Photoorganocatalyzed Reversible-Deactivation Alternating Copolymerization of Chlorotrifluoroethylene and Vinyl Ethers under Ambient Conditions: Facile Access to Main-Chain Fluorinated Copolymers

Article abstract of DOI:10.1021/jacs.0c01016

Fluoropolymers have found broad applications for many decades. Considerable efforts have focused on expanding access toward main-chain fluorinated polymers. In contrast to previous polymerizations of gaseous fluoroethylenes conducted at elevated temperatures and with high-pressure metallic vessels, we here report the development of a photoorganocatalyzed reversible-deactivation radical alternating copolymerization of chlorotrifluoroethylene (CTFE) and vinyl ethers (VEs) at room temperature and ambient pressure by exposing to LED light irradiation. This method enables the synthesis of various fluorinated alternating copolymers with low ? and high chain-end fidelity, allowing an iterative switch of the copolymerization between ON and OFF states, the preparation of fluorinated block alternating copolymers, as well as postsynthetic modifications.

Full text of DOI:10.1021/jacs.0c01016

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Article
Photoorganocatalyzed Reversible-Deactivation Alternating
Copolymerization of Chlorotrifluoroethylene and Vinyl Ethers under
Ambient Conditions: Facile Access to Main-Chain Fluorinated Copolymers
Kunming Jiang, Shantao Han, Mingyu Ma, Lu Zhang, Yucheng Zhao, and Mao Chen
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.0c01016 • Publication Date (Web): 30 Mar 2020
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Photoorganocatalyzed Reversible-Deactivation Alternating Copoly-
merization of Chlorotrifluoroethylene and Vinyl Ethers under Ambi-
ent Conditions: Facile Access to Main-Chain Fluorinated Copolymers
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Kunming Jiang, Shantao Han, Mingyu Ma, Lu Zhang, Yucheng Zhao and Mao Chen*
State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan Univer-
sity, Shanghai, China, 200433
ABSTRACT: Fluoropolymers have found broad applications for many decades. Considerable efforts have focused on expand-
ing accesses toward main-chain fluorinated polymers. In contrast to previous polymerizations of gaseous fluoroethylenes
conducted at elevated temperatures and with high-pressure metallic vessels, we here report the development of a photoor-
ganocatalyzed reversible-deactivation radical alternating copolymerization of chlorotrifluoroethylene (CTFE) and vinyl
ethers (VEs) at room temperature and ambient pressure by exposing to LED light irradiation. This method enables the syn-
thesis of various fluorinated alternating copolymers with low Ð and high chain-end fidelity, allowing iterative switch of the
copolymerization between “ON” and “OFF” states, the preparation of fluorinated block alternating copolymers, as well as post-
synthetic modifications.
tions, and would give rise to different reactivities and un-
predictable copolymer sequence. In addition, the Cl atoms
INTRODUCTION
Fluoropolymers, endowed with outstanding properties
such as thermal stability, chemical inertness, excellent
weatherability and low surface energy, have found their use
in many high-end applications.1, 2 However, lots of fluori-
nated homopolymers possess high crystallinity, hindering
their processability. Copolymerization is an effective means
to regulate the crystallinity and solubility without losing the
intrinsic advantages of fluoropolymers.3, 4 Examples include
commercialized products of Halar,5 Lumiflon6 and Tefzel,7
all of which have been synthesized via copolymerization of
fluoroethylene and other comonomers. Meanwhile, the in-
corporation of comonomers enables facile regulation of pol-
ymers’ chemical structures and physical properties.3, 8
on the growing copolymers could act as initiating sites or
undergo chain transfer reactions under metal-catalyzed or
harsh conditions.21-23 Consequently, a number of synthetic
limitations including the requirement of metal catalysts24 or
60Co γ-ray irradiation25 in the reaction process, as well as
poor chain-end fidelity, broad molecular weight distribu-
tion (MWD) at high monomer conversion, remain issues to
be overcome.
Recently, the employment of photoredox catalysis in
RDRPs,26-32 cationic polymerizations33-35 and ring-opening
metathesis polymerizations36 has enabled spatiotemporally
controlled chain growth exposing to light irradiation.37-39
However, a photo-controlled (co)polymerization of CTFE
has not been achieved yet. We envision that a photoorgano-
catalyzed approach could provide opportunities to improve
the livingness of chain-growth and decrease side reactions
by implementing control through the photoredox singe-
electron-transfer mechanism31-34 under mild conditions.
Meanwhile, the controlled copolymerization of CTFE under
operationally simple conditions could not only facilitate the
access towards a variety of fluoropolymers, but also allow
the investigation of amorphous materials that would re-
solve the crystallinity problem of the homopolymer coun-
terpart, which might shed light on rational design of poly-
meric materials (for example, solid polymer electrolytes
(SPEs))40, 41 derived from the particularly interesting per-
formance of fluoropolymers.42, 43
Precise polymer synthesis enables engineering of tailored
materials at the molecular level for specific properties that
are suitable for various applications.9-11 While the develop-
ment of reversible-deactivation radical polymerization
(RDRP) has been demonstrated to be particularly effective
for acrylates and styrene,9-11 the transformation of fluoro-
ethylene (i.e., chlorotrifluoroethylene (CTFE),12 which con-
stitutes the backbone of Halar and Lumiflon, to name a few)
through a controlled pathway remains a significant chal-
lenge.13, 14 Considerable research efforts have been devoted
to synthesize copolymers of CTFE,15-19 however, owing to its
low boiling point,20 the synthetic routes typically require
o
high pressure at elevated temperatures (80 to 250 C),
which limits the broad accessibility of related products.
Apart from the harsh conditions, the intrinsic characteristic
of copolymerization poses challenges on regulation of the
precise chain-growth since the copolymer chain-ends could
connect with different comonomers during iterative initia-
Herein we report the development of a photoorganocata-
lyzed reversible-deactivation radical alternating copoly-
merization of CTFE and vinyl ethers (VEs) for the first time
(Scheme 1). Specifically, the synthetic advances of this
method include: (1) the facile transformation of CTFE and
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VEs in an alternating fashion achieved under ambient pres-
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at the excited state of F-PTH is more positive than PTH
(EƟ(PC●+/PC*) = -1.87 V vs -2.03 V) as caused by the elec-
tron-withdrawing substituent, F-PTH is reductive enough
to react with thiocarbonylthio CTAs mostly employed in
photoinduced electron transfer-reversible addition-frag-
mentation chain transfer (PET-RAFT) polymerization.47 Ad-
ditionally, F-PTH exhibits reversible voltammetric cycles at
different scan rates (Figure S6), indicating that the oxida-
tion is highly reversible and the resulting PC•+ is stable.
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sure and temperature without metal-contamination con-
cern; (2) the controlled access to various main-chain fluori-
nated materials with low Ð and high chain-end fidelity at
high VE conversions; (3) the iteratively switching of copol-
ymerization between “ON” and “OFF” states for a gaseous
monomer enabled by using light as an external trigger; (4)
the unprecedented capability in expanding the synthetic
scope to overall fluorinated block alternating copolymers,
and in facile post-synthetic modifications. Overall, this
method emerges as a simple and effective approach for the
controlled synthesis of main-chain fluorinated alternating
copolymers, which creates new possibilities to access func-
tional materials.
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Scheme 1. Photoorganocatalyzed reversible-deactiva-
tion radical alternating copolymerization of CTFE and
VEs.
RESULTS AND DISCUSSION
Scheme 2. Chemical Structures of A) Catalyst, B) Chain-
Transfer Agents and C) Comonomers used in this study.
Figure 1. Optimization for the photoorganocatalyzed copoly-
merization of CTFE and EVE with CTA 1-4.
[CTFE]/[EVE]/[CTA]/[F-PTH] = 60/40/1/0.05, 410 nm purple
LED, 25 °C, ambient pressure. A) EVE conversions. B) molecu-
lar weights (Mn) and Ɖ results of copolymers, filled blue
squares represent Mn by SEC, empty blue squares represent Mn
calculated based on monomer conversions.
Using F-PTH as a PC, we investigated the copolymeriza-
tion of CTFE and EVE in the presence of a series of xanthates
(CTA 1a to 1d, Scheme 1B & 1C) in diethyl carbonate sol-
vent using a 13 W purple LED bulb as a light source (emis-
sion at 410 nm, Figure S7). While xanthates have shown
good control in RAFT copolymerization of CTFE and VEs un-
der thermal conditions as reported by Kamigaito, Ladmiral
and co-workers,19 as well as 60Co γ-ray irradiated copoly-
merization by the Bai group,25 the employment of xanthates
under photoredox conditions generated copolymers of un-
satisfactory control (Ð = 1.42-1.60, Figure 1B, Table S1);
though, moderate to high conversions (59-95%, Figure 1A)
were obtained. Then, we focused on tuning the structure of
CTAs in order to modulate its reactivity. We observed that a
Preliminary investigations on copolymerization con-
ditions. At the beginning of the investigation, we employed
non-fluorinated PCs [i.e., perylene and 10-phenylphenothi-
azine (PTH)] in the photopolymerization of CTFE and vinyl
ethyl ether (EVE). However, emulsions were generated, and
broad MWDs (Ð ~ 1.5-1.8) of the resulted copolymers were
detected by size-exclusion chromatography (SEC). Instead,
we synthesized fluorinated PC (F-PTH, Scheme 1A, Scheme
S1 and Figures S1-S3) based on PTH.44-46 In comparison to
PTH, F-PTH possesses a redshifted absorption (λmax = 350 vs
320 nm, Figures S4-S5) and increased molar absorptivity (ε
= 7958 vs 3200 M-1cm-1). Although the reductive potential
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better leaving group, which gives a more stable alkyl radi- conversion, Mn,SEC = 21.1 kDa, Mn,calc = 15.9 kDa and Mn,MALLS
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cal, affords lower monomer conversions than a poorer leav-
ing group. For example, in comparison to CTA 1a, 2a and 3a
(alkyl radical = •CCN(CH3)2), improved conversions (93-
98% vs 53-61%) were obtained with CTA 1d, 2d and 3d (al-
kyl radical = •CH2CN). From CTAs 1 to 3, the employment of
CTA 3d provided the lowest MWD (Ð = 1.39), others gave
MWDs in a range of Ð = 1.42-2.25.
= 14.8 kDa, respectively.
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When CTA 1d, 2d and 3d were analyzed by cyclic voltam-
metry (CV) (Figure S8), CTA 3d exhibits the most positive
onset potential of reduction, suggesting that the NPh2 group
could best facilitate accepting electron from PC* during the
PET process.39 Then, we turned our attention to CTA 4,48
which simultaneously possesses a more positive reductive
potential than CTA 3d (-1.21 vs -1.54 V) and a −CH2CN leav-
ing group. The employment of CTA 4 generated P(CTFE-alt-
EVE) at a complete EVE conversion and high control over
MWD (Ð = 1.21, Mn,SEC = 19.8 kDa). Further modifications
from the optimized reaction conditions including solvents
and light sources resulted in lower monomer conversions
and broad MWDs (Tables S2-S3).
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To further validate the importance of a fluorinated PC, we
employed non-fluorinated PCs instead of F-PTH with CTA 4,
and found that broad MWDs (Ð = 1.49-1.77) at 88-97%
monomer conversions were obtained (Table S4). The copol-
ymerization mixture of CTFE and EVE was characterized
with dynamic light scattering (DLS). The observation of na-
noparticles (343 nm) (Figures S9 and S10) indicated that
the main-chain fluorinated copolymers would be prone to
self-assembly during copolymerization. The n-C8F17 substit-
uent on F-PTH could promote the interaction between PC
and the growing polymer chain by transferring into nano-
particles driven by the fluorine-fluorine interaction, thus
implementing the good control over chain growth.
Reaction kinetics for the alternating copolymeriza-
tion. Next, we investigated the copolymerization process of
CTFE and different VEs under optimized reaction condi-
tions. As shown in Figure 2A, for VEs including EVE, t-butyl-
dimethyl(4-(vinyloxy)butoxy)silane (SiBVE), i-butyl vinyl
ether (IBVE), n-butyl vinyl ether (BVE) and 2-chloroethyl vi-
nyl ether (CEVE), the degrees of polymerization (DPs, Equa-
tions S1 and S2, Tables S5 to S9) increase with exposure
times. Importantly, DPs of both CTFE and VEs are very close
to each other throughout the copolymerization processes,
confirming the alternating chemical structures of the copol-
ymer backbones. Plots of ln([M]0/[M]t) as a function of time
(Figure 2B) exhibit first order kinetics for reactions of dif-
ferent VEs, further demonstrating the high degree of control
obtained in the alternating copolymerization process. Dur-
ing the propagation, molar masses of copolymers increase
with monomer conversions (Figure 2C). The MWDs of all
copolymers maintained within a narrow range of Ð =1.12-
1.29 (Figures S11 to S15), which are particularly good for
main-chain fluorinated copolymers. Although the molar
masses provided by SEC are higher than theoretical results
at high VE conversions (Mn,calc), when measured with a mul-
tiangle laser light scattering (MALLS) detector (Figure S16),
obtained molecular weights (Mn,MALLS) are in a good agree-
ment with the predetermined values. For example, during
the synthesis of P(CTFE-alt-BVE), when BVE reached 90%
Figure 2. Alternating copolymerization of CTFE and VEs ena-
bled by the photoredox catalysis. Points of different colors rep-
resent results obtained with different VEs: SiBVE (green), EVE
(yellow), IBVE (purple), BVE (blue) and CEVE (red).
[CTFE]/[VE]/[CTA 4]/[F-PTH] = 120/80/1/0.05, 25 °C, ambi-
ent pressure. A) Degrees of polymerization (DPs) of CTFE
(filled circle) and VEs (empty circle) versus exposure time. See
the supporting information (Equations S1 and S2) for details of
calculation. B) ln([M]0/[M]t) versus exposure time. [M]0 and
[M]t are the concentrations of VEs at time points 0 and t, re-
spectively. C) Mn and Ð versus % VE conversion, filled squares
represent Mn obtained by SEC, empty squares represent Mn ob-
tained using a MALLS detector.
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Expanding the copolymerization scope and charac-
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the chain-end group. As shown in Figure 3, resonances cor-
responding to protons from Ha to He were clearly observed,
and their integration areas are in a good agreement with the
target structure, revealing that the final repeating unit of co-
polymer is vinyl ether, which is substituted by the dithiocar-
bamate group (Z(CS)S-). The molecular weight calculated
based on the 1H NMR spectrum is close to the Mn,MALLS value
(Mn,NMR = 24.8 kDa, Mn,MALLS = 24.2 kDa, , Mn,calc = 23.9 kDa).
Termination of copolymer with proton will reduce the
chain-end fidelity, giving overestimated molar mass as de-
termined by UV-vis adsorption (Mn,UV-vis).49 When P(CTFE-
alt-CEVE) was characterized by UV-vis instrument, Mn,UV-vis
= 25.1 kDa was obtained, suggesting that the degree of end
group functionality is above 95% (Figures S18 and S19,
Equations S3). The dithiocarbamate terminal groups in
other alternating copolymers have also been observed in
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terization results. With the established copolymerization
method, we turned our attention to the synthesis of a vari-
ety of P(CTFE-alt-VE)s with different molecular weights. As
shown in Table 1, good to excellent VE conversions were
achieved for different combinations of CTFE and VEs upon
visible-light irradiation at low organocatalyst loadings
(0.01-0.05 mol% of monomer). Since ambient temperature
and pressure were employed, conventional low-pressure
glass tubes could be employed as reaction containers in this
method, further facilitating handling gaseous CTFE without
high-pressure metallic devices. For examples described in
Table 1, P(CTFE-alt-VE)s of molecular weights ranging from
2.0 to 31.1 kDa and narrow MWDs of Ð = 1.13-1.32 were ob-
tained at up to >99% VE conversions. SEC profiles of ob-
tained fluoropolymers (Figure S17) were symmetrical and
unimodal without the detection of any shoulder peak, fur-
ther manifesting the well-controlled propagation realized
for each comonomer. When CTA 4 was replaced with CTA
3d under otherwise identical conditions, the photoorgano-
catalyzed copolymerizations of CTFE and different VEs gen-
erated copolymers with decreased control over MWDs (Ð =
1.33-1.51, Table S10).
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corresponding H NMR spectra (Figures S20-S24), indicat-
ing that high chain-end fidelity was achieved with this
method.
Table 1. Photoorganocatalyzed alternating copolymer-
ization of CTFE and VEs.a
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Figure 3. H NMR spectrum of P(CTFE-alt-CEVE) synthesized
via the photoorganocatalyzed copolymerization.
“ON/OFF” switch for the copolymerization of gaseous
CTFE. An attractive advantage of photo-controlled
polymerization is the capability to temporally regulate
chain growth by switching light irradiation between “ON”
and “OFF” states, providing a facile access to tune materials’
properties.38, 39 The ease of handling gaseous monomer en-
abled by this photoredox catalytic method allowed us to re-
alize unprecedently temporal control of copolymerization
based on CTFE, which operation we believe could be further
expanded to other low-boiling-point monomers. During ex-
periments, the reaction displayed good switchability as
demonstrated by three cycles of “ON/OFF” chain growth
(Figure 4), the molecular weights continuously increased
with conversions (Table S11, and the MWDs of copolymers
were kept in a range of Ð = 1.22-1.26).
a[M] = [CTFE]+[VE], [CTFE]/[VE] = 60/40, [CTA 4]/[F-PTH]
= 1/0.05, 25 °C, ambient pressure, conducted with Schlenk
glass tube, 410 nm light irradiation. Conversions are based on
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the H NMR analysis of remaining VEs after reactions. Mn,SEC
c
and Ð measured by SEC. Mn,MALLS measured by MALLS instru-
ment. dMn determined by 1H NMR analysis.
P(CTFE-alt-CEVE) synthesized with this method was
characterized with proton nuclear magnetic resonance
spectroscopy (1H NMR) to analyze the chemical structure of
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same photopolymerization conditions without additional
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photocatalyst. This process generated P(CTFE-alt-EVE)-b-
P(CTFE-alt-CEVE) with satisfactory control over the molar
mass distribution (Mn = 13.6 kDa, Ð = 1.29), and the SEC pro-
file of the copolymer revealed a clear shift of P(CTFE-alt-
EVE) to lower retention time (Figure 6B, black vs blue line),
indicating the good chain-end fidelity of the fluorinated ma-
croinitiator. The incorporation of a second block and the
terminal dithiocarbamate substituent of P(CTFE-alt-EVE)-
b-P(CTFE-alt-CEVE were confirmed by the 1H NMR analysis
(Figures S25).
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Figure 4. Photoredox catalysis enabled external control of co-
polymerization of CTFE and IBVE by switching light between
“ON” and “OFF” states.
When the light irradiation was turned “OFF”, the chain
growth could keep proceeding, which might not be clear to
observe with short “OFF” periods. For example, to shed light
on the fidelity of temporal control in different photo-medi-
ated RDRPs, Hawker, Anastasaki and coworkers demon-
strated that there was no monomer conversion during the
“dark” periods in metal-free atom transfer radical polymer-
ization (ATRP) and PET-RAFT polymerization in compari-
son with Cu-mediated processes recently.50 Then, a longer
“dark” time was employed in our investigation. As shown in
Figure 5, when the light irradiation was switched “OFF” dur-
ing chain growth, the polymerization was immediately
ceased without the observation of any monomer conversion
in the following 10 h. The polymerization could be success-
fully turned “ON” by further exposing the reaction mixture
to light irradiation. During the chain-growth process, the
molecular weights of fluoropolymers improved with mono-
mer conversions. The good temporal control observed in
this metal-free system is consistent with results demon-
strated by others.31, 44, 50
Figure 6. Synthesis and characterization of block alternating
copolymers. A) Synthetic schemes of the two-step photopoly-
merization and post modification. B) SEC profiles of the fluori-
nated block alternating copolymers.
Figure 5. “ON/OFF” temporal control of copolymerization
of CTFE and IBVE with long “OFF” periods.
The fluorinated block copolymers with all alternating
segments have provided versatile and unprecedented ac-
cesses to various fluorinated materials via post-synthetic
modifications. For example, by modifying the chloride
group on the side chain of the P(CTFE-alt-CEVE) block, dif-
ferent functionalities could be incorporated, including the
tetraphenylethylene (TPE) (P1, Mn = 26.3 kDa, Ð = 1.33) and
azide groups (P2, Mn = 14.0 kDa, Ð = 1.31). While the TPE
group could embed the corresponding materials with ag-
gregation-induced emission (AIE) behavior (Figures S27),52
Chain-extension via the photoorganocatalyzed alter-
nating copolymerization and post-synthetic modifica-
tions. To illustrate the synthetic advantage of this method,
we synthesized a main-chain fluorinated block alternating
copolymer51 by a two-step photoorganocatalyzed copoly-
merization process. As shown in Figure 6A, P(CTFE-alt-
EVE) (Mn = 6.1 kDa, Ð = 1.22) was first prepared in the pres-
ence of F-PTH and CTA 4 exposing to 410 nm light irradia-
tion, and subsequently employed as a macroinitiator in the
chain-extension reaction with CTFE and CEVE under the
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(6) a) Lumiflon (FEVE, developed by the Asahi Glass Company) is made
the tailoring of azide group provides opportunities to fur-
ther connect with desirable functionalities via the copper-
catalyzed “click” chemistry.53 The successful conversions of
the chloride substituent into TPE and azide groups were
confirmed by H NMR and FT-IR measurements (Figures
S28-S30).
of alternating copolymers of CTFE and vinyl ethers, offerring ultra-
weatherability and long life cycle for outdoor coatings; b) Scheirs, J.; Burks,
S.; Locaspi, A. Developments in Fluoropolymer Coatings. Trends Polym.
Sci. 1995, 3, 74-82.
(7) Tefzel (ETFE, manufactured by the DuPont Company) is an
alternating copolymer of tetrafluoroethylene and ethylene, exhibitting both
excellent corrosion resistance and mechanical strength.
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(8) Campagne, B.; David, G.; Améduri, B.; Jones, D. J.; Roziere, J.;
Roche, I., Novel Blend Membranes of Partially Fluorinated Copolymers
Bearing Azole Functions with Sulfonated Peek for PEMFC Operating at
Low Relative Humidity: A Study of the Nature of the N-Heterocycle.
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Catalyzed Living Radical Polymerization: Toward Perfection in Catalysis
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(13) Asandei, A. D.; Adebolu, O. I.; Simpson, C. P., Mild-Temperature
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CONCLUSION
We have developed a photoorganocatalyzed reversible-
deactivation alternating copolymerization of CTFE and VEs
with a fluorinated photoredox catalyst, enabling the con-
trolled synthesis of various main-chain fluorinated alternat-
ing copolymers with low Ð and high chain-end fidelity at
high monomer conversions. The synthetic advances of this
method allow smooth transformation of gaseous CTFE at
ambient pressure and room temperature by exposing to
LED light irradiation, and facilitate iteratively switching the
chain growth between “ON” and “OFF” states. Main-chain
fluorinated block alternating copolymers have been suc-
cessfully synthesized via a tandem photoorganocatalyzed
alternating copolymerization, promoting the synthesis of
fluoropolymers with diverse functional side groups. Given
the broad applications of fluoropolymers and photopoly-
merization, as well as tunable physical/chemical properties
of copolymers by selecting appropriate comonomers, we
expect this method to be useful for creating improved op-
portunities to tailored fluorinated copolymers.
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ASSOCIATED CONTENT
(17) Lopez, G.; Thenappan, A.; Améduri, B., Synthesis of
Chlorotrifluoroethylene-Based Block Copolymers by Iodine Transfer
Polymerization. ACS Macro Lett. 2015, 4, 16-20.
(18) Chung, T. C.; Petchsuk, A., Synthesis and Properties of
Ferroelectric Fluoroterpolymers with Curie Transition at Ambient
Temperature. Macromolecules 2002, 35, 7678-7684.
(19) Guerre, M.; Uchiyama, M.; Lopez, G.; Améduri, B.; Satoh, K.;
Kamigaito, M.; Ladmiral, V., Synthesis of PEVE-b-P(CTFE-alt-EVE)
Block Copolymers by Sequential Cationic and Radical RAFT
Polymerization. Polym. Chem. 2018, 9, 352-361.
Supporting Information
The Supporting Information is available free of charge via the
Internet at http://pubs.acs.org.
General experimental considerations, experimental pro-
cedures, NMR spectra, SEC profiles, and additional sup-
porting data
AUTHOR INFORMATION
(20) For CTFE, b.p. = -26.2 C at 760 mmHg.
(21) Tan, S.; Li, J.; Zhang, Z., Study of Chain Transfer Reaction to
Solvents in the Initiation Stage of Atom Transfer Radical Polymerization.
Macromolecules 2011, 44, 7911-7916.
Corresponding Author
*chenmao@fudan.edu.cn
(22) Tan, S.; Liu, E.; Zhang, Q.; Zhang, Z., Controlled Hydrogenation of
P(VDF-co-CTFE) to Prepare P(VDF-co-TrFE-co-CTFE) in the Presence of
CuX (X = Cl, Br) Complexes. Chem. Commun. 2011, 47, 4544-4546.
(23) Valade, D.; Boschet, F.; Améduri, B., Grafting Polymerization of
Styrene onto Alternating Terpolymers based on Chlorotrifluoroethylene,
Hexafluoropropylene, and Vinyl Ethers, and Their Modification into
Ionomers bearing Ammonium Side-Groups. J. Polym. Sci., Part A: Polym.
Chem. 2010, 48, 5801-5811.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
This research was financially supported by the NSFC (no.
21704016, 21971044), start-up funding from Fudan Univer-
sity. We appreciate Prof. Xinrong Lin (Yunnan University) and
Prof. Liming Zhang (Fudan University) for suggestions of ana-
lyzing polymers.
(24) Wang, W.; Yan, D.; Bratton, D.; Howdle, S. M.; Wang, Q.;
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(27) Discekici, E. H.; Anastasaki, A.; Kaminker, R.; Willenbacher, J.;
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