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KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded
Polylactide/Polyvinylpyrrolidone Blends
Bunthoeun Nim, Paiboon Sreearunothai and Pakorn Opaprakasit*
School of Bio-Chemical Engineering and Technology, Sirindhorn International Institute of Technology (SIIT),
Thammasat University, Pathum Thani, Thailand
Atitsa Petchsuk
National Metal and Materials Technology Center, Thailand Science Park, Pathum Thani, Thailand
* Corresponding author. E-mail: pakorn@siit.tu.ac.th DOI: 10.14416/j.ijast.2018.10.003
Received: 18 July 2017; Accepted: 21 August 2017; Published online: 4 October 2018
© 2019 King Mongkut’s University of Technology North Bangkok. All Rights Reserved.
Abstract
Nanofibers of polylactide (PLA)/polyvinylpyrrolidone (PVP) blends loaded with titanium dioxide (TiO2)
particles have been prepared by an electrospinning technique. TiO2 particles are formed by sol-gel mechanisms
from titanium (IV) iso-propoxide (TTIP) precursor. Effect of TiO2 formation rate on properties of the fibers are
examined by adding iso-propyl alcohol (iPOH) to slow down the TiO2 precipitation process. The use of iPOH
produces fiber mats consisting of slightly bigger and smoother filaments, but smaller-sized embedded TiO2
particles. Both materials show a distinct UV absorption characteristic of TiO2 at λmax 300 nm, which can be
applied in catalytic applications. Degradation behaviors of the materials in phosphate buffer solutions have also
been investigated. The materials have high potential for use as epoxidation catalysts for conversion of vegetable
oils to polymeric building blocks and plasticizers.
Keywords: Polylactide, Polyvinylpyrrolidone, Titanium dioxide, Electrospinning, Degradation
Research Article
Selected Paper from the 6th International Thai Institute of Chemical Engineering and Applied Science Conference (ITIChE2016)
1 Introduction
Polylactide (PLA) is one of widely used biodegradable
polymers, which can be synthesized from renewable
resources. This polymer is derived from lactic acid
monomers, commonly obtained from fermentation of
agricultural products, such as corn, rice, wheat, and
cassava starch [1]. PLA is recently applied in a wide
range of applications, including packaging [2], [3],
tissue engineering [4], scaffold engineering [5], wound
dressing, drug delivery, and anti-microbial materials
[6], due to its good mechanical properties, ease of
processibility, biodegradability [7], [8], biocompatibility
[9], and high transparency [10]. Therefore, the materials
is a promising alternate to non-degradable petroleum-
based plastics to solve serious plastic waste problems.
Polymer blends and composites have attracted vast
attention from the research community and industrial
sector to further improve properties of the materials
and expand their applications [11], [12]. Various blends
and composites of PLA have been developed and used
for many specific applications. Recently, composites
of PLA with titanium dioxide (TiO2) particles were
prepared and their properties and potentials were
examined. TiO2 nanoparticles possess a unique photo-
catalytic activity that can be applied in environmental
remediation, especially degradation of organic pollutants
and bacteria with high efficiency [13]–[15].
Major advantages of using TiO2 particles include
inexpensive cost, non-toxicity, high chemical stability,
Please cite this article in press as: B. Nim, P. Sreearunothai, P. Opaprakasit, and A. Petchsuk, “Preparation
and properties of electrospun fibers of titanium dioxide-loaded polylactide/polyvinylpyrrolidone blends,”
KMUTNB Int J Appl Sci Technol, vol. x, no. x, pp. x–x, (Year).
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B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
and high resistant to solvents. Various preparation
methods of TiO2 and PLA/TiO2 composites were reported,
such as in situ polymerization[16], electrospinning [6],
[17], [18], spin coating [19], [20], solution casting [9],
and a surface modified method [10]. In addition, several
PLA-based blends were used to prepare various
composites, including polyvinylpyrrolidone (PVP) [21],
polyethylene (PE) [22], polystyrene (PS) [23], and
poly(butylene succinate) (PBS) [24]. Among these,
PVP shows interesting properties, as it is water soluble,
with low toxicity and high physiological compatibility
[25]. This polymer is also considered as a conventional
polymer for safe use in pharmaceutical, cosmetic, and
food industries [26].
There are several reports of PVP carrier in an
electrospinning technique. The particles are embedded
to the polymer for various applications such as dye
degradation [15], [17], sensor [18], and bio-sensing [12].
Blends of PLA and PVP loaded with TiO2
nanoparticles (PLA/PVP/TiO2) are a promising
nanocomposite for use in improving PLA’s properties
and introducing specific catalytic activities. These
composites exhibited superior properties, compared
to their neat material counterparts, such as higher
Young’s modulus, improved thermal stability, higher
photo-degradability and biodegradability, and higher
gas barrier properties [27], [28]. Nanocomposite
fibers of PLA/TiO2/PVP/ZnCl2 were fabricated by an
electrospinning technique and used in wound dressing
applications [21].
In this work, TiO2-loaded PLA/PVP nanofibers
are fabricated by an electrospinning method. The loaded
TiO2 particles are formed by sol-gel mechanisms by
employing their precursor solution mixed with the
solutions of the polymer matrix during the electrospinning
process. Effects of TiO2 particles formation rate on
properties of the fibers are examined by adding isopropyl
alcohol. Morphology and properties of the resulting
fiber mats are investigated. The materials have high
potential for use as catalytic system. Their stability and
degradability are then examined in Phosphate Buffer
Solutions (PBS), under UVA light activator [29].
2 Methodology
2.1 Materials
Polylactide 4043D (PLA) was supplied by NatureWork®.
Polyvinylpyrrolidone (PVP) K29-32 (Mw=58,000 g/mol)
and Titanium (IV) Iso-propoxide, Ti(OiPr)4 (TTIP),
precursor (98+ %) were purchased from Acros.
Chloroform RPE (>99%), N,N-dimethyl formamide
(DMF) (99.8%), and isopropyl alcohol (99.7%) (iPOH)
solvents were purchased from Carlo Erba. Sodium
dihydrogen phosphate monohydrate (NaH2PO4;H2O)
and disodium hydrogen phosphate heptahydrate
(Na2HPO4;7H2O) were supplied by Carlo Erba and
PANREAC, respectively.
2.2 Preparation of PLA/PVP blends and TiO2-loaded
composites
PLA/PVP blends were prepared by mixing PLA (0.84 g)
with PVP at a ratio of 5:1 wt/wt, in chloroform (9 g),
and stirring until completely dissolved. The TiO2
precursor mixture was prepared from TTIP (200 μL),
mixed with DMF (3 g) and iPOH (1.5 g), followed by
adding of DI water (100 μL) drop wise. The mixture
was stirred at room temperature for 1 h. iPOH was used
to slow down the precipitation rate of TiO2 particles.
The polymer mixture was then mixed with the precursor
mixture and stirred at room temperature for 1 h to generate
suitable solutions for electrospinning. A summary of
the samples compositions and sample names is listed
in Table 1.
Table 1: Summary of sample compositions and sample
names
Samples PLA (g) PVP (g) TTIP (μL) iPOH (g)
P-P-T 0.84 0.168 200 0
P-P-I-T 0.84 0.168 200 1.5
2.3 Electrospinning
Fiber mats were fabricated by an electrospinning
technique. The composited mixture was placed in a
syringe (capacity of 3 mL) connected to a syringe-
stainless needle. The syringe was placed on a flow
controller (KD Scientific KD 100 Syringe Pump),
with a flow rate of 1 mL/h. The distance between the
collector and the needle tip was 15 cm. A voltage of
10 kV was applied by using a Gamma high voltage
(0–40 kV) power supply. The electrospun fibers were
gathered on an aluminum foil collector.
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KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
2.4 Characterization
Fourier Transform Infrared (FTIR) spectroscopy,
equipped with an Attenuated Total Reflectance (ATR)
accessory (Nicolet iS5 Spectrometer), was employed
to determine functional groups and interactions of the
electrospun fiber mats. Scanning electron microscopy
(SEM-SU8030) was used to investigate size and
surface morphology of the samples. Energy-dispersive
X-ray (EDX-SU8030) was employed to observe
surface compositions of each component. A UV-Vis
spectrophotometer (Genesys 10S) was used to examine
the absorption behaviors of the fiber mats.
2.5 Degradation experiments
Degradation behaviors of the fiber mats were examined
in phosphate buffer solutions (PBS at pH 7.4) at
ambient temperature. Neat PLA, P-P-T, and P-P-I-T
fiber mats were cut into 2×2 cm2. Each specimen
was immersed into 50 mL PBS and placed at a 22 cm
distance under UVA light (UVA 15WT8 lamp). The
experiments were conducted for 6 days, in which the
specimens were removed from the solution and washed
with DI water and dried at 40°C in a vacuum oven for
overnight. FTIR and UV-Vis spectroscopy were used
to examine the chemical structures of the samples as
a function of degradation time.
3 Results and Discussion
3.1 ATR-FTIR spectroscopy
ATR-FTIR spectra of spun fiber samples of neat
PLA, P-P-T, and P-P-I-T are shown in Figure 1. Band
characteristics of PLA and PVP are observed, indicating
the presence of the 2 components on a filament’s surface.
A strong band at 1753 cm–1 is assigned to the vibration
of C=O of PLA chains, whereas that at 1659 cm–1
corresponds to the amide (N-C=O) vibrational mode.
Both P-P-T and P-P-I-T show similar FTIR spectra
pattern. This reflects that the technique may not be
able to differentiate the nature of the two samples.
Nonetheless, a broad band centered at 3400 cm–1 (O-H
stretching), observed in these 2 samples but not in
neat PLA, indicates the presence of remaining iPOH
after the TiO2 particle formation, and also bound water
molecules due to the hygroscopic nature of PVP.
3.2 Scanning electron microscopy
Figure 2 shows surface morphology of P-P-T and
P-P-I-T mats examined by SEM. Significant differences
between the 2 samples are observed. Both sample
mats show rough and irregular surface morphology,
which is different from that of neat PLA, as reported
earlier [30]. This is likely due to the interplay between
Figure 1: ATR-FTIR spectra of fiber mats: (a) Neat PLA, (b) P-P-T, and (c) P-P-I-T.
1000 1500 2000 2500 3000 3500
νO–H
2994ν
as
CH
3
2944ν
s
CH
3
1753νC=O
1659νN–C=O
1453δ
as
CH
3
1381δC–H
1362δ
s
CH
3
νC–O
870νC–C
(a)
(b)
(c)
3400
1753
1182
1087
1453
2944
1659
2994 870
1362
Wavenumbers (cm
–1
)
3400
Band (cm
–1
) Assignment
1182–1087
4
B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
the 2 polymeric components during electrospinning.
Nonetheless, it is clearly observed that the surface
of P-P-I-T fibers is smoother than that of P-P-T. The
fiber mats of P-P-I-T contains TiO2 beads with higher
uniformity than those of P-P-T, as the addition of iPOH
slows down the TiO2 precipitation rate. The regions of
irregular fiber (beads) shape are caused by agglomeration
of TiO2 particles present as beads embedded in
the filaments. This is confirmed by EDX results, as
illustrated in Figure 3. The Ti content in the beads
is much higher, compared to that in the regular
fiber region. The size distribution of the filaments is
compared in Figure 4. The P-P-T fibers have an
average diameter of 800 nm, slightly smaller than that
of P-P-I-T (827 nm).
3.3 UV-Vis spectroscopy
UV-Vis spectroscopy is employed to examine absorption
behaviors of the materials, as shown in Figure 5. P-P-T
and P-P-I-T fibers show a major absorption band at
λmax 214 nm. This is due to the n→π* transition of the
carbonyl groups in PLA, which is similar to that observed
in spun fibers of neat PLA. All samples also show
a broad absorption covering the full visible region,
likely due to the translucent nature of the fiber mats.
A distinct absorption band is observed at 300 nm for
P-P-T and P-P-I-T fiber mats, indicating the presence
of TiO2 particles. This enables the materials to possess
photo-catalytic activity for use in many applications,
such as epoxidation of unsaturated oils or degradation
Figure 2: SEM images of electrospun fibers (a)–(c) P-P-T and (d)–(f) P-P-I-T at 5,000×, 10,000×, and 20,000×
magnifications.
Figure 3: EDX spectra illustrating atomic compositions of bead defects with different sizes present in (a) P-P-T
and (b) P-P-I-T fibers.
(a) (b) (c)
(d) (e) (f)
|
EDS Spot 1
|
EDS Spot 2
0.00k
0.66k
1.32k
1.98k
2.64k
3.30k
3.96k
4.62k
5.28k
0.00 1.00 2 .00 3.00 4.00 5.00
5.94k
|
EDS Spot 1
|
EDS Spot 2
0.00k
0.85k
1.70k
2.55k
3.40k
4.25k
5.10k
0.00 1.00 2.00 3.00 4.00 5.00
(a) (b)
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KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
of contaminated water. Due to space limitations, this
will be addressed in details in a separate work.
3.4 Degradation mechanisms
Degradation behaviors of the spun fiber mats are
examined in PBS solutions by activation with UVA
light. The fiber samples were soaked in PBS at 1, 4,
and 6 days, and their FTIR and UV-Vis spectra were
recorded, as shown in Figure 6. The ATR-FTIR and
UV-Vis results show evidences of PLA degradation
as a function of time, similar to those reported in our
previous work [31]. Both P-P-T and P-P-I-T mats show
similar FTIR changes, and the latter is chosen to show
the changes. A decrease in intensity of the 1659 cm–1
band of the amide group of PVP reflects that during
the degradation, PVP present on the surface of the
filaments is released and dissolves in PBS solutions.
In addition, a weak band in the same region is observed
at 1650 cm–1, associated with carboxylate of degraded
PLA.
Results from UV-Vis spectra of PBS solutions
after P-P-I-T fiber mats are soaked for 1, 4, and 6 days,
as shown in Figure 7, illustrates an absorption band of
lactate oligomers, products from the degradation of
PLA, at 202 nm. The intensity of the band increases
with the degradation time, indicating that degradation
of the PLA component takes place very early. This is
likely because of the presence of TiO2 catalytic particles
and the dissolubility of PVP from the filaments, which
in turn, exposes the PLA component to a higher degree
of hydrolysis.
4 Conclusions
Fiber mats of PLA/PVP blends loaded with TiO2
particles, i.e., P-P-T, and P-P-I-T, are successfully
fabricated by an electrospinning method. The fiber
mats absorb UV light in a region of 300 nm, which
enables their photo-catalytic activity. Preliminary
results from degradability experiments show that
degradation of the PLA component takes place very
Figure 5: UV-Vis spectra of fibers mats of: (a) neat
PLA, (b) P-P-T, and (c) P-P-I-T.
Figure 6: ATR-FTIR spectra of electrospun P-P-I-T
(10 kV) fiber soaked in PBS solution at: (a) 0, (b) 1,
(c) 4, and (d) 6 days.
Figure 7: UV-Vis spectra of P-P-I-T fiber mats as a
function of degradation time: 1, 4, and 6 days.
Figure 4: Size distribution of (a) P-P-T and (b) P-P-I-T
fiber mats.
0
5
10
15
20
25
30
35
570
720
860
1000
1140
Percentage (%)
Diameter (nm)
(b)
Average size 827 nm
0
5
10
15
20
25
30
35
570
720
860
1000
1140
Percentage (%)
Diameter (nm)
(a)
Average size 800 nm
1.0
1.1
1.2
1.3
1.4
1.5
1.6
Volts
200 300 400 500 600 700 800
Arbitrary units
Abs
Wavelength (nm)
(c)
(b)
(a)
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
1000 1500 2000 2500 3000 35 00
Wavenumbers (cm-1)
(a)
(b)
(c)
(d)
1753
1182
1087
1659
Wavenumber (cm
–1
)
1.0
1.2
1.4
1.6
1.8
2.0
2.2
200 202 204
Arbitrary units
wavelength (nm)
Abs
(d) 6 days
(c) 4 days
(b) 1 day
(a) PBS blank
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Volts
200 202 204
Arbitrary units
6
B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
early, due to the presence of TiO2 catalytic particles and
the dissolubility of PVP from the filaments.
Acknowledgements
The authors acknowledge financial supports from
the Thammasat University Research Fund (Theme
research) and the Center of Excellence in Materials
and Plasma Technology (M@P Tech), Thammasat
University. B.N. thanks the support from the Excellence
Foreign Scholarship (EFS) program provided by SIIT.
The authors would like to convey special appreciation
to the academic committee of The 6th International
Thai Institute of Chemical Engineering and Applied
Science Conference (ITIChE2016) for providing
the opportunity for this work to be published in this
journal.
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