An Investigation on the Production of Random Copolymer with Monothiocarbonate and Trithiocarbonate Units over Cyclic Thiocarbonate via Metal-free Catalysis

Article abstract of DOI:10.1002/cjoc.201900522

Synthesis of poly(thiocarbonate)s from the copolymerization of epoxides and carbon disulfide (CS₂) remains a tough challenge, due to inevitable oxygen-sulfur atom scrambling process. In this work, we utilized the oxygen-sulfur exchange reaction

Full text of DOI:10.1002/cjoc.201900522

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: An Investigation on the Production of Random Copolymer with
Monothiocarbonate and Trithiocarbonate Units over Cyclic Thiocarbonate via
Metal-free Catalysis
Authors: Jia-Liang Yang, Lan-Fang Hu, Xiao-Han Cao, Ying Wang, and Xing-Hong
Zhang*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.201900522.
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An Investigation on the Production of Random Copolymer with
Monothiocarbonate and Trithiocarbonate Units over Cyclic
Thiocarbonate via Metal-free Catalysis
Jia-Liang Yang,a Lan-Fang Hu,a Xiao-Han Cao, a Ying Wang, a and Xing-Hong Zhang *,a
a MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou
310027, China
Summary of main observation and conclusion Synthesis of poly(thiocarbonate)s from the copolymerization of epoxides and carbon disulfide (CS2)
remains a tough challenge, due to inevitable oxygen-sulfur atom scrambling process. In this work, we utilized the oxygen-sulfur exchange reaction (O-S
ER) to synthesize a random copolymer with monothiocarbonate and trithiocarbonate units from CS2 and phenyl glycidyl ether (PGE) via metal-free Lewis
pairs. The copolymers contained monothiocarbonate and trithiocarbonate units of which the molar fraction could be tuned by varying either the types of
Lewis pairs or the reaction temperature. Keeping track on the intermediate provided an insight in the process of O-S ER and thus gave a hint to control the
product structure. Production and consumption of phenyl thioglycidyl ether was the key process to regulate the chain structure. Remarkably, the oxygen
atoms of PGE could be excluded out of the chain, resulting in the nearly complete production of poly(trithiocarbonate)s. Correspondingly, the refractive
index of this kind of copolymer could be regulated in a wide range of 1.73-1.79 (at 590 nm).
polymer linkages and two cyclic products were revealed by 1H and
Background and Originality Content
13C NMR spectroscopy, and
a plausible mechanism on a
(Main Text Paragraphs. Note: Poly(thiocarbonate)s with
tunable structure and high refractive index (RI) were successfully
synthesized from CS2 and phenyl glycidyl ether. This work
provided a new method to harness O-S ER in the copolymerization
of CS2 with epoxides that are low-cost commercially available
chemicals)
tetrahedral intermediate was presented based on the result of in
situ infrared spectroscopic monitoring of the polymerization
process. After that, Werner and his coworkers used metal alkoxide
as catalyst to mediate the reaction of CS2 with different
epoxides20-21, similar mechanism was proposed for O-S ER process.
In particular, catalyst loading was found to have decisive effect in
the product constitute for this catalyst system. Lower
concentration of metal alkoxide (0.125-0.5%) leaded to highly
regioregular and alternating polythiocarbonates composed of five
different linkages, while at higher loadings the reaction pathway
switched in favor to the formation of cyclic dithiocarbonates. Of
all these works, the formation of copolymers was always
accompanied by the O-S ER process, therefore, the
copolymerization always results in complicated chain structures.
Copolymerization of carbon dioxide has got
a rapid
development in the past decades1-5, while the coupling of its
sulfur containing analogue CS2 hasn’t been treated equally. The
utilization of CS2 as a C1 monomer could potentially relieve the
pressure of petroleum resources crisis and introduce sulfur atoms
into the polymers by a “green” route simultaneously6. In 2007,
Nozaki and co-workers conducted the copolymerization of
propylene sulfide and CS2 to yield poly(propylene trithiocarbonate)
with high refractive index (RI) of 1.781. During 2008-2009, various
structures produced by Oxygen-Sulfur Exchange Reaction (O-S ER)
in both the polymer and cyclic byproducts were confirmed by
Zhang8 and Darensbourg9 respectively. This process can generate
CO2, carbonyl sulfide (COS) and episulfide that mixing in the
reaction system and mutually copolymerize with CS2 and epoxide,
resulting in the copolymers with randomly distributed
thiocarbonates [-SC(=O)O-, -OC(=S)O-, -SC(=S)S-], carbonate
[-OC(=O)O-] or even (thio)ether units. As an important scrambling
intermediate, carbonyl sulfide (COS), was firstly identified by
GC-MS in Zhang’s work when investigating the copolymerization
of CS2 with propylene oxide (PO). Since then, utilization of COS as
a C1 monomer in copolymerization has got widely concerned and
made rapid progress in a short time10-18, while investigations on
CS2 copolymerization is standstill. The greatest challenge for
studying CS2 copolymerization lies in the O-S ER process which will
interrupt the coupling reaction, as a result, complicated linkages
will be generated in the polymer chain.
Scheme 1 O-S ER products of CS2 with cyclic ethers from different catalysts,
Cat. 1: Zinc-Cobalt(III) double-metal cyanide complexes (DMCC), Cat. 2:
(salen)CrCl/oniumsalts), Cat. 3: Lithium t-butoxide.
To figure out the mechanism of O-S ER, we have investigated
the pathways for O-S ER process by using oxetane, a symmetric
monomer, to copolymerize with CS2 in the catalyzing of
(salen)CrCl/(onium salts) binary system19. As a result, five different
Since O-S ER was inevitable in the copolymerization of CS2
with cyclic ethers, so we wondered the possibility of harnessing it.
*E-mail: xhzhang@zju.edu.cn
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First author et al.
Report
Varying the tendency of O-S ER22 might be used as an effective
method to tune the sulfur content in the polymer chain.
Meanwhile introduction of sulfur atom in the polymer chain is
benefit for increasing refractive index (RI) of the resulted
copolymer21-23. The thusly formed high RI polymer is an important
class of materials that has been widely developed in recent years
for optical components due to their lightweight, high impact
copolymerization catalyzed by metal catalyst17. Since COS is a
confirmed intermediate of O-S ER, so we considered that, using
LPs as catalysts for the copolymerization of CS2 and PGE could
result in much simpler mainchain structure for the bluntness of
PGE to COS27. Except for this, introduction of aromatic rings is also
benefit for increasing RI of a polymer material. We supposed that,
organic Lewis pairs could be utilized to catalyze the
copolymerization of CS2 and PGE, providing poly(thiocarbonate)s
with precise chain structure, tunable sulfur content, high RI and
free of metal residue.
resistance, low cost and easy processing26-29
. Remarkably,
polymerization with elemental sulfur (S8) is the universal way to
provide sulfur-rich polymers with high RI, and these polymers
performed well in Li-S batteries, metal ion detection, IR imaging
technology and self-healing materials30. Here we propose that O-S
ER could be utilized as an atom redistribution process, by which
we could synthesize poly(thiocarbonate)s from CS2 with precise
structure and easily tunable sulfur content, thus to produce sulfur
containing polymers with high RI.
Scheme 2 Copolymerization of CS2 with PGE catalyzed by organic Lewis
pairs.
PhO
S
O
Cat.
+ S
OPh
C
S
S
S
Catalyst design is usually the core of meditating
a
O
O
m
n
polymerization process31-33. Confined by the difficulty in intricate
design and multiple synthesis steps of metal catalyst, modifying of
the polymer by varying catalyst structure faces great troubles.
Worse still, metal residue of the catalyst imposed much
restrictions on the application of the resulted polymer materials13.
Recently, development in organic Lewis pairs (LP)s catalysts
provided an alternative route33-35. Organic LPs were proved to be
effective in catalyzing the copolymerization of CO2/COS with
different epoxides13,36, providing various polycarbonates and
poly(monothiocarbonate)s without metal residues. It is
convenient to tune the synergy between Lewis acid (LA) and Lewis
base (LB) for particular polymerization situation since their simple
structures and easily accessible characters. Another notable factor
is that phenyl glycidyl ether (PGE) showed lower activity when
copolymerize with COS by LPs13, comparing with the same
S
PhO
L2
L1
Cat.=Lewis Pair
Two Linkages only!
B
Lewis Acid:
Lewis Base:
Cl
N
Br
P
N
N
10
Activity:
N
>
>
Ph
Ph
Ph
Ph
Br
Cl
P
P
P
Ph
Ph
N
Results and Discussion
Copolymerization of Carbon Disulfide and Phenyl Glycidyl Ether (PGE)
Table 1 Copolymerization of CS2 with PGE catalyzed by different Lewis pairs composed of TEB and Lewis bases a
Entry
LB
TOF
(h-1)b
63
Copolymer
Mn
(kg/mol)d
7.4
Đ
L1:L2
(%)c
C1:C2:C3
(%)c
Selectivity (%)c
(Mw/Mn)d
1
2
3
4
5
6
7
8
TEA
DBU
35
40
41
40
41
35
0
1.5
1.4
1.5
1.7
1.6
1.4
-
68:32
69:31
76:24
75:25
83:17
82:18
-
88:8:4
83:17:0
88:12:0
86:10:4
93:0:7
95:0:5
96:4:0
-
63
5.8
PPNCl
PPh4Cl
PPh4Br
DTMeAB
TBD
63
11.1
12.6
9.7
63
46
30
11.6
-
60
DMAP
0
-
-
-
-
a (The reactions were performed in bulk ([TEB]:[LB]: [PGE]: [CS2] = 1:1:500:750, molar ratio) in a 10 ml autoclave at 40 oC for 8 h. TEB: Triethyl borane, TEA:
Triethyl amine, DBU: 1,8-Diazabicyclo[5.4.0]undec-7-ene, [PPN]Cl: Bis(triphenylphosphine)iminium chloride, PPh4Cl: Tetraphenyl phosphonium chloride,
PPh4Br: Tetraphenyl phosphonium bromide, DTMeAB: Dodecyltrimethylammonium bromide, TBD: 1,5,7-Triazabicyclododecene, DMAP:
4-dimethylaminopyridine.) b ((Mol epoxide consumed)/(mol TEB h), determined by using 1H NMR spectroscopy of crude product.) c (Determined by using
1H NMR spectroscopy of crude product. Polymer selectivity is the molar ratio of the copolymer to all the cyclic product.) d (Determined by using gel
permeation chromatography (GPC) in THF, calibrated with polystyrene standards.)
2
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As summarized in Table 1, copolymerization of CS2 and PGE
was successfully catalyzed by organic Lewis pairs composed of TEB
as LA and various LBs at 40 oC. In most cases, conversion of PGE
accomplished in 8 h resulting in TOF values around 63 h-1. Rather
than a couple of complicated linkages as previously reported in
metal catalyst systems8-9,21-22 (Scheme 1), all of the resulted
copolymers had only two kinds of alternating linkages,
monothiocarbonate [-O(C=S)O-] (L1) and trithiocarbonate linkages
Nature of the Lewis base has a strong impact on the activity,
selectivity and molecule weight. When the feeding ratio of [TEB]:
[LB]: [PGE]: [CS2] was 1: 1: 500: 750 (molar ratio), other than
DMAP, most of the LBs could catalyze the copolymerization of CS2
and PGE resulted in a copolymer chain composed of L1 and L2 at
40oC (entries 1-6, Table 1). Based on activity, these LBs could be
divided into three groups. TEA and DBU showed relatively high
activity when coupled with TEB at 40 oC, TOF value of 63 h-1 was
observed, and L2 content were over 30 % (entry 1, 32 %, entry 2,
31 %, Table1). Chlorine anion of PPNCl and PPh4Cl led to a lower
L2 content of 24-25 % (entries 3-4, Table1), with similar TOF
values. While PPh4Br and DTMeAB with bromine anion showed
relatively low activity, not all the monomers accomplished
conversion in 8 h, and the TOF were 46 h-1 and 30 h-1 respectively.
Meanwhile, the corresponding polymer chains had low L2 content
(entry 5, 17%, entry 6, 18 %, Table 1). Variation in the content of
product is revealed in Figure 2. The special case was when TBD
served as LB, no polymer was produced and the selectivity of C1
was very high (96 %, entry 7, Table1). However, changes in
molecule weight of the resulted copolymer was irregular, because
the molecule weight was determined by a series factors including
initiator efficiency, conversion and copolymer selectivity13. With
similar TOF value and copolymer selectivity, molecule weights of
poly(thiocarbonate)s obtained from chlorine anion (11.4,
12.6kg/mol, entries 3, 4, Table 1) were larger than that of TEA and
DBU (7.4 and 5.8 kg/mol entries 1, 2, Table 1), which means the
initiator efficiency of quaternary ammonium salts was lower than
that of organic LB. And the initiator efficiency of bromine anion
was even lower (entries 5, 6, Table 1), for the size of bromine is
larger which hindered its combination with TEB in the chain
initiation stage13.
[-S(C=S)S-] (L2), confirmed by H NMR and H-13C HSQC spectra
(Figure 1, Figures S1-S7). As expected, COS was still an
intermediate in this copolymerization, confirmed by GC-MS
(Figure S8). Bluntness of PGE to COS in forming copolymer might
be the major reason for the absence of other linkages, and the
resulted copolymers with only two kinds of linkages is very
convenient for further structure optimizing. Molecule weights of
the produced copolymers ranged from 5.8-12.6 kg/mol with cyclic
thiocarbonates produced in a proportion of around 60 %. There
was no dithiocarbonate linkages [-S(C=S)O-] in the backbone,
indicating that the copolymer was totally formed by O-S ER
process. The ratio of L1/L2 linkages was decided by the tendency
of O-S ER and finally reflected sulfur content in the copolymer.
Since L2 is “sulfur-rich” compared with L1, high concentration of
L2 in the backbone is in favor of increasing sulfur content and high
RI of the copolymer.
1
1
Figure 1 (a) 1H NMR spectrum of purified product (entry 6, Table1); (b)
1H-13C HSQC spectrum of purified product showing 1J correlation peaks of
hydrogen atom and carbon atom in the same methyne and methylene
(entry 6, Table1).
a Department, Institution, Address 1
E-mail:
c Department, Institution, Address 3
E-mail:
b Department, Institution, Address 2
E-mail:
Chin. J. Chem. 2018, template
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First author et al.
Report
copolymer and constituent of cyclic product indicated the
distribution of oxygen and sulfur element between linear and
cyclic products. If the cyclic product is sulfur-rich, then the
copolymer should be oxygen-rich, vice-versa. And this distribution
was totally determined by the tendency of O-S ER. What is
important is that, other than two common five member cyclic
products 5-(phenoxymethyl)-1,3-oxathiolane-2-thione (C1) and
4-(phenoxymethyl)-1,3-dithiolane-2-thione
(C2)20,
phenyl
thioglycidyl ether (C3) was observed in the 1H NMR spectra of
crude product (Figures S3, S5, S6). Usually thiiranes are taken as
the byproduct in the coupling of CS2 with epoxides37, while we
think it may serve as an intermediate of O-S ER just like COS, and
its participation in the copolymerization process resulted in
inequality of L1 and L221. As
a whole, the tendency of
oxygen/sulfur ratio in cyclic product was ought to be in
accordance with the constitution change in copolymers. However,
when oxygen-rich content L1 increased from 68 % to 82 % in the
backbone (entries 1 and 6, Table 1), decrease of dithiocarbonate
in cyclic product was unobvious (Figure 2). Reasonable
speculation is that, oxygen-rich intermediate COS and CO2 were
produced and excluded from the polymerization process13. Rather
than L3, linkages of L1 and L2 were produced by the interaction of
CS2 and PGE through a tetrahedral intermediate19,21, on the other
hand, direct copolymerization of CS2 with C3 would also resulted
to the formation of L2.
Figure 2 Effect of Lewis base on the result of CS2/PGE copolymerization,
corresponding content of linkages in the polymer chain (red color) and
composition of cyclic products (blue color) are marked respectively. (1)
entry 1 in Table 1, TEA served as LB, (2) entry 2 in Table 1, DBU served as
LB, (3) entry 3 in Table 1, PPNCl served as LB, (4) entry 4 in Table 1, PPh4Cl
served as LB, (5) entry 5 in Table 1, PPh4Br served as LB, (6) entry 6 in Table
1, DTMeAB served as LB.
Other than linear copolymer, cyclic product was another
pivotal factor that worth noticing. Ratio of cyclic product to the
Tuning the O-S ER process by the influencing factors
a
Table 2 Copolymerization of CS2 with PGE at different temperature by three kinds of LPs.
Entry
Temp
[°C]
25
LB
TOF
[h-1]b
45
53
63
63
13
54
63
63
9
Copolymer
Mn
[kg/mold
7.5
Đ
[Mw/Mn]d
1.7
L1: L2
C1: C2: C3
c
c
selectivity (%) c
%
%
1
2
TEA
TEA
34
30
27
14
35
42
26
18
30
34
34
27
82:18
75:25
38:62
0:100
91:9
94:0:6
89:4:7
30
7.8
1.5
3
60
TEA
6.2
1.5
85:15:0
82:18:0
100:0:0
89:5:6
4
80
TEA
2.9
1.3
5
25
PPh4Cl
PPh4Cl
PPh4Cl
PPh4Cl
DTMeAB
DTMeAB
DTMeAB
DTMeAB
3.1
1.5
6
30
10.5
7.4
1.5
85:15
38:62
0:100
84:16
83:17
54:46
38:62
7
60
1.6
80:20:0
78:22:0
100:0:0
100:0:0
83:7:10
81:19:0
8
80
5.7
1.7
9
25
2.3
1.4
10
11
12
30
11
58
63
2.6
1.4
60
12.4
4.6
1.5
80
1.7
a (The reactions were performed in bulk ([TEB]:[LB]: [PGE]: [CS2] = 1:1:500:750, molar ratio) in a 10 ml autoclave for 8 h.) b ((Mol epoxide consumed)/(mol
TEB h), determined by using 1H NMR spectroscopy of crude product.) c (Determined by using 1H NMR spectroscopy of crude product. Polymer selectivity is
the molar ratio of the copolymer to all the cyclic product.) d (Determined by using gel permeation chromatography (GPC) in THF, calibrated with
polystyrene standards.)
We further investigated the influential factors of O-S ER and
their effect on the distribution of sulfur atoms between
poly(thiocarbonate)s and cyclic product. TEA, PPh4Cl and DTMeAB
differed from each other in activity, were chose to couple with
TEB to catalyze the copolymerization of CS2 and PGE at different
temperatures, the results were summarized in Table 2 (Figures
S10-21). Caused by the rising of temperature, increasing in activity
and sacrifice of copolymer selectivity were observed in all the
three LPs, which is conform to the previous reported results of LP
catalysts13. For all the LPs, sulfur atoms preferred to concentrate
in linear polymer when the reaction temperature increased
(entries 1-12, Table 2). For TEA and PPh4Cl, copolymers composed
of fully L2 linkages were produced when the reaction temperature
was raised to 80°C. While high temperature also resulted in
inferior copolymer selectivity, thus molecule weights of the
resulted copolymers were low (2.9kg/mol, entry 4, Table 2;
5.7kg/mol, entry 8, Table 2). As for TEB/DTMeAB pair, since its low
activity, the highest L2 content was 62% in 80°C (entry 12, Table 2).
On the other hand, low reaction temperature was in favor of
forming C1. When TOF value was less than 13h-1, only C1 was
produced as cyclic product (entries 5, 9, 10, Table 2). To draw a
conclusion, temperature and the activity of LPs are two powerful
factors which could be utilized to regulate the sulfur/oxygen
distribution between the linear polymer and cyclic product.
What is important in deciding the copolymerization result is
the appearance and vanishing of C3. As the polymerization
intermediate, C3 was produced in accompany with COS from CS2
and PGE in the presence of equivalent TEB and TEA, confirmed by
1H NMR spectrum and GC-MS (Figures S8, S9). However, C3 didn’t
always appear in all of the copolymerization crude product and it
4
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Running title
Chin. J. Chem.
experienced prominent variation with the change of temperature.
When TEA was used as LB, C3 was only tracked in reaction
temperature below 40°C (entry 1, Table1, entries 1 and 2, Table2),
and disappeared when the temperature was above 60°C (entries 3
and 4, Table2). Correspondingly, with the consumption of C3,
content of L2 in the polymer chain increased from 18 to 100%
(entries 1-4, Table2). Similar trend of cyclic product constitution
was observed when using PPh4Cl and DTMeAB as Lewis base.
Appearance of C3 at relative low reaction temperature and
disappearing with rising of temperature was observed for these
two LBs (Figure 3), while the demarcation point for each LB was
different. Appearance and ceiling temperature for the existence of
C3 increased with the diminishing of LP activity (25-40°C for TEA,
30-40°C for PPh4Cl, 40-60°C for DTMeAB). We supposed that, the
activation energy for consummation of C3 is higher than that of
producing it, so this reaction intermediate only exist in a particular
temperature range, and the range goes up with the decreasing
activity of Lewis base. As a result, high temperature and LP with
stronger activity inclined to produce sulfur concentrated
polythiocarbonates (L2 linkage in this work).
should be equal with each other, however, ether L1 > L2 or L2 > L1
were observed in the above mentioned results. Loss of L2 may be
caused by another rearrangement process involving −S(C=S)S- and
epoxide monomer. This process converts a L2 linkage to L1 with
the production C3 as byproduct, which might be one of the routes
to form C3. And this rearrangement of course reduces the content
of L2 in the polymer chain. On the other hand, C3 could also serve
as
a monomer to participate in the alternating insertion
competing with PGE. Insertion of C3 will increase the content of
L2, apparently increasing temperature and enhancing the activity
of LPs were apparently benefit for this reaction. As a result, high
concentration (even fully) L2 linkages were observed at above
60°C when using TEA or PPh4Cl as Lewis base.
High Refractive Index copolymers from CS2 and PGE
1.88
(1) L1:L2=38:62 RI=1.79
(2) L1:L2=68:32 RI=1.78
(3) L1:L2=75:25 RI=1.77
(4) L1:L2=82:18 RI=1.73
1.84
1.80
Scheme 3 Plausible mechanism of CS2/PGE copolymerization.
1.76
1.72
L1
B
S
O
B
S
B
S
S
R
R
R
O
O
S
P
P
O
O
R
S
R
O
R
S
400
500
600
700
800
P
CS2
R
Wave Length (nm)
C3
Figure 3 Variation of refractive index ((1)entry 7, Table 2; (2)entry 1,
Table 1; (3)entry 2, Table 2; (4)entry 1, Table 2;) via the wavelength of
400-800nm, RI is referred to the refractive index at 590nm.
B
B
S
B
S
R
R
S
P
S
O
O
S
S
S
As we can see, regulation of O-S ER process is an effective
way to adjust sulfur content of the produced poly(thiocarbonate)s
with varying RI. Converting PGE to C3 and consumption of C3 in
the copolymerization process would raise the content of sulfur in
the polymer chain. When the content of L2 is more than 50% in
the polymer chain, ratio of sulfur atom to oxygen atom will exceed
2:1, which is the original ratio of sulfur and oxygen in the
monomer (two sulfur atoms in CS2 and one oxygen atom in PGE).
By mediating the tendency of O-S ER, ratio of L2 ranging from 9%
(entry 5, Table2) to 100% (entries 4 and 8, Table2) was achieved.
We chose poly(thiocarbonate)s of molecule weight around
7.5kg/mol with gradually varied L2 content to test their RI by
spectroscopic ellipsometry (Figure 3). As expected, RI of the
copolymer went up with the increasing of L2 content. Value of RI
at 590nm were 1.73, 1.77, 1.78, 1.79 respectively for copolymers
with L2 content of 18%, 25%, 32%, 62%. When the ratio of L2
linkage was 62%, polythiocarbonate with RI of 1.79 was produced,
which is even higher than that of fully alternating poly(ethylene
trithiocarbonate)s7 for the introduction of aromatic rings.
S
S
S
P
P
O
R
Further scrmbling
R
L2
B
O
B
S
S
S
P
S
S
P
S
S
R
R
R=Ph;
1. Counterpart of ammonium salt;
e.g. DTMeAB
2. Ammonium salt from organic base;
e.g. TEA
B
=
B
=
N
P
N
11
O
N
O
Cl
R
R
Based on these observations, we proposed
a plausible
mechanism for the copolymerization process, and the pathways
were shown in Scheme 3. PGE is initially ring-opened by LPs
followed with a facile CS2 insertion. Actually, similar to the
copolymerization process involving oxetane and CS2, this is still
anticipated to be the rate determining step here19. An alternative
reaction pathway could involve anion attack at the carbon center
Conclusions
We have described here the synthesis of high refractive index
poly(thiocarbonate)s from CS2 and phenyl glycidyl ether (PGE)
employing metal-free Lewis pairs as catalyst. Polythiocarbonates
with only two kinds of linkages were produced with tunable
content. Phenyl thioglycidyl ether (C3) and COS were monitored
as the intermediate of Oxygen-Sulfur Exchange Reaction, and
provided an insight of O-S ER. O-S ER process and constituent of
the product could be easily tuned by varying the reaction
temperature or activity of Lewis base. In virtue of O-S ER,
distribution of oxygen and sulfur element in polymer chain and
of the −O(C=S)S− propagating unit to form
a tetrahedral
intermediate. Following rearrangement at the carbon center of
the tetrahedral intermediate, the anion is regenerated with
concomitant formation of the −O(C=S)O− linkages (L1) ended with
sulfur anion. Successional insertion of CS2 leads to a structure of
−S(C=S)S− linkages (L2). In this view, the content of L1 and L2
Chin. J. Chem. 2019, 37, XXX－XXX
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First author et al.
Report
cyclic product could be changed in a large range, thus the resulted
poly(thiocarbonate)s would be oxygen-rich (RI=1.73) or sulfur-rich
(RI=1.79). Our ongoing efforts are to seek more biological
monomers to copolymerize with CS2 to produce high refractive
index polymer materials.
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Atom-exchange coordination polymerization of carbon disulfide and
propylene oxide by a highly effective double-metal cyanide complex.
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Chin. J. Polym. Sci. 2019, 37, 951-958.
Experimental
Copolymerization of CS2 with PGE catalyzed by Lewis pairs,
experimental details
A 10ml autoclave with magnetic stirrer was first dried in an
oven at 120 °C overnight, then immediately placed into the glove
box chamber. After keeping under vacuum for 2-3 hours, the
reaction vessel was moved into the glovebox with nitrogen
atmosphere. The copolymerization of CS2 with PGE described
below is taken from Entry 1 in Table 1 as an example. Triethyl
amine (TEA, 2.5ul, 0.018 mmol) was firstly added into the reactor
and dissolved in 0.8 mL of CS2. PGE (1.2 mL, 9 mmol) was carefully
added into the vessel after the introduction of an appropriate
amount of TEB (18 μL, 0.018 mmol). The reactor was sealed and
taken out from the glovebox and put into oil bath. The
copolymerization was carried out at 40°C for 8h. The reactor was
then cooled in ice-water bath, and an aliquot was then taken from
the resulting crude product for the determination of constituent
of the product by 1H NMR spectrum. The crude product was
quenched with acetic acid in ethyl alcohol (1 mol/L), and it divided
into two parts, solid part and liquid part. The solid part was
dissolved with CH2Cl2 and then precipitated by ethyl alcohol, then
the copolymer was collected by centrifugation and dried in
vacuum at 40 °C overnight. The cyclic product in liquid part was
collected by centrifugation.
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a semicrystalline
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[16] Luo, M.; Zhang, X. H.; Du, B. Y.; Wang, Q.; Fan, Z. Q. Well-defined high
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Polym. Chem. 2015, 6, 6955-6958.
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alternating copolymerization of carbonyl sulfide with racemic propylene
oxide. Macromolecules 2013, 46, 5899-5904.
[19] Luo, M.; Zhang, X. H.; Darensbourg, D. J. An investigation of the
pathways for oxygen/sulfur scramblings during the copolymerization of
carbon disulfide and oxetane. Macromolecules 2015, 48, 5526-5532.
[20] Diebler, J.; Spannenberg, A.; Werner, T. Atom economical synthesis of di-
and trithiocarbonates by the lithium tert-butoxide catalyzed addition of
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7480-7489.
[21] Diebler, J.; Komber, H.; Häußler, L.; Lederer, A.; Werner, T.
Alkoxide-Initiated regioselective coupling of carbon disulfide and terminal
epoxides for the synthesis of strongly alternating copolymers.
Macromolecules 2016, 49, 4723-4731.
[22] Darensbourg, D. J.; Wilson, S. J.; Yeung, A. D. Oxygen/sulfur scrambling
during the copolymerization of cyclopentene oxide and carbon disulfide:
selectivity for copolymer vs cyclic [Thio]carbonates. Macromolecules 2013,
46, 8102-8110.
[23] Sun, Z.; Huang, H.; Li, L.; Liu, L.; Chen, Y. Polythioamides of high
refractive index by direct polymerization of aliphatic primary diamines in
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Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
Acknowledgement
X.-H. Zhang gratefully acknowledge the financial support of the
Distinguished Young Investigator Fund of Zhejiang Province
(LR16B040001) and the National Science Foundation of the
People’s Republic of China (no. 21774108).
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Chin. J. Chem. 2019, 37, XXX－XXX
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(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
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Entry for the Table of Contents
Page No.
Title: An Investigation on the Production of
Random Copolymer with Monothiocarbonate
and Trithiocarbonate Units over Cyclic
Thiocarbonate via Metal-free Catalysis
Jia-Liang Yang, Lan-Fang Hu, Xiao-Han Cao, and
Xing-Hong Zhang *
a Department, Institution, Address 1
E-mail:
c Department, Institution, Address 3
E-mail:
b Department, Institution, Address 2
E-mail:
Chin. J. Chem. 2018, template
© 2018 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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