Influence of molecular weight on the aggregation-induced emission enhancement and spectral stability of vinyl polymers containing the fluorescent 2,4,6-triphenylpyridine pendant groups

Article abstract of DOI:10.1039/c2jm30455d

The effect of molecular weight on the aggregation-induced emission enhancement (AIEE) and the spectral stability of vinyl polymers containing fluorescent 2,4,6-triphenylpyridine (TP) pendant groups was evaluated in this study. The high and low molecular w

Full text of DOI:10.1039/c2jm30455d

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PAPER
Influence of molecular weight on the aggregation-induced emission
enhancement and spectral stability of vinyl polymers containing the
fluorescent 2,4,6-triphenylpyridine pendant groups†
*
Chung Tin Lai and Jin Long Hong
Received 23rd January 2012, Accepted 5th March 2012
DOI: 10.1039/c2jm30455d
The effect of molecular weight on the aggregation-induced emission enhancement (AIEE) and the
spectral stability of vinyl polymers containing fluorescent 2,4,6-triphenylpyridine (TP) pendant groups
was evaluated in this study. The high and low molecular weight (MW) vinyl polymers of PDMPS-H
and -L are deep-blue emitters with the respective high quantum yields of 82.5 and 84.1% in the solid film
state. With high MW (Mn ¼ 525,400 g molꢀ1), PDMPS-H also possesses high spectral stability without
ꢁ
reduction in the emission intensity upon heating to temperatures above 200 C. Solutions of the low
MW (Mn ¼ 37,300 g molꢀ1) PDMPS-L exhibited the normal AIEE effect with continuous emission
gains with increasing aggregation upon nonsolvent inclusion. In contrast, the high MW PDMPS-H
solutions emitted with constant intensity on all solutions with different extent of aggregation. The
emission behavior was then explained by the conformational difference between the PDMPS-L and -H
chains and was theoretically approached by computer simulation.
MEH-PPV chain tends to assemble into aggregated large nano-
Introduction
particles with low emission intensity.42 In the film state, most of
the chain segments of high MW MEH-PPV orient in parallel to
the film plane, in contrast to the nearly random chain orientation
observed in the low MW samples.43 The chain entanglement as
well as thermal and mechanical stabilities generally improved by
the high MW also result in less structural defects like aggregates,
which are said to be detrimental to emission intensity due to the
notorious ACQ effect.1–4,51
In contrast to the aggregation-caused fluorescence quenching
(ACQ)1–4 observed in the traditional organic fluorophores, the
unusual aggregation-induced emission (AIE) or AIE enhance-
ment (AIEE) behavior found in non-coplanar molecules has
drawn lots of attention.5–28 The AIE-operative fluorophores such
as the silole (1-methyl-1,2,3,4,5-pentaphenylsilole) molecule emit
strongly in the aggregated solution and the solid states, albeit it is
nonemissive in the dilute solution state.5–8 In the aggregated state
of silole, the intramolecular rotation (IMR) of the phenyl
peripheries against the central silole core was largely restricted,
leading to reduced nonradiative decay pathways and the
enhanced emission. Due to the advantageous enhanced emissions
in the application solid state, lots of organic and polymeric
materials with the novel AIE or AIEE properties have been
prepared and characterized.9–39,55
No previous effort was made to evaluate the effect of MW on
AIEE properties. Since the MW of the polymer is closely related
to chain mobility and molecular rotation governing the AIE
properties, a low and a high MW vinyl polymers (PDMPS-L and
-H in Scheme 1) containing novel AIEE-active 2,4,6-triphe-
nylpyridine (TP) pendant fluorophore were prepared to assess
the influence of MW on the AIEE-operative emission behavior
and the spectral stability at high temperature. The resultant
PDMPS-H and -L polymers have distinctive MW difference
(with Mn ¼ 525,400 vs. 37,300 g molꢀ1) and were characterized to
be deep-blue emitters with the respective high quantum yields of
82.5 and 84.1% in the solid film states. The high MW PDMPS-H
polymer also exhibits high spectral stability without any emission
The molecular weight (MW) has been shown to be crucial to
the morphology and optoelectronic properties of conjugated
polymers such as MEH-PPV,40–43 polydiacetylene,44 poly-
thiophenes,45–47 and polyfluorenes.48–51 Using the widely-studied
MEH-PPV as example, the short MEH-PPV chain exhibits
higher diffusion coefficient whereas the long chain MEH-PPV
aggregates in the early state. In good solvent, the more extended
ꢁ
reduction upon heating to temperatures higher than 200 C. In
addition, a DTP molecule (cf. Scheme 1) was prepared and used
as model compound to probe the AIEE properties of the poly-
meric analogues. The results also indicated that the PDMPS-H
and -L polymers have varied AIEE emission behaviors, which
were explained in term of conformational difference between the
low and high MW analogues. Theoretical approach for the
Department of Materials and Optoelectronic Science, National Sun
Yat-Sen University, Kaohsiung 80424, Taiwan, Republic of China.
E-mail: jlhong@mail.nsysu.edu.tw; Tel: +886-7-5252000, ext 4065
† Electronic supplementary information (ESI) available: Fig S1–S10. See
DOI: 10.1039/c2jm30455d
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summarized in Table 1. GPC analysis indicated that the starting
polymers PBS-L and -H from the controlled living anionic
polymerizations have narrow PDIs (1.08 for PBS-L and 1.06 for
PBS-H). Further chemical transformations of the t-butoxy
group proceeded to resulted in the final PDMPS products.
The PDMPS-H has a higher Mn (¼ 525,400 g molꢀ1) and
Mw (¼ 583,200 g molꢀ1) than those for PDMPS-L (Mn
¼
37,300 g molꢀ1, Mw ¼ 42,200 g molꢀ1). The large MW difference
between PDMPS-H and -L resulted in the differences in the
corresponding emission and thermal properties, points will be
discussed later.
The efficient transformation from hydroxyl to acetylene
pendant functions52 and the success on the click reaction53,54 can
be demonstrated by 1H NMR spectra. Substitution level of
PDMPS depends on the the starting PVPh and the following
click reaction between APDP and PPS. Degrees of conversions to
acetyolene functions in PPS-L and PPS-H are 99.1% and 98.2,
respectively, which can be calculated from the integration ratios
between the proton Hd (–CH2–ChC–) and protons He,f
(aromatic Hs) in the 1H NMR spectra (Fig. 1). The efficiency of
the click reaction can be also assured from the 1H NMR spectra:
Scheme 1 Preparation of polymeric PPS-L and -H and small-mass
APDP and their further click reaction to yield the desired PDMPS-L
and -H products.
+
the methylene –CH2–N3 resonance (4.25 ppm, proton a in
single-chain conformation was manoeuvred by computer simu-
1
lation, along with it, the H NMR, fluorescence (FL) spectra,
Fig. S3, ESI†) of APDP and the methylene –CH2–ChC– reso-
nance (4.7 ppm, proton d in Fig. 1) of PPS are no longer observed
in the spectra of the PDMPS products (Fig. 2). Instead, the two
methylene resonances (protons c and d) for PDMPSs appear at
5.1 and 5.6 ppm, respectively. Conversions of PDMPS-L and -H
thus evaluated are 99.7 and 99.1, respectively. The aromatic
resonances (protons g–k) for the TP fluorophores in PDMPS-L
and -H are virtually different in shape, comment will be given
later in this discussion.
dynamic light scattering, rheology and viscosity measurements
were all used to evaluate plausible reasons leading to the varied
emissive behaviors and spectral stability between the low and the
high MW PDMPSs.
Results and discussion
Synthesis
Infrared spectra in Fig. S4 (ESI†) can be conveniently used to
demonstrate the success of the functional group transformations.
The large hydroxy stretching band (in the ranges of 3000 to
3600 cmꢀ1) of PVPh-L (or –H) was replaced by the sharp
acetylenic –ChC–H stretching at 3288 cmꢀ1 in the spectrum
of PPS-L (or –H), which indicates that conversion from the
hydroxy –OH to the propynoxy –O–CH2–ChC–H group pro-
ceeded quantitatively. Successful click reaction can be demon-
strated from the result that the azide –N3+ (2100 cmꢀ1) stretching
of APDP and the acetylenic –ChC– (2120 cmꢀ1) stretching of
PPSs were almost absent in the spectra of the final PDMPS
products.
The vinyl polymers PDMPS-L and -H with the AIE-active TP
pendant group were prepared by the facile click reaction between
the azide-functionalized APDP molecule and the polymeric PPSs
(PPS-L and -H) with acetylene pendant groups (Scheme 1). To
have the polymeric PPS-L or -H, the required poly(t-butoxy
styrene)s of low and high molecular weights (PBS-L and -H) were
prepared by the anionic polymerization with controlled mono-
mer/initiator (BV/sec-BuLi) ratio. The t-butoxy groups in the
PBS polymers were then hydrolyzed by HCl to generate the
hydroxyl (–OH) group in the resultant PVPhs, which were then
reacted with propargyl bromide to generate the desired acetylene
pendant functions in PPSs. As another reactant for the click
reaction, the azide-functionalized APDP was prepared from
a three-step reaction procedures starting from the DTP molecule,
which was synthesized from the Chichibabin reaction between
p-tolualdehyde and acetophenone in 1 : 2 molar ratio and was
used as model compound to simulate the emission behavior of
the polymeric PDMPSs. The 4-methyl group in DTP was then
reacted with NBS to yield the desired bromomethyl function,
which under the attack of NaN3 was transformed into the azide
group in the desired APDP compound, of the intermediate
BPDP compound. The chemical structures of all organic inter-
mediates and products were carefully characterized and
confirmed by the 1H NMR, infrared and mass spectroscopy and
elemental analysis.
Table 1 Molecular weights determined from GPC
Sample
PBS-L
PBS-H
PVPh-L
PVPh-H
a
Mn (g molꢀ1
)
16,000
17,300
1.08
209,000
221,600
1.06
10,600
11,300
1.06
153,500
161,200
1.05
b
Mw (g molꢀ1
)
PDIc
Sample
PPS-L
PPS-H
PDMPS-L
PDMPS-H
a
Mn (g molꢀ1
Mw (g molꢀ1
PDIc
)
14,500
15,800
1.09
195,100
208,800
1.07
37,300
42,200
1.13
525,400
583,200
1.11
b
)
a
b
Number-average molecular weight, g molꢀ1
.
Weight-average molecular
Molecular weights of all polymeric materials were evaluated
from the GPC analysis (Fig. S5, ESI†) and the results were
c
. Polydispersity.
weight, g molꢀ1
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Fig. 3 DSC thermograms of (A) low MW and (B) high MW polymers of
PBS, PVPh, PPS and PDMPS.
Emission behavior of DTP, PDMPS-L and -H solutions
The small-mass model DTP was studied first, as shown in
Fig. 4A, dilute (10ꢀ5 M) solution of DTP in THF is essentially
nonemissive but with the gradual inclusion of water nonsolvent
the FL emissions become more intense. The operative AIE effect
can be better illustrated by the increasing quantum yield (FF)
upon increasing water content in the solutions; the summarized
results in Fig. 4B suggest that a maximum FF value of 32% can be
reached when the water content in the solution is 60 vol%,
however, further increase of water content resulted in no emis-
sion gain as seen from the constant FFs for solutions with water
content S60 vol%. The solution FL emission spectra in Fig. 4A
contain a long-wavelength tail extended over 400 nm while in the
Fig. 1 1H NMR spectrum of PBS, PVPh and PPS (DMSO-d6).
Fig. 2 1H NMR spectrum of PDMPS-L and PDMPS-H solutions
(10ꢀ3 M). (DMSO-d6).
The MW difference between the low and high MW polymeric
intermediates and products resulted in the respective low and
high glass transition temperatures (Tgs) shown in the DSC
thermograms (Fig. 3). With higher MWs, the high MW PBS-H,
PVPh-H, PPS-H and PDMPS-H all have higher Tgs than their
low MW analogues. The final PDMPS-H product has a high Tg
of 211 ꢁC, which is 51 ꢁC higher than the resolved 160 ꢁC for the
PDMPS-L counterpart. Except the distinct Tg difference, poly-
mers PDMPS-L and -H also showed varied FL emission
behaviors in the solution and in the solid states.
Fig. 4 (A) FL emission spectra of solid film and dilute (10ꢀ5 M) solution
of DTP in THF/water solvent mixtures of varied compositions, (B) the
summarized solution quantum yield (FF) vs. solution composition (inset:
solid quantum yield), and (C) photographs of DTP in pure THF (left)
and THF/water mixture (90% volume fractions of water) (right) under
illumination with a 365 nm UV lamp.
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solid state a strong emission band (at 372 nm) separated from the
monomer emission was observed. Recently, pyrene-substituted
ethenes (PSEs)55 were reported to exhibit aggregate-enhanced
excimer emission with strong long-wavelength excimer emission
due to the inherent p–p intermolecular interactions and multiple
hydrogen bonds. Similar emission response between PSEs and
DTP molecules indicated that excimer formation is the possible
source for the strong emission at 372 nm. The enhanced excimer
formation in the solid state contributed to the high FF of 73.4%,
comparatively higher than those of the solution samples.
The solution emission behavior of the polymeric PDMPS-L in
THF/water characterized its AIEE effect; as shown in Fig. 5A,
the weakly-emissive solution of PDMPS-L in pure THF gradu-
ally gained emission intensity as the water content in the solution
increased. Although weak in intensity, solution of PDMPS-L in
THF did emit with the discernible monomer and aggregate
emission bands at 350 and 372 nm, respectively. With increasing
water inclusion, the monomer emission merged with the strong
aggregate emission and the large emission gain here is actually
due to the strong aggregate emission, which suggests that
the developed aggregates upon water addition maximized the
observed AIEE effect. Aggregate development resulted in the
bathochromic shift of the aggregate peak from 372 to 383 nm.
Further aggregation on the solid sample resulted in a spectrum
containing mostly the aggregate emission band centered at
a wavelength (389 nm) longer than the aggregate solutions. The
emission enhancement can be also verified from the summarized
FFs in Fig. 5B. The resultant FF values (25–78%) for the
PDMPS-L mixture solutions are comparatively higher than
those (0–32%) of the DTP solutions; therefore, extent of aggre-
gation is expected to be higher in the polymer as compared to the
small-mass DTP. High extent of aggregation on the solid
PDMPS-L also led to further increase of FF to a high value
of 84.1%.
only a small emission difference between 0 and 60 vol% water
solutions (Fig. 6A). Secondly, all emission spectra contained
mainly the long-wavelength aggregate emission with little peak
shifts from 375 to 380 nm. The emission spectrum of the solid
PDMPS-H also resembles the solution ones, which may indicate
the extent of aggregation in the mixture solutions and the solid
sample are quite the same and indeed, the resultant FFs are all in
the vicinity of 82 to 84% (Fig. 6B) for the aggregated solutions
and the solid samples. From the resolved FFs, the PDMPS-H
chains in the mixture solutions have higher degrees of aggrega-
tion than the PDMPS-L chains in solutions; however, little
difference exists in the solid samples in view of their FFs (82.5 vs.
84.1%).
Emissions of dilute solutions (10ꢀ5 M) of DTP, PTMPS-L and
-H in THF at varied reduced temperatures were then measured.
The maximum peak intensity summarized in Fig. 7 indicates the
large emission enhancements of the DTP and the PTMPS-L
solutions with decreasing temperature (before the freezing point
of the mixture solution at –108 ꢁC), which is in distinct contrast
to the small emission gain of the PTMPS-H solution during the
cooling cycle. The insensitivity of the PDMPS-H solution toward
cooling suggests that the long polymer chain of PDMPS-H at
room temperature already imposed high energy barriers for the
molecular rotations of the pendant TP fluorophores and there-
fore, cooling did not much alter the rotation energy barrier
leading to effective nonradiative decay pathways. On the other
hand, the molecular rotations of the TP fluorophores in the
small-mass DTP and the low MW PDMPD-L are considered to
proceed readily due to their less segmental constraints. The high
MW of the PDMPS-H chain should impose high energy barrier
for free molecular rotaion and we will discuss it later. With the
lower rotation barriers, TP fluorophores in DTP and PDMPS-L
underwent active molecular rotations and cooling did exert
effectively in preventing facile molecular rotations leading to
nonradiative decay process. At temperatures <ꢀ108 ꢁC (close to
the freezing point of mixture solutions), serious scattering from
The solution emission of the high MW PDMPS-H is different
from the low MW analogue in two aspects; firstly, there existed
Fig. 5 (A) FL emission spectra of solid film and dilute (10ꢀ5 M) solution
of PDMPS–L in THF/water solvent mixtures of varied compositions, (B)
the summarized solution quantum yield (FF) vs. solution composition
(inset: solid quantum yield), and (C) photographs of PDMPS-L in pure
THF (left) and THF/water mixture (80% volume fraction of water)
(right) under illumination with a 365 nm UV lamp.
Fig. 6 (A) FL emission spectra of solid film and dilute (10ꢀ5 M) solution
of PDMP-H in THF/water solvent mixtures of varied compositions, (B)
the summarized quantum yield (FF) vs. solution composition (inset: solid
quantum yield), and (C) photographs of PDMPS–H in pure THF (left)
and THF/water mixture (60% volume fractions of water) (right) under
illumination with a 365 nm UV lamp.
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Fig. 7 The maximum peak intensity of DTP, PDMPS-L and -H solu-
tions (10ꢀ5 M) in THF at different reduced temperatures.
Fig. 8 Fluorescent decay spectroscopy of PDMPS-L and -H solutions
(10ꢀ5 M) in THF.
the frozen THF media caused the emission reductions in all three
systems.
1
The H NMR spectra in Fig. 2 can be used to evaluate the
Characterizations of the solid PTMPS-L and -H films
relative rotation barrier between the PDMPS-H and the -L
samples. The 1H NMR band shape analysis had been utilized in
the studies of rotation-induced conformational changes in the
AIE-active silole compounds.6 It had been shown that the fast
conformational exchanges caused by the fast intramolecular
rotations upon the single-bond axes give sharp resonance peaks,
whereas the slower exchanges due to the slow rotations broaden
the resonance peaks. Dilute solution (10ꢀ3 M) of PDMPS-L in
DMSO-d6 gave the divided resonance peaks of the aromatic
protons (g–k) in the ranges of 7.3–7.9 ppm, which is essentially
different from the broad aromatic resonance band observed in
spectrum of PDMPS-H. Other than the aromatic resonance
peaks, the rest of the spectra are essentially the same for both
samples, which indicated that only the molecular rotations of the
TP pendant groups are strongly affected by the MW difference.
The 1H NMR spectra in Fig. 2 demonstrated that the molecular
rotations of the TP fluorohores in PDMPS-H are indeed
restricted more seriously than the TPs in PDMPS-L.
Good thermal stability of fluorescent polymers generally requires
better spectral stability at high temperature and the higher Tg
(211 ꢁC) of PDMPS-H means better spectral stability of
PDMPS-H when compared to PDMPS-L with a lower Tg of
160 ꢁC. To demonstrate, the fluorescence intensity of both solid
films was measured at temperatures across the respective glass
transitions (Fig. 9A) and indeed, the high MW PDMPS-H
showed little emission reduction even heated to temperatures
beyond its Tg, which is widely different from the large emission
decrease (to less than 2/3 of the original intensity) observed in the
PDMPS-L sample. Both solid samples are deep-blue emitters
and the PDMPS-H film emitted brightly (cf. the inserted photo)
at a high temperature of 250 ꢁC, which makes it particularly
interesting and the advantageous spectral stability should be due
to its high MW.
To demonstrate, the rheological stability of both film samples
were measured at temperatures across their respective glass
transitions. The complex viscosity vs. temperature plot in Fig. 9B
suggests that the high MW PDMPS-H sample has much higher
viscosity than the low MW PDMPS-L sample. Both samples
exhibited a viscosity drop during the glass transitions; however,
beyond Tg, the PDMPS-H sample still possessed a much higher
The time-resolved fluorescence spectra were then taken to
study the decay behaviors. The decay curves in Fig. 8 clearly
suggest that the PDMPS-H solution has slower decay rate than
the PDMPS-L solution. The resolved data from the decay
curves can be quantitatively fitted with the double–exponential
viscosity than PDMPS-L (5.5 ꢂ 104 vs. 23 Pa s at 250 C). It is
ꢁ
function of y ¼ A1eꢀt /s + A2eꢀt /s , which suggests that the
solution excited states decay through the fast and the slow
pathways with the values of A1 and A2 representative of their
respective fractions and s1 and s2 the respective lifetimes.
Presumably, the fast-decay pathways are due to excited
species in more isolated (monomer) units while the slow-decay
pathways are from paired species in the aggregated regions.
The summarized results in Table 2 suggest that aggregate
decay pathway occupies a higher fraction of 91% for PTPMPS-
H as compared to a less of 63% for PTMPS-L solutions, which
is consistent with the above conclusion that degree of aggre-
gation is high for high MW PTMPS-H but low for low MW
analogue. The average lifetime (s) formulated from s ¼ (A1s1 +
A2s2)/(A1 + A2) is also consistent with the order of PTPMS-H >
PTPMPS-L (7.58 vs. 2.71 ns).
1
1
2
2
envisaged that the numerous entangled chains across the long
chain segment of the high MW PDMPS-H maintained its high
viscosity in the viscous liquid state at high temperatures; in
contrast, the low entangled segments in the PDMPS-L sample
Table 2 Data calculated from the fluorescent decay curves in Fig. 8
Sample
A1 (%)a
A2 (%)a
s1 (ns)a
s2 (ns)a
s (ns)b
PDMPS-L
PDMPS-H
37
9
63
91
0.75
0.73
3.87
8.26
2.71
7.58
a
ꢀt2/s2
Determined from the fitting function of y ¼ A1eꢀt /s + A2e
from the
1
1
fluorescence decay curves in Fig. 8. b Determined from s ¼ (A1s1 + A2s2)/
(A1 + A2).
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their FL intensity response toward repeated heating/cooling
cycles. The results shown in Fig. 9C suggest that both polymers
can be reversibly heated without reducing their emission inten-
sity. Thermal stability of the low and high MW PDMPSs is also
different. The TGA thermograms (Fig. S8, ESI†) indicate that
the polymer PDMPS-H has a higher on-set decomposition
temperature (TD) and a higher residual weight (WR) after heating
ꢁ
ꢁ
to 750 C than the PDMPS-L (TD ¼ 410 vs. 380 C and WR
51 vs. 27 wt%) sample.
¼
Theoretical approach to the single-chain conformers of PDMPS-
L and -H
The single-chain conformations of the PDMPS-L and -H poly-
mers were then studied by computer simulation from the
Molecular Studio package in order to evaluate the plausible
reason for their emission behavior. Primarily, the repeat unit
with minimum-energy needed to be built and was used to
construct the single chains with the respective 100 and 1000
repeat units representative of the low and the high MW
analogues. As illustrated in Fig. 10, the resultant PDMPS-L
conformer after energy-minimization (top) possesses a linear
main-chain with low curvature (cf. the purple main-chain
framework inserted in the top circle). In contrast, the resolved
PDMPS-H conformer mainly contains several intersected loops
connected by the highly-curled intersegments (Fig. 10, bottom).
Here, we described the resultant PDMPS-H conformer as a coil-
like chain for the sake of convenience. Careful inspection for the
Fig. 9 (A) Relative emission intensity and (B) rheogram of complex
viscosity for samples PDMPS-L and -H films measured at high temper-
atures. (c) The fluorescence modulation spectrum shows the thermo-
reversibility of the FL intensity (heating rate: 2 ꢁC minꢀ1).
are incapable of keeping up a reasonable viscosity to maintain
mechanical integrity in the flow state. Here, the restricted
molecular rotations of the TP fluorophores imposed by the
entangled segments of PDMPS-H sample are supposed to
function well to exert efficient AIEE-oriented emission in the
viscous state; however, the low viscosity of the PDMPS-L chain
at high temperatures led to large emission reduction due to the
free molecular rotations of the less-entangled chains at high
temperatures. The thermo-reversibility of the FL/temperature
response of the PDMPS-L and -H samples can be evaluated from
Fig. 10 Single-chain conformers of PDMPS-L (top) and PDMPS-H
(bottom) simulated from MS.
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more linear PDMPS-L chain suggested that most of the fluor-
phoric TP units in the adjacent pendant groups are actually
pointed away from each other and become spatially isolated
from the vicinal TP fluorophores, which are the monomer units
responsible for the weak emission in the dilute (10ꢀ5 M) solution
of PDMPS-L due to the lack of aggregated TPs to exert AIE-
operative emission. For the coil-like PDMPS-H chain, the
highly-curled regions and the intersected loops contain abundant
sources of intimately-packed 1,3-TP pairs, which contributed to
the excimer emission upon photo-irradiating the dilute (10ꢀ5 M)
solution of PDMPS-H in THF.
solutions). The volume shrinkage which occurred in the
PDMPS-L solution led to the bathochromic shift of the aggre-
gate emission and the emission enhancement observed in
Fig. 5A; suggesting that the shrinkage of the aggregated nano-
particles forced the interior aromatic TP fluorophores to pack in
a more coplanar fashion, which extended conjugation and the
bathochromic shift of the long-wavelength aggregation emissions
with increasing water inclusion. The steric crowdedness imposed
by the volume shrinkage also restrains the free rotation of the
aromatic rings and blocks the nonradiative decay channels,
leading to the observed emission enhancements in Fig. 5A. The
large aggregated particles formed in the PDMPS-H mixture
solutions allows little changes of the geometrical arrangements of
the 1,3-TP pairs in the aggregated states. The invariant 1,3-TP
pairs responsible for the excimer emission are considered to
persist in the solution, aggregate and solid states as judged by the
similar emission spectra illustrated in Fig. 6A.
When aggregates formed in the mixture solutions, intermo-
lecular interactions for the linear PDMPS-L and the coil-like
PDMPS-H chains is schematically illustrated in Scheme 2. In the
aggregated domains, the intimate contacts among the linear
PDMPS-L chains proceeded readily and the densely-packing of
the TP fluorophores within the compact aggregates are
conceivable; thus, aggregate emission increased (cf. Fig. 5A)
when water was included to generate aggregates containing the
densely-packed fluorophores. In contrast, few intimately-con-
tacted TP pairs can be further gained for the intermolecular
approaches of the large PDMPS-H coils due to the geometrical
restraint and in this case, coil aggregates with loose intermolec-
ular contacts may be yielded. The little intermolecular associa-
tion may account for the small emission variations for the
different mixture solutions of PDMPS-H (cf. Fig. 6A). With the
inclusion of water, aggregated nanoparticles with varied hydro-
dynamic volumes formed. The DLS analysis (Fig. S9, ESI†) on
the mixture solutions suggests that the aggregated nanoparticles
generated for the mixture solutions of PDMPS-H are compara-
tively larger than the nanoparticles formed in the PDMPS-L
solutions, a result possibly correlated with the loose and the
dense geometrical arrangements inside the aggregated nano-
particles of the PDMPS-H and -L solutions, respectively. With
the increasing water content from 20 to 80 vol%, the average
hydrodynamic diameter (Dh) of the PDMPS-L nanoparticles
evaluated from the mixture solutions decreased from 136 to
71 nm, which are much smaller than those found in the PDMPS-
H solutions (Dh ¼ 341–185 nm from 10 to 60 vol% water
Conclusions
The high and low MW PDMPS-H and -L polymers with novel
AIE-active TP pendant groups were successfully prepared
through the facile click reaction between the azide-functionalized
APDP and vinyl polymer with the acetylene pendant groups.
Both the solid PDMPS-L and -H films are good deep-blue
emitters with the high FF values of 84.1 and 82.5%, respectively.
ꢁ
With high MW, the PDMPS-H polymer has a high Tg (211 C)
and enhanced spectral stability withoutꢁany emission reduction
after heating to temperature above 200 C.
The simulated single-chain conformer of PDMPS-L contains
linear framework with most of the pendant TP fluorophores
isolated to each other, which are responsible for the weak emis-
sion in dilute solution. With the inclusion of nonsolvent water,
the intimate intermolecular contacts of the linear chains facilitate
formations of densely-packed TP aggregates, leading to large
emission enhancement. In contrast, despite the single coil-like
PDMPS-H chain containing more aggregated domains, inter-
molecular approaches among the coil-like chains gained little
aggregated TP pairs, resulting in the constant emission intensity
with further water inclusion.
Experimental
Materials
Reagent grade acetophenone, p-tolualdehyde, ammonium
acetate, sodium sulfite (Na2SO3), sodium azide (NaN3), sec-
butyllithium solution (1.3 M in cyclohexane), 4-tert-butoxystyr-
ene (BV), propargyl bromide solution (80 wt% in toluene),
alumina oxide, acetic acid and dioxane were purchased from
Aldrich Chemical Company and used directly without purifica-
tion. Benzoyl peroxide (BPO; Acros) and N-bromosuccinimide
(NBS; Aldrich) were recrystallized from chloroform/methanol
and acetone, respectively. CuBr (98%, Aldrich) was stirred
overnight in acetic acid, filtered and washed with ethanol and
diethyl ether before dried in vacuo. THF was refluxed over
sodium/benzophenone under nitrogen for more than 2–3 days
before distillation to use. N,N-dimethylformamide (DMF;
Aldrich) and dichloromethane (DCM; Aldrich) were refluxed
over CaH2 under nitrogen for 5 h before distillation for use.
Scheme 2 Intermolecular approaches within the aggregated nano-
particles for the more linear PDMPS-L and the coil-like PDMPS-H
chains.
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Characterization
to 0 ꢁC, the precipitates were filtered, washed with methanol, and
dried in vacuo to afford pale yellow solid. After recrystallization
from methanol three times, the fluffy and yellowish needle
product (5.38 g, 34% yield) was obtained. IR (KBr pellet, cmꢀ1):
3025, 2922, 2855, 1598, 1543, 1399, 1241, 1181, 1115, 1076, 1027,
877, 817, 771, 737, 692, 568. 1H NMR (500 MHz, CDCl3): d 2.45
(s, 3H, Ha), 7.34 (d, 2H, Hb), 7.45 (t, 2H, Hc), 7.52 (t, 4H, Hd),
7.66 (d, 2H, He), 7.88 (s, 2H, Hf), 8.21 (d, 4H, Hg) (Fig. S1, ESI†).
MS, m/z: calcd for C24H19N, 321.15; found, 321.04 (M+).
Anal. Calcd for C24H19N: C, 89.68; H, 5.96; N, 4.36. Found: C,
89.59; H, 6.12; N, 4.28.
1H NMR spectra were recorded on a Varian VXR-500 MHz
instrument (resonance frequency of 500 MHz) operated in the
Fourier transform mode with CDCl3 or (CD3)2SO as the solvent.
A VG Quattro GC-MS/MS/DS instrument was used to deter-
mine the molar mass of the organic molecules. The sample was
charged into rapidly moving gas and converted into ions, which
can be separated based on their mass-to-charge ratios (m/z).
Molecular weight and molecular weight distribution of polymers
were determined from GPC using a Waters 510 HPLC model
equipped with a 410 differential refractometer, an UV detector
ꢀ
and three Ultrastyragel columns (100, 500, and 1000 A) con-
Preparation of 4-(4-(bromomethyl)phenyl)-2,6-diphenylpyridine
(BPDP). Solution mixtures of DTP (4 g, 12.45 mmol), NBS
(2.31 g, 13 mmol) and BPO (3.15 g, 13 mmol) in CCl4 (20 mL)
were stirred under nitrogen in a two-necked flask to become
nected in series. Polymer solution was eluted by THF or DMF
with a flow rate of 0.6 mL minꢀ1. A set of monodisperse poly-
styrene standards covering molecular weight range of 103–106 g
molꢀ1 was used for the molecular weight calibration. The glass
transition temperatures (Tg) of the polymers were obtained from
ꢁ
homogeneous before heated at 80 C for 24 h. After cooling to
room temperature, the succinimide side produced was removed
by filtration. Aqueous Na2SO3 (ꢃ 20 mL) was then added to the
filtrate and the whole solution was stirred vigorously in order to
reduce excess bromine. The solution was extracted with chloro-
form (15 mL) and washed with water (40 mL). The organic layer
was collected and dried over MgSO4. All volatiles were then
removed under reduced pressure. Column chromatography
(hexane eluent) was applied to yield the yellow oily product
(1.8 g; 36.1% yield). IR (KBr pellet, cmꢀ1): 3061, 3033, 2955,
2926, 2854, 1599, 1546, 1451, 1421, 1392, 1229, 1204, 1179, 1073,
1025, 920, 879, 836, 774, 739, 691, 604, 504. 1H NMR (500 MHz,
CDCl3): d 4.35 (s, 2H, Ha), 7.34 (d, 2H, Hb), 7.45 (t, 2H, Hc), 7.52
(t, 4H, Hd), 7.66 (d, 2H, He), 7.88 (s, 2H, Hf), 8.21 (d, 4H, Hg)
(Fig. S2, ESI†). MS, m/z: calcd for C24H18BrN, 399.06; found,
399.29 (M+). Anal. Calcd for C24H18BrN: C, 72.01; H, 4.53; Br,
19.96; N, 3.50. Found: C, 72.30; H, 4.00; Br, 20.21; N, 3.48.
a TA Q-20 DSC calorimeter with a scan rate of 20 ꢁC minꢀ1
.
FT-IR spectra were recorded on a Nicolet IR-200 spectrometer.
Sampleꢁsolution in THF was dropped on a KBr pellet and dried
at 100 C under vacuum to prepare solid samples for analysis.
The UV-vis absorption spectra were recorded with an Ocean
Optics DT 1000 CE 376 spectrophotometer. The FL emission
spectra were obtained from a LabGuide X350 fluorescence
spectrophotometer using a 450W Xe lamp as the continuous light
source. Solution quantum yield (FF) in solvent mixture of varied
compositions was determined by comparison with a quinine
sulfate standard solution (10ꢀ5 M in 0.1 N H2SO4, FF ¼ 55%).
Integrating sphere was used to measure the quantum yields of the
solid films. Particle sizes of polymer aggregates in solvent
mixtures were analyzed by dynamic light scattering (DLS) using
a Brookhaven 90 plus spectrometer equipped with a temperature
controller. An argon ion laser operating at 658 nm was used as
light source. The rheological behavior of the PDMPS-L and
PDMPS-H were studied using TA Instruments AR 2000ex
Rheometer. The experiments were operated under a fixed oscil-
lation frequency of 10 Hz at different elevated temperatures with
a scan rate of 2 ꢁC minꢀ1. Single-chain conformations of PDMPS
polymers were formulated from the Materials Studio (MS)
commercial software of Accelrys Inc. The repeat unit with the
geometry optimization was primarily built by Gaussian MS
Program. The polymeric chains with the respective 100 and 1000
repeat units were then constructed to represent the low and the
high MW PDMPS-L and -H, respectively, The Smart Minimizer
incorporated in the Discover MS Program33 was used to
broadcast the minimum-energy conformer of PDMPS-L and -H.
Preparation of 4-(4-(azidomethyl)phenyl)-2,6-diphenylpyridine
(APDP). Suspension of BPDP (1 g, 2.5 mmoꢁl) and NaN3 (0.2 g,
3 mmol) in DMF (20 mL) was heated at 80 C for 24 h. Excess
solvent was then removed by vacuum distillation at elevated
temperature. The resultant solid was dissolved in 30 mL
dichloromethane and washed with 150 mL of saturated aq. NaCl
solution twice. The organic layer was then dried over MgSO4
before concentrated to obtain crude mixture. Final product
(0.1 g; 11% yield) was obtained after column chromatography
(hexane eluent). IR (KBr pellet, cmꢀ1): 3061, 3035, 2958, 2925,
2851, 2099, 1596, 1543, 1391, 1247, 1185, 1078, 1025, 835, 769,
737, 691 (Fig. S4, ESI†). 1H NMR (500 MHz, CDCl3): d 4.24 (s,
2H, Ha), 7.34 (d, 2H, Hb), 7.45 (t, 2H, Hc), 7.52 (t, 4H, Hd), 7.66
(d, 2H, He), 7.88 (s, 2H, Hf), 8.21 (d, 4H, Hg) (Fig. S3, ESI†). MS,
m/z: calcd for C24H18N4, 362.15; found, 362.11 (M+). Anal.
Calcd for C24H18N4: C, 79.54; H, 5.01; N, 15.46. Found: C,
79.81; H, 4.69; N, 15.49.
Syntheses of small molecules and polymers
Catalyst tris(2-dimethylaminoethyl)amine (Me6-TREN)31 for
Click reaction was prepared by the reported procedures. Organic
molecules and polymers shown in Scheme 1 were prepared
according to the detailed procedures below.
Preparation of PBS-L and -H by anionic polymerization. A
PBS-L polymer was synthesized by living anionic polymerization
under an inert atmosphere in THF (500 mL) using sec-butyl-
lithium (0.22 mL, 0.28 mmol; 1.3 M in cyclohexane) as the
initiator at ꢀ78 ꢁC. The 4-tert-butoxystyrene (BV; 5 g) monomer
was then injected via syringe and polymerization was allowed to
proceed at ꢀ78 ꢁC for 2 h before warmed up to room
Preparation of 2,6-diphenyl-4-p-tolylpyridine (DTP). A mixture
of acetophenone (12 g, 99.87 mmol), p-tolualdehyde (6 g, 49.93
mmol), ammonium acetate (60 g, 0.78 mol) and acetic acid
(100 mL) was heated and reacted at 115 ꢁC for 24 h. After cooling
This journal is ª The Royal Society of Chemistry 2012
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temperature and terminated with methanol. The solid precipi-
tates were filtered and washed with methanol three times before
vacuum drying to yield the final polymer as blond yellow powder
(4.5 g; 90% yield). The synthesis of PBS-H was operated with the
same procedures as for PBS-L but different recipes (sec-butyl-
lithium ¼ 0.02 ml (0.026 mmol) and BV ¼ 5 g) was used. PBS-L:
Tg ¼ 96 ꢁC (Fig. 3). IR (KBr pellet, cmꢀ1) 2976, 2927, 1604, 1502,
(0.25 g, 0.69 mmol) and PPS-L (0.1 g, 0.69 mmol). A solution of
Me6-TREN (46 mg; 0.2 mmol) in degassed DMF (5 mL) was
then introduced and the resultant transparent solution was
heated at 80 ꢁC under argon atmosphere for 48 h. When the
mixture was cooled to room temperature, DMF was distilled off
under reduced pressure. The residue was then diluted with THF
before passing through an alumina column to remove the copper
catalyst. The solid product was then precipitated from methanol.
Subsequent dissolution/precipitation procedures by THF/meth-
anol (v/v ¼ 1.5/8.5) were repeated twice before vacuum drying to
yield the final polymer as yellow powder (PDMPS-L, 0.34 g, 95%
yield). The synthesis of PDMPS-H (0.315 g, 88% yield) followed
the same procedures. PDMPS-L: Tg ¼ 160 ꢁC (Fig. 3). IR (KBr
pellet, cmꢀ1) 3059, 3034, 2922, 2852, 1600, 1543, 1503, 1454,
1394, 1226, 1031, 832, 775, 699 (Fig. S4A, ESI†). 1H NMR (500
MHz, CDCl3): d 0.40–2.28 (b, 3H, Ha, Hb), 5.01–5.23 (b, 2H,
Hc), 5.50–5.70 (b, 2H, Hd), 6.23–6.93 (b, 4H, He, Hf) 7.28–7.40
(b, 2H, Hg) 7.40–7.60 (b, 6H, Hh, Hi) 7.60–7.75 (b, 2H, Hj) 7.81–
7.95 (b, 2H, Hk) 8.12–8.36 (b, 5H, Hl, Hm) (Fig. 2). PDMPS-H:
Tg ¼ 211 ꢁC (Fig. 3). IR (KBr pellet, cmꢀ1) 3057, 3034, 2922,
2855, 1600, 1545, 1509, 1456, 1394, 1224, 1028, 828, 775, 694
1
1446, 1239, 1165, 895, 848, 550. H NMR (500 MHz, CDCl3):
d 0.55–2.48 (b, 12H, Ha, Hb, Hc), 5.91–6.44 (b, 2H, Hd), 6.45–
6.86 (b, 2H, He) (Fig. 1). PBS-H: Tg ¼ 114 ꢁC (Fig. 3). IR (KBr
pellet, cmꢀ1) 2976, 2927, 1606, 1505, 1455, 1377, 1242, 1167, 900,
853. 1H NMR (500 MHz, CDCl3): d 0.55–2.54 (b, 12H, Ha, Hb,
Hc), 5.96–6.89 (b, 4H, Hd, He) (Fig. 1).
Preparation of PVPh-L and -H. Hydrolysis of polymer PBS
afforded the desired poly(4-vinylphenol) (PVPh). The PBS-L
(3.5 g, 19.86 mmol) was dissolved in dioxane (50 mL) before the
introduction of aq. HCl (37 wt%, 2 mL) solution. The mixture
was stirred at 80 ꢁC overnight and the resultant product was
precipitated from methanol/water (v/v ¼ 2/8) mixture. After
neutralization with aq. NaOH (10 wt%) solution, the resultant
product was filtered off. Repeated dissolution and precipitation
by THF and methanol/water solvents were then conducted to
yield crude product for further Soxhlet extraction with water for
3 days. Final products of PVPh-L (2.1 g, 88%) and -H (2.25 g,
94% yield) were obtained after vacuum drying at 80 ꢁC. PVPh-L:
Tg ¼ 156 ꢁC (Fig. 3). IR (KBr pellet, cmꢀ1) 3689–3072, 3021,
2921, 2847, 1607, 1514, 1445, 1364, 1229, 1168, 1104, 1013, 828,
552 (Fig. S4A, ESI†). 1H NMR (500 MHz, CDCl3): d 0.88–2.11
(b, 3H, Ha, Hb), 6.09–6.74 (b,ꢁ4H, Hc, Hd), 8.85–9.20 (b, 1H, He)
1
(Fig. S4B, ESI†). H NMR (500 MHz, CDCl3): d 0.39–2.30 (b,
3H, Ha, Hb), 4.97–5.27 (b, 2H, Hc), 5.42–5.77 (b, 2H, Hd), 6.15–
7.03 (b, 4H, He, Hf) 7.03–8.01 (b, 12H, Hg, Hh, Hi, Hj, Hk) 8.01–
8.44 (b, 5H, Hl, Hm) (Fig. 2).
Acknowledgements
We appreciate the financial support from the National Science
Council, Taiwan, Republic of China, under Contract No. NSC
100-2221-E-110-045.
(Fig. 1). PVPh-H: Tg ¼ 191 C (Fig. 3). IR (KBr pellet, cmꢀ1
)
3687–3083, 3022, 2921, 2847, 1606, 1512, 1443, 1361, 1230, 1173,
1
1108, 828, 545 (Fig. S4B, ESI†). H NMR (500 MHz, CDCl3):
d 0.77–2.22 (b, 3H, Ha, Hb), 5.88–6.96 (b, 4H, Hc, Hd), 8.72–9.27
Notes and references
(b, 1H, He) (Fig. 1).
1 S. W. Thomas III, G. D. Joly and T. M. Swager, Chem. Rev., 2007,
107, 1339.
Preparation of PPS-L and -H. Propargyl bromide (1.78 g, 15
mmol) was added to a mixture of PVPh-L (1.5 g, 12.48 mmol)
and K2CO3 (2.07 g, 15 mmol) in dry DMF (40 mL) and stirred at
65 ꢁC for 24 h under nitrogen atmosphere. The resultant mixtures
were precipitated by methanol/water (v/v ¼ 5/5) and the
precipitate was filtered and dried under vacuum at 80 ꢁC to
obtain PPS-L (1.87 g, 95% yield). The synthesis of PPS-H (1.63 g,
83% yield) followed the same procedures. PPS-L: Tg ¼ 64 ꢁC
(Fig. 3). IR (KBr pellet, cmꢀ1) 3290, 3030, 2924, 2856, 1609, 1581,
1511, 1452, 1373, 1304, 1264, 1220, 1178, 1114, 1032, 923, 826,
€
2 A. Dreuw, J. Ploner, L. Lorenz, J. Wachtveitl, J. E. Djanhan,
J. Bruning, T. Metz, M. Bolte and M. U. Schmidt, Angew. Chem.,
Int. Ed., 2005, 44, 7783.
3 C.-T. Chen, Chem. Mater., 2004, 16, 4389.
4 G. Qian, Z. Zhong, M. Luo, D. Yu, Z. Zhang, Z. Y. Wang and
D. Ma, Adv. Mater., 2009, 21, 111.
5 J. Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu, H. S. Kwok,
X. Zhan, Y. Liu, D. Zhu and B. Z. Tang, Chem. Commun., 2001,
1740.
6 J. Chen, C. C. W. Law, J. W. Y. Lam, Y. Dong, S. M. F. Lo,
I. D. Williams, D. Zhu and B. Z. Tang, Chem. Mater., 2003, 15, 1535.
7 H. J. Tracy, J. L. Mullin, W. T. Klooster, J. A. Martin, J. Haug,
S. Wallace, I. Rudloe and K. Watts, Inorg. Chem., 2005, 44, 2003.
€
1
681, 646, 554 (Fig. S4A, ESI†). H NMR (500 MHz, CDCl3):
€
8 Z. Li, Y. Q. Dong, J. W. Y. Lam, J. Sun, A. Qin, M. Haubler,
d 0.34–2.25 (b, 3H, Ha, Hb), 3.37–3.59 (b, 1H, Hc), 4.57–4.80 (b,
ꢁ
(Fig. 3). IR (KBr pellet, cmꢀ1) 3289, 3034, 2924, 2858, 1609, 1508,
Y. P. Dong, H. H. Y. Sung, I. D. Williams, H. S. Kwok and
B. Z. Tang, Adv. Funct. Mater., 2009, 19, 905.
9 Y. Hong, J. W. Y. Lama and B. Z. Tang, Chem. Commun., 2009, 4332.
10 H. Li, Z. Chi, B. Xu, X. Zhang, X. Li, S. Liu, Y. Zhang and J. Xu, J.
Mater. Chem., 2011, 21, 3760.
11 T. He, X. T. Tao, J. X. Yang, D. Guo, H. B. Xia, J. Jia and
M. H. Jiang, Chem. Commun., 2011, 47, 2907.
12 B. Xu, Z. Chi, Z. Yang, J. Chen, S. Deng, H. Li, X. Li, Y. Zhang,
N. Xu and J. Xu, J. Mater. Chem., 2010, 20, 4135.
2H, Hd), 6.21–7.06 (b, 4H, He, Hf) (Fig. 1). PPS-H: Tg ¼ 83 C
1451, 1372, 1300, 1225, 1180, 1114, 1029, 925, 831, 679, 647, 552
1
(Fig. S4B, ESI†). H NMR (500 MHz, CDCl3): d 0.32–2.27 (b,
3H, Ha, Hb), 3.36–3.62 (b, 1H, Hc), 4.48–4.88 (b, 2H, Hd), 6.05–
7.21 (b, 4H, He, Hf) (Fig. 1).
13 Z. Zhao, S. Chen, J. W. Y. Lam, P. Lu, Y. Zhong, K. S. Wong,
H. S. Kwok and B. Z. Tang, Chem. Commun., 2010, 46, 2221.
14 W. Wang, T. Lin, M. Wang, T. X. Liu, L. Ren, D. Chen and
S. Huang, J. Phys. Chem. B, 2010, 114, 5983.
15 W. Z. Yuan, P. Lu, S. Chen, J. W. Y. Lam, Z. Wang, Y. Liu,
H. S. Kwok, Y. Ma and B. Z. Tang, Adv. Mater., 2010, 22, 1.
Preparations of PDMPS-L and -H (click reaction). A typical
procedure for the click reaction is as follows: DMF (10 mL) was
placed in a three-neck flask and degassed by bubbling argon gas
for 1.5 h before the addition of CuBr (20 mg, 0.14 mmol), APDP
9554 | J. Mater. Chem., 2012, 22, 9546–9555
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View Article Online
16 W. C. Wu, C. Y. Chen, Y. Tian, S. H. Jang, Y. Hong, Y. Liu, R. Hu,
B. Z. Tang, Y. T. Lee, C. T. Chen, W. C. Chen and A. K. Y. Jen, Adv.
Funct. Mater., 2010, 20, 1413.
36 R.H.Chien,C.T.LaiandJ.L.Hong,J. Phys. Chem. C, 2011, 115, 12358.
37 B. Xu, X. Wu, H. Li, H. Tong and L. Wang, Macromolecules, 2011,
44, 5089.
17 P. P. Kapadia, J. C. Widen, M. A. Magnus, D. C. Swenson and
F. C. Pigge, Tetrahedron Lett., 2011, 52, 2519.
38 R. H. Chien, C. T. Lai and J. L. Hong, J. Phys. Chem. C, 2011, 115,
20732.
18 D. S. An, B. K. Lee, J. S. Lee, Y. S. Park, H. S. Song and S. Y. Park, J.
Am. Chem. Soc., 2004, 126, 10232.
39 W. Z. Yuan, Z. Q. Yu, Y. Tang, J. W. Y. Lam, N. Xie, P. Lu,
E. Q. Chen and B. Z. Tang, Macromolecules, 2011, 44, 9618.
€
40 K. Koynov, A. Bahtiar, T. Ahn, C. Bubeck and H. –H. Horhold,
Appl. Phys. Lett., 2004, 84, 3792.
41 S. Shaked, S. Tal, Y. Roichman, A. Razin, S. Xiao, Y. Eichen and
N. Tessler, Adv. Mater., 2003, 15, 913.
42 R. Traiphol, R. Potai, N. Charoenthai, T. Srikhirin, T. Kerdcharoen
and T. Osotchan, J. Polym. Sci., Part B: Polym. Phys., 2010, 48, 894.
€
43 K. Koynov, A. Bahtiar, T. Ahn, R. M. Cordeiro, H.-H. Horhold and
C. Bubeck, Macromolecules, 2006, 39, 8692.
19 Z. Zhao, P. Lu, J. W. Y. Lam, Z. Wang, C. Y. K. Chan,
H. H. Y. Sung, I. D. Williams, Y. Ma and B. Z. Tang, Chem. Sci.,
2011, 2, 672.
20 J. Wang, J. Mei, W. Yuan, P. Lu, A. Qin, J. Sun, Y. Ma and
B. Z. Tang, J. Mater. Chem., 2011, 21, 4056.
21 Y. Liu, C. Deng, L. Tang, A. Qin, R. Hu, J. Z. Sun and B. Z. Tang, J.
Am. Chem. Soc., 2011, 133, 660.
22 P. S. Salini, A. P. Thomas, R. Sabarinathan, S. Ramakrishnan,
K. C. G. Sreedevi, M. L. P. Reddy and A. Srinivasan, Chem.–Eur.
J., 2011, 17, 6598.
44 D. Grando, G. P. Banfi, D. Fortusini, R. Ricceri and S. Sottini, Synth.
Met., 2003, 139, 863.
23 X. Zhang, Z. Chi, H. Li, B. Xu, X. Li, S. Liu, Y. Zhang and J. Xu, J.
Mater. Chem., 2011, 21, 1788.
45 R. J. Kline, M. D. McGehee, E. N. Kadnikova, J. Liu and
J. M. J. Frechet, Adv. Mater., 2003, 15, 1519.
24 B. Wang, Y. Wang, J. Hua, Y. Jiang, J. Huang, S. Qian and H. Tian,
Chem.–Eur. J., 2011, 17, 2647.
25 Z. Zhao, D. Liu, F. Mahtab, L. Xin, Z. Shen, Y. Yu, C. Y. K. Chan,
P. Lu, J. W. Y. Lam, H. H. Y. Sung, I. D. Williams, B. Yang, Y. Ma
and B. Z. Tang, Chem.–Eur. J., 2011, 17, 5998.
46 A. Zen, J. Pflaum, S. Hirschmann, W. Zhuang, F. Jaiser,
U. Asawapirom, J. P. Rabe, U. Scherf and D. Neher, Adv. Funct.
Mater., 2004, 14, 757.
47 A. Zen, M. Saphiannikova, D. Neher, J. Grenzer, S. Grigorian,
U. Pietsch, U. Asawapirom, S. Janietz, U. Scherf, I. Lieberwirth
and G. Wegner, Macromolecules, 2006, 39, 2162.
48 C. Donley, J. Zaumseil, J. Andreasen, M. Nielsen, H. Sirringhaus,
R. Friend and J. Kim, J. Am. Chem. Soc., 2005, 127, 12890.
49 M. Knaapila, B. P. Lyons, T. P. A. Hase, C. Pearson, M. C. Petty,
L. Bouchenoire, P. Thompson, R. Serimaa, M. Torkkeli and
A. P. Monkman, Adv. Funct. Mater., 2005, 15, 1517.
ꢁ
ꢁ
26 A. Perez, J. L. Serrano, T. Sierra, A. Ballesteros, D. d. Saa and
J. Barluenga, J. Am. Chem. Soc., 2011, 133, 8110.
27 T. L. Bandrowsky, J. B. Carroll and J. B. Wilking, Organometallics,
2011, 30, 3559.
28 H. H. Lin, Y. C. Chan, J. W. Chen and C. C. Chang, J. Mater. Chem.,
2011, 21, 3170.
29 K. Kokado and Y. Chujo, Macromolecules, 2009, 42, 1418.
30 R. H. Chien, C. T. Lai and J. L. Hong, J. Phys. Chem. C, 2011, 115,
5958.
50 M. Knaapila, R. Stepanyan, B. P. Lyons, M. Torkkeli, T. P. A. Hase,
€
R. Serimaa, R. Guntner, O. H. Seeck, U. Scherf and A. P. Monkman,
Macromolecules, 2005, 38, 2744.
31 C. T. Lai, R. H. Chien, S. W. Kuo and J. L. Hong, Macromolecules,
2011, 44, 6546.
51 K. Hosoi, T. Mori, T. Mizutani, T. Yamamoto and N. Kitamura,
Thin Solid Films, 2003, 438–439, 201.
}
32 J. Liu, Y. Zhong, J. W. Y. Lam, P. Lu, Y. Hong, Y. Yu, Y. Yue,
M. Faisal, H. H. Y. Sung, I. D. Williams, K. S. Wong and
B. Z. Tang, Macromolecules, 2010, 43, 4921.
33 C. T. Lai and J. L. Hong, J. Phys. Chem. B, 2010, 114, 10302.
34 A. Qin, J. W. Y. Lam, L. Tang, C. K. W. Jim, H. Zhao, J. Sun and
B. Z. Tang, Macromolecules, 2009, 42, 1421.
52 A. D. Thomsen, E. Malmstrom and S. Hvilsted, J. Polym. Sci., Part
A: Polym. Chem., 2006, 44, 6360.
53 V. V. Rostovtsev, L. G. Green, V. V. Fokin and K. B. Sharpless,
Angew. Chem., Int. Ed., 2002, 41, 2596.
54 C. W. Tornoe, C. Christensen and M. Meldal, J. Org. Chem., 2002,
67, 3057.
€
35 W. Z. Yuan, A. Qin, J. W. Y. Lam, J. Z. Sun, Y. Dong, M. Haussler,
J. Liu, H. P. Xu, Q. Zheng and B. Z. Tang, Macromolecules, 2007, 40,
55 Z. Zhao, S. Chen, J. W. Y. Lam, Z. Wang, P. Lu, F. Mahtab,
H. H. Y. Sung, I. D. Williams, Y. Ma, H. S. Kwok and B. Z. Tang,
J. Mater. Chem., 2011, 21, 7210.
3159.
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