Synthesis of bioderived polycarbonates with adjustable molecular weights catalyzed by phenolic-derived ionic liquids

Article abstract of DOI:10.1039/d0gc00493f

The synthesis of high-molecular-weight bioderived polycarbonates via green routes and regulation of molecular weight is of great significance and is highly challenging. Herein, a green sequential approach toward the synthesis of bio-derived polycarbonates with adjustable molecular weights from isosorbide and dimethyl carbonate (DMC) has been developed by employing ionic liquids (ILs) as a class of eco-friendly catalysts. The structures of IL catalysts can be designed readily to control the molecular weight of isosorbide-derived polycarbonates (PIC), which is an attractive advantage of IL catalysts instead of the conventional metal-containing catalysts. In the presence of the [Bmim][4-I-Phen] catalyst, the PIC weight-average molecular weight (M_w) can reach 50?300 g mol^-1. By the combination of the experimental results and DFT calculations, an IL anion-cation synergistic catalytic polymerization mechanism has been proposed, which reveals the nucleophile-electrophile dual activation by H-bonds and charge-charge interactions in catalyzing the formation of PIC. The significance of this study is that it provides guidance for developing IL catalysts for synthesizing higher molecular weight polycarbonates, thereby conveniently leading to a variety of polymers with tunable properties.

Full text of DOI:10.1039/d0gc00493f

View Article Online
View Journal
Green
Chemistry
Cutting-edge research for a greener sustainable future
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: W. Qian, L. Liu, Z.
Zhang, Q. Su, W. Zhao, W. Cheng, D. Li, Z. Yang, R. Bai, F. Xu, Y. Zhang and S. Zhang, Green Chem., 2020,
DOI: 10.1039/D0GC00493F.
Volume 20
This is an Accepted Manuscript, which has been through the
Number
May 2018
Pages 1919-2160
9
7
Royal Society of Chemistry peer review process and has been
accepted for publication.
Green
Chemistry
Cutting-edge research for a greener sustainable future
rsc.li/greenchem
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1463-9262
PAPER
Paul T. Anastas et al.
The Green ChemisTREE: 20 years after taking root with the 12
principles
rsc.li/greenchem

Please do not adjust margins
Page 1 of 11
Green Chemistry
View Article Online
DOI: 10.1039/D0GC00493F
Green Chemistry
ARTICLE
Synthesis of Bioderived Polycarbonates with Molecular Weight
Adjustability Catalyzed by Phenolic-derived Ionic Liquids
Received 00th January 20xx,
Accepted 00th January 20xx
Wei Qian,a,b Lei Liu,a Zengliang Zhang,a Qian Su,a Weizhen Zhao,a Weiguo Cheng,*a Li Dong,a Zifeng
Yang,a,b Ruibing Bai,a Fei Xu,a Yanqiang Zhang a and Suojiang Zhang*a
DOI: 10.1039/x0xx00000x
Synthesis of high-molecular-weight bioderived polycarbonates via green routes and regulation of molecular weight are of
great significance but also enormous challenges. Herein,
a green sequential approach toward the bio-derived
polycarbonates with adjustable molecular weight from isosorbide and dimethyl carbonate (DMC) has been developed by
employing ionic liquids (ILs) as a class of eco-friendly catalyst. The structures of IL catalysts are capable of being designed
readily to control the molecular weight of isosorbide-derived polycarbonate (PIC), which is an attractive advantage of IL
catalysts instead of the conventional metal-containing catalysts. In the presence of [Bmim][4-I-Phen] catalyst, PIC weight-
average molecular weight (Mw) can reach to 50300 g/mol. By combination of the experimental results and DFT
calculations, an IL’s anion-cation synergistic catalytic polymerization mechanism has been proposed, which reveals that
nucleophile electrophile dual activation by H-bonds and charge-charge interactions in catalyzing PIC formation. Further
importance of this study is that we propose a guidance of developing IL catalysts for synthesizing higher molecular weight
polycarbonates, thereby conveniently preparing a variety of polymers with tunable properties.
polymer building block attributing to its rigidity, chirality, and
11
nontoxicity.10,
Compared with the traditional BPA
Introduction
polycarbonate, isosorbide-derived polycarbonate (PIC) retains
higher heat resistance and preferable UV resistance.12-14
Furthermore, melt polymerization is a preferred approach
circumventing toxic reagents and sophisticated technological
processes.15 However, previous studies were mainly focused
on the melt polymerization of isosorbide with diphenyl
carbonate (DPC) instead of with dimethyl carbonate (DMC).14,
Approach to polymeric materials from bio-derived monomers
and green polymerization processes is currently recognized as
2
an inevitable choice for sustainable development.1,
Of
polymeric materials, polycarbonate is extensively employed
for various engineering fields because of its brilliant
properties, such as high mechanical strength and excellent
transparency.3, 4 However, the traditional synthetic route for
polycarbonate is interfacial or solution polycondensation of
the highly toxic reagent phosgene and the petroleum-based
monomer bisphenol-A (BPA) known for interfering with the
body’s endocrine system.5-9 Hence, it is an insistent demand to
develop green routes and alternative nontoxic bio-based
monomers with equivalent properties for polycarbonate
synthesis.
16-18
Compared with DPC pathway, the DMC route is more
sustainable, which avoids the use of the toxic raw material
phenol.15 Moreover, DMC, a green biodegradable chemical, is
derived from CO2. And the DMC route can achieve at a
relatively lower reaction temperature.19 Therefore, the direct
melt polymerization of isosorbide and DMC can simplify the
reaction steps and reduce the cost and energy consumption.
However, it is a challenging route to manufacture PIC via the
DMC method.20, 21 Because isosorbide is a dihydric alcohol with
weak reactivity.14 Additionally, DMC is difficult to act as a
Isosorbide (1,4:3,6-dianhydro-D-sorbitol, IS), obtained from
starch and cellulose, is considered as a promising biobased
methoxycarbonylating agent for participating in
a
transesterification reaction in the presence of a basic catalyst
at high temperatures.20, 22 These reasons cause the enormous
challenge in synthesizing PIC, particularly high-molecular-
weight PIC.11, 23 Considering the abovementioned factors, the
bottleneck of developing this green route is the catalyst
development. Consequently, only a few metal-containing
catalysts (alkali metal acetylacetonate complexes) have been
developed for the one-pot melt polymerization of isosorbide
a. Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of
Green Process and Engineering, State Key Laboratory of Multiphase Complex
Systems, Innovation Academy for Green Manufacture, CAS, Institute of Process
Engineering, Chinese Academy of Sciences, Beijing 100190 (P.R. China). E-mail:
wgcheng@ipe.ac.cn, sjzhang@ipe.ac.cn
b. School of Chemical Engineering, University of Chinese Academy of Sciences, 19A
Yuquan Road, Shijingshan District. Beijing 100049 (P.R. China).
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
Green Chem., 2013, 00, 1-10 | 1
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 2 of 11
ARTICLE
Green Chemistry
24
and DMC.19, In the presence of the lithium acetylacetone of isosorbide and DMC.37 The phenolic anion could not only
View Article Online
DOI: 10.1039/D0GC00493F
catalyst, the weight-average molecular weight (Mw) of the form H-bonds with the -OH groups of isosorbide, but also act
synthetic PIC can reach to 46500 g/mol under the optimum as a nucleophile activating DMC through interacting with the
conditions.19 However, it is generally known that metal-based C=O groups, thus resulting in the generation of the
catalysts may cause certain damages, for example, methoxycarboxylation products [dicarboxymethyl isosorbide
26
environmental concerns, and corrosions.25,
Besides, the (DC),
2-monocarboxymethyl
isosorbide
(MC-1),
5-
37
screening of the metal-containing catalysts for PIC synthesis monocarboxymethyl isosorbide (MC-2)] (Fig. 1a).22,
without basis leaves PIC molecular weight being randomly Concerning the melt polymerization of isosorbide and DMC,
varied. As a result, it is hopeless to expect that PIC molecular the PIC molecular weight is not only controlled by the
weight could be further enhanced via employing the transesterification stage but also affected by the
abovementioned metal-containing catalysts.
polycondensation stage.19 The polycondensation stage is
mainly the transesterification reaction of the terminal groups
of these methoxycarboxylation products causing the formation
of oligomers, and then the terminal groups of the growing
polymer chains are further reacting with each other
continuously.19, 37 Although the substrates’ structures of the
two stages are different, they all contain -OH groups and
carbomethoxy groups (-OCOOCH3) (Fig. 1a). Therefore,
through modifying the structures of phenolate-based IL’s
anion and cation, it is possible to obtain efficient catalysts for
synthesizing high-molecular-weight PICs. Because the
nucleophilicity of anion and the electrophilicity of cation in IL
could influence each other.38-40
Based on the above viewpoints, we report a one-pot DMC
method for PIC synthesis using phenolic ILs as a promising
class of eco-friendly catalysts, of which the highly toxic
phosgene and the endocrine disruptor BPA are avoided. The
excellent tunability of phenolic IL catalysts’ structure facilitates
the H-bond strength between IL catalyst’s cation or anion and
substrates to vary readily, causing the different catalytic
activity of IL catalysts. As a result, the PIC molecular weight can
be controlled by selecting proper IL catalysts. We also propose
a plausible polymerization mechanism for PIC synthesis in the
presence of phenolic IL catalysts according to the experimental
results, 1H NMR, ESI-MS, MALDI-TOF-MS, and DFT calculations.
Results and discussion
Effect of IL catalysts’ structure on PIC synthesis
In
our
previous
work,
we
developed
trihexyl(tetradecyl)phosphonium 4-substituted phenolic IL
([P66614][4-R-Phen], R = H, F, Cl, Br and I) catalysts for the
transesterification reaction of isosorbide with DMC and the
[P66614][4-I-Phen] catalyst showed the highest catalytic activity
(Fig. 1b).37 However, for the melt polymerization of them, the
substrates’ structures of the two stages are different (Fig. 1a),19
which means that the [P66614][4-I-Phen] catalyst may not be the
best catalyst for the whole reaction process. Thus, it is essential to
investigate the influence of the anions’ and cations’ structures of 4-
substituted phenolic IL catalysts on the polymerization
reaction. For this purpose, a series of 4-substituted phenolic IL
Fig. 1 (a) The melt polymerization of isosorbide and DMC; (b)
The structures of IL catalysts’ cations and anions used in this
work.
Satisfactorily, ILs have been proven to exhibit remarkable
performance in the catalytic field, and are recognized as
potential replacements for metal-containing catalysts
attributing to their highlighted properties of adjustability and
low toxicity.27-34 It was reported that the cation and anion of IL
both could activate substrates.35, 36 Hence, it is significant to
design the structures of IL’s cation and anion to promote the
polymerization reaction of isosorbide and DMC. In our
previous study, we discovered that phosphonium phenolate
ILs were effective catalysts for the transesterification reaction
1
catalysts (Fig. 1b) were synthesized and identified by H NMR
and ESI-MS (see ESI†). Among them, the [P66614][4-R-Phen] (R =
H, F, Cl, Br and I) catalysts were used directly, which were
obtained from our previous work.37 As shown in Fig. S1, these
2 | Green Chem., 2013, 00, 1-10
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 11
Green Chemistry
Please do not adjust margins
Green Chemistry
ILs displayed excellent thermal stability and the corresponding
ARTICLE
factor for the difference of the PIC molecular weight, owing to
View Article Online
DOI: 10.1039/D0GC00493F
temperatures with maximum decomposition rates (Td-max
)
the three methoxycarboxylation compounds with different
reactivity.19 With the catalysis of [P66614][4-I-Phen], the
were all above 200 oC.37
obtained PIC exhibits the highest molecular weight (Mn
=
Table 1 The influence of the structure of IL’s anion on the pre-
polymerization stage
16500 g/mol and Mw = 28400 g/mol) (Fig. 2a). From this point,
we can conclude that a high content of DC is really conducive
to the growth of polymer chains.
ntry
Anion
XIS (%)
SDC (%)
SMC-1 (%)
SMC-2 (%)
1
2
3
4
5
[4-H-Phen]
[4-F-Phen]
[4-Cl-Phen]
[4-Br-Phen]
[4-I-Phen]
94.7
97.0
95.0
96.6
98.8
51.6
68.2
52.7
56.2
82.6
26.3
19.3
25.6
24.8
9.6
22.1
12.5
21.7
19.0
7.8
Reaction conditions: The molar ratio DMC/IS=7.5. Transesterification
time: 3.5 h. Cat. amount is 4.4×10-3 equiv. mol based on IS. XIS denotes
isosorbide conversion at the transesterification stage calculated by GC.
Transesterification products’ selectivities determined by HPLC.
denotes selectivity.
S
Initially, the cation in IL was fixed as the [P66614] cation, of
which the anions were grafting the atoms of H, F, Cl, Br, and I
to the para-position of phenolic ion, respectively. To study the
influence of the composition of transesterification products on
PIC molecular weight, the transesterification time was set to
3.5
h
instead of 13 h.37 Because DC was the main
transesterification product under the condition of excessive
transesterification time.37 The results are listed in Table 1 and
Fig. 2a, indicating that the whole polymerization reaction can
be catalyzed effectively by the phenolate-based ILs. Moreover,
the typical 1H NMR spectra of the different stages of the
isosorbide moiety construction change obviously with the
reaction process, implying the growth of polymer chains (Fig.
1
S2). The GPC results are consistent with the H NMR analysis
and indicate that the molecular weight of PIC (Mn and Mw) is
also changed with the variation of phenolic anion structure
(Fig. 2a and Table S1). This can be explained as follows. The
different IL’s anion structure leads to the variation of the
nucleophilicity of 4-substituted phenolic anion in IL. As
reported by our previous work, the O atom of the phenolic
anion can form H-bond interactions with the -OH groups in
isosorbide.37 Thus, the change of IL’s anion structure could
result in the variation of the H-bond strength. For instance, the
bond lengths of H-bond are 1.538, 1.539, and 1.557 Å for [4-H-
Phen], [4-F-Phen], and [4-I-Phen], respectively.37 Furthermore,
the halogen group could undertake the negative charge of the
oxygen atom of phenolic anion, improving the halogen-oxygen
interaction of phenolic anion with isosorbide.41-43 Naturally,
when IL catalyst has a different anion structure, the proportion
of the transesterification products (DC, MC-1, and MC-2) is
also different at the same reaction condition (Table 1). At the
transesterification stage, the catalytic activity order of
[P66614][4-R-Phen] catalysts (R = H, F, Cl, Br and I) is consistent
with our previous work.37 At the polymerization stage, the
different contents of various PIC precursors are a significant
Fig. 2 PIC molecular weight catalyzed by IL catalysts (a) cation fixed
as [P66614] and the anions with different structures; (b) anion fixed
as [4-I-Phen] and the cations with different structures.
Obviously, [4-I-Phen] is an appropriate anion in this
polymerization reaction according to the above experimental
results. So, does the cation have a significant effect on this
reaction? For this purpose, the effect of IL’s cation structure on
the PIC molecular weight was discussed. As illustrated in Fig.
2b and Table S1, the structure of IL’s cation also has a great
influence on PIC molecular weight. With the presence of
[Bmim][4-I-Phen], the Mn and Mw can attain to 23400 g/mol
and 39600 g/mol, respectively. When IL’s cation structure
involves [P66614] or [N4444], the proportion of DC is obviously
more than that catalyzed by [Bmim][4-I-Phen] (Table 2, entry
1-2, 6). However, the molecular weight of PIC catalyzed by the
IL catalyst including [P66614] or [N4444] is lower than that
catalyzed by [Bmim][4-I-Phen]. It means that a high proportion
of DC is a prerequisite but not the unique factor in synthesizing
high-molecular-weight PIC. One possible reason is that [P66614
]
This journal is © The Royal Society of Chemistry 20xx
Green Chem., 2013, 00, 1-10 | 3
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 4 of 11
ARTICLE
Green Chemistry
or [N4444] cation has a long alkyl chain, resulting in an increase 7.5, the Mn and Mw of PIC gradually decrease to V1ie4w4A0rt0icleg/Omnlinoel
DOI: 10.1039/D0GC00493F
of steric hindrance interacting with the bulky carboxymethyl and 23800 g/mol (DMC/IS molar ratio: 15), respectively. To the
moiety of methoxycarboxylation products (DC, MC-1 or MC- best of our knowledge, no one has made a clear explanation
2).44 Consequently, its catalytic activity of polycondensation for this phenomenon. To solve this puzzle, the selectivity of
stage could be weaker than that of [Bmim][4-I-Phen]. This can intermediate products (DC, MC-1, MC-2) and isosorbide
be proved by the DFT calculations below. The protic ILs conversion were analyzed (Fig. 4). With the increase of DMC/IS
([DBNH][4-I-Phen], [DBUH][4-I-Phen], and [TMGH][4-I-Phen]) molar ratio, the amount of DC in the total transesterification
present inferior catalytic activity in the prepolymerization products is significantly enhancing and that of MC-1 (MC-2) is
stage, leading to the low conversion of isosorbide and the low considerably reducing (Fig. 4a). After DMC/IS molar ratio
contents of prepolymers (Table 2, entry 3-5). As a result, the reaching to 7.5, the increase of isosorbide conversion is not
PIC molecular weight is lower than that catalyzed by aprotic ILs apparent. These results reveal that the PIC molecular weight is
(Fig. 2b). According to previous literature,45, 46 generally, the not always increasing with the DC amount enhancement.
ability to form H-bond of protic IL is stronger than that of Similarly, the influence of transesterification time is consistent
aprotic IL. Therefore, the inferior catalytic activity of protic ILs with the above result (Fig. 3b and 4b).
could be related to the fact that the proton of IL’s cation can
form strong H-bond interactions with the oxygen atom of C=O
in DMC and is difficult to disintegrate from the complex. Thus,
it makes methoxycarboxylation products difficult to generate,
especially, DC (Table 2, entry 3-5). The results of DFT
calculations, given below, can verify the abovementioned
deduction. Next, further investigations were carried out
utilizing the [Bmim][4-I-Phen] catalyst.
Table 2 The influence of the structure of IL’s cation on the pre-
polymerization stage
Entry
Cation
[P66614
XIS (%)
98.8
98.1
44.9
43.6
3.2
SDC (%)
SMC-1 (%)
9.6
SMC-2 (%)
7.8
1
2
3
4
5
6
]
82.6
[N4444
]
70.8
16.2
72.6
74.6
80.0
25.3
13.0
27.4
25.4
20.0
20.9
[DBNH]
[DBUH]
[TMGH]
[Bmim]
-
-
-
96.6
53.8
Reaction conditions: The molar ratio DMC/IS=7.5. Transesterification
time: 3.5 h. Cat. amount is 4.4×10-3 equiv. mol based on IS. XIS denotes
isosorbide conversion at transesterification stage calculated by GC.
Transesterification products’ selectivities determined by HPLC.
denotes selectivity.
S
Fig. 3 Effect of (a) molar ratio of DMC to isosorbide; (b)
transesterification time on PIC molecular weight catalyzed by
[Bmim][4-I-Phen].
Effect of prepolymer composition on PIC synthesis
Undoubtedly, [Bmim][4-I-Phen] is a proper IL catalyst in this
polymerization reaction according to the abovementioned
experimental results. Then, does the proportion of
prepolymers have a significant effect on PIC molecular weight?
To this end, the influences of DMC/IS molar ratio and the
transesterification time on the polymerization reaction were
interrogated with the catalysis of [Bmim][4-I-Phen],
respectively. As depicted in Fig. 3a, the molar ratio of DMC to
isosorbide indeed has an important impact on the PIC
molecular weight. When the DMC/IS molar ratio increases
from 1.5 to 7.5, the PICs Mn and Mw increase from 9600 g/mol
and 18100 g/mol to 23400 g/mol and 39600 g/mol,
respectively. However, as the DMC/IS molar ratio exceeding
Interestingly, it seems to mean that an excessive amount of
high reactive DC has a negative effect on the PIC molecular
weight. The most plausible reason is that DC is more prone to
occur
a decarboxylation reaction at high temperatures.
Decarboxylation reactions could indeed occur for some dialkyl
carbonates at high temperatures in the presence of catalysts.47
For supporting this hypothesis, TG-MS and 1H NMR
spectroscopy were employed. As exhibited in Fig. S3a, TG-MS
curves demonstrate that DC, MC-1, and MC-2 all can release
CO2 (m/z 44) at 190 oC. Furthermore, as shown in Fig. S3b and
1
Fig. S4, the H NMR spectra indicate that DC, MC-1, and MC-2
4 | Green Chem., 2013, 00, 1-10
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 11
Green Chemistry
Please do not adjust margins
Green Chemistry
ARTICLE
all can undergo methylation at a high temperature (the single polycondensation temperature was too hiVgiehw Aroticrle Ontlhinee
peak at about 3.4 ppm belongs to the hydrogen in methoxy polycondensation time was too long.14 Through conditional
DOI: 10.1039/D0GC00493F
group -OCH3 of isosorbide moiety according to the previous optimization, the maximum molecular weight of PIC is Mn =
report).22 Hence, the carbomethoxy group (-OCOOCH3) of DC 28500 g/mol and Mw = 50300 g/mol (Fig. S5).
(MC-1 or MC-2) could suffer methylation in the presence of a
catalyst, which leads to -OCOOCH3 transforming into -OCH3
and releasing CO2 at the same time. Additionally, the end -
OCH3 could cause the polymer chain to be terminated. Thus,
excessive content of DC is easier to terminate the polymer
chain growth, on account of that DC has two -OCOOCH3
groups. Consequently, an excessive amount of high reactive
DC has a negative effect on the PIC molecular weight. The
optimum proportion of prepolymers for PIC synthesis depends
on reaction conditions and catalyst type.
Fig. 5 Typical (a) 1H NMR, and (b) 13C NMR spectra of PIC prepared
by [Bmim][4-I-Phen].
PIC structure characteristic and thermal properties
The structure characteristic of the synthesized PIC, catalyzed
1
by [Bmim][4-I-Phen], was identified by H NMR and 13C NMR
1
spectra (Fig. 5). From the H NMR spectra, the proton signals
of repeating unit and the terminal groups (-OH, -OCOOCH3,
and OCH3) could be identified (Fig. 5a), which are completely
in conformity with the previous literature.19, 48 From proton
signals of the terminal groups, the relative contents of various
terminal groups could be determined.
Taking the effect of the polycondensation temperature as an
Fig. 4 Effect of (a) molar ratio of DMC to isosorbide; (b)
transesterification time on IS conversion at transesterification
stage and prepolymers’ selectivities.
example, the relative contents of terminal groups change
obviously with the polycondensation temperature increasing.
Subsequently, to explore the maximum molecular weight of
With the growth of molecular weight, the content of the
PIC in the presence of [Bmim][4-I-Phen], we also studied the
terminal -OH increases and the amount of the terminal -
influences of polycondensation temperature and time on the
polycondensation reaction under the optimum prepolymer
composition (Fig. S5). A high polycondensation temperature is
indispensable to reduce melt viscosity for polymer chain
growth.15 However, the thermal degradation of PIC and side
OCOOCH3 decreases (see Table 3 and Fig. S5a). This is because
the reactivity of the terminal -OCOOCH3 is higher than that of
the terminal -OH,19 which leads to the terminal -OCOOCH3
participating in polycondensation faster. Additionally, the
reduction of the terminal -OCOOCH3 amount is also related to
reactions would play
a
dominant role when the
This journal is © The Royal Society of Chemistry 20xx
Green Chem., 2013, 00, 1-10 | 5
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 6 of 11
ARTICLE
Green Chemistry
the decarboxylation reaction of the -OCOOCH3. As shown in that the influence of polycondensation temperature on PIC
View Article Online
DOI: 10.1039/D0GC00493F
Fig. S6, the decomposition temperatures at 5% weight loss (Td- molecular weight is pronounced. Therefore, the thermal behaviors
5%) of DC and the PIC sample are about 180 oC and 313 oC, of these PIC samples were evaluated by the TGA and DSC analyses
respectively, which means that the thermal stability of the PIC (Fig. S7). These PIC samples all display a one-step decomposition
sample is higher than DC. The -OCOOCH3 group turns to be process (Fig. S7a). Moreover, the decomposition temperature of
stable at the end of long polymer chains. As a result, the these PIC samples at 5% weight loss (Td-5%) and the thermostability
content of -OCOOCH3 is higher than that of -OCH3 (Table 3). Due of PIC can be improved with the increasing of PIC molecular weight
o
to the steric effect, the catalyst tends to attack the terminal (Fig. S7a, c and Table S2). For instance, Td-5% enhances from 314 C
o
exo-OCOOCH3 easier than endo-OCOOCH3, which leads to the to 345 C, with the Mn and Mw of PIC increasing from 11500 g/mol
exo-OCOOCH3 to be consumed faster in the polycondensation and 23800 g/mol to 24800 g/mol and 45100 g/mol. When the
reaction.49 Meanwhile, the decarboxylation reaction of the molecular weight is high enough, Td-5% increases slowly.19 The DSC
terminal -OCOOOCH3 occurs continuously at high curves reveal that these PIC samples are all amorphous state
polycondensation temperature. As a result, the ratio of the because of the absence of a single sharp molten peak. This result is
terminal endo-OCH3/exo-OCH3 is also always more than 1 perfectly consistent with the information provided by the 13C NMR
(Table 3). We also discover that the ratio of the terminal endo- spectra. Glass transition temperature (Tg) of PIC also tends to be
OH/exo-OH is always greater than 1.5, which could be high with increasing PIC molecular weight, for example, the Tg
attributed to the reason that the reactivity of the terminal enhances from 128 oC to 160 oC, with the Mn and Mw of PIC
endo-OH and exo-OH are non-identical.10 This is similar to that increasing from 11500 g/mol and 23800 g/mol to 28500 g/mol and
the molar ratio of MC-1/MC-2 is always greater than 1 (Table 1 50300 g/mol (Fig. S7b-c and Table S2). These results indicate that
and 2).37
PIC has excellent heat resistance.
Table 3 The influence of polycondensation temperature on the
relative contents of terminal groups of PIC
Possible polymerization mechanism
Although a possible mechanism has been proposed for the
transesterification reaction of isosorbide and DMC catalyzed
by quaternary phosphonium phenolate ILs in our previous
Terminal groups (%)
Entry
PT (oC)
-OH
-OCH3
endo
-OCOOCH3
work,37
the
polymerization
mechanism
of
the
polycondensation stage is still unclear. Herein, a plausible
exo
endo
exo
anion-cation synergistic catalytic polymerization mechanism
37, 50
was proposed according to the previous report,14,
the
1
2
3
4
5
6
7
180
220
230
250
260
270
280
11.2
15.1
19.2
18.5
19.4
22.7
20.6
18.1
23.0
27.3
29.0
29.2
34.8
36.8
1.1
1.1
1.3
1.2
1.9
2.0
1.5
2.0
2.9
3.0
3.5
5.1
4.5
5.4
67.6
57.9
49.2
47.9
44.4
35.9
35.8
experimental results, and DFT calculations (Scheme 1). As
mentioned above, the polycondensation stage is mainly the
transesterification reaction of methoxycarboxylation products
(DC, MC-1, and MC-2) causing the formation of oligomers, and
then the growing polymer chains are reacting with each other
continuously. The 1H NMR spectra were employed for
investigating the interactions of methoxycarboxylation
products with [Bmim][4-I-Phen]. The C-2 hydrogen of the
[Bmim] cation was anticipated to accelerate electrophilic
activation of DC through an H-bond, which was similar to the
previous literature.14, 50 This inference was supported by the C-
2 hydrogen signal of the [Bmim] cation shifting from δ 9.30 to
9.15 ppm, when the molar ratio of [Bmim][4-I-Phen] to DC
decreased from 1:0 to 1:4 (see Fig. S8a). Simultaneously, the
proton of [4-I-Phen] anion moved from δ 7.03 and 6.17 ppm to
7.21 and 6.40 ppm (see Fig. S8b). This was contrary to the
Reaction conditions: DMC/IS=7.5. Transesterification time: 3.5 h.
Polycondensation time: 4 h. Cat. amount is 4.4×10-3 equiv. mol based
on IS. The relative amount of terminal groups determined by 1H NMR.
The peak integration at δ 4.87 ppm in a repeating unit normalized to be
1. PT denotes polycondensation temperature. Total -OH = exo-OH +
endo- OH; Total -OCH3= exo- CH3 + endo- OCH3
As presented in Fig. 5b, the peaks of the 13C NMR spectrum are in anticipated downfield shift of the C-2 hydrogen of [Bmim]
good accord with the carbon atoms of the PIC repeating unit.14 The cation and upfield shift of the hydrogen of [4-I-Phen] anion
signals of carbonates in the PIC repeating units can be detected at induced by forming a new H-bond, which ascribed to the
154.0, 153.6 and 153.3 ppm and the relative peak ratio of them is strong intramolecular H-bonds in IL substituted by the
1:2:1, which are attributed to the three connection modes of endo- relatively weak H-bonds of the C-2 hydrogen of [Bmim] cation
51, 52
endo (a1), endo-exo (a2) and exo-exo (a3), respectively, suggesting with the oxygen of C=O in DC.14,
Additionally, the
PIC is a random polymer.48
interactions of MC-1 or MC-2 with [Bmim][4-I-Phen] were also
Thermal properties are of great significance for the processing explored, respectively. As expected, the oxygen of C=O in MC-
and application of polymers. The results mentioned above indicate 1 could also form an H-bond with the C-2 hydrogen of [Bmim]
6 | Green Chem., 2013, 00, 1-10
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 11
Green Chemistry
Please do not adjust margins
Green Chemistry
ARTICLE
cation, which made carbon of C=O more susceptible to be not be probed, suggesting the endo-OH in MC-1 could also be
View Article Online
DOI: 10.1039/D0GC00493F
attacked. This proposal was also verified by the C-2 hydrogen activated through forming an H-bond with the O of [4-I-Phen]
signal of the [Bmim] cation moving from δ 9.30 to 9.16 ppm, (see Fig. S10a), which made the nucleophilicity of the oxygen
when the molar ratio of MC-1 to [Bmim][4-I-Phen] increased of endo-OH increased.37 Undoubtedly, there is a similar result
from 0:1 to 5:1 (see Fig. S9a). Meanwhile, the proton of [4-I- for MC-2 (see Fig. S10 and S11b).
Phen] anion shifted from δ 7.03 and 6.17 ppm to 7.13 and 6.30
ppm (see Fig. S9b). Upon addition of [Bmim][4-I-Phen], the
hydrogen signal of the endo-OH in MC-1 at δ 2.48 ppm could
Furthermore, the key intermediates of the early
polymerization stage were successfully captured employing
ESI-MS and MALDI-TOF-MS (Fig. 6 and Table S3-S4). As
Scheme 1 Plausible melt polymerization mechanism of polycondensation stage.
Fig. 6 (a) ESI-MS spectrum of PIC oligomers obtained at 160 oC; and (b) MALDI-TOF-MS spectrum of PIC oligomers obtained at 180 oC.
This journal is © The Royal Society of Chemistry 20xx
Green Chem., 2013, 00, 1-10 | 7
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 8 of 11
ARTICLE
Green Chemistry
presented in Fig. 6a, the intervals of Δm/z =172 Da is the PIC The [4-I-Phen] anion of [P4444][4-I-Phen] still cVoieuwldArtifcolerOmnlinae
repeating unit mass and the oligomers mainly feature Na+ strong H-bond (bond length: 1.58 Å) with the hydrogen of
DOI: 10.1039/D0GC00493F
adducts. The end groups of -OH, -OCOOCH3 and -OCH3 could endo-OH in MC-1 (Fig. 7b). However, at the polymerization
1
be detected, which are perfectly consistent with the above H stage, the terminal -OCOOCH3 proportion of the prepolymers
NMR results. We also analyzed the end group types of PIC is more than the terminal -OH, resulting in a greater
oligomers using the analysis technique of MALDI-TOF-MS (Fig. probability of the terminal -OCOOCH3 reacting with each other
6b and Table S4). The oligomers mainly feature the adducts of than that with -OH. At this point, the cation of IL plays a vital
isosorbide molecule, H2O molecule, and H+, which may be due role in activating the terminal -OCOOCH3 for the polymer chain
to the residual isosorbide with strong moisture absorbability. growth, and the [Bmim] cation shows a better catalytic effect
The types of end groups are in full accord with the above for the polymerization stage obviously, which is in accord with
results.
the abovementioned result of catalyst activity evaluation. To
clarify the inferior catalytic activity of protic ILs, the interaction
of DMC with [TMGH] cation or [P4444] cation has also been
investigated (Fig. 7c-d). As expected, the hydrogen atom in -
NH2 of [TMGH] cation could form a strong H-bond (bond
length: 1.80 Å). There are only weak van der Waals forces
between [P4444] cation and the DMC molecule. In other words,
the interactions between IL’s anion or cation and substrates
should keep a balance for its anion-cation synergistic catalysis.
Therefore, the cation of phenolic ILs and substrate with a
moderate H-bond strength is beneficial to synthesis PIC with a
higher molecular weight.
Briefly, the mechanism of the polymerization stage (Scheme
1) could be described as follows: for cycle-I, initially, the
oxygen of C=O in DC (MC-1 or MC-2) forms an H-bond with the
C-2 hydrogen of [Bmim] cation, which makes the carbon of
C=O in DC (MC-1 or MC-2) more easily to be attacked by the
nucleophile. The hydrogen of -OH in MC-1 or MC-2 forms an H-
bond with the oxygen of [4-I-Phen] anion, which makes the
oxygen of -OH in MC-1 (MC-2) exhibit stronger nucleophilicity.
As a consequence, the carbon of C=O in DC (MC-1 or MC-2) is
attacked by the oxygen of -OH in MC-1 or MC-2 more easily
(Step 1). With the electron transfer, an unstable complex is
formed (Step 2). Subsequently, with the electron further
transfer and the electrostatic interactions, the highly volatile
methanol generates at high temperature and high vacuum
more easily. Spontaneously, the oligomer produces and
[Bmim][4-I-Phen] regenerates (Step 3). For cycle-II, first, the
carbon of C=O in DC (MC-1 or MC-2) is activated through the
formation of an H-bond between the oxygen of C=O in DC
(MC-1 or MC-2) and the C-2 hydrogen of [Bmim] cation. In the
another molecule of DC (MC-1 or MC-2), the carbon of C=O is
activated by the nucleophile of [4-I-Phen] anion, which makes
the oxygen of -OCOOCH3 beside the furan ring could attack the
pre-activated carbon of C=O in DC (MC-1 or MC-2) molecule
more readily (Step 1’). With the electron transfer, an unstable
complex is formed and the COOCH3 positive ion is dissociated
out (Step 2’). Afterward, with the electron further transfer and
the electrostatic interactions, the highly volatile DMC
generates more easily at high temperature and high vacuum.53
Spontaneously, the oligomer produces and [Bmim][4-I-Phen]
regenerates (Step 3’). Then, the terminal -OH and -OCOOCH3
of oligomers repeat the above similar catalytic cycles (cycle-I
and cycle-II), resulting in the increasing of PIC molecular
weight. It should be mentioned that the terminal -OCOOCH3 of
polymer chain transforming into -OCH3 can lead to this end of
polymer chain stopping chain growth.
Fig. 7 Optimized structure of (a) [Bmim][4-I-Phen] interaction
with DC and MC-1; (b) [P4444][4-I-Phen] interaction with DC and
MC-1; (c) [TMGH] cation interaction with DMC; (d) [P4444
]
cation interaction with DMC. C atom (dark grey), H atom (light
grey), O atom (red), N atom (blue), I atom (purple), P atom
(yellow).
To further confirm the proposed polymerization mechanism,
DFT calculations were implemented for investigating the
interactions between IL and the transesterification products.
The amount of DC is close to the total amount of MC-1 and
MC-2 under the optimal conditions catalyzed by [Bmim][4-I-
Phen]. Therefore, the interactions among [Bmim][4-I-Phen],
DC and MC-1 were selected to geometry optimizations and
energy calculations at the B3LYP/6-311+G* level using the
Gaussian 09 program (see ESI†). As expected, the C-2
hydrogen of [Bmim] cation could form a weak H-bond (bond
length: 2.10 Å) with the oxygen of C=O in DC and the [4-I-Phen]
anion could form a strong H-bond (bond length: 1.60 Å) with
the hydrogen of endo-OH in MC-1 (Fig. 7a) at the same time.
By analogy, the polymer chain with the terminal -OH or
terminal OCOOCH3 also could form H-bonds with [Bmim][4-I-
Phen]. As a result, the dual H-bonds are high-efficient to
promote the polymerization progress. For comparison, the
interactions among [P4444][4-I-Phen], DC and MC-1 were also
surveyed. There are only weak van der Waals forces between
[P4444] cation and the DC molecule, due to the long alkyl chain
of [P4444] cation resulting in the increase of steric hindrance.
8 | Green Chem., 2013, 00, 1-10
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 11
Green Chemistry
Please do not adjust margins
Green Chemistry
ARTICLE
(MALDI-TOF MS) (Bruker, Germany) fitted with alVpiehwaA-crtyicalenOon-li4ne-
hydroxycinnamic acid (α-CCA) as the MALDI matrix. TG-MS
Conclusions
DOI: 10.1039/D0GC00493F
In summary, a strategy for PIC synthesis with adjustable
molecular weight from the biorenewable isosorbide and the
CO2-derived DMC catalyzed by phenolic ILs has been
developed. Noteworthily, the excellent tunability of phenolic
IL’s structure facilitated the H-bond strength of the cation and
anion of IL with substrates to vary readily, causing different
catalytic activity of IL catalysts. Concerning PIC synthesis, the
catalytic activity of aprotic IL catalysts was superior to protic IL
data were collected on a Setaram Labsys Evo TGA 1600
thermal gravimetric analyzer and a mass spectrometer (MS,
Tilon grp technology limited). The selectivities of
carboxymethyl compounds were measured on a SHIMADZU
LC-20AT HPLC with a differential refraction detector (RID) and
an InertSustain C18 chromatographic column.37 The molecular
weights of PICs were identified using an Agilent PL-GPC 50 gel
permeation chromatography (GPC). Polystyrene and the
moving phase of dimethylformamide (DMF) were used to
establish the calibration curve. Thermogravimetric Analysis
1
catalysts. Based on the H NMR analysis and DFT calculations,
we discovered the cation of phenolic ILs and substrate with a
moderate H-bond strength was beneficial to synthesis PIC with (TGA) was performed on a Diamond TG/DTA6300 thermal
analyzer with a heating rate of 10 oC/min under an N2
atmosphere. The glass transition temperature was measured
on a Mettler Toledo DSC 1 differential scanning calorimeter
(DSC) with a heating rate of 10 oC/min and a nitrogen flow rate
of 50 mL/min.
a higher molecular weight. Additionally, an IL’s anion-cation
synergistic catalytic mechanism has been proposed, which
reveals that nucleophile electrophile dual activation by H-
bonds and charge-charge interactions in catalyzing PIC
formation. Further significance of this study is that we provide
a guidance of developing other IL catalysts for preparing higher
molecular weight polycarbonates with the biorenewable
building blocks, thus expediently creating various polymeric
materials with desired properties.
Conflicts of interest
There are no conflicts to declare.
Acknowledgments
Experimental
This work is financially supported by National Key R&D
Program of China (2016YFB0600903); National Natural Science
Foundation of China (No. 21890763, No. 21908226);
Innovation Academy for Green Manufacture, Chinese
Academy of Sciences (No. IAGM-2019-A01).
Synthesis of ILs
IL catalysts were synthesized through the acid-base
neutralization reaction according to the previous literature.54-
56
For instance, synthesis of [DBUH][4-I-Phen], an ethanol
solution of 4-I-Phen was dropwise added into an equimolar
amount of DBU in an ice−water bath. Then the mixture was
stirred for 48 h at room temperature. Subsequently, the
solvent was removed by reduced pressure distillation and then
the IL was vacuum-dried for 24 h at 55 oC.
References
1
J. D. Mota-Morales, R. J. Sánchez-Leija, A. Carranza, J. A.
Pojman, F. del Monte and G. Luna-Bárcenas, Prog. Polym. Sci.,
2018, 78, 139-153.
Synthesis of PIC
PIC was prepared via the one-pot melt polymerization based
on the previous study.19 Isosorbide (10 g, 0.0684 mol), DMC
(46.23 g, 0.5132 mol), and the catalyst (4.4 × 10-3 equiv. mol,
based on IS) were mixed for the reaction. The
transesterification reaction time was set as 3.5 h. At the
polycondensation stage, the temperature was gradually
heated to 180 oC and kept 1 h. Then, the reaction temperature
2.
3
Y. Zhu, C. Romain and C. K. Williams, Nature, 2016, 540, 354.
J. Feng, R. X. Zhuo and X. Z. Zhang, Prog. Polym. Sci., 2012, 37,
211-236.
D. J. Brunelle, in Advances in Polycarbonates, American
Chemical Society, 2005, vol. 898, ch. 1, pp. 1-5.
J. T. Gu and C. S. Wang, J. Appl. Polym. Sci., 1992, 44, 849-
857.
W. B. Kim, U. A. Joshi and J. S. Lee, Ind. Eng. Chem. Res., 2004,
43, 1897-1914.
H. R. Kricheldorf, S. Böhme and G. Schwarz, Macromol. Chem.
Phys., 2005, 206, 432-438.
P. Alonso-Magdalena, E. Vieira, S. Soriano, L. Menes, D. Burks,
I. Quesada and A. Nadal, Environ. Health Perspect., 2010, 118,
1243-1250.
N. Ben-Jonathan, in Estrogen Receptor and Breast Cancer:
Celebrating the 60th Anniversary of the Discovery of ER, ed. X.
Zhang, Springer International Publishing, Cham, 2019, DOI:
10.1007/978-3-319-99350-8_13, pp. 343-377.
4
5
6
7
8
o
and vacuum degree were increased gradually to 230 C and
less than 20 Pa, respectively. Meanwhile, the mixture was
stirred continuously for 4 h at this temperature. Finally, the
obtained powder was vacuum-dried at 55 oC for 24 h.
Characterization methods
9
1H NMR and 13C NMR spectra were collected in deuterated
chloroform (CDCl3) or dimethylsulfoxide (DMSO-d6) using a
Bruker AVANCE III HD 600 MHz NMR spectrometer with
tetramethylsilane (TMS) as the internal reference. Mass 10 M. Rose and R. Palkovits, ChemSusChem, 2012, 5, 167-176.
11
F. Fenouillot, A. Rousseau, G. Colomines, R. Saint-Loup and J.
P. Pascault, Prog. Polym. Sci., 2010, 35, 578-622.
spectra data were recorded on a Bruker micrQTOF-Q II mass
spectrometer or an Autoflex III Matrix-assisted laser
desorption/ionization time-of-flight mass spectrometry
This journal is © The Royal Society of Chemistry 20xx
Green Chem., 2013, 00, 1-10 | 9
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 10 of 11
ARTICLE
Green Chemistry
12. W. Lai, L. Su, M. Zhang, J. Yan and G. Wu, J. Polym. Sci., Part 42
A: Polym. Chem., 2019, 57, 1670-1681.
P. Metrangolo, H. Neukirch, T. Pilati and G.ViRewesAnrtaictlie,OAnlcince.
Chem. Res., 2005, 38, 386-395.
DOI: 10.1039/D0GC00493F
13
D. J. Saxon, M. Nasiri, M. Mandal, S. Maduskar, P. J. 43
Dauenhauer, C. J. Cramer, A. M. LaPointe and T. M. Reineke,
P. Metrangolo, F. Meyer, T. Pilati, G. Resnati and G. Terraneo,
Angew. Chem., 2008, 120, 6206-6220.
JACS, 2019, 141, 5107-5111.
C. Ma, F. Xu, W. Cheng, X. Tan, Q. Su and S. Zhang, ACS
Sustainable Chem. Eng., 2018, 6, 2684-2693.
44
45
H. Y. Ju, M. D. Manju, K. H. Kim, S. W. Park and D. W. Park, J.
Ind. Eng. Chem., 2008, 14, 157-160.
T. L. Greaves and C. J. Drummond, Chem. Rev., 2008, 108,
206-237.
14
15
S. Fukuoka, I. Fukawa, M. Tojo, K. Oonishi, H. Hachiya, M.
Aminaka, K. Hasegawa and K. Komiya, Catal. Surv. Asia, 2010, 46
14, 146-163.
K. Dong, S. Zhang and J. Wang, Chem. Commun., 2016, 52,
6744-6764.
16
17
18
19
W. Sun, F. Xu, W. Cheng, J. Sun, G. Ning and S. Zhang, Chinese 47
J Catal.,, 2017, 38, 908-917.
Y. S. Eo, H.-W. Rhee and S. Shin, J Ind Eng Chem., 2016, 37, 48
P. Tundo, F. Aricò, A. E. Rosamilia and S. Memoli, Green
Chem., 2008, 10, 1182-1189.
M. Zhang, W. Lai, L. Su and G. Wu, Ind. Eng. Chem. Res., 2018,
57, 4824-4831.
42-46.
Z. Zhang, F. Xu, H. He, W. Ding, W. Fang, W. Sun, Z. Li and S. 49
Zhang, Green Chem., 2019, 21, 3891-3901.
Q. Li, W. Zhu, C. Li, G. Guan, D. Zhang, Y. Xiao and L. Zheng, J. 50
P. Tundo and F. Aricò, ScienceOpen Research, 2014, DOI:
10.14293/S2199-1006.1.SOR-CHEM.AB3R7E.v2.
A. K. Chakraborti and S. R. Roy, JACS, 2009, 131, 6902-6903.
J. Sun, T. Dutta, R. Parthasarathi, K. H. Kim, N. Tolic, R. K. Chu,
N. G. Isern, J. R. Cort, B. A. Simmons and S. Singh, Green
Chem., 2016, 18, 6012-6020.
I. Skarmoutsos, D. Dellis, R. P. Matthews, T. Welton and P. A.
Hunt, J. Phys. Chem. B, 2012, 116, 4921-4933.
A. G. Shaikh, S. Sivaram, C. Puglisi, F. Samperi and G.
Montaudo, Polym. Bull., 1994, 32, 427-432.
C. Wang, H. Luo, D. E. Jiang, H. Li, S. Dai, Angew. Chem., Int.
Ed., 2010, 49, 5978-5981.
Polym. Sci. Part A: Polym. Chem., 2013, 51, 1387-1397.
P. Tundo and M. Selva, Acc. Chem. Res., 2002, 35, 706-716.
S. H. Pyo, J. H. Park, T. S. Chang and R. Hatti-Kaul, Current
Opinion in Green and Sustainable Chemistry, 2017, 5, 61-66.
P. Tundo, F. Aricò, G. Gauthier, L. Rossi, A. E. Rosamilia, H. S.
51
20
21
52
22
Bevinakatti, R. L. Sievert and C. P. Newman, ChemSusChem, 53
2010, 3, 566-570.
W. J. Yoon, S. Y. Hwang, J. M. Koo, Y. J. Lee, S. U. Lee and S. S. 54
Im, Macromolecules, 2013, 46, 7219-7231.
L. Feng, W. Zhu, W. Zhou, C. Li, D. Zhang, Y. Xiao and L. Zheng, 55
23
24
K. Fukumoto, M. Yoshizawa, H. Ohno, JACS, 2005, 127, 2398-
2399.
Polym. Chem., 2015, 6, 7470-7479.
25
26
P. R. Schreiner, ChemInform, 2003, 34.
L. Hao, Y. Zhao, B. Yu, Z. Yang, H. Zhang, B. Han, X. Gao and Z.
Liu, ACS Catal., 2015, 5, 4989-4993.
56
B. Yu, H. Zhang, Y. Zhao, S. Chen, J. Xu, L. Hao, Z. Liu, ACS
Catal., 2013, 3, 2076-2082.
27
28
29
30
31
32
33
34
S. Zhang, J. Sun, X. Zhang, J. Xin, Q. Miao and J. Wang, Chem.
Soc. Rev., 2014, 43, 7838-7869.
W. Wang, C. Li, L. Yan, Y. Wang, M. Jiang and Y. Ding, ACS
Catal., 2016, 6, 6091-6100.
Y. Qiao, W. Ma, N. Theyssen, C. Chen and Z. Hou, Chem. Rev.,
2017, 117, 6881-6928.
Y. Wu, Y. Zhao, R. Li, B. Yu, Y. Chen, X. Liu, C. Wu, X. Luo and
Z. Liu, ACS Catal., 2017, 7, 6251-6255.
S. R. Roy and A. K. Chakraborti, Org. Lett., 2010, 12, 3866-
3869.
W. Chen, Y. Zhang, L. Zhu, J. Lan, R. Xie and J. You, J. Am.
Chem. Soc., 2007, 129, 13879-13886.
K. Chen, G. Shi, W. Zhang, H. Li and C. Wang, JACS, 2016, 138,
14198-14201.
M. Bystrzanowska, F. Pena-Pereira, Ł. Marcinkowski and M.
Tobiszewski, Ecotoxicology and Environmental Safety, 2019,
174, 455-458.
35
36
37
38
39
40
41
L. Zhang, X. Fu and G. Gao, ChemCatChem, 2011, 3, 1359-
1364.
M. Liu, L. Liang, X. Li, X. Gao and J. Sun, Green Chem., 2016,
18, 2851-2863.
W. Qian, X. Tan, Q. Su, W. Cheng, F. Xu, L. Dong and S. Zhang,
ChemSusChem, 2019, 12, 1169-1178.
N. L. Lancaster, P. A. Salter, T. Welton and G. B. Young, J Org
Chem., 2002, 67, 8855-8861.
A. Cerda-Monje, A. Aizman, R. A. Tapia, C. Chiappe and R.
Contreras, Phys Chem Chem Phys., 2012, 14, 10041-10049.
N. L. Lancaster and T. Welton, J Org Chem., 2004, 69, 5986-
5992.
G. Cui, J. Zheng, X. Luo, W. Lin, F. Ding, H. Li and C. Wang,
Angew. Chem., Int. Ed., 2013, 52, 10620-10624.
10 | Green Chem., 2013, 00, 1-10
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 11 of 11
Green Chemistry
View Article Online
DOI: 10.1039/D0GC00493F
Phenolic ionic liquid’s structure is capable of being designed readily to control the molecular
weight of isosorbide-derived polycarbonate.