Polymeric Fibers Containing Graphene

Abstract

Due to their superior properties, nanofibers are preferred in many fields, especially in tissue engineering, drug delivery, seed coating material, cancer diagnosis, lithium-air battery, optical sensors and air filtration. Compared to conventional fibrous structures, nanofibers are lightweight onedimensional nanomaterials with diameters in the range of tens to hundreds of nanometers, controllable pore structures, three-dimensional interconnected structures, high surface-to-volume ratios, and high mass transport properties which make them ideal for use in different applications. Many methods are used for production of nanofibers. However, centrifugal spinning is a technique that allows very fast nanofiber production. Besides, in this technique, wider range of polymers and solvents can be used and nanofibers with high porosity can be obtained by using different solution and process parameters. Diameter, total surface area, porosity and pore size of nanofibers affect performance. In addition, using nanofillers is a promising method to improve the properties of the fibers. The incorporation of graphene into the fibers improves mechanical, electrical, and thermal, properties of the fibers. In this study, polyacrylonitrile / polymethylmethacrylate fibers containing different ratios of graphene were produced by centrifugal spinning technique. Nanofibers containing 3, 5 and 7 wt.% graphene based on polymer weight were produced. Morphological and structural characterization was carried out using SEM, TEM and FTIR. The effect of graphene on nanofiber diameters and the distribution of graphene in the nanofibers have been studied. The morphology of the fibers prepared in nanocomposite structure was examined using SEM. The effect of graphene on nanofiber morphology was also determined by TEM. While nanofibers containing 3, 5 wt.% graphene had uniform morphology, it was observed that graphene affected fiber formation. When 7 wt. % graphene was used, bead formation was observed. In addition, increasing graphene content to 7 wt.% caused a decrease in average fiber diameters.

Full text

International
Congress on Multidisciplinary Natural Sciences
Uluslararası Multidisipliner Doğa Bilimleri Kongresi ISBN:NNNN-NNNN
Polymeric Fibers Containing Graphene
Elham ABDOLRAZZAGHIAN
1
Meltem YANILMAZ
2
Özet
Nanolifler, üstün özelliklerinden dolayı doku mühendisliği, ilaç salınımı, tohum kaplama
malzemesi, kanser teşhisi, lityum-hava pilleri, optik sensörler ve hava filtrasyonu başta olmak
üzere birçok alanda tercih edilmektedir. Geleneksel lifli yapılarla karşılaştırıldığında,
nanolifler, nanometre aralığında bir çapa sahip, hafif, tek boyutlu nanomalzemeler olmakla
birlikte kontrol edilebilir gözenek yapıları, üç boyutlu birbirine bağlı yapıları, yüksek yüzey-
hacim oranı ve yüksek kütle iletim özelliklerine sahiptir. Bu da onları farklı uygulamalarda
kullanım için ideal kılar. Nanofiber üretimi için birçok yöntem kullanılmaktadır. Ancak
santrifüj eğirme, çok hızlı nanofiber üretimine imkan veren bir tekniktir. Ayrıca bu teknikte
daha geniş çeşitlilikte polimerler ve çözücüler kullanılabilmekte ve farklı çözelti ve işlem
parametreleri kullanılarak yüksek gözenekliliğe sahip nanolifler elde edilebilmektedir.
Nanofiberlerin çapı, toplam yüzey alanı, gözenekliliği ve gözenek boyutu performansı etkiler.
Bunun yanında, nanofiller kullanmak, liflerin özelliklerini iyileştirmek için umut verici bir
yöntemdir. Grafenin liflere dahil edilmesi, liflerin mekanik, elektriksel ve termal özelliklerini
iyileştirir. Bu çalışmada, farklı oranlarda grafen içeren poliakrilonitril / polimetilmetakrilat
lifleri santrifüj eğirme tekniği ile üretilmiştir. Polimer ağırlığına göre ağırlıkça %3, 5 ve 7
grafen içeren nanofiberler üretilmiştir. Morfolojik ve yapısal karakterizasyonları SEM, TEM
ve FTIR kullanılarak yapıldı. Grafenin nanolif çapları üzerindeki etkisi ve grafenin
nanoliflerdeki dağılımı incelendi. Nanokompozit yapıda hazırlanan liflerin morfolojisi SEM
1
Yüksek Lisans Öğrencisi, İstanbul Teknik Üniversitesi, Nanobilim ve Nanomühendislik Programı, İstanbul, Türkiye, Orcıd:
0000-0003-0930-1080
2
İstanbul Teknik Üniversitesi, Tekstil Mühendisliği Bölümü, İstanbul, Türkiye, Orcıd: 0000-0003-0562-5715

International Congress on Multidisciplinary Natural Sciences (ICOMNAS-2021), Dec 01-02 2021
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kullanılarak incelenmiştir. Grafenin nanofiber morfolojisi üzerindeki etkisi TEM ile
belirlendi. Ağırlıkça 3 ve 5 wt.% grafen içeren nanolifler homojen morfolojiye sahipken,
grafenin lif oluşumunu etkilediği ve %7 grafen kullanıldığında bead oluşumu gözlenmiştir.
Ek olarak, grafenin %7 ye çıkarılması ortalama lif çaplarında azalmaya neden olmuştur.
Anahtar Kelimeler: Nanolifler, morfoloji, grafen, polimerler, lif, çap
Abstract
Due to their superior properties, nanofibers are preferred in many fields, especially in tissue
engineering, drug delivery, seed coating material, cancer diagnosis, lithium-air battery, optical
sensors and air filtration. Compared to conventional fibrous structures, nanofibers are
lightweight one-dimensional nanomaterials with diameters in the range of tens to hundreds
of nanometers, controllable pore structures, three-dimensional interconnected structures,
high surface-to-volume ratios, and high mass transport properties which make them ideal for
use in different applications. Many methods are used for production of nanofibers. However,
centrifugal spinning is a technique that allows very fast nanofiber production. Besides, in this
technique, wider range of polymers and solvents can be used and nanofibers with high porosity
can be obtained by using different solution and process parameters. Diameter, total surface
area, porosity and pore size of nanofibers affect performance. In addition, using nanofillers is
a promising method to improve the properties of the fibers. The incorporation of graphene
into the fibers improves mechanical, electrical, and thermal, properties of the fibers. In this
study, polyacrylonitrile / polymethylmethacrylate fibers containing different ratios of graphene
were produced by centrifugal spinning technique. Nanofibers containing 3, 5 and 7 wt.%
graphene based on polymer weight were produced. Morphological and structural
characterization was carried out using SEM, TEM and FTIR. The effect of graphene on
nanofiber diameters and the distribution of graphene in the nanofibers have been studied. The
morphology of the fibers prepared in nanocomposite structure was examined using SEM. The
effect of graphene on nanofiber morphology was also determined by TEM. While nanofibers
containing 3, 5 wt.% graphene had uniform morphology, it was observed that graphene
affected fiber formation. When 7 wt. % graphene was used, bead formation was observed. In
addition, increasing graphene content to 7 wt. % caused a decrease in average fiber diameters.
Keywords: Nanofibers, morphology, graphene, polymers, fiber diameter
Introduction
Nanofibers are a class of nanomaterials which has special properties that mainly due to their
extremely high surface to volume ratio compared to conventional fibers. Large surface area to
volume ratio, high porosity, small pore size, low density and excellent mechanical properties
are some of these properties. Because of these unique properties, nanofibers have been
presented as promising materials for different applications like purification, energy, textile,
tissue engineering, wound healing and wound dressing applications.

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Many methods are used for the production of nanofibers such as drawing, electrospinning,
centrifugal spinning, template synthesis, self assembly and chemical vapor deposition
(Ramakrishna, Lim, Fujihara, Teo, & Ma, 2005). Electrospinning which is based on
electrostatic forces is one of the major techniques to fabricate nanofibers. While this method
is an easy method at laboratory scale, it has some disadvantages in high-scale production such
as low production speed, unsafe working environment due to electrical field and high amount
of solvent consumption (Niu, Zhou, & Wang, 2019; Zhou, Wang, Gong, Liu, & Wei, 2020).
Centrifugal spinning is a low-cost and operationally safe technique to produce fibers for
multiple applications, it has a higher fiber yield compared to the electrospinning method. In
this technique, centrifugal forces are applied to a polymer solution to overcome its surface
tension and stretch the polymer droplet to form fibers. Then, the fibers are laid over each
other resulting in nano fiber based mats (Orrostieta Chavez, Lodge, & Alcoutlabi, 2021).
Graphene included electrospun polymeric and carbon nanofibers were studied for different
applications including energy storage systems, electronics, chemical sensors and medicine
owing to the properties like large surface area, stiffness, transparency, high thermal and
electrical conductivity (Raphael Mmaduka, Ishaq, & Fabian Ifeanyichukwu, 2019). Luo et al.
synthesized graphene/carbon nanofiber composite via electrospinning as a high performance
electrode for supercapacitors which demonstrate good electrochemical performance with a
high capacitance of 215 𝐹𝑔−1 at 1 𝐴𝑔−1 due to high conductivity and large surface area of
graphene which lead to fast kinetics (Luo et al., 2018). Shan et al. synthesized nitrogen doped
graphene/carbon nanofiber composite with polyacrylonitrile as a precursor via electrospinning
method and used that as an anode for lithium-ion battery which showed a high storage capacity
of 216 𝑚𝐴ℎ𝑔−1 in first cycle and rate performance of 154 𝑚𝐴ℎ𝑔−1 at 5 𝐴𝑔−1 due to highly
electrical conductivity, ordered structure and excellent flexibility of graphene (Shan et al.,
2019). Song and his coworkers prepared biocomposite nanofiber scaffolds of
polycaprolactone (PCL) with graphene oxide (GO) via electrospinning method with superior
mechanical properties due to high surface area, flexibility, stiffness and uniform dispersion of
graphene in the PCL matrix (Song et al., 2015). Herein, we prepared polyacrylonitrile
(PAN)/polymethyl methacrylate (PMMA) nanofibers containing different ratios of graphene
by a lab-scale centrifugal spinning and hierarchical porous nanofibers are obtained.
Experimental
1. Materials and method
In this study, polymer solutions were prepared by using PAN (Mw = 150000), PMMA (Mw
= 120000) and different amount of graphene (3 wt%, 5 wt% and 7 wt% relative to PAN and
PMMA) in dimethylformamide (DMF). For comparison, PAN/PMMA solution without
graphene was prepared with DMF at a room temperature for 24 hours. 3 wt%, 5 wt% and 7
wt% graphene was dispersed in DMF and stirred in a room temperature. After that, PAN and
PMMA were added to the dispersed graphene/DMF solutions and they were named as
PAN/PMMA/GRAPH3, PAN/PMMA/GRAPH5 and PAN/PMMA/GRAPH7. They were
stirred overnight in a room temperature to get homogeneous solutions. All of the solutions
were then fed continuously to the centrifugal spinning system with the aid of a syringe at a

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speed of 60 ml / h. In this study, the system was operated with a DC motor and the speed
was kept constant at 4000 rpm. The diameter of the nozzle used was 0.5 mm and the distance
between the collector and the nozzles was 20 cm.
2. Results and discussion
PAN/PMMA and PAN/PMMA/graphene nanofibers were synthesized via a centrifugal
spinning device. The centrifugal force overcame the surface tension when the rotational speed
climbed to a critical point, and liquid jets generated at the nozzles, stretched with solvent
evaporation, and deposited on the collectors in the shape of the fiber mat. The morphology
of the nanofibers prepared using the PAN/PMMA solution and with various weight ratios of
graphene was investigated by FEI Quanta FEG 250 Scanning Electron Microscope (SEM).
Figure 2.1 displays SEM images of PAN/PMMA nanofibers at different magnifications.
Nanofibers show smooth surface without apparent bead formation and long fibrous
morphology with homogeneously distributed diameters. While, the morphology of
PAN/PMMA/graphene-nanofibers demonstrate rough surface and creation of pores along
the fibers. Also, the formation of beads are seen on the surface of PAN/PMMA/GRAPH7
nanofiber (Figure 2.2, Figure 2.3, Figure 2.4). The average fiber diameter of PAN/PMMA,
PAN/PMMA/GRAPH3, PAN/PMMA/GRAPH5 and PAN/PMMA/GRAPH7 fibers were
measured as 1700 nm, 1461 nm, 1294 nm and 975 nm, respectively. It was observed that the
fiber diameter of PAN/PMMA decreased from 1700 nm to 1461 nm as introducing graphene.
The average diameter of fibers decreased as the amount of graphene increased from 3 wt% to
5 wt% (1461 nm to 1294 nm) and 5 wt% to 7 wt% (1294 nm to 975 nm) as well. Adding
graphene decreased the polymer amount feeded to the nozzles and led to decreased fiber
diameters.
Figure 2.1: SEM images of PAN/PMMA fibers at different magnifications
Figure 2.2: SEM images of PAN/PMMA fibers with 3% graphene at different magnifications

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Figure 2.3: SEM images of PAN/PMMA fibers with 5% graphene at different magnifications and diameter distributions
Figure 2.4: SEM images of PAN/PMMA fibers with 7% graphene at different magnifications and diameter distributions
TEM images were depicted to study the dispersion state of graphene in fibers. The
PAN/PMMA-based nanofiber had a smooth surface with one phase (Figure 2.5), while
PAN/PMMA/graphene-based nanofiber surface became rougher with graphene on the
surface of nanofibers (Figure 2.6). Kim et al. fabricated PAN/PMMA-based nanofibers
containing graphene by electrospinning method, and reported simiar results (Kim, Yang, &
Ferraris, 2012). Mohamed et al. synthesized PAN/Graphene oxide (GO) nanofibers by
dispersing different content of graphene oxide via electrospinning method. He also reported
that with increasing graphene content in PAN solution, the surface of nanofibers become
rougher and the average diameter of nanofibers become smaller due to increasing thermal,
electrical conductivities and viscosity of the solution (increasing conductivity decreases the
average diameter of fibers) (Abdel-Mottaleb, Mohamed, Karim, Osman, & Khattab, 2020).
Chen et al. prepared PVA/graphene composite nanofibers by dispersing different content of
graphene in PVA solution and increasing the graphene content in PVA solution led to decrease
in the diameter of nanofibers due to the addition of the G sheets (Chen, Chang, Pan, Chiang,
& Tseng, 2018). Moreover, it was seen that graphene was uniformly distributed in fibers which
is benefial for performance of the resulted nanofibers.

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Figure 2.5: TEM images of PAN/PMMA fibers
Figure 2.6: TEM images of PAN/PMMA fibers with 5% graphene
Fourier-transform infrared spectroscopy (FTIR) analysis (Spectrum Two; Perkin Elmer) was
performed to examine the chemical structures of the obtained nanofibers. Analyzes were
performed between 450-4000 𝑐𝑚−1 wavelength, in absorbance mode at room temperature.
FTIR results are given in Figure 2.7. PAN has the characteristic absorption band at 2240 which
is assigned to the -C≡N stretching of acrylonitrile unit in the polymer chain. PMMA has the
peak at 1730 𝑐𝑚−1 which attributed to the characteristic absorption band of carbonyl
stretching (Abeykoon, Bonso, & Ferraris, 2015). Herein, The FTIR spectra of PAN/PMMA
nanofibers demonstrate the peaks at 1731, 2241 and 2988 𝑐𝑚−1 corresponding to the C=O
(the characteristic peak for acrylate carboxyl group), C≡N (the characteristic peak for nitrile
group) and C-H (aldehyde group) , respectively, indicating the presence of both PMMA and
PAN. Sangermano et al. reported that in the FTIR spectrum of graphene there are no
important peaks that are related to any functional groups (Sangermano, Marchi, Valentini,
Bon, & Fabbri, 2011). Herein, with the addition of graphene, no change was observed in the
FTIR spectra of PAN/PMMA/GRAPH (3, 5 and 7 wt%) indicating no peaks for graphene
structure.

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0500 1000 1500 2000 2500 3000 3500 4000 4500
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
0.055
0.060
0.065
0.070
0.075
Absorbance
Wavelength, 1/cm
PAN/PMMA nanofiber
PAN/PMMA/GRAPH3 nanofiber
PAN/PMMA/GRAPH5 nanofiber
PAN/PMMA/GRAPH7 nanofiber
Figure 2.7: FTIR spectra of nanofibers
Conclusion
In this study, nanofibers were obtained by using PAN/PMMA and PAN/PMMA/graphene
solutions via centrifugal spinning technique. Increasing graphene amount in PAN/PMMA
solution led to decreased average fiber diameters. Moreover, adding graphene into the solution
affected the morphology and the surface of the PAN/PMMA nanofibers became rougher.
Uniform graphene distribution was observed from TEM images. Moreover, with increasing
graphene content to 7 wt%, beads are formed on the surface of the PAN/PMMA nanofibers.
However, adding graphene didn’t affect the FTIR spectra of PAN/PMMA nanofibers.
Acknowledgement
This research was supported by The Scientific and Technology Research Council of Turkey
(TUBITAK). Project Number: 219M348.
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