Photoreactive nanomatrix structure formed by graft-copolymerization of 1,9-nonandiol dimethacrylate onto natural rubber

Article abstract of DOI:10.1002/pola.24011

Formation of photoreactive nanomatrix structure was investigated by graft-copolymerization of an inclusion complex of 1,9-nonandiol dimethacrylate (NDMA) with β-cyclodextrin (β-CD) onto natural rubber particle using potassium persulfate (KPS), iert-butyl hydroperoxide/tetraethylenepentamine (TBHPO/TEPA), cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA), and benzoyl peroxide (BPO) as an initiator. The graft copolymer was characterized by ¹H NMR and FTlR after coagulation. The conversion of NDMA and the amount of residual methacryloyl group were found to be 58.5 w/w % and 1.81 w/w %, respectively, under the suitable condi tion of the graft-copolymerization. The morphology of the film specimen, prepared from the graft copolymer, was observed by transmission electron microscopy (TEM) after staining the film with OsO₄. Natural rubber particle of about 1.0 μm in diameter was dispersed in poly(NDMA) matrix of about 10 nm in thickness.

Full text of DOI:10.1002/pola.24011

Photoreactive Nanomatrix Structure Formed by Graft-Copolymerization
of 1,9-Nonandiol Dimethacrylate onto Natural Rubber
1
,2
1
1
1
YOSHIMASA YAMAMOTO, PATJAREE SUKSAWAD, NANTHAPORN PUKKATE, TATSUYA HORIMAI,
3
1,2
OSAMU WAKISAKA, SEIICHI KAWAHARA
1
Department of Materials Science and Technology, Faculty of Engineering, Nagaoka University of Technology,
Nagaoka, Niigata 940-2188, Japan
2
Center for Green-Tech Development in Asia, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
3
Tokai Rubber Industries Ltd., Komaki, Aichi 485-8550, Japan
Received 15 November 2009; accepted 6 March 2010
DOI: 10.1002/pola.24011
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: Formation of photoreactive nanomatrix structure
was investigated by graft-copolymerization of an inclusion
complex of 1,9-nonandiol dimethacrylate (NDMA) with b-cyclo-
dextrin (b-CD) onto natural rubber particle using potassium
persulfate (KPS), tert-butyl hydroperoxide/tetraethylenepent-
amine (TBHPO/TEPA), cumene hydroperoxide/tetraethylene-
pentamine (CHPO/TEPA), and benzoyl peroxide (BPO) as an
tion of the graft-copolymerization. The morphology of the film
specimen, prepared from the graft copolymer, was observed
by transmission electron microscopy (TEM) after staining the
4
film with OsO . Natural rubber particle of about 1.0 lm in
diameter was dispersed in poly(NDMA) matrix of about 10 nm
in thickness. VC 2010 Wiley Periodicals, Inc. J Polym Sci Part A:
Polym Chem 48: 2418–2424, 2010
1
initiator. The graft copolymer was characterized by H NMR
and FTIR after coagulation. The conversion of NDMA and the
amount of residual methacryloyl group were found to be 58.5
w/w % and 1.81 w/w %, respectively, under the suitable condi-
KEYWORDS: graft copolymers; graft-copolymerization; inclusion
chemistry; inclusion complex; nanomatrix structure; natural
rubber; rubber
INTRODUCTION Photoreactive nanomatrix structure is
a
sites is expected to enhance the mechanical properties after
UV-irradiation, which forms a three-dimensional network
structure in the nanomatrix.
novel functional nanophase separated structure, which con-
sists of a dispersoid of major elastomer and a matrix of
minor functional polymer having carbon–carbon double
bonds as a photoreactive site. The photoreaction of the poly-
mer in the nanomatrix may concrete the nanomatrix struc-
ture with not only crosslinking junctions of the elastomer in
dispersoid and chemical linkages between the elastomer and
the functional polymer but also crosslinking junctions of the
functional polymer in the nanomatrix.
In our previous work, the nanomatrix structure consisting of
a natural rubber particle as the dispersoid of 1 lm in diame-
ter and the functional polymer as the matrix of 15 nm in
thickness was formed by coagulating the natural rubber
particle covered with grafted functional polymer, such as
3–6
polystyrene and polymethyl methacrylate.
Furthermore,
the photoreactive rubber latex was prepared in our previous
work by graft-copolymerization of an inclusion complex of
In the previous work, we found that the nanomatrix struc-
ture played important roles in high proton conductivity of
1
,9-nonandiol dimethacrylate (NDMA) with a-cyclodextrin
7
1
(a-CD). A methacryloyl group of poly(NDMA) grafted onto
the natural rubber particle was confirmed to remain without
any reaction, while the other was used for the graft-copoly-
merization. Based on the results, the photoreactive nanoma-
trix structure may be formed by coagulating a latex of the
photoreactive rubber.
polymer electrolyte membrane and high elastic properties
2
of rubbery material, respectively. However, the resulting
electrolyte membrane and the rubbery material were inferior
in mechanical properties, such as less tensile strength and
low tear energy. This has been explained to be due to no
chemical linkages between the functional polymers in the
nanomatrix. To improve the properties, it is necessary to
introduce crosslinking junctions into the polymers in the
nanomatrix, as the chemical linkages between the functional
polymers prevent flowing the polymers in the nanomatrix. In
this regard, the nanomatrix structure with the photoreactive
However, the latex was not stabilized during the polymeriza-
tion, and a part of the reacted rubber particles were coagu-
lated at 52% of conversion. The coagulation has been
explained to be due to releasing a-CD from the inclusion com-
plex followed by crosslinking during graft-copolymerization.
Correspondence to: S. Kawahara (E-mail: kawahara@mst.nagaokaut.ac.jp)
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 2418–2424 (2010) V
2010 Wiley Periodicals, Inc.
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rubber latex (HANR: Golden Hope, Malaysia). tert-Butyl
hydroperoxide/tetraethylenepentamine (TBHPO/TEPA), cumene
hydroperoxide (CHPO), tetraethylenepentamine (TEPA), and
benzoyl peroxide (BPO) were purchased from NOF Corporation.
Sodium dodecyl sulfate (SDS, 98%) was purchased from Kish-
ida Chemical Co., Ltd. b-CD, potassium persulfate (KPS, 95%),
and chloroform-d (99.8%) were purchased from Wako Pure
Chemical Industry. Urea (99.5%), methanol (99.5%), acetone
(99.5%), and potassium bromide were purchased from Nacalai
Tesque, Inc. The reagents were used without further
purification.
1
0,11
Deproteinization
HANR latex was sieved with a stainless 200 mesh before
usage. HANR latex (300 g) placed in a 1 L beaker was
diluted with 2.0 w/w % of SDS aqueous solution (300 g) to
make 30 w/w % DRC latex before deproteinization. The
diluted latex was mixed with urea (0.6 g) and stirred for 1 h
at room temperature and it was subjected to centrifugation
4
FIGURE 1 Schematic representation for inclusion complex for-
mation of NDMA and b-CD before graft-copolymerization.
at 10 rpm and 288 K for 30 min to separate the rubber
cream fraction from serum fraction. The resulting cream
fraction, which mainly contains rubber, was added into
0.5 w/w % of SDS aqueous solution (200 g) in a 1 L beaker.
The mixture of the cream fraction and the SDS aqueous solu-
tion was stirred slowly at room temperature for 1 h to redis-
perse the rubber particle. The resulting latex was sieved
with a stainless 200 mesh and it was subjected to the cen-
trifugation and the redispersion twice to purify natural rub-
ber. For the last time of redispersion, the concentration of
SDS was decreased to be 0.1 w/w % of SDS aqueous solu-
tion. The resulting deproteinized natural rubber (DPNR) la-
tex was kept in a 500 mL glass bottle in the dark at room
temperature. DRC of the DPNR latex was measured as fol-
lows; DPNR latex (2 g) was poured into a small metal con-
tainer and it was dried in an oven at 323 K until a constant
weight was reached. The DRC was estimated from the weight
of the latex and dried rubber, as in the following eq. 1:
In fact, the graft-copolymerization was not completed; that is,
the coagulated particles were not covered with poly(NDMA).
To cover all particles at high conversion of graft-copolymeriza-
tion, thus, it is necessary to make a stable inclusion complex.
Recently, Ritter and coworkers reported that 1,4-butandiol
diacrylate completely penetrated the CD cavity when it formed
8
a complex with methylated b-CD, whereas in the case of
1
,4-butandiol dimethacrylate, the CD was located at the termi-
9
nal end of 1,4-butandiol dimethacrylate. Satav et al. demon-
strated that a methacryloyl group of 1,4-butandiol dimethacry-
late was protected with b-cyclodextrin (b-CD) having larger
cavity of about 6.6 Å in diameter to form the stable inclusion
complex. When we use b-CD to form the stable inclusion com-
plex, all particles may be covered with poly(NDMA) to make it
possible to form the photoreactive nanomatrix structure
which has seen ever.
W dried rubber
DRCðW=W %Þ ¼
ꢀ 100
(1)
Here, for the first time, we form the photoreactive nanoma-
trix structure through graft-copolymerization of the stable
inclusion complex prepared with b-CD and NDMA in water
Wlatex
(
Fig. 1). The formation of the inclusion complex was
1
3
1
confirmed by FTIR, solid state C NMR, H NMR, and X-ray
diffraction (XRD). A stability of the inclusion complex was
evaluated by determination of solubility product. The result-
ing inclusion complex was subjected to graft-copolymeriza-
tion onto natural rubber particle with various radical initia-
tors (Fig. 2). Effects of amount of the inclusion complex and
the radical initiator on conversion of NDMA were investi-
gated. The resulting graft copolymer was characterized by
1
H NMR, FTIR. The morphology of the graft copolymer was
observed by TEM.
EXPERIMENTAL
Materials
Natural rubber latex used in this study was about 60% dry
rubber content (DRC) of a commercial high-ammonia natural
FIGURE 2 Schematic representation for graft-copolymerization
of inclusion complex onto DPNR in latex stage.
GRAFT-COPOLYMERIZATION OF NDMA, YAMAMOTO ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 1 Conditions for Inclusion Complex Formation of
acetone in a Soxhlet apparatus under nitrogen atmosphere in
the dark and dried under reduced pressure for a week, in
which the removal of almost all free-polymer, isolated from
natural rubber, was completed by the extraction for 24 h.
Conditions of graft-copolymerization of inclusion complex
onto DPNR in latex stage are tabulated in Table 2.
NDMA and CD
Feed of NDMA (mol)
Feed of b-CD (mol)
0.044
0.044
400
303
5
0.044
0.044
400
323
5
0.044
0.044
400
363
5
Ion-exchanged water (mL)
Reaction temperature (K)
Reaction time (h)
Characterization
FTIR measurement was carried out using a JASCO FT-IR 410
ꢂ1
spectrometer with a resolution of 4 cm . The sample was
where Wdried rubber and Wlatex represent the weight of the
dried rubber and the latex, respectively.
mixed with potassium bromide powder in the ratio of 5 to
5 w/w %. The mixture was grinded in the mortar and it
was casted into a DR-81 diffusive reflection attachment.
9
Preparation of Inclusion Complex
b-CD was dissolved in ion-exchanged water. NDMA as a
divinyl monomer was added in stoichiometric amount and
the mixture was stirred at 363 K for 1–5 h. The complex
was precipitated out from the mixture. The precipitated com-
plex was filtered and it was washed with hot ion-exchanged
water to remove uncomplexed b-CD. The crystalline com-
plexes were dried at 323 K for 1 week under reduced pres-
sure. Conditions of inclusion complex formation of NDMA
and b-CD are tabulated in Table 1.
NMR measurements were carried out using a JEOL EX-400
NMR spectrometer operating at 399.65 and 100.4 MHz for
H and C, respectively. The sample was dissolved into chlo-
1
13
roform-d or dimethyl sulfoxide-d6 (DMSO-d ) without tetra-
6
methylsilane. Chemical shifts were referred to chloroform in
1
13
chloroform-d or to DMSO in DMSO-d6. H and C NMR
measurements were carried out at 323 and 298 K at the
pulse repetition time of 7 and 5 s, respectively.
1
3
Solid state C CP/MAS NMR measurements were carried
out with a JEOL ECA-400 NMR spectrometer at room tem-
perature with spin rate of 7 MHz, scan time of 1000 times
and contact time of 1 s. Hexamethylbenzene was used for
reference. Before measurement, samples were crushed by
JFC-300 cryogenic sample crusher.
Determination of Solubility Product
The inclusion complex (0.3 mmol) was suspended into water
ꢁ
(
10 mL). The suspension was shaken for 1 h at 30 C, and
ꢁ
allowed to stand for 1 h at 30 C. After filtration of the su-
ꢁ
pernatant, the filtrate was dried at 50 C under reduced
pressure to give free CD, which was identified with H NMR
1
measurement. The solubility product was determined by the
concentration of free CD estimated by gravimetric method.
Crystallinity changes in the complex formation of NDMA
with b-CD were confirmed by Mac Science MXP03HF22 X-
ray powder diffraction and image-plate photography using
graphite monomchromator with a voltage of 40 kV and a
current of 35 mA. The diffractogram was recorded in the 2y
Graft-Copolymerization
Graft-copolymerization of the inclusion complex onto DPNR
was carried out with a radical initiator. DPNR latex (500 g,
ꢁ
angle range between 5 and 70 .
2
0 w/w % DRC) was charged with N gas. Initiator and the
2
complex were added to the latex, respectively. The reaction
was carried out by stirring the latex at about 400 rpm for 2
h at 343 K. The unreacted NDMA was removed by using a
centrifuge. The as-prepared graft copolymer (gross polymer)
was obtained by dipping a glass tube into the reacted latex
and dried under reduced pressure at ambient temperature
for more than a week. The gross polymer was extracted with
Observation of morphology for the graft copolymer was
made with TEM, JEOL JEM-2100 at accelerating voltage of
200 kV. The ultra thin sections of the graft copolymer were
prepared by a microtome (Ultracut N, Reichert-Nissei FC S)
at a temperature lower than T of NR. The thin sections with
g
the thickness of about 100 nm were stained by OsO
room temperature for 5 min.
4
at
TABLE 2 Various Conditions of Graft-Copolymerization of Inclusion Complex onto DPNR in Latex Stage
Initiator
NDMA
Complex
Reaction
NDMA Content
(w/w %)
Conversion
(w/w %)
No.
(g/kg-Rubber)
(mol/kg-Rubber)
Temp. (K)
1
2
3
4
5
6
7
8
150
150
150
150
150
150
50
KPS
0.033
0.033
0.033
0.033
0.01
353
313
353
303
303
303
303
303
1.38
0.06
0.25
1.81
0.85
1.73
0.71
1.87
44.4
2.1
CHPO/TEPA
BPO
8.1
TBHPO/TEPA
TBHPO/TEPA
TBHPO/TEPA
TBHPO/TEPA
TBHPO/TEPA
58.5
27.3
55.6
69.0
30.1
0.1
0.033
0.033
300
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ARTICLE
FIGURE 4 Plot of percentage of complex formation versus
reaction time for the inclusion complex at various tempera-
tures; (n) 302 K, (~) 323 K, and (^) 363 K.
FIGURE 3 FTIR spectra for (A) NDMA, (B) b-CD, inclusion com-
plex of b-CD and NDMA prepared at 363 K for (C) 1 h, (D) 2 h,
temperature. The inclusion complex prepared from NDMA
(
E) 3 h, (F) 4 h, and (G) 5 h.
1
3
and b-CD at 363 K for 5 h was subjected to solid state
NMR, XRD, and H NMR measurements.
C
1
1
3
RESULTS AND DISCUSSION
Solid state C CP/MAS NMR spectra for the inclusion complex
and b-CD is shown in Figure 5. In the spectrum of b-CD, four
signals characteristic of C , C , C , C , C , and C of b-CD
Inclusion Complex Formation of NDMA and b-CD
6
2
3
5
4
1
Figure 3 shows FTIR spectra ranging from 1500 to 1900
ꢂ1
appeared at 62.2, 70–75, 81.0, and 102.2 ppm. Each signal
was observed as an overlapped signal due to each carbon of
glucose unit. After forming the inclusion complex, the spec-
trum showed apparent single signals for each carbon of glu-
cose unit accompanying signals of NDMA, which were
assigned as shown in Figure 5. It is well known that b-CD
retains less symmetrical cyclic conformation when it does not
cm for NDMA, b-CD and the inclusion complex of NDMA
with b-CD prepared at 363 K for 1–5 h, respectively. The
spectrum of the inclusion complex showed a broad peak at
ꢂ1
about 1640 cm , whereas the corresponding b-CD peak
ꢂ1
appeared at about 1649 cm . This may be attributed to the
1
2–15
interaction of NDMA within b-CD cavity.
As for NDMA, a
stretching vibration peak of carbon–carbon double bond and
carbonyl group appeared at about 1640 and 1719 cm
respectively. After forming the inclusion complex of NDMA
1
6–21
ꢂ1
include any guest into the cavity.
In contrast, apparent
,
single signals for each carbon of glucose unit of b-CD in the
inclusion complex indicate that symmetrical cyclic conforma-
tion of b-CD is formed, that is, same environment for each glu-
cose unit of b-CD due to formation of the inclusion complex.
ꢂ1
with b-CD, the peak height at 1719 cm
reaction time, while that at 1640 cm
decreased with
ꢂ1
did not vary. The
ꢂ1
decrease in the peak height at 1719 cm may be explained
to be due to the interaction between carbonyl group of
NDMA and b-CD at longer reaction time. The percentage of
the complex formation was estimated from a ratio of peak
Figure 6 shows XRD patterns for b-CD and the inclusion com-
plex, respectively. The XRD pattern of b-CD was distinguished
from that of the inclusion complex. The difference in XRD
ꢂ1
ꢂ1
height at 1719 cm to that at 1640 cm , as in the follow-
ing eq. 2:
Complex formation ð%Þ ¼
ðIC¼O=IC¼CÞ
ꢂ ðIC¼O=IC¼CÞInclusion complex
Monomer
ꢀ
100 ð2Þ
ðIC¼O=IC¼CÞMonomer
where I
and I
are peak height of a carbonyl group at
C ¼¼ O
ꢂ1
C¼C
ꢂ1
1719 cm and a carbon–carbon double bond at 1640 cm
,
respectively.
Figure 4 shows a plot of percentage of complex formation
versus reaction time at various temperatures. The complex
formation of NDMA with b-CD increased with increasing
reaction time. Figure 4 also shows the effect of temperature
on the complex formation. An ability to form the complex at
1
3
363 K was higher than those at 303 and 323 K. This may be
FIGURE 5 C CP/MAS NMR spectra for (A) inclusion complex
and (B) b-CD.
attributed to higher solubility of NDMA into water at higher
GRAFT-COPOLYMERIZATION OF NDMA, YAMAMOTO ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
peak at 4.1 ppm corresponding to four protons of methylene
group adjacent to methacryloyloxy group of NDMA
(
AOCH A) was compared with the peak at 4.82 ppm corre-
2
sponding to seven protons of methine group in b-CD (H1),
although NDMA might be released from b-CD in DMSO-d6.
The integration showed a ratio of 1:1 of NDMA and b-CD in
the inclusion complex. This suggests that the inclusion com-
plex was formed in a ratio of 1:1.
To evaluate the complex stability, a solubility product of the
resulting inclusion complex, which was difficult to dissolve into
water, was compared with the inclusion complex of NDMA with
7
a-CD prepared in our previous study. The solubility product
(Ksp) at an equilibrium state is expressed as follows:
CD ꢃ NMDA Ð CD þ NDMA
Ksp ¼ ½CDꢄ½NDMAꢄ
FIGURE 6 XRD diffractograms for (A) b-CD and (B) inclusion
(
3)
complex.
pattern may indicate a change in crystalline form due to the
formation of the inclusion complex. The main peaks for b-CD
where [CD] and [NDMA] are concentration of CD and NDMA
dissociated from the inclusion complex in water, respectively.
eq. 3 is converted to eq. 4, as the inclusion complex was
formed in a ratio of 1:1.
ꢁ
ꢁ
ꢁ
ꢁ
appeared at 2h ¼ 12.2 , 14.3 , 21.8 , and 22.7 , which indicate
a cage-type packing, whereas inclusion complex showed new
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
peaks at 2h ¼ 7.6 , 11.3 , 12.8 , 16.8 , 20.1 , and 33.16
2
accompanying disappearance of the main peaks for native b-
Ksp ¼ ½CDꢄ
(4)
ꢁ
ꢁ
CD. As is well known, the peak at 2h ¼ 7.6 and 20.1 in the
inclusion complex is characteristic for the channel structure of
b-CD including long guest molecules and polymers in particu-
The estimated Ksp for the inclusion complex with b-CD and
ꢂ6
ꢂ6
a-CD in water were 1.16 ꢀ 10 and 3.29 ꢀ 10 , respec-
tively. This result indicates that the inclusion complex with
b-CD was more stable than that with a-CD in water.
9
,12,19–24
lar.
Furthermore, the absence of uncomplexed b-CD
was confirmed in the inclusion complex as there is no peaks of
b-CD. Therefore, it was demonstrated that the inclusion com-
plex was formed with NDMA and b-CD.
Graft-Copolymerization of Inclusion Complex onto
DPNR Particle
Before graft-copolymerization, natural rubber latex was puri-
1
To determine a ratio of NDMA and b-CD, H NMR spectra for
NDMA, the inclusion complex, and b-CD were measured in
fied to mainly remove protein which is well known as radi-
9
DMSO-d6 as shown in Figure 7. Six signals for NDMA and
25
cal scavenger to disturb graft-polymerization.
Figure 8
1
five signals for b-CD appeared in the H NMR spectra,
respectively. These signals were assigned as shown in Figure
9
7
, according to the previous literature. After forming the
1
inclusion complex, all signals in H NMR spectrum were
attributed to those of b-CD and NDMA. To estimate a ratio of
NDMA and b-CD in the inclusion complex, integration of the
1
FIGURE 8 H NMR spectra for (A) DPNR, (B) NDMA, and (C)
DPNR-graft-poly(NDMA) (after acetone extraction) prepared
from 20%DRC DPNR, 15% inclusion complex for 3 h at 303 K
(solvent: chloroform-d).
1
FIGURE 7 H NMR spectra for (A) NDMA monomer, (B) b-CD,
6
and (C) inclusion complex (solvent: DMSO-d ).
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ARTICLE
This suggests that the formation of the inclusion complex
maintained the methacryloyl group of NDMA after graft-
copolymerization.
Figure 9 shows FTIR spectra ranging from 1600 to 1800
ꢂ1
cm
for DPNR, DPNR-graft-poly(NDMA) prepared with
TBHPO/TEPA, CHPO/TEPA, BPO, or KPS as an initiator,
respectively. A peak height was normalized with a height of
ꢂ1
reference peak at 1660 cm , which was identified to a
stretching vibration of carbon–carbon double bond of natural
rubber. As for DPNR-graft-poly(NDMA), a stretching vibra-
tion peak of carbonyl group of NDMA appeared at 1730
ꢂ1
cm . A conversion and content of NDMA in DPNR-graft-
FIGURE 9 FTIR spectra of (A) DPNR, DPNR-graft-NDMA copoly-
mer using (B) TBHPO/TEPA, (C) CHPO/TEPA, (D) BPO, and (E)
KPS as a initiator.
poly(NDMA) were estimated from a ratio of the peak height
ꢂ1
ꢂ1
at 1730 cm to that at 1660 cm by using a calibration
curve.
1
shows H NMR spectra for DPNR, NDMA and graft copoly-
Content of NDMA ð%Þ ¼
mer (DPNR-graft-poly(NDMA)) prepared from 20 w/w %
DRC of DPNR latex and 150 g/kg-rubber of the inclusion
complex in the presence of 0.033 mol/kg-rubber of TBHPO/
TEPA at 303 K for 3 h. Signals in the spectra for DPNR and
Weight of NDMA unit in the graft ꢂ copolymer
ꢀ
100 ð6Þ
Weight of graft ꢂ copolymer
Conversion of NDMA ð%Þ ¼
7
NDMA were assigned according to the literature. After the
Weight of NDMA unit in the graft ꢂ coplymer
ꢀ
100 ð7Þ
graft-copolymerization of the inclusion complex onto DPNR
particle, two signals at 5.58 and 6.15 ppm appeared in the
spectrum, which were assigned to unsaturated methylene
protons of methacryloyl group. As the signals still appeared
even after extraction of the graft copolymer with acetone for
Weight of feed of NDMA
Table 2 shows the estimated conversion and content of
NDMA. The conversion of NDMA was dependent on initiator,
in which the highest conversion, 69.0 w/w %, was accom-
plished by using 0.033 mol/kg-rubber of TBHPO/TEPA. On
the other hand, the conversion of NDMA increased with
decreasing feed of the inclusion complex, while the content
of NDMA was reached to plateau at feed of 150 g/kg-rubber
of inclusion complex. It is quite noteworthy that no coagula-
tion occurred during graft-copolymerization even at higher
conversion of more than 58.5%. This may be attributed to
formation of the stable inclusion complex between NDMA
and b-CD, because b-CD free from NDMA is formed an inclu-
2
4 h, the residual methacryloyl group is considered to link
with natural rubber. Thus, amount of residual methacryloyl
group after graft-copolymerization was estimated, as in the
following eq. 5:
Amount of residual methacryloyl group ð%Þ
I5:58=ðI4:10ꢂ4:20=4Þ
graft copolymer
¼
ꢀ 100 ð5Þ
I5:58=ðI4:10ꢂ4:20=4Þmonomer
where I is the intensity of the signals and subscript numbers
represent chemical shift (ppm) of the signals. The estimated
value of amount of residual methacryloyl group is 45.3%.
2
6–28
sion complex with SDS, which may coagulate the latex.
A suitable condition of the graft-copolymerization was
FIGURE 10 TEM photographs for
DPNR-graft-poly(NDMA),
20,000, (b): ꢀ5000.
(a):
ꢀ
GRAFT-COPOLYMERIZATION OF NDMA, YAMAMOTO ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
determined to be 150 g/kg-rubber of inclusion complex and
7 Pukkate, N.; Horimai, T.; Wakisaka, O.; Yamamoto, Y.; Kawa-
0.033 mol/kg-rubber of TBHPO/TEPA. The resulting product,
hara, S. J Polym Sci Part A: Polym Chem 2009, 47, 4111–4118.
DPNR-graft-poly(NDMA), prepared under suitable condition
was subjected to TEM observation.
8
Sarvothaman, M. K.; Ritter, H. Macromol Rapid Commun
004, 25, 1948–1952.
2
TEM photographs for DPNR-graft-poly(NDMA) are shown in
Figure 10, in which a gloomy domain is natural rubber and a
bright domain is poly(NDMA). As is clearly seen, the natural
rubber particle of about 1.0 lm in diameter was dispersed
in poly(NDMA) matrix of 10 nm in thickness to form nano-
matrix structure, while it did not contain poly(NDMA).
Furthermore, a volume fraction of poly(NDMA) matrix was
estimated by image-analysis of the photograph to be about 3
v/v %, which corresponded to 1.81 v/v % estimated from
NDMA content shown in Table 2. These results indicate that
the graft-copolymerization occurs only on the surface of nat-
ural rubber particle. This implies that formation of the inclu-
sion complex changed polarity of hydrophobic NDMA to in-
hibit penetrating NDMA into hydrophobic natural rubber
particle. Consequently, the photoreactive nanomatrix struc-
ture was formed in spite of as low as 1.81 w/w % of NDMA
content, which has seen ever.
9 Satav, S. S.; Karmalkar, R. N.; Kulkarni, M. G.; Mulpuri, N.;
Sastry, G. N. J Am Chem Soc 2006, 128, 7752–7753.
1
0 Kawahara, S.; Klinklai, W.; Kuroda, H.; Isono, Y. Polym Adv
Technol 2004, 15, 181–184.
1
1 Klinklai, W.; Saito, T.; Kawahara, S.; Tashiro, K.; Suzuki, Y.;
Sakdapipanich, J. T.; Isono, Y. J Appl Polym Sci 2004, 93,
5
55–559.
1
2 Jambhekar, S.; Casella, R.; Maher, T. Int J Pharm 2004, 270,
1
49–166.
13 Ansari, M. T.; Iqbal, I.; Sunderland, V. B. Arch Pharm Res
2009, 32, 155–165.
1
4 Pretsch, T.; Jakob, I.; M u¨ ller, W. Polym Degrad Stab 2009,
9
4, 61–73.
1
5 Chen, X.; Chen, R.; Guo, Z.; Li, C.; Li, P. Food Chem 2007,
1
01, 1580–1584.
1
6 Harada, A.; Li, J.; Kamachi, M. Macromolecules 1993, 26,
CONCLUSIONS
5
698–5703.
The photoreactive nanomatrix structure was formed by
graft-copolymerization of the stable inclusion complex of
NDMA with b-CD onto deproteinized natural rubber. The
content, the conversion, and the residual methacryloyl group
of NDMA for the graft-copolymerization were 1.81, 58.5, and
17 Gidley, M. J.; Bociek, S. M. J Am Chem Soc 1988, 110,
3820–3829.
1
8 Martinez, G.; Gomez, M. A.; Villar-Rodil, S.; Garrido, L.;
Tonelli, A. E.; Balik, C. M. J Polym Sci Part A: Polym Chem
2
007, 45, 2503–2513.
4
5.3%, respectively, at NDMA feed of 150 g/kg-rubber and
1
9 Harada, A.; Nishiyama, T.; Kawaguchi, Y.; Okada, M.; Kama-
initiator concentration of 0.033 mol/kg-rubber. TEM observa-
tion of the resulting graft copolymer showed that natural
rubber particle of about 1.0 lm in diameter was dispersed
in poly(NDMA) matrix of 10 nm in thickness.
chi, M. Macromolecules 1997, 30, 7115–7118.
0 Harada, A.; Suzuki, S.; Okada, M.; Kamachi, M. Macromole-
cules 1996, 29, 5611–5614.
2
2
1 Li, J.; Yan, D.; Jiang, X.; Chen, Q. Polymer 2002, 43,
2
625–2629.
REFERENCES AND NOTES
22 Harada, A.; Okada, M.; Li, J.; Kamachi, M. Macromolecules
995, 28, 8406–8411.
1
1
Kawahara, S.; Suksawad, P.; Yamamoto, Y.; Kuroda, H. Mac-
romolecules 2009, 42, 8557–8560.
23 Jiao, H.; Goh, S. H.; Valiyaveettil, S. Macromolecules 2001,
4, 8138–8142.
3
2
Kawahara, S.; Yamamoto, Y.; Fujii, S.; Isono, Y.; Niihara, K.;
Jinnai, H.; Nishioka, H.; Takaoka, A. Macromolecules 2008, 41,
24 Rusa, C. C.; Bullions, T. A.; Fox, J.; Porbeni, F. E.; Wang, X.;
4510–4513.
Tonelli, A. E. Langmuir 2002, 18, 10016–10023.
3
Pukkate, N.; Yamamoto, Y.; Kawahara, S. Colloid Polym Sci
25 Tuampoemsab, S.; Sakdapipanich, J. Kautsch Gummi
2008, 286, 411–416.
Kunstst 2007, 57, 678–684.
4
Pukkate, N.; Kitai, T.; Yamamoto, Y.; Kawazura, T.; Sakdapi-
26 Xu, Y.; Bolisetty, S.; Ballauff, M.; M u¨ ller, A. H. E. J Am
panich, J.; Kawahara, S. Eur Polym Mater 2007, 43, 3208–3214.
Chem Soc 2009, 131, 1640–1641.
5
Kawahara, S.; Kawazura, T.; Sawada, T.; Isono, Y. Polymer
27 Yei, D. R.; Kuo, S. W.; Fu, H. K.; Chang, F. C. Polymer 2005,
2003, 44, 4527–4531.
46, 741–750.
6
Hayatiyusof, N.; Kawahara, S.; Said, M. J Rubb Res 2008, 11,
28 Mwakibete, H.; Cristantino, R.; Bloor, D. M.; Wyn-Jones, E.;
97–110.
Holzwarth, J. F. Langmuir 1995, 11, 57–60.
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