FUNCTIONALIZATION OF COTTON-CELLULOSE VIA HIGH
ENERGY IRRADIATION INITIATED GRAFTING AND
CYCLODEXTRIN IMMOBILIZATION
Gilles Desmet
Promoters: prof. dr. Judit Borsa and prof. dr. ir. Paul Kiekens
Supervisor: prof. dr. Erzsébet Takács
Master’s thesis submitted in order to obtain the degree of
Master of Science in Textile Engineering
Department of Textiles
Head: prof. dr. ir. Paul Kiekens
Faculty of Engineering
Academic year: 2009-2010
Association
of
Universities for Textiles
FUNCTIONALIZATION OF COTTON-CELLULOSE VIA
HIGH ENERGY IRRADIATION INITIATED GRAFTING
AND CYCLODEXTRIN IMMOBILIZATION
By Gilles DESMET
Master’s thesis submitted as finalization of the ETEAM (European Master’s degree in
Advanced Textile Engineering) program in order to obtain the academic degree of
Master of Science in Textile Engineering
Supervisor:
Prof. dr. Erzsébet TAKÁCS
Head of the Department of Radiation Chemistry
Institute of Isotopes
Hungarian Academy of Sciences
Promoters:
Prof. dr. Judit BORSA
Department of Physical Chemistry and Materials Science
Faculty of Chemical Technology and Biotechnology
Budapest University of Technology and Economics
Prof. dr. ir. Paul KIEKENS
Department of Textiles
Faculty of Engineering
University of Ghent
Department of Textiles
Head: prof. dr. ir. Paul KIEKENS
Faculty of Engineering
University of Ghent
Academic year 2009 - 2010
Preface i
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
PREFACE
This thesis is the finalization of a 2 year master’s program, known as ETEAM
(European Master’s degree in Advanced Textile Engineering) organized by the
Association of Textile Universities (AUTEX) of which the secretarial department is
situated at the Department of Textile at the University of Ghent. This program allowed
me to study at the technical universities of Tampere, Dresden, Ljubljana and Budapest,
where this master’s thesis was created. Professor Judit Borsa, from the Department of
Physical Chemistry and Materials Science at the Faculty of Chemical Technology and
Biotechnology at the Budapest University of Technology and Economics (BME: Budapesti
Műszaki és Gazdas{gtudom{nyi Egyetem), handed me the subject of my thesis and served
as my initial supervisor. Because of the thoroughgoing collaboration between professor
Judit Borsa and professor Erzsébet Takács, head from the department of Radiation
Chemistry at the Institute of Isotopes (IKI) from the Hungarian Academy of Sciences
(HAS), I would perform my research activities at this institute under the daily
supervision of professor Erzsébet Takács. This would allow me to work with
professional equipment and experienced researchers and technicians. For the practical
experiments, technical assistant Éva Koczogné Horváth, or Evike, would aid me.
My sincere thanks go in the first place to those three people, who proved to be
invaluable to the realization of this work. Both professor Borsa and professor Takács
possess a combination of unremitting kindness and profound knowledge which could
not make me imagine better supervisors, and Evike’s practical skill and help was
indispensable for the experimental part. Köszönöm szépen!
Secondly, I would like to thank professor Paul Kiekens, who made it possible for me to
go abroad, professor László Wojnárovits for his thorough editing of the manuscript,
Katalin Gonter and dr. Péter Hargittai for their help making the SEM-pictures, Zoltán
Papp for irradiating all the samples, dr. Enikő Földes for making the DSC
measurements and all the other people of the Radiation Chemistry department for
their support and making my time spent over there so pleasant!
Preface ii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Special thanks to my parents, for supporting me throughout the entire duration of my
studies and to Ilka, for her love and support.
Copyright :
The author gives permission to make this Master’s thesis available for consultation and
to copy parts of the Master’s thesis for personal use. Any other use falls under the
limitations of the copyright, especially with regard to the obligation of mentioning the
source explicitly on quoting the results of this Master’s thesis.
Budapest, 30th of May
Gilles Desmet
Summary iii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Association
of
Universities for Textiles
SUMMARY
FUNCTIONALIZATION OF COTTON-CELLULOSE VIA HIGH
ENERGY IRRADIATION INITIATED GRAFTING AND
CYCLODEXTRIN IMMOBILIZATION
By Gilles DESMET
Master’s thesis in order to obtain the degree of
Master of Science in Textile Engineering
Academic year: 2009-2010
Promoters: prof. dr. J. BORSA and prof. dr. ir. P. KIEKENS
Supervisor: prof. dr. E. TAKÁCS
Department of Textiles
Head: prof. dr. ir. P. KIEKENS
Faculty of Engineering
Ghent University
Academic year: 2009-2010
A study was made investigating the surface functionalization of cotton-cellulose using
i) pre-irradiation grafting (PIG) and ii) simultaneous grafting (SG) of glycidyl
methacrylate (GMA). This topic requires significant knowledge in several scientific
disciplines, viz. material sciences, chemistry and physics. The first major part of this
thesis consists therefore of an in-depth literature survey, compiling the relevant
information out of over 80 reference works, and supplies all the necessary knowledge
in order to fully understand the followed experimental procedures.
The second major part consequently grasps the experimental research: Glycidyl
methacrylate (GMA) will be grafted on cotton-cellulose according to the two
distinguished methods: i) pre-irradiation grafting (PIG) in which the substrate is
irradiated first and only afterwards immersed into a grafting solutions and ii)
simultaneous (or mutual) grafting (SG) in which substrate and grafting solutions are
irradiated together. Both reactions will result in a material consisting of a cellulose
backbone and grafted GMA side chains.
Summary iv
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Using visual analysis, SEM, gravimetrical measurements and FTIR spectroscopy, it is
found that PIG leads to more homogeneous samples with no obvious signs of
homopolymerized GMA, while SG leads to much higher yields under the same
reaction conditions but showed, however, clear indications of GMA-homopolymer. By
careful control of the reaction parameters, viz. consistence of the reaction mixture,
absorbed dose, moisture content, grafting temperature and grafting time, a degree of
grafting (in mass percentage) of 125% for PIG and 350% for SG can be reached. It is
shown that the moisture content has a significant impact on the grafting yield during
PIG, a result which has not been published earlier.
The thermal properties are measured using DSC and the grafted samples show an
increased thermal stability. UV/VIS spectroscopy and a gravimetrical determination of
the swelling percentage showed that the samples have increased adsorption properties
and an increased hydrophobicity, this hints for a possible future application as a
reactive filter. A special application of the grafted GMA is that they impart epoxide
groups which can, theoretically, serve as anchoring points for β-cyclodextrin (β-CD).
The immobilization of β-CD is further investigated. Dependent on the procedure, two
immobilizing procedures are considered: i) after PIG or SG, using a catalyst to open the
epoxide ring or ii) during SG. Only this second method, however, has showed clear
results. The resultant material is characterized using SEM, gravimetrical measurements
and adsorption measurements. Using SEM, little bolls were observed on the surface at
sufficient magnifications which were not observed in the simultaneous grafting
without β-CD in the grafting solution, and the adsorption properties were clearly
enhanced.
Keywords:
cotton-cellulose, pre-irradiation grafting, simultaneous (mutual) grafting, GMA, cyclodextrin
immobilization.
Extended Abstract v
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
EXTENDED ABSTRACT
Functionalization of cotton-cellulose via high energy irradiation
initiated grafting and cyclodextrin immobilization
Gilles Desmet
Promoters: prof. dr. Judit Borsa, prof. dr. ir. Paul Kiekens
Supervisor: prof. dr. Erzsébet Takács
Abstract: A study was made investigating the
surface functionalization of cotton-cellulose
using i) pre-irradiation grafting (PIG) and ii)
simultaneous grafting (SG) of glycidyl
methacrylate (GMA). The influence of the
reaction parameters was determined. It was
found that PIG leads to more homogeneous
fiber surfaces while SG leads to attached flakes
of homopolymerized GMA, despite the
addition of styrene as homopolymer
suppressor. Additionally, the immobilization
of β-cyclodextrin on both kinds of surfaces was
looked into.
Keywords: cotton-cellulose, pre-irradiation
grafting, simultaneous (mutual) grafting,
GMA, cyclodextrin immobilization
I. INTRODUCTION
ach application demands its own unique
material. The properties of synthetic
materials can be adjusted the way the
end-users defines them. Environmental issues
and the limited supply of petroleum, however,
advise the use of renewable, so-called green
materials. One of the most obvious green
materials is cellulose, being the most abundant
natural polymer on earth [1]. Green materials
however come the way nature supplies them. In
order to make them meet the demand of specific
applications, we can functionalize them. This
means that specific chemical functional groups
will be imparted to the material on a molecular
level. This will have its influence on the
supermolecular and the morphological level, as
well as on the resulting properties. In this work,
an epoxide ring will be imparted to the cellulose
through grafting of glycidyl methacrylate (GMA)
[2-4], initiated through irradiation. This means
that side chains of GMA will be placed on the
cellulose backbone using either pre-irradiation
(PIG) or simultaneous grafting (SG) [5-6]. In the
pre-irradiation grafting method cellulose is
irradiated in the presence of air which yields
peroxide groups [7-8]. The grafting-initiating
radicals are formed by decomposing these
peroxide groups in the grafting solution by
applying heat. A disadvantage of this method is
the degradation of the substrate due to the
radiation directly affecting the cellulose. During
simultaneous (mutual) grafting the irradiation is
carried out in the presence of the monomer
solution [4,9] and mainly solvent radicals are
created (due to their relative amount), which on
their turn may produce radicals in both
monomer and the substrate. Both solvent and
monomer can act as stabilizer, protecting the
cellulose against radiation. The disadvantage is
the formation of homopolymer.
The grafted materials can be used for, among
other things, the adsorption of water
contaminants [10]. The adsorption properties of
this material could be even further enhanced by
reaction between the reactive epoxide group and
β-cyclodextrin. This molecule is known for its
unique ability to form inclusion complexes with
aromatic and phenolic compounds, metals and
dyes [11-14]. Next to filtering purposes, the
inclusion complex forming ability of β-
cyclodextrin can also be used for the
incorporation of antimicrobials [15] or the slow
release of perfumes or drugs [16]. The first goal
of this work is to investigate the two procedures
of grafting GMA on cellulose and their effect on
the resulting material. The second goal is to
elucidate the methods to immobilize β-
cyclodextrin on the procured material,
depending on the precedent grafting technique,
viz. PIG [17-19] or SG [4]. The enhancement of
the adsorption properties will be tested.
II. EXPERIMENTAL
A. Materials
GMA (Aldrich®) and β-cyclodextrin (β-CD)
(CycloLab, Ltd.) were used without purification.
Styrene was purchased from Fluka® Analytical
and 2,4-Dichlorophenoxy acetic acid (2,4-D)
from Aldrich®. Purified water was obtained
E
Extended Abstract vi
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
from an ion exchanger equipment, type ELGA
Option 4. All solvents were from an analytical
grade. Cotton-cellulose samples (Testfabrics,
Inc.) were washed in boiling methanol for 3
hours.
B. Grafting procedure
B.1. Pre-irradiation grafting (PIG)
Cotton-cellulose fabric samples were irradiated
in air, at room temperature, by 60Co gamma rays
up to 40 kGy (dose rate 6 kGy h-1). Immediately
after irradiation the samples were immersed in a
0,5 – 3 M GMA solution of 20 v% H2O – 80 v%
MeOH at 40 to 70°C for 10 – 120 min. The
material to liquor (M:L) ratio was approx.: 0.1 g
sample per 10 ml solution. N2 bubbling was
applied to deoxygenate the monomer solutions.
Bubbling was started about half hour before
grafting and continued during the whole
grafting procedure. Grafted samples were first
washed carefully in methanol and remaining
monomer was removed by extraction in boiling
methanol for 3 hours. The samples were dried at
room conditions.
B.2. Simultaneous grafting (SG)
Monomer solutions were created containing 0,18
– 1,51 M GMA in 20 v% H2O – 80 v% MeOH as
well as 0,6 M styrene, to suppress
homopolymerization. In 1 experiment, NaOH
(0,5 M) was added. Glass ampoules were filled
with this solution (10 or 17 ml) together with 2
cotton samples and deoxygenated using N2
bubbling for approx. 5 min. The ampoules were
flame sealed in inert atmosphere and irradiated
at room temperature up to 20 kGy.
The same washing and drying procedure as for
PIG was used.
C. β-CD immobilization procedure
C.1. Upon PIG
The procedure as first described by Zhao and He
has been followed [16]. Pre-irradiated samples
were immersed into a 0,017 M β-CD solution of
20% DMF – 80% H2O with 0,25 M NaCl
(catalyst) in a M:L ratio of approx. 1:75 at 70°C
for 24 hours. Next they were extracted with H2O
(1 h), acetone (1 h) and MeOH (1 h).
C.2. Upon SG
Except for the solution, which could contain
NaOH (0,5 M) or HCl (0.5 M) as catalyst instead
of NaCl, the same procedure as for PIG has been
used.
C.3. During SG
0,017 M β-CD was added to the grafting
solution, which was changed to 33 v% H2O – 33
v% MeOH 33 v% DMF due to solubility issues of
β-CD in methanol. The rest of the procedure was
the same as in normal SG.
D. Evaluation of the samples
Sensory perceptions gave a rough idea about the
yield, and the macroscopic influence of grafting.
SEM analysis was performed upon gold coating
of the sample with a JSM 5600LV Scanning
Electron Microscope from JEOL Ltd.
The degree of grafting (DG (w%) = 100 (wg-w0)/w0 )
was determined by weighting the dried samples
before (w0) and after (wg) grafting.
The degree of immobilization (DI (w%) = 100 (wCD-
wg)/wg ) was determined by weighting the dried
samples before (wg) and after (wCD) the
cyclodextrin immobilization treatment.
FTIR spectroscopy was used to determine the
functional groups of the substrate with an ATI
Mattson Research Series 1 FTIR spectrometer in
the diffuse reflectance mode.
The band at 2900 cm-1, assigned to the stretching
vibrations of aliphatic C–H bonds, served as
internal standard.
DSC was performed to assess the thermal
properties with a Mettler DSC30 device. UV-spectroscopy of an aqueous solution of 0,2
mM 2,4-D before and after adsorption on the
grafted samples was performed with a JASCO
U-550 UV/VIS spectrophotometer. Swelling ( = 100(wS-wg)/wg ) was determined by
weighting the dried grafted samples (wg) and
the wet ones, after removing excess water with
blotting paper (wS).
III RESULTS AND DISCUSSION
A. Pre-irradiation grafting
A.1. Characterization of the samples
Grafted samples were considerably stiffer than
untreated samples. A significant change of
surface morphology was observed (Fig. 1).
Fig. 1: Surfaces of an (a) untreated and (b) grafted fiber (PIG,
DG(wt%)=64%). At a magnification of X10.000.
Extended Abstract vii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
The changes are homogeneous, as the free radical
graft copolymerization is initiated over the
entire fiber simultaneously.
FTIR-spectroscopy (Fig. 2) also confirmed the
grafting qualitatively. The absorption peak at
1728 cm-1 is attributable to the stretching
vibrations of the carbonyl group and can be
related to the DG as determined via
gravimetrical measurements. Both methods are
in good agreement with each other.
4000 3500 3000 2500 2000 1500 1000 500
0
1
2
3
4
5
b
Ab
so
rba
nce
(A
.U.)
Wavenumber (cm-1)
a GMA
b Cellulose
c GMA-grafted
cellulose
a
c
Fig. 2: FTIR spectra of a: GMA, b: cellulose and c: GMA-
grafted cellulose
A.2. Influence of the reaction parameters
A higher absorbed dose leads to a higher DG,
since more generated radicals lead to more
surviving peroxy compounds which initiate the
grafting.
The plasticizing effect of water in the cellulose
during irradiation increases the decay of the
radicals and ergo significantly decreases the
amount of initiation points: a difference of
humidity of approx. 65% changes the DG (w%)
with a factor 4-5.
Grafting time and temperature both influence
the free radical graft copolymerization reaction
positively.
The GMA-monomer concentration giving the
best yield is found at ± 2 M (Fig. 3). Initially, as
the concentration of reactant (GMA) increases,
also more grafted product will be created. At
higher concentrations, viscosity effects start
playing a role and also homopolymerization
may occur, slowing down the reaction.
0,5 1,0 1,5 2,0 2,5 3,0
10
20
30
40
50
60
70
DG
(w
t%)
Concentration (M)
Fig. 3: DG in function of GMA-monomer concentration.
20 kGy, 50 °C, 1 h.
A.3. Properties
The thermal stability of the material increased
together with the DG (Fig. 4).
0 100 200 300 400
-6
-4
-2
0
a DG=0%
b DG=19%
c DG=52%
He
at (m
W/m
g)
Temperature (oC)
exo
the
rmic
a
b c
en
do
the
rmic
Fig. 4: DSC spectrum of a: untreated, b: grafted (DG (w%) =
19%) and c: grafted (DG (w%) = 52%) cellulose fibers.
Swelling experiments showed that grafted
materials become more hydrophobic as the DG
increases.
The adsorption of 2,4-D (which is used as a
model molecule for a phenolic contaminant) is
slightly enhanced (Fig. 8).
B. Simultaneous grafting
B.1. Characterization of the samples
Samples procured upon the same doses and
monomer concentrations as in PIG have
nevertheless a much higher yield (double to
triple). This is because SG goes in 1 step and
takes place in a closed system. The disadvantage
is the visual trace of homopolymer, even after
the thorough washing procedure. SEM-pictures
show homopolymer flakes attached to the fiber’s
surface (Fig. 5). This is in clear contrast with the
samples obtained using PIG, which also looked
more uniform. It is believed that PIG leads to
grafted GMA all over the fiber, while SG leads to
grafted GMA mainly on the surface.
Fig. 5: Surfaces of grafted fibers, using (a): PIG
(DG(wt%)=32%) and (b): SG (DG(wt%)=35%).
At a magnification of X2000.
The FTIR spectra shows that some of the styrene,
which was in fact added to suppress homo-
polymerization; has copolymerized together
with the GMA (Fig. 6). The observed flakes are
most likely copolymers of GMA with styrene.
Extended Abstract viii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
4000 3000 2000 1000 0
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
5,5
a
Ab
so
rba
nce
(A
.U.)
Wavenumber (cm-1)
a Styrene
b Cellulose upon PIG
c Cellulose upon SG
b
c
Fig. 6: FTIR spectra of a: styrene b: GMA-grafted cellulose
using PIG and c: GMA-grafted cellulose using SG.
B.2.Influence of the reaction parameters
The same relevant effects as in PIG are observed,
but yields are a lot higher with SG. As soon as
doses resp. concentrations are increased over 5
kGy resp. 0.5 M large amounts of homo-polymer
are believed to be present, making accurate
estimations of the DG not possible.
Also the influence of NaOH was investigated,
since it is a known swelling agent for cotton.
However, the increase in OH- concentration was
detrimental for the free radical copolymerization
reaction. A similar effect for a decreasing pH is
expected and it is anticipated that the grafting
happens optimal at pH=7.
B.3. Properties
The thermal stability is believed to be further
increased because of the addition of small
amounts of styrene [4].
As SG leads to higher concentrations of GMA on
the fiber’s surface, the hydrophobicity is even
more increased. Also the adsorption properties
(Fig. 8) for an intermediate DG (w%) = ± 50% are
clearly better. Probably because there is more
GMA present on the surface, which is where the
adsorption occurs the easiest.
C. Immobilization of β-cyclodextrin
C.1. After grafting
The use of NaCl was successful as a catalyst for
the immobilization of β-CD on samples grafted
using PIG, but not for the samples grafted using
SG. Probably, the difference in morphology is
the reason. HCl might also successfully catalyze
the immobilization reaction, but does however
hydrolyze the cellulose samples to such a degree
its mechanical properties have become useless.
C.2. During SG
Little bolls appeared on the surface (Fig. 7). They
are believed to be an indication for the
cyclodextrins. Low doses (< 10 kGy) and low
monomer concentrations (< 0,5 M) are advised.
Fig. 7: Surfaces of a fiber simultaneously grafted with β-CD.
At a magnification of (a) X2000 and (b): X10.000.
Simultaneous grafting of SG + β-CD leads to
further enhanced adsorption properties (Fig. 8).
DMF was required in the grafting reaction
mixture to have an effect. Intermediate degrees
of grafting (40-90 wt%) are expected to show the
best adsorption properties.
250 300
0,00
Ab
so
rba
nce
(A
.U.)
Wavelength (nm)
a reference
b grafted using PIG
c grafted using SG
d grafted using SG+-CDa
b
c
d
Fig. 8: UV spectra of a solution in H2O of 2,4–D; a: before,
and after adsorption on grafted cellulose using b: PIG, c: SG
and d: SG + β-CD. All DGs were approx. 50% and each
sample had approx. the same weight, only d was a bit
lighter.
IV. CONCLUSION
A. PIG vs. SG
Cellulose grafted with GMA was produced
according to the 2 known procedures: PIG and
SG. SG leads to higher yields under similar
conditions, it has a higher radiation chemical
yield, which is due to the difference in reaction
mechanism. For the same reason, it is believed
that in PIG the fiber will be more uniformly
grafted with GMA while in SG most of the GMA
will be grafted on the surface [5].
In PIG the initiation points are formed in a first
step under the form of peroxy compounds. Then
in a second step all these initiation points are
activated simultaneously: because of the
temperature of the reaction mixture, the peroxy
compounds are decomposed and alkoxy radicals
are created. Since the initiation points are also in
the interior of the fiber, grafted GMA chains will
be everywhere. In SG, both grafted as
homopolymerized GMA is created as soon as
the reaction is started. The surface will become
coated by a GMA-polymer layer and make
further penetration of monomer impossible.
Extended Abstract ix
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
The SEM-photographs, the swelling experiment
and the adsorption experiment confirm this
theory.
B. The immobilization of β-CD
The immobilization of β-CD on the procured
GMA-grafted fibers was investigated. If the
treatment happened upon PIG, NaCl could be
successfully used as a catalyst [20]. However,
upon SG no β-CD immobilization seemed to
have occurred with NaCl thus a new route was
investigated using HCl as a catalyst. This
seemed to induce the appearance of little bolls
on the surface. However, the cellulose was
severely damaged by the treatment.
The best adsorption results were found when β-
CD was immobilized during SG. SEM-
photographs showed the appearance of little
bolls.
V. ACKNOWLEDGEMENT
This thesis was performed as a joint project
between the BME (Budapest University of
Technology and Economics) and the IKI
(Institute of Isotopes) of the HAS (Hungarian
Academy of Sciences).
The author would like to thank many people,
but especially Éva Koczogné Horváth for her
help with the experiments and prof. dr. Erzsébet
Takács and prof. dr. Judit Borsa for their
guidance, support and proofreading.
Additionally, I would like to thank prof. dr.
László Wojnárovits for his professional editing.
VI. REFERENCES
[1] D. Roy, M. Semsarilar, J. T. Guthrie and S.
Perrier, Chemical Society Reviews, vol. 38, pp.
2046-2064, (2009).
[2] E. Vismara, L. Melonea, G. Gastaldi, C.
Cosentinob and G. Torri, Journal of Hazardous
Materials, vol. 170, pp. 798–808, (2009).
[3] A. Sekine, N. Seko, M. Tamada and Y.
Suzuki, Radiation Physics and Chemistry, vol. 79,
pp. 16-21, (2010).
[4] P. R. S. Reddy, G. Agathian and A. Kumar,
Radiation Physics and Chemistry, vol. 72, pp. 511-
516, (2005).
[5] E. Takács, H. Mirzadeh, L. Wojnárovits, J.
Borsa, M. Mirzataheri and N. Benke, Nuclear
Instruments and Methods in Physics Research, vol.
265, pp. 217–220, (2007).
[6] S. Hassanpour, Radiation Physics and
Chemistry, vol. 55, pp. 41-45, (1999).
[7] E. Takács, L. Wojnárovits, J. Borsa, J. Papp, P.
Hargittai and L. Korecz, Nuclear Instruments and
Methods in Physics Research, (2005).
[8] N. Benke, E. Takács, L. Wojnárovits and J.
Borsa, Radiation Physics and Chemistry, vol. 76,
pp. 1355-1359, (2007).
[9] E. Takács, L. Wojnárovits, J. Borsa and I.
Rácz, Radiation Physics and Chemistry, (2009).
[10] E. Takács, L. Wojnárovits and C. M.
Földváry, Radiation Physics and Chemistry, vol.
79, pp. 848-862, (2010).
*11+ B. Vončina and A. Le Marechal, Journal of
Applied Polymer Science, vol. 96, pp. 1323-1328
(2005).
*12+ B. Vončina. (2005). Use and determination of
beta-cyclodextrin on textile substrates [Presentation
(ppt)].
[13] G. Crini, Dyes and Pigments, vol. 77, pp. 415-
426, (2008).
[14] G. Crini, H. N. Peindy, F. Gimbert and C.
Robert, Separation and Purification Technology,
vol. 53, pp. 97–110, (2007).
[15] E. S. Abdel-Halim, M. M. G. Fouda, I.
Hamdy, F. A. Abdel-Mohdy and S. M. El-Sawy,
Carbohydrate Polymers, vol. 79, (2010).
[16] D. Zhao, L. Zhao, C. Zhu, Z. Tian and X.
Shen, Carbohydrate Polymers, vol. 78, pp. 125-130,
(2009).
[17] T. Hirotsu, Thin Solid Films, vol. 506-507,
(2006).
[18] C. A. B. Nava-Ortiz, G. Burillo, E. Bucio and
C. Alvarez-Lorenzo, Radiation Physics and
Chemistry, vol. 78, pp. 19–24, (2009).
[19] P. Le Thuaut, B. Martel, G. Crini and U.
Maschke, Journal of Applied Polymer Science, vol.
77, pp. 2118–2125, (2000).
[20] X.-B. Zhao and B.-L. He, Reactive Polymers,
vol. 24, pp. 9-16, (1994).
Contents x
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
CONTENTS
Table of Contents
PREFACE ......................................................................................................................................i
SUMMARY ................................................................................................................................ iii
EXTENDED ABSTRACT .......................................................................................................... v
CONTENTS ................................................................................................................................. x
Table of Contents ................................................................................................................... x
List of Figures ...................................................................................................................... xiv
INTRODUCTION ................................................................................................................. xviii
An introduction to the functionalization of green materials ...................................... xviii
The set-up of this thesis ....................................................................................................... xx
NOMENCLATURE ............................................................................................................... xxii
PART I: LITERATURE SURVEY ............................................................................................... 1
1 The characteristics of cotton-cellulose ......................................................................... 1
1.1 Introduction to cellulose ....................................................................................... 1
1.2 Molecular: The chemical structure ...................................................................... 2
1.2.1 The monomer: β-D-glucopyranose .............................................................. 2
1.2.2 The polymer: Cellulose.................................................................................. 3
1.2.3 Single chain conformation ............................................................................ 5
1.2.4 Degree of polymerization and molar mass distribution .......................... 6
1.3 Supermolecular: The crystal structure ................................................................ 7
1.3.1 The fringed fibril model ................................................................................ 8
1.3.2 Crystallinity .................................................................................................... 9
1.4 Morphological: The fiber structure .................................................................... 12
Contents xi
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
1.4.1 Microfibrils and fibrils ................................................................................. 12
1.4.2 The cotton fiber ............................................................................................. 14
1.4.3 Pore structure................................................................................................ 16
1.5 Chemical reactivity .............................................................................................. 16
1.5.1 Accessibility .................................................................................................. 17
1.5.2 Activation ...................................................................................................... 17
2 Radiation chemistry ..................................................................................................... 19
2.1 Radionuclides ....................................................................................................... 19
2.1.1 Radioactivity ................................................................................................. 19
2.1.2 Radioactive decay ........................................................................................ 20
2.1.3 Cobalt-60 (60Co)............................................................................................. 21
2.2 Ionizing radiation ................................................................................................. 22
2.2.1 Interaction processes between γ-irradiation and matter ........................ 23
2.2.2 Linear energy transfer (LET) ...................................................................... 24
2.3 Radiation dosimetry ............................................................................................ 25
2.3.1 Absorbed dose .............................................................................................. 25
2.3.2 Radiation chemical yield ............................................................................. 25
2.4 Irradiation of cellulose ......................................................................................... 26
2.4.1 The formation of free radicals in cellulose................................................ 26
2.4.2 Caused effects upon irradiation ................................................................. 28
3 Graft copolymerization ............................................................................................... 31
3.1 Grafting principles ............................................................................................... 31
3.1.1 Grafting methodology ................................................................................. 31
3.1.2 Grafting techniques ...................................................................................... 33
3.2 Radiation induced free radical graft copolymerization .................................. 34
3.2.1 The theoretical principles of pre-irradiation grafting ............................. 34
Contents xii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
3.2.2 The theoretical principles of simultaneous grafting ............................... 35
3.2.3 The free radical graft copolymerization of glycidyl methacrylate ........ 36
4 Cyclodextrins ................................................................................................................ 38
4.1 Structure ................................................................................................................ 38
4.2 Inclusion complexes ............................................................................................. 40
4.3 Immobilization techniques on textiles .............................................................. 42
PART II: AIM OF THIS WORK ............................................................................................... 45
5 Earlier results ................................................................................................................ 45
5.1 Copolymers of cellulose and PGMA ................................................................. 45
5.2 Immobilization of β-CDs on substrates grafted with PGMA ........................ 46
6 Aim of this work .......................................................................................................... 48
PART III: IMPLEMENTATION AND ANALYSIS OF THE EXPERIMENTS .................. 50
7 Experimental ................................................................................................................. 50
7.1 Materials ................................................................................................................ 50
7.2 Irradiation facility ................................................................................................ 51
7.3 Grafting procedures ............................................................................................. 53
7.3.1 Pre-irradiation grafting (PIG) ..................................................................... 53
7.3.2 Simultaneous grafting (SG)......................................................................... 55
7.4 Material characterization .................................................................................... 58
7.4.1 Morphological analysis using SEM ........................................................... 58
7.4.2 Analysis of the functional groups using FTIR spectroscopy ................. 58
7.4.3 Gravimetrical measurements ..................................................................... 58
7.4.4 Analysis of the hydrophilicity via the swelling percentage ................... 60
7.4.5 Analysis of the adsorption properties using UV/VIS spectroscopy ..... 60
7.4.6 Analysis of the thermal properties using DSC......................................... 60
8 Results and discussion ................................................................................................ 61
Contents xiii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
8.1 Pre-irradiation grafting of glycidyl methacrylate (GMA) .............................. 61
8.1.1 Analysis of the pre-irradiated grafted samples ....................................... 61
8.1.2 Influence of the parameters during the pre-irradiation ......................... 66
8.1.3 Properties ...................................................................................................... 71
8.1.4 Cyclodextrin immobilization ...................................................................... 73
8.2 Simultaneous grafting of GMA .......................................................................... 75
8.2.1 Characterization of the samples ................................................................. 75
8.2.2 Influence of the parameters during simultaneous grafting ................... 79
8.2.3 Properties ...................................................................................................... 81
8.2.4 Cyclodextrin immobilization ...................................................................... 82
9 Conclusion .................................................................................................................... 85
9.1 Characterization ................................................................................................... 85
9.2 Influence of the parameters ................................................................................ 86
9.3 Properties .............................................................................................................. 87
9.4 Immobilization of β-CD ...................................................................................... 88
APPENDICES ............................................................................................................................ 89
Appendix A: Experimental data ........................................................................................ 89
A.1 Dependence of the parameters in pre-irradiation grafting ................................. 89
A.1.1 Monomer concentration .................................................................................... 89
A.1.2 Absorbed dose .................................................................................................... 90
A.1.3 Moisture content ................................................................................................ 91
A.1.4 Temperature ....................................................................................................... 91
A.1.5 Grafting time ....................................................................................................... 92
A.2 Dependence of the parameters in simultaneous grafting ................................... 94
A.2.1. Adsorbed dose ................................................................................................... 94
A.2.1 Monomer concentration .................................................................................... 94
Contents xiv
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Appendix B: SEM pictures .................................................................................................. 95
B.1 SEM photographs of untreated cotton-cellulose ................................................... 95
B.2 SEM photographs of pre-irradiated grafted cotton-cellulose.............................. 96
B.3 SEM photographs of simultaneously grafted cotton-cellulose ........................... 99
ADDENDUM: NEDERLANDSE SAMENVATTING ........................................................ 103
BIBLIOGRAPHY ..................................................................................................................... 109
List of Figures Figure 1: Structural formula of cellulose. .................................................................................................... 2
Figure 2: Fischer projection (a) and stereo projection (b) of D-glucose........................................................ 2
Figure 3: Representation of α-D-glucopyranose (a) and β-D-glucopyranose (b) in the 4C1 conformation. . 3
Figure 4: Representation of cellulose with cellobiose as repeating base unit. ............................................... 5
Figure 5: Sketch of a random helix to elucidate the meaning of n and h (Rees, 1977 29, p. 42). ................... 5
Figure 6: A schematic representation of the rotation possibilities in the cellulose chain. ............................ 6
Figure 7: Intramolecular hydrogen bonds stabilizing the cellulose chain. ................................................... 6
Figure 8: Intermolecular hydrogen bonding causing the formation of cellulose sheets. .............................. 7
Figure 9: Fringed fibrillar model (Hearle, 1958 38). ..................................................................................... 8
Figure 10: Schematic representation of the unit cell in a cellulose crystalline structure (Wakelyn, et al.,
2007 26, p. 561). ............................................................................................................................................ 9
Figure 11: Illustrative sketch of surface chains (gray) among the crystallite core chains (black)
(Nishiyama, 2009 42). ................................................................................................................................. 12
Figure 12: Schematic representation of a bundle microfibrils. Each microfibril consists of crystallites,
which are represented in the picture as cubes. (Zugenmaier, 2001 34). ...................................................... 13
Figure 13: Photographs of cotton-cellulose microfibrils, created using transmission electron micrography
(Wakelyn, et al., 2007 26, p. 543 and p. 577 ). ............................................................................................ 14
Figure 14: Computer generated montage of the organization of the different layers in a cotton fiber.
(Wakelyn, et al., 2007 26, p. 543). ............................................................................................................... 14
Figure 15: Kidney bean shaped cross-sections of cotton fibers (Wilding, 2007 49). .................................... 15
Figure 16: Diagram of the decay of radionuclides via γ-radiation. ............................................................ 21
Figure 17: Diagram of the decay of cobalt 60 towards the stable isotope nickel 60. ................................... 22
Figure 18: Illustration of the excitation mechanism. ................................................................................. 22
Contents xv
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Figure 19: Illustration of the ionization mechanism. ................................................................................. 23
Figure 20: Reaction mechanism of the radical at C(4) towards an allyl radical via dehydrogenation. ...... 27
Figure 21: Proposed degradation reaction mechanism leading from the formation of a radical at C(4). The
red fishhook arrows represent electron movement...................................................................................... 29
Figure 22: Schematic representation of the grafting to method (Roy, et al., 2009 1).................................. 32
Figure 23: Schematic representation of the grafting through method (Roy, et al., 2009 1). ....................... 32
Figure 24: Schematic representation of the grafting from method (Roy, et al., 2009 1). ............................ 33
Figure 25: Structural formula of glycidyl methacrylate. ........................................................................... 36
Figure 26: Radical polymerization of GMA. The red fishhook arrows represent the electron movement. R
represents the substrate, in this work, cellulose. XY represents an impurity in the reaction mixture. ..... 37
Figure 27: Structural formulas of α-, β- and γ-cyclodextrin (Skowron, 2006 79). ..................................... 38
Figure 28: Structural formulas of β-cyclodextrin with the glucopyranose units in the 4C1 chair
conformation. ............................................................................................................................................. 39
Figure 29: Schematic illustrative representation of β-cyclodextrin. .......................................................... 39
Figure 30: Inclusion complex of β-cyclodextrin with toluene. ................................................................... 41
Figure 31: 6-deoxy-6-diethylenetriamine-β-cyclodextrin forming an inclusion complex with a metal ion
(M) (Rizzarelli and Vecchio, 1999 82). ........................................................................................................ 41
Figure 32: β-cyclodextrin dimer complex with 4 Cu(II) ions in a frontal view (Chapman and Sherman,
1997 81). ...................................................................................................................................................... 42
Figure 33: BTCA used as a cross-linking agent to bind cyclodextrin to a fiber surface. ........................... 42
Figure 34: Structural formula of (a): NMA-β-CD (a) and (b): MCT-β-CD. ............................................ 43
Figure 35: Reaction scheme of the immobilization of β-CD on a graft copolymer of PGMA with a
substrate R (which in this work represents cellulose). ............................................................................... 44
Figure 36: Structural formula of (a) styrene, (b) 2,4-D and (c) DMF. ...................................................... 50
Figure 37: Gamma-irradiator used for the irradiation of the samples. ....................................................... 52
Figure 38: Immersed 60Co source. .............................................................................................................. 52
Figure 39: Prepared cotton cellulose sample, before numbering (approx. 3,5 cm²). ................................... 53
Figure 40: Immobilization of β-CDPM on a graft copolymer of cellulose (R) with PGMA. The DP of the
β-CDPM is symbolized by ‘p’. ................................................................................................................... 57
Figure 41: Photographs of samples procured upon PIG having a DG (wt%) of (a): 25% and (b): 58%. .. 61
Figure 42: (a): An untreated fiber and (b): a grafted fiber with a DG (wt%) = 32%. PIG at 20 kGy in a
1,5 M GMA solution at 40°C for 1 h. Magnification of X2000. ............................................................... 62
Figure 43: (a): An untreated fiber and (b): a grafted fiber with a DG (wt%) = 64%. PIG at 20 kGy in a
1,5 M GMA solution at 40°C for 1 h. Magnification of X10.000. ............................................................ 62
Contents xvi
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Figure 44: FTIR spectra from a: GMA, b: Cellulose and c: GMA-grafted cellulose .................................. 64
Figure 45: FTIR spectra of grafted cellulose, pre-irradiated at several different doses. From high to low:
40 – 30 – 20 – 15 – 10 - 5 - 0 kGy. ............................................................................................................. 65
Figure 46: Relationship between the DG and the intensity of the peak at 1728 cm-1, which corresponds to
the carbonyl group of the grafted GMA. .................................................................................................... 65
Figure 47: Degree of grafting as a function of the absorbed dose. Grafted in a 1,5 M GMA grafting
solution at 50°C for 1 h. ............................................................................................................................. 67
Figure 48: Degree of grafting as function of the water content in the samples. Pre-irradiated at 10 kGy
and grafted in a 1,5 M GMA solution at 50°C for 1 h............................................................................... 68
Figure 49: Degree of grafting as a function of the monomer concentration in M. Pre-irradiated at 20 kGy
and grafted at 50°C for 1 h. ........................................................................................................................ 69
Figure 50: Degree of grafting as a function of the grafting temperature in °C. Pre-irradiated at 20 kGy
and grafted in a 1,5 M GMA solution for 1 h. ........................................................................................... 69
Figure 51: Degree of grafting as a function of the grafting time in minutes. Pre-irradiated at 20 kGy and
grafted in a 1,5 M GMA solution at 50°C. Taken out with a clean metal pair of tweezers. ...................... 70
Figure 52: Degree of grafting as a function of the grafting time in minutes. Pre-irradiated at 20 kGy and
grafted in a 1,5 M GMA solution at 50°C. Taken out with a sterile silicon wire. ..................................... 71
Figure 53: Diagram of the DSC experiment of a: untreated cotton-cellulose, b: cotton-cellulose upon PIG
with a DG (wt%) = 19% and c: cotton-cellulose upon PIG with a DG (wt%) = 52%. ............................. 72
Figure 54: Correlation between the swelling and the DG of pre-irradiated grafted samples. .................... 72
Figure 55 UV-spectra of an aqueous solution of 2,4-D; a: before adsorption, b: after adsorption on
untreated cellulose and c: after adsorption on cellulose, grafted using PIG, with a DG (wt%) = 52,5 %. 73
Figure 56: GMA-grafted cellulose treated with a 0,017 M β-CD solution at 70°C for 24 h using (a) 0,5 M
NaOH and (b) 0,5 M HCl as catalyst. Magnification of X10.000............................................................. 75
Figure 57: SEM photograph at X1000 of a grafted fiber with a DG (wt%) = 35%, simultaneously
irradiated and grafted at 5 kGy in a 0,38 M GMA solution. ..................................................................... 76
Figure 58: FTIR spectra of a: Styrene, b: Grafted cotton-cellulose procured using PIG and c: Grafted
cotton-cellulose procured using SG. .......................................................................................................... 77
Figure 59: Reaction scheme suggesting the copolymerization mechanism between GMA and styrene. The
red fishhook arrows represent electron movement...................................................................................... 78
Figure 60: FTIR spectra of a: GMA monomer and b: Grafted cotton-cellulose having a DG (wt%) of
301% procured upon SG at a dose of 15 kGy in a reaction mixture of 0,38 M GMA. .............................. 78
Figure 61: Degree of grafting as a function of the absorbed dose, grafted in a 0,38 M reaction mixture. . 79
Figure 62: Degree of grafting as a function of the monomer concentration. SG at 20 kGy. ...................... 80
Contents xvii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
Figure 63: Correlation between the swelling and the DG of simultaneously grafted samples. .................. 81
Figure 64: UV-spectra of an aqueous solution of 2,4-D; a: before adsorption, b: after adsorption on
cellulose, grafted using PIG, with a DG (wt%) = 52,5% and c: after adsorption on cellulose, grafted using
SG, with a DG (wt%) = 51,5%. ................................................................................................................. 82
Figure 65: Grafted fibers with GMA+ β-CDPM at magnifications of (a): X2000 and (b): X10.000. SG in
a 0,38 M GMA and 0,017 M β-CD 33 v% DMF – 33 v% H2O – 33 v% MeOH solution at 5 kGy. DG
(wt%)+DI (wt%) = 39%. ........................................................................................................................... 83
Figure 66: Grafted fibers with GMA+ β-CDPM at magnifications of (a): X2000 and (b): X10.000. SG in
a 0,38 M GMA 20 v% H2O – 80 v% MeOH solution with 1,85 g β-CDPM per 100 ml at 5 kGy. DG
(wt%)+DI (wt%) = 49%. ........................................................................................................................... 84
Figure 67: UV-spectra of an aqueous solution of 2,4-D; a: before adsorption, b: after adsorption on
cellulose, grafted using SG, c: after adsorption on cellulose, grafted using SG with β-CD monomer and d:
after adsorption on cellulose, grafted using SG with β-CDPM ................................................................. 84
Figure 68: Untreated cotton at a magnification of (a): X500; (b): X1000; (c): X2000 and (d): X10.000. . 95
Figure 69: PIG at 20 kGy, 40°C, 1 h, 1,5 M GMA. DG (wt%) = 32%. Magnification of (a), (e): X500;
(b): X1000; (c), (f): X2000 and (d): X10.000. ............................................................................................ 96
Figure 70: PIG at 20 kGy, 70°C, 1 h, 1,5 M GMA. DG (wt%) = 64%. Magnification of (a) and (e):
X500; (b): X1000; (c) and (f): X2000 and (d) X10.000. ............................................................................ 97
Figure 71: (a) and (b): PIG at 40 kGy, 50°C, 1 h, 1,5 M GMA. Magnifications of X2000 resp. X10.000.
(c) and (d): PIG at 20 kGy, 50°C, 15 min, 1,5 M GMA followed by 24 h in 0.5 M NaOH and 0,017 M β-
CD. Magnifications of X2000 resp. X10.000. (e) and (f): PIG at 20 kGy, 50°C, 15 min, 1,5 M GMA
followed by 24 h in 0.5 M HCl and 0,017 M β-CD. Magnifications of X2000 resp. X5000. .................... 98
Figure 72: SG at 5 kGy, 0,38 M GMA. DG (wt%) = 35%. Magnifications of (a) X500; (b) X1000; (c)
and (e) X2000; (e) and (f) X10.000. ........................................................................................................... 99
Figure 73: SG at 5 kGy, 0,76 M GMA. DG (wt%) = 55%. Magnifications of (a): X500; (b): X1000; (c)
and (e): X2000; (e) and (f): X10.000. ....................................................................................................... 100
Figure 74: SG at 5 kGy in 0,38 M GMA and 0,017 M β-CD in DMF –H2O –MeOH (33 v% each).
Magnifications of (a): X500; (b), (c) and (e): X2000; (e) and (f): X10.000. ............................................. 101
Figure 75: SG at 5 kGy, 0,38 M GMA and 1,85 g M β-CDPM per 100 ml in 20 v% H2O – 80 v%
MeOH. Magnifications of (a) and (d): X500; (b) and (e): X2000; (c) and (f): X10.000. ......................... 102
Introduction xviii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
INTRODUCTION
An introduction to the functionalization of green materials While technology has brought us (the developed world) an abundance of food,
monster traffic jams and tons and tons of throw-away articles, it came at a price.
During the last decades the awareness for the caused, global, problems has been
growing steadily. Some of the ‘hotter’ topics include, but are not limited to: global
warming, air and water pollution, the hole in the ozone layer, the destruction of the
rain forest and the depletion of the natural reserves. This calls for innovations. One of
the, already followed, paths is the investigation in green materials, or natural materials.
Green materials offer a solution to the problem of the depletion of the natural reserves
since they are renewable, plus they are non-polluting. Many of today’s materials are
specifically designed for their application, but natural materials come in the way
nature supplies them. While bio-engineers already succeed to drastically improve
desired properties, genetic engineering stays a tricky problem and generally, reaching
the same versatility as is applicable for man-made materials is not (yet) possible. A
solution lies in modifying the properties of the natural materials, applying old
technologies used for the conventional synthetic materials as well as new ones. One of
the most obvious green materials is cellulose, being the most abundant natural
polymer on earth (Roy, et al., 2009 1). Cellulose has been the subject of many studies
and its general structure and properties are quite well-known, but nevertheless a lot of
uncertainties remain. Rather than unraveling the remaining mysteries around
cellulose, this work will focus on the already known properties and one of the ways to
alter these or add new ones. In other words, the goal is to functionalize the cellulose.
More specifically, the idea of functionalization is to introduce specific chemical
functional groups on a molecular level to the material. This will have its influence on
the supermolecular and the morphological level, as well as on the resulting properties.
The resulting material possesses the imparted functionality but its bulk still consists
mainly of cellulose and thus the intrinsic properties of cellulose are retained.
Introduction xix
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
An interesting way to achieve the desired functionalization is via graft copolymerization.
In fact, graft copolymerization of cellulose is one of the key ways to alter its properties
(Roy, et al., 2009 1). This technique allows to combine the best properties of two (or
even more) polymers in one material. By changing the parameters of the graft
copolymerization reaction, viz. polymer type of the grafted chains, degree of
polymerization, the polydispersities of both main and grafted chains, the graft density
and the graft uniformity, it is possible to synthesize tailor-made materials according to
the desired properties. The methods to achieve this graft copolymerization are
numerous, one of them is via a high energy irradiation initiated graft copolymerization, a
topic of radiation chemistry. As the name gives away, this is the study of the chemical
effects of matter induced by radiation, in this work more specifically: γ-irradiation
emitted by cobalt 60 (Takács, et al., 2007 5; Takács, et al., 2010 10; Badawy, et al., 2001 21).
It is obvious that next to the choice of bulk polymer (cotton), also the polymer that will
become grafted on the cotton surface is crucial for the end-product. Poly(glycidyl
methacrylate) (PGMA) is an interesting choice under increasing interest (Vismara, et al.,
2009 2; Sekine, et al., 2010 3), because it has the very reactive epoxide group at one end. A
graft copolymer of cellulose with poly(glycidyl methacrylate) is thus particularly
interesting because i) intrinsically, it already imparts several interesting properties to
cellulose, viz. flame retardancy, the enhanced adsorption of aromatic contaminants and
the adsorption and chelation of metals (Vismara, et al., 2009 2; Le Thuaut, et al., 2000 19),
ii) due to its reactivity it can basically be changed in several other functional groups,
e.g. in a hydroxyl, amine, thiol or phosphoric acid group (Nava-Ortiz, et al., 2009 18) iii)
it is an excellent anchor point for numerous molecules, e.g. cyclodextrins.
This immobilization of cyclodextrins will be examined more closely because of the very
special properties of cyclodextrins, viz. they have a very specific shape which allows
them to form inclusion complexes (host-guest complexes) with several compounds (Del
Valle, 2004 22). This means that within the cavity of the cyclodextrin a guest molecule
can be held, without forming any covalent bonds. There is a dynamic binding between
the guest molecules and the host cyclodextrin. The strength of the binding is merely
depending on how well the host and the guest ‘fit’ together. This property has
Introduction xx
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
numerous applications, ranging from simple adsorption to the incorporation of
antimicrobials or the controlled release of perfumes or drugs. However, because
cyclodextrins are quite voluminous molecules, steric effects make it impossible to bind
the cyclodextrins directly to the cellulose so this is why it is necessary to work via the
poly(glycidyl methacrylate) chains. This thesis will hence also further investigate how
to permanently bind cyclodextrins onto cotton textiles, a research domain that has been
growing from the early 80’s and is receiving a lot of attention lately (Vončina and Le
Marechal, 2005 11; Heise, et al., 2005 23). Even during the creation of this thesis an article
appeared (Abdel-Halim, et al., 2010 15), which reported the simultaneous grafting with
β-CDs present in the grafting reaction, a procedure also investigated in this work (see
3.2.2 and 8.2).
Because of the many interesting imparted properties, there are multiple applications
possible for both the GMA-grafted cellulose as for the subsequent cyclodextrin-
immobilized material. One of the most interesting and useful applications receives a lot
of attention recently, i.e. the uptake of water contaminants (Vismara, et al., 2009 2;
Sekine, et al., 2010 3; Takács, et al., 2010 10; O’Connell, et al., 2008 24; Sokker, et al., 2009
25), because water contamination may lead to heavy environmental damage and pose a
serious hazard for human health. While the GMA-grafted cellulose is already able to
filter many contaminants, a following cyclodextrin immobilization is supposed to even
further enhance the adsorption properties and make them more specific towards
aromatics and phenols, dibenzofuran molecules, metals and dyes (Crini, 2008 13)
The set-up of this thesis It may already become clear that this thesis situates at the interface of several scientific
disciplines, viz. material sciences, chemistry and physics. It requires a significant
background in order to fully appreciate and understand the performed mechanisms.
This is why the first part of this work exists out of an in-depth literature survey
reviewing the theoretical principles behind the used techniques, an endeavor
undertaken in the first place for myself, to achieve a deeper knowledge, and in the
second place for the reader, who might not be an expert in every scientific field. I
attempted to represent the important findings in a relevant yet complete way. Since an
Introduction xxi
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
image says more than a thousand word, a lot of results are represented using pictures.
The second part is the link between the literature survey and the practical aspect of this
thesis. In the first place, some of the most important articles considered directly linked
to the practical research in this work will be reviewed in a very condensed way,
presenting the experimental methods and results of importance. And in the second
place and directly linked to this follows the aim of this work: i.e. investigating the
grafting of glycidyl methacrylate on cotton, according to the two known procedures, viz.
pre-irradiation (PIG) and simultaneous grafting (SG). A special application is the use of
the imparted epoxy groups in the material to immobilize cyclodextrins.
The third part consists of the experimental implementation in order to fulfill the
stipulated investigation and a discussion linking all the information gained in this
work + the results from previous authors. This discussion is built around the personal
experimental research and includes:
i) The assessment of the grafted material procured by both methods (PIG and SG),
characterized using several complementary analytical techniques, viz. visual and other
sensory perceptions, SEM, gravimetrical measurements and FTIR spectroscopy. Some
of the most interesting SEM-photographs can be found in Appendix B: SEM pictures.
ii) The influence of the reaction parameters during the grafting, viz. absorbed dose,
moisture content, temperature, time, monomer concentration, moisture concentration
and pH, dependent on the method. The gathered data are collected in Appendix A:
Experimental data.
iii) Examination of some of the properties which are believed to be directly enhanced,
viz. thermal properties, hydrophilicity, adsorption properties.
iv) Investigation of one special application, i.e. the immobilization of β-cyclodextrin;
which is depending on the precedent grafting method.
v) On basis of i) - iv), a conclusion can be reached, allowing a detailed comparison
between PIG and SG of GMA on cotton, and its consequences for a subsequent
cyclodextrin immobilization This will logically form the finale of this work.
Nomenclature xxii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
NOMENCLATURE
Where possible, terms and units as defined by the International Union for Physics and
Applied Chemistry (IUPAC) and the International System of Units (SI) are used. They
are considered general knowledge and will not necessarily be explicitly mentioned in
the following list.
60Co = cobalt 60
AGU = anhydroglucose unit, or glucose residue
C(X) = the Xth carbon of the molecule, starting the numbering at the carbon with
the highest functional group (according to IUPAC)
CD = cyclodextrin
CX (M) = molar concentration of the substance X, thus in moles per liter
D = absorbed dose (in Gy)
DG = degree of grafting
DI = degree of immobilization
DMF = N,N-dimethylformamide
DP = degree of polymerization
DSC = differential scanning calorimetry
E = energy, expressed in joules (J)
eV = electron volt (1 eV = 1,602 10-19 J)
FTIR = fourier transform infrared
GMA = glycidyl methacrylate (or IUPAC: 2,3-epoxypropyl methacrylate)
Gy = gray (1 Gy = 1 J kg-1), SI unit of absorbed dose
Nomenclature xxiii
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
LET = linear energy transfer
m = mass
M = molarity (equal to moles per liter)
M:L = material to liquor ratio (in gram per liter)
M X = molar mass of the substance X
PGMA = poly(glycidyl methacrylate)
PIG = pre-irradiation grafting
S = swelling (in mass percent)
SEM = scanning electron microscopy
SG = simultaneous grafting
u = unified atomic mass unit, equal to one twelfth of the mass of an isolated
atom of 12C at rest and in its ground state, equal to 1,660 538 782 10−27 kg
v% = volume percentage
wt% = mass percentage
W0 = mass of the samples upon numbering, before any treatment
WCD = mass of the samples upon β-cyclodextrin immobilization
Wg = mass of the samples upon grafting
Ws = mass of the samples upon the swelling treatment
Wt = mass of the samples after grafting and β-cyclodextrin immobilization
β-CD = β-cyclodextrin
β-CDPM = β-cyclodextrin polymer
Literature survey 1
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
PART I: LITERATURE SURVEY
1 The characteristics of cotton-cellulose Understanding the structure of cellulose is a prerequisite towards controlling its modification,
so at least the main structural elements will be glanced through. The discussion will take place
on three levels: molecular, supermolecular and morphological; followed by how these structural
parameters affect the reactivity of the cellulose, which is of course paramount regarding further
reactions. An introduction sketching cellulose as a natural polymer originating from cotton will
precede this. Where possible, values are given, with the sole intention to give an idea of
magnitude.
1.1 Introduction to cellulose
Cellulose is the most abundant and renewable polymer on earth, being the structural
component in the cell wall of green plants. Cotton, hemp, flax, jute, ramie are the more
classical examples of cellulose sources, but also rice husks, wheat straws, banana peels,
etc. are possible (Takács, et al., 2010 10). Of all these sources, cotton is the most
important one; being the most produced natural textile fiber worldwide with 20,4 - 23,8
million metric tons, accounting for 38% of the global fiber consumption. The cotton
plant belongs to the Malvales order, family Malvaceae, tribe Gossypieae, and genus
Gossypium. Currently there are thirty-three different species recognized of which four
have commercial value, viz. hirsutum, barbadense, aboreum and herbaceum (Wakelyn,
et al., 2007 26, pp. 523-526). Of more importance is, however, that cotton is reported to
be the purest source of cellulose. After treatments to remove the naturally occurring
non-cellulosic materials, the cellulose content of the fiber is over 99% (Wakelyn, et al.,
2007 26, p. 537). Cotton fibers are long (25 mm or more) elongated single cells, growing
from the surface layers of the cotton seed and are also known as cotton lint. Along with
the lint also shorter fibers grow, which are known as linters. Those linters however are
from an inferior quality. In the scope of textile processing, cotton lint is used and will
also be the structure considered in everything that follows.
Literature survey 2
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
1.2 Molecular: The chemical structure
Chemically, cellulose is referred to as linear (1 → 4)-β-D-glucan (McNaught, 1996 27). A
glucan molecule is a polysaccharide of D-glucose monomers linked by glycosidic bonds.
The structural formula of cellulose is represented in Figure 1.
O
OH
OH OOH
OH
O
OH
OH O
OH
O
OH
OH OH
OHn-2
Figure 1: Structural formula of cellulose.
1.2.1 The monomer: β-D-glucopyranose
Glucose, with as chemical formula C6H12O6, is part of the aldohexose family. As
aldohexoses possess four chiral centers, this leads to 24 ( = 16) possible configurations.
Two of these stereoisomers are known as glucose, D-glucose and L-glucose, being
enantiomers (mirror images) of each other. Since L-glucose is not biologically active
and does not occur naturally, D-glucose is meant when speaking of simply glucose,
however not strictly correct. A common and clear way of picturing aldohexoses is via
the Fischer projection. The numbering of the carbons becomes also clear via this
projection, starting from the carbon C(1) with the preferred functional group, i.e. the
aldehyde group (McNaught, 1996 27), see also Figure 2.
1
2
3
4
5
6OH
O
H OH
OH H
H OH
H OH
23
45
6
1
OH
OH
OH
OH
O
OH
(a) (b)
Figure 2: Fischer projection (a) and stereo projection (b) of D-glucose.
Literature survey 3
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
D-glucose can exist in an open chain form, or in a cyclic form. Since in the open form an
aldehyde group exists on C(1), this form of glucose is also denoted as aldehydo-D-
glucose. Closing of the chain happens via a nucleophilic addition between the oxygen
atom on C(5) and C(1), creating a hemiacetal group (Du Prez, 2007 28). The resulting
cyclic aldohexose is referred to as a pyranose. Since stable molecules have bond angles
according to the tetrahedral configuration (109, 5°), the glucopyranose ring will not be
flat. Instead, glucopyranose exists in several puckered conformations (conformational
isomerism) in order to reduce angle strain to a minimum. The 4C1 is the most stable
conformation; this notation denounces that the molecule takes the shape of a chair with
C(4) above the plane of the ring (formed by C(2), C(3), C(5) and the ring oxygen) and
C(1) below (Rees, 1977 29, p. 14), see Figure 3 for an example. When the nucleophilic
addition takes place, two possibilities arise for the carbonyl group: the resulting
hydroxyl group (at C(1) thus) can orient itself cis or trans with the hydroxyl group on
C(4) which corresponds in the case of D-glucopyranose with α-D-glucopyranose
respectively β-D-glucopyranose (McNaught, 1996 27), see Figure 3. In the 4C1
conformation, this equals an axial, respectively equatorial orientation of the hydroxyl
group on C(1). Note that equatorial substituents cause less steric hindrance within the
molecule, which is why β-D-glucopyranose is thermodynamically more stable.
O
OH
OH OHOH
OH
O
OH
OH
OH
OH
OH
(a) (b)
123
4 5
6
123
4
6
5
Figure 3: Representation of α-D-glucopyranose (a) and β-D-glucopyranose (b) in the 4C1 conformation.
1.2.2 The polymer: Cellulose
The building units of cellulose are β-glucopyranose in the 4C1 conformation linked by
glycosidic bonds (O'Sullivan, 1997 30; Klemm, et al., 1998 31, p. 9). A glycosidic bond is a
bond between the hemiacetal group of a carbohydrate and the hydroxyl group of
another organic compound, which may or may not be another carbohydrate,
Literature survey 4
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
eliminating water and creating an acetal. In the case where the carbohydrate is glucose,
the term glucosidic bond is also in use by several authors (Wakelyn, et al., 2007 26; Princi,
et al., 2006 32). The linkage between the β-glucopyranose units in cellulose happens
between C(1) and C(4), this is denoted as a (1 → 4) linkage (McNaught, 1996 27). Note
that there will be an unreacted hydroxyl group at each chain end, viz. the C(1) end and
the C(4) end. These ends show clearly different behavior: the C(1) end is reducing
while the C(4) end is non-reducing (Wakelyn, et al., 2007 26, p. 547; Klemm, et al., 1998
31, p. 10). This is because the C(1) end contains a free hemiacetal group which can be
further oxidized. The chemical which would cause this oxidation becomes reduced
during this reacting. This end acts thus as a reducing agent. The other end of the chain
does not have this free hemiacetal group and is thus non-reducing. The reducing ends
are very reactive, but given the number of D-glucopyranosyl monomeric units in one
cellulose molecule, their relative share is rather small. During linkage, each monomer
loses one molecule of water; this is why they are referred to as anhydroglucose units
(AGUs) or glucose residues (C6H10O5), having a molar mass M = 162,15 g mol-1 These
units are oriented with alternating methylol (-CH2OH) groups above and below the
plane of the ring.
If the dimer cellobiose is taken as the basic unit instead of the glucose residue, which
some authors prefer (Wencka, et al., 2007 33; Zugenmaier, 2001 34), cellulose can be
considered as an isotactic polymer of cellobiose (Klemm, et al., 1998 31, p. 9), see also
Figure 4. This is however not really descriptive in any chemical sense, since hydrolysis
doesn’t yield dimers and tetramers rather than trimers and pentamers. Also when
talking about DP AGUs are used, so it seems more appropriate to work with the AGU
as a basic unit. When describing crystal structures however, this cellobiose
characterization can be useful, since the length of one cellobiose unit corresponds with
the crystallographic repeat along the fiber axis.
Literature survey 5
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
O
OH
OH OOH
OH
O
OH
OH OH
OHn
Figure 4: Representation of cellulose with cellobiose as repeating base unit.
1.2.3 Single chain conformation
The cellulose molecules form long and unbranched chains, viz. cellulose is a
syndiotactic (i.e. with alternating oriented substituents) homopolymer of β-D-
glucopyranose units (Klemm, et al., 1998 31, p. 9). This kind of shape can be described as
a helix, having two parameters describing its general contour: h and n (see Figure 5 for
a graphic explanation) respectively denoting the number of monomer units per turn of
helix and the projected length of each monomer on the helix axis (French and Johnson,
2004 35). The value of n is positive or negative in the case of, respectively, a right-
handed or a left-handed screw. For common crystalline cellulose, these parameters are
n = 2 and h = 5,18 Å (Wakelyn, et al., 2007 26, p. 552).
Figure 5: Sketch of a random helix to elucidate the meaning of n and h (Rees, 1977 29, p. 42).
These parameters arise because around the C(1)-O-C(4) bridge between succeeding
AGUs, there exists a rotation possibility around the C(1)-O bond (say φ) and around
the O-C(4) bond (say ψ), see Figure 6, making a single molecule very flexible.
n = 3
Literature survey 6
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
O
OHOH
O
OH
O
OH
OH
OH
Figure 6: A schematic representation of the rotation possibilities in the cellulose chain.
Four chain families arise depending on the values of n and h, the ribbon family, the
hollow helix family, the crumpled family and the loosely jointed family. Thermodynamically,
cellulose is most favored in the ribbon shape (Rees, 1977 29, pp. 42-54), which is reflected
in its crystal structures, cf. paragraph 1.3. Intramolecular hydrogen bonds i) between
the hydroxyl group on C(3) and the pyranose ring oxygen of a following
glucopyranose unit in the chain and ii) between the hydroxyl groups on C(6) and C(2)
of neighboring glucopyranose units in the same chain, stabilize this shape and are
responsible for the considerable stiffness, see Figure 7.
O
OH
OH O
OH
O
OH
OH O
OH
O
OH
OH O
OH
O
OH
OH
OH
Figure 7: Intramolecular hydrogen bonds stabilizing the cellulose chain.
1.2.4 Degree of polymerization and molar mass distribution
The size of one molecular entity is defined by its chain length, which is expressed as
degree of polymerization (DP). The molar mass can then be calculated as the product
of the DP with the mass of the repeating AGU (1 AGU = 162,14 u). Cellulose
originating from native sources is polydisperse (Klemm, et al., 1998 31, pp. 11-13) and
there is thus a broad molar mass distribution (Lin, et al., 2009 36), the length of one
chain can go up to 15.000 (O'Sullivan, 1997 30) or even 20.000 (Wakelyn, et al., 2007 26,
pp. 544, 546) glucopyranose units, according to the source. Both the DP (taken as an
average) and, possibly even more, the molar mass distribution have a big impact on the
Literature survey 7
Functionalization of cotton-cellulose via high energy Gilles Desmet
irradiation initiated grafting and cyclodextrin immobilization
properties of the polymer. In general: the higher the DP and the narrower the molar
mass distribution, the stronger the polymer.
1.3 Supermolecular: The crystal structure
Besides the intramolecular hydrogen bonds, which play a big role in the single chain
conformation, also intermolecular hydrogen bonds, between the hydroxyl groups on
C(3) and C(6) of an adjacent molecule in the same plane (Roy, et al., 2009 1), exist, see
Figure 8. This hydrogen bonding mainly takes place between hydroxyl groups which
are located on the edges of the cellulose ribbon and are responsible for the tendency of
the cellulose chains to order themselves into long sheets, along the axis of the fibrillar
super unit (the microfibril, cf. 1.4.1). Next to those hydrogen bonds, also extensive Van
der Waals interaction is reported. These Van der Waals interactions happen between the
flat sides of the ribbons and cause the stacking of the sheets in the direction
perpendicular on the fibrillar axis. This high level of intermolecular interaction causes a
very efficient and high density arrangement (up to 1,62 g cm-³); which explains the
remarkable insolubility of cellulose in most solvents; since they must be able to disrupt
the extremely strong network of both hydrogen bonding and Van der Waals