Synthesis and in situ core reorganization of smart polymers

Article abstract of DOI:10.1016/j.reactfunctpolym.2011.04.009

A smart poly(ethylene oxide) polymer containing two thermally reversible groups located at the chain center (F2-PEO) was synthesized by a maleimide-furan (MF) [4 + 2] Diels-Alder (DA) reaction between one bis[(furan-2-yl)methyl] terephthalate (F2) and two

Full text of DOI:10.1016/j.reactfunctpolym.2011.04.009

Reactive & Functional Polymers 71 (2011) 843–848
Contents lists available at ScienceDirect
Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Synthesis and in situ core reorganization of smart polymers
⇑
Xiubo Jiang, Wen Zhu, Yechao Yan, Yongming Chen , Fu Xi
Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A smart poly(ethylene oxide) polymer containing two thermally reversible groups located at the chain
center (F2-PEO) was synthesized by a maleimide–furan (MF) [4 + 2] Diels–Alder (DA) reaction between
one bis[(furan-2-yl)methyl] terephthalate (F2) and two maleimide-terminated poly(ethylene glycol)
methyl ethers (MI-PEOs). MF adducts underwent retro-DA (rDA) addition at a higher temperature, and
the maleimide–anthracene (MA) addition reaction could occur simultaneously. Therefore, when F2-
PEO and bis((anthracen-10-yl)methyl) succinate (AN2) were refluxed in toluene for 48 h, the cores of
F2-PEOs were replaced with the MA adducts in situ to give new polymers AN2-PEOs. Moreover, when
F2-PEOs were mixed with the molecules containing four anthracene units (AN4), the rDA reaction of
the MF adducts and the MA addition reactions occurred simultaneously, generating four-arm star PEOs.
The core reorganization of polymers has been confirmed by SEC, UV, 1H NMR, and MALDI-TOF mass
spectra.
Received 4 March 2011
Received in revised form 25 April 2011
Accepted 28 April 2011
Available online 6 May 2011
Keywords:
Diels–Alder (DA) addition
Star polymers
Core reorganization
Smart polymers
Thermal reversible groups
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
hydrogel synthesis [23–25], modification of linear and dendronized
polymers [26–28], the development of reversible cross-linking sys-
In recent years, polymer chains that can be reconstructed by
responding to environmental influences have attracted significantly
increased attention. Such polymers have covalent linkages that may
be cleaved and reformed in response to external stimuli. This prop-
erty has been applied to the discovery of biologically active materi-
als [1,2] and to the development new stimulus-responsive
functional materials [3]. Chemical groups such as disulfide linkages
[4,5], acylhydrazone bonds [6–8], 2,2,6,6-tetramethylpiperidine-1-
oxy (TEMPO) groups [9–12], and [4 + 2] addition bonds from malei-
mide–furan Diels–Alder (DA) reaction [13–16] can be used as chem-
ical linkages for such polymers.
tems [29–33], and the development of organic–inorganic hybrids
[34,35]. One interesting feature of the DA reaction is that the adducts
may undergo a reverse reaction at higher temperature. The malei-
mide-furan (MF) DA reaction has been thoroughly studied. The MF
DA reaction occurs at a mild temperature of approximately 40 °C
and undergoes the retro-DA (rDA) reaction at a higher temperature.
However, the addition product between maleimide and anthracene
(MA) is much more stable, and the reverse reaction does not occur
even at a higher temperature [36]. The difference in the stability of
the two adducts above can endow the polymers that are based on
MF addition with interesting properties.
The polymers with disulfide –S–S– bonds can be cleaved into
smaller segments with terminal thiol groups in the presence of
reductants such as tri-n-butylphosphine or dithiothreitol (2,3-
dihydroxy-1,4-butanethiol), and the disulfide linkages can be
reformed under oxidation [17,18]. After a cycle of cleavage and
regeneration, the polymer chains can be recovered. Additionally,
radical exchange reactions of disulfides in the absence of oxygen
can proceed in high efficiency under photoirradiation conditions
[4]. The DA reaction is a well-known thermally reversible reaction,
which generally involves the coupling of a ‘‘diene’’ and a ‘‘dieno-
phile’’. Because it can proceed under mild conditions without a cat-
alyst, this reaction is attractive for designing reversible covalent
bonds and has been widely used in polymer synthesis [19–22],
Herein, we report novel polymers with replaceable cores based
upon the different properties of the MF and MA adducts. As shown
in Scheme 1, linear poly(ethylene oxide) with a core of MF adducts
(F2-PEO) was obtained by a coupling reaction of the maleimide
modified PEO (MI-PEO) and a bis-furan derivative (F2) (2:1 M ra-
tio). When the mixture of F2-PEO and a dianthracene functional
agent (AN2) in toluene was heated to reflux, the F2-PEO cleaved
via a rDA reaction yielding two MI-PEO intermediates, which re-
acted with AN2 in situ to form another linear PEO (AN2-PEO) with
a core of MA adducts. Moreover, when treating F2-PEO with tetra-
anthracene derivatives (AN4) at a ratio of F2-PEO:AN4 = 2:1, a star-
shaped PEO with four arms could be obtained by in situ core reor-
ganization. Therefore, this work supplied a new method not only to
introduce new components into the polymer chains but also to
reorganize the polymer chain architecture through an in situ pro-
cess of chain cleavage and regeneration.
⇑
Corresponding author. Tel.: +86 10 62659906; fax: +86 10 62559373.
E-mail address: ymchen@iccas.ac.cn (Y. Chen).
1381-5148/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.reactfunctpolym.2011.04.009

844
X. Jiang et al. / Reactive & Functional Polymers 71 (2011) 843–848
30 mL of mixture of CH2Cl2/DMF (v/v = 1/1). Then EDC (2.34 g,
15 mmol) was added upon stirring. After 12 h, 150 mL of CH2Cl2
was added in the solution. The solution was washed with water
three times, the CH2Cl2 phase was dried over MgSO4, and then
the solvent was evaporated to give a viscous liquid. The product
was purified by column chromatography (silica gel, petroleum
ether/ethyl acetate 6:1). The solid was dried at 25 °C under vacuum
to give 1.07 g of product (55% yield). 1H NMR (CDCl3, dH ppm) 8.09
(s, 4H), 7.45 (s, 2H), 6.50–6.48 (d, 2H), 6.39 (s, 2H). 5.32 (s, 4H). 13
C
NMR (CDCl3, dC ppm) 165.4, 149.2, 143.4, 133.8, 129.7, 111.1,
110.6, 58.8. Elemental analysis: Calcd for C18H14O6: C, 66.26; H,
4.29. Found: C, 65.80; H, 4.48.
2.4. Synthesis of the F2-PEO
MI-PEO (0.80 g, 1.03 mmol) and F2 (0.168 g, 0.50 mmol) were
dissolved in CHCl3 (3 mL). The resulting mixture was stirred at
40 °C for 72 h and then the solvent was removed by evaporation
under vacuum. The residue was purified by column chromatogra-
phy (silica gel, dichloromethane/methanol 10:1). Removal of the
solvents under reduced pressure gave F2-PEO crude product, and
the purified product was obtained by fractionation. 1H NMR
(CDCl3, dH ppm) 8.14–8.07 (m, 4Ha), 6.59–6.40 (m, 4Hc, endo/exo),
5.62–5.35 (dd, 2Hf, endo/exo), 5.22–4.68 (dd, dd, 4He, endo/exo),
3.8–4.8 (m, PEO and 1Hb, endo), 3.37 (s, 6Hc), 3.10–3.03 (dd, 1Hb,
exo), 2.65–2.55 (m, 8H).
Scheme 1. Formation of smart polymers and the process of core replacement.
2. Experimental
2.1. Materials
9-(Hydroxymethyl)anthracene (97%, Aldrich), 4-(dimethyl-
amino)pyridine (DMAP; 99%, Alfa Aesar), N-(3-dimethylaminopro-
2.5. Synthesis of the bis((anthracen-10-yl)methyl) succinate (AN2)
pyl)-N0-ethylcarbodiimide
hydrochloride
(EDC;
Aldrich),
Succinic acid (1.18 g, 10 mmol), 9-(hydroxymethyl)anthracene
(6.24 g, 30 mmol), and DMAP (0.61 g, 5 mmol) were dissolved in
a 60 mL mixture of CH2Cl2/DMF (v/v = 1/1). Then EDC (4.68 g,
30 mmol) was added upon stirring. After 12 h, 250 mL of CH2Cl2
was added into the solution, which was then washed with water
three times. The CH2Cl2 phase was dried over MgSO4, and then
the solvent was evaporated to give a viscous liquid. After precipi-
tation in methanol, the crude product was purified by recrystalliza-
tion in ethyl acetate to yield a yellow solid (3.73 g, 75%). 1H NMR
(CDCl3, dH ppm) 8.50 (s, 2H), 8.27–8.23 (d, 4H), 8.04–8.01 (d, 4H),
7.56–7.25 (m, 8H), 6.09 (s, 4H), 2.65 (s, 4H). 13C NMR (CDCl3, dC
ppm) 172.4, 131.4, 131.0, 129.2, 129.0, 126.6, 126.0, 125.1, 123.9,
59.1, 29.2. Elemental analysis: Calcd for C34H26O4: C, 81.93; H,
5.23. Found: C, 81.40; H, 5.29.
terephthalic acid (P99%, Aldrich), pentaerythritol (P97%, Aldrich),
succinic acid (P99%, Aldrich), and furfuryl alcohol (98%, Alfa Aesar)
were used as received. Other reagents were commercialized chem-
icals and used as received. Poly(ethylene oxide) with a terminated
carboxylic acid group (PEO-COOH) was prepared by condensation
between poly(ethylene glycol) monomethyl ether (molar mass is
550) and succinic acid anhydride in toluene [37]. 4-(2-Hydroxy-
ethyl)-10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione (F-MI)
was prepared according to literature [38]. Succinic acid mono-
athracen-9-ylmethyl ester was synthesized upon reaction with 9-
anthrylmethanol and succinic anhydride [39].
2.2. Measurements
1H NMR spectra were recorded with a Bruker 400 MHz spec-
trometer with CDCl3 as the solvent and tetramethylsilane as the
internal standard. The average molecular weights and polydisper-
sity indices of all the samples were measured with a size exclusion
chromatography (SEC) system equipped with a Waters 515 HPLC
pump, three Waters Styragel columns (HT2, HT3, and HT4), a Rhe-
odyne 7725i sampler, and a Waters 2414 refractive-index (RI)
detector. Low-dispersity PS standards were used to calibrate the
GPC system. THF was used as the eluent at a flow rate of 1 mL/
min at 35 °C. Matrix-assisted laser desorption/ionization time-of-
flight (MALDI-TOF) mass spectrometry was performed on a Bruker
Biflex III spectrometer equipped with a 337 nm nitrogen laser. The
2.6. Synthesis of the AN4
Pentaerythritol (0.136 g, 1 mmol), succinic acid mono-athracen-
9-ylmethyl ester (1.54 g, 5 mmol), and DMAP (0.24 g, 2 mmol)
were dissolved in 14 mL of a mixture of CH2Cl2/DMF (v/v = 1/1).
Then EDC (1.56 g, 10 mmol) was added upon stirring. After 12 h,
100 mL of CH2Cl2 was added into the solution, which was washed
with water three times. The combined CH2Cl2 phase was dried over
MgSO4, and then the solvent was evaporated to give a viscous li-
quid. After precipitation in methanol, the crude product was puri-
fied by column chromatography (silica gel, petroleum ether/
dichloromethane 1:2). 1H NMR (CDCl3, dH ppm) 8.44 (s, 4H),
8.33–8.30 (d, 8H), 8.27–8.24 (d, 8H), 7.53–7.40 (m, 16H), 6.09 (s,
8H), 4.06 (s, 8H), 2.60 (s, 16H). 13C NMR (CDCl3, dC ppm) 172.3,
171.6, 131.3, 130.0, 129.2, 129.0, 126.6, 126.0, 125.1, 123.9, 62.3,
matrix, 4-hydroxy-a-cyanocinnamic acid (CCA), and sample were
dissolved in THF. Mass spectra were acquired in reflection mode
and linear mode using an acceleration voltage of 19 kV. UV–vis
spectra were obtained on
spectrometer.
a Shimadzu model UV-1601PC
59.1, 42.0, 29.0. Elemental analysis: Calcd for
74.94; H, 5.24. Found: C, 73.71; H, 5.34.
C81H68O16: C,
2.3. Synthesis of bis(furan-2-yl)methyl terephthalate (F2)
2.7. Replacing core reaction to form an AN2-PEO
Terephthalic acid (1.00 g, 6.02 mmol), furfuryl alcohol (1.41 g,
14.4 mmol), and DMAP (0.73 g, 6.02 mmol) were dissolved in a
The AN2 (44 mg, 0.088 mmol) was added to a solution of F2-
PEO (0.17 g, 0.088 mmol) in 5.0 g of toluene. The mixture was bub-

X. Jiang et al. / Reactive & Functional Polymers 71 (2011) 843–848
845
tated with diethyl ether. The final product was dried for 24 h under
vacuum at 25 °C. Yield: 0.15 g (81%). 1H NMR (CDCl3, dH ppm)
7.50–7.05 (m, Hc, phenyl), 5.50 (s, 4Hb), 4.77 (s, 2Ha), 4.25–4.16
(m, 8Hd,h), 3.8–3.48 (m, PEO), 3.37 (s, 6Hf), 3.0–2.8 (s, 4He), 2.64–
2.50 (m, 12Hl,m,n).
2.8. Replacing core reaction to form star polymers AN4-PEO
The same procedure as above was performed. 1H NMR (CDCl3,
dH ppm) 7.50–7.05 (m, Hc, phenyl), 5.49 (s, 8Ha), 4.77 (s, 4Hb),
4.25–4.16 (m, 24H), 3.8–3.48 (m, PEO), 3.35 (s, 12Hj), 2.85–2.50
(m, 32Hf,g,h,i).
2.9. Monitoring efficiency of core replacement with UV spectrum
Scheme 2. Synthesis of F2-PEO with a replaceable core.
Fifty milligrams of solution was taken from the initial toluene
solution of F2-PEO and either AN2 or F2-PEO and AN4 and was
diluted to 8.0 g with toluene to be measured by UV–Vis spectros-
copy. After reaction for 48 h, the same amount of the solution
(50 mg) was taken from the Schlenk flask and was diluted to
bled with nitrogen for 30 min and refluxed in the dark for 48 h un-
der nitrogen. The solvent was removed under high vacuum; the
residual solid was dissolved in CH2Cl2 and subsequently precipi-
Fig. 1. 1H NMR spectra of F-MI-PEO (top) and MI-PEO (bottom).
Fig. 3. 1H NMR spectrum of fractionated F2-PEO prepared by the reaction of F2 and
MI-PEO.
Fig. 2. SEC curves of F2-PEO before and after fractionation compared with the
curves of MI-PEO.
Fig. 4. 1H NMR spectrum of AN2-PEO before (top) and after precipitation (bottom).

846
X. Jiang et al. / Reactive & Functional Polymers 71 (2011) 843–848
Fig. 5. UV spectra of the mixture of AN2 and F2-PEO before (dashed line) and after
core exchange (solid line) in toluene.
Fig. 7. SEC curves of star AN4-PEO from the reaction of F2-PEO and AN4.
and the methyl proton peaks e of PEO was 2:3, which indicated
that all of the MI-PEO had terminal maleimide groups. Further-
more, the MI-PEO product was analyzed by MALDI-TOF mass spec-
troscopy, and the spectrum revealed a series of peaks in range of
700–1200 Da, corresponding to the polymer MI-PEO. The interval
between neighboring peaks is 44 Da, corresponding to one ethyl-
ene oxide (EO) unit of PEO (data not shown).
8.0 g with toluene to obtain UV spectra. Comparing the intensity of
absorption features due to anthracene groups in wavelength region
of 300–400 nm, the efficiency of anthracene group consumption
was obtained.
3. Results and discussion
Subsequently, the MI-PEO was coupled with a bis-furan mole-
cule F2 (2:1 M ratio) to prepare a F2-PEO that has a core with
two MF adduct units. The reaction proceeded in CHCl3 solution at
40 °C for 72 h. From the SEC trace shown in Fig. 2, the MF reaction
did not proceed with high efficiency. In addition to the new main
peak, corresponding to a molecular weight that is twice that of
MI-PEO, a large peak at the elution time of MI-PEO was observed,
which may be attributed to unreacted MI-PEO as well as the MF
monoadduct. No improvement was found when performing this
reaction in other solvents, such as DMSO and THF. After the
coupling reaction, column chromatography was performed to re-
move the fraction at 30 min, and the product after fractionation
was also analyzed by SEC. As shown in Fig. 2, the peak at longer
elution time has been greatly reduced and appeared as a small
shoulder feature associated with the main product peak. The peak
at shorter elution time with linear polystyrene as standards
yielded relative Mn data (1 1 0 0) that was twice that of MI-PEO
(540), which implied the formation of F2-PEO with the two MF
3.1. Synthesis of the F2-PEO by MF DA reaction
The F2-PEO with two MF adduct units was prepared by the DA
coupling reaction between two MI-PEO and an F2 unit, as shown in
Scheme 2. First, the PEO with a furan protected maleimide terminal
(F-MI-PEO) was easily prepared by a condensation reaction of the
furan protected maleimide F-MI with PEO550–COOH, which pro-
ceeded in the presence of EDC and DMAP in CH2Cl2 at room tem-
perature. The structure of F-MI-PEO was identified by its 1H NMR
spectrum (Fig. 1), and the characteristic resonances from F-MI-
PEO, such as vinyl proton a and bridge protons b and c, were as-
signed at 6.51, 5.22, and 2.82 ppm, respectively. Then by removing
the furan group under reflux of toluene, the PEO with a maleimide
terminal (MI-PEO) was obtained, which could also be confirmed by
the disappearance of the 1H NMR peaks a, b and c due to F-MI-PEO
and the appearance of the vinyl proton d in Fig. 1. Additionally, the
integration ratio between the characteristic peaks due to protons d
Fig. 6. MALDI-TOF mass spectrum of AN2-PEO collected in reflection mode from the reaction of F2-PEO and AN2.

X. Jiang et al. / Reactive & Functional Polymers 71 (2011) 843–848
847
Fig. 8. MALDI-TOF mass spectrum obtained in linear mode of AN4-PEO by the reaction of F2-PEO and AN4.
adducts. As expected, the MF adduct exhibits endo/exo stereoiso-
mers, and the 1H NMR spectrum of the fractionated F2-PEO clearly
displays these isomers. As shown in Fig. 3, the ratio of endo/exo ad-
ducts (57/43) was calculated by comparing the integrations corre-
sponding to proton e (OCH2C) (endo/exo) at 5.22–4.68 ppm. The
peak corresponding to k at 6.75 ppm was attributed to the vinyl
protons of maleimide group in the small amount of unreacted
MI-PEO, in accordance with the SEC results. The peak due to proton
j at 7.45 ppm was attributed to the furan group (OCH = CH) from
F2. Because the bis-furan molecule F2 had been removed com-
pletely during fractionation of column chromatography, the pres-
ence of peak j indicated the presence of a small amount of the
MF monoadduct during the reaction of F2-PEO and F2. By compar-
ing the integration areas of peaks due to k, j and e, the proportion
of F2-PEO in the product reached 88 mol%, and the remaining
12 mol% of included the unreacted MI-PEO and PEO with a sin-
gle-MF adduct.
4.77 ppm, which were attributed to the CH2 adjacent to MA adduct
and the CH bridge-head of the cycloaddition product.
The efficiency of the MA reaction was also monitored by the UV
adsorption spectrum as shown in Fig. 5. Prior to reaction, UV
absorption spectrum of the mixture was measured, and the charac-
teristic absorption of anthracene units in AN2 was observed (dash
line). After reaction, the characteristic peaks of anthracene had al-
most disappeared (solid line), further indicating the consumption
of the AN2. The consumption efficiency of the anthracene group
was estimated to be in excess of 97% by comparing the absorption
values (k = 364 nm) of the solution before and after reaction.
After reaction, the MA adducts became the core of the AN2-PEO.
However, the molecular weight of the polymer AN2-PEO was sim-
ilar to that of F2-PEO, precluding characterization of this reaction
mixture by SEC. Therefore, the AN2-PEO product was analyzed
by MALDI-TOF mass spectroscopy. Examination of the MALDI-
TOF mass spectrum (Fig. 6) revealed two series of peaks in range
of 2000–2500 Da. The interval between neighboring peaks of each
series is m/z 44, corresponding to one EO unit of PEO. The peak ob-
served at m/z 2088.2 (Mobs) was assigned as a molecule of AN2-
PEO with 24 EO units. In detail, this mass of AN2-PEO can be calcu-
lated as: [24 ꢀ 44.04 (C2H4O, EO unit) + 978.9 (C54H46O16N2,
core) + 2 ꢀ 15.0 (C2H6, methyl end) + 23 (Na+), Mcalc = 2088.8]. An-
other series of peaks was observed due to the same polymer ion-
ized with potassium instead of sodium.
3.2. Replacing the core of F2-PEO to form AN2-PEO
The process of changing the polymer core was realized in the
reaction of an equimolar stock of the dianthracene units of AN2
and the MF adducts of F2-PEO via an in situ strategy where the
MF retro-DA reaction occurs, followed by a subsequent MA DA
reaction as shown in Scheme 1. The reaction was conducted in tol-
uene and refluxed for 48 h in the presence of AN2. In the 1H NMR
spectrum of AN2-PEO (Fig. 4, top), the proton resonances of endo/
exo stereoisomers disappeared and the characteristic peaks (r, o, p
and q) of F2 appeared, indicating the occurrence of the rDA reac-
tion. Furthermore, F2 could be removed by precipitation in diethyl
ether. As shown in Fig. 4 (bottom), multiplet signals corresponding
to the phenyl rings appeared in the range of 7.50–7.05 ppm instead
of signals due to anthracene ring protons (8.55–7.50) as a result of
MA cycloaddition. Moreover, we observed signals at 5.50 and
3.3. Forming star polymers by core reorganization
The above results indicated that the linear F2-PEO had been
converted to the AN2-PEO by core replacement in situ. This inter-
esting chemistry may be applied to generate topological polymers
by chain reorganization such as star polymers. When the agent
containing four anthracene units (AN4) reacted with two equiva-
lents of F2-PEO, four-arm star polymers AN4-PEO would be ob-

848
X. Jiang et al. / Reactive & Functional Polymers 71 (2011) 843–848
tained by the rDA decomposition of MF adducts and MA formation,
as shown in Scheme 1. During the reaction to form AN4-PEO, the
reactant ratio of F2-PEO to AN4 was kept to 2.1. Addition of excess
F2-PEO could promote formation of perfect structures of four-arm
star polymers.
polymer with a different core. Such chemistry was also applied
to prepare four-arm star polymers by reacting F2-PEO with AN4.
Therefore, this concept could be used to change not only the com-
position of a polymer chain but also chain architecture and, as a re-
sult, to tune the properties of polymer materials. This methodology
could be additionally interesting if the polymers with informative
functional groups were incorporated by the core exchanging
strategy.
The SEC trace of the reaction between F2-PEO and AN4, as
shown in Fig. 7, exhibits a new peak at shorter elution time, indi-
cating the formation of higher molecular weight products. Addi-
tionally, a small peak, consistent with that observed for the MI-
PEO precursor, was observed in the lower molecular weight region,
which was attributed to MI-PEO cleaved by the rDA reaction of the
F2-PEO at higher temperature. Spectroscopic analysis (UV and 1H
NMR) of this product gave similar results to those previously seen
for AN2-PEO; characteristic peaks due to anthracene units in UV
disappeared completely after reaction, demonstrating that the
anthracene units of AN4 had been consumed completely during
the MA reaction. No remaining peaks due to the anthracene ring
(d 8.55–7.50) could be found in 1H NMR, further supporting the
complete consumption of anthracene units. Moreover, the proton
resonances of the MF adduct in F2-PEO, including the protons of
the phenyl spacer and endo/exo stereoisomers, had completely dis-
appeared in the 1H NMR spectrum. This observation implied that
the MF adduct core of F2-PEO was destroyed during the rDA reac-
tion. Additionally, the signals from aromatic rings associated with
the MA adducts, observed as peaks at 5.49 ppm and 4.77 ppm from
methylene and methenyl of MA adduct rings, were observed, dem-
onstrating the formation of new MA adducts. These facts strongly
supported the formation of star polymers by core replacing
chemistry.
Acknowledgement
This work is supported by the Natural Science Foundation of
China (No. 21090350 and 21090353).
References
[1] J-M. Lehn, Chem. Eur. J. 5 (1999) 2455.
[2] O. Ramström, J-M. Lehn, Nat. Rev. Drug Discovery 1 (2001) 26.
[3] J-M. Lehn, Science 295 (2002) 2400.
[4] H. Otsuka, S. Nagano, Y. Kobashi, T. Maeda, A. Takahara, Chem. Commun. 46
(2010) 1150.
[5] N.L. Hill, J.L. Jarvas, F. Pettersson, R. Braslau, React. Funct. Polym. 68 (2008) 361.
[6] T. Ono, S. Fujii, T. Nobori, J-M. Lehn, Chem. Commun. (2007) 46.
[7] T. Ono, S. Fujii, T. Nobori, J-M. Lehn, Chem. Commun. (2007) 4360.
[8] Y. Ruff, J-M. Lehn, Angew. Chem. Int. Ed. 47 (2008) 3356.
[9] H. Otsuka, K. Aotani, Y. Higaki, A. Takahara, Chem. Commun. (2002) 2838.
[10] Y. Amamoto, M. Kikuchi, H. Otsuka, A. Takahara, Macromolecules 43 (2010)
5470.
[11] H. Otsuka, K. Aotani, Y. Higaki, Y. Amamoto, A. Takahara, Macromolecules 40
(2007) 1429.
[12] Y. Guan, Y. Zheng, J. Cui, X. Wan, Chin. J. Polym. Sci. 28 (2010) 257.
[13] J. Canadell, H. Fischer, G. de With, R.A.T.M. van Benthem, J. Polym. Sci. Part A:
Polym. Chem. 48 (2010) 3456.
The AN4-PEO product was also measured by MALDI-TOF mass
spectrometry in reflection mode but could not be observed due
to high molecular weight. However, the MS spectrum of AN4-
PEO acquired in linear mode was obtained as shown in Fig. 8.
Two series of m/z peaks with 44 Da (EO unit) intervals in two re-
gions, 800–1200 and 4400–5400, were observed, corresponding
to the two peaks in SEC trace (Fig. 7). The main peaks in the high
molecular weight region were attributed to the AN4-PEO star poly-
mers. The peak observed at 4455 Da (Mobs), labeled with an arrow,
was assigned as the AN4-PEO molecule including four MI-PEO with
48 EO units and an AN4 unit; the detailed calculation for AN4-PEO
is: [48 ꢀ 44.04 (C2H4O, EO unit) + 8 ꢀ 116.07 (8C4H4O4, succinate
group) + 4 ꢀ 315.3 (4C21H17O2N, MA adduct) + 68 (C5H8,
core) + 4 ꢀ 15.0 (4C2H6, methyl end) + 23 (Na+), Mcalc = 4454.7].
Additionally, the peaks in the low molecular weights region
(800–1200 Da) were attributed to excess MI-PEO. The peaks ob-
served at 890 Da (Mobs) were assigned as MI-PEO with 14 EO units;
the detailed calculated mass for MI-PEO is as follows: [14 ꢀ 44.04
(C2H4O, EO unit) + 236 (C10H6O6N) + 15.0 (CH3, methyl end) + 23
(Na+), Mcalc = 890.6].
[14] I. Kosif, E–J. Park, R. Sanyal, A. Sanyal, Macromolecules 43 (2010) 4140.
[15] A. Gandini, A.J.D. Silvestre, D. Coelho, J. Polym. Sci. Part A: Polym. Chem. 48
(2010) 2053.
[16] A.M. Atta, S.M. El-Saeed, R.K. Farag, React. Funct. Polym. 66 (2006) 1596.
[17] N.V. Tsarevsky, K. Matyjaszewski, Macromolecules 35 (2002) 9009.
[18] J. Kamada, K. Koynov, C. Corten, A. Juhari, J.A. Yoon, M.W. Urban, A.C. Balazs, K.
Matyjaszewski. Macromol. 43 (2010) 4133.
[19] M.L. Szalai, D.V. McGrath, D.R. Wheeler, T. Zifer, J.R. McElhanon,
Macromolecules 40 (2007) 818.
[20] N. Aumsuwan, M.W. Urban, Polymer 50 (2009) 33.
[21] N. Teramoto, Y. Arai, M. Shibata, Carbohydr. Chem. 64 (2006) 78.
[22] A. Vieyres, T. Lam, G. Gillet, G. Franc, A. Castonguay, A. Kakkar, Chem.
Commun. 46 (2010) 1875.
[23] H.L. Wei, Z. Yang, H.J. Chu, J. Zhu, Z.C. Li, J.S. Cui, Polymer 51 (2010) 1694.
[24] H.L. Wei, Z. Yang, L.M. Zheng, Y.M. Shen, Polymer 50 (2009) 2836.
[25] S. Rimmer, P. Tattersall, J.R. Ebdon, N. Fullwood, React. Funct. Polym. 41 (1999)
177.
[26] C. Goussé, A. Gandini, P. Hodge, Macromolecules 31 (1998) 314.
[27] T. Dispinar, R. Sanyal, A. Sanyal, J. Polym. Sci. Part A: Polym. Chem. 45 (2007)
4545.
[28] N.W. Polaske, D.V. McGrath, J.R. McElhanon, Macromolecules 43 (2010) 1270.
[29] G. Rana, P.B. Catalina, G. Alessandro, Macromolecules 35 (2002) 7246.
[30] M. Watanabe, N. Yoshie. Polym. 47 (2006) 4946.
[31] B.J. Adzima, H.A. Aguirre, C.J. Kloxin, T.F. Scott, C.N. Bowman, Macromolecules
41 (2008) 9112.
[32] Y.L. Liu, C.Y. Hsieh, Y.M. Chen, Polymer 47 (2006) 2581.
[33] S. Magana, A. Zerroukhi, C. Jegat, N. Mignard, React. Funct. Polym. 70 (2010)
442.
4. Conclusions
[34] K. Adachi, A.K. Achimuthu, Y. Chujo, Macromolecules 37 (2004) 9793.
[35] Y. Imai, H. Itoh, K. Naka, Y. Chujo, Macromolecules 33 (2000) 4343.
[36] H. Durmaz, F. Karatas, U. Tunca, G. Hizal, J. Polym. Sci. Part A: Polym. Chem. 44
(2006) 499.
[37] A.F. Buckmann, M. Morr, Makromol. Chem. 182 (1981) 1379.
[38] G. Mantovani, F. Lecolley, L. Tao, D.M. Haddleton, J. Clerx, J.J.L.M. Cornelissen,
K. Velonia, J. Am. Chem. Soc. 127 (2005) 2966.
We have obtained a well-defined polymer F2-PEO that has a
replaceable core of MF adducts. At a higher temperature, rDA reac-
tion of the MF adducts within the polymer chain center occurred
and the MA addition reaction simultaneously proceeded in the
presence of anthracene derivatives, AN2s, to generate a new PEO
[39] X. Lei, J.A. Porco, Org. Lett. 6 (2004) 795.