Synthesis of photo-switchable 3-FcAB -modified polymer particles

Article abstract of DOI:10.1039/c1nj20189a

3-Ferrocenylazobenzene (3-FcAB)-containing polymers were prepared using solution polymerization and emulsion polymerization. Polymer A, prepared by solution polymerization followed by re-precipitation, and Polymer B, prepared by emulsion polymerization, had spherical shapes with the outer diameters of ca. 300 nm and ca. 20 nm, respectively. Both the polymers responded to green light, UV light, and blue light in solution like monomeric 3-FcAB and its derivatives. In the solid state, Polymer A exhibited both isomerization and re-orientation behaviors upon light irradiation, indicating a possibility to achieve a light-induced shape change by the re-orientation of the chromophore. On the other hand, Polymer B underwent simple photoisomerization behaviors, which is more preferable for developing a switching system using spectroscopic detection of the isomerization behaviors of nano-dots.

Full text of DOI:10.1039/c1nj20189a

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New Journal of Chemistry
A journal for new directions in chemistry
www.rsc.org/njc
Volume 35 | Number 10 | October 2011 | Pages 1909–2384
ISSN 1144-0546

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PAPER
Synthesis of photo-switchable 3-FcAB-modified polymer particleswz
Kosuke Namiki, Masaki Murata, Shoko Kume and Hiroshi Nishihara*
Received (in Victoria, Australia) 1st March 2011, Accepted 3rd May 2011
DOI: 10.1039/c1nj20189a
3-Ferrocenylazobenzene (3-FcAB)-containing polymers were prepared using solution
polymerization and emulsion polymerization. Polymer A, prepared by solution
polymerization followed by re-precipitation, and Polymer B, prepared by emulsion
polymerization, had spherical shapes with the outer diameters of ca. 300 nm and ca. 20 nm,
respectively. Both the polymers responded to green light, UV light, and blue light in solution
like monomeric 3-FcAB and its derivatives. In the solid state, Polymer A exhibited both
isomerization and re-orientation behaviors upon light irradiation, indicating a possibility to
achieve a light-induced shape change by the re-orientation of the chromophore. On the other
hand, Polymer B underwent simple photoisomerization behaviors, which is more preferable
for developing a switching system using spectroscopic detection of the isomerization behaviors
of nano-dots.
Introduction
Photochromic molecules have been intensely studied because
their physical properties can easily be switched by light.1
Integrations of these molecules have attracted much attention
because of their potential application to photo-switchable
molecular devices.2 Azobenzene is one of the most popular
photo-switchable molecules and its assemblies have been
extensively investigated. Assemblies of azobenzene derivatives
such as polymers,3 monolayers,4 and colloids5 have especially
attracted much attention because they can achieve immobili-
zation and high-density of the switching units.
We have reported that 3-ferrocenylazobenzene (3-FcAB)
exhibits a redox-conjugated reversible photoisomerization in
solution6 and on the surface of an electrode.7 As shown in
Scheme 1 Redox-coupled photoisomerization of 3-ferrocenylazobenzene.
Scheme 1, the excitation of the metal-to-ligand charge transfer
(MLCT) band with 546 nm green light causes the trans-to-cis
isomerization of 3-FcAB in the reduced Fe(II) state in addition
be controlled reversibly by a single green light coupled
to the normal UV and blue light response (trans-to-cis
with the redox reaction between Fe(II) and Fe(III). Assemblies
isomerization by excitation of the azo p–p* band with
365 nm UV light, and the reverse cis-to-trans isomerization
of this compound therefore have a possibility to achieve
photo-switching without dual light sources, and this simpler
by excitation of the cis-azo n–p* band with 436 nm blue light).
photoswitch will be advantageous for construction of small
Once 3-FcAB is oxidized to 3-FcAB+ in the Fe(III) state, the
size devices. The aim of this study is to introduce 3-FcAB
MLCT band disappears and the cis-to-trans reverse isomerization
in acrylic polymers for the purpose of integrating the
occurs by excitation of the cis-azo n–p* band with the
same 546 nm light. By using this feature, this compound can
functional molecule and to examine the photo-responses of
the 3-FcAB-containing polymers. We have attempted two
types of polymerization, one is solution polymerization and
the other is emulsion polymerization,8 and the polymers thus
Department of Chemistry, School of Science,
The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033,
Japan. E-mail: nisihara@chem.s.u-tokyo.ac.jp
w Submitted to the themed issue dedicated to Prof. Didier Astruc.
z Electronic supplementary information (ESI) available: FT-IR and
1H NMR spectra of monomers and polymers. See DOI: 10.1039/
c1nj20189a
obtained are Polymer A and Polymer B, respectively. Both
methods afforded spherical polymer shapes but their sizes were
different. We discuss the differences of the structures and
characteristics of the polymers depending on the preparation
methods.
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tert-butoxide and 3-ferrocenyl-40-hydroxymethylazobenzene
to give Polymer A. As for modification of poly(2-bromoethyl
acrylate) formed by emulsion polymerization with 3-FcAB, the
reaction was carried out in suspension to give Polymer B. The
modification reactions occurred only at the outer sphere since
the solubility decreased rapidly as the reactions proceeded.
3-Ferrocenyl-40-((2-(acryloyloxy)ethoxy)methyl)azobenzene
(Monomer) was prepared as a reference.
Results and discussion
Synthesis and characterization
There are many polymerization types, i.e., solution polymeriza-
tion, liquid phase bulk polymerization, gas phase polymerization,
solid phase polymerization, suspension polymerization, and
emulsion polymerization. To create size-controlled discrete
polymer particles, solution polymerization and emulsion
polymerization were chosen in this study.
IR spectra of 3-FcAB, Monomer, Polymer A, and Polymer B
are similar to each other, containing a peak around 1600 cmꢀ1
attributable to the azo NQN stretching. A peak around
1700 cmꢀ1 ascribed to the CQO stretching of the carboxyl
group or the ester group in Monomer was slightly shifted in
higher wavenumbers in the polymers because the conjugation
of CQO with the double bond is lost by polymerization
(Fig. S1, ESIz). In the spectrum of Polymer B, the intense
absorption at 1227 cmꢀ1 due to sodium dodecyl sulfate (SDS)
was not observed, indicating that the amount of residual SDS
was very small.
First, we attempted solution polymerization and emulsion
polymerization of 3-ferrocenyl-40-acryloylmethoxyazobenzene,
but only trace amounts of polymer were obtained. This failure
can be ascribed to the involvement of the ferrocene moiety,
which works as a radical scavenger.9 The polymers containing
3-FcAB were, therefore, prepared by the modification of the
bromide substituted polymer compounds (Scheme 2). The
solution polymerization reaction of 2-bromoethyl acrylate was
carried out both in toluene and in cyclohexane. Polymerization
proceeds in both solvents almost quantitatively. In the emulsion
polymerization process, sodium dodecyl sulfate (SDS) was
used as an emulsifier and the monomer was well dispersed in
water as a stable monomer micelle, so that the mixture of the
monomer and SDS in water was transparent. Because of the
relatively small diameter of the formed polymer (ca. 20 nm,
vide infra), the surface energy might be low enough to emulsify
a large part of the monomer and the polymerization reaction
was like microemulsion polymerization. The generated polymer
was hardly soluble in organic solvents (B0.1 g per 100 mL in
chloroform, THF, or toluene) and almost insoluble in methanol
because of its high degree of polymerization. The surfactant
must be totally removed because the existence of amphiphilic
molecules disturbs the ether synthesis at the next 3-FcAB-
modification reaction. As the surfactant could not be removed
by reprecipitation by chloroform–methanol, the polymer was
washed vigorously with water and methanol. The polymer
became further insoluble on removing the surfactant by
washing with water.
The 1H NMR spectrum of poly(2-bromoethyl acrylate)
exhibits broadening of all peaks typical to polymers with short
relaxation times (Fig. S2, ESIz). On the other hand, the peaks
in the spectrum of Polymer A are broad but the peaks of the
ferrocene part are relatively sharp (Fig. S2, ESIz). This is
probably because the mobility of each part of the polymer is
different and the 3-FcAB part, as a side chain of the polymer,
can move freely. The exchange ratio in the 3-FcAB-modification
reaction was estimated to be ca. 20% for Polymer A from the
1
signal integration of the H NMR spectrum.
For scanning electron microscope (SEM) analysis, Polymer A
was reprecipitated from a THF solution with an equal
volume of water10 and the resulting suspension was dropped
on gold-deposited mica (Au/mica), and Polymer B in a 1,4-
dioxane solution was dropped on Au/mica. Both polymers
are composed of spherical particles and the outside diameters
were ca. 300 nm for Polymer A and ca. 20 nm for Polymer B
as shown in Fig. 1. The diameter of Polymer A particles was
poly-dispersed as shown in Fig. S3 (ESIz), where larger
particles might be generated by the aggregation of polymer
Modification of poly(2-bromoethyl acrylate) formed by
solution polymerization was performed by addition of sodium
Scheme 2 Synthesis of Polymer A, Polymer B and Monomer.
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by emulsion polymerization were rigid enough to be un-
changed in their shapes and sizes in the sample preparation
process.
Photoisomerization behaviors in solution
UV-vis absorption spectra of Monomer, Polymer A, and
Polymer B are shown in Fig. 2. The exchange ratio of
Polymer B in the 3-FcAB-modification reaction was estimated
at ca. 50% from the absorbance of the spectrum assuming a
molar extinction coefficient of 2 ꢁ 104 Mꢀ1 cmꢀ1, which is a
regular value for azobenzene derivatives. The lmax value of the
p–p* band is not shifted for Polymer A, whereas it is shifted to
the longer wavelength by 5 nm for Polymer B, suggesting that
the azobenzene chromophores are buried in the polymer and
experience a more polarizable environment than dioxane.
Fig. 1 SEM images of the re-precipitated Polymer A on Au/mica (A)
and Polymer B on Au/mica (B).
particles at the stage of solvent evaporation. On the other
hand, the particles of Polymer B were mono-dispersed as
shown in Fig. 1B. From this result, polymer particles prepared
The photoisomerization behavior of Polymer
A and
Polymer B in 1,4-dioxane were observed by UV-vis spectro-
scopy and the results are shown in Fig. 3. The photoisomeri-
zation behaviors are summarized in Table 1. They show
photo-responses with three different wavelength lights at
365, 436 and 546 nm, similar to 3-FcAB and its derivatives.
The smaller amount of the generated cis molar ratio by 546 nm
Table 1 Summary of the electronic spectral changes and isomerization
behaviors of 3-FcAB in polymers
%cis molar ratio
UV
p–p*/nm MLCT/nm %MLCT
Green
Sample
(Polymer A)
1,4-Dioxane 326
440
450
8
20
59
10
15
5
Solidb
(Polymer B)
344
1,4-Dioxanea 330
Chloroforma 325
436
441
450
9
18
15
54
10
12
17
9
5
Solidb
339
a
b
Polymer was dissolved by ultrasonication. A 1,4-dioxane solution
was cast on a glass plate.
Fig. 2 Scaled UV-vis absorption spectra of Polymer A (solid line),
Polymer B (dotted line) and Monomer (dash-dotted line) in 1,4-dioxane.
Fig. 3 UV-vis absorption spectra of Polymer A (A) and Polymer B (B) in 1,4-dioxane (orange line) and its 546 nm (green line), 365 nm (purple
line), and 436 nm (blue line) photo-irradiated spectra. Inset: differences in the UV-vis absorption spectra between before and after 546 nm (green
line), 365 nm (purple line), and 436 nm (blue line) irradiation.
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green light irradiation of Polymer A (15%) and Polymer B
(17%) compared with 3-FcAB (35%) can be interpreted to be
because of the substituent effect,6b because the absorption at
546 nm is weaker. The rate constant of thermal cis-to-trans
3.3(5) ꢁ 10ꢀ5 sꢀ1 and 5(1) ꢁ 10ꢀ5
s
ꢀ1, respectively). The
solutions of the oxidized polymers were placed in the dark and
were irradiated by 546 nm light. The UV-vis absorption
spectra and their time-course change in the dark and upon
546 nm light irradiation are shown in Fig. 4. The azo p–p*
band of the polymers in the trans-form appeared at 326 nm
and 350 nm for Polymer A and Polymer B, respectively,
whereas lmax of the band of the oxidized monomer in the
trans-form was observed at 312 nm.w The large shift of the
azo p–p* band in Polymer B is supposed to be induced by
the aggregation of the 3-FcAB part in the polymer by the
hydrophilic effect like an inverse micelle, because the ferrocene
part was ionized and became hydrophilic by oxidation. From
the spectral changes, it is suggested that the oxidized cis-
isomer in the polymers was converted to the trans-isomer with
green light. The amount of increase of the absorbance at the
azo p–p* band was about the same as that of decrease in their
reduced state. This fact suggests that the cis-isomers generated
by the green-light irradiation in their reduced states were
totally converted to the trans-isomers by the irradiation of
green light.
isomerization of Polymer B at 20 1C was 3(1) ꢁ 10ꢀ5 sꢀ1
,
which is comparable to that of 3-FcAB (5(1) ꢁ 10ꢀ5
s
ꢀ1).
To achieve the reversible isomerization controlled by
single green light, the stability and light-response of the cis-
isomer in the ferrocenium state are very important. The
isomerization behaviors of Polymer A and Polymer B in the
oxidized state were examined by the UV-vis spectral measure-
ments. At first, Polymer A and Polymer B in dichloromethane
were irradiated by 546 nm green light to generate their cis-
isomers. From the UV-vis spectra of these solutions, the
ratios of the photogenerated cis-isomers were estimated to
be 20% for Polymer A and 11% for Polymer B. After the
light irradiation, 10 eq. of iodine were added to the solution
to oxidize the polymers from ferrocene to ferrocenium.
The oxidized cis-isomer was stable in the dark (the rate
constants of thermal cis-to-trans isomerization of Polymer A
and Polymer B at 20 1C in the oxidized states were
Fig. 4 UV-vis absorption spectra of Polymer A (A) and Polymer B (C) oxidized with 10 eq. of iodine in dichloromethane followed by 546 nm
irradiation, where absorption of iodine was subtracted, and the corresponding time course change in absorbance at 350 nm (B and D, respectively),
where K and J indicate before and after starting 546 nm light irradiation. Inset of A and C: differences in the UV-vis absorption spectra between
before and after 546 nm light irradiation.
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Photoisomerization behaviors in the solid state
Polymer B is more preferable for a spectroscopic detection of
the isomerization behaviors.
The photoisomerization behaviors of Polymer A and Polymer B
in the solid state were also examined. Samples were deposited on
Au/mica, SEM images of which show spherical particles with the
outside diameter of ca. 300 nm for Polymer A and ca. 20 nm for
Polymer B (vide supra, Fig. 1). In the UV-vis absorption spectra
of Polymer A and Polymer B, the p–p* band was 14 nm and
19 nm shifted to a longer wavelength, respectively (Fig. 5). The
shifts are ascribed to the formation of J-aggregates of 3-FcAB in
the polymers.
Conclusions
3-FcAB was introduced to the polymers prepared by solution
polymerization and emulsion polymerization, and the prepared
polymer particles with the outer diameters of ca. 300 nm and
ca. 20 nm, respectively, were isomerized by UV, blue, and
green light both in solution and in solid state. Moreover, the
polymers can be controlled by the green-light-response and by
the redox reaction of their ferrocene parts (Scheme 3). Therefore,
it is concluded that these polymer particles are possible candidates
to act as nano-sized photo-memories or switches.
Photoirradiation caused spectral changes, which indicate
that the polymers underwent photo-response against UV,
green and blue light, although the cis molar ratios with UV
and green light were decreased because of the J-aggregation of
the chromophores (Fig. 5). The photoisomerization behaviors
of these polymers are different. As shown in Fig. 5A, the p–p*
band of Polymer A was not simply decreased with light
irradiation. The spectral changes of the p–p* band can be
deconvoluted to two components. One component is a simple
decrease of the original p–p* band of the trans-isomer. The
other is a generation of the new p–p* band of the trans-isomer
at a shorter wavelength region. The latter can be ascribed as a
generation of H-aggregated chromophores. Therefore, these
spectral changes suggest that the aggregation state of the
polymer was changed by light irradiation. The driving force
of these changes might be a re-orientation of the chromo-
phores by a continuous shape change caused by light irradia-
tion. On the other hand, the spectral changes of Polymer B
can be interpreted as simple trans-to-cis and cis-to-trans isomeri-
zation behaviors. These results suggest that the orientation
of the chromophore in Polymer B was not affected by
light irradiation because of its rigid structure. From these
isomerization behaviors, it can be concluded that Polymer A
has a possibility to detect the isomerization behavior by the
re-orientation of the chromophores in the solid state, and
Experimental
General
Ultra pure water was generated from a water purification
system (Yamato, Autopure WD500). Solvents and reagents
were used as received from the commercial sources, and
otherwise noted. 2-Bromoethyl acrylate11 and 3-ferrocenyl-
40-hydroxymethylazobenzene7 were prepared according to the
literature. All the reactions in this section were done under a
nitrogen atmosphere.
Synthesis
3-Ferrocenyl-40-acryloylmethoxyazobenzene. 3-Ferrocenyl-
40-hydroxymethyl-azobenzene (0.603 g, 1.52 mmol) and
triethylamine (1 mL, 0.73 g, 3.6 mmol) were dissolved in
20 mL of dehydrated dichloromethane under an argon
atmosphere. Acryloyl chloride (1 mL, 1.12 g, 12.4 mmol)
was added dropwise to the solution at 0 1C. The resulting
mixture was stirred for 2 h at room temperature. 50 mL of 3%
HCl–water was added and the organic layer was collected and
Fig. 5 UV-vis absorption spectra of Polymer A (A) and Polymer B (B) in the solid state (orange line) and their changes with 546 nm (green line),
365 nm (purple line), and 436 nm (blue line) light irradiation. Inset: differences in the UV-vis absorption spectra between before irradiation and
after 546 nm (green line), 365 nm (purple line), and 436 nm (blue line) light irradiation.
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Scheme 3 Photochromic behaviors of Polymer A and Polymer B.
dried with sodium sulfate. After removing the solvent, orange
oil was purified by silica-gel column chromatography with
chloroform–hexane (from 1 : 9 v/v to 1 : 1 v/v) as eluent and the
second fraction was collected. Needle crystals were obtained
by recrystallization with methanol–hexane at ꢀ30 1C. Yield:
0.620 g (0.138 mmol, 90.6%). 1H NMR for 3-ferrocenyl-
40-acryloylmethoxyazobenzene (400 MHz, CDCl3) d (ppm)
8.01 (s, 1H, C6H4), 7.94 (d, J = 8.2 Hz, 2H, C6H4), 7.73
(d, J = 7.8 Hz, 1H, C6H4), 7.58 (d, J = 7.8 Hz, 1H, C6H4),
7.52 (d, J = 8.2 Hz, 2H, C6H4), 7.42 (dd, J = 7.8 Hz, 7.8 Hz, 1H,
C6H4), 5.99 (m, 1H,QCH2), 5.35 (d, J = 17.0 Hz, 1H,QCH),
5.25 (d, J = 10.5 Hz, 1H, QCH2), 4.77 (s, 2H, C5H4), 4.62
(s, 2H, CH2), 4.38 (s, 2H, C5H4), 4.09 (s, 5H, C5H5).
4.37 (s, 2H, C5H4), 4.07 (s, 5H, C5H5), 3.55 (t, J = 6.0, 2H,
O–CH2).
Polymerization of 2-bromoethyl acrylate in solution
2-Bromoethyl acrylate (1.74 g, 9.72 mmol) was dissolved in
toluene (10 mL, HPLC grade, KANTO CHEMICAL Co.
Inc.) and the solution was degassed with nitrogen for 15 min.
2,20-Azobisisobutyronitrile (0.027 g, 0.16 mmol) was added to
the solution and the solution was stirred for 22 h at 60 1C. The
solution was then cooled by water and hexane was added to
precipitate the formed polymer. The resulting gel-like material
was filtrated and washed by hexane. Yield: 1.61 g (92.5%).
1H NMR for poly-(2-bromoethyl acrylate) (400 MHz, CDCl3)
d (ppm) 4.40 (br, 2H, O–CH2), 3.55 (br, 2H, Br–CH2), 2.45
(br, 1H), 2.03 (br, 1H), 1.75 (br, 1H).
3-Ferrocenyl-40-((2-(acryloyloxy)ethoxy)methyl)azobenzene.
3-Ferrocenyl-40-hydroxymethylazobenzene (1.057 g, 2.67 mmol)
was dissolved in 20 mL of dehydrated tetrahydrofuran
under an argon atmosphere. To this orange solution, sodium
tert-butoxide (0.294 mg, 2.62 mmol) was added and the
color of the solution immediately changed to dark brown.
2-Bromoethyl acrylate (0.873 g, 4.88 mmol) was added to the
solution, and the mixture was stirred for 22 h. Water (20 mL)
was added and the organic layer was collected and dried with
anhydrous sodium sulfate. After removing the solvent, orange
oil was purified by silica-gel column chromatography with
chloroform–hexane (3 : 1) as eluent and the second fraction
was collected. Yield: 0.537 g (1.08 mmol, 40.5%). 1H NMR for
3-ferrocenyl-40-((2-(acryloyloxy)ethoxy)methyl)azobenzene
(400 MHz, CDCl3) d (ppm) 8.02 (t, J = 1.8, 1H, C6H4), 7.95
(d, J = 8.4 Hz, 2H, C6H4), 7.73 (d, J = 7.8 Hz, 1H, C6H4),
7.60 (d, J = 7.8 Hz, 1H, C6H4), 7.54 (d, J = 8.4 Hz, 2H,
C6H4), 7.43 (dd, J = 7.8 Hz, 7.8 Hz, 1H, C6H4), 6.49 (dd, J =
17.2 Hz, 1.2 Hz, 1H, QCH), 6.21 (dd, J = 17.2 Hz, 10.4 Hz,
1H,QCH2), 5.89 (dd, J = 10.4 Hz, 1.2 Hz, 1H,QCH2), 5.29
(s, 2H, CH2), 4.75 (s, 2H, C5H4), 4.47 (t, J = 6.0, 2H, O–CH2),
Polymerization was also carried out in cyclohexane. 2-Bromo-
ethyl acrylate (1.22 g, 6.80 mmol) was dissolved in 7 mL of
cyclohexane, degassed by nitrogen for 15 min, azobisisobutyro-
nitrile (0.0127 g, 0.077 mmol) was added, and stirred for 18 h
at 60 1C. The solution became clouded as the polymerization
reaction proceeded. Yield of the polymer was quantitative.
Polymerization of 2-bromoethyl acrylate by emulsion
polymerization
Ultra pure water (20 mL) in a 50 mL round-bottom flask was
degassed by nitrogen for 15 min and sodium dodecyl sulfate
(2.004 g, 6.95 mmol) was dissolved. 2,20-Azobisisobutyro-
nitrile (0.023 g, 0.14 mmol) was dissolved in 2-bromoethyl
acrylate (0.812 g, 4.54 mmol) and the mixture was poured into
the round-bottom flask and stirred for 5 min to emulsify the
monomer. The resulting clear solution was heated to 60 1C
and the solution became creamy white. The solution was
heated for 20 h, and aqueous ammonium chloride was added
to salt out the formed polymer. The ball-like polymer was
washed with water and methanol vigorously. Yield: 0.732 g
(36.5 %).
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Modification of poly(2-bromoethyl acrylate) formed by solution
polymerization (Polymer A)
(s, 2H, C5H4), 4.41(br), 4.36 (s, 2H, C5H4), 4.07 (s, 5H, C5H5),
3.55(br), 2.46(br), 2.47(br) 1.77(br), 1.26(br).
Poly(2-bromoethyl acrylate) (0.261 g) was dissolved in 10 mL
of anhydrous tetrahydrofuran. To the solution, alkoxide
solution (sodium tert-butoxide (92 mg, 0.82 mmol) and
3-ferrocenyl-40-hydroxymethylazobenzene (0.309 g, 78.0 mmol,
0.53 eq. vs. poly(2-bromoethyl acrylate)) in 20 mL of
anhydrous tetrahydrofuran) was added dropwise for 10 min.
The resulting mixture was stirred for 3 h, and saturated
aqueous ammonium chloride (20 mL) was added. The organic
layer was extracted by dichloromethane and dried over anhydrous
sodium sulfate. The mixture was purified by silica gel column
chromatography with chloroform as eluent and the first fraction
was collected. Yield: 0.305 g. IR (cmꢀ1): 2922, 2851, 1696,
1603, 1506, 1451, 1414, 1385, 1205, 1156, 1105, 1034, 1012,
870, 825, 797, 712, 689, 504.
Acknowledgements
This work was supported by Grant-in-Aid for Scientific
Research from MEXT of Japan (Nos. 20245013 and
21108002, area 2107 (Coordination Programming)).
References
1 M. Irie, Chem. Rev., 2000, 100, 1683, and the reviews in the same
issue.
2 (a) S. Kume and H. Nishihara, Struct. Bonding, 2007, 123, 79;
(b) S. Kume and H. Nishihara, Dalton Trans., 2008, 3260, and the
references therein.
3 (a) Y. Yu, M. Nakano and T. Ikeda, Nature, 2003, 425, 145;
(b) A. S. Abd-El-Aziz, P. O. Shipman, B. N. Boden and
W. S. McNeil, Prog. Polym. Sci., 2010, 35, 714–836, and the
references therein.
4 D. Pearson, A. J. Downard, A. M. Taylor and A. D. Abell, J. Am.
Chem. Soc., 2007, 129, 14862.
Modification of poly(2-bromoethyl acrylate) formed by emulsion
polymerization (Polymer B)
Poly(2-bromoethyl acrylate) (49 mg) was dispersed in 10 mL
of anhydrous tetrahydrofuran, heated to 40 1C, and stirred for
30 min. To the solution, alkoxide solution (sodium tert-but-
oxide (67 mg, 0.60 mmol) and 3-ferrocenyl-40-hydroxymethyl-
azobenzene (196 mg, 0.495 mmol, 1.8 eq. vs. poly(2-bromoethyl
acrylate)) in 10 mL of anhydrous tetrahydrofuran) was added
dropwise for 10 min. The suspension was stirred at 45 1C for
2 h, cooled to room temperature and the insoluble component
was filtrated and washed with water and methanol. Yield: 25 mg.
IR (cmꢀ1): 2951, 2871, 1734, 1701, 1603, 1452, 1386, 1160, 820,
5 Y. Einaga, O. Sato, T. Iyoda, A. Fujishima and K. Hashimoto,
J. Am. Chem. Soc., 1999, 121, 3745.
6 (a) M. Kurihara, A. Hirooka, S. Kume, M. Sugimoto and
H. Nishihara, J. Am. Chem. Soc., 2002, 124, 8800;
(b) A. Sakamoto, A. Hirooka, K. Namiki, M. Kurihara,
M. Murata, M. Sugimoto and H. Nishihara, Inorg. Chem., 2005,
44, 7547; (c) M.-C. Daniel, A. Sakamoto, J. Ruiz, D. Astruc and
H. Nishihara, Chem. Lett., 2006, 38.
7 K. Namiki, A. Sakamoto, M. Murata, S. Kume and H. Nishihara,
Chem. Commun., 2007, 4650.
8 (a) C. S. Chern, Prog. Polym. Sci., 2006, 31, 443; (b) M. Save,
Y. Guillaneuf and R. G. Gilbert, Aust. J. Chem., 2006, 59, 693.
9 C. U. Pittman, J. Inorg. Organomet. Polym. Mater., 2005, 15, 33.
10 Y. Li, Y. Deng, X. Tong and X. Wang, Macromolecules, 2006,
39, 1108.
1
688, 497. H NMR: (400 MHz, CDCl3) d (ppm) 8.01 (s, 1H,
C6H4), 7.86 (d, J = 7.2 Hz, 2H, C6H4), 7.72 (d, J = 7.2 Hz,
1H, C6H4), 7.58 (d, J = 7.2 Hz, 1H, C6H4), 7.43 (dd, J = 7.2 Hz,
7.2 Hz, 1H, C6H4), 7.34 (d, J = 7.2 Hz, 2H, C6H4), 4.75
11 C. E. Rehberg, M. B. Dixon and W. A. Faucett, J. Am. Chem.
Soc., 1950, 72, 5199.
c
2152 New J. Chem., 2011, 35, 2146–2152
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