Functional 1,3-benzoxazine bearing 4-pyridyl group: Synthesis and thermally induced polymerization behavior

Article abstract of DOI:10.1002/pola.27015

1,3-benzoxazine 1, bearing 4-pyridyl moiety on the nitrogen atom, was synthesized from p-cresol, 4-aminopyridine, and paraformaldehyde. The efficient synthesis was achieved by adding acetic acid to suppress the strong basicity caused by the presence of 4-aminopyridine derivatives. Upon heating 1 at 180 °C, it underwent the thermally induced ring-opening polymerization. The resulting polymer was composed of two types of repeating unit, i.e., (1) Mannich-type one (-phenol-CH₂-NR-CH₂-) that can be expected from the general ring-opening polymerization of conventional benzoxazines and (2) a typical phenolic resin-type one (-phenol-CH ₂-phenol-) induced by release of 4-aminopyridine and paraformaldehyde (unit B). Another structural feature of the polymer was that it possessed a benzoxazine moiety at the chain end. 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 410-416 A novel 1,3-benzoxazine 1 with 4-aminopyridyl moiety is synthesized from 4-aminopyridine, p-cresol, and paraformaldehyde. 1 undergoes the thermally induced ring-opening polymerization at 180 °C to afford the corresponding polymer composed of two types of repeating units, that is, Mannich-type one (-phenol-CH₂-NR-CH ₂-) and a typical phenolic resin-type one (-phenol-CH ₂-phenol-). The polymer possesses a benzoxazine moiety at the chain end. Copyright

Full text of DOI:10.1002/pola.27015

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
Functional 1,3-Benzoxazine Bearing 4-Pyridyl Group: Synthesis
and Thermally Induced Polymerization Behavior
Asei William Kawaguchi,1 Atsushi Sudo,2 Takeshi Endo1
1Molecular Engineering Institute, Kinki University, Kayanomori, Iizuka, Fukuoka 820-8555, Japan
2Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, Kowakae, Higashi Osaka,
Osaka 577-8502, Japan
Correspondence to: T. Endo (E-mail tendo@moleng.fuk.kindai.ac.jp)
Received 18 May 2013; accepted 5 November 2013; published online 22 November 2013
DOI: 10.1002/pola.27015
ABSTRACT: 1,3-benzoxazine 1, bearing 4-pyridyl moiety on
the nitrogen atom, was synthesized from p-cresol, 4-
aminopyridine, and paraformaldehyde. The efficient synthesis
was achieved by adding acetic acid to suppress the strong
basicity caused by the presence of 4-aminopyridine derivatives.
Upon heating 1 at 180 ꢀC, it underwent the thermally induced
ring-opening polymerization. The resulting polymer was com-
posed of two types of repeating unit, i.e., (1) Mannich-type one
(-phenol-CH2-NR-CH2-) that can be expected from the general
ring-opening polymerization of conventional benzoxazines and
(2) a typical phenolic resin-type one (-phenol-CH2-phenol-)
induced by release of 4-aminopyridine and paraformaldehyde
(unit B). Another structural feature of the polymer was that it
C
V
possessed a benzoxazine moiety at the chain end. 2013 Wiley
Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52,
410–416
KEYWORDS: benzoxazine; heteroatom-containing polymer;
metal-polymer
structure
complexes;
ring-opening
polymerization;
the benzoxazine ring, and its thermally induced ring-opening
polymerization behavior. Although analogous benzoxazines
and naphthoxazines bearing pyridyl moieties have been
reported, their polymerization behaviors have been not
reported25–29. In addition, the ability of the resulting poly-
mer 2 to capture some metal ions such as Cu21and Co21 is
also described.
INTRODUCTION 1,3-benzoxazines have received considerable
attention because of their promising practical applications as
monomers for high performance materials.1–3 Their facile
and versatile synthesis from relatively abundant materials
involving phenols, amines, and formaldehyde is also greatly
advantageous from the viewpoint of development of various
benzoxazines bearing functional groups.4–22 Some of these
functional groups serve as reactive sites to increase the
crosslinking degree so that the thermal and mechanical
properties of the obtained poly(benzoxazine)s can fulfill spe-
cific requirements.
EXPERIMENTAL
Materials
The materials included 4-aminopyridine, purchased from
Tokyo Chemical Industry Co. Ltd. Paraformaldehyde and ace-
tic acid were purchased from Kanto Kagaku Co. p-Cresol, tol-
uene, cobalt(II) sulfate hepta-hydrate, and copper(II) sulfate
penta-hydrate were purchased from Wako Pure Chemical
Industries. All materials were used without any further puri-
fication. N-Phenyl-1,3-benzoxazine 3 was prepared from
according to the reported procedure.30–32
Another interesting topic in the field of the utilization of
functionalized 1,3-benzoxazine monomers is their combina-
tion with inorganic materials to fabricate nanocomposites. In
these works, the attractive interaction between polar func-
tional groups and inorganic surfaces has been effectively
exploited. For example, Yagci et al. have demonstrated the
surface functionalization of nanoparticles of magnetite with
a benzoxazine bearing carboxyl moiety.23 Recently, Yagci’s
group and we collaborated to develop a polybenzoxazine/
montmorillonite nanocomposite, where a new benzoxazine
bearing 4-pyridyl moiety 1 was used as a key material.24
Measurements
1H NMR spectra were recorded in either chloroform-d
(CDCl3) or dimethylsulfoxide (DMSO-d6) on a Varian UNITY-
INOVA400 (1H, 400 MHz) spectrometer, with tetramethyl-
silane (TMS) as an internal standard. Melting point was
measured by Yanako MP-500D. Number-average molecular
Herein, we report the details of the synthesis of benzoxazine
1, which possesses 4-pyridyl moiety on the nitrogen atom in
Additional Supporting Information may be found in the online version of this article.
C
V
2013 Wiley Periodicals, Inc.
410
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
weight (Mn) was estimated by size exclusion column chroma-
tography (SEC) on a Tosoh HLC-8220GPC system, equipped
with three consecutive polystyrene gelcolumns (AM4000,
AM3000 and AM2500, molecular weight ranges: 1,000,000–
500 Da) and refractive index (RI) and ultraviolet (UV,
k 5 254 nm) detectors, using DMF as a eluent and flow rate
was 1.0 mL/min. This system was calibrated with polysty-
rene standards.
Synthesis of 6-methyl-3-(pyridin-4-yl)-3,4-dihydro-2H-
1,3-benzoxazine (1)
In a 100-mL round-bottomed flask equipped with a Dean-
Stark apparatus, 4-aminopyridine (9.40 g, 100 mmol), p-cre-
sol (10.8 g, 100 mmol), acetic acid (6.00 g, 100 mmol), para-
formaldehyde (6.00 g, 200 mmol) and 2-methoxyethanol (10
mL) were added in toluene (50 mL) and the mixture was
heated under reflux for 14 h with addition of 3.00 g of para-
formaldehyde every 2 h. The reaction mixture was cooled to
room temperature and washed with 100 mL of 1.5 M NaOH
aq. and 100 mL of brine three times each. After the organic
phase was dried over anhydrous MgSO4, the solvent was
removed under reduced pressure, and the residue was frac-
tionated by the column chromatography (eluent: acetone) to
obtain crude 1. Crude 1 was further purified by recrystalli-
zation from a mixture of acetone and n-hexane (volume
ratio5 1:ꢀ4) to obtain pure 1 (14.7 g, 65 mmol, 65%): mp
136–137 C.
SCHEME 1 Synthesis of benzoxazine
1
bearing 4-pyridyl
moiety.
min. The corresponding metal-polymer complexes were
precipitated.
1
ꢀ
H NMR (400 MHz, CDCl3, 20 C) d, ppm; 2.26 (s, 3H, CH3-),
4.60 (s, 2H, Ph-CH2-N), 5.33(s, N-CH2-O), 6.73-6.95 (5H,
3,5,6-position H of Ph and 3,5-position H of pyridine), 8.33
(dd, 2H, 2,6-position H of pyridine). 13C NMR (in CDCl3, at
20 ꢀC): 20.8 (C H3-), 48.3 (Ph-C H2-N), 76.3 (N-C H2-O),
110.2, 117.2, 120.0, 127.3, 129.1, 131.0, 150.9, 152.1, and
153.4 (aromatic part). Anal. calcd. for C14H14N2O: C, 74.31;
H, 6.24; N, 12.38. Found: C, 74.04; H, 6.12; N, 12.35.
RESULT AND DISCUSSION
Synthesis of Benzoxazine Bearing 4-Pyridyl Group
With employing p-cresol, 4-aminopyridine, and paraformal-
dehyde as the starting materials, we surveyed reaction con-
ditions for efficient synthesis of benzoxazine 1 (Scheme 1).
1
Its yields were estimated by H-NMR analysis of the reaction
mixtures, and the resulting time-yield relationships are
shown in Figure 1. The conditions and the corresponding
results are summarized in Table 1.
Thermally Induced Ring-Opening Polymerization of 1
Five hundred milligrams each of 1 were taken and each of
them was placed in a test tube. Nitrogen inlets were
attached to the ꢀtest tubes and then they were heated in an
oil bath at 180 C. From time to time, these test tubes were
taken away from the oil bath one-by-one, and each of the
mixture was analyzed by 1H NMR to determine conversions
of 1 and the unit ratio. The product obtained by heating the
monomer for 14 h was dissolved in DMF, and the solution
was poured into ethyl acetate. The resulting precipitate was
collected by filtration and was dried in vacuo to give corre-
sponding polymer 2a (180 mg, 36%). In a similar way, the
product obtained by heating the monomer for 36 h was
treated to obtain polymer 2b (135 mg, 27%).
First, we attempted to synthesize 1 by a standard method,
i.e., heating a mixture of p-cresol, in refluxing toluene (entry
1). The reaction became sluggish, giving a yellow viscous
substance insoluble in toluene. Since it was highly polar
according to TLC analysis, we speculated that the viscous
product was a resol-type condensate 4, of which formation
was promoted by highly basic 4-aminopyridine and its deriv-
atives. As shown in Figure 1, the NMR yield of 1 reached ca.
25% at 27 h. Prolonging the reaction time was not effective
to improve the yield. In addition, a benzoxazine bearing
hydroxymethyl group 5 was isolated from the reaction mix-
ture in 12% as a byproduct. H and 13C NMR of 5 are shown
1
in Figure S1 in Supporting Information. Some plausible
mechanisms for the formation of 5 that involve base-
catalyzed hydroxymethylation of p-cresol and that of the p-
cresol-derived benzoxazine 1 are shown in Scheme 2.
Metal ion-Capturing
Two hundred seventy milligrams of 2a was dissolved in
DMF (60 mL) to obtain Solution A. CuSO4Á5H2O (50.0 mg,
0.2 mmol) and CoSO4Á7H2O (56.2 mg, 0.2 mmol) were dis-
solved into a mixture of deionized water (5 mL) and metha-
nol (15 mL) to obtain Solution B, respectively. Solution A (1
mL) was poured into solution B (1 mL) and stirred for 1
To suppress these base-catalyzed side reactions, we next
attempted addition of acetic acid (entry 2). As shown in Fig-
ure 1, the formation of 1 was slightly accelerated. More
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416
411

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
SCHEME 2 Plausible mechanisms for the formation of
byproducts.
ence of acetic acid, the pyridylamino part would be
neutralized and thus converted to a more polar and less
soluble salt form, preventing the reaction of 6 with formal-
dehyde to give 1.
FIGURE 1 Time-dependences of 1H NMR yield of 1.
For the purpose of preventing the precipitation of the inter-
mediate 6, 2-methoxyethanol was added as a co-solvent
(entry 4). This alcohol was employed because it is enough
polar and is less volatile not to be removed from the system
during the azeotropic removal of water was added. However,
as shown in Figure 1, the rate of formation of 1 was deceler-
ated contrary to our expectation. What we observed in this
case was serious sublimation of paraformaldehyde on the
condenser. This problem was solved by adding paraformalde-
hyde in several portions every 2 h (entry 5). Further
improvement of the yield of 1 was achieved in entry 6,
where the initial concentrations of p-cresol and 4-
aminopyridine were 10 times larger than those in entry 5.
By recrystallization, 1 was isolated as a colorless crystal in
65%.
remarkably, the formation of the yellow viscous substance
was completely suppressed. In addition, the byproduct 5
was not detected in the 1H-NMR analysis of the mixture
(Fig. 2).
Upon confirming the remarkable addition effects of acetic
acid, we continued further optimization of the conditions. In
entry 3, a Dean-Stark apparatus was used for azeotropic
removal of water formed during the reaction. As a result, the
formation of 1 was significantly accelerated so that its yield
reached 50% within 10 h. However, the final yield of 1 after
the reaction for 18 h was not satisfactory yet. In this case, a
white viscous precipitate formed. TLC analysis of the precipi-
tate revealed that it was a mixture of highly polar com-
pounds. 1H-NMR analysis of the precipitate suggested that
the major component of the mixture was an aminomethy-
lated cresol derivative 6 formed by condensation of p-cresol,
formaldehyde, and 4-aminopyridine, of which further cyclo-
condensation with formaldehyde gives 1. Due to the pres-
Besides, we examined another route for the target benzoxa-
zine 1, which relied on the transformation of 4-
aminopyridine into the corresponding triazine derivative and
its use. Recently this “triazine-route” has been successfully
TABLE 1 Synthesis of N-(4-Pyridyl) 1,3-Benzoxazinea
p-Cre-
sol
4-Amino
pyridine
(mmol)
Paraformal-
dehyde
Toluene AcOH
Dean-Stark
apparatus
2-Methoxy
Reaction
Yieldb
(%)
Entry (mmol)
(mmol)
(mL)
(mmol)
ethanol (mL) time (h)
1
2
3
4
5
6
10
10
10
10
10
100
10
10
10
10
10
100
20
50
50
50
50
50
50
0
Not used
Not used
Used
0
48
48
18
24
14
12
31 (8c)
42 (30c)
53
20
10
10
10
10
100
0
20
0
20
Used
5
50
140
700
Used
5
66 (52c)
73 (65c)
Used
10
a
c
Temp.: reflux.
Yield estimated by 1H NMR.
Isolated yield.
b
412
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
FIGURE 2 1H NMR spectra of the reaction mixtures (Entries 1
and 2).
applied to the efficient synthesis of benzoxazines.33 Accord-
ingly, we attempted to synthesize the triazine with varying
reaction conditions such as solvent, temperature, and con-
centration; however, under all the conditions we surveyed,
the triazine was not obtained. Instead, the product we
got was (4-Py)-NH-CH2-NH-(4-Py), the 2:1 adduct of 4-
aminopyridine and formaldehyde. This adduct was insoluble
in all the solvents we examined and this insoluble nature
prevented its further reactions.
FIGURE 3 1H and 13C NMR spectra of 1.
13C NMR spectrum also supported the chemical structure of
1. The two signals at 76.3 and 48.3 ppm were attributable
for the two methylene groups in the benzoxazine ring.
Benzoxazine 1 was soluble in acetone, ethyl acetate, chloro-
form, toluene, DMSO and DMF, and was insoluble in n-hex-
ane. Figure 3 shows the 1H and 13C NMR spectra of 1. All
the signals, which involve two singlet ones at 4.6 and 5.3
ppm for the two methylene groups in the benzoxazine ring,
were successfully assigned. The singlet signal at 8.33 ppm
was also assigned for 2,6-position protons of pyridine. The
Thermally Induced Polymerization of 1
The thermally induced polymerization of 1 was examined at
180 ꢀC (Scheme 3). As a referential experiment, the ther-
mally induced polymerization of N-phenyl-1,3-benzoxazine 3
was also performed under the same conditions. The corre-
sponding time-dependences of monomer conversion are
SCHEME 3 Thermally induced polymerization of 1.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416
413

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
same precipitation procedure. Figure 5 shows the 1H NMR
spectrum of 2a, which clarified the following structural char-
acteristics of 2a: (a) The smaller content of pyridyl group
than that expected from the standard ring-opening polymer-
ization of benzoxazines without side reactions and (b) the
presence of benzoxazine ring at the chain end. The unexpect-
edly smaller content of pyridyl group was clarified by com-
paring the integrated intensity of the signals attributable to
the pyridyl group at around 8 ppm with that of a broad sig-
nal attributable to the methyl group at around 2 ppm. On
the other hand, the presence of benzoxazine ring at the chain
end was suggested by the presence of two signals at 4.6 and
5.3 ppm, which were attributable to the two methylene
groups in the benzoxazine ring. These signals were not
observed in the spectrum of polymꢀer 2b, which was
obtained by heating polymer 2a at 180 C for 22 h, suggest-
ing that the benzoxazine ring at the terminal of 2a was con-
sumed by its thermally induced ring-opening reaction. The
content of the pyridyl group did not change during this post
heating process.
FIGURE 4 Time-dependence of conversion of 1 and that of
conversion of 3 in their thermally induced polymerizations at
180 ꢀC.
Along with the small content of pyridyl moiety in 2, a corre-
spondingly small content of the methylene linkages was also
suggested by the NMR spectrum. If the polymer 2b is solely
composed of unit A, -cresol-CH2-N(4-pyridyl)-CH2-cresol-
that can be formed by the standard ring-opening polymeriza-
tion of benzoxazines, the ratio between the intensity of the
signal attributable to the methylene linkages and that of the
signal attributable to the methyl groups should be 4:3. How-
ever, the ratio estimated by analyzing the spectrum was
1.8:3. From the synchronous lacks of the pyridyl and methyl-
ene moieties, we deduced that the polymer contained unit B,
a cresol-novolac-type unit.
shown in Figure 4. The consumption rate of 1 was much
smaller than that of 3, suggesting that the electron-
withdrawing nature of the 4-pyridyl group affected the poly-
merization ability of benzoxazine negatively. Such retardation
of polymerization by introducing electron-deficient aromatic
groups such as 4-chlorophenyl and 4-nitrophenyl groups has
been reported.34
By heating 1 at 180 ꢀC for 14 h, more than 90% of 1 was
consumed. The resulting polymer 2a was isolated by precipi-
tation from ethyl acetate and then purified by repeating the
For more detailed structural analysis of the polymers 2, their
13C NMR spectra were measured. The resulting spectra are
FIGURE 5 1H NMR spectra of 1, 2a, and 2b.
414
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
FIGURE 6 13C NMR Spectra of 1, 2a, and 2b.
shown in Figure 6. The spectrum of 2a confirmed the pres-
ence of benzoxazine moiety at the chain end. On the other
hand, the spectrum of 2b confirmed its disappearance. These
results were in good agreement with the information
1
obtained from the H NMR analysis.
The polymers 2a and 2b were isolated as ethyl acetate-
insoluble fractions in 36 and 27%, respectively. They were
soluble in DMF and DMSO, and insoluble in acetone, ethyl
acetate, THF and n-hexane.
In addition, the polymerization of 1 was performed at 200 ꢀC.
The corresponding time-dependence of the monomer conver-
sion is shown in Figure 4. At this elevated temperature, the
consumption rate of 1 was much faster than that observed at
180 ꢀC. Within 4 h, more than 90 % of 1 was consumed.
1H-NMR analysis of the resulting polymer clarified that its
structure was quite similar to that of polymer 2b.
SCHEME 4 Plausible mechanisms for the polymerization of 1.
mer 1, phenoxide-containing species such as A1, and pheno-
lic moieties at the chain ends. The adduct of A1 and 1 has a
benzoxazine moiety, which can remain intact at the chain
end or can undergo the ring-opening reaction into a zwitter-
ionic species A2.
Possible Mechanisms for the Polymerization of 1
Scheme 4 depicts some plausible mechanisms that would be
involved in the present polymerization system. Although
there should be other pathways, only essential ones that can
explain the structural characteristics of the polymer 2 are
selected to simplify the discussion. As has been already
described, 1 was less reactive than a cresol-derived N-phenyl
benzoxazine 3. In the polymerization of benzoxazines, their
ring-opening reaction into the corresponding zwitter-ionic
intermediates is one of the critical steps. In the case of the
polymerization of 1, this step can be inhibited by introduc-
tion of electron-withdrawing 4-pyridyl group on the nitrogen
atom, because it destabilizes the iminium cation in the spe-
cies A1 that should be formed as a result of the ring-
opening reaction.
Another possible pathway from the zwitter-ionic species
such as A1 and A2 would be the elimination of imine 7 to
give the corresponding methyl cations B1 and B2. Previously
we have reported that this elimination process was responsi-
ble for the weigh losses during the polymerization of benzox-
azines.35 The resulting methyl cations can react with the
electron-sufficient cresol-derived aromatic ring, leading to
the incorporation of cresol-novolac-type unit in the resultant
polymers.
Estimation of Molecular Weight of Polymer 8
The polymers 2a and 2b were analyzed by SEC to estimate
their molecular weights. The resulting SEC profiles were
bimodal in both the cases. From the two peaks in the profile,
Mns of 2a were estimated to be 7800 and 2600. In a similar
way, Mns of 2b were estimated to be 8200 and 2500, which
were almost same as those of 2a.
Once the iminium moiety forms, it can react with the
electron-sufficient cresol-derived aromatic ring in the mono-
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416
415

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
7 H. Oie, A. Sudo, T. Endo, J. Polym. Sci. Part A: Polym. Chem.
2010, 48, 5357–5363.
On the other hand, the SEC profile of polymer 8 obtained by
masking the phenolic OH of polymer 2b by its reaction with
t-butyl isocyanate was unimodal, and its SEC-estimated Mn
was 1600, much smaller than those of 2b. This significant
difference in Mn caused by masking OH implied that (1) the
intrinsic molecular weight of 2b was much smaller than that
estimated by SEC and (2) the strong interaction between the
phenolic moiety and pyridyl moiety caused aggregation of
the polymer chains, leading to the overestimation of molecu-
lar weight.
8 M. Ergin, B. Kiskan, B. Gacal, Y. Yagci, Macromolecules 2007,
40, 4724–4727.
9 A. Nagai, Y. Kamei, X. S. Wang, M. Omura, A. Sudo, H.
Nishida, E. Kawamoto, T. Endo, J. Polym. Sci. Part A: Polym.
Chem. 2008, 46, 2316–2325.
10 B. Kiskan, G. Demiray, Y. Yagci, J. Polym. Sci. Part A:
Polym. Chem. 2008, 46, 3512–3518.
11 A. Chernykh, T. Agag, H. Ishida, Polymer 2009, 50, 3153–
3157.
12 Z. Brunovska, H. Ishida, J. Appl. Polym. Sci. 1999, 73, 2937–
2949.
Metal Ion Capturing by Polymer 2
One of the outstanding features of the polymer 2 is the pres-
ence of a highly basic 4-aminopyridyl moiety in the side
chain. Therefore, we expected that the side chain would have
high affinity to metal ions to permit the polymer to capture
metal ions efficiently. A DMF solution of 2b was prepared,
and to this solution, a solution of CuSO4Á5H2O in a mixture
of water and methanol was added. As a result, a light yellow
precipitation appeared in a few minutes (Fig. S2 in Support-
ing Information), confirming the formation of a complex of
polymer 2b and cupper (II) ion. Similarly, cobalt (II) ion was
efficiently captured, leading to the formation of a pink insol-
uble polymer-metal complex.
13 H. M. Qi, H. Ren, G. Y. Pan, Y. Q. Zhuang, F. R. Huang, L.
Du, Polym. Adv. Technol. 2009, 20, 268–272.
14 Y. L. Liu, C. I. Chou, J. Polym. Sci. Part A: Polym. Chem.
2005, 43, 5267–5282.
15 R. Andreu, M. A. Espinosa, M. Galia, V. Cadiz, J. C. Ronda,
J. A. Reina, J. Polym. Sci. Part A: Polym. Chem. 2006, 44,
1529–1540.
16 D. R. Yei, H. K. Fu, W. Y. Chen, F. C. Chang, J. Polym. Sci.
Part B: Polym. Phys. 2006, 44, 347–358.
17 R. Kudoh, A. Sudo, T. Endo, Macromolecules 2010, 43,
1185–1187.
18 B. Kiskan, B. Koz, Y. Yagci, J. Polym. Sci. Part A: Polym.
Chem. 2009, 47, 6955–6961.
19 K. Jia, R. Zhao, J. C. Zhong, X. B. Liu, J. Mater. Sci. 2010,
21, 1125–1131.
CONCLUSIONS
A novel 1,3-benzoxazine, 1, bearing 4-aminopyridyl moiety
was synthesized from 4-aminopyridine, p-cresol, and parafor-
maldehyde, where addition of acetic acid to neutralize the
basicity of the system was inevitable. The benzoxazine 1
underwent thermally induced ring-opening polymerization
upon heating it at 180 ꢀC. The polymerization was slower
than that of an analogous N-phenyl benzoxazine derived
from p-cresol, clarifying the significant deceleration effect by
the electron-withdrawing nature of pyridyl moiety. The
obtained polymer possessed pyridyl group at the side chain,
although its content was lower than that expected from the
standard ring-opening polymerization of benzoxazines. The
4-aminopyridyl moiety introduced into the polymer exhibited
high affinity to metal ions such as copper (II) and cobalt (II)
ions, leading to the formation of the corresponding polymer-
metal complexes. Due to this metal-capturing ability, the
polymer would be useful as metal scavenging materials and
a component for polymer-inorganic hybrid materials.
ꢀ~
ꢁ
20 C. Zuniga, M. S. Larrechi, G. Lligadas, J. C. Ronda, M. Galia,
ꢀ
V. Cadiz, J. Polym. Sci. Part A: Polym. Chem. 2011, 49, 1219–
1227.
21 S. F. Li, T. Zou, J. Appl. Polym. Sci. 2012, 123, 922–928.
22 Y. H. Liu, W. Zhang, Y. Chen, S. X. Zheng, J. Appl. Polym.
Sci. 2006, 99, 927–936.
23 Y. Yagci, B. Kiskan, A. L. Demirel, O. Kamer, J. Polym. Sci.
Part A: Polym. Chem. 2008, 46, 6780–6788.
24 K. D. Demir, M. A. Tasdelen, T. Uyar, A. W. Kawaguchi, A.
Sudo, T. Endo, Y. Yagci, J. Polym. Sci. Part A: Polym. Chem.
2011, 49, 4213–4220.
25 E. Laxminarayana, T. Krantikumar, M. T. Chary, Int. J.
Chem. Sci. 2010, 8, 2367–2372.
26 H. Y. Sun, T. Y. Kim, S. W. Cho (Samsung SDI Co., Ltd.).
Eur. Patent EP,188,154,9A1, January 23, 2008.
27 S. Choi, J. Park, W. Lee (Samsung Electronics Co., Ltd.).
Eur. Patent EP,203,691,0A1, March 18, 2009.
28 S. Choi, W. Jeon, I. Jung, W. Lee (Samsung Electronics Co.,
Ltd.). Eur. Patent EP,204,818,3A1, April 15, 2009.
29 S. Choi, J. Park (Samsung Electronics Co., Ltd.). U.S. Patent,
US2,009,011,744,0A1, May 7, 2009.
30 X. Ning, H. S. Ishida, J. Polym. Sci. Part B: Polym. Phys.
1994, 32, 921–927.
REFERENCES AND NOTES
1 H. Ishida, D. P. Sanders, J. Polym. Sci. Part B: Polym. Phys.
2000, 38, 3289–3301.
31 H. Kimura, A. Matsumoto, K. Hasegawa, K. Ohtsuka, A.
Fukuda, J. Appl. Polym. Sci. 1998, 68, 1903–1910.
2 H. Ishida, D. J. Allen, J. Polym. Sci. Part B: Polym. Phys.
1996, 34, 1019–1030.
32 A. Sudo, R. Kudoh, H. Nakayama, K. Arima, T. Endo, Macro-
molecules 2008, 41, 9030–9034.
3 X. Ning, H. Ishida, J. Polym. Sci. Part A: Polym. Chem. 1994,
32, 1121–1129.
33 A. W. Kawaguchi, A. Sudo, T. Endo, J. Polym. Sci. Part A:
Polym. Chem. 2012, 50, 1457–1461.
4 W. J. Burke, J. Am. Chem. Soc. 1949, 71, 609–612.
34 R. Andreu,I. A. Reina, J. C. Ronda, J. Polym. Sci. Part A:
Polym. Chem. 2008, 46, 3353–3366.
5 N. N. Ghosh, B. Kiskan, Y. Yagci, Prog. Polym. Sci. 2007, 32,
1344–1391.
35 A. Sudo, L. C. Du, S. Hirayama, T. Endo, J. Polym. Sci. Part
A: Polym. Chem. 2010, 48, 2777–2782.
6 T. Agag, T. Takeichi, Macromolecules 2003, 36, 6010–6017.
416
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2014, 52, 410–416