L-cysteine-induced fabrication of spherical titania nanoparticles within poly(ether-imide) matrix

Article abstract of DOI:10.1007/s00726-014-1695-1

In the presented study, a new l-cysteine-containing diamine is synthesized and fully characterized and its application for the in situ sol-gel fabrication of poly(ether-imide)/titania nano hybrid materials is investigated. The electron microscopic photographs (TEM, FE-SEM and AFM) of the resulted materials confirm the production of spherical nanoparticles with well dispersion and narrow particle size distribution which is a usual challenge in the sol-gel methods. In addition to the positive effects on the particles morphology, the existence of amino acid containing pendant groups in the structure of polymer chains led to the comprehensive interaction with titania phase. As a result, the improvement in the flexibility of polymer backbone (as one of the most serious difficulties in polyimides processing) is obtained while its thermal stability dose is not sacrificed (confirmed by TGA and DSC techniques).

Full text of DOI:10.1007/s00726-014-1695-1

Amino Acids
DOI 10.1007/s00726-014-1695-1
ORIGINAL ARTICLE
L-cysteine-induced fabrication of spherical titania nanoparticles
within poly(ether-imide) matrix
•
Hojjat Seyedjamali Azadeh Pirisedigh
Received: 20 November 2013 / Accepted: 8 February 2014
Ó Springer-Verlag Wien 2014
Abstract In the presented study, a new L-cysteine-con-
taining diamine is synthesized and fully characterized and
its application for the in situ sol–gel fabrication of poly
(ether-imide)/titania nano hybrid materials is investigated.
The electron microscopic photographs (TEM, FE-SEM and
AFM) of the resulted materials confirm the production of
spherical nanoparticles with well dispersion and narrow
particle size distribution which is a usual challenge in the
sol–gel methods. In addition to the positive effects on the
particles morphology, the existence of amino acid con-
taining pendant groups in the structure of polymer chains
led to the comprehensive interaction with titania phase. As a
result, the improvement in the flexibility of polymer back-
bone (as one of the most serious difficulties in polyimides
processing) is obtained while its thermal stability dose is not
sacrificed (confirmed by TGA and DSC techniques).
or biocompatibility (Liang et al. 2011; Bao et al. 2013; Wu
et al. 2007; Singh and Lilard 2009; Xue et al. 2011; Park
et al. 2013a). With the rapidly growing applications of
polymer/inorganic nano hybrid materials in various areas
from aerospace industry to tissue engineering, their biotic
modification seems to be promising (Kango et al. 2013;
Park et al. 2013b; Okamoto and John 2013). Among the
artificial materials, polyimides (PIs) and PI matrix nano-
composites possess the specific situations due to their
excellent thermal, chemical, mechanical, optical and
dielectric properties (Liaw et al. 2013; Xiao et al. 2009;
Jang et al. 2007). The combination of excellent physico-
chemical properties of PIs and multi-functionalistic nature
of titania (TiO2) provides one of the most important classes
of modern materials with versatile applications, especially
when titania is nanosized, low aggregated, well-graded and
spherical in shape (Lee et al. 2009; Tsai et al. 2008; Missan
et al. 2010; Rajesh et al. 2013). The homogenization of
intrinsically dissimilar polymer-inorganic couples, which
affects intensively the particles morphology, is attainable
via either the chemical modification of inorganic nano-
particles (e.g., the use of silane linkages) or utilization of
the polymers suitable to construct the physical interactions
in organic–inorganic interfaces, namely, the site isolation
concept (Yoshida et al. 1997).
Keywords L-cysteine ꢀ Poly(ether-imide) ꢀ Titania ꢀ
Sol–gel ꢀ Morphology
Introduction
The insertion of naturally occurring species into the
chemical structure of artificial materials is a powerful
strategy to increase their biodegradability, bioactivity and/
The in situ sol–gel technique is a powerful and of course
straightforward method for the fabrication of nanoparticles
within the polymer grounds by means of site isolation con-
cept; however, it typically suffers from the production of
non-spherical particles with limited size gradation due to the
low organic–inorganic compatibility (Cao et al. 2013; Pan-
dini et al. 2013; Morselli et al. 2012). On the other hand, the
insertion of traditional bulky pendant groups in the structure
of PIs—to overcome their general low processability—may
worsen the organic–inorganic compatibility and disrupt the
H. Seyedjamali (&)
Department of Environmental Engineering, University of
Environment, 31746-74761 Karaj, Islamic Republic of Iran
e-mail: seyedjamali@yahoo.com
A. Pirisedigh
Department of Chemistry and Petrochemical Engineering,
Standard Research Institute, 31745-139 Karaj,
Islamic Republic of Iran
123

H. Seyedjamali, A. Pirisedigh
consistency in the morphology of inorganic nanoparticles as
they increase the hydrophobicity of PI matrixes (Song et al.
2013; Vanherck et al. 2013; Seyedjamali and Pirisedigh
2012a).
vacuum oven at 125 °C overnight. N,N-dimethylformam-
ide (DMF) was dried over barium oxide, followed by
fractional distillation. Tetraethyl orthotitanate (Ti(OEt)4)
and acetylacetone (acac) were employed as received.
Recently, we have reported the in situ synthesis of
titania nanoparticles within a polymer matrix including
L-leucine as a fraction of polyimide main chains (Seye-
djamali and Pirisedigh 2011a). In a separate work, we
examined the incorporation of amino acids in the chemical
structure of pendant groups which gave improved results in
terms of better dispersion and created nanoparticles with
more spherical shapes attributed to the more flexibility of
pendant groups (Seyedjamali and Pirisedigh 2011b). Since
the later investigation had been carried out using L-phen-
ylalanine, we did a third study on the use of L-leucine as a
fraction of pendant groups and the experiments proved the
superior results not only due to the more elasticity of
pendant groups regiochemistry but also to the additional
flexibility of L-leucine in comparison with L-phenylalanine
(Seyedjamali and Pirisedigh 2012b). L-cysteine as the only
naturally occurring amino acid containing—SH functional
group has the ability to bind more effectively to the variety
of metals and metal oxides (Su et al. 2010; Lv et al. 2012).
The binding nature could be a combination of thiolate
formation, (-S-metal), H bond or simple dipole–dipole
interactions (Muir and Idriss 2013; Ataman et al. 2011;
Lachheb et al. 2012). In addition, the secondary interaction
of thiol group with the surface plays an important role on
the interaction strength (Muir and Idriss 2013; Ataman
et al. 2011). Thus, as the extension of our investigations,
we decided to use L-cysteine fractions in the pendant group
of PI matrix. Herein, we wish to report the full synthesis
and characterization of a new L-cysteine containing dia-
mine monomer and its application for the in situ sol–gel
fabrication of new poly(ether-imide)/titania nano hybrid
materials with superior particles morphology in terms of
their shapes, dispersion and grading. Although the exis-
tence of naturally occurring amino acids in the structure of
polymers may increase their biological activities (Katsar-
Instruments
Proton nuclear magnetic resonance (1H-NMR, 500 MHz
and 13C-NMR, 125 MHz) spectra were recorded in
DMSO-d6 solution using a Bruker (Germany) Avance 500
instrument. FT-IR spectra were recorded on 400D IR
spectrophotometer (Japan). The spectra were obtained
using KBr pellets. The vibrational transition frequencies
are reported in wave numbers (cm-1). Band intensities are
assigned as weak (w), medium (m) and strong (s). Thermal
gravimetric analysis (TGA) data were taken on Perkin
Elmer in nitrogen atmosphere at a heating rate of
20 °C min-1. Differential scanning calorimetry (DSC) data
were recorded on a DSC-PL-1200 instrument at a heating
rate of 20 °C min-1 in nitrogen atmosphere. The glass
transition temperatures (Tg)s were read at the middle of the
transition in the heat capacity taken from the heating DSC
traces. The X-ray diffraction (XRD) patterns were recorded
by employing a Philips X’PERT MPD diffractometer (Cu
Ka radiation: k = 0.154056 nm at 40 kV and 30 mA) over
the 2h range of 20–80° at a scan rate of 0.05° min-1
.
Transmission electron microscopy (TEM) images were
recorded using a JEOL JEM-2000 operating at 200 kV.
Field emission scanning electron microscopy (FE-SEM)
was acquired by JEOL JSM-6700S Japan operating at an
accelerating voltage of 1.5 or 5.0 kV. The sample was
prepared by drop casting an acetone suspension onto mica
substrate and then coated with gold. Atomic force
microscopy (AFM) topographic images were obtained
using Digital Multimode Instruments Nanoscope III (Dig-
ital Instrument Inc., USA) with noncontact tapping mode
with a silica probe (NSC 11) and a frequency of 463 kHz.
UV–visible absorbance spectra were obtained from Perkin
UV–VIS lambda 850 spectrometer.
¨
ava 2003; Aıt-Haddou et al. 2004; Sanda and Endo 1999),
the investigations of this potential biological are not the
subject of current report.
Synthesis of aromatic diamine monomer
Methyl 2-(3,5-dinitrobenzamido)-3-mercaptopropanoate
(3) synthesis
Materials and methods
Although, a production pathway has been reported previ-
ously for compound 3 (Metais et al. 1997), our synthesis
was based on the procedure described as follows: to a
chloroform (50 mL) solution of 3.0 g (17.5 mmol) 3,5-
dinitrobenzoyl chloride (2), 4.03 g (17.5 mmol) of L-cys-
teine methyl ester hydrochloride (1) and 4 mL of Et3N
were added and stirred at room temperature until the
complete conversion monitored by TLC (50:50
Materials
All chemicals were purchased from Fluka Chemical Co.
(Buchs, Switzerland), Aldrich Chemical Co. (Milwaukee,
WI), Riedel–deHaen AG (Seelze, Germany) and Merck
Chemical Co. 4,40-oxydiphthalic anhydride (ODPA) was
recrystallized from acetic anhydride and then dried in a
123

L-cysteine-induced fabrication
ethylacetate:n-hexane). Then, the mixture was washed with
distilled water for three times. After that the organic phase
was separated and dried over calcium chloride, the dinitro
compound (3) was precipitated by rotary evaporation of
chloroform and recrystallized from ethylacetate/n-hexane
vacuum dried (3.9 g, 93 %). mp 184–187 °C (dec.),
½aꢁD = ?23.1 (0.05 g in 10 mL of DMF). FT-IR (KBr):
25
3,441 (m), 3,363 (m), 3,295 (s), 3,212 (s), 3,160 (s), 3,101 (s),
3,072 (m), 2,967 (m), 2,618 (m), 2,557 (m), 2,503 (m), 1,690
(s), 1,671 (s), 1,604 (s), 1,505 (s), 1,445 (m), 1,281 (s), 1,253
(s), 1,072 (m), 1,036 (m), 1,019 (m), 921 (w), 869 (w), 802
(m), 721 (s), 694 (m), 653 (m) cm-1. 1H-NMR (500 MHz,
DMSO, d6): d 1.46 (s, 1H, SH), 3.29 (d, 1H, CH,
J = 6.47 Hz), 3.52 (d, 1H, CH, J = 5.94 Hz), 4.93 (dd,
J1 = 7.63, J2 = 6.15, 1H, CH), 5.51 (s, 4 H, NH2), 6.05 (s,
1H, Ar–H), 6.62 (s, 2H, Ar–H), 7.59–7.67 (m, 5H, Ar–H),
1
(5.24 g, 91 %). H-NMR, 13C-NMR and the other char-
acterization details have been reported previously (Metais
et al. 1997).
N-(3-mercapto-1-oxo-1-(phenylamino)propan-2-yl)-3,5-
dinitrobenzamide (4) synthesis
8.81 (s, 1H, amide NH), 9.49 (s, 1H, amide N–H) ppm. 13
C
A 50-mL round-bottomed flask equipped with a reflux
condenser was charged with 5 g of compound dinitro 3
(15.2 mmol), 1.5 mL of freshly distilled aniline (1.53 g;
16 mmol) and 10 mL of DMF and refluxed overnight.
Then, DMF was removed under reduced pressure and the
precipitate was washed with 0.5 M aqueous solution of
HCl (50:1 v/v) to precipitate 4 as a yellow powder which
was washed with distilled water and vacuum dried (5.3 g,
NMR (125 MHz, DMSO-d6), d (ppm): d 35.72 (CH2), 54.55
(CH), 102.11 (Ar), 103.64 (Ar), 122.13 (Ar), 129.45 (Ar),
130.07 (Ar), 135.12 (Ar), 136.19 (Ar), 149.65 (Ar), 167.73
(C=O), 172.38 (C=O) ppm. Elemental analysis calculated
for C16H18N4O2S (330.40 g mol-1): C, 58.16 %, H, 5.49 %,
N, 16.96 %. Found: C, 57.94 %; H, 5.68 %; N, 16.62 %.
Fabrication of NCs
25
90 %) mp 152–153 °C,½aꢁD = ?64.7 (0.05 g in 10 mL of
DMF); FT-IR (KBr): 3,343 (m), 3,100 (m), 3,070 (m),
2,967 (m), 2,620 (m), 2,555 (m), 2,498 (m), 1,692 (s),
1,673 (s), 1,601 (s), 1,503 (s), 1,447 (m), 1,280 (s), 1,255
(s), 1,069 (m), 1,035 (m), 1,020 (m), 919 (w), 865 (w), 801
A 25-mL round-bottomed flask was charged with 3.5 g of
diamine 5 (10.6 mmol) and 22 mL of DMF was added to
dissolve the diamine compound completely. The solution
was cooled to 0 °C and 3.29 g of ODPA (10.6 mmol) was
added in several portions and stirred for 1 h at 0 °C and 2 h
at room temperature under N2 atmosphere, to yield the
poly(amic acid) (PAA) solution. (Ti(OEt)4) was dissolved
in acac with a molar ratio of 1:4 prior to use. Then,
according to the wanted titania percentages (3–15 wt%),
the required amounts of Ti(OEt)4/acac were added,
assuming the complete conversion to TiO2 particles. The
homogenization was carried out with vigorous stirring for
15 h. Then, thin films of mixed PAA containing various
titanate precursors were cast onto the glass plates. Obtained
films were annealed in an electric oven at 50, 75, 100, 125,
150, 175, 200, 225, and 250 °C for 30 min each and
300 °C for 10 h and then were cooled very slowly and
removed from glass surfaces. Abbreviations as PEI/T0,
PEI/T3, PEI/T5, PEI/T10 and PEI/T15 corresponded to the
pure polymer matrix and nanocomposites containing
3–15 wt% titania contents, respectively.
1
(m), 718 (s), 691 (m) cm-1. H-NMR (500 MHz, DMSO,
d6): d 1.47 (s, 1H, SH), 3.27 (d, 1H, CH, J = 6.33 Hz),
3.50 (d, 1H, CH, J = 6.07 Hz), 4.91 (dd, J1 = 7.55,
J2 = 6.21, 1H, CH), 9.04 (s, 1H, Ar–H), 9.13 (s, 2H, Ar–
H), 7.63–7.71 (m, 5H, Ar–H), 8.97 (s, 1H, amide NH), 9.50
(s, 1H, amide N–H) ppm. 13C-NMR (125 MHz, DMSO,
d6): d 35.44 (CH2), 54.93 (CH), 102.15 (Ar), 103.23 (Ar),
122.15 (Ar), 129.44 (Ar), 129.91 (Ar), 135.19 (Ar), 136.48
(Ar), 151.74 (Ar), 167.22 (C=O), 172.37 (C=O) ppm.
Elemental analysis calculated for C16H14N4O6S
(390.37 g mol-1): C, 49.23 %; H, 3.61 %; N, 14.35 %.
Found: C, 49.05 %; H, 3.85 %; N, 14.17 %.
3,5-Diamino-N-(3-mercapto-1-oxo-1-
(phenylamino)propan-2-yl)benzamide (5) synthesis
In a 50-mL two necked round-bottomed flask equipped with
a reflux condenser and a dropping funnel, 5 g of dinitro
compound 4 (12.8 mmol), 0.5 g of Pd–C 10 % and 20 mL of
DMF were added and heated slowly until 50 °C. Then,
25 mL of ethanol solution of hydrazine monohydrate 80 %
(1:1 v/v) was added slowly (over 60 min) via the dropping
funnel and the mixture was stirred vigorously. After the
complete addition of hydrazine monohydrate, the mixture
was refluxed for 1 h and filtered while hot. Diamine 5 was
obtained by removal of DMF under reduced pressure. The
products were recrystallized from absolute ethanol and
Results and discussion
Monomer synthesis and characterization
L-cysteine-containing diamine monomer (5) was synthe-
sized according to the sequence shown in Scheme 1.
Methyl ester derivative of L-cysteine was used due to the
limited organosolubility of its corresponding carboxylic
123

H. Seyedjamali, A. Pirisedigh
O
different quantities of tetraethyl orthotitanate/acac to form
the homogeneous solutions as the sol (Scheme 2). The role
of acac is to prevent the fast conversion to the gel which leads
to the fabrication of nanoparticles with more consistency.
After the film production via evaporation of the solvent from
glossy surfaces, the crude materials were annealed up to
300 °C. During the thermal treatment, the amic acid frac-
tions were converted to the imide functions and generated
water—as the condensation byproduct—turned the titanate
precursor into the titania particles. The deliberate bit by bit
heating and cooling of materials through the fabrication
process let the titania particles to form the more spherical
shapes. It was verified that the fast thermal operation has the
reverse consequences on the geometric order of the created
particles. Furthermore, the existence of several functions in
the chemical structure of polymer matrix with the ability to
interact with inorganic phase has definite results on the
particles morphology.
O2N
NO2
O2N
NO2
NH3 Cl
CH2
SH
1
CHCl3
Et3N
H3CO
O
O
Cl
NH
HSH2C
O
3
2
OCH3
O2N
NO2
H2N
NH2
Ph-NH2
N2H4.H2O
Pd-C
3
O
O
DMF/
Reflux
NH
NH
HSH2C
O
HSH2C
O
NH
Ph
NH
Ph
5
4
Scheme 1 Synthesis of L-cysteine containing diamine monomer (5)
acid compound. In the next step, ester functional group was
converted to amide using overnight refluxing with aniline.
This transformation leads to the more capability of diamine
to construct H bond lattice via amide protic sites.
According to the high tendency of species including thiol
functions for metal catalyzed disulfide bond formation
especially in the presence of humidity and/or oxygen (Mezyk
1995; Leong et al. 2013), the materials were kept away from
both external moisture and air. However, solubility tests
showed the small decrease in the solubility of fabricated
materials with the increase in titania contents attributable to
the creation of partials disulfide cross links between polymer
chains and/or two pendant groups of a particular chain
(Fig. 4). Possible mechanism (Fujii et al. 1987) for the
intermolecular and intramolecular metal-mediated disulfide
bonds formation is presented in scheme 3.
In FT-IR spectrum of diamine 5 (Fig. 1), the strong
absorption peaks appeared at 1,690 and 1,671 cm-1 are
related to the stretching of two carbonyl double bonds
related to the amide functional groups. The absorption
peaks related to the amine and amide NH bonds are
1
observable at 3,200–3,450 cm-1. Full assignments of H-
NMR and 13C-NMR spectrums are presented in Figs. 2 and
3, respectively, which show full agreement with the
chemical structure of diamine 5.
Spectroscopic study of nano hybrid materials
Nanocomposites fabrication
The confirmation of thermal cyclization of amic acid
moieties to imide functions is demonstrable via either FT-
IR spectra or TGA experiments. In the FT-IR spectrums of
PAA (Fig. 5), the broad absorption peak at
Diamine 5 was reacted with ODPA in dry DMF at room
temperature for the fabrication of the corresponding
poly(amic acid) (PAA) which subsequently was mixed with
Fig. 1 FT-IR spectrum of
diamine monomer 5
123

L-cysteine-induced fabrication
Fig. 2 1H-NMR spectrum of
diamine monomer 5
Fig. 3 13C-NMR spectrum of
diamine monomer 5
2,350–2,550 cm-1 refers to the carboxylic acid functions
which disappeared after thermal operation (PEI/T0 or PEI/
T10) confirming the complete imidization. The absorption
peaks related to the stretching of imide ring are assigned in
Fig. 5. The FT-IR spectrum of PEI/T10 is illustrated rep-
resentatively which shows a strong absorption peak related
to the titania phase (Ti–O stretching). The other noticeable
absorption peaks are the stretching of thiol S–H bond
which appear at 2,598 cm-1 for PEI/T0 indicating the free
S–H bond and at 2,489 cm-1 for PEI/T10 attributable to
the S–H bond involved in the interaction with TiO2 phase.
The FT-IR spectra of the other fabricated hybrid materials
were more or less the same.
The UV–Vis spectroscopy of fabricated nanocomposites
was carried out as well. Accordingly, the more titania
contents have led to the fewer UV transmission percent
(Fig. 6). The more absorption efficiency could be discussed
by both more aggregation of titania particles and formation
123

H. Seyedjamali, A. Pirisedigh
Scheme 2 Fabrication
sequences for nano hybrid
materials with different titania
contents
O
O
H2N
NH2
H
N
H
N
O
n
O
O
O
HO2C
CO2H
O
O
O C
NH
O C
NH
HSH2C
O
O
O
PAA
ODPA
HSH2C
O
1) Ti(OEt)4 / acac
(1:4)
2) Film Casting
3) Annealing
Dry DMF
RT
NH
Ph
NH
Ph
O
N
O
N
O
N
O
O
O
N
O
O
O
O
C O
C O
O C
NH
HS
SH
NH
HN
HO OH
OH
HS
HO
OH
HO
OH
TiO2
TiO2
OH
HO
HO
OH
OH
O
OH
HO
NH
O
O
HN
NH
HO OH
photoelectrochemical applications, photocatalysts, optical
filters and antireflective coatings (Li et al. 2002, 2013;
Chang et al. 2009; Tsai et al. 2008, 2006; Liaw and Chen
2007; Chiang and Whang 2003; Chen et al. 2014; Ehsani
et al. 2014; Li and Ni 2013; Muthirulan et al. 2013; Gupta
et al. 2013).
Fig. 4 Hypothetical schema representing of disulfide cross-link
formation
Morphological study
Various apparatus were applied to investigate the size,
sized distribution, shape and grading of nanoparticles cre-
ated within the polymer matrix through the sol–gel process.
Although the sol–gel technique provides a straightforward
method for producing of nanoparticles, it suffers the weak
control of their morphology. Thus, the introduction of new
strategies for modification of this method is promising. The
TEM photographs of nanocomposites with various titania
concentrations are provided in Fig. 7. As it may be seen,
the well-dispersed and spherical nanoparticles are created
specially in the lower titania contents.
of titanium ion–acac complex (Liaw and Chen 2007; Que
et al. 2000). However, the complex mechanism may be
negligible, subsequent to the gelation step. Although the
color of resulted materials was ranged from yellow (in PEI/
T3) to brown (in PEI/T15), all the materials were com-
pletely transparent. While they block out the lights with
higher frequency, like a sun glass, the visible region of
light spectrum is transparent. This behavior could be useful
for the applications where the polymer/titania nano hybrid
materials are used for absorption of UV irradiations, e. g.
Scheme 3 Proposed
mechanism for
S
S
S
S
(i) intramolecular and
(ii) intermolecular disulfide
bonds formation
Ti
(i)
-EtOH
EtO
OEt
Ti(OEt)4
-EtOH
S
SH
HS
SH
-EtOH
(ii)
HS
EtO Ti OEt
OEt
S
S
S
OEt
OEt
Ti
S
123

L-cysteine-induced fabrication
2007; Chiang and Whang 2003; Seyedjamali and Pirise-
digh 2011a, b; Seyedjamali and Pirisedigh 2012a, b).
Figure 9 illustrates the FE-SEM photograph of PEI/T5
as a representative issue as well as graphical illustration of
organic/inorganic interaction and the severe tendency of
poly(ether-imide) back bone to wrap the titania nanopar-
ticles. In addition to the H bonds or dipole–dipole inter-
actions, the use of ODPA as a dianhydride monomer
including a flexible ether function and the existence of
bulky pendant groups including aliphatic fractions in the
structure of monomer may be the other facilitators for
surrounding titania particles more efficiently.
The investigation of surface topography was done using
AFM imaging technique too. The observable convexities in
the AFM image of PEI/T3 (Fig. 10) which are attributed to
the titania nanoparticles reveal that (a) nanoparticles are
created not only in the ventricle of nanocomposite but also
in its surface, and (b) surface nanoparticles are well-dis-
persed and relatively spherical in shape.
Fig. 5 FT-IR spectra of PAA, PEI/T0 and PEI/T10 as the examples
The XRD analysis was performed to verify the crystal-
linity of nano hybrid materials. The typical XRD patterns
for pure anatase titania PEI/T0 and PEI/T10 are presented
in Fig. 11. The peaks appeared at 2h = 16.0°, 19.2° and
19.9° are related to the diffractions of partial crystalline
poly(ether-imide) matrix. The absence of these peaks in the
spectra of hybrid materials (e.g., PEI/T10) could be
attributed to the tough organic–inorganic interaction which
suppresses the fractional crystallinity of polymer matrix
and flatten the bulging section of XRD patterns.
Thermal properties
The thermal analyses of fabricated nano hybrid materials
were done using TGA and DSC experiments which are
presented in Fig. 12 and Table 1, respectively. Accord-
ingly, the fabricated nanocomposites with higher titania
contents showed elevated thermal resistances by means of
T5, T10, Tg and char yields.
Fig. 6 UV–vis spectra of PEI/T0-PEI/T15
According to the sized distribution diagrams (Fig. 8),
the fine particles grading is obtained which may be
attributed to the comprehensive organic–inorganic inter-
actions and the control of the reaction rate in the gelation
step by means of both the slow thermal imidization and the
use of acac as the chelating agent. The use of L-cysteine
containing diamine monomer including several protic
(amide NH and SH fractions) and dipolar (carbonyl groups)
functionalities has led to form a three-dimensional network
of organic–inorganic interactions. The site isolation con-
cept (Yoshida et al. 1997) in a widespread state is
responsible for the more geometrical ordering and well
dispersion as well as the narrow particle size distributions.
In comparison with the similar investigations, the presented
PI could be considered as a beneficial matrix for the in situ
sol–gel fabrication of TiO2 nanoparticles in terms of the
superior distribution, more consistency and spherical par-
ticles morphology (Tsai et al. 2008, 2006; Liaw and Chen
A large descend in the thermogram of PAA is apparent
which is attributed to the generation of H2O molecules
along with the thermal imidization. This thermogram
returns to the flat pattern at 300 °C confirming the com-
plete imidization. This observation is in agreement with the
FT-IR data where the strong broad carboxylic acid peak in
the spectrum of PAA was omitted in PEI/T0 which proves
the complete imidization spectroscopically. This tempera-
ment was observed in FT-IR spectra of the other entries
(only PEI/T10 is shown) as a result of the comprehensive
thermal imidization of amic acid moieties. A comparison
between the TGA thermograms (Fig. 12) of PEI/T0 and
PEI/T3-PEI/T15 shows that there is a relatively large gap
between the thermal stabilities of pure polymer matrix
(b) and the other nano hybrid materials (c–f) whereas the
123

H. Seyedjamali, A. Pirisedigh
Fig. 7 TEM photographs of nanocomposites with 3 % (a), 5 % (b), 10 % (c) and 15 % (d) titania contents
phase as an intrinsically more heat resistant fraction,
otherwise a linear relationship between the concentration
of titania and thermal stability should be observed. Fur-
thermore, the Tg amount (193 °C) for pure PI matrix shows
that it enjoys more processability while the comparison of
its T5, T10 and CY with those in PEI/T3 confirms the
positive and intensive effects of inorganic phase on the
compensation of thermal stability. The growth of Tg values
with the increase in titania concentration could be dis-
cussed by more limited segmental movements caused by
the strong L-cysteine-titania interaction in the materials
with more titania contents.
Fig. 8 Particle size distribution diagrams for fabricated nano hybrid
materials
Conclusions
difference between the nano hybrid materials (c–f) is
slighter. This observation reveals that the origin of the
thermal stability is the construction of organic/inorganic
interactions and not merely the existence of inorganic
A new L-cysteine containing diamine monomer is synthe-
sized and fully characterized via spectroscopic and ele-
mental analysis techniques. The application of the stated
diamine for the in situ sol–gel fabrication of a new series of
123

L-cysteine-induced fabrication
Fig. 12 TGA thermograms of PAA, pure polymer matrix and PEI/
T3-PEI/T15
Table 1 Thermal analysis of nanocomposites
Material
Ta5 (°C)
Tb10 (°C)
Tg (°C)
CYc (%)
PEI/T0
PEI/T3
PEI/T5
PEI/T10
PEI/T15
417
468
473
476
478
422
538
544
548
551
193
244
249
257
262
46
69
73
75
79
Fig. 9 Typical FE-SEM image of PEI/T15
TGA; at heating rate of 10 °C min-1 and DSC; at heating rate of
20 °C min-1 in nitrogen atmosphere
a
Decomposition temperature for 5 % weight loss
b
Decomposition temperature for 10 % weight loss
c
Char Yields, weight percentage of material left undecomposed at
800 °C
shape of nanoparticles in a sol–gel manner is achieved
while the thermal stability of PIs was not sacrificed. The
significance of this achievement refers to:
(a) An improvement in processability as a sever chal-
lenge associated with the PIs applications is done
without the increase in the organic nature of
polymer.
Fig. 10 Exemplar AFM topographic image of PEI/T15
(b) L-cysteine-induced improvement in the control of
nanoparticles morphology as the most serious prob-
lem of the sol–gel manners offers a powerful, simple
and inexpensive way for the in situ fabrication of
nanocomposite materials.
(c) With the high and increasing consumptions of PI/
titania nano hybrid materials in various modern areas,
the presentation of their superior varieties is
promising.
Fig. 11 XRD patterns of anatase titania, pure polymer matrix and a
typical nanocomposite
(d) The usual destructive effects of pendant groups on
the thermal stability of PIs are compensated via the
construction of strong interaction with inorganic
phase which has an exciting coincident as the more
spherical and well-distributed nanoparticles.
PI/titania nanocomposites with the improved morphologi-
cal features is reported. In comparison with the similar
works the perfection in grading, dispersion and the globular
123

H. Seyedjamali, A. Pirisedigh
Lee C, Kim I, Shin H, Kim S, Cho J (2009) Nonvolatile resistive
switching memory properties of thermally annealed titania
precursor/polyelectrolyte multilayers. Langmuir 25:11276–11281
Leong JX, Daud WRW, Ghasemi M, Liew KB, Ismail M (2013) Ion
exchange membranes as separators in microbial fuel cells for
bioenergy conversion: a comprehensive review. Renew Sustain
Energy Rev 28:575–587
Li F, Ni X (2013) Improving poly(3-hexylthiophene)-TiO2 hetero-
junction solar cells by connecting polypyrrole to the TiO2
nanorods. Sol Energy Mater Sol Cell 118:109–115
(e) Due to the existence of L-cysteine moieties in the
structure of PI matrixes, they expected to show
biological activities which could be the subject of
further investigations.
Acknowledgments Financial support for this work from Research
Affairs Division University of Environment; Standard Research
Institute and Iran nanotechnology Initiative Council and National
Elite Foundation (NEF) is greatly acknowledged.
Li L, Qinghua L, Jie Y, Xuefeng Q, Wenkai W, Zikang Z, Zongguang
W (2002) Photosensitive polyimide (PSPI) materials containing
inorganic nano particles (I)PSPI/TiO2 hybrid materials by sol–
gel process. Mater Chem Phys 74:210–213
Conflict of interest The authors declare that they have no com-
peting financial interests.
Li Z, Gan M, Qiu W, Fu D, Li S, Bai Y (2013) Synthesis and
anticorrosion performance of poly(2,3-dimethylaniline)–TiO2
Composite. Prog Org Coat 76:1161–1167
References
Liang JZ, Tang CY, Zhou L, He L, Tsui CP (2011) Melt density and
flow property of PDLLA/nano-CaCO3 bio-composites. Compos
B 42:1897–1900
Liaw CW, Chen KP (2007) Preparation and characterization of
poly(imide siloxane) (PIS)/titania(TiO2) hybrid nanocomposites
by sol–gel processes. Eur Polym J 43:2265–2278
Liaw DJ, Wang KL, Huang YC, Lee KR, Lai JY, Ha CS (2013)
Advanced polyimide materials: syntheses, physical properties
and applications. Prog Polym Sci 37:907–974
Lv K, Hu J, Li X, Li M (2012) Cysteine modified anatase TiO2 hollow
microspheres with enhanced visible-light-driven photocatalytic
activity. J Mol Catal A Chem 356:78–84
¨
Aıt-Haddou H, Leeder SM, Gagne MR (2004) Amino-acid containing
metallomonomers copolymerized into porous organic polymers:
applicability to allylic alkylation catalysis. Inorg Chim Acta
357:3854–3864
Ataman E, Isvoranu C, Knudsen J, Schulte K, Andersen JN, Schnadt J
(2011) Adsorption of L-cysteine on rutile TiO2(110). Surf Sci
605:179–186
Bao Y, Shen G, Liu H, Li Y (2013) Fabrication of gold nanoparticles
through autoreduction of chloroaurate ions by thermo- and pH-
responsive amino acid-based star-shaped copolymers. Polymer
54:652–660
Metais E, Overman LE, Rodriguez MI, Stearns BA (1997) Halide-
terminated N-acyliminium ion-alkyne cyclizations: a new con-
struction of carbacephem antibiotics. J Org Chem 62:9210–9216
Mezyk SP (1995) Direct rate constant measurement of radical
disulphide anion formation for cysteine and cysteamine in
aqueous solution. Chem Phys Lett 235:89–93
Cao J, Zhu Q, Dou J, Li C, Chen W, Li Z (2013) Controlling sol-gel
polymerization to create bowl-shaped polysilsesquioxane parti-
cles with a kippah structure. Polymer 54:2493–2497
Chang WL, Su HW, Chen WC (2009) Synthesis and properties of
photosensitive polyimide–nanocrystalline titania optical thin
films. Eur Polym J 45:2749–2759
Missan HPS, Lalia BS, Karan K, Maxwell A (2010) Polymer–ionic
liquid nano-composites electrolytes: electrical, thermal and
morphological properties. Mater Sci Eng B 175:143–149
Morselli D, Bondioli F, Sangermano M, Messori M (2012) Photo-
cured epoxy networks reinforced with TiO2 in situ generated by
means of non-hydrolytic sol-gel process. Polymer 53:283–290
Chen CL, Chan TW, Su SC, Teng H, Lee YL (2014) High
performance solid-state dye-sensitized solar cells based on
poly(acrylonitrile-co-vinyl acetate)/TiO2 nanoparticles redox
electrolytes. J Power Sources 247:406–411
Chiang PC, Whang WT (2003) The synthesis and morphology
characteristic study of BAO-ODPA polyimide/TiO2 nano hybrid
films. Polymer 44:2249–2254
Muir JMR, Idriss
H (2013) Computational study of cysteine
interaction with the rutile TiO2 (110) surface. Surf Sci
617:60–67
Ehsani A, Adeli S, Babaei F, Mostaanzadeh H, Nasrollahzadeh M
(2014) Electrochemical and optical properties of TiO2 nanopar-
Muthirulan P, Devi CKN, Sundaram MM (2013) Facile synthesis of
novel hierarchical TiO2@Poly(o-phenylenediamine) core–shell
structures with enhanced photocatalytic performance under solar
light. J Environ Chem Eng 1:620–627
Okamoto M, John B (2013) Synthetic biopolymer nanocomposites for
tissue engineering scaffolds. Prog Polym Sci 38:1487–1503
Pandini S, Baldi F, Paderni K, Messori M, Toselli M, Pilati F,
ticles/poly tyramine composite film.
713:91–97
J Electroanal Chem
Fujii N, Otaka A, Funakoshi S, Bessho K, Watanabe T, Akaji K,
Yajima H (1987) Studies on Peptides. CLI. Syntheses of cystine-
peptides by oxidation of S-protected cysteine-pPeptides with
thallium(III) trifluoroacetate. Chem Pharm Bull 35:2339–2347
Gupta KK, Mishra PK, Srivastava P, Gangwar M, Nath G, Maiti P (2013)
Hydrothermal in situ preparation of TiO2 particles onto poly(lactic
acid) electrospun nanofibres. Appl Surf Sci 264:375–382
Jang W, Shin D, Choi S, Park S, Han H (2007) Preparation,
morphology and properties of acylchloride-grafted multiwall
carbon nanotubes/fluorinated polyimide composites. Polymer
48:2130–2143
Kango S, Kalia S, Celli A, Njuguna J, Habibi Y, Kumar R (2013) Surface
modification of inorganic nanoparticles for development of
organic–inorganic nanocomposites. Prog Polym Sci 38:1232–1261
Katsarava R (2003) Active polycondensation: from peptide chemistry
to amino acid based biodegradable Polymers. Macromol Symp
199:419–429
`
Gianoncelli A, Brisotto M, Bontempi E, Ricco T (2013) One-
way and two-way shape memory behaviour of semi-crystalline
networks based on sol-gel cross-linked poly(e-caprolactone).
Polymer 54:4253–4265
Park DH, Hwang SJ, Oh JM, Yang JH, Choy JH (2013a) Polymer–
inorganic supramolecular nanohybrids for red, white, green, and
blue applications. Prog Polym Sci 38:1442–1486
Park SI, Lee EO, Yang HM, Park CW, Kim JD (2013b) Polymer-
hybridized liposomes of poly(amino acid) derivatives astrans-
epidermal carriers. Colloid Surf B Biointerfaces 110:333–338
Que W, Zhou Y, Chan YC, Kam CH (2000) Optical and microstruc-
tural properties of sol-gel derived titania/organically modified
silane thin films. Thin Solid Films 358:16–21
Lachheb H, Dappozze F, Houas A, Guillard C (2012) Adsorption and
photocatalytic degradation of cysteine in presence of TiO2.
J Photochem Photobiol A Chem 246:1–7
Rajesh S, Senthilkumar S, Jayalakshmi A, Nirmala MT, Ismail AF,
Mohan D (2013) Preparation and performance evaluation of poly
123

L-cysteine-induced fabrication
(amide–imide) and TiO2 nanoparticles impregnated polysulfone
nanofiltration membranes in the removal of humic substances.
Colloids Surf A Physicochem Eng Aspects 418:92–104
Sanda F, Endo T (1999) Syntheses and functions of polymers based
on amino acids. Macromol Chem Phys 200:2651–2661
Seyedjamali H, Pirisedigh A (2011a) In situ sol–gel fabrication of
new poly(amide–ether–imide)/titania (TiO2) nanocomposite thin
films containing L-leucine moieties. Colloid Polym Sci
289:15–20
Tsai MH, Liu SJ, Chiang PC (2006) Synthesis and characteristics of
polyimide/titania nano hybrid films. Thin Solid Films
515:1126–1131
Tsai MH, Chang CJ, Chen PJ, Ko CJ (2008) Preparation and
characteristics of poly(amide–imide)/titania nanocomposite thin
films. Thin Solid Films 516:5654–5658
Vanherck K, Koeckelberghs G, Vankelecom IFJ (2013) Crosslinking
polyimides for membrane applications. Prog Polym Sci
38:874–896
Seyedjamali H, Pirisedigh A (2011b) Synthesis and morphology of
new functional polyimide/titania nano hybrid materials. J Mater
Sci 46:6744–6750
Wu CB, Hao JY, Deng XM (2007) A novel degradable poly(b-amino
ester) and its nano-complex with poly(acrylic acid). Polymer
48:6272–6285
Seyedjamali H, Pirisedigh A (2012a) Synthesis of well-dispersed
polyimide/TiO2 nanohybrid films using a pyridine-containing
aromatic diamine. Polym Bull 68:299–308
Seyedjamali H, Pirisedigh A (2012b) Well-dispersed polyimide/TiO2
nanocomposites: in situ sol-gel fabrication and morphological
study. Colloid Polym Sci 290:653–659
Xiao Y, Low BT, Hosseini SS, Chung TS, Paul DR (2009) The
strategies of molecular architecture and modification of polyim-
ide-based membranes for CO2 removal from natural gas. Prog
Polym Sci 34:561–580
Xue Y, Tang X, Huang J, Zhang X, Yub J, Zhang Y, Guid S (2011)
Anti-tumor efficacy of polymer–platinum(II) complex micelles
fabricated from folate conjugated PEG-graft-a, b-poly [(N-
amino acidyl)-aspartamide] and cis-dichlorodiammine plati-
num(II) in tumor-bearing mice. Colloid Surf B Biointerfaces
85:280–281
Singh R, Lillard JW Jr (2009) Nanoparticle-based targeted drug
delivery. Exp Mol Pathol 86:215–223
Song G, Zhang Y, Wang D, Chen C, Zhou H, Zhao X, Dang G (2013)
Intermolecular interactions of polyimides containing benzimid-
azole and benzoxazole moieties. Polymer 54:2335–2340
Su C, Shao C, Liu Y (2010) Synthesis of heteroarchitectures of PbS
nanostructures well-erected on electrospun TiO2 nanofibers.
J Colloid Interface Sci 346:324–329
Yoshida M, Lal M, Kumar ND, Prasad PN (1997) TiO2 nano-particle-
dispersed polyimide composite optical waveguide materials
through reverse micelles. J Mater Sci 32:4047–4051
123