Construction of Self-Reporting Biodegradable CO2-Based Polycarbonates for the Visualization of Thermoresponsive Behavior with Aggregation-Induced Emission Technology?

Article abstract of DOI:10.1002/cjoc.202100372

Thermoresponsive polymers with simultaneous biodegradability and signal “self-reporting” outputs that meet for advanced applications are hard to obtain. To address this issue, we developed fluorescence signal “self-reporting” biodegradable thermoresponsiv

Full text of DOI:10.1002/cjoc.202100372

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Title: Construction of Self-Reporting Biodegradable CO2-based Polycarbonates for
the Visualization of Thermoresponsive Behavior with Aggregation-Induced
Emission Technology
Authors: Molin Wang, Enhao Wang, Han Cao, Shunjie Liu,* Xianhong Wang,* and
Fosong Wang
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Cite this paper: Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
Construction of Self-Reporting Biodegradable CO2-based Poly-
carbonates for the Visualization of Thermoresponsive Behavior
with Aggregation-Induced Emission Technology
Molin Wang,a,b Enhao Wang,a,b Han Cao,a,b Shunjie Liu,*,a,b Xianhong Wang,*,a,b and Fosong Wanga,b
a Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022,
China.
b School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, 230026, China
Keywords
CO2 copolymerization| polycarbonates | thermoresponsive polymers | aggregation-induced emission | visualization
Main observation and conclusion
Thermoresponsive polymers with simultaneous biodegradability and signal “self-reporting” outputs that meet for advanced applica-
tions are hard to obtain. To address this issue, we developed fluorescence signal “self-reporting” biodegradable thermoresponsive
polycarbonates through the immortal copolymerization of CO2 and oligoethylene glycol monomethyl ether-functionalized epoxides in
the presence of hydroxyl-modified tetraphenylethylene (TPE-OH). TPE-OH was used as chain transfer agent to afford well-defined
polycarbonates with controlled molecular weight (6000 ~ 17000 g mol-1) and aggregation-induced emission characteristics. Through
temperature-dependent fluorescence intensity study, low critical solution transition of TPE-labeled polycarbonates were determined
and the fine details of thermal-induced phase transition process were monitored. Further research indicated that tempera-
ture-controlled aggregation and dissociation of TPE moieties are the main reason for fluorescence intensity variations. We anticipate
that this work could offer a method to visualize the thermal transition process of thermoresponsive polycarbonates and broaden their
application fields as smart materials.
Comprehensive Graphic Content
*E-mail: sjliu@ciac.ac.cn, xhwang@ciac.ac.cn
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10.1002/cjoc.202100372
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Background and Originality Content
Scheme 1. Preperation of TPE-labeled thermoresponsive polycarbonates
Stimuli-responsive polymers are capable of responding “smartly”
with rapid physical or chemical transition to the external stimuli,
such as temperature, light, pH, electric field and ionic strength.[1-2]
Among them, thermoresponsive polymers with lower critical solu-
tion temperature (LCST) close to the body temperature have
shown a wide range of biomedical applications as drug delivery,
tissue engineering, and gene therapy due to their unique proper-
ties.[3] For this purpose, many thermoresponsive polymers have
been developed such as poly(N-isopropylacrylamide) (PNIPAM),[4-7]
poly(N-vinyl caprolactam) (PNVCL),[8-9] poloxamers[10] and polyox-
azolines,[11-13] etc. However, the non-biodegradability issue hin-
ders the in vivo applications. Despite strategies such as copoly-
√
thermoresponsive
√ fluorescence
biodegradable
√
signal “self-reporting” biodegradable thermoresponsive polycar-
bonates through the copolymerization of CO2 and
OEG-functionalized epoxides in the presence of hydroxyl-modified
tetraphenylethylene (TPE-OH) (Scheme 1). The binary
(salen)Co(III)Cl/PPNCl complex was utilized to afford polycar-
bonates with completely alternating structure which assures bio-
degradability.[34-35] The role of TPE-OH is of key importance. On
the one hand, it possesses unique aggregation-induced emission
(AIE) attributes,[36-37] which can change the fluorescence intensity
through the restriction of intramolecular motion (RIM) mecha-
nism subjected to thermal stimulus.[38] On the other hand, TPE-OH
acts as chain transfer agent (CTA) to give polycarbonates good
adjustability of molecular weight via the mechanism of immortal
polymerization.[39] Therefore, the molecular weight of TPE-labeled
thermoresponsive polymer can be well controlled in the range of
6000 ~ 17000 g mol-1. The thermoresponsive process of
TPE-labeled polycarbonates is reflected by fluorescence signal in
real time. Most importantly, through the derivative analysis of the
fluorescence curves, the fine temperature variation which re-
sponses to the microstructure’s transformation of the polymer
can be facilely visualized. Collectively, the present study provides a
new strategy to design fluorescence self-reporting thermorespon-
sive polymers.
merization
with
biodegradable
monomers[14-15]
or
post-polymerization modification[16-17] partially improve the bio-
degradability, the main architecture of the resulting materials still
suffers from incomplete degradation.[18] Therefore, it is of great
significance to develop thermoresponsive polymers with com-
plete biodegradability.
Copolymerization of carbon dioxide (CO2) and epoxides into
polycarbonates is regarded as a valid way to synthesize biode-
gradable polymers.[19-22] On the basis of the breakthrough in cata-
lyst design, various polycarbonates derived from different types of
epoxides have been successfully developed.[23-30] Through copol-
ymerization of a hydrophilic oligoethylene glycol monomethyl
ether (OEG) functionalized epoxide (a thermoresponsive unit)
with CO2, Wang and coworkers successfully synthesized biode-
gradable thermoresponsive polycarbonates.[31] However, the top-
ological architecture and molecular weight of the resulting poly-
mers are hard to control, owing to the incorporation of the third
epoxide monomer.[32] Moreover, just like common thermorespon-
sive polymers, the as-prepared biodegradable polycarbonates lack
accessible methods to rapidly and facilely reflect the microscopic
changes into visible or detectable signals, which make them diffi-
cult to become high value-added materials.[33] Therefore, it re-
mains challenging to prepare biodegradable thermoresponsive
polycarbonates with well-defined architecture and self-reporting
signal outputs.
Results and Discussion
Synthesis and Characterization of TPE-Labeled Ther-
moresponsive Polycarbonates.
Herein, to address the above issues, we developed fluorescence
Table 1. The copolymerization of epoxide/CO2 catalyzed by SalenCoCl/PPNCl using TPE-OH as CTA
polymer
CU
Mn
Entrya
monomer
feedb
Đ
(%) c
94
(%) d
(g mol-1)e
1
2
3
4
5
6
7
8
ME2GE
ME2GE
ME2GE
ME2GE
ME3GE
ME3GE
ME3GE
ME3GE
400/1/1/1
400/1/1/2
400/1/1/5
400/1/1/10
400/1/1/1
400/1/1/2
400/1/1/5
400/1/1/10
99
99
99
99
99
99
99
99
17100
11300
8100
1.21
1.24
1.23
1.17
1.20
1.18
1.18
1.15
93
93
93
93
93
89
89
6400
17900
15400
9700
7500
a The polymerization reactions were carried out in 2.0 mL of epoxides in 10 mL autoclaves, at 25°C and 3.0 MPa CO2. Note: to make sure the complete
b
conversion of epoxide monomer (> 99%), the reaction time of all polymerizations was set as 12h. The molar ratio of monomer: salenCoCl: PPNCl:
c
1
e
TPE-OH. Selectivity of polycarbonate over cyclic carbonate. d Determined by H NMR spectroscopy. Determined by gel-permeation chromatography in
2
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Self-Reporting Biodegradable CO2-based Polycarbonates for the Visualization of Thermoresponsive Behavior
Chin. J. Chem.
CH2Cl2 at35 °C calibrated with polystyrene standards.
TPE-labeled thermoresponsive polycarbonates are synthesized
by immortal copolymerization of CO2/OEG-functionalized epox-
ides using SalenCo(III)Cl/PPNCl catalyst system in the presence of
TPE-OH CTA. As illustrated in Scheme 1, to improve the hydro-
a
d
h
philicity, two kinds of epoxides, ME2GE and ME3GE, bearing dif-
e
ME2GE
f
ferent length of OEG were utilized to prepare thermoresponsive
g
e
a
d
d
b
c
polycarbonates P-MEnGE (n = 2, 3), where n represents the num-
ber of repeating units in the pendent OEG chains. The results of
immortal copolymerizations of CO2/MEnGE (n = 2, 3) are summa-
rized in Table 1. All the reactions were carried out with [epox-
ides]/[Co center] molar ratio of 400:1 at 25℃ under CO2 pressure
of 3.0 MPa. To ensure the complete monomer conversion (＞
99%), the reaction time was optimized to 12 h. A series of
P-MEnGE (n=2, 3) with different number-average molecular
weight (Mn) and relatively narrow molar mass dispersity (Đ) were
prepared by adjusting monomer-to-initiator (TPE-OH + salenCoCl
+ PPNCl) ratios (M/I). As shown in entries 1~4 in Table 1, with the
variation of M/I from 400: 1 to 400: 10, Mn of P-ME2GE reduced
gradually from 17100 g mol-1 to 6400 g mol-1 with a narrow Đ of
~1.2 (Figure S1). Similarly, in entries 5~8, the Mn of P-ME3GE was
controllable in the range of 17900 g mol-1 to 7500 g mol-1. It's
worth noting that the carbonate units (CU) content remained at
99% in all reactions suggesting the nearly complete alternating
structure. Moreover, the Mn of P-ME2GE and P-ME3GE displayed
good linear relationships with of M/I (Figure 1), demonstrating
the effective controllability of TPE-OH on the Mn of the resulting
polymers.[40] Altogether, well-defined TPE-labeled polycarbonates
with OEG side chains were successfully obtained.
c
f
h
b
c
P-ME2GE
d
b
a
ME3GE
b
g
e
a
c
e
c
e
P-ME3GE
a
d
a
b
c
b
d
Figure 2. 1H NMR spectra of samples (300 MHz, CDCl3). (a) ME2GE, (b)
ME3GE, (c) TPE-OH, (d) P-ME2GE (Mn = 6400 g mol-1), (e) P-ME3GE (Mn =
7300 g mol-1).
Thermoresponsive properties of fluorescent P-MEnGE in
Aqueous Solution.
The relationship between fluorescence properties and temper-
ature response of P-MEnGE (n = 2, 3) in aqueous solution was
studied using temperature-dependent fluorescence spectrometer.
Due to the hydrophilicity of OEG side chains, both of P-ME2GE and
P-ME3GE could disperse into tiny micelles in aqueous solution at
room temperature. The relationship between fluorescence prop-
erties and temperature response of P-MEnGE (n = 2, 3) in aqueous
solution was studied using temperature-dependent fluorescence
spectrometer. Due to the hydrophilicity of OEG side chains, both
of P-ME2GE and P-ME3GE exhibited good water solubility at room
temperature. P-ME2GE (Mn = 6400 g mol-1) and P-ME3GE (Mn =
7300 g mol-1) with comparable molecular weight were chosen as
examples to investigate their fluorescence-temperature proper-
ties. The aqueous solution of P-MEnGE (0.5 mg mL-1) exhibited
obvious fluorescence emission, owing to the presence of TPE unit.
Normally, P-MEnGE tended to form micelles in aqueous solution
where hydrophilic OEG chains stretched on the outside while
hydrophobic TPE and carbonate units aggregated into cores. The
hydrophobic aggregates trigger the RIM mechanism of TPE to give
strong fluorescence.[42-43] As shown in Figure 3, the two polymers
showed fluorescence emission peak at ~464 nm in aqueous solu-
tion at room temperature under excitation of 321 nm (Figure S15).
For P-ME2GE (Figure 4a), fluorescence intensity generally showed
a downward trend with the increase of temperature from 25 to
70 °C. The fluorescence intensity remained almost invariable at
low temperature (25 to 32 °C), but showed an abrupt decrease in
a
b
20
15
10
5
20
15
10
5
P-ME3GE
P-ME2GE
y = 4143 + 114.0x
R2 = 0.9910
y = 2371 + 110.8x
R2 = 0.9535
20
60
100
140
20
60
100
140
M/I
M/I
Figure 1. The relationship of Mn of the as-prepared polymer with M/I. (a)
P-ME2GE, (b) P-ME3GE.
Chemical structures of intermediates and polymers were con-
1
firmed by H NMR spectra (Figure 2 and Figure S2~S12) and ma-
trix-assisted laser desorption/ionization time-of-flight mass spec-
troscopy (MALDI-TOF). The characteristic peaks at 3.39, 3.56, and
3.60–3.75 ppm which corresponded to CH3 and CH2, respectively
in ME2GE and ME3GE (Figure 2a, b), were clearly observed in pol-
ycarbonate P-MEnGE (Figure 2d, e), indicating that the OEG chains
were incorporated into the polymer backbone. In addition, char-
acteristic peaks of TPE-OH (6.55-7.22 ppm in Figure 2c) were ap-
peared in P-MEnGE. Moreover, the strong signals at 5.04 and
4.15–4.55 ppm were ascribed to CH and CH2 in carbonate units.
Meanwhile, the absence of characteristic peaks of ether linkage
(homopolymer of epoxides, at 3.30–3.60 ppm) suggested that the
backbone of P-MEnGE was completely alternating (CU content >
99%).[41] MALDI-TOF spectroscopy showed the signals of two spe-
cies, [TPE-O(P-ME2GE)]Na+ (n = 9~24) and [TPE-O(P-ME3GE)]Na+ (n
= 8~26), again demonstrating the incorporation of TPE-OH into
the polymer (Figure S13, S14). Altogether, the above results
demonstrated the successful incorporation of TPE unit into the
backbone of polycarbonates.
a
b
Temp. (°C)
Temp. (°C)
P-ME2GE
P-ME3GE
25
30
32
34
36
38
40
42
47
52
55
57
59
61
63
65
70
25
30
32
34
36
38
40
42
47
52
55
57
59
61
63
65
70
400
450
500
550
600
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
Figure 3. Temperature-dependent fluorescence spectra of aqueous solu-
tion of (a) P-ME2GE (Mn = 6400 g mol-1) and (b) P-ME3GE (Mn = 7300 g
mol-1). Concentration: 0.5 mg mL-1. λex=321 nm.
Chin. J. Chem. 2021, 39, XXX－XXX
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3

Wang et al.
Report
the range of 32 to 45°C. Further increase to 60 °C led to the fluo-
began to dehydrate and induce phase transition. While, at the
rescence quenching of P-ME2GE. Therefore, upon phase transition, maximum temperature the polymer chains were almost
the self-reporting output is triggered and made visible by varia-
tions in fluorescence. Similar phenomena were also observed in
P-ME3GE aqueous solution and the rapid transition temperature
range was 40-56 °C (Figure 4b). Presumably, these phenomena
were caused by two reasons. On the one hand, the active intra-
molecular motion of TPE triggered by temperature resulted in
enhanced nonradiative decay of the excited state and then
weakened the fluorescence.[44] On the other hand, the newly
formed hydrophobic domains derived from dehydration of OEG
side chains with temperature provided platform for the intra-
molecular motion of TPE.[45]
completely dehydrated indicating the finish of the phase
transition.[47] Thanks to the AIE characteristics of TPE moieties,
temperature changes were monitored sensitively and the fine
details were revealed during the thermal-induced phase
transition of thermoresponsive polymer aqueous solution.
The Phase Transition Behaviors of TPE-Labeled Polycar-
bonates in water under various Temperatures.
The morphologies of P-MEnGE (n= 2, 3) in aqueous solution at
different temperature were characterized by dynamic light scat-
tering (DLS). As exhibited in Figure 5a, the aqueous solution of
P-ME2GE self-assembled into micelles with hydrodynamic diame-
ters (Dh) of about 20 nm at room temperature. The Dh of micelles
kept constant (20 nm) with an increase of temperature to 35 °C.
However, when temperature reached above 40 °C, Dh of micelles
leaped to 500 nm because of the aggregation of dehydrated
polymer chains.[48] This significant fluctuation of Dh with temper-
ature in the range of 35~40 °C properly exhibited the thermal
transition process of P-ME2GE near cloud point. In Figure 5b, the
Dh of P-ME3GE micelles remained stable at 50~55 °C while
showed a significant increase at 60 °C, indicating the cloud point
(54 °C) of P-ME3GE from molecular aggregation level. These re-
b 1.0
a
1.0
0.8
0.6
0.4
0.2
0.0
P-ME GE
3
P-ME2GE
0.8
0.6
0.4
0.2
0.0
30℃
40℃
50℃
60℃
24
32
40
48
56
64
72
24
32
40
48
56
64
72
Temperature (°C)
Temperature (°C)
0.05
c
d
1.0
0.8
0.6
0.4
0.2
0.0
0.05
1.0
0.8
0.6
0.4
0.2
0.0
P-ME2GE
d(I)/dT
P-ME3GE
d(I)/dT
a
b
30
0.00
0.00
-0.05
-0.10
-0.05
-0.10
10
40°C
56°C
)
C
°
(
-0.15
0.05
e
r
u
t
a
r
e
p
-0.15
0.05
24
32
40
48
56
64
72
m
24
32
40
48
56
64
72
e
T
Temperature (°C)
Temperature (°C)
e 1.0
f
c
d
1.0
0.8
0.6
0.4
0.2
0.0
20
10
0
P-ME3GE
45°C
20
10
0
100
80
60
40
20
0
P-ME2GE
d2(I)/dT2
100
80
60
40
20
0
d2(I)/dT2
P-ME2GE
d(Tr)/dT
P-ME3GE
57℃
57°C
36℃
0.8
0.6
0.4
0.2
0.0
0.00
d(Tr)/dT
0.00
54°C
37°C
-0.05
-0.10
-0.15
-0.05
-0.10
-0.15
-10
-20
-30
-40
-10
-20
-30
-40
45℃
67℃
24
32
40
48
56
64
72
24
32
40
48
56
64
72
20
30
40
50
60
70
35
45
55
65
75
Temperature (°C)
Temperature (°C)
Temperature (°C)
Temperature (°C)
Figure 4. The relationship between fluorescence intensity at 464 nm with
temperature. (a) P-ME2GE and (b) P-ME3GE. Inset: fluorescence photos at
corresponding temperature. The first-order (c and d) and second-order (e
and f) derivatives of temperature-dependent FL intensity curves for
P-ME2GE (Mn = 6400 g mol-1) and P-ME3GE (Mn = 7300 g mol-1), respective-
ly. Fluorescence intensity at 464 nm. Concentration: 0.5 mg mL-1. λex=321
nm.
Figure 5. Hydrodynamic diameters of P-ME2GE (a) and P-ME3GE (b) in
aqueous solution at different temperatures determined by DLS. Concen-
tration: 0.5 mg mL-1. Temperature-dependent transmittance of aqueous
solutions of P-ME2GE (c) and P-ME3GE (d) at 500 nm with the first-order
derivative of the corresponding curves.
sults were consistent with the above temperature-dependent FL
intensity study.
To explore more details about the thermal-induced phase
transition of P-MEnGE, we performed the first-order and
second-order derivatives of the temperature-dependent FL
intensity curves (Figure 4c, d, e, f). The minimum value of the
first-order derivative represented the temperature at which the
FL intensity changed most significantly, which is 40 °C and 55 °C
for P-ME2GE and P-ME3GE, respectively. Meanwhile, there were
minimum and maximum in the second derivatives owing to the
rapid decrease in fluorescence intensity,[46] which was related to
the thermal-induced phase transition of the polymers. The
aqueous solution of thermoresponsive polymers with LCST could
show cloud point on heating procedure. We defined 37 °C and
54 °C as the cloud point for P-ME2GE and P-ME3GE respectively.
At the minimum temperature, the OEG side chains of P-MEnGE
Common temperature-dependent optical transmittance tests
were also conducted to further confirm the thermal transition
properties of P-MEnGE (n= 2, 3) (Figure 5c, d). According to UV-vis
spectra of P-MEnGE in aqueous solution (Figure S15), we chose
500 nm to measure the transmittance of polymer solution in or-
der to avoid the interference of TPE absorption. The transmit-
tance of solution dropped rapidly until it reached zero. The
first-order derivative of transmittance curves displayed a sharp
inverted peak, indicating a thermal transition temperature of the
polymers. The temperature variation range of 36 to 45 °C in
P-ME2GE was in good agreement with the fluorescence results
(37~45 °C). However, the result of P-ME3GE deviated from the
fluorescence data, which might be attributed to the fact that the
4
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Self-Reporting Biodegradable CO2-based Polycarbonates for the Visualization of Thermoresponsive Behavior
Chin. J. Chem.
influence of molecular motion on TPE fluorescence intensity was
more obvious at high temperature.[49]
importance. First, it enables polymer with controlled molecular
weight from 6400 to 17100 g mol-1 for P-ME2GE and 7500 to
17900 for P-ME3GE by regulating the feeding ratio of M/I. Second,
the AIE attributes of TPE-OH realized the fluorescence
self-reporting of the thermoresponsive transition of polymers
according to the intramolecular mobility-dependent fluorescence.
The self-assemble of TPE-labeled polymer in aqueous solution
resulted in fluorescence enhancement owing to the RIM mecha-
nism of TPE. Through temperature-dependent fluorescence in-
tensity study, the cloud points of P-ME2GE and P-ME3GE were
determined to be 37 and 54 °C, respectively. The derivative analy-
sis of the fluorescence intensity curve revealed the whole thermal
transition process with temperature owing to the dehydration of
OEG units. The present study may provide a self-reporting meth-
od to visualize the thermal transition process of biodegradable
thermoresponsive polymers.
To further investigate the micro-changes of P-MEnGE during
1
thermal-induced phase transition, H-NMR measurement were
conducted in D2O at various temperatures. Figure 6 shows the
1H-NMR spectra of P-ME2GE in D2O during the heating process
from 25 to 50 °C. All spectra were measured under the same pa-
rameters and the signal of water at 4.79 ppm was taken as inter-
nal reference. At low temperature (25~30 °C), the signals assigned
to OEG units
(3.20-3.80 ppm) were strong and clear, indicating the flexible
movements of the protons in OEG side chains.[50] At high temper-
ature (36-50 °C), the proton peaks became broader. It means that
the mobility of protons were restricted because of polymer’s col-
lapse by the dehydration of OEG side chains.[51] This result was in
consistent with the thermal transition behavior measured by flu-
orescence and transmittance methods. However, an opposite
variation trend was observed in TPE moiety. At low temperature
(25~30 °C), the proton peaks of TPE remained broad, while the
peaks split into multiple peaks at high temperatures (36-50 °C),
which was resulted from the enhanced intramolecular motion of
TPE with temperature. The downfield-shifted proton peaks both
in OEG and TPE moieties were possible due to the gradual break-
Experimental
All the experimental details are provided in supporting infor-
mation.
1
down of polymer-water hydrogen bonds.[52] The H-NMR spectra
Supporting Information
of P-ME3GE also display similar variation pattern (Figure S16).
These results confirmed the special role of TPE in fluorescence
self-reporting the thermal transition process of polymers.
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2021xxxxx.
Acknowledgement
50℃
45℃
The authors acknowledge the financial support from Funda-
mental Science Center projector in National Natural Science
Foundation of China (Grant No. 51988102), and Key Research
Program of Frontier Sciences, CAS (Grant No. QYZDJ-SSW-JSC017).
The authors also thanks Prof. Anjun Qin and Dr. Han Zhang in
South China University of Technology for performing tempera-
ture-dependent fluorescence spectrometer.
40℃
36℃
30℃
References
OEG
TPE
25℃
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To investigate the degradability of P-MEnGE, the in vitro hydro-
lytic degradation of P-ME2GE (Mn=6400 g mol-1) was carried out in
an aqueous solution at room temperature with a concentration of
0.5 mg mL-1. The process of degradation was observed by 1H NMR
spectra in D2O. As shown in Figure S17, the characteristic peaks at
4.95, 4.54 and 4.30 ppm belonging to cyclic carbonates were ob-
served after 15 days, which indicated that the polymer has been
partially degraded. The polymers with similar structures to
PC-MEnGE also showed good degradability in neutral pH condi-
tion.[31] This result suggested the potential applications of
P-MEnGE in biodegradable materials.
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Entry for the Table of Contents
Construction of Self-Reporting Biodegradable CO2-based Poly-carbonates for the Visualization of Thermoresponsive Behavior with Aggrega-
tion-Induced Emission Technology
Molin Wang, Enhao Wang, Han Cao, Shunjie Liu,* Xianhong Wang,* and Fosong Wang
Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
1.0
1.0
P-ME2GE
P-ME3GE
0.8
0.6
0.4
0.2
0.0
0.8
0.6
0.4
0.2
0.0
30℃
40℃
50℃
60℃
24
32
40
48
56
64
72
24
32
40
48
56
64
72
Temperature (°C)
Temperature (°C)
Thermoresponsive polymers with simultaneous biodegradability and signal “self-reporting” outputs that meet for advanced applications are hard to
obtain. In this work, we developed fluorescence signal “self-reporting” biodegradable thermoresponsive polycarbonates through the copolymerization
of CO2 and OEG-functionalized epoxides in the presence of hydroxyl-modified tetraphenylethylene (TPE-OH). The self-assemble of TPE-labeled poly-
mer in aqueous solution resulted in fluorescence enhancement owing to the restriction of intramolecular motion mechanism of TPE. Further research
indicated that temperature-controlled aggregation and dissociation of TPE moieties are the main reason for fluorescence intensity variations.
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
This article is protected by copyright. All rights reserved.
www.cjc.wiley-vch.de
8