Synthesis and intrinsic blue fluorescence study of hyperbranched poly(ester-amide-ether)

Article abstract of DOI:10.1007/s11426-010-4154-1

A series of hyperbranched poly(ester-amide-ether)s (H-PEAEs) were synthesized via the A₂+CB₃ approach by the self-transesterification of ethyl ester-amide-ethers end-capped with three hydroxyl groups and ethyl ester group at two terminals. The molecular structures were characterized with ¹H NMR and FT-IR spectroscopy. The number average molecular weights were estimated by GPC analysis to possess bimodal wide distribution from 1.57 to 2.09. The strong inherent blue fluorescence was observed at 330 nm for excitation and 390 nm for emission. Moreover, the emission intensity and fluorescence quantum yield increased along with the incorporated ether chain length, as well as almost linearly with the H-PEAE concentration in an aqueous solution. For comparing the fluorescence performance, the linear poly(ester-amide-ether) (L-PEAE) and hyperbranched poly(ester-amide) (H-PEA) were synthesized. The results showed that the coexistence of ether bond and carboxyl group in the molecular chain was essential for generating the strong fluorescence. However, the compact backbone of H-PEAE would be propitious to the enhancement of fluorescence properties.

Full text of DOI:10.1007/s11426-010-4154-1

SCIENCE CHINA
Chemistry
December 2010 Vol.53 No.12: 2452–2460
doi: 10.1007/s11426-010-4154-1
• ARTICLES •
· SPECIAL TOPIC · Highly Branched Polymers – Promising Architectural Macromolecules
Synthesis and intrinsic blue fluorescence study of
hyperbranched poly(ester-amide-ether)
ZHANG Yong, FU Qi & SHI WenFang*
CAS Key Laboratory of Soft Matter Chemistry; Department of Polymer Science and Engineering,
University of Science and Technology of China, Hefei 230026, China
Received August 11, 2010; accepted September 3, 2010
A series of hyperbranched poly(ester-amide-ether)s (H-PEAEs) were synthesized via the A2+CB3 approach by the self-trans-
esterification of ethyl ester-amide-ethers end-capped with three hydroxyl groups and ethyl ester group at two terminals. The
molecular structures were characterized with 1H NMR and FT-IR spectroscopy. The number average molecular weights were
estimated by GPC analysis to possess bimodal wide distribution from 1.57 to 2.09. The strong inherent blue fluorescence was
observed at 330 nm for excitation and 390 nm for emission. Moreover, the emission intensity and fluorescence quantum yield
increased along with the incorporated ether chain length, as well as almost linearly with the H-PEAE concentration in an
aqueous solution. For comparing the fluorescence performance, the linear poly(ester-amide-ether) (L-PEAE) and hyper-
branched poly(ester-amide) (H-PEA) were synthesized. The results showed that the coexistence of ether bond and carboxyl
group in the molecular chain was essential for generating the strong fluorescence. However, the compact backbone of H-PEAE
would be propitious to the enhancement of fluorescence properties.
synthesis, self-transesterification, hyperbranched poly(ester-amide-ether), fluorescence property
Au and CdSe nanodot [12], and fluorescein sodium [13].
1 Introduction
The poly(amido amine) (PAMAM) and poly(propylene
imine) (PPI) dendrimers were reported to emit the strong
blue fluorescence. Moreover, the fluorescent intensity was
enhanced at a lower pH value and higher temperature, as
well by the oxidation treatment [14, 15]. These results indi-
cated that the photoluminescence performance of PAMAM
and PPI was resulted from the formation of fluorescence-
emitting moieties in the dendritic structures [16]. Moreover,
the hyperbranched poly(amino-ester)s and polyethylenimi-
nes were reported to emit the intrinsic blue fluorescence.
Therefore, the photoluminescence performance might be an
inherent property of dendritic molecules. The oxidation
treatment only enhanced the fluorescent intensity [17]. The
amine bonds along the molecular chains may play a key role
for emitting the fluorescence [18]. However, to the best of
our knowledge, the hyperbranched fluorescent polymers
containing ether linkage are seldom reported.
Fluorescence is a technology that is now used routinely in
optical [1] and biomedical science research [2, 3]. The
fluorescent materials are normally consisted of traditional
fluorophores such as aromatic moieties, inorganic species
like lanthanides, quantum dots, or metal nanoclusters.
In recent years, a variety of hyperbranched fluorescent
polymers have been prepared through many creative syn-
thetic methods, including end-capping with traditional fluoro-
phores such as N,N-dimethylaminobenzaldehyde [4–6], and
pyrene [7]; building dendritic architectures possessing fluo-
rescent groups such as aromatic carbazole [8], oxadizaole
[9], triarylpyrazoline [10], and binaphtyl [11]; and encapsu-
lated metallic fluorescent nanodots or dye molecules such as
*Corresponding author (email: wfshi@ustc.edu.cn)
© Science China Press and Springer-Verlag Berlin Heidelberg 2010
chem.scichina.com
www.springerlink.com

ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
2453
In this paper, the hyperbranched poly(ester-amide-ether)
(H-PEAE) was synthesized through the “A2+CB3” approach
based on commercial raw materials, and characterized by
FT-IR and 1H NMR spectroscopy. The fluorescent behavior
of H-PEAE was investigated through changing the ether
linkage length and considering the molecular architecture
difference. The photoluminescent mechanism was basically
discussed by the comparison with hyperbranched poly(ester-
amide) (H-PEA).
NaHCO3 aq., distilled water, finally dilute NaCl aq. and
distilled water again. The anhydrous MgSO4 was used to
dry the organic layer, and then removed by filtration. The
organic solvent CH2Cl2 was evaporated under reduced
pressure, finally obtaining the diethyl ester-ether as color-
less oil.
For preparing the diethyl ester-ethers incorporated with
two, three and four ether linkage segments, 0.44 moL (23.4 g)
acrylonitrile reacted with 0.2 moL (12.4 g) ethylene glycol,
(21.22 g), diethylene glycol, or (30.03 g) triethylene glycol,
then further with excess ethanol, yielding the transparent
yellowish oil, named M-mono (85.8%), M-di (61.9.%), and
M-tri (52.5%), respectively.
2 Experimental
2.1 Materials
1H NMR (300 MHz, CDCl3): for M-mono(ppm), 
1.10–1.29 (6H, CH3), 2.48–2.62 (4H, CH2COO), 3.48–3.75
(8H, CH2O), 3.98–4.15 (4H, CH2CH3); for M-di (ppm), 
1.12–1.30 (6H, CH3), 2.48–2.65 (4H, CH2COO), 3.49–3.78
(12H, CH2O), 4.02–4.18 (4H, CH2CH3); for M-tri (ppm), 
1.12–1.29 (6H, CH3), 2.48–2.66 (4H, CH2COO), 3.51–3.79
(16H, CH2O), 4.03–4.19 (4H, CH2CH3).
All chemicals were purchased from Shanghai First Reagent
Co. (China), and used as received without further purifica-
tion except for acrylonitrile, which was distilled before use.
2.2 Measurements
The 1H NMR analysis was performed on a Bruker 300 MHz
nuclear magnetic resonance instrument (Bruker Bio-Spin
Co., Switzerland). The FT-IR spectra were recorded on a
Perkin-Elmer Spectrum 2000 Fourier transform infrared
spectrometer (Perkin-Elmer Instruments, USA). The UV-vis
analysis was carried out on a Shimadzu UV-2401PC ultra-
violet-visible spectrometer (Shimadzu Corporation, Japan).
The fluorescence spectra were recorded on a Perkin-Elmer
LS-55 Fluorescence Spectrometer (Perkin-Elmer, USA).
The gel permeation chromatographic (GPC) analysis was
performed on a GPC apparatus (Waters, USA) at 25 °C. THF
was used as an eluent with an elution rate of 1.0 mL/min.
The standard PSt was used for calibrating the samples. The
fluorescence quantum yield was measured with the excita-
tion wavelength of 335 nm using quinine sulfate (dissolved
in 0.5 M H2SO4 aq.) as a standard.
Synthesis of hyperbranched poly(ester-amide-ether)s
(H-PEAEs)
The H-PEAEs were prepared by a general procedure as fol-
lows. The equivalent molar amount of diethyl ester-ether
and trishydroxyl methylaminomethane (THAM) were dis-
solved in DMSO. An excess of anhydrous K2CO3 was then
added into the solution under stirring, and reacted at 25 °C
for 15 h. After removed K2CO3 by filtration and DMSO by
evaporation under reduced pressure, 0.1 wt% Ti(OBu)4 as a
catalyst was added and reacted at 140 °C for 2 h, 150 °C for
2 h, 160 °C for 2 h, and then 170 °C for 1 h under reduced
pressure (~ 25 mmHg) and vigorously stirring. After cooling
to room temperature, the product was dissolved into DMF
and precipitated into ethyl ether three times and then dried
in vacuo at 65 °C for 24 h. The final products, named poly
(H-PEAE-mono), poly(H-PEAE-di) and poly(H-PEAE-tri),
were obtained with the yields of 44.7%, 36.1%, and 35.3%,
respectively.
2.3 Synthesis
1H NMR (300 MHz, DMSO-d6): for poly(H-PEAE-mono)
(ppm),  7.09–7.42 (CONH), 4.49–5.28 (OH), 3.88–4.25 (C-
(CH2O)n(CH2OH)3-n), 2.99–3.85 (group, C(CH2O)n(CH2OH)3-n,
CH2OCH2CH2OCH2), 2.29–2.61 (CH2COO, CH2CONH);
for poly(H-PEAE-di) (ppm),  6.92–7.46 (CONH), 4.29–5.40
(OH), 3.85–4.29 (C(CH2O)n(CH2OH)3-n), 2.92–3.71 (group,
C(CH2O)n(CH2OH)3-n, CH2OCH2CH2OCH2), 2.40–2.52
(CH2COO, CH2CONH); for poly(H-PEAE-tri) (ppm), 
7.15–7.35 (CONH), 4.45–5.29 (OH), 3.82–4.33 (C(CH2O)n-
(CH2OH)3-n), 2.97–3.64 (group, C(CH2O)n(CH2OH)3-n,
CH2OCH2CH2OCH2), 2.29–2.59 (CH2COO, CH2CONH).
Synthesis of diethyl ester-ethers
The diethyl ester-ethers were synthesized using the similar
approach reported in the literature [19, 20]. Acrylonitrile
was firstly added into the mixture of 40 wt% NaOH aque-
ous solution and glycol at 0–5 °C over 1 h. After stirred at
room temperature over night, the reactant was neutralized
with dilute HCl, and then dissolved in ethyl acetate. The
organic layer was washed with distilled water three times,
dried with anhydrous MgSO4, and then concentrated, ob-
taining a dicyano derivative as colorless transparent oil. The
obtained dicyano derivative further reacted with excess
ethanol at the presence of conc. H2SO4 under reflux until the
CN peak in the FT-IR spectrum disappeared. After the
redundant ethanol was removed under reduced pressure, the
crude product was treated in turn with CH2Cl2, saturated
Synthesis of hyperbranched poly(H-PEA)
Sebacic acid (10 g) was firstly dissolved into the mixture of
ethanol and benzene. Then 1 mL of conc. H2SO4 was added,

2454
ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
and stirred under reflux for 4 h. After the solvents were re-
moved under reduced pressure, the reactant was dissolved
in CH2Cl2, then washed with saturated NaHCO3 aq., and
distilled water three times in turn. The organic layer was
dried with anhydrous MgSO4. After the removal of MgSO4
by filtration and CH2Cl2 by evaporation under reduced
pressure, diethyl decanedioate (DEDDO) was obtained as
using a rotary evaporator, diethyl 4,7-dioxadecane-1,10-
dioate (2.62 g) and 0.1 wt% Ti(OBu)4 were added into the
flask, and reacted at the temperature range of 140 to 170 °C
for 7 h under reduced pressure (~ 25 mmHg) with vigor-
ously stirring. After cooling to room temperature, the prod-
uct was dissolved in THF and precipitated into ethyl ether
three times, obtaining the linear poly(ester amide ether),
named L-PEAE, as brown oil (2.86 g, 52.96%).
1
colorless oil (11.3 g, 88.4%). H NMR (300 MHz, CDCl3)
(ppm):  1.15–1.39 (6H, CH3, 8H, (CH2)4), 1.50–1.67 (4H,
CH2CH2COO), 2.18–2.33 (4H, CH2CO), 4.01–4.18 (4H,
CH2CH3). Then 10.00 g DEDDO reacted with 4.69 g
THAM, yielding a pale-yellow solid (8.35 g, 56.85%).
1H NMR (300 MHz, DMSO-d6) (ppm):  7.05–7.51 (CONH),
4.35–5.19 (OH), 3.75–4.11 (C(CH2O)n(CH2OH)3-n), 2.95–3.61
(C(CH2O)n(CH2OH)3-n), 2.15–2.33 (OCOCH2(CH2)7CONH),
1.82–2.15 (OCO(CH2)7CH2CONH), 1.32–1.61 (OCOCH2CH2-
(CH2)4CH2CH2CONH), 0.91–1.31 (OCOCH2CH2(CH2)4CH2-
CH2CONH).
1H NMR (300 MHz, CDCl3) (ppm):  6.65–7.13 (CONH),
4.02–4.32 (COOCH2), 3.61–3.89 (OCH2CH2O), 3.52–3.61
(OCH2CH2COO), 3.42–3.52 (OCH2CH2CONH), 3.24–3.42
(CONHCH2), 2.51–2.69 (OCOCH2), 2.28–2.51 (NHCOCH2),
1.15–1.28 (CH3).
3 Results and discussion
3.1 Synthesis and characterization
The H-PEAEs were synthesized through a novel “A2 +CB3”
approach by the so-called self-transesterification of ethyl
ester-amide-ethers end-capped with three hydroxyl groups
and ethyl ester group at two terminals, as shown in Scheme
1. The ethylene glycol incorporated with ether linkage re-
acted with acrylonitrile, following by the esterification of
nitrile group with ethanol at the presence of conc. H2SO4.
Synthesis of linear poly(ester amide ether) (L-PEAE)
3.67 g ethanolamine reacted with 2.62 g diethyl 4,7-dioxa-
decane-1,10-dioate under stirring and reduced pressure
(~ 25 mmHg) at 60 °C for 4 h, and then at 100 °C until the
peak at 1730 cm1 disappeared monitored by FT-IR spec-
troscopy. After the removal of superfluous ethanolamine
Scheme 1 Schematic route for synthesis of H-PEAEs.

ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
2455
1657 cm1, ester carbonyl at 1734 cm1, ether C-O at 1056
cm1, and the bend vibration of N-H at 1569 cm1 were ob-
viously observed.
The resultant diethyl ester-ether further reacted with the
amino group of THAM in DMSO at the presence of anhy-
drous K2CO3 as a catalyst at room temperature, theoretically
obtaining the ethyl ester-amide-ether with three end-hydroxyl
groups, as a CB3 monomer according to Flory’s theory [21].
As a result, the gelation during the polymerization of CB3
monomers for producing H-PEAEs was avoided. For com-
parison, H-PEA and L-PEAE were synthesized, as shown in
Schemes 2 and 3, respectively.
For characterizing the chemical structure of H-PEAE, the
FT-IR, 1H NMR, and GPC spectroscopic analysis were car-
ried out based upon the comparison with L-PEAE and
H-PEA. As a typical example, from the FT-IR spectrum of
H-PEAE-mono, as shown in Figure 1, the stretching vibra-
tion of O-H at 3386 cm1, amide carbonyl absorption at
Due to the similar molecular structures of H-PEAEs, the
1H NMR spectrum of H-PEAE-mono was studied as a repre-
sentative, as shown in Figure 2(A). The peaks at 3.2–3.9 ppm
are attributed to the protons of ether linkage (CH2OCH2).
The weak peaks at 7.0–7.5 ppm are attributed to the amide
proton, suggesting that several kinds of structural units in
the polymer chain were formed, which is similar with that
1
reported in literature [22]. The peaks in the H NMR spec-
trum of H-PEAE attributed to the protons in linear, branch-
ing and terminal groups are heavily overlapped, resulting in
a failure in the calculation of branching degrees of
1
H-PEAEs. The H NMR spectrum of L-PEAE is shown in
Scheme 2 Schematic route for synthesis of H-PEA.
Scheme 3 Schematic route for synthesis of L-PEAE.

2456
ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
Figure 2(B). The peaks at 3.2–3.9 ppm are attributed to the
protons of ether linkage (CH2OCH2). The peaks at
2.3–2.5 ppm and 2.5–2.8 ppm are attributed to the protons
of methylene near amide group (CH2CONH) and near
1
ester group (CH2COO), respectively. From the H NMR
spectrum of H-PEA, as shown in Figure 2(C), the peaks at
1.1–1.3 ppm and 1.3–1.6 ppm are attributed to the protons
of methylene of alkyl chains, while the peaks at 1.9–2.2
ppm and 2.2–2.3 ppm to the protons of methylene near the
amide group (CH2CONH) and ester group (CH2COO),
respectively.
The number average molecular weights of H-PEAEs,
H-PAE and L-PEAE were determined by GPC, as shown in
Figure 3, and the data are listed in Table 1. It can be found
that the polydispersity indices (PDI) of H-PEAE-mono and
L-PEAE are relative smaller than others. Moreover, the bio-
modal distribution was clearly observed for H-PEAEs and
H-PEA, due to the dense hydroxyl groups in the CB3 monomer,
which was often obtained for branched polymers [23].
Figure 1 FT-IR spectrum of H-PEAE-mono.
3.2 Fluorescence properties
As shown in Figure 4, the H-PEAEs possess the strong
fluorescence property, although no traditional fluorophore
exists in the polymeric chains. The H-PEAE-mono, H-PEAE-
di and H-PEAE-tri possess the excitation bands at 330, 329
Figure 3 GPC traces of H-PEAEs, H-PEA and L-PEAE.
Table 1 GPC data of H-PEAEs, H-PEA and L-PEAE
Polymer
H-PEAE-mono
H-PEAE-di
H-PEAE-tri
H-PEA
Mw (g/mol)
11820
Mn (g/mol)
7530
PDI
1.57
2.07
2.09
1.98
1.46
13130
6340
13080
6260
10420
5260
Figure 2 1H NMR spectra of H-PEAE-mono in DMSO–d6 (A), L-PEAE
in CDCl3 (B) and H-PEA in DMSO–d6 (C).
L-PEAE
5480
4090

ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
2457
H-PEAE-mono except for the ether linkage. The excitation
and emission fluorescence spectra of diethyl ester-ether for
H-PEAE-mono and monomer DEDDO for H-PEA are
shown in Figure 5. It can be seen that the diethyl ester-ether
and DEDDO have two same excitation bands at 289 and
355 nm. However, the diethyl ester-ether has two emission
bands at 400 and 442 nm, whereas DEDDO has only one
emission band at 400 nm. The fluorescence properties of
H-PEAE-di and H-PEAE-tri films were measured, as shown
in Figure 6, and also show that the emission intensity in-
creased with the increase of ether linkage length in diethyl
ester-ether monomer. Whereas, the H-PEA shows a very
weak fluorescence band. This observation suggests that the
ether linkage in the H-PEAEs play an important role in
generating the luminescent species.
Moreover, it was found that the emission intensity in-
creased almost linearly along with the H-PEAE-mono
aqueous solution concentration, as shown in Figure 7. This
result indicates that there is no effect of intermolecular in-
teraction on the fluorescence properties of H-PEAEs.
Therefore, it can be concluded that the fluorescence proper-
ties of H-PEAEs and L-PEAE are dependant on the in-
tramolecular interaction of polymeric chains.
Figure 8 shows the emission spectra of H-PEAE-mono
measured at different reaction times. It can be seen that the
Figure 4 Fluorescence spectra of H-PEAEs and L-PEAE. (A) Excitation
spectra emitted at 400 nm; (B) Emission spectra excited at 335 nm.
and 328 nm, and emission bands at 388, 394, 390 nm, re-
spectively, in comparison with the excitation band at 335
nm and emission band at 389 nm for L-PEAE.
The quantum yield was calculated based on the following
formula:
A 
F


1
2 
2 1
A 
F
1
2
where, F1 is the fluorescence intensity of the reference (qui-
nine sulfate) with quantum yield (1), F2 is the fluorescence
intensity of the molecule with unknown quantum yield (2);
A is the absorption of the corresponding sample [24].
Therefore, the fluorescence quantum yield of H-PEAE- mono,
H-PEAE-di, H-PEAE-tri and L-PEAE were calculated to be
0.06, 0.12, 0.19 and 0.11, respectively. These observations
suggest that the compact backbone of H-PEAEs is not impor-
tant in the formation of luminescent center. On the other
hand, the emission intensity and fluorescence quantum yield
increased along with the ether linkage length in the diethyl
ester-ether monomer. Moreover, the fluorescence quantum
yields of H-PEAEs and L-PEAE are larger than that of hy-
perbranched and linear polyethylenimines which have the
largest quantum yield of 0.06, as reported in the literature
[18].
Figure 5 Fluorescence spectra of A2-mono and DEDDO. (A) Excitation
spectra emitted at 400 nm; (B) Emission spectra excited at 330 nm.
The molecular structure of H-PEA is similar with that of

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ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
intramolecular interaction in H-PEAEs.
The further measurements were performed to elucidate
the intrinsic fluorescence of H-PEAE-mono. The fluores-
cence emission spectra of the H-PEAEs and L-PEAE at
different excitation wavelengths were recorded, as showed
in Figure 9(A). It can be seen that the emission band shifts
to the longer wavelength with increasing the excitation
wavelength. The emission intensity increased until the ex-
citation wavelength reached to 330 nm, and then decreased.
The emission intensity is very weak when the excitation
wavelength was at 410 nm. The emission spectrum for the
excitation wavelength of 310 nm shows another weak peak
at 625 nm except for the peak at about 390 nm, which re-
veals the existence of three emitting polymeric species. The
shorter wavelength species was detected only by short
wavelength excitation. The emitting species at 625 nm was
only detected by 310 nm excitation. H-PEAE-di and
L-PEAE show the similar emission spectra with H-PEAE-
mono, as shown in Figure 9(B) and Figure 9(C). All three
polymers have three emitting polymeric species. The emis-
sion spectra of H-PEAE-tri at different wavelengths are
shown in Figure 9(D). The emission spectrum shows two
peaks at 310 nm, indicating the existence of two emitting
polymeric species, which is different from H-PEAE-mono,
H-PEAE-di and L-PEAE. A similar inherent luminescence
property exhibited from silica based on sol–gel materials
has been reported, pointing out the generation of emitting
nanocluster species, and proved by the dependence of emis-
sion wavelength on the excitation wavelength [25, 26].
Moreover, the similar inherent blue luminescence property
for hyperbranched and linear polyethylenimines has also
been reported, probably due to the creation of amine rich
nanocluster and electron–hole recombination process [18,
27]. Therefore, it might be concluded that the mechanism
for showing strong the inherent blue luminescence by
H-PEAEs and L-PEAE probably is due to the ether rich
nanocluster and electron–hole recombination process. This
was also proved by the fact that the H-PEA showed very
weak fluorescence property, because of the absence of ether
linkage in the polymeric chain. However, no photolumines-
cence was observed from polyethylene glycol, so single
ether linkage is not the reason for generating the lumines-
cence. The coexistence of ether linkage and carbonyl group
in H-PEAEs is essential for generating the strong fluores-
cence. Moreover, the coexistence of NH and C=O groups is
also very important for providing the states of delocalized
electron–hole recombination [25]. Furthermore, the chemi-
cal groups possess electron–donating capacity also play a
key role in generating the inherent luminescence property
[26]. In the H-PEAE and L-PEAE chains, the oxygen atom
of ether linkage is an electron–donating group and the car-
bonyl group provides the state for delocalized electron–hole
recombination. Therefore, both H-PEAEs and L-PEAE
showed strong fluorescence intensity, whereas, the H-PEA
showed very weak fluorescence.
Figure 6 Emission spectra of films of H-PEAEs and H-PEA excited at
380 nm.
Figure 7 Emission intensity of H-PEAE-mono aqueous solution at dif-
ferent concentrations.
Figure 8 Emission spectra of H-PEAE-mono at different reaction times.
fluorescence emission intensity increased along with the
polymerization time. H-PEAE-mono shows the very weak
fluorescence intensity when reacted for 2 h. This observa-
tion also confirmed that the emission intensity increased
with increasing the molecular weight and thus the number
of intramolecular interaction species. Therefore, it can be
concluded that the photoluminescence is derived from the

ZHANG Yong, et al. Sci China Chem December (2010) Vol.53 No.12
2459
Figure 9 Emission spectra of H-PEAES at different excitation wavelengths. (A) H-PEAE-mono, (B) L-PEAE, (C) H-PEAE-di, (D) H-PEAE-tri.
5443–5452
4 Conclusions
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The H-PEAEs were synthesized via the A2 + CB3 approach
by the self-transesterification of ethyl ester-amide-ethers.
The molecular structures were well characterized with H
1
4
5
NMR and FT-IR spectroscopy, and GPC analysis. The ob-
tained H-PEAEs possess strong inherent blue fluorescence
and have excitation bands at about 330 nm and emission
bands at about 390 nm. And H-PEAEs also have better
fluorescence properties than the reported inherent fluores-
cence polymers containing amine group. From the com-
parison of fluorescence intensity with L-PEAE, it was found
that the coexistence of ether linkage and carbonyl group in
the polymeric chain plays an important role in generating
the luminescence, but not the 3D-architecture of H-PEAEs.
The higher local concentration of ether linkage can enhance
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