A new strategy to access polymers with aggregation-induced emission characteristics

Article abstract of DOI:10.1021/ma500985j

A highly efficient strategy for synthesizing the first biocompatible polyesters with AIE characteristics has been established via immortal ring-opening polymerizations of cyclic esters bearing nonluminophores. In the process, the large excess hydroxyl-mod

Full text of DOI:10.1021/ma500985j

Article
pubs.acs.org/Macromolecules
A New Strategy To Access Polymers with Aggregation-Induced
Emission Characteristics
Wei Zhao, Chuanyang Li, Bo Liu, Xue Wang, Ping Li, Yang Wang, Chunji Wu,†
†
,‡
†,‡
†
†,‡
§
†,‡
Changguang Yao,†,‡ Tao Tang, Xinli Liu,* and Dongmei Cui*
†
,†
,†
†State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, People’s Republic of China
‡
University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
§Jinzhou City Health School, Beijing Road 4-26, Jinzhou, Liaoning 121001, China
*
S Supporting Information
ABSTRACT: A highly efficient strategy for synthesizing the
first biocompatible polyesters with AIE characteristics has been
established via immortal ring-opening polymerizations of cyclic
esters bearing nonluminophores. In the process, the large
excess hydroxyl-modified AIE active compound, acting as the
chain transfer agent, attaches to the active rare-earth metal
catalyst via the rapid-reversible exchange reaction to initiate
the polymerization. Thus, more polyester chains appear to
grow from one active metal species, and the AIE fragments are
incorporated into the polymer chains at specific sites, in situ.
The resultant polyesters have linear, block, or star-shaped
microstructures mimicking those of the modified AIE
compounds. The polymerization solutions can be directly fabricated to large-area thin solid films. The obtained PLA, for
instance, emits fluorescence in water/THF mixtures owing to aggregation, the intensity of which is 2850-fold stronger than that
in THF solution. This strategy avoids complicated preparation of AIE-active monomers and/or usage of toxic metal reagents for
catalyzing the coupling reactions in order to introduce AIE-active fragments, which provides a straightforward approach to access
AIE active or other functional polymers from hardly modified monomers.
INTRODUCTION
By merit of their good capacity to be facilely fabricated into
■
thin solid films and devices by spin-coating, static casting, and
Luminescent materials have gained an upsurge in research
interest in the past decades due to their promising applications
in electronic and biomedical areas.
the luminophores are only highly emissive in dilute solutions,
and aggregations often cause partial or even complete
quenching of the light emissions (ACQ). To alleviate the
ACQ effect in the condensed phase, various chemical, physical,
7
inkjet printing under mild conditions, AIE-active polymers
1
−3
have become the research target. To date, the mostly explored
polymers with AIE characteristic are those bearing conjugated
double or triple bonds such as polyacetylenes, polyphenylenes,
polytriazoles, poly(phenyleneethynylene)s, and poly-
In many cases, however,
(
phenylenevinylene)s, which are synthesized by polymerization
of the monomers modified by the AIE-active luminogens or by
attaching the polymers to the predesigned substrates bearing
these units via Sonagashira−Hagihara coupling or click
4
and engineering approaches have been developed, which,
sometimes, are accompanied by severe side effects. In contrast,
the propeller-like small molecules show “aggregation-induced
emission (AIE)” phenomenon coined by Tang and co-workers
in 2001, where the aggregation facilitates light-emitting
8
reactions. Recently, a few saturated polyolefins (possessing
no chromophoric units in their backbones) such as poly-
styrene)s, poly(acrylate)s, and poly(acrylamide)s are prepared
(
5
processes of luminogens. Since then, many organic fluorogens
by anionic or radical polymerizations of the corresponding AIE
9
have been found to show the AIE effect and many high-tech
applications, such as fluorescence sensors, biological probes,
immunoassay markers, PAGE visualization agents, and
unit functionalized monomers. Besides these remarkable
achievements, development of polymers, in particular, the
biodegradable and biocompatible polymers, with in situ
generated AIE features in more facile manners, obviously, will
6
reporters for micelle formation. These low molecular weight
luminescent materials with AIE effects have to be fabricated
into thin solid films when processing by expensive techniques,
such as vacuum sublimation and vapor deposition, prohibiting
manufacturing large-area flat-panel devices.
Received: May 13, 2014
Revised: July 23, 2014
©
XXXX American Chemical Society
A
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be the next challenging topic: the most promising applications
of the AIE-active polymers as the bioprobes of real-time
imaging take the furthest advantages of AIE features; the
biodegradable polymers are usually arising from hardly
functionalized monomers.
Herein, we wish to report a novel and efficient strategy,
named “AIE-active molecules mediated chain transfer polymer-
ization”, which employs a rare-earth metal catalyst shuttling
among the excess AIE-active compounds as the chain transfer
agents (CTA) via fast-reversible exchange reaction, to initiate
polymerizations. Polymer chains appear to grow from the CTA,
thus achieving extremely high catalyst productivity and
incorporating the AIE-active units in situ into the obtained
polymer chains at well-defined positions (Scheme 1). The AIE-
complicated. Until now, there are no reports of such AIE-active
polyesters.
10
RESULTS AND DISCUSSION
■
Synthesis of Catalysts Bearing AIE-Active Moiety. The
synthesis of the AIE-active polyesters, if tetraphenylethenes
(
TPE), a typical propeller-like AIE active moiety, is chosen,
involves three steps: (1) preparation of the hydroxyl function-
alized TPE-n(OH) (n = 1, 2, 4); (2) reaction of TPE-n(OH)
with a rare-earth metal coordination catalyst; (3) TPE-n(OH)-
mediated living-chain transfer ROP of cyclic esters, alter-
natively, immortal ROP. Mono-, di-, and tetrahydroxyl-
functionalized tetraphenylethenes TPE-OH, TPE-2OH, and
TPE-4OH were synthesized following the modified literature
12
procedure (Scheme 2). (Details of preparation and character-
ization are provided in the Experimental Section.) TPE-OH
was employed, for the first time, to react stoichiometrically with
Scheme 1. Strategy for Synthesizing Polymers with AIE
Characteristics
13
O,N,N,O-tetradentate Salan lutetium alkyl complex 1. Meta-
thesis reaction between lutetium alkyl moiety Lu−CH SiMe in
2
3
1
and the hydroxyl group of TPE-OH generated a TPE-labeled
Lu−alkoxide counterpart TPE-O-[Lu], selectively (Scheme 3),
as evidenced by NMR monitoring result (Figures 1 and Figure
S1). Accordingly, treatment of TPE-2OH and TPE-4OH with 2
and 4 equiv complex 1, respectively, afforded the alkoxide
counterparts TPE-2O-[Lu] and TPE-4O-[Lu] in quantitative
1
1
yields (the H NMR spectrum of TPE-2O-[Lu] and H NMR,
13
13
C NMR, and C DEPT (135°) spectra of TPE-4O-[Lu] are
active compounds are alcohols in this work; thus, the strategy is
suitable for the ring-opening polymerizations (ROP) of cyclic
esters. These polyesters are biodegradable and biocompatible
materials possessing versatile mechanical properties and low
immunogenicity, having been employed as matrixes in
pharmaceutical and medical fields as well as imaging and
ratiometric sensing applications. Whereas, these polymers are
usually hydrophobic and their monomers are hardly function-
alized, which make the modification process tedious and
shown in Figures S2−S5).
Synthesis of AIE-Active Polymers. To our delight, all the
three alkoxide derivatives TPE-O-[Lu], TPE-2O-[Lu], and
TPE-4O-[Lu] showed high activity toward the ROP of rac-LA
in THF at room temperature (Schemes 4 and 5) to transfer 500
equiv of rac-LA to polylactide (PLA) within 1 h in high yields
11
1
(Table 1, entries 1−3). The H NMR spectra of the oligomeric
PLA samples indicated that the coordination−insertion of rac-
LA took place at metal−oxygen bond of each TPE-O-[Lu] unit;
a
Scheme 2. Synthesis of Hydroxyl-Functionalized TPE
a
Reagents and conditions: (a) Zn, TiCl , THF; (b) 2-chloroethoxyethanol, K CO , KI, DMF.
4
2
3
B
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Scheme 3. Synthesis of TPE-Labelled Lutetium Alkoxide Complexes TPE-O-[Lu], TPE-2O-[Lu], and TPE-4O-[Lu]
faster. In the CH Cl medium, TPE-4O-[Lu] could also initiate
2
2
rapid ROP of rac-BBL to give the syndiotactic product (P =
r
0
.83) (Scheme 5) (Table 1, runs 4−7). The resultant PBBL,
PMAC, and PMPC all have star-shaped microstructures with a
AIE-active “core”. Noteworthy was that the latter two
polycarbonates bear pendant unsaturated C−C double bonds
or C−C triple bonds, leaving versatile options for swift
postpolymerization modification.
TPE-OH, TPE-2OH, and TPE-4OH Mediated Living
Chain Transfer Polymerization. For a living polymerization
system, however, one molecule of catalyst leads to the growth
of only one macromolecular chain. Thus, the catalyst
productivity is low, and a large quantity of the quite expensive
catalyst would therefore be required for a relatively small batch
of polymer, which is also responsible for the contamination of
polymers with high catalyst residue. If the obtained polymers
are applied in medical and pharmaceutical (or microelectonic)
fields, it always encounters tedious manipulations of catalyst
removal and polymer purification to avoid issues revolving
around the residual metal traces in the final products. Immortal
1
Figure 1. H NMR spectrum of TPE-O-[Lu] (400 MHz, THF-d +
8
CDCl , 25 °C).
3
thus, the resultant PLAs were automatically labeled by the TPE
moiety at the end (TPE-O-PLA) or the middle of the linear
PLAs (TPE-2O-PLA), or the core of the four-armed PLA
TPE-4O-PLA), with respect to the complex employed
Figures 2−4). The resultant PLAs had molecular weights
determined by GPC and M
ones (Mn,calcd) together with extremely low polydispersity
indexes (PDI < 1.06), indicating a living polymerization mode.
Moreover, all PLAs possessed very high heterotacticity (P =
.99), which confirmed further that the hydroxyl-modified AIE-
active compounds TPE-n(OH) reacted with the lutetium−alkyl
moiety exclusively while the Salan ligand remained untouched
to govern the selectivity via its cagelike steric environment
14
polymerization (IMP), a special case of coordination chain
15
transfer polymerization (CCTP), where the growing macro-
molecular chain is able to transfer from the active species to the
chain transfer agent (CTA) without occurrence of other chain
termination pathways, allowing the growth of several polymer
chains per catalyst molecule, is the most efficient manner to
carry out a polymerization with the least amount of catalyst.
However, the AIE-active TPE-n(OH) have never been
employed as the chain transfer agent, whether they can
perform the rapid and reversible exchange reaction with the
catalyst molecule, the key point of constructuring a living
immortal polymerization, namely, the catalyst “running fast”
among the large amount of TPE-n(OH) to transfer the active
moiety to them, is unknown.
(
(
(
) very close to those theoretic
n,GPC
r
0
13
around metal active center.
The above methodology was extended successfully to other
cyclic esters. Under the same polymerization conditions, by
using TPE-4O-[Lu] as the initiator, the ROP of CL or the allyl
or alkyne functionalized carbonates MAC and MPC went even
Thus, we first attempted the straightforward preparation of
the AIE-active initiators by directly mixing “TPE-OH”, “TPE-
2OH”, or “TPE-4OH” with complex 1 ([Lu]/[OH] = 1)
C
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Scheme 4. Synthesis of AIE-Active PLA by Using Salan Lutetium Alkoxide Complexes TPE-O-[Lu] and TPE-2O-[Lu]
without further work-up process. These in situ generated
initiators showed the similar performances to the isolated ones,
suggesting the formation of the active species was rapid and
selective. Enlightented by this result, multiple equivalents TPE-
OH were added to the ROP system of rac-LA with the [TPE-
OH]/[Lu] molar ratio varying from 5:1 to 100:1. Surprisingly
to us, the polymerization proceeded smoothly without obvious
Obviously, these α-TPE, ω-hydroxyl-functionalized polymers
were excellent building blocks for further modification.
Characteristics of the Obtained AIE-Active Biocom-
patible Polymers. Owing to incorporating TPE moieties, all
the obtained polymers were evaluated for their luminescent
properties. The AIE-active labeled star polymer TPE-4O-PLA
was practically nonluminescent when molecularly dissolved in
good solvents, and its photoluminescence (PL) spectrum in
dilute THF solution was almost a flat line parallel to the
abscissa. Strikingly, as shown in Figure 5a, a strong PL signal
was recorded under the same experimental conditions when
water was added into the THF solution due to the aggregate
formation. The emission intensified gradually with increasing
1
termination ( H NMR monitoring the reaction of TPE-O-[Lu]
with TPE-OH under the molar ratio of 1:3 in the presence of
2
0 equiv of rac-LA in THF-d was shown in Figure S6). The
8
4
4
molecular weights (M = 0.16 × 10 −1.45 × 10 ) of the
n
resultant PLAs decreased in inverse proportion with the
increase of [TPE-OH], and no broadened molecular weight
distribution was observed (PDI = 1.04−1.05), indicative of an
immortal polymerization (Table 1, runs 8−11). Moreover, the
hetereoselectivity of the precursor 1 (Pr > 0.98) was
maintained, suggesting that complex TPE-O-[Lu] was very
stable in the presence of large amount of TPE-OH without
ligand dissociation from the metal center. TPE-OH behaved as
the chain transfer agent to mediate a rapid and reversible
exchange reaction with the active species [Lu]-O-TPE (or the
simultaneously generated polymeric active species [Lu]-
the water fraction f
enhancement increased rapidly when f
in the THF/water mixtures. The
> 40%. At f = 90%,
w
w
w
the intensity was more than 2850-fold stronger than that in
THF (Figure 5b). The obtained luminogenic materials also
displayed good processing property. For instance, the TPE-4O-
PLA could be facilely fabricated into large film on a glass
substrate by the simple spin-coating. Figure 6a demonstrates
the photographs of TPE-4O-PLA-coated glass substrate taken
under room light and UV illumination. The coated glass
substrate was strongly luminescent under UV illumination. The
other isolated polymers also displayed strong luminescence in
their solid states under UV illumination (Figure 6b).
OCHCH CO-(PLA)-O-TPE). Thus, the resultant PLAs were
3
automatically end-capped with TPE moiety at one end and
hydroxyl at the other end, which involved in the polymerization
cycle and took the same role as TPE-OH. Therefore, when the
polymerization achieved completeness under a [LA]:[Lu]:
CONCLUSION
■
[OH] ratio of 1000:1:100, 100 PLA chains with TPE-label grew
In summary, we have demonstrated for the first time that
polymers with AIE characteristics can be synthesized in situ by
living chain transfer polymerization. The AIE-active com-
pounds, for instance TPE, are modified with primary hydroxyl
groups TPE-n(OH), which attach to the active metal centers
via metathesis reaction with the coordination catalyst, the
Salan-ligated lutetium alkyl complex. Because the exchange
reaction between the primary hydroxyl and the lutetium
from each active metal center (run 11). When TPE-2OH or
TPE-4OH was employed instead of TPE-OH, the ROP of rac-
LA could also proceed in an immortal fashion to afford linear
PLAs with the TPE moiety placed in the middle of the polymer
chains or four-armed PLAs with the AIE-active “core” (Scheme
6
, Table 1, runs 12−21). So were the cases of rac-BBL, CL,
MAC, and MPC as the monomers (Table 1, runs 22−26).
D
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Scheme 5. Synthesis of Four-Armed, Star-Shaped AIE-Active Biocompatible Polymer by Using Salan Lutetium Alkoxide
Complexes TPE-4O-[Lu]
1
3a
alkoxide is rapid and reversible while the ligand remains
untouched, apparently, more polyester macromolecules prop-
agate from one active metal center to achieve an up to 10 000%
catalyst efficiency with respect to the amount of TPE-n(OH)
loaded, and the specific selectivity of the complex is reserved in
the cases of rac-LA and BBL monomers. Meanwhile, the AIE-
active units are incorporated into the polymer chains at well-
defined positions relating to the structures of TPE-n(OH). The
resultant biodegradable polyesters exhibit unique emission
properties that were observed in the aggregation states as well
as in the solid states. Contrary to the conventional methods,
this strategy avoids high catalyst residues, in particular the toxic
ones for the coupling reactions, which opens an approach to
access biodegradable polymers; those usually arise from hardly
modified monomers such as cyclic esters that bear non-
luminogens, for their promising real-time imaging and sensor
applications.
complex 1 followed the established method. D,L-Lactide (Aldrich)
was recrystallized three times with dry ethyl acetate. Hydroxyl-
12
functionalized TPEs were synthesized according the literature and
dried over anhydrous magnesium sulfate in THF prior to using for
polymerization.
Typical Polymerization of rac-Lactide in the Presence of
Hydroxyl-Functionalized TPE. A typical procedure for polymer-
ization of rac-LA in the presence of hydroxyl-functionalized TPEs
TPE-OH, TPE-2OH, or TPE-4OH) was performed in a 25 mL
round flask under an N atmosphere. To a vigorously stirred solution
of complex 1 in 3 mL of THF was added corresponding hydroxyl-
functionalized TPE in 2 mL of THF. After 10 min, rac-LA was added
quickly. The polymerization took place immediately at room
temperature. After a specified polymerization time, an aliquot was
(
2
withdrawn and quenched quickly with 1.0 mL of HCl/CH OH/
CHCl (0.1/10/60 v/v) solution, and then 1.0 mL of THF was added
to obtain a clear solution. Several drops of the quenched solution was
taken, removed volatiles, and subjected to monomer conversion
3
3
determination which was monitored by integration of monomer vs
1
polymer methane or methyl resonances in HNMR (CDCl ). The
3
EXPERIMENTAL SECTION
■
residue solution was quenched by an excess amount of ethanol,
filtered, washed with ethanol, and then dried at 40 °C for 24 h in vacuo
to give polymer product. The molecular weight and the molecular
weight distribution of the resulting polymer were determined by GPC.
The tacticity of the PLA was calculated according to the methine
General Procedures. All reactions were carried out under a dry
and oxygen-free argon atmosphere by using Schlenk techniques or
under a nitrogen atmosphere in an MBraun glovebox. Solvents were
purified by an MBraun SPS system. Ligands were synthesized
1
1
according to modified literature procedures. The phenols and amines
region homonuclear decoupling H NMR spectrum.
were purchased from Aldrich or Fluka. All liquids were dried over 4 Å
molecular sieves for a week and distilled before use, and solid materials
were used without purification. The synthesis of Salan lutetium
Synthesis of Hydroxyl-Functionalized TPEs. Synthesis of TPE-
OH. This reaction was performed following the procedures described
3
in the literature. A suspension of TiCl (0.78 mL, 7.0 mmol) and Zn
4
E
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Table 1. Immortal Polymerizations of Cyclic Esters with Hydroxyl-Modified TPE Derivatives as the Chain Transfer Agents
a
[Lu]/[CTA] /[Mono] time (min) conv (%) Mn,calcd × 10−4
b
c
Mn,NMR × 10−4
d
Mn,GPC × 10−4
e
e
f
run
Mono
CTA
PDI
Pr/Pm
1
2
3
rac-LA
rac-LA
rac-LA
rac-BBL
CL
TPE-OH
1/1/500
30
60
60
10
1
87
94
6.31
13.60
26.02
1.59
22.90
8.08
8.00
1.30
0.71
0.25
0.14
6.18
1.31
0.68
0.27
0.13
6.92
1.52
0.75
0.28
0.16
1.84
0.73
1.22
2.08
2.06
6.40
14.12
27.32
1.66
24.00
8.83
8.64
1.45
0.75
0.27
0.16
6.30
1.36
0.70
0.27
0.14
7.12
1.64
0.77
0.30
0.18
1.77
0.66
1.31
2.16
1.05
1.03
1.04
1.07
1.18
1.07
1.08
1.04
1.04
1.03
1.05
1.03
1.02
1.03
1.04
1.03
1.06
1.03
1.04
1.05
1.05
1.08
1.06
1.04
1.03
1.04
0.99/0.01
0.99/0.01
0.99/0.01
0.83/0.17
TPE-2OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-OH
1/0.5/500
1/0.25/500
1/0.25/100
1/0.25/500
1/0.25/100
1/0.25/100
1/5/500
90
g
4
44
5
6
7
8
9
100
100
100
87
MAC
10
10
30
60
60
60
30
30
30
60
60
35
30
60
120
120
30
30
30
30
30
MPC
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-LA
rac-BBL
rac-BBL
CL
0.99/0.01
0.99/0.01
0.99/0.01
0.98/0.02
0.99/0.01
0.98/0.02
0.99/0.01
0.98/0.02
0.98/0.02
0.99/0.01
0.99/0.01
0.99/0.01
0.98/0.02
0.98/0.02
0.83/0.17
0.82/0.18
TPE-OH
1/10/500
1/50/1000
1/100/1000
1/1/500
92
0.73
0.26
0.15
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
TPE-OH
73
TPE-OH
68
TPE-2OH
TPE-2OH
TPE-2OH
TPE-2OH
TPE-2OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
TPE-4OH
85
1/5/500
87
1/10/500
1/50/1000
1/100/1000
1/1/500
87
0.70
0.26
0.13
76
55
95
1/5/500
100
94
1/10/500
1/50/1000
1/100/1000
1/1/300
0.76
0.30
0.16
73
60
g
68
g
1/10/300
1/5/500
59
100
100
100
MAC
1/5/500
MPC
1/5/500
2.13
a
b
1
c
Polymerizations were performed under N in THF at 25 °C, [LA] = 0.69 M. Obtained from H NMR analysis. Calculated based on monomer
2
0
conversion and the assumption that one PLA chain is generated per Lu−O metal species ([Mono] /[CTA] ) × M
× X (X = conv) + MCTA.
0
0
Mono
d
1
e
Determined from H NMR spectrum. Determined by GPC in THF using polystyrene standards (the obtained M for PLA and PCL were
n
f
corrected with 0.58 and 0.56, respectively). P /P of PLA is the probability of racemic/mesomeric linkages between monomer units determined
r
m
1
g
from the methane region of the homonuclear decoupled H NMR spectrum, P + P = 1. Polymerizations were performed under N in CH Cl at
r
m
2
2
2
2
5 °C, [BBL] = 1.16 M, P /P of PBBL (entries 22 and 23) is the probability of racemic/mesomeric linkages between monomer units determined
0 r m
13 1
by C{ H} NMR spectrum, P + P = 1.
r
m
1
1
Figure 2. H NMR spectrum of oligomeric TPE-O-PLA (400 MHz,
Figure 3. H NMR spectrum of oligomeric TPE-2O-PLA (400 MHz,
CDCl , 25 °C).
CDCl , 25 °C).
3
3
dust (0.92 g, 14.0 mmol) in 35 mL of dry THF was refluxed under a
N atmosphere for 2 h. A solution of 4-hydroxybenzophenone (0.69 g,
2
times with ethyl acetate (25 mL). The combined organic fractions
3
.5 mmol) and benzophenone (0.64 g, 3.5 mmol) in dry THF (15
were washed with water and dried over MgSO . The solvents were
4
mL) was added to the suspension of the titanium reagent, and the
reaction was allowed to proceed at reflux for 4 h. The reaction mixture
was cooled to 25 °C and poured into a 10% aqueous K CO solution
removed in vacuo to afford 4-(1,2,2-triphenylvinyl)phenol (M1). The
crude product was purified by a silica gel column using hexane−ethyl
acetate (1:1, v/v) as eluent. Compound M1 was obtained in 65% yield
2
3
1
(
50 mL), and after vigorous stirring for 5 min, the dispersed insoluble
(0.79 g). H NMR (400 MHz, CDCl , 25 °C): δ = 7.14−6.97 (15H,
3
H
material was removed by vacuum filtration using a Celite pad. The
m, C H ), 6.87 (2H, d, C H ), 6.54 (2H, d, C H ), 4.66 (1H, s,
6 5 6 4 6 4
organic layer was separated, and the aqueous layer was extracted three
C H OH)
6 4
F
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7
2.67 (CH ), 69.63 (CH ), 67.18 (CH ), 61.64 (CH ). MALDI-TOF
2
2
2
2
+
[
M+1] : found: 540.2495; calcd: 540.25.
1
TPE-4OH. White solid, yield 80%. H NMR (400 MHz, CDCl , 25
3
°
3
3
C): 6.91 (8H, d, C H ), 6.65 (8H, d, C H ), 4.07 (8H, t, ArOCH ),
6
4
6
4
2
.83 (8H, t, ArOCH CH ), 3.74 (8H, t, ArOCH CH OCH CH OH),
2 2 2 2 2 2
.65 (8H, t, ArOCH CH OCH CH OH), 2.15 (4H, t, Ar-
2
2
2
2
1
3
OCH CH OCH CH OH). C NMR (400 MHz, CDCl , 25 °C):
2
2
2
2
3
1
7
56.91 (Ar), 138.48 (Ar), 137.07 (Ar), 132.51 (Ar), 113.75 (Ar),
2.63 (CH ), 69.68 (CH ), 67.20 (CH ), 61.69 (CH ). MALDI-TOF
2
2
2
2
+
[
M + 1] : found: 748.3448; calcd: 748.35.
Synthesis of Catalysts Bearing AIE-Active Moiety. Synthesis
of Complex TPE-O-[Lu]. To a THF (2.5 mL) solution of complex 1
0.2 g, 0.2333 mmol) was dropwise added equivalent AIE-OH (0.1018
g, 0.2333 mmol, in 2.5 mL of THF) slowly. After being stirred at 25
C for 10 min, volatile materials were then removed in vacuo, giving
(
°
1
complex TPE-O-[Lu] in a quantitative yield (0.28 g). H NMR (400
MHz, THF-d + CDCl , 25 °C) δ 7.22 (2H, d, JHH = 2.5, C H ),
8
3
H
6
2
7
.09−6.92 (15H, m, C H ), 6.89 (2H, d, J = 2.5, C H ), 6.87 (2H,
1
6
5
HH
6
2
Figure 4. H NMR spectrum of oligomeric TPE-4O-PLA (400 MHz,
d, J = 8.7, C H ), 6.61 (2H, d, J = 8.7, C H ), 4.16−4.07 (4H, m,
LuOCH + ArCH N), 4.00 (2H, t, J = 5.0, ArOCH ), 3.79 (2H, t,
HH
6
4
HH
6
4
CDCl , 25 °C).
3
2
2
HH
2
JHH = 4.9, ArOCH CH O), 3.63 (4H, s, THF), 3.58 (2H, t, J = 5.4,
2
2
HH
LuOCH CH ), 3.09 (2H, d, J = 12.3, ArCH N), 2.57 (2H, t, J =
2
2
HH
2
HH
A mixture of compound M1 (0.35 g, 1.00 mmol), 2-chloroethox-
5
.5, N(CH ) N), 2.00 (6H, s, N(CH ) ), 1.91 (2 H, t, J = 5.5,
yethanol (0.31 g, 2.5 mmol), K CO (1.04 g, 7.5 mmol), and
2 2 3 2 HH
2
3
N(CH ) N), 1.76 (4H, s, THF), 1.46 (18H, s, C(CH ) ), 1.26 (18H,
potassium iodide (0.16 g, 1.0 mmol) in DMF (25 mL) was stirred at
2
2
3 3
s, C(CH ) ). Anal. Calcd for C H LuN O : C, 67.76%, H, 7.44%, N,
1
00 °C for 8 h under a N atmosphere. After removal of solvent, ethyl
3
3
68 89
2
6
2
2
.32%. Found: C, 67.65%, H, 7.36%, N, 2.23%.
acetate was added to the mixture. The organic layer was washed with
saturated aqueous solutions of NaHCO , H O, and NaCl and dried
Synthesis of Complex TPE-2O-[Lu]. To a THF (2.5 mL) solution
3
2
of complex 1 (0.2 g, 0.2333 mmol) was dropwise added 1/2 equiv of
AIE-2OH (0.0631 g, 0.1167 mmol, in 2.5 mL of THF) slowly. After
being stirred at 25 °C for 10 min, volatile materials were then removed
over anhydrous Na SO . After filtration and removal of the solvent, the
2
4
residue was chromatographed over silica gel (ethyl acetate/hexane =
:4) to give TPE-OH (0.39 g, 90% yield) as a white solid. TPE-OH:
1
1
in vacuo, giving complex TPE-2O-[Lu] in a quantitative yield (0.24 g).
H NMR (400 MHz, CDCl , 25 °C): δ = 7.14−6.97 (15H, m, C H ),
3
H
6
5
1
H NMR (400 MHz, THF-d + CDCl , 25 °C) δ 7.22 (4H, d, J =
6
(
(
.91 (2H, d, C H ), 6.66 (2H, d, C H ), 4.04 (2H, t, ArOCH ), 3.82
8
3
H
HH
6
4
6
4
2
2
6
.5, C H ), 7.06−6.95 (10H, m, C H ), 6.89 (4H, d, J = 2.5, C H ),
2H, t, ArOCH CH ), 3.74 (2H, t, ArOCH CH OCH CH OH), 3.66
6
2
6
5
HH
6
2
2
2
2
2
2
2
.84 (4H, d, J = 8.7, C H ), 6.59 (4H, d, J = 8.7, C H ), 4.12
2H, t, ArOCH CH OCH CH OH), 2.15 (1H, t, Ar-
HH
6
4
HH
6
4
2
2
2
2
13
(4H, d, JHH = 12.3, ArCH N), 4.06 (4H, s, LuOCH ) 4.00 (4H, s,
OCH CH OCH CH OH). C NMR (400 MHz, CDCl , 25 °C):
2
2
2
2
2
2
3
ArOCH ), 3.79 (4H, s, ArOCH CH O), 3.64 (8H, s, THF), 3.58 (4H,
1
1
6
57.34 (Ar), 143.67 (Ar), 139.91 (Ar), 136.83 (Ar), 131.07 (Ar),
2
2
2
t, JHH = 5.2, LuOCH CH ), 3.08 (4H, d, J = 12.3, ArCH N), 2.56
27.74 (Ar), 126.27 (Ar), 113.55 (Ar), 72.61 (CH ), 69.49 (CH ),
2
2
HH
2
2
2
+
(
4H, t, JHH = 5.5, N(CH ) N), 2.00 (12H, s, N(CH ) ), 1.90 (4H, t,
6.84 (CH ), 61.78 (CH ). MALDI-TOF [M + 1] : found: 436.2022;
2 2 3 2
2
2
JHH = 5.5, N(CH ) N), 1.77 (8H, s, THF), 1.46 (36H, s, C(CH ) ),
calcd: 436.20.
2
2
3 3
1
6
.26 (36H, s, C(CH ) ). Anal. Calcd for C110H Lu N O : C,
3.57%, H, 7.66%, N, 2.70%. Found: C, 63.49%, H, 7.48%, N, 2.55%.
Synthesis of Complex TPE-4O-[Lu]. To a THF (2.5 mL) solution
Synthesis of TPE-2OH and TPE-4OH. The synthetic procedures are
3 3 158 2 4 12
similar to those of TPE-OH described above. TPE-2OH: White solid;
1
yield 88%. H NMR (400 MHz, CDCl , 25 °C): δ = 7.14−6.98
3
H
(
10H, m, C H ), 6.90 (4H, d, C H ), 6.63 (4H, d, C H ), 4.05 (4H, t,
of complex 1 (0.2 g, 0.2333 mmol) was dropwise added 1/4 equiv of
AIE-4OH (0.0436 g, 0.0583 mmol, in 2.5 mL of THF) slowly. After
being stirred at 25 °C for 10 min, volatile materials were then removed
6
5
6
4
6
4
ArOCH ), 3.82 (4H, t, ArOCH CH ), 3.74 (4H, t, Ar-
2
2
2
OCH CH OCH CH OH), 3.66 (4H, t, ArOCH CH OCH CH OH),
2
2
2
2
2
2
2
2
13
2
.15 (2H, t, ArOCH CH OCH CH OH). C NMR (400 MHz,
in vacuo, giving complex TPE-4O-[Lu] in a quantitative yield (0.22 g).
2
2
2
2
1
CDCl , 25 °C): 157.04 (Ar), 144.17 (Ar), 139.69 (Ar), 136.68 (Ar),
H NMR (400 MHz, THF-d , 25 °C) δ 7.22 (2H, d, JHH = 2.5,
8 H
3
1
32.54 (Ar), 131.35 (Ar), 127.69 (Ar), 126.24 (Ar), 113.69 (Ar),
C H ), 6.90 (2H, d, J = 2.5, C H ), 6.86 (2H, d, J =8.4, C H ),
6 2 HH 6 2 HH 6 4
Scheme 6. Synthesis of AIE-Active Biocompatible Polymers via a Fast Running Catalyst
G
dx.doi.org/10.1021/ma500985j | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 5. (a) Photoluminescence (PL) spectra of TPE-4O-PLA in THF/water mixtures with different water fractions measured at 25 °C. (b) Plot of
I/I versus water fraction in the THF/water mixture (I is PL intensity in THF/water mixtures with different water fractions; I is PL intensity in pure
0
0
THF solution). Inset: photographs of THF/water mixtures of TPE-4O-PLA with different water fractions taken under UV illumination (TPE-4O-
4
−5
PLA, M = 7.12 × 10 ; [TPE-4O-PLA] = 1.0 × 10 mol/L).
n
Figure 6. (a) Photographs of AIE-active PLA-coated glass substrate taken under room light and UV illumination. (b) Photographs of star-shaped
luminogenic biocompatible polymers under room light and UV illumination.
6
3
.60 (2H, d, JHH = 8.4, C H ), 4.11 (4H, m, LuOCH + ArCH N),
ACKNOWLEDGMENTS
6
4
2
2
■
.97 (2H, t, JHH = 4.7, ArOCH ), 3.75 (2H, t, J
= 4.7,
HH
2
The authors thank financial support from the National Natural
Science Foundation of China for project Nos. 21361140371,
1321062, 51233005, and 21274143.
ArOCH CH O), 3.59−3.52 (6H, m, LuOCH CH + THF), 3.08
2
2
2
2
(
2H, d, JHH = 12.3, ArCH N), 2.56 (2H, t, J = 5.5, N(CH ) N),
2 HH 2 2
5
2
.01 (6H, s, N(CH ) ), 1.92 (2H, t, J = 5.5, N(CH ) N), 1.72 (4H,
3 2 HH 2 2
s, THF), 1.47 (18H, s, C(CH ) ), 1.25 (18H, s, C(CH ) ). Anal.
3
3
3 3
REFERENCES
Calcd for C194H296Lu N O : C, 60.93%, H, 7.80%, N, 2.93%. Found:
4
8
24
■
C, 60.77%, H, 7.51%, N, 2.76%.
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(
H− H COSY NMR spectrum of TPE-O-[Lu], H NMR
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13
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Corresponding Authors
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dx.doi.org/10.1021/ma500985j | Macromolecules XXXX, XXX, XXX−XXX