent. The effect of the addition of hydrophilic
surfactant Pluronic F127, Polyivinylpyrrolidone (PVP), and Tetronic 1307 on the performance of the final PES hol-
low-fiber membrane was investigated. The morphology of fabricated hollow fiber membrane observed by scanning
electron microscopy (SEM) indicated that all of membrane had a skin layer on the surface and finger like macrovoid
structure inside the hollow fiber. The addition of 5 wt% polymeric surfactant on the polymer solution results in mem-
brane with improved length and number of macrovoid structure. Sponge formation both near inner surface and near
outer surface of hollow fiber membrane was another impact of addition of polymeric additives, which is led to de-
crease of water permeability of these membrane. Water contact angle measurement was performed to investigate the hy-
drophilicity property of resulted membrane. It is confirmed that the modified PES hollow fiber membranes had lower
water contact angle than that of the original membrane, which indicate that the modified PES membrane with additives
has high hydrophilic.
Keywords: Membrane Preparation; Polyethersulfone; Tetronic 1307; Pluronic F127; Polyivinylpyrrolidone
1. Introduction
Ultrafiltration (UF) as a novel separation technology has
been widely applied in water purification process for the
removal of particles, turbidity, microorganism, and natu-
ral organic matter (NOM) from surface water and ground-
water [1-3]. These method offers several advantages such
as consistent high quality of water, capable of removing
a wide range of substances, and fewer addition of che-
micals to raw water in treatment process [2,4]. The UF
technology was established with large plants installed
worldwide since 1980 [5]. This membrane rapidly expan-
ding due to the need for purifying drinking water. The
researchers are now developing high performance of UF
membrane module for drinking water treatment. Mem-
branes were fabricated and modified with various meth-
ods [6-8]. The purpose is to obtain high performance of
UF membrane with high flux, high rejection, high foul-
ing resistance, good chemical resistant and mechanical
stability.
Porous polymeric membrane can be fabricated by se-
veral methods, including sintering, stretching, track et-
ching, and phase separation processes [9]. The obtained
membrane structures and properties can be controlled ba-
sed on material properties and the preparation condition.
Most of commercially available membranes are prepared
by phase separation method which can be induced in four
main techniques for the preparation of polymeric mem-
branes [10]. Those are methods of thermally induced
phase separation (TIPS), air-casting of the polymer solu-
tion, precipitation from vapor phase, and non-solvent
induced phase separation (NIPS) or immersion precipita-
tion. This paper mainly focuses on preparation and modi-
fication of poly(ether sulfone) hollow fiber membrane
via NIPS process. In the membrane preparation process
via NIPS, a polymer is dissolved in the solvent at room
temperature, and homogeneous polymer solution is casted
on a support or is extruded through a spinneret and sub-
sequently immersed in a non-solvent coagulant bath to
solidify the membrane. Phase separation occurs due to
the inflow of non-solvent to the casting solution [11-13].
The separation performance depends on properties of the
resulted membrane, such as degree of hydrophilicity, pore
*Corresponding author.

Structure Change of Polyethersulfone Hollow Fiber Membrane Modified with Pluronic F127,
Polyvinylpyrrolidone, and Tetronic 1307
73
size and pore distribution, surface charge, and membrane
thickness. The hydrophilicity, porosity, and skin layer thick-
ness of membrane can be modified by addition of additive
to the casting solution such as polyvinyl pyrrolidone (PVP),
polyethylene glycol (PEG), Pluronic, etc. This method is
known as a membrane modification process. In general, the
objectives for modification of membrane morphology is to
improve fouling resistance. Thus, the membrane life time
can be longer than unmodified membrane.
Modification of polyethersulfone membrane morpho-
logy by addition of PVP at various molecular weight and
concentration has been investigated intensively [14-16].
Addition of PVP into PES-DMF (dimethylformamide) con-
tributes to increasing of membrane hydrophilicity. Thus, this
additive could act as fouling preventing agent [14]. Increas-
ing of permeability without significant change in selectivity
by addition of small quantities of PVP was also observed by
Ochoa, N.A and co-workers [15]. The research group of
Wang succeeded in making a hydrophilic PES flat mem-
brane by adding surfactant Pluronic F127 into the polymer
solution [18-20]. The presence of Pluronic F127 in blend
membrane could improve fouling resistance of the resulting
membrane. In our previous study [21], surfactant Tetronic
1307 was used as a membrane modifying agent in order to
improve the membrane performance. The permeability de-
cline of the PES blend membrane with Tetronic 1307 in
BSA filtration was lower than that of the original PES
membrane because of its greater hydrophilicity. In the pre-
sent study, the Pluronic F127, PVP, and Tetronic 1307 were
used as membrane modifying agent to produce high per-
formance of PES hollow fiber membrane. The effects of
those additives on the performance, characteristics, and
fouling property of the fabricated membranes are system-
atically compared.
2. Experimental
2.1. Material
PES (Ultrason E6020 P) with Mw 65,000 was purchased
from BASF Co. N-Methyl-2-Pyrrolidone (NMP) was ob-
tained from WAKO (Pure Chemical Industries, Ltd, Ja-
pan). Surfactant Tetronic 1307, and Pluronic F127 were
purchased from BASF Co. Polyvinil pyrrolidone (PVP
K30), was purchased from SIGMA (Germany). Dextran
with molecular weight of 77,000 obtained from SIGMA
ALDRICH (Germany) was used as agent for solute rejec-
tion investigation. All such chemicals were used with-
out further purification. The water used was high-quality
deionized water (DI water, >15 MΩ·cm−1) produced by
an Elix-5 system (Millipore).
2.2. Preparation of Hollow Fiber Membrane
Hollow fiber membrane was prepared via non-solvent in-
duced phase separation (NIPS) by a batch-extruder using
a similar method applied in our previous work [22]. Do-
pe solutions were prepared by dissolved 20 wt% of PES
and 5 wt% of additives in NMP (Ta ble 1). The homoge-
nous polymer solution were obtained by stirring the solu-
tion at 300 rpm for 24 hours. The dope solutions were
left in the reservoir for 4 hour to allow complete release
of bubbles.
All of membrane preparation conditions were mainta-
ined to be similar, as shown in Tab le 2. The hollow fiber
was extruded from the spinneret and wound on a take-up
winder after entering into the coagulation batch to induce
phase separation, and solidify the membrane. The poly-
mer flow rate through spinneret was controlled by a gear
pump. Water as inner coagulation media was flow into
inner tube to make lumen of the hollow fiber. The prepa-
red hollow fiber membranes were kept in the pure water
before testing.
2.3. Membrane Morphology
Membrane morphologies (surface and cross section) were
observed by a Scanning Electron Microscope (SEM, Hi-
tachi Co., JSM-5610LVS, Japan) with an accelerating
voltage of 15 kV. The hollow fiber membranes were free-
ze-dried using a freeze dryer (EYELA, FD-1000, Japan)
at temperature of –40˚C for 24 hours. For cross section
observation, the freeze-dried membranes was fractured in
liquid nitrogen.
Table 1. Dope polymer composition.
Membrane PES (wt%)NMP (wt%) Additives (wt%)
1
2
3
4
20
20
20
20
80
75
75
75
-
Pluronic F127 (5)
PVPK30 (5)
Tetronic 1307 (5)
Table 2. Preparation condition of PES hollow fiber mem-
brane.
Spinneret dimension (mm) OD/ID = 1.00/0.70
Polymer flow rate (m/min)
Inner coagulant
Inner coagulant flow rate (m/min)
Take-up speed winder (m/min)
Air gap distance (cm)
Bath composition
Temperature (˚C)
3.10
Water
13.0
13.6
10.0
100% water
25

Structure Change of Polyethersulfone Hollow Fiber Membrane Modified with Pluronic F127,
Polyvinylpyrrolidone, and Tetronic 1307
74
2.4. Membrane Hydrophilicity
The hydrophilicity properties of the hollow fiber mem-
brane were observed by measuring water contact angle of
the outer surface of membrane at room temperature by a
contact angle meter (Kyowa Interface Science Co., Drop
Master 3000, Japan). A 0.5 μl of de-ionized water was
dropped on the outer surface of hollow fiber membrane
using microsyringe with a stainless stel needle and the
contact angle was recorded automatically. Each sample
was randomly measured for 20 times and an average va-
lue was calculated as the contact angle of that membrane.
The time between the deposition of a droplet in the mem-
brane surface and the measurement of the contact angle
was kept as short as possible in order to avoid a change
of droplet volume due to water evaporation or absorp-
tion.
2.5. Water Permeability and Solute
Rejection Test
Both experiments were carried out by using a cross flow
filtration system. The schematic diagram of laboratory-
scale apparatus by using the single hollow fiber module
used for the experiments are shown in Figure 1. For wa-
ter permeability observation, deionized water was forced
to permeate from the inside to the outside of the hollow
fiber membrane by peristaltic pump. The transmembrane
pressure could be applied by adjusting the pressure valve
close to the release side, and the average of the readings
of the two pressure gauges of 0.05 MPa was taken as the
filtration pressure. The solute rejection experiment was
performed by using solution contained 1 wt% dextran
with molecular weight of 77,000. The solute rejection (R)
of membrane was obtained by measuring the concentra-
tion of dextran in feed and permeate by using UV spec-
trophotometer (GE-Healthcare) at 254 nm of wave length.
Rejection of dextran calculated by the following equation:

0
0
Rejection % =100
CC
C




where C0 and C are the concentration of humic acid in
feed and permeate, respectively.
The fluxes of deionized water and dextran solution was
collected every 10 minutes and calculated on the basis of
the inner surface area of the hollow fiber membrane.
3. Results and Discussion
3.1. Membrane Morphology
In order to understand the effect of membrane modifying
agent on the structures of the PES membrane, the cross-
section and surface structure of all fabricated membranes
were observed by SEM. Surface structures of PES mem-
brane with and without additives are shown in Figure 2.
It is shown that, all of membranes had porous structures
with rough surface. The structure change between PES ori-
ginal membrane and PES blend membrane was not so
clear because the pores were too small formed on the sur-
face.
Figure 3 shows the SEM image of whole cross-section
and enlarged cross-section of membrane prepared by PES/
NMP system and the membrane prepared by PES/NMP/
Pluronic F127, PES/NMP/PVP, and PES/NMP/Tetronic
1307 system. In all cases, fingerlike macrovoids were clear-
ly formed inside the hollow fiber membranes. Addition of
membrane modifying agent in the polymer solution brou-
ght about the increase of number and length of fingerlike
structure. Sponge area in the center path of hollow fiber
membrane prepared by PES/NMP system was also dis-
appear when the membrane modifying agent added. Fi-
gure 4 shows the structure of membrane near the inner
Figure 1. Schematic diagram of single hollow fiber mem-
brane module employed in fouling experime nt.
(a) PES (b) PES/F127
(c) PES/PVP (d) PES/T-1307
Figure 2. SEM images of the outer surface of PES hollow
fiber membrane with and without additive.

Structure Change of Polyethersulfone Hollow Fiber Membrane Modified with Pluronic F127,
Polyvinylpyrrolidone, and Tetronic 1307
75
(a) PES (b) PES/F127
(c) PES/PVP (d) PES/T-1307
Figure 3. Structure change of PES hollow fiber membrane observed by SEM. Left: whole cross-section; right: enlarged
cross-section.
(a) PES (b) PES/F127
(c) PES/PVP (d) PES/T-1307
Figure 4. SEM images of PES hollow fiber membranes with and without additive. Left: near inner surface; right: near outer
surface.
and the outer surface of all resulted membrane. An in-
creased of fingerlike structure was clearly observed by
addition of additive as membrane modifying agent. In the
membrane preparation via non-solvent induced phase se-
paration process, the addition of the third component in
the polymer solution brought about the decrease in the
non-solvent amount that is necessary to obtain phase se-
paration [22]. This means, the phase separation easily o-
ccurs by the addition of polymeric additive as a third com-
ponent in the dope solution, that results membrane with
enhanced growth of macrovoid inside the hollow fiber
membrane. On the other hand, addition of 5 wt% of Plu-
ronic F127, PVP, and Tetronic 1307 led to the forma-
tion of a sponge layer near the inner and outer surface, as
shown in Figures 4(b)-(d). The existence of hydrophilic
additives on the surface of PES hollow fiber membrane
may result in formation of sponge layer on the inner and
the outer surface of membrane.
3.2. Membrane Hydrophilicity
PES membranes have excellent chemical resistance, wide
range temperature in application, and desirable mechani-
cal strength. This polymer is widely used in membrane
preparation for various applications [23-25]. However,
their antifouling property is poor, which is the main dis-
advantage of this polymer in practical application. In this
work, hydrophilic polymer was added to the polymer so-

Structure Change of Polyethersulfone Hollow Fiber Membrane Modified with Pluronic F127,
Polyvinylpyrrolidone, and Tetronic 1307
76
lution in order to improve the hydrophilicity property of
PES membrane. Three types of polymeric additives were
blended to PES system. The hydrophilicty of blend mem-
brane was observed by water contact angle measurement.
The results are presented in Table 3. The original PES
membrane prepared from PES/NMP system showed the
higher water contact angle, which indicate the membrane
is hydrophobic. In all cases, water contact angle decreas-
ed when the polymeric surfactant added to the polymer
solution. This means, the membrane became more hydro-
philic.
3.3. Filtration Performances
Table 4 also lists the ultrafiltration performance of the
series of hollow fiber membrane. The water permeability
of PES original membrane is higher than that of the oth-
ers membrane blended with additives. Addition of 5 wt%
of polymeric additives into this polymer system lead to
the formation of sponge layer near both the inner and the
outer surface of PES hollow fiber membrane (Figure 3).
This is the reason for decreasing of water permeability of
PES/F127, PES/PVP, and PES/T1307 membranes. The
rejection of 1 wt% dextran (Average MW = 77.000) is
higher than 90% in all membrane system.
4. Conclusion
Polyethersulfone (PES) hollow fiber membrane was pre-
pared via non-solvent induced phase separation process,
and the effect of addition of three different polymeric
additives, i.e., pluronic F127, PVP, and Tetronic 1307 on
the characteristic and performances of fabricated mem-
branes was investigated. SEM investigation showed that
the increase macrovoid structure inside the hollow fiber
membrane by the addition of all polymeric additives. Spon-
ge formation both near inner surface and near outer sur-
face of hollow fiber membrane was the another impact of
addition of polymeric additives, which led to decrease of
water permeability of these membrane. The hydrophi-
licity of all modified membrane analyzed by water con-
Table 3. Hydrophilicity property of membrane observed by
water contact angle measurement.
Membrane System
Water
Contact Angle
(˚)
Water
Permeability
(L/m2·h·atm)
Solute
Rejection
(%)
PES
PES/F127
PES/PVP
PES/T-1307
71.6
63.2
60.85
61.75
88.65
72.15
66.72
20.80
92.60
93.99
94.43
96.80
tact angle was higher than that of the original PES mem-
brane, which indicate the additives are exist on the sur-
face of hollow fiber membrane.
5. Acknowledgements
We would like to thank the Directorate General of High-
er Education, The Ministery of National Education, Indo-
nesia for the financial support of this work.
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