White photoluminescent material based on a functional polysiloxane complex with lanthanide ions (Eu3+ and Dy3+)

Article abstract of DOI:10.1039/c3ra41621f

This paper reports on a white light-emitting, polysiloxane-based material obtained by coordinating lanthanide ions (Eu³⁺ and Dy³⁺) into α, ω-N,N′-diphenylmalonamide terminated polydimethylsiloxane (PMP). PMP is a new functional polysiloxane designed and synthesized in this work. The luminescence emissions of the raw materials and the composite material were measured. The composite material produced a white luminescence with Commission Internationale de l'Eclairage coordinates of (0.32, 0.34). The polysiloxane backbone plays a role in the luminescence performance of both the PMP and the composite material. Interactions between the terminal groups of the PMP host and the rare earth ions, as revealed by infrared and fluorescence data, contribute to the emission via the antenna effect. The surface morphologies of PMP and the composite material are smooth platforms piled up by layer stacking, as observed with SEM. DSC data were also collected to research the thermal behaviour of these materials. The introduction of phenyl amide groups led to a quantum yield of 0.3% for the PMP-Eu³⁺-Dy ³⁺ composite material.

Full text of DOI:10.1039/c3ra41621f

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PAPER
White photoluminescent material based on a functional
polysiloxane complex with lanthanide ions (Eu3+ and
Dy3+)3
Cite this: RSC Advances, 2013, 3,
9957
Fuyuan Zheng, Jie Zhang* and Shengyu Feng
This paper reports on a white light-emitting, polysiloxane-based material obtained by coordinating
lanthanide ions (Eu3+ and Dy3+) into a, v-N,N9-diphenylmalonamide terminated polydimethylsiloxane
(PMP). PMP is a new functional polysiloxane designed and synthesized in this work. The luminescence
emissions of the raw materials and the composite material were measured. The composite material
produced a white luminescence with Commission Internationale de l’Eclairage coordinates of (0.32, 0.34).
The polysiloxane backbone plays a role in the luminescence performance of both the PMP and the
composite material. Interactions between the terminal groups of the PMP host and the rare earth ions, as
revealed by infrared and fluorescence data, contribute to the emission via the antenna effect. The surface
morphologies of PMP and the composite material are smooth platforms piled up by layer stacking, as
observed with SEM. DSC data were also collected to research the thermal behaviour of these materials. The
introduction of phenyl amide groups led to a quantum yield of 0.3% for the PMP–Eu3+–Dy3+ composite
material.
Received 21st January 2013,
Accepted 17th April 2013
DOI: 10.1039/c3ra41621f
www.rsc.org/advances
metal ions into the same host.8–12 It is of interest to find more
ions and hosts that are suitable to obtain white-light-emitting
Introduction
Natural light is the ideal product that people want to get from
luminescent devices. So white light emission with CIE
coordinates around (0.33, 0.33) is an important goal for all
stages of research in the field of luminescent materials, such
as LEDs (Light Emitting Diodes) and photoluminescent
materials. Generally, there are two ways to prepare white light
emitting luminescent materials. One of the most effective ways
is to synthesize a single component material, emitting white
light in general. These materials can be either a complex of a
single metal and a single organic host,1,2 or a polymer
obtained through the covalent bonding of groups that emit
different colours.3–5 However, these kinds of materials are
difficult to find. Moreover, when the components are bound
together to prepare luminescent materials, it is difficult to
tune the emissions of the materials. Another way to get white-
light-emitting materials is to blend several components with
different colour emissions. This method is broadly employed,
because these components are easier to find. Some researchers
have mixed different colour luminescent organics or macro-
molecules to obtain white light emissions.6,7 In other work,
white light emissions were achieved by incorporating different
luminescent materials for commercial applications.
Lanthanide ions are widely used for the preparation of
luminescent materials, such as illumination lamps and cell
optical imaging.13–17 They are characterized by a long-lived
excited state, as well as strong and narrow emission bands in
the visible region, resulting from their f–f transitions.18–21 The
rare earth ions can produce visible light signals with less
energy input than other metal ions. Small molecules are easy
to find as hosts for lanthanide ions and to coordinate with the
ions,22–25 but show little potential for mechanical casting
when used as solid materials. For easy materials processing,
we should turn to macromolecular hosts.26–28
Polysiloxane is considered an ideal macromolecular host
for lanthanide ions in the preparation of luminescent
materials. It has been used in various applications such as
impact-resistant plastics, electronic adhesives and biological
engineering materials, because of its low glass transition
temperature, low variation of viscosity with temperature, high
flexibility of its main chains, high gas permeability, physiolo-
gical inertness and excellent thermal stability.29–32 In addition,
the transparency of the Si–O–Si chain is also important for
polysiloxane to be used as a host, in that the materials based
on it can be easily excited optically.33
Key Laboratory of Special Functional Aggregated Materials, Ministry of Education,
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100,
People’s Republic of China. E-mail: jiezhang@sdu.edu.cn
Many fluorescent materials based on lanthanide ion-doped
polysiloxanes have been studied.34,35 Zha and his co-workers
incorporated lanthanide ion-containing nanoparticles into a
Electronic supplementary information (ESI) available. See DOI: 10.1039/
3
c3ra41621f
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the reaction. Then the mixture was cooled down to room
temperature. The MA precipitated from the solution was
obtained as a white powder by filtration. Yield: 72%. H NMR
polysiloxane host to prepare luminescent hybrid thin films
with the advantages of both the inorganic glasses and the
silica.36 Lu et al. prepared various colourful luminescent
materials through doping rare earth ions into polysiloxanes
with different side chains.37,38 In our previous work, colour-
tunable diethyl malonate-terminated polysiloxanes with incor-
porated europium(III) and terbium(III) ions were prepared and
studied.39 By altering the ratio of Eu3+/Tb3+ in these materials,
easily tuneable colourful photoluminescent emissions were
observed from their THF solutions.
1
(300 MHz, DMSO): d 9.96 (m, 2H), 7.60 (dd, J = 8.6, 1.0 Hz, 4H),
7.30 (m, 4H), 7.05 (m, 2H), 5.83 (ddt, J = 16.9, 10.2, 6.6 Hz, 1H),
5.14 (dd, J = 17.2, 1.9 Hz, 1H), 5.03 (m, 1H), 3.60 (t, J = 7.4 Hz,
1H), 2.67 (t, J = 7.0 Hz, 2H) (Fig. S3, ESI ). 13C NMR (300 MHz,
3
CDCl3): d 168.36, 136.81, 132.88, 128.50, 124.43, 119.92,
118.13, 55.63, 36.87 (Fig. S4, ESI ).
3
Synthesis of a, v-N,N9-diphenylmalonamide terminated
However, despite considerable effort to develop lanthanide
ion-complex luminescent materials based on polysiloxane
hosts, white light-emitting material has not been achieved.
In previous work, the polysiloxane was used only as a suitable
host. The Si–O–Si backbone chain’s contribution to the
luminescent performance of the materials had not been
considered.
polydimethylsiloxane (PMP)
HP (10 mmol) was mixed with 22 mmol MA in a three-necked
flask under nitrogen. 50 mL of THF and 0.3 mL Pt catalyst41
were then added into the mixture. The system was kept stirring
at 90 uC until the FT-IR peak of the Si-H band at 2125 cm21
disappeared. After evaporation of the solvent and separation of
the catalyst, unreacted MA was separated using diethyl ether.
PMP was obtained as a brown solid. The synthesis process of
PMP is shown in Fig. 1. According to the NMR data, twice the
number of hydrogen atoms were added to the terminal carbon
atoms compared to those added to the inner carbon atoms,
which means this addition reaction followed Markovnikov’s
rule. 1H NMR (300 MHz, CDCl3): d 9.33 (d, J = 9.3 Hz, 6H), 7.52
(m, 12H), 7.23 (t, J = 7.8 Hz, 12H), 7.04 (t, J = 7.3 Hz, 6H), 3.73
(m, 2H), 3.48 (m, 1H), 2.01 (m, 4H), 1.41 (m, 2H), 1.15 (m, 2H),
1.08 (m, 4H), 0.82 (dt, J = 23.1, 7.4 Hz, 6H), 0.49 (m, 4H), 0.00
In order to prepare white light emitting polysiloxane-based
luminescent material, we synthesized
a new functional
polysiloxane, PMP (a, v-N,N9-diphenylmalonamide terminated
polydimethylsiloxane), in which amide groups were employed
instead of ester groups to coordinate with the doped ions, and
benzene rings were included to enhance energy absorption
and coordination.40 A white light-emitting material based on
polysiloxane was obtained with CIE coordinates of (0.32, 0.34).
The photoluminescence of the coordination material was
measured, and the polysiloxane chain’s luminescent contribu-
tion was investigated. Different methods were employed to
reveal the interaction between the ions and the PMP host, as
well as the thermal performances and morphologies of the
materials before and after coordination. Its luminescent
quantum yield was higher than in our previous work,39 which
coincided with our molecular design aim. The underlying
reasons for the enhanced quantum yield are discussed.
(d, J = 2.6 Hz, 108H) (Fig. S6, ESI ). 13C NMR (300 MHz, CDCl3):
3
d 169.39, 137.08, 128.46, 124.33, 119.90, 55.81, 36.75, 21.01,
17.34, 13.07, 0.55 (Fig. S7, ESI ). 29Si NMR (300 MHz, CDCl3): d
3
6.99, 221.27, 221.92 (Fig. S8, ESI ). M = 1462 g mol21
3
n
1
(calculated from H NMR data).
Preparation of Eu3+ and Dy3+ ion-doped PMP (PED)
First, Eu(NO3)3?6H2O (0.6 mmol) and Dy(NO3)3?6H2O (0.2
mmol) were dissolved in 30 mL THF in a flask, together with
0.8 mmol PMP. The solution was kept refluxing at 70 uC for 4
h. The solid obtained after evaporation of the solvent was
thoroughly washed with methanol and water successively, in
order to remove the ions and PMP host which were not
Experimental
Synthesis of a, v-hydride terminated polydimethylsiloxane
(HP)
A mixture of D4 (octamethylcyclotetrasiloxane) and MHMH
(tetramethyldisiloxane) was heated to 65 uC and kept stirring
for 10 h under nitrogen, catalyzed by 5 wt% activated clay. The
activated clay was removed by filtration when the reaction was
complete. The substances with boiling points lower than 100
uC under 1.3 kPa were evaporated. HP was obtained as a
1
colourless liquid. H NMR (300 MHz CDCl3): d 4.81 (s, 1H, O–
Si(CH3)2–H), 0.31 (d, J = 2.76 Hz, 6H, O–Si(CH3)2–H), 0.21 (t, J =
2.98, 2.98 Hz, 30H, O–Si(CH ) –O) (Fig. S1, ESI ). 29Si NMR (300
3
3 2
MHz, CDCl ): d 26.96, 219.92, 221.92 (Fig. S2, ESI ). M = 874
3
3
n
1
g mol21 (calculated from H NMR data).
Synthesis of 2-allyl-N1,N3-diphenylmalonamide (MA)
Diethyl malonate was added into a flask with a three-fold
molar excess of aniline. Xylol (50 mL) was used as solvent. The
mixture was kept refluxing at 120 uC for 5 h. Ethanol was
distilled out of the system as soon as it was produced during
Fig. 1 Synthesis of PMP.
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involved in the coordination.39 The residue was dried under
vacuum at 40 uC. PED was obtained as a yellowish solid. Yield:
87%. The total content of the rare earth ions in the PED
material was analyzed by titration using ethylenediaminete-
traacetic acid disodium salt (EDTA-2Na).42 The content of the
Eu3+ ions was measured by redox titration.43 The ratio of Eu3+
/
Dy3+/PMP was 0.78 : 0.22 : 1. The emission quantum yield of
PED was measured in THF using quinine sulfate in 0.1 M
H2SO4 (w = 0.546) as the standard.44,45 The PED luminescent
material had a quantum yield of 0.3%.
Analytical measurements
Fourier transform infrared (FT-IR) spectra were recorded on a
TENSOR 27 infrared spectrometer using a KBr pellet technique
and measured within the 4000–400 cm21 region at room
temperature. 1H NMR, 13C NMR and 29Si NMR spectra were
recorded on a BRUKER AVANCE-400 spectrometer in deuter-
ated chloroform (CDCl3) without tetramethylsilane (TMS) as
an internal reference. Luminescent emission spectra were
measured with an F-7000 spectrophotometer. The excitation
and emission slits were 5.0 and 2.5 nm, respectively.
Differential scanning calorimetry (DSC) was performed with
a DSC882 differential scanning calorimeter. The samples were
firstly heated to 120 uC to eliminate thermal history. Data were
then collected during the second heating process from 2150
uC up to 200 uC at a rate of 10 uC min21 under nitrogen.
Scanning electronic microscope (SEM) images were obtained
with a JEOL-7600F microscope.
Fig. 2 IR spectra of MA, HP, PMP and PED.
main chain of PMP, so the peak of the CLO bond moved to a
higher wavenumber by 2 cm21 and the peak of the N–H bond
by 21 cm21. The peak shift of the N–H bond was much larger
than that of the CLO bond, which showed the formation and
deformation of hydrogen bond had greater influence on the
N–H bond than the CLO bond. The arrangement of benzene
rings was affected by the Si–O–Si chain. In addition, the
occurrence of isomers of the organic terminal group influ-
enced the arrangement of the benzene rings. As a result, the p–
p stacking of the benzene rings was disturbed and the four
characteristic peaks of the benzene rings moved to higher
wavenumbers (1603, 1547, 1499 and 1445 cm21). After PMP
was coordinated with lanthanide ions, the vibration of the N–
H bond became weaker and its peak moved to 3290 cm21. The
vibration of the CLO bond was also weakened and the peak
moved to 1641 cm21. The coordination formed between the
organic terminal groups of PMP and the lanthanide ions
decreased the electron density of the CLO and N–H bonds.
Comparing the peak shift of the CLO bond with that of the N–
H bond, we know the coordination interactions were mainly
between the O atoms and the lanthanide ions. The p electrons
of the benzene rings were partly involved in the coordination
with the ions. So the peaks belonging to the benzene rings at
1547 and 1445 cm21 in the spectra of PMP moved to 1562 and
1450 cm21 in the spectra of PED (PMP-Eu3+-Dy3+), respectively,
while the other two peaks at 1603 and 1499 cm21 remained
unchanged.
Results and discussion
The IR spectra of MA, HP, PMP and PED are shown in Fig. 2. In
the spectrum of MA (2-allyl-N1,N3-diphenylmalonamide), there
is a peak at 3275 cm21 belonging to the stretching vibration of
the N–H bond. The peak for the stretching vibration of the
CLC–H bond is at 3054 cm21 while the C–C–H bond has peaks
around 2960 cm21. The broad band at 1676 cm21 is composed
of the stretching vibrations of the CLO and CLC bonds. Four
characteristic benzene ring peaks at 1601, 1545, 1495, 1441
cm21 are also observed. a, v-Hydride terminated polydi-
methylsiloxane (HP) has a characteristic peak at 2127 cm21
due to the stretching vibration of the Si–H bond. The peaks at
1096 and 1024 cm21 are due to the stretching vibration of the
Si–O–Si bond. The peak at 1261 cm21 is the symmetric
deformation vibration of the Si–CH3 bond. The peak belonging
to the Si–C–H3 bond is at 2964 cm21. When PMP (a,
v-N,N9-diphenylmalonamide terminated polydimethylsilox-
ane) was obtained by hydrosilylation, the peak at 2127 cm21
in its IR spectrum disappeared. A sharp peak is found in the
spectrum of PMP at 1678 cm21 rather than the broad peak at
1676 cm21 in the spectrum of MA, because of the disappear-
ance of the CLC bonds. Hydrogen bonds equalized the
electron densities of the involved bonds and made their
stretching vibration peaks in the IR spectra move to a lower
wavenumber. Comparing with MA, the formation of the
hydrogen bonds between the CLO bonds and the N–H bonds
was influenced by the steric hindrance caused by the Si–O–Si
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Luminescence excitation spectra of HP, MA, PMP and PED
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temperature (Fig. 4). The most characteristic peaks of the
nitrate salts of Eu3+ and Dy3+ ions were at 395 nm and 352 nm
respectively, which coincided well with the literature.47 When
PED was obtained by coordinating these lanthanide ions with
the PMP host, we did not find the characteristic absorptions of
the original nitrate ions, which meant that the chemical
environment of the ions was totally changed. In other words,
the rare earth ions were coordinated with the host.
As shown in the luminescence excitation spectra, the rare
earth ions could absorb energy by themselves. It is also known
that the coordinated ions can obtain energy through the
antenna effect from the polymers to the ions.48 In this work,
the lanthanide ions were well coordinated with the organic
host. It was of importance to evaluate the antenna effect of the
novel polymeric PMP. Therefore, we chose to research the
luminescence performance of the rare earth ion-coordinated
polysiloxane by excitation at 365 nm, a wavelength that could
excite the PED material effectively and it is also the wavelength
of commonly used UV-light sources.
As shown in Fig. 5, luminescence emission spectra of MA,
HP, PMP and PED were measured by excitation at 365 nm.
Even though HP had little absorption of the energy at 365 nm
in the excitation spectra, its luminescence emission was still
detected when excited at 365 nm. HP showed blue light-
emission in a wide region between 400–550 nm, peaking at 410
nm. MA had an even wider emission in the blue-green range
between 400–650 nm, peaking at 434 nm. The emission of
PMP was a combination of the emissions of HP and MA, with a
wide emission between 400–650 nm that peaked at 441 nm.
The energy that would have been emitted by the PMP between
(Fig. 3) were obtained by monitoring the emission at 485 nm at
room temperature. HP showed no absorption in the region
from 250 nm to 450 nm because both the Si–H terminal bonds
and the Si–O–Si chains have no absorption in this region. MA
had strong absorption between 290 nm and 340 nm, peaking
at 316 nm, corresponding to the pAp* transition of the
benzene rings linked with the amide group.46 The isolated
CLC double bond had little contribution to the absorption of
MA. When PMP was prepared through hydrosilylation, it
showed stronger absorption than MA between 340 nm and 450
nm, which could be attributed to the nAp* transition of the
benzene rings substituted by an N atom with a lone pair,46
while its absorption between 290 nm and 340 nm was almost
the same as that of MA. As was revealed by the IR spectra, the
Si–O–Si main chain of PMP hindered the formation of
hydrogen bonds between the amino groups and the carbonyl
groups. Therefore, more electrons took part in the nAp*
transition and the absorption between 340 nm and 450 nm
was consequently enhanced. The p–p stacking of the benzene
rings was disturbed by the incorporation of the rare earth ions
in the PED material, so the peak of the pAp* transition of the
benzene rings in its spectrum moved to a shorter wavelength
of 290 nm. The coordination formed mainly by the O atoms
and partly by the N atoms decreased the electron density
around the N atoms. Therefore, the absorption of the nAp*
transition of the benzene rings became weaker, as shown in
the spectrum of PED, peaking at 365 nm.
The absorption spectra of Eu(NO3)3 and Dy(NO3)3 were also
detected via monitoring the emission at 485 nm at room
Fig. 3 Luminescence excitation spectra of HP, MA, PMP and PED.
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PED, with coordination between the ions and the PMP,
emission between 400–450 nm was diminished. The residual
part of the emission in the region between 450–600 nm was
the PMP emission mixed with the characteristic emissions of
the Eu3+ and Dy3+ ions and this constituted the total emission
of the PED material.
Narrow width emission bands at 593 and 618 nm assigned
to 5D0A7F1 and 5D0A7F2 transitions of the Eu3+ ions were
found in the emission spectrum of PED. The emission bands
of the Dy3+ ions were mixed together with the residual
emission of the PMP between 435–580 nm. Though they were
not very sharp, we could still find emission bands at 481 and
4
575 nm which could be assigned to the F9/2A6H15/2 and 4F9/2
A6H13/2 transitions of the Dy3+ ions. The emissions of the Eu3+
ions and the emission band of Dy3+ at 575 nm were orange-
red. The residual emission of the PMP host provided a blue-
green colour, together with the emission band at 481 nm of
the Dy3+ ions. Therefore, a white colour emission of PED, with
CIE coordinates of (0.32, 0.34), was prepared from the mixture
of these colourful components.
From the results above, when MA molecules were linked to
both ends of HP, the Si–O–Si chain provided a polymeric
backbone for the phenyl amide groups. The steric hindrance,
caused by the introduction of the polymeric backbone,
impeded the formation of the hydrogen bonds between the
phenyl amide groups, as well as their arrangement. However,
the flexibility of the Si–O bond would have offset the influence
of isomers of PMP. Comprehensively, the Si–O–Si chain gave
birth to the additional absorption of the organic terminal
groups to the energy with wavelengths between 340–450 nm.
Fig. 4 Luminescence excitation spectra of Eu(NO3)3 and Dy(NO3)3.
400–450 nm and a part of that between 450–600 nm was
delivered to the rare earth ions and was then emitted by the
ions as their characteristic emissions. This is the phenomenon
known as the ‘‘antenna effect’’. Therefore, in the spectra of the
Fig. 5 Luminescence emission spectra of MA, HP, PMP and PED.
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In other words, the introduction of the Si–O–Si chain
broadened the energy range that could be absorbed by the
phenyl amide groups. The Si–O–Si chain enabled the electron
transition of the groups at its ends to be excited by lower
energy light.
In the PED material, the flexibility of the Si–O–Si backbone
optimized the coordination between the phenyl amide groups
and the rare earth ions. Additionally, the Si–O–Si chain
benefited the coordination between the ions and the organic
host by weakening the formation of the hydrogen bonds
between the amide groups. The role of the Si–O–Si chain is not
only as host for the organic groups and ions, but also as a
luminescent material. It has blue emission mainly between
400 nm and 500 nm. After the coordination of PMP and the
lanthanide ions, the energy between 400 nm and 450 nm was
delivered to the ions and was transformed into the character-
istic emissions of the ions. The residual emission of the Si–O–
Si chain contributed to the total emission of the PED material
as a blue light component.
Fig. 6 SEM photos of PMP (a, b) and PED (c, d).
In our previous work,39 using ester-terminated polysilox-
anes, the maximum quantum yield was 0.09%. In this work,
we replaced the ester groups with amide groups because the
unpaired electrons of the N atom in an amide group are easier
to polarize than those of the O atom in an ester group.
Consequently, the replacement of an ester group by an amide
should have enhanced the coordination between lanthanide
ions and the terminal groups. The quantum yield of PED was
improved to 0.3%, which was expected based on our molecular
layers were still observed on the edge of the PED particles. But
the layer stacking in PED was less compact than that in PMP
and more decentralised interlayer spaces were observed in the
SEM images of PED. The surface of PED was as smooth as that
of PMP. We did not find phase separation on the surface of
PED, which showed again that the rare earth ions were well-
coordinated with the PMP host.
When macromolecules are formed by PMP molecules
through non-covalent interactions, it is likely that the
design. We also added benzene rings that brought
a
conjugated structure to the host and enhanced the energy
absorption capacity of the organic groups, contributed by
pAp* and nAp* transitions. The benzene rings may also
coordinate to some extent with the rare earth ions through
p-ions interactions. Because of the increased energy absorbed
by the host and the enhanced coordination, more energy was
transformed by the ions and released through their character-
istic emissions, and more residual emissions of the host
contributed to the total emission. Consequently, the quantum
yield of PED (0.3%) was nearly 12 times larger than that of the
EP-Re material (0.023% on average) synthesized in our
previous work.39
The morphology of the lateral surface of PMP was observed
using a scanning electron microscope. Stacked layers were
observed as shown in Fig. 6 a and b. The layers are believed to
be formed by PMP molecules through intralayer hydrogen
bonds between the O, N and H atoms of the amides in the
terminal groups. The layers are then piled up through p–p
interactions between the benzene rings in neighbouring
layers, as well as interlayer hydrogen bonds. When PED was
obtained through the coordination of PMP and the lanthanide
ions, it produced particles (Fig. 6 c and d) rather than the
viscoelasto-plastic material of PMP. The coordination and
steric hindrance of the ions disturbed the formation of non-
covalent forces, as was revealed by the IR and luminescence
spectra, and consequently the order of both the intra and inter
layer structure were rearranged. However, similar stacking
macromolecules behave like
a block polymer with the
connected terminal groups as hard segments and the Si–O–
Si chains as soft segments. Consequently, phase separation
could happen. However, we did not observe phase separation
in the SEM images. The Si–O–Si chain of PMP is composed of
only 10 monomeric units. In the presence of the hydrogen
bonds and other non-covalent forces formed between the
phenyl amide groups, the Si–O–Si chain was too short to act as
a soft segment. As shown in Fig. 6, a plain surface was
observed which meant that the Si–O–Si chain was stretched
tightly between its terminal groups.
For further investigation of the molecular behaviour of the
PMP material, DSC measurements were performed. As shown
in Fig. 7, the glass transition temperature of HP was 2136 uC.
HP formed a crystalline structure at 295 uC and this structure
decomposed at 250 uC. MA molecules were piled up through
hydrogen bonds between the amide groups and p–p interac-
tion between the benzene rings. These non-covalent forces
were broken as the temperature increased to 195 uC and the
orderly structure of MA was consequently destroyed. As was
revealed by the IR spectra, the Si–O–Si main chain of PMP
hindered the formation of the non-covalent interactions
between the phenyl amide groups. Also, the interaction
between the terminal groups disturbed the arrangement of
the Si–O–Si chains. Thus, in the spectrum of PMP, there were
neither exothermic nor endothermic peaks for the formation
or disruption of the Si–O–Si crystalline structure, respectively.
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Fig. 7 DSC spectra of HP, MA, PMP and PED.
The glass transition trend of the PMP material became very
slight in the DSC spectra. The temperature for the disintegra-
tion of the interactions between the phenyl amide groups
moved back to 155 uC. In the PED material, the orderly
structure was further disturbed by the coordination between
the lanthanide ions and the organic groups in PMP. The glass
transition trend of the Si–O–Si chain in PED became even
slighter. The formation of some of the hydrogen bonds was
also influenced by the coordination. The break temperature of
the interaction between the terminal groups was moved to 131
uC. The disruption of the coordination between the organic
groups and the rare earth ions occurred at nearly 200 uC.
was observed in the SEM images. According to the DSC results,
the hydrogen bonds between the terminal groups broke at 130
uC. The disruption of the coordination between the organic
groups and the rare earth ions did not occur until 180 uC.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (No. 21274080 and 20874057),
the Doctor Station Foundation of Chinese Education
Department (No. 20090131120022) and the Key Natural
Science Foundation of Shandong Province of China (No.
ZR2009BZ006 and ZR2011BZ001).
Conclusions
References
White light emission was produced from the composite
material PED (PMP–Eu3+–Dy3+), with
a molar ratio of
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