Synthesis and characterization of novel type poly (4-chloromethyl styrene-grft-4-vinylpyridine)/TiO2 nanocomposite via nitroxide-mediated radical polymerization

Article abstract of DOI:10.1016/j.polymer.2011.08.016

This paper describes the synthesis and characterization of novel type poly (4-chloromethyl styrene-graft-4-vinylpyridine)/TiO₂ nanocomposite. Firstly, poly (4-chloromethyl styrene)/TiO₂ nanocomposite was synthesized by in situ free radical polymerizing of 4-chloromethyl styrene monomers in the presence of 3-(trimethoxysilyl) propylmethacrylate (MPS) modified nano-TiO₂. Thereafter, 1-hydroxy-2,2,6,6-tetramethyl-1- piperidinyloxy (TEMPO-OH) was synthesized by the reduction of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). This functional nitroxyl compound was covalently attached to the poly (4-chloromethyl styrene)/TiO₂ with replacement of chlorine atoms in the poly (4-chloromethyl styrene) chains. The controlled graft copolymerization of 4-vinylpyridine was initiated by poly (4-chloromethyl styrene)/TiO₂ nanocomposite carrying TEMPO groups as a macroinitiators. The coupling of TEMPO with poly (4-chloromethyl styrene)/TiO₂ was verified using ¹H nuclear magnetic resonance (NMR) spectroscopy. The obtained nanocomposites were studied using transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and the optical properties of the nanocomposites were studied using ultraviolet-visible (UV-Vis) spectroscopy.

Full text of DOI:10.1016/j.polymer.2011.08.016

Polymer 52 (2011) 4760e4769
Contents lists available at SciVerse ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Synthesis and characterization of novel type poly
4-chloromethyl styrene-grft-4-vinylpyridine)/TiO2
(
nanocomposite via nitroxide-mediated radical polymerization
Mehdi Jaymand*
Laboratory of Polymer, Faculty of Chemistry, Payame Noor University, Tabriz 5158654778, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 May 2011
Received in revised form
This paper describes the synthesis and characterization of novel type poly (4-chloromethyl styrene-graft-
4
-vinylpyridine)/TiO
synthesized by in situ free radical polymerizing of 4-chloromethyl styrene monomers in the presence of
-(trimethoxysilyl) propylmethacrylate (MPS) modified nano-TiO Thereafter, 1-hydroxy-2,2,6,6-
2 2
nanocomposite. Firstly, poly (4-chloromethyl styrene)/TiO nanocomposite was
7
August 2011
3
2
.
Accepted 13 August 2011
Available online 18 August 2011
tetramethyl-1-piperidinyloxy (TEMPO-OH) was synthesized by the reduction of 2,2,6,6-tetramethyl-1-
piperidinyloxy (TEMPO). This functional nitroxyl compound was covalently attached to the poly (4-
chloromethyl styrene)/TiO
chains. The controlled graft copolymerization of 4-vinylpyridine was initiated by poly (4-chloromethyl
styrene)/TiO nanocomposite carrying TEMPO groups as a macroinitiators. The coupling of TEMPO
with poly (4-chloromethyl styrene)/TiO
was verified using 1H nuclear magnetic resonance (NMR)
2
with replacement of chlorine atoms in the poly (4-chloromethyl styrene)
Keywords:
TiO nanoparticles
2
In situ polymerization
NMRP
2
2
spectroscopy. The obtained nanocomposites were studied using transmission electron microscopy (TEM),
Fourier-transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), differential scanning calo-
rimetry (DSC) and the optical properties of the nanocomposites were studied using ultravioletevisible
(
UVeVis) spectroscopy.
Ó 2011 Elsevier Ltd. All rights reserved.
1
. Introduction
of star and graft copolymers with controlled molecular weight
under mild conditions. This polymerization method is based on the
use of traditional radical initiator (e.g., B.P.O) in the presence of
stable nitroxide radical (e.g., TEMPO). Compared with other graft
copolymerization such as anionic polymerization, an advantage of
‘living’ free radical polymerization (LFRP) is that in the preparation
of grafted copolymers, the terminal groups are stable in air at room
temperature, and prepolymers can be isolated, stored, and used as
needed. Moreover, in anionic polymerization, stringent polymeri-
zations conditions are required [11e14].
The past few years have witnessed a rapid development in the
field of controlled radical polymerization for synthesizing tailor-
made polymers with well-defined architecture and predictable
molecular weights [1e5]. A number of techniques have been
explored to achieve this control: atom transfer radical polymeri-
zation (ATRP) [6,7], nitroxide-mediated radical polymerization
(
[
NMRP) [8], and reversible addition fragmentation process (RAFT)
9,10]. Nitroxide-mediated radical polymerization method is
a controlled free radical methodology, which allows the synthesis
Considering such novel chemical properties as acidity, basicity,
and hydrophilic-hydrophobic balance, 4-vinylpyridine is of great
importance. The homo or copolymers of 4-vinylpyridine are
intriguing materials with many applications, such as in sensors and
actuators, thin films, host/ligand of metal-containing chromo-
phores, antimicrobial materials, and so on [15e18]. Controlled
polymerization of P4VP has been achieved by living ionic poly-
merization [19,20], and recent reversible addition fragmentation
chain transfer [21], polymerization studies have also reported
successful controlled/living radical polymerization (CRP) syntheses
of P4VP as well as polystyrene/P4VP triblock copolymers [22].
Studies with nitroxide-mediated polymerization [23,24] of
Abbreviations: LFRP, ‘‘Living’’ free radical polymerization; CRP, Controlled/living
radical polymerization; NMRP, Nitroxide-mediated radical polymerization; TEMPO,
2
,2,6,6-Tetramethyl-1-piperidinyloxy; B.P.O, Dibenzoyl peroxide; PCMS, Poly (4-
0
chloromethyl styrene); P4VP, Poly (4-vinylpyridine); AIBN, 2, 2 -Azobis (iso-
butyronitrile); DMF, N,N-Dimethylformamide; TEM, Transmission electron
microscopy; T , Glass transition temperature; DSC, Differential scanning calorim-
g
etry; TGA, Thermogravimetric analysis; BET, Specific surface area; MPS, 3-(Trime-
thoxysilyl) propylmethacrylate.
*
Tel.: þ98 411 5492296; fax: þ98 411 5419744.
E-mail addresses: m_jaymand@yahoo.com, m.jaymand@gmail.com.
0
032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2011.08.016

M. Jaymand / Polymer 52 (2011) 4760e4769
4761
2
4
-vinylpyridine reported that ‘‘pseudo-living’’ polymerization was
50þ/ꢁ15 m /g. 4-Chloromethyl styrene and 4-vinylpyridine
monomers from Merck (Darmstadt, Germany) were distilled
under a reduced pressure before use. TEMPO was prepared in our
laboratory [8,11]. Natrium-L(þ)-ascorbate and 3-(trimethoxysilyl)
propylmethacrylate (MPS), were obtained from Merck and used
ꢀ
possible at a relatively high reaction temperature (T > 100 C).
In recent years, polymer encapsulated submicron inorganic
particles have attracted increasing because of their exceptional
properties and use in technological applications [25e28]. Titanium
0
dioxide (TiO
2
) is one of the most important pigments and fillers
without further purification. 2, 2 -Azobis (isobutyronitrile) (AIBN)
from Merck, crystallized in ethanol at 50 C before use. Toluene,
ꢀ
used for a variety of scientific endeavors such as a dye in conjugated
polymers for photoelectrochemical [29] or photoconductive agents
(Merck) was dried by refluxing over sodium and distilled under
argon prior to use. All other reagents were purchased from Merck
and purified according to the standard methods.
2
[30] a photocatalyst in a photodegradable TiO -polystyrene nano-
composite films [31] and semiconductor electrodes in photo-
electrochemical cells [32]. However, it is difficult to disperse
inorganic nanoparticles in non-polar polymers due to the incom-
patibility at the interphase between the hydrophobic matrix and
the hydrophilic oxide surface. Because of their extremely large
surface-area/particle-size ratio, nanoparticles tend to strongly
aggregate, hence reducing the mechanical properties of the resul-
tant nanocomposite materials [33e37]. Many efforts have been
taken to overcome this problem and to enhance the fillerematrix
interaction, such as ultrasonic irradiation, which has been explored
2
2.2. Modification of TiO nanoparticles with MPS coupling agent
The process started with dispersing of certain amount (1.5 g) of
TiO nanoparticles in ethanol (100 ml) as the solvent under 20 min
2
ultrasonication, into which distilled water (0.6 g), ammonia
(25wt.%, 0.4 g), and the coupling agent MPS (1.5 g) were added. The
dispersed solution was then transferred to a 250 ml round bottom
flask equipped with a condenser and a magnetic stirrer under
bubbling argon gas. The solution temperature was maintained at
2 2 2 3
for dispersion of SiO , TiO , and Al O nanoparticles during the
ꢀ
synthesis of inorganic/polymer nanocomposite materials. However,
this approach is restricted due to the limited interaction between
the inorganic fillers and the organic matrix, compared with the
very strong interaction between individual nanoparticles. Some
methods have been explored to improve the dispersibility of inor-
ganic nanoparticles in polymer such as surface modification of
nanoparticles with, titanate and silane coupling agents [35e37],
modification by chemisorption of small molecules [26,38] and
modification by the adsorption of polymers [39]. In addition to,
polymer chains have been attached chemically to the inorganic
nanoparticles. In this respect, ‘‘grafting from’’ and ‘‘grafting to’’
methods have been proposed. The ‘‘grafting from’’ approach relies
on the immobilization of initiators for the controlled/living radical
polymerization (CRP) of various monomers, followed by the chain
growth from the surface and formation of polymer brush of
possible high grafting density [40e42]. Currently, to the best of our
knowledge, most of the reported approaches to prepare organic-
inorganic nanocomposites involve living radical polymerizations.
Hojjati and Charpentier who used the relatively new technique of
70 C under stirring for 8 h. The particles were recovered by
centrifugation at 6000 rpm for 10 min. The particles were then
redissolved in ethanol and reprecipitated by centrifugation which
was repeated until the solution was clear. The solid product was
dried overnight under vacuum at room temperature.
2
2.3. Encapsulation of modified TiO nanoparticles by poly (4-
choloromethyl styrene) via in situ free radical polymerization
The free radical polymerization of 4-choloromethyl styrene
monomers from the MPS-modified TiO was accomplished by the
2
followed procedure:
2
MPS-TiO (0.5 g), AIBN (0.05 g) and 4-choloromethyl styrene
monomers (3.0 g, 21.6 mmol) were mixed into a 100 ml flask
containing 20 ml toluene. The mixture was irradiated with ultra-
sonic vibrations for 15 min, bubbling with argon gas. Thereafter, the
mixture was refluxed into an oil bath maintained at a temperature
ꢀ
of 65 C and stirred with electromagnetic stirring for 12 h under
argon protection to complete the polymerization. The product
recovered by filtration in large amount of methanol. To ensure that
no ungrafted polymer remained in the product, the particles were
redissolved in toluene and reprecipitated by centrifugation at
6000 rpm for 10 min, with this process repeated until the solution
was clear (Yield: 0.81 g). For preparation of pure poly (4-
RAFT polymerization, to polymerized methylmeta crylate from TiO
2
nanoparticles [43], Zhao and his coworkers functionalized multi-
walled carbon nanotubes via nitroxide-mediated radical polymer-
ization [44], and by applying ATRP, Liu and Wang, grew polymer
chains of hydroethyl acrylate from ZnO nanoparticles [45].
For the first time, synthesis and characterization of poly (4-
2
choloromethyl styrene) the polymer was cleaved from TiO nano-
chloromethyl
P4VP)/TiO ] nanocomposite via nitroxide-mediated radical poly-
merization (NMRP) are reported. Firstly, TiO nanoparticles were
styrene-graft-4-vinylpyridine)/TiO
2
[(PCMS-g-
particles, through the refluxing, for about 24 h under acidic
conditions (Scheme 1).
2
2
modified by MPS coupling agent. Thereafter, 4-chloromethyl
2.4. Preparation of TEMPO-OH by reduction of TEMPO
styrene monomers were added to carry out copolymerization
with vinyl groups on the MPS-modified TiO
AIBN in solution medium. Afterward, 1-hydroxy-2,2,6,6-
tetramethyl-1-piperidinyloxy (TEMPO-OH) was coupled with poly
2
by free radical initiator
TEMPO (0.25 g, 1.6 mmol) was suspended in a solution of
sodium ascorbate (0.525 g, 5.3 mmol) in water (5 ml) and shaken
vigorously until it was completely decolorized (w30 min). The
resulting suspension was extracted with ether. Afterward, the ether
(
2
4-chloromethyl styrene)/TiO nanocomposite by a substitution
nucleophilic reaction in N,N-dimethylformamide (DMF) as the
2 4
extracts was washed with water and brine, dried (using Na SO ),
solvent. The controlled graft copolymerization of 4-vinylpyridine
and evaporated under reduced pressure to produce a crude product
(Scheme 2).
was initiated by PCMS/TiO
a macroinitiators.
2
carrying TEMPO groups as
2
2.5. Synthesis of PCMS-TEMPO/TiO macroinitiator
2
. Experimental
In a tree-neck round-bottom flask equipped with condenser,
dropping funnel, gas inlet/outlet, and a magnetic stirrer, 0.10 g
0.65 mmol) of TEMPO-OH was dissolved in anhydrous N,N-dime-
thylformamide (DMF) (3 ml) and added under N atmosphere to
30 mg (1.3 mmol) hexane washed NaH (from 60% suspension in oil).
2
.1. Materials
(
Titanium dioxide (P25, Degussa AG, Frankfurt, Germany),
average primary particle size 21 nm and specific surface area (BET)
2

4762
M. Jaymand / Polymer 52 (2011) 4760e4769
2
Scheme 1. Encapsulation of modified nano-TiO by PCMS via in situ free radical polymerization.
samples were prepared by grinding the dry powders with KBr and
compressing the mixture into disks. The disks were stored in
a desiccator to avoid moisture absorption. The spectra were
1
recorded at room temperature. H nuclear magnetic resonance
ꢀ
(
NMR) spectra were obtained at 25 C using an FT-NMR (400 MHz)
Scheme 2. Preparation of TEMPO-OH by reduction of TEMPO.
Brucker spectrometer (Brucker, Ettlingen, Germany). The sample
for H NMR spectroscopy was prepared by dissolving about 10 mg
1
of products in 5 ml of deuterated chloroform. Transmission electron
microscopy (TEM) was performed using a Philips EM208 micro-
scope (Phillips, Eindhoven, Netherlands) with a 100 kV accelerating
voltage. The thermal properties of the nanocomposites were
obtained with a TGA-PL STA 1640 (Polymer Laboratories, Shrop-
shire, UK). About 10 mg of the sample was heated between 25 and
The mixture was stirred for 30 min. In a separate container, 1 g of
poly (4-chloromethyl styrene)/TiO was dissolved in 5 ml DMF and
was slowly added to the mixture under N atmosphere and
refluxed for 24 h at room temperature. The reaction was terminated
by pouring the content of the flask into a large amount of methanol.
The white solid was filtered, washed with methanol and dried in
vacuum (Scheme 3).
2
2
ꢀ
ꢀ
ꢁ1
600 C at a rate of 10 C min under flowing nitrogen. Differential
scanning calorimetry analyses were performed with a NETZSCH
(
2
Selb, Germany)-DSC 200 F3 Maia. The sample was first heated to
2
.6. Nitroxide-mediated living radical polymerization of 4-
ꢀ
00 C and then allowed to cool for 5 min to eliminate the thermal
vinylpyridine onto PCMS-TEMPO/TiO macroinitiator
2
ꢀ
history. Thereafter, the sample was reheated to 200 C at a rate of
1
at a flow rate of 50 ml min . Ultravioletevisible (UVeVis) spectra
of the samples were measured using a Shimadzu 1601 PC, UVeVis
spectrophotometer (Shimadzu, Kyoto, Japan) in the wavelength
range 300e800 nm.
ꢀ
ꢁ1
0 C min . The entire test was performed under nitrogen purging
ꢁ
1
In a typical experiment, a dry ampoule was charged with
toluene (10 ml), 4-vinylpyridine monomers (3.0 g, 28.5 mmol), and
PCMS-TEMPO/TiO macroinitiator (0.5 g). Thereafter, the ampoule
2
was sealed and three cycles of freeze-pump-thaw were performed
to remove oxygen. After which the reaction mixture was heated at
ꢀ
130 C and maintained at this temperature for 12 h. The reaction
was terminated by pouring the content of the ampoule into a large
amount of methanol. To remove the ungrafted poly (4-
vinylpyridine) from the crude product, the powder was extracted
with DMF in a Soxhlet apparatus for 24 h. The precipitated polymer
was filtered, washed several times with DMF, and dried under
vacuum (Yield: 0.68 g), (Scheme 4).
3. Results and discussion
3.1. Modification of TiO nanoparticles with coupling agent MPS
2
The functional silanes have been widely used for the surface
modification of metal oxides. To get evidence that coupling agent
MPS was chemically bonded to TiO
copy investigation was firstly used to identify the qualitative
composition of modified TiO . The FTIR spectra of coupling agent
MPS (a), raw TiO (b) and MPS-modified TiO (c) are shown in Fig. 1.
The FTIR spectra of the coupling agent MPS shows the characteristic
2
nanoparticles, FTIR spectros-
2
.7. Characterization
2
Fourier-transform infrared (FTIR) spectra of the samples were
2
2
obtained on a Shimadzu 8101M FTIR (Shimadzu, Kyoto, Japan). The
2
Scheme 3. Synthesis of PCMS-TEMPO/TiO macroinitiator.

M. Jaymand / Polymer 52 (2011) 4760e4769
4763
2
Scheme 4. Nitroxide-mediated living radical polymerization of 4-vinylpyridine onto PCMS-TEMPO/TiO macroinitiator.
absorption bands due to stretching vibration of CeH in the
styrene) and the TiO
found that the TiO nanoparticle encapsulated by PCMS is charac-
terized by the CeH aromatic stretching vibration at 3050 and
2
nanoparticles encapsulated by PCMS. It is
ꢁ
1
ꢁ1
2
944e2843 cm region, the band around 1719 cm is due to
2
ꢁ
1
stretching vibration of C]O and the band around 1637 cm is due
to stretching vibration of C]C which can act as the functional site
for the further copolymerization [35].
ꢁ
1
3021 cm , the CeH aliphatic stretching vibration at 2923 and
ꢁ
1
2852 cm , the phenyl ring stretching vibration at 1445, 1511 and
ꢁ1
ꢁ1
ꢁ1
The TieOeSi transmittance peak at 1068 cm
and C]O
1610 cm , the ring in phase CeH stretching vibration at 1020 cm
,
ꢁ
1
ꢁ1
vibration band at 1708 cm are found for the MPS-modified TiO
Fig. 1-c). In addition grafting of coupling agent MPS onto TiO
2
and the ring out of-plane bend at 681 cm , where the typical
absorption bands for PCMS are clearly seen, indicating the exis-
tence of PCMS on the particle surface.
(
2
surface with covalent chemical bonding can be confirmed by the
ꢁ
1
eCH stretching vibration at 2925e2874 cm region. The bands
ꢁ1
ꢁ1
around 1634 cm and3385 cm are due to the hydroxyl groups on
the surface of TiO nanoparticles. The shift of the C]O vibration
band from 1719 to 1708 cm
hydrogen bond between the carbonyl group from MPS and the
hydroxyl group on the surface of TiO nanoparticles [46].
The TiO nanoparticles both before and after modification was
3.3. Synthesis of PCMS-TEMPO/TiO macroinitiator
2
2
ꢁ
1
is due to the formation of the
At first in order to produce the active sites on PCMS/TiO2
nanocomposite, TEMPO was added to PCMS/TiO . So, TEMPO-OH
2
2
reacts with PCMS/TiO to give the PCMS-TEMPO/TiO2 macro-
2
1
2
initiator. The H NMR spectra of PCMS/TiO nanocomposite indicate
2
studied by organic phase/water partitioning experiments. As one
the chemical shifts at 1.13e2.34 and 6.17e7.35 ppm represent the
aliphatic (a) and aromatic (c) protons respectively, and the chemical
0
would expect after modification by an organic group, nano-TiO
2
s
hydrophilicity changes. A photograph of vials containing equal
volumes of chloroform and water, and equal masses of unmodified
titania and modified titania are shown in Fig. 2. The modified titania
shifts at 4.16e4.67 ppm shows the eCH Cl protons (b) in this
2
1
product. Comparison with the H NMR spectrum of PCMS/TiO the
2
1
H NMR spectrum of PCMS-TEMPO/TiO2 macroinitiator indicates
(
Fig. 2-b) exhibited good dispersion in organic phase (chloroform),
the additional chemical shifts of CH eO (d) and methyl groups (e)
2
while unmodified TiO (Fig. 2-a) one partitioned into the water
phase, indicating the success of the incorporation of the MPS
coupling agent to the titania surface.
2
of TEMPO molecules at 3.34e3.48 and 0.76e1.06 ppm respectively
1
[47,48]. The H NMR spectra showed that the functional groups of
the TEMPO were coupled with PCMS/TiO nanocomposite, thus the
2
NMRP reaction has been occurring (Fig. 4).
3.2. Encapsulation of modified TiO
2
nanoparticles by poly (4-
chloromethyl styrene)
3.4. Preparation of poly (4-chloromethyl styrene-grft-4-
2
vinylpyridine)/TiO nanocomposite
The methacrylate group of the MPS can further react with 4-
chloromethyl styrene monomers via free radical polymerization,
Poly (4-vinylpyridine) is a pH-sensitive polymer which is
soluble in water when the pH value is below 4.7 and becomes
insoluble when the pH is high (>4.7). Therefore, block or graft
forming a polymer shell chemically bonded to the inorganic TiO
core. Fig. 3 shows the FTIR spectra of free poly (4-chloromethyl
2

4764
M. Jaymand / Polymer 52 (2011) 4760e4769
Fig. 2. The photographs were taken after the samples were placed in the bottles and
ultrasonicated for 10 min; the concentration was ca. 0.5 mg/ml. In the bottles, the
upper layer is water and the lower layer is chloroform phase. The unmodified TiO is
is suspended in the
2
well dispersed in the water phase (a), while the modified TiO
2
organic phase (b).
Compared with that of PCMS/TiO
1
2
, new peaks at 1360 and
636 cm attributed to pyridine groups in the FTIR spectrum of
PCMS-g-P4VP)/TiO nanocomposite were observed [16,49]. The
ꢁ1
(
2
ꢁ
1
band around 3414 cm is due to the hydroxyl groups in the TiO
nanparticles.
2
The chemical structure of the (PCMS-g-P4VP)/TiO
composite was further examined by H NMR spectroscopy. In the
H NMR spectrum of the (PCMS-g-P4VP)/TiO (Fig. 6), the signals
2
2
nano-
1
1
due to the aromatic protons (c) and the pyridine ring protons (g)
were observed at 6.04e7.15 and 8.08e8.43 ppm, respectively
2 2
Fig. 1. FTIR spectra of coupling agent MPS (a), raw TiO (b) and MPS-modified TiO (c).
copolymers of P4VP could respond to pH values in water solution
and self-assemble to form different supramolecular structures.
Additionally, the complexing properties of the P4VP, e.g., toward
metallic salts, make it act as an interesting multidentate ligand for
the preparation of block or graft copolymers/nanoparticle mixtures
[16e18]. Thus, we choose P4VP as the building blocks of the shell.
The thermal homolytic scission of the CeO bond of the aminoxy
moiety of the PCMS-TEMPO/TiO
2
macroinitiator takes place at
ꢀ
130 C and causes the radical polymerization of 4-vinylpyridine to
yield the controlled graft copolymerization. The bond dissociation
is considered to be reversible [11]. To successfully carry out this
copolymerization, it was necessary to perform this reaction at this
temperature any spontaneous thermal polymerization and it was
necessary to perform that at this reaction condition, the polymer-
ization is living and controlled. For comparison, the blank experi-
2
ments proceed in the absence of TEMPO onto PCMS/TiO was also
included. In this condition, no homo poly (4-vinylpyridine) was
formed in the absence of macroinitiator under the identical NMRP
conditions. This suggests that the possibility of the formation of
homopolymer in the grafting reaction can be excluded in this study
and it performed that the polymerization is living.
Fig. 5 shows the FTIR spectra of (PCMS-g-P4VP)/TiO
PCMS/TiO (b) nanocomposites. The FTIR spectra of (PCMS-g-
P4VP)/TiO nanocomposite is basically the same due to strong
absorption by (PCMS-g-P4VP) and weak absorption of TiO
2
(a) and
2
2
2
.
2
Fig. 3. FTIR spectra of free PCMS (a) and PCMS/TiO nanocomposite (b).

M. Jaymand / Polymer 52 (2011) 4760e4769
4765
Fig. 4. 1H NMR spectra of PCMS/TiO
nanocomposite and PCMS-TEMPO/TiO macroinitiator.
2 2
[
4
17,50]. Furthermore, the living graft copolymerization of
signals of CHeO and methyl groups (e) at 3.46 and 0.75e1.02 ppm
respectively. The H NMR spectra show that the functional groups
1
-vinylpyridine onto PCMS/TiO is characterized by the functional
2
groups of the TEMPO at the end of poly (4-vinylpyridine) chains.
The functional group of the TEMPO appears with characteristic
of the TEMPO were retained at the end of poly (4-vinylpyridine)
chains, which provides strong evidence that the NMRP reaction
Fig. 5. FTIR spectra of (PCMS-g-P4VP)/TiO
2
(a) and PCMS/TiO
2
(b) nanocomposites.
Fig. 6. 1H NMR spectra of (PCMS-g-P4VP)/TiO
nanocomposite.
2

4766
M. Jaymand / Polymer 52 (2011) 4760e4769
Table 1
Grafting parameters for PCMS/TiO
2
and (PCMS-g-P4VP)/TiO
2
nanocomposites.
Grafting
Samples
Mass of
Weight Grafting
g
Grafting (W ) Gain (%WG) Efficiency (%GE) Yield (%G)
PCMS/TiO
2
0.81
0.68
8.8
5.1
23.1
17.4
38.2
26.5
(
PCMS-g-P4VP)/TiO
2
2 2
Fig. 8. DSC traces of the PCMS (a), PCMS/TiO (b) and (PCMS-g-P4VP)/TiO (c).
Fig. 7. UVeVis spectra of PCMS/TiO
composite (b) and PCMS (c).
2 2
nanocomposite (a), (PCMS-g-P4VP)/TiO nano-
Fig. 9. TGA curves of the TiO
P4VP)/TiO (d) and PCMS (e).
2 2 2
(a), MPS-modified TiO (b), PCMS/TiO (c), (PCMS-g-
2
occurred. These data were confirmed the successful synthesis of the
PCMS-g-P4VP)/TiO nanocomposite via nitroxide-mediated
radical polymerization.
The grafting parameters such as grafting yield, grafting effi-
ciency, and weight gain were calculated, based on gravimetric
measurements, according to the following equations: grafting yield
(
2
recorded and are summarized in Table 2. Small values of absor-
bance at the visible and UV region were observed for PCMS, which
is reasonable transparency but has no function of filtering out UV
light. However, relatively strong absorbance in the UV region and
small absorbance at the visible region, which also means a typical
optical property of the combination of visual transparency and UV
filters close to the visual wavelengths, were observed for the
(
W
%G) ¼ (W
) ꢂ 100; weight Gain (%WG) ¼ (W
where W is the mass of the grafting copolymer, W
initiator (MPS-TiO or PCMS-TEMPO/TiO ), and W
g
ꢁ W
0
)/W
g
ꢂ 100; grafting efficiency (%GE) ¼ W
g
/(W
þ W ) ꢂ 100;
m
þ
0
g
ꢁ W
0
)/(W
m
0
g
0
is the mass of
is the mass of
2
2
m
(
PCMS-g-P4VP)/TiO
enhanced in the UV range for PCMS/TiO
the (PCMS-g-P4VP)/TiO sample. The range of UV wavelengths is
often subdivided into UV-A (380e315 nm), UV-B (315e280 nm),
and UV-C (280e10 nm). Thus, PCMS/TiO and (PCMS-g-P4VP)/TiO
nanocomposites can be applied to block the UV-A radiation.
nanocomposite. The scattering is remarkably
2
the monomer taken for the reaction. The grafting parameters for
PCMS/TiO and (PCMS-g-P4VP)/TiO nanocomposites were calcu-
lated and summarized in Table 1.
2
compared to scattering in
2
2
2
2
2
3.5. Optical properties
The samples for UVeVis spectroscopy were prepared by addi-
3
.6. Thermal property study
tion of same amount of the obtained nanocomposites into boiled
DMF solutions. Films with relatively uniform thickness were
obtained on the sidewall of a quartz glass after solvent evaporation.
Thermal behaviors of the obtained nanocomposites were
investigated by differential scanning calorimetry (DSC) and
2
The UVeVis spectra of PCMS/TiO nanocomposite, (PCMS-g-P4VP)/
TiO nanocomposite and pure PCMS are shown in Fig. 7. Their
2
absorbance at wavelengths 400 nm (A400) and 300 nm (A300) were
Table 3
Weight changes of the samples from TGA.
Samples
Initial
wt. (%)
Residual
wt. (%)
Grafted
MPS (%)
Grafted
PCMS (%)
Grafted
P4VP (%)
Table 2
Absorbance at wavelengths 400 nm (A400) and 300 nm (A300).
TiO
PCMS
MPS-TiO
PCMS/TiO
(PCMSeg-P4VP)/TiO
2
100
100
100
100
100
99.32
8.68
95.02
56.74
30.17
e
e
e
Samples
A
300 (nm)
A400 (nm)
e
e
e
PCMS
PCMS/TiO
0.210
1.315
0.908
0.052
0.414
0.381
2
4.3
4.3
4.3
e
e
2
2
38.28
38.28
e
(
PCMS-g-P4VP)/TiO
2
2
26.57

M. Jaymand / Polymer 52 (2011) 4760e4769
4767
2 2 2
Fig. 10. TEM micrographs of raw TiO nanoparticles (a), TiO nanoparticles encapsulated by PCMS (b) and (PCMS-g-P4VP)/TiO (c).
thermogravimetric analysis (TGA). Fig. 8 shows the DSC traces of
the PCMS (a), PCMS/TiO (b) and (PCMS-g-P4VP)/TiO (c). The
nanocomposite. The DSC traces of (PCMS-g-P4VP)/TiO
composite (Fig. 8c) shows a strong endothermic peak at 310 C,
corresponding to the degradation of the poly (4-vinylpyridine)
chains. For the (PCMS-g-P4VP)/TiO nanocomposite, the T is too
2 g
weak to measure, or it is suppressed due to the confinements of
2
nano-
ꢀ
2
2
PCMS is non-crystalline and therefore does not exhibit any crys-
tallization or melting transitions. Fig. 8(a) exhibits an endothermic
ꢀ
peak approximately at 81 C, corresponding to the glass transition
ꢀ
temperature of PCMS. In Fig. 8(b) the transition observed at 106 C
polymer chains (especially P4VP due to its hydrophilic-
can be designed as the glass transition temperature of PCMS/TiO
2
2
hydrophobic balance) by the TiO nanoparticles. In this Figure the
Fig. 11. The photographs were taken after the samples were placed in the bottles and ultrasonicated for 10 min; the concentration was ca. 1 mg/ml. Photograph of samples: PCMS/
TiO in toluene (a), PCMS/TiO in DMF (b), (PCMS-g-P4VP)/TiO in toluene (c) and (PCMS-g-P4VP)/TiO in DMF (d).
2
2
2
2

4768
M. Jaymand / Polymer 52 (2011) 4760e4769
ꢀ
weak transition observed at 119 C can be designed as the glass
transition temperature of (PCMS-g-P4VP)/TiO nanocomposite.
Strong interfacial bonding between the modified TiO nano-
a good dispersion of (PCMS-g-P4VP)/TiO
The change in the dispersibility was additional evidence showing
that (PCMS-g-P4VP)/TiO was obtained. In other words, the dis-
persibility of polymer grafted TiO was a reflection of the solubility
of the polymer attached, so the polymer change from PCMS to
(PCMS-g-P4VP) affected the dispersibility of TiO
2
to form a stable system.
2
2
2
particles and polymer chains leads to an increase of the glass
transition temperature of nanocomposites by impeding the chain
flexibility.
2
2
.
Characteristic TGA curves of the TiO
PCMS/TiO (c), (PCMS-g-P4VP)/TiO (d) and PCMS (e) are shown in
Fig. 9. TGA results indicate improvement of the thermal stability for
2 2
(a), MPS-modified TiO (b),
2
2
4. Conclusions
PCMS/TiO
2
compared to neat PCMS. According to the Fig. 9(c), we
Poly (4-chloromethyl styrene)/TiO
synthesized by in situ free radical polymerizing of 4-chloromethyl
styrene monomers in the presence of 3-(trimethoxysilyl) pro-
2
nanocomposite was
ꢀ
can draw the conclusion that the weight-loss around 450 C in the
TGA curve of PCMS/TiO
chains covalently attached to TiO
position temperature of PCMS/TiO
PCMS (420 C), indicated that no polymers adsorbed noncovalently
onto the surface of TiO
curve of PCMS/TiO
observed, which corresponded to the decomposition of the poly (4-
vinylpyridine) in the TGA curve of (PCMS-g-P4VP)/TiO . Moreover,
according to Fig. 9(d), we can conclude that the weight-loss of the
2
is a result of the decomposition of PCMS
2
nanoparticles. Higher decom-
(450 C) compared with pure
pylmethacrylate (MPS) modified nano-TiO
terminated poly (4-chloromethyl styrene)/TiO
PCMS-TEMPO/TiO ) was prepared by reacting of PCMS/TiO
sodium 4-oxy-TEMPO derived from TEMPO-OH. Macroinitiator
PCMS-TEMPO/TiO could initiates ‘‘living’’ free radical polymeri-
zation of 4-vinylpyridine monomers to yield the controlled graft
copolymer [(PCMS-g-P4VP)/TiO ]. TGA results indicated that no
polymers adsorbed noncovalently onto the surface of TiO nano-
2
. Thereafter, TEMPO-
macroinitiator
with
ꢀ
2
ꢀ
2
(
2
2
2
nanoparticles. In comparison with the TGA
, a new weight-loss region around 320 C was
ꢀ
2
2
2
2
ꢀ
2
(
PCMS-g-P4VP)/TiO
2
nanocomposite between 150 and 280 C is
particles. Also FTIR spectroscopy and TEM images investigation
provided direct and clear evidence for the presence of PCMS and
PCMS-g-P4VP) shell on nano-TiO core particles. Significantly, the
2
obtained nanocomposites showed a strong absorption of UV light
in the wavelength range of 300e400 nm. Thus, the prepared
nanocomposites could be used to block the UV radiation in the
accelerated, followed by the early degradation of the TEMPO
molecules at the end of poly (4-vinylpyridine) chains [44]. The
weight percent of grafted modifier, grafted PCMS and grafted P4VP
are calculated from the TGA curves and summarized in Table 3.
(
3.7. Transmission electron microscopy
2
mentioned wavelength range. The PCMS/TiO that was obtained
was easily dispersed in organic solvents such as toluene to give
a stable suspension. Yet, when the PCMS layer was changed to
a (PCMS-g-P4VP) layer, the dispersibility of the sample changed. In
other words, NMRP technique could be used as a powerful tool to
Direct and clear evidence of the PCMS and (PCMS-g-P4VP)
chemically bonded to TiO
only from TGA and FTIR spectroscopy but also from transmission
electron microscopy images. TEM images of the raw TiO nano-
particles (a), TiO nanoparticles encapsulated by PCMS (b) and
PCMS-g-P4VP)/TiO nanocomposite (c) are shown in Fig. 10.
Fig. 10(a) shows the TEM image of the raw TiO nanoparticles
2
nanoparticles were demonstrated not
2
2
modify TiO nanoparticles into useful materials.
2
(
2
Acknowledgments
2
consisting of agglomerated spherical particles. It is clearly
demonstrated in Fig. 10(b and c) that the PCMS and (PCMS-g-P4VP)
shell is formed on the particle surface. The polymer shell can be
seen with less contrast. Since the free PCMS and (PCMS-g-P4VP) has
been separated from the bonded PCMS and (PCMS-g-P4VP), Fig. 10
I express my gratitude to the Bonyade Melli Nokhbeghan Insti-
tute and Payame Noor University for supporting this project.
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