Erythritol Dicarbonate as Intermediate for Solvent- and Isocyanate-Free Tailoring of Bio-Based Polyhydroxyurethane Thermoplastics and Thermoplastic Elastomers

Article abstract of DOI:10.1021/acs.macromol.6b02787

The highly reactive [4,4′-bi(1,3-dioxolane)]-2,2′-dione (BDC), also being referred to as erythritol dicarbonate and butadiene dicarbonate, enables the facile isocyanate-free tailoring and melt-processing of bio-based polyhydroxyurethane (PHU) materials. Both the direct carbonation of erythritol and the chemical fixation of CO₂ with 2,2′-bioxirane, obtained by epoxidation of bioethanol-derived butadiene, afford high purity BDC in high yields. According to the FTIR spectroscopic model study BDC reacts with primary alkylamines at room temperature even in the absence of catalysts. High BDC reactivity is essential for producing high molar mass linear PHU thermoplastics via melt-phase polyaddtition with aliphatic diamines. Opposite to conventional isoycanate-mediated polyurethane syntheses erythritol units are incorporated into the polyurethane backbone without requiring the use of protective groups. As a function of the diamine structures and copolymer compositions the PHU properties vary from hard to soft and elastomeric. Typically isophorone diamine (IPDA) and trimethylhexamethylenediamine (TMHMDA) serve as building blocks for hard segments whereas highly flexible diamines such dimer fatty acid-derived diamidoamines render PHU soft and elastomeric. This study elucidates how copolymer composition and reaction parameters such as temperature, catalyst, and stabilizer addition influences PHU molar masses as well as mechanical and thermal properties. For the first time, owing to extraodinary BDC reactivity, melt-phase BDC polyaddition with diamines is competitive with conventional reactive processing of polyurethane thermoplastics using isocyanates. Moreover this versatile isocyanate-free synthetic route offers a great variety of options for fabricating unconventional bio-based PHUs and carbohydrate urethanes unparalleled by conventional polyurethanes.

Full text of DOI:10.1021/acs.macromol.6b02787

Article
pubs.acs.org/Macromolecules
Erythritol Dicarbonate as Intermediate for Solvent- and Isocyanate-
Free Tailoring of Bio-Based Polyhydroxyurethane Thermoplastics
and Thermoplastic Elastomers
Stanislaus Schmidt,†,‡,§ Felix J. Gatti,† Manuel Luitz,† Benjamin S. Ritter,†,‡ Bernd Bruchmann,*,§
and Rolf Mulhaupt*,†,‡
̈
†Institute for Macromolecular Chemistry, Stefan-Meier Strasse 31, D-79104 Freiburg, Germany
‡Freiburg Materials Research Center, Stefan-Meier Strasse 21, D-79104 Freiburg, Germany
§JONAS - Joint Research on Advanced Materials and Systems, Advanced Materials & Systems Research, BASF SE, Carl-Bosch-Strasse
38, 67056 Ludwigshafen, Germany
S
* Supporting Information
ABSTRACT: The highly reactive [4,4′-bi(1,3-dioxolane)]-
2,2′-dione (BDC), also being referred to as erythritol
dicarbonate and butadiene dicarbonate, enables the facile
isocyanate-free tailoring and melt-processing of bio-based
polyhydroxyurethane (PHU) materials. Both the direct
carbonation of erythritol and the chemical fixation of CO2
with 2,2′-bioxirane, obtained by epoxidation of bioethanol-
derived butadiene, afford high purity BDC in high yields.
According to the FTIR spectroscopic model study BDC reacts
with primary alkylamines at room temperature even in the
absence of catalysts. High BDC reactivity is essential for
producing high molar mass linear PHU thermoplastics via melt-phase polyaddtition with aliphatic diamines. Opposite to
conventional isoycanate-mediated polyurethane syntheses erythritol units are incorporated into the polyurethane backbone
without requiring the use of protective groups. As a function of the diamine structures and copolymer compositions the PHU
properties vary from hard to soft and elastomeric. Typically isophorone diamine (IPDA) and trimethylhexamethylenediamine
(TMHMDA) serve as building blocks for hard segments whereas highly flexible diamines such dimer fatty acid-derived
diamidoamines render PHU soft and elastomeric. This study elucidates how copolymer composition and reaction parameters
such as temperature, catalyst, and stabilizer addition influences PHU molar masses as well as mechanical and thermal properties.
For the first time, owing to extraodinary BDC reactivity, melt-phase BDC polyaddition with diamines is competitive with
conventional reactive processing of polyurethane thermoplastics using isocyanates. Moreover this versatile isocyanate-free
synthetic route offers a great variety of options for fabricating unconventional bio-based PHUs and carbohydrate urethanes
unparalleled by conventional polyurethanes.
engineered expanded multiphase TPUs (Infinergy) as shoe
sole materials for “Energy Boost” running shoes by joining
together the beneficial properties of TPUs and foams.9 Because
of the resilience of tailored TPUs, the sole springs back into its
original shape immediately after impact. Hence, this rebound
effect enables efficient dampening and the runners use up
considerably less energy. In view of sustainability and green
chemistry, it is highly desirable to employ renewable resources
and to substitute toxic and highly moisture sensitive isocyanate
intermediates without impairing TPU melt processing. In
traditional isocyanate-based polyurethane chemistry bio-based
feedstocks are employed as alternative to substitute fossil
resources in manufacturing of isocyanates and polyols. For
INTRODUCTION
■
Tailored linear polyurethanes are melt-processable by extrusion
and injection molding on heating, harden on cooling, and
enable multiple thermal reprocessing steps without sacrificing
their structural integrity. Albeit thermoplastic polyurethanes
(TPU) represent only 5% of the total polyurethane
consumption, they serve the needs of diversified markets
ranging from engineering thermoplastics to thermoplastic
elastomers. Typical TPU applications include textiles, footwear,
tubes, sheets, films, protective coatings, and adhesives.1,2
Balancing of soft and hard segments in multiphase TPUs
governs mechanical and thermal properties as well as solvent
and wear resistance. Since several decades multiphase TPUs are
fabricated by polyaddition of aromatic and aliphatic diisocya-
nates with short-chain diols such as butanediol together with
flexible long-chain diols such as polyester or polyether diols,
respectively.3−8 In 2013, BASF SE jointly with Adidas
Received: December 26, 2016
Revised: February 28, 2017
© XXXX American Chemical Society
A
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Scheme 1. Routes to Erythritol Dicarbonate (BDC) from Erythritol and Butadiene
example, the phosgenation of decarboxylated lysine yields
pentamethylene diisocyanate as bio-based diisocyanate mono-
mer.10 Since many years sugar polyols, prepared by
propoxylation and ethoxylation of sugars, serve as polyol
components of cross-linked polyurethanes.11−19 However, the
incorporation of polyfunctional sugars into linear polyurethanes
is much more difficult and requires the use of protective groups
to render them difunctional.11,12 In view of green chemistry,
high resource efficiency, and economy, the use of protective
groups is prohibitive. During recent years considerable progress
has been made regarding the development of non-isocyanate
polyhydroxyurethanes, also being referred to as nonisocyanate
polyurethane (NIPU), and prepared by polyaddition of
polyfunctional cyclic carbonates with polyfunctional aliphatic
amines.13−17 Owing to the rather low reactivity of most
polyfunctional carbonates, readily available by carbonation of
bio-based polyols or epoxidized terpenes and plant oils,
respectively, the PHU synthesis requires the addition of
catalysts such as triethylamine, organometallic complexes,
diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]-
undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene
(TBD), and thiourea.18−21 Among them, TBD is emphasized
for its high activity.22,23 Today even in the presence of catalysts
PHU synthesis by solution polyaddition requires elevated
temperatures and prolonged reaction times of several
hours.11,12,14,24−28 According to Besse et al., long polymer-
ization time accounts for massive side reactions which disrupt
the precise stoichiometry, thus preventing molar mass buildup
even in the presence of small amounts of monofunctional
byproducts.3,13,14,29−31 It is an important challenge in TPU
synthesis to enhance the polymerization rate of difunctional
cyclic carbonates without impairing stoichiometry in order to
produce high molar mass TPU within only a few minutes,
typical for industrial reactive processing such as reactive
injection molding and reactive extrusion. At Union Carbide
Whelan et al. recognized first that [4,4′-bi(1,3-dioxolane)]-2,2′-
dione (BDC), also known as erythritol dicarbonate or
butadiene dicarbonate, respectively, reacted with
hexamethylenediamine (HMDA) in dimethyl sulfoxide solution
at room temperature to yield linear PHU.32 However, they did
not report on either reaction kinetics or basic structure/
property correlations. To the best of our knowledge, no
attempts have been made to produce erythritol-based linear
TPUs by solvent-free polyaddition and reactive melt process-
ing. Erythritol, a common sweetener for diet food, is readily
available by fermentation of bio-based feedstocks like glucose,
sucrose, and other sugars.33−36 Carbonation by transester-
ification of meso-erythritol with dialkyl carbonates gave rather
poor yields of impure erythritol dicarbonate which did not
qualify as monomer for polyaddition without extensive
purification. As reported by Rokicki et al., a monofunctional
cyclic ether carbonate is formed as byproduct (see Scheme
1).32,37−39 The presence of small amounts of such monofunc-
tional cyclic carbonates drastically impairs PHU molar mass.
Herein we report on the synthesis of high purity BDC from
meso-erythritol by transesterification with diphenyl carbonate
without encountering monofunctional cyclic carbonate as
undesirable byproduct (see Scheme 1, route A). In a highly
atom-efficient alternative synthetic pathway BDC is obtained
without byproducts by epoxidation of butadiene followed by
chemical CO2 fixation (see Scheme 1, pathway B).37 Bio-based
butadiene can be gained from bioethanol.40 We examine the
influences of amine structures, catalyst, and stabilizer addition
on PHU formation (see Scheme 2) in order to enhance
polymerization rate without encountering side-reactions in
melt-phase polyaddition.
Scheme 2. Solvent-Free Polyaddition of BDC with Diamines
IPDA, TMHMDA, and the Dimer-Fatty-Acid-Based
Amidoamine DFS-1,6-AA To Produce
Polyhydroxyurethanes (PHU)
This study elucidates how the choice of diamine structures,
particularly blending together rigid diamines with flexible
diamines such as dimer fatty acid-based diamidoamines,
governs thermal and mechanical properties of bio-based PHU
thermoplastics and thermoplastic PHU elastomers.
EXPERIMENTAL SECTION
■
Chemicals. DMSO (99%) and ethylene carbonate (EC, 99%) were
obtained from Merck, THF (99%) was from Carl Roth, tetrabutyl-
ammonium bromide (TBAB, 99%) and hexamethylenediamine
(HMDA) were from Alfa Aesar GmbH & Co. KG. Carbon dioxide
(N45) was obtained from Air Liquide. All deuterated solvents were
purchased from Deutero GmbH. The dimer fatty acid Pripol 1009 was
supplied by Croda GmbH and acetic anhydride (99%) by Fluka
Analytical. The diamines such as 2,2,4-trimethylhexamethylenediamine
(TMHMDA), isophoronediamine (IPDA), triethyl orthoformiate
(99%), DABCO, ethanol (99%), meso-erythritol (99%), 1,8-
diaminooctane (OCDA), and 1,12-diaminododecane (DDA) were
purchased from Sigma-Aldrich Chemie GmbH. Irgafos 168 and
Irganox 1010 were supplied by BASF SE.
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Scheme 3. BDC Preparation from 2,2′-Dioxirane and meso-Erythritol
FT-IR Spectroscopy. Fourier transform infrared spectra were
measured on a Vector 22 from Bruker. The attenuated total reflection
measurements were recorded by using 30 scans between 4000 and 800
cm−1.
Thermogravimetric Analysis. Simultaneous thermal analysis
(STA 409 from Netzsch) was used to study the degradation and the
mass loss in an air atmosphere using a temperature range varying
between 50 and 650 °C at 10 K/min.
NMR Spectroscopy. NMR spectroscopy measurements were
recorded at a frequency of 300 MHz using the Avance II spectrometer
from Bruker. Acetone-d6, CDCl3, and DMSO-d6 were used as
deuterated solvents.
Differential Scanning Calorimetry. A DSC-1 PerkinElmer and a
Netzsch DSC 204 F1 Phoenix (heating rate 10 or 20 K/min) were
used to determine the thermal properties.
Stress−Strain Characterization. Zwick Z005 (Ulm, Germany,
ISO527A1, 50 mm/min) was used to characterize the mechanical
properties of injection-molded dog bone-shaped testing specimen.
Elongation at break and Young’s modulus and were determined at
room temperature by using the statistical average of at least five testing
samples.
5.20 (m, 2 H, CH2) ppm. 13C NMR (75 MHz, DMSO-d6): δ = 65.19
(2 C, CH2), 75.93 (2 C, CH2), 154.63 (2 C, CO) ppm.
Dimer Fatty Acid-Based Diamidoamine (DFS-1,6-AA). Pripol
1009 (250 g, 0.441 mol) was mixed with triethyl orthoformiate (146
mL, 131 g, 0.887 mol, 2.10 equiv) and EtOH (240 mL), and few drops
of sulfuric acid were added. The mixture was refluxed for 240 h. All
byproducts were distilled off in a vacuum. The remaining viscose
mixture was dissolved in Et2O and extracted with H2O (3 × 200 mL).
Organic phases were dried first over MgSO4 and afterward overnight
in a vacuum at 60 °C. 1H NMR (299.87 MHz; CDCl3): δ = 0.70−1.77
(m, 67.80 1-H, CH2), 2.27 (t, 4.17 3-H, CH2), 4.11 (q, 4.0 2-H, CH2)
ppm.
The resulting dimer fatty acid diethyl ester (95.9 g, 154 mmol) was
mixed with HMDA (251 g, 2.17 mol, 14.0 equiv) for 170 h at 115 °C.
After complete conversion excessive HMDA was distilled off. The
residual viscose oil was dissolved in Et2O (300 mL) and extracted with
water (5 × 500 mL). All organic phases were combined and dried at
60 °C in a vacuum for 24 h. DFS-1,6-AA (n(Amin) = 2.33 0.20
mol/kg) was gained as a viscose brown oil. A dimer content of 14.3
1
1
mol % was determined by H NMR spectroscopy. H NMR (299.87
MHz; CDCl3): δ = 0.23−1.92 (m, 74.46 2-H, CH2), 2.08 (t, 4.24 4-H,
CH2), 2.61 (t, 4.24 1-H, CH2), 3.16 (q, 4.00 3-H, CH2) ppm.
General Procedure for PHU Preparation in DMSO Solution.
The aliphatic diamine (HMDA, OCDA, DDA) was dissolved in
DMSO (1 mol/L) at 100 °C. An exact equivalent of BDC was added
to this mixture. After 14−20 h of stirring at 100 °C the reaction was
cooled down to room temperature. By addition of water the polymer
was precipitated as a colorless solid. The product was dried at 60 °C in
a vacuum.
Size Exclusion Chromatography. The molar mass was
determined using THF and DMAc solution by means of a SECurity
GPC-System (Agilent 1200) from PSS Polymer Standards Service
GmbH. Three SEC columns with pore size of (102, 10−3, and 10−4
Å
for THF and 30 and 1000 Å for DMAc) from PSS Polymer Standards
Service GmbH were used in order fractionate the polymer samples
using the refractive index detector G136A and VW-detector G1314B
from Agilent Technologies. Polystyrene was used as standard for
samples in THF and PMMA for polymers measured in DMAc at 85
°C. All PHU samples were acetylated with acetic anhydride prior to
the SEC measurement.
Compounder. The reactive compounding was made using a Micro
5 cm3/15 cm3 twin-screw compounder from Xplore in a temperature
range between 70 and 140 °C. The speed of the twin screw was kept
constantly at 120 rpm. The gained force−time and temperature−time
diagrams were recorded by using DSM Xplore as software.
Synthesis of BDC from 2,2′-Bioxirane. Tetrabutylammonium
bromide (TBAB, 0.96 mmol, 312 mg, 0.50 mol %) was added to an
autoclave which was flushed with CO2. Under a CO2 atmosphere 2,2′-
dioxirane (15 mL, 16.7 g, 0.194 mol) was added. The carbonation took
place at 30 bar and 120 °C for the duration of 6 h. The solid product
was recrystallized from acetone and dried overnight in a vacuum. BDC
was obtained as a colorless powder (90%) melting at 169 °C (lit.: 90%,
Tm 166 °C).37 1H NMR (299.87 MHz, acetone-d6): δ = 4.38−4.47 (m,
2 H, 1−CH2), 4.60−4.70 (t, 8.8 Hz, 2 H, CH2), 5.04−5.13 (m, 2 H,
CH) ppm.
BDC from meso-Erythritol. Diphenyl carbonate (DPC, 92.1 g;
0.43 mol; 2.10 equiv), Zn(OAc)2·2H2O (451.1 mg; 1 mol %), DMSO
(45 mL, 4.5 mol/L), and meso-erythritol (25 g, 0.21 mol) were added
to a flask. This mixture was heated at 30 mbar to 120 °C and stirred
for 19 h. During the conversion DMSO and phenol were distilled off,
and the residual brown solid was recrystallized from acetone. BDC was
gained as a colorless crystalline product (80−90%) with a melting
point of 169 °C (lit.: 168−170 °C)39,41 which has a purity of 99%
(determined by NMR spectroscopy). 1H NMR (299.87 MHz, DMSO-
d6): δ = 4.35−4.45 (m, 2 H, CH2), 4.58−4.68 (m, 2 H, CH2), 5.12−
BDC_HMDA. 1H NMR (299.87 MHz; DMSO-d6): δ = 1.1−1.5 (m,
CH2), 2.8−3.1 (m, CH2), 3.4−3.9 (m, CH−OH), 4.0−4.3 (m, O
C−CH2 4.5−4.7 (m, OC−CH) 4.9−5.1 (m, OH), 6.6−7.2 (m, NH)
ppm.
BDC_OCDA. 1H NMR (299.87 MHz; DMSO-d6): δ = 1.1−1.5 (m;
CH2), 2.8−3.1 (m, CH2), 3.5−3.9 (m, CH−OH), 4.0−4.7 (m, O
CH, OC−CH2), 4.8−5.1 (m, OH), 6.6−7.2 (m, NH) ppm.
1
BDC_DDA. H NMR (299.87 MHz; DMSO-d6): δ = 1.2−1.7 (m,
CH2), 2.9−3.2 (m, CH2, 1/1′), 3.5−4.0 (m, CH−OH), 4.0−4.7 (m,
OCH, OC−CH2), 4.9−5.2 (m, OH), 6.7−7.2 (m NH) ppm.
General Procedure for Melt-Phase Polyaddition of BDC with
Diamines. Kinetic Study. DFS-1,6-AA was warmed to 70 °C and
mixed with the exact stoichiometric amount of BDC and the additive,
e.g. DABCO, Irgafos168, or the blend 50 wt % Irganox1010/50 wt %
Irgaphos168, (0.5 wt %) for 1 min. The viscous mixture was injected
into the compounder (Micro 5 cm3/15 cm3 twin-screw compounder/
Xplore), which was set at 80 °C. The polymer buildup was monitored
for 85 min, every 10 min a sample was taken. To avoid polymer
degradation by shear forces torque was kept almost below 3000 N.
When achieving this force value, the temperature was increased to 100
°C.
General Preparation of Homo- and Copolymers. The mixture of
catalyst (0.5 wt %), stabilizer (0.5 wt %), and the diamines was
warmed up to 70 °C. Then the exact stoichiometric amount of BDC
was added, and the mixture was stirred for few minutes. The viscous
reaction mixture was injected into the compounder (Micro 5 cm3/15
cm3 twin-screw compounder/Xplore) and processed at 80 °C until the
force increased at a maximum torque of 3000 N. In such case the
temperature was then increased in 20 °C intervals up to 130 °C.
Increasing molecular weight of the resulting polymers is accompanied
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Figure 1. FTIR spectroscopic analyses of reaction kinetics monitoring the reaction of EC, BDC (OC: 1800 cm−1) with ethanolamine at room
temperature in the absence of solvent at 1, 15, and 32 min for BDC and at 1, 60, and 120 min for EC yielding urethane (OC: 1700 cm−1).
Scheme 4. Solution Polyaddition of BDC with 1,6-Hexamthelenediamine (HMDA, x = 6), 1,8-Octamethylenediamine (OCDA,
x = 8), and 1,12-Dodecanediamine (DDA, x = 12) in DMSO (1 mol/L) at 100 °C
by higher melt viscosity and increased shear forces. DFS-1,6-AA and
the used additive (0.5 wt %) were mixed at 70 °C for several minutes.
After exactly 20 min the prepared polymer was injected at 130 °C and
9 bar into the mold to give dog-bone-shaped testing specimens. To
prevent side reactions, the conversion temperature was always kept
below 140 °C.
disclosed that BDC reacted with primary alkylamines in DMSO
solvent at ambient temperature.37 In order to examine BDC
conversion at room temperature in the absence of solvents, the
reactions of both BDC and the corresponding monofunctional
ethylene carbonate with ethanolamine were monitored by
means of FTIR spectroscopy using identical reaction
conditions. In the FTIR traces (see Figure 1) of the BDC/
ethanolamine reaction the IR band at 1800 cm−1 corresponds
to the stretching vibration of the carbonyl group of the cyclic
carbonate while the signal at 1700 cm−1 represents the carbonyl
group of the formed PHU urethane bond. Full BDC conversion
with ethanolamine was achieved at room temperature within 32
min.
In sharp contrast, the corresponding bulk reaction of the
much less reactive ethylene carbonate with ethanolamine was
significantly slower, requiring 120 min for achieving full
conversion. This confirms that the inductive effect of the
vicinal carbonate group renders BDC significantly more
reactive. This is in accordance with a similar substituent effect
observed for sorbitol tricarbonate.43
Linear PHUs Prepared by Solution Polyaddition. Albeit
BDC is known for several years only Whelan et al. reported on
BDC polyaddition with diamines in DMSO to produce linear
PHUs at ambient temperature.32 However, they did not
comment either on polymerization kinetics, molecular PHU
architectures, or PHU material properties. Therefore, we
investigated DMSO solution polyaddition of BDC with 1,6-
hexamethylenediamine (HMDA), 1,8-octamethylenediamine
(OCDA), and 1,12-dodecamethylenediamine (DDA) in
DMSO (1 mol/L) at 100 °C, following procedures reported
by Kihara et al. for the preparation of other linear PHUs.44
Scheme 4 displays the reaction pathways leading to PHU
isomers containing either secondary hydroxyl groups or
RESULTS AND DISCUSSION
■
BDC Preparation. As is illustrated in Schemes 1 and 3, the
carbonation of both meso-erythritol and 2,2′-bioxirane affords
BDC. As compared to conventional transesterification of meso-
erythritol with dimethyl carbonate, accompanied by monofunc-
tional carbonate byproduct formation, both BDC yield and
purity significantly improved when meso-erythritol was trans-
esterified with diphenyl carbonate (DPC) in DMSO solution at
120 °C in the presence of zinc acetate as catalyst.37−39 During
this transesterification reaction DMSO together with phenol,
which evolved as byproduct, were continuously removed by
vacuum distillation. In sharp contrast, the carbonation of 2,2′-
dioxirane (BDO), readily available by epoxidation of butadiene,
proceeded at 120 °C and 30 bar CO2 pressure in the presence
of tetrabutylammonium bromide (TBAB) as catalyst without
requiring either solvent addition or removal of byproducts.
Hence, this bulk carbonation represents an atom-efficient route
to BDC. As confirmed by means of ESI, NMR, and FTIR
spectroscopy (see Supporting Information) both routes afford
high purity BDC melting at 169 °C and containing 55.5 wt %
chemically fixed CO2.
Model Reactions of BDC with Amines. The accelerating
effect of vicinal cyclic carbonate groups was already predicted
by Goldstein et al., who investigated the aminolysis kinetics of
carbohydrate-based cyclic carbonates in DMSO.42 The high
reactivity of BDC was recognized first by Whelan et al., who
D
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1
Figure 2. H NMR spectrum (DMSO-d6) of PHU isomers (BDC_HMDA, x = 4) prepared by polyaddition in DMSO solution (1 mol/L) at 100
°C.
Table 1. Molar Mass and Thermal Properties of PHUs Prepared by Solution Polyaddition of BDC with HMDA, OCDA, or
a
DDA in DMSO at 100 °C
b
c
c
b
d
be
,
polymer
Mn,NMR [g/mol]
Mn,SEC [g/mol]
Mw [g/mol]
PDI
P
[%]
98
Tg [°C]
Tm [°C]
(prim OH/sec OH) [%]
BDC-HMDA
BDC-OCDA
BDC-DDA
14800
8900
9700
9600
23100
26900
2.4
2.8
3.1
9
9
34/66
35/65
97
98
10000
31300
11
141
a
b
c
1
Solution polyaddition (DMSO; 1 mol/L) 14−19 h at 100 °C. Determined by H NMR spectroscopy. SEC of acetylated PHUs in DMAc,
d
e
solution using a PMMA standard, 85 °C; DSC 10 K/min. Conversion (P) as determined by 1H NMR spectroscopy. Molar ratio (OH) of primary
(Prim) and secondary (Sec) hydroxyl groups as determined by H NMR spectroscopy.
1
primary hydroxyl groups together with secondary hydroxyl
groups in the backbone. This PHU isomer formation is
accounted for by different ring-opening pathways following the
attack of the amine at the carbonyl group.
and 4.70 ppm. The PHU molar masses determined by means
size exclusion chromatography (SEC) using PHU solutions in
DMAc and by H NMR spectroscopic end-group analysis are
1
listed in Table 1. The degree of polymerization was determined
from the signal intensity ratio of 1H NMR signals
corresponding to the remaining amino group (2.65 ppm) at
the PHU chain end and the methylene group (3.0 ppm)
allocated next to the urethane in the PHU backbone.
Independent of the diamine type, the molar ratio of primary
and secondary hydroxyl groups was around 0.5. Preferably,
erythritol 1,2-diol units are incorporated in the PHU backbone.
Owing to the extremely low PHU solubility in THF, CHCl3, or
DMAc, hydroxyl and amine groups were acetylated with acetic
anhydride prior to SEC analysis in order to enhance PHU
solubility. It should be noted that this postpolymerization
functionalization markedly increased PHU molar mass.
Regardless of the diamine type and postpolymerization
functionalization all PHU molar masses (Mw) were quite low
and varied between 20 and 30 kg/mol. This is in accordance
with observations by Whelan et al. for BDC-based NIPU and
also with those of Kihara et al., who prepared other PHUs using
the identical solution process conditions.32,44 Such low PHU
molar masses do not qualify for industrial applications. Most
likely owing to low PHU molar masses the type of diamine had
little influence on glass transition temperatures ranging between
9 and 11 °C. In thermal analyses by DSC (see Table 1) only
The progress of the polyaddition was monitored by means of
FTIR spectroscopy which confirmed full BDC conversion and
successful urethane formation. All polymers were precipitated
in water, washed with water, and dried in a vacuum at 60 °C for
1
24 h. The polymer structure was characterized by H NMR
1
spectroscopy. Figure 2 displays the H NMR spectrum of the
BDC-HMDA polymer. The hydrogen atoms allocated in the
aliphatic chain segment, marked as (2), correspond to the two
1H NMR signals at 1.15 and 1.50 ppm, whereas the aliphatic
methylene hydrogen atoms next to the urethane group, marked
as (1) and (3), are assigned to the broad signal at 2.90 ppm.
Primary and secondary hydroxyl groups, labeled (5) and (5*),
correspond to the two multiplet signals at 3.85 and 3.53 ppm
(see Figure 2). The ratio between the primary and secondary
1
OH groups of (35/65) was also determined by H NMR
spectroscopy. The formation secondary hydroxyl groups
indicates that the ring-opening occurred by thermodynamic
control. This is in accordance with other reports on the
preparation of linear PHUs via polyaddition of cyclic
carbonates and diamines.18,45 The hydrogen atoms labeled
(4) and (5) of the methylene groups allocated in the α-position
of the urethane oxygen atom account for broad signals at 4.50
E
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BDC−DDA was semicrystalline and exhibited a melting
temperature of 141 °C.
Linear PHUs Prepared by Melt-Phase Polyaddition.
Short polymerization times and fast molar mass buildup are
essential for a reasonable technical process since side reactions,
high viscosity, and crystallization restrict diffusion and lower
reactivity of the end groups. Moreover, in order to qualify for
reactive injection molding and reactive extrusion successfully
competing with the exceptionally rapid polyaddition reaction of
isocyanates, the polyaddition reaction of the cyclic carbonates
should take place within minutes. To date, unlike BDC, most
conventional difunctional cyclic carbonates even in the
presence of catalysts exhibit poor reactivity and fail to produce
linear PHUs by melt-phase polyaddition and reactive
compounding within a few minutes. As is illustrated in Scheme
5, in order to tailor linear PHU thermoplastics and thermo-
Figure 3. Weight-average molar mass (Mw) of BDC-DFS-1,6-AA as a
function of polymerization time in the absence (left) and the presence
of 0.5 wt % additives such as DABCO, Irganox1010/Irgafos168 (50 wt
%/ 50 wt %) and Irgafos168. BDC was polymerized with
stoichiometric amounts of DFS-1,6-AA for 40 min at 80 °C and 50
min at 100 °C.
Scheme 5. PHU Building Blocks Comprising Rigid Diamines
(IPDA, TMHMDA, HMDA, DDA) and Flexible Dimer Fatty
Acid-Based Diamidoamines (DFS-1,6-AA)
amino groups during this reaction which impaired stoichiom-
etry and thus lowered molar mass. From the torque
measurements it became apparent that the molar mass increase
occurred within 20 min at 100 °C in the presence of
antioxidant and catalyst.
For the evaluation of the thermal and mechanical properties
of BDC homo- and copolymers stoichiometric amounts of
BDC and diamines were premixed together with 0.5 wt % TBD
catalyst and 0.5 wt % Irganox1010/Irgafos168 (50 wt %/ 50 wt
%) at 70 °C for 2 min and injected into the mini-twin-screw
extruder (Xplore). After melt-processing for 20 min at 80−130
°C the samples were recovered and injection-molded at 135 °C.
In order to balance soft and hard segments, 4, 10, and 20 wt %
of the flexible DFS-1,6-AA was substituted by rigid diamines
such as IPDA or TMHMDA, respectively. All samples were
characterized by FTIR and NMR spectroscopy, differential
scanning calorimetry (DSC), and thermogravimetric analysis
(TGA). In order to improve their solubility all homo- and
copolymers were acetylated with acetic anhydride prior to SEC
analysis. Molar masses, molar mass distributions, and thermal
and mechanical properties are summarized in Table 2. All BDC
homo- and copolymers were melt-processable by injection
molding. The copolymerization of BDC with flexible DFS-1,6-
AA afforded a highly flexible soft PHU exhibiting low glass
transition temperature of −5 °C and low Young’s modulus of
90 MPa in conjunction with a high elongation at break of 130%.
The stiffness of the BDC copolymers gradually increased with
increasing content of rigid comonomers such as IPDA or
TMHMDA, respectively. On increasing the rigid diamine
content to 20 wt % the Young’s modulus increased from 90 to
1470 MPa (+1600%) for DFS-1,6-AA/IPDA copolymers and
to 980 MPa (+1200%) for DFS-1,6-AA/TMHMDA copoly-
mers. The glass transition temperatures increased from −5 to
24 °C for IPDA- and 27 °C for TMHMDA-copolymers. As
compared to IPDA copolymers, the TMHDMA copolymeriza-
tion afforded markedly higher molar masses of the copolymer.
This could be attributed to the higher reactivity of the
TMHDMA amine groups with respect to IPDA. Moreover, the
higher rigidity of IPDA, as evidenced by the higher glass
transition temperature of the homopolymer, would require
higher processing temperatures which are not feasible due to
plastic elastomers by balancing hard and soft segments, BDC
was polymerized with rigid diamines such as HMDA, DDA,
2,2-dimethyl-4-methylhexamethylenediamine (TMHMDA),
and isophoronediamine (IPDA) in conjunction with flexible
dimer fatty acid-based diamidoamines (DFS-1,6-AA) obtained
by end-capping dimer fatty acid with HMDA.
The melt-phase polyaddition of BDC with diamine was
performed using a twin-screw miniextruder (Micro 5 cm3/15
cm3 twin-screw compounder, XPLORE). It should be noted
that the polymerization temperature of BDC polyaddition in
melt phase is restricted to temperatures below 140 °C. Above
140 °C BDC alkylation, accompanied by evolution of carbon
dioxide, competes with urethane formation and accounts for
foaming and severely impairing stoichiometry required to afford
high molar masses. In order to examine the influence of
catalysts and antioxidants, BDC was polymerized with the
flexible dimer−amidoamine DFS-1,6-AA in the presence of
additives such as DABCO catalyst, phosphite processing
stabilizer (Irgafos168), phenolic antioxidant (Irganox1010),
and the corresponding stabilizer blend (50 wt % Irganox1010/
50 wt % Irgaphos168). Typically, DFS-1,6-AA, BDC, and the
additive such as DABCO, Irgafos168, and the blend of 50 wt %
Irganox1010/50 wt % Irgaphos168 (0.5 wt %) were premixed
at 70 °C for 1 min and then injected into the compounder at 80
°C. Owing to the rapid increase of viscosity, the temperature
was increased to 100 °C and kept constant until the end of the
experiment. Samples were collected after 15, 35, 55, 75, and 85
min. At low temperature the increase of molar mass was
comparable in the presence and in the absence additives. Upon
heating to 100 °C, the addition of catalyst and especially the
addition of antioxidant markedly increased weight-average
molar mass, as determined by SEC measurements (see Figure
3). Most likely, the antioxidant prevented oxidation of the
F
DOI: 10.1021/acs.macromol.6b02787
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Macromolecules
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Table 2. Molar Mass and Thermal Properties of BDC Homo- and Copolymers Prepared by Melt-Compounding for 20 min at
80−130 °C
a
a
IPDA or
TMHMDA [wt %]
IPDA or TMHMDA
[mol %]
Tg
Tm
Mn
Mw
Young’s
elongation at
d
d
polymer
BDC/DFS-1,6-AA
[°C]
[°C]
[g/mol] [g/mol] modulus [MPa]
break [%]
b
b
b
b
b
c
b
b
b
b
b
c
0
4
0
20
−5
−5
−3
24
88
13
16
27
41
133
133
111
9000
5900
6100
5900
2200
10000
9600
8500
12400
26200
20600
18800
14800
4700
90 20
80 30
130 40
120 30
40 40
<1
BDC/DFS-1,6-AA/IPDA_1
BDC/DFS-1,6-AA_IPDA_2
BDC/DFS-1,6-AA_IPDA_3
BDC/IPDA
10
21
100
4
40
300 40
1470 140
60
100
20
BDC/DFS-1,6-AA/TMHMDA_1
BDC/DFS-1,6-AA/TMHMDA_2
BDC/DFS-1,6-AA/TMHMDA_3
42000
44100
33600
30800
40 10
380 70
980 50
220 20
c
c
9
40
<1
<1
c
c
20
60
b
b
BDC/TMHMDA
100
100
a
b
c
d
DSC: 10 K/min. SEC (THF, PS standard). SEC (DMAc, PMMA standard, 85 °C). Tensile testing: ISO 527A1.
side reactions. It should be noted that both BDC/IPDA (Tg =
88 °C) and BDC/TMHDMA (Tg = 41 °C) homopolymers
were extremely brittle.
phenols during melt-phase polymerization prevents side
reactions which impair stoichiometry and PHU molar masses.
The melt-phase polyaddition of TMHMDA with BDC affords
linear PHU with weight-average molar mass of 44 kg/mol
within 20 min at 100 °C. This solvent-free polyaddition is
superior to conventional BDC solution polymerizations
requiring reaction times of several hours and producing
PHUs with much lower molar masses. Especially in the
presence of flexible dimer fatty acid-derived diamidoamine all
resulting BDC copolymers are melt processable by meas of
injection-molding. Combining flexible and rigid diamines
governs the formation of segmented PHU thermoplastics
with properties varying from hard to semicrystalline,
amorphous, flexible, and soft. Progress in BDC-mediated
melt-phase polyaddition holds great promise for the
isocyanate-free formation of polyurethane thermoplastics,
thermoplastic elastomers, and specialty polymers by reactive
extrusion and reactive injection-molding.
According to DSC analyses, only the BDC/DFS-1,6-AA
homopolymers and BDC copolymers with DFS-1,6-AA/IPDA
containing less than 40 mol % of IPDA incorporation were
semicrystalline with melting temperatures varying between 111
and 131 °C. Opposite to IPDA the branched TMHMDA
prevents crystallization during injection molding. This may be
attributed to the stereochemistry of the branched segments in
the PHU backbone. In addition for all polymers any by product
1
formation could be detected by H NMR spectroscopy.
CONCLUSIONS
■
The carbonation of both erythritol and epoxidized butadiene
affords high-purity bio-based [4,4′-bi(1,3-dioxolane)]-2,2′-
dione (BDC) as versatile and highly reactive difunctional cyclic
carbonate intermediate enabling the solvent-free fabrication of
unconventional linear non-isocyanate carbohydrate−urethane
thermoplastics unparalleled by classical polyurethanes. Since
isocyanates readily react with all hydroxyl groups, conventional
polyaddition of erythritol with diisocyanates forms cross-linked
polyurethanes. Hence, protective groups are needed to convert
erythritol into a diol useful as mononmer in conventional
isocyanate-based synthesis of poly(carbohydrate−urethane)s.
Whereas the known erythritol carbonation with dimethyl
carbonate yields BDC together with considerable amounts of
monofunctional cyclic carbonate impurities, the transesterifica-
tion of erythritol with diphenyl carbonates substantially
improves both BDC yield and purity. Neither solvent nor
byproduct removal is required when 2,2′-bioxirane, obtained by
epoxidation of bioethanol-derived butadiene, is converted into
BDC by means of catalytic CO2 fixation. According to FTIR
monitoring of the BDC reaction with amines full BDC
conversion and quantitative urethane formation is achieved at
ambient temperature within a few minutes. This remarkably
high BDC reactivity is by far superior to most other
difunctional cyclic carbonates. Hence, for the first time BDC
enables the rapid melt-phase polyaddition with various aliphatic
diamines to form high molar mass linear PHU thermoplastics
by reactive processing. In sharp contrast, most state-of-the-art
syntheses of linear PHU thermoplastics require solution
polymerization and polymerization times of several hours. It
should be noted that the polymerization temperature is
restricted to temperatures below 150 °C, owing to alkylation
side reactions occurring at higher temperatures. The addition of
catalysts and especially antioxidants such as sterically hindered
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.macro-
mol.6b02787.
SEC, thermic, and mechanic analysis of all materials as
1
also as the FTIR and H NMR spectra; force−time and
temperature−time diagrams (PDF)
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: bernd.bruchmann@basf.com (B.B.).
*E-mail: rolfmuelhaupt@makro.uni-freiburg.de (R.M.).
ORCID
Stanislaus Schmidt: 0000-0002-4534-2552
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge the support by the Ministerium fur
Wissenschaft, Forschung und Kunst Baden-Wurttemberg,
Stuttgart, Germany, and by JONAS−Joint Research Network
on Advanced Materials and Systems, BASF SE, Ludwigshafen,
̈
̈
Germany. Also, we thank Ellen Gunther, Marina Hagios, Alfred
̈
Hasenhindl, and Dr. Victor Hugo Pacheco Torres.
G
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(22) Lambeth, R. Organocatalytic synthesis of (poly)-
hydroxyurethanes from cyclic carbonates and amines. Polymer 2013,
54 (21), 5568−5573.
(23) Chen, Q.; Gao, K.; Xie, H.; Zhao, Z. K.; Bao, M. Preparation of
lignin/glycerol-based bis(cyclic carbonate) for the synthesis of
polyurethanes. Green Chem. 2015, 17, 4546.
REFERENCES
■
(1) Engels, H.-W. Polyurethanes: Versatile Materials and Sustainable
Problem Solvers for Today’s Challenges. Angew. Chem., Int. Ed. 2003,
52 (36), 9422−9441.
(2) Web, K. TPU: Produktion legt jahrlich um 5 Prozent zu, 2013.
̈
Available from:https://www.kunststoffweb.de/ki_ticker/TPU_
Produktion_legt_jaehrlich_um_5_Prozent_zu_t225770,14.07.2016.
(3) Lu, Q.-W.; Hoye, T. R.; Macosko, C. W. Reactivity of common
functional groups with urethanes: Models for reactive compatibiliza-
tion of thermoplastic polyurethane blends. J. Polym. Sci., Part A: Polym.
Chem. 2002, 40 (14), 2310−2328.
(4) Thermoplastische Polyurethan Elastomere (TPU); Elastollan®−
Materialeigenschaften. 2011; Available from: http://www.
polyurethanes.basf.de/pu/solutions/de_DE/function/conversions:/
publish/content/group/Arbeitsgebiete_und_Produkte/
Thermoplastische_Spezialelastomere/Infomaterial/elastollan_
material_d.pdf.
(5) Rogulska, M.; Kultys, A. Aliphatic polycarbonate-based thermo-
plastic polyurethane elastomers containing diphenyl sulfide units. J.
Therm. Anal. Calorim. 2016, 126 (1), 225−243.
(6) Puszka, A.; Kultys, A. New thermoplastic polyurethane
elastomers based on aliphatic diisocyanate. J. Therm. Anal. Calorim.
2017, 128, 407−416.
(7) Terban, M. W.; et al. Structures of Hard Phases in Thermoplastic
Polyurethanes. Macromolecules 2016, 49 (19), 7350−7358.
(8) Li, S.; et al. Synthesis and properties of non-isocyanate aliphatic
crystallizable thermoplastic poly(ether urethane) elastomers. Eur.
Polym. J. 2016, 84, 784−798.
(9) BASF.Infinergy:BASFdevelopsthefirstexpanded TPU,http://
www.polyurethanes.basf.de/pu/solutions/en/content/group/News_
und_Medien/Presseinformationen/Infinergy_BASF_develops_
expanded_TPU, 14.07.2016, 2013.
(10) Fiene Martin, S. E.; Siegel, W.; Freyer, S.; Oskar, Z.; Schulz, G.
(BASF), Process for preparing pentamethylene 1,5-Diisocyanate,
US8044166 (B2), 2011.
(11) Prompers, G.; et al. Polyurethanes with pendant hydroxy
groups: polycondensation of D-mannitol-1,2:5,6-dicarbonate with
diamines. Des. Monomers Polym. 2005, 8 (6), 547−569.
(12) Fidalgo, D. M.; Kolender, A. A.; Varela, O. Stereoregular poly-
O-methyl [m,n]-polyurethanes derived from D-mannitol. J. Polym. Sci.,
Part A: Polym. Chem. 2013, 51 (2), 463−470.
(13) Blattmann, H.; et al. Isocyanate- and Phosgene-Free Routes to
Polyfunctional Cyclic Carbonates and Green Polyurethanes by
Fixation of Carbon Dioxide. Macromol. Rapid Commun. 2014, 35
(14), 1238−1254.
(14) Rokicki, G.; Parzuchowski, P. G.; Mazurek, M. Non-isocyanate
polyurethanes: synthesis, properties, and applications. Polym. Adv.
Technol. 2015, 26 (7), 707−761.
(15) Maisonneuve, L.; et al. Isocyanate-Free Routes to Polyurethanes
and Poly(hydroxy Urethane)s. Chem. Rev. 2015, 115 (22), 12407−
12439.
(16) Kathalewar, M. S.; et al. Non-isocyanate polyurethanes: from
chemistry to applications. RSC Adv. 2013, 3 (13), 4110−4129.
(17) Cornille, A.; et al. A perspective approach to sustainable routes
for non-isocyanate polyurethanes. Eur. Polym. J. 2017, 87, 535−552.
(18) Ochiai, B.; Inoue, S.; Endo, T. One-pot non-isocyanate synthesis
of polyurethanes from bisepoxide, carbon dioxide, and diamine. J.
Polym. Sci., Part A: Polym. Chem. 2005, 43 (24), 6613−6618.
(19) Diakoumakos, C. D.; Kotzev, D. L. Non-Isocyanate-Based
Polyurethanes Derived upon the Reaction of Amines with Cyclo-
carbonate Resins. Macromol. Symp. 2004, 216 (1), 37−46.
(20) Aurilien Soules, S. C., Joubert, J.-P., WO2013060950 (A1) -
Method fpr preparing a compound comprising at least one beta-
hydroxy-urethane unit and/or at least one [Upsilon]-hydroxy-urethane
unit, 2013.
(24) Ubaghs, L.; et al. Polyurethanes with Pendant Hydroxyl Groups:
Synthesis and Characterization. Macromol. Rapid Commun. 2004, 25
(3), 517−521.
(25) Prompers, G.; et al. Polyurethanes with pendant hydroxy
groups: polycondensation of 1,6-bis-O-phenoxycarbonyl-2,3[ratio]4,5-
di-O-isopropylidenegalactitol and 1,6-di-O-phenoxycarbonylgalactitol
with diamines. Green Chem. 2006, 8 (5), 467−478.
(26) Boyer, A.; et al. Solubility in CO2 and carbonation studies of
epoxidized fatty acid diesters: towards novel precursors for polyur-
ethane synthesis. Green Chem. 2010, 12 (12), 2205−2213.
(27) Rokicki, G.; Drzewicz, M.; Zachara, J.; et al. Bis(cyclic
carbonate) based on d-mannitol, d-sorbitol and di-
(trimethylolpropane) in the synthesis of non-isocyanate poly-
(carbonate-urethane)s. Eur. Polym. J. 2016, 84, 799−811.
(28) Lamarzelle, O.; et al. Activated lipidic cyclic carbonates for non-
isocyanate polyurethane synthesis. Polym. Chem. 2016, 7 (7), 1439−
1451.
(29) Besse, V.; et al. How to explain low molar masses in
PolyHydroxyUrethanes (PHUs). Eur. Polym. J. 2015, 71, 1−11.
(30) Besse, V.; et al. Synthesis of isosorbide based polyurethanes: An
isocyanate free method. React. Funct. Polym. 2013, 73 (3), 588−594.
(31) Delebecq, E.; et al. On the Versatility of Urethane/Urea Bonds:
Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane.
Chem. Rev. 2013, 113 (1), 80−118.
(32) Whelan, J. Multiple Cyclic Carbonate Polymers From Erythritol
Dicarbonate, US2935494 (A), in United States Patent Office, U.C.
Corporation, 1960.
(33) Roper, H.; Goossens, J. Erythritol, a New Raw Material for Food
̈
and Non-food Applications. Starch - Starke 1993, 45 (11), 400−405.
̈
(34) Mironczuk, A. M.; et al. Enhanced production of erythritol by
Yarrowia lipolytica on glycerol in repeated batch cultures. J. Ind.
Microbiol. Biotechnol. 2014, 41 (1), 57−64.
(35) Shindou, T.; et al. Identification of erythritol by HPLC and GC-
MS and quantitative measurement in pulps of various fruits. J. Agric.
Food Chem. 1989, 37 (6), 1474−1476.
(36) Besson, M.l.; Gallezot, P.; Pinel, C. Conversion of Biomass into
Chemicals over Metal Catalysts. Chem. Rev. 2014, 114 (3), 1827−
1870.
(37) Meyer, H. R. Dicarbonate und Dicarbamate des DL-Threits und
des Erythrits. Helv. Chim. Acta 1966, 49 (6), 1935−1937.
(38) Meyer, H. R. Butanetetrol dicarbonates and their production in
The Patent Office London, 1966, GRACE W R & CO[US].
(39) Tomczyk, K. M.; et al. Intramolecular etherification of five-
membered cyclic carbonates bearing hydroxyalkyl groups. Green Chem.
2012, 14 (6), 1749−1758.
(40) Swodenk, W. Ethanol als Rohstoff fur die chemische Industrie.
̈
Chem. Ing. Technol. 1983, 55 (9), 683−688.
(41) Lew, B. W. Process for preparing cyclic carbonates from
polyhydric alcohols. US 3,663,569, 1969.
(42) Goldstein, B. N.; et al. Investigation of cooperative kinetics on
reactions of functional groups on polymer chains. Journal of Polymer
Science Part A-2: Polymer Physics 1971, 9 (5), 769−777.
(43) Schmidt, S.; et al. Isocyanate-Free Route to Poly(carbohydrate−
urethane) Thermosets and 100% Bio-Based Coatings Derived from
Glycerol Feedstock. Macromolecules 2016, 49 (19), 7268−7276.
(44) Kihara, N.; Endo, T. Synthesis and properties of poly-
(hydroxyurethane)s. J. Polym. Sci., Part A: Polym. Chem. 1993, 31
(11), 2765−2773.
(45) Ochiai, B.; Satoh, Y.; Endo, T. Polyaddition of bifunctional
cyclic carbonate with diamine in ionic liquids: In situ ion composite
formation and simple separation of ionic liquid. J. Polym. Sci., Part A:
Polym. Chem. 2009, 47 (18), 4629−4635.
(21) Blain, M.; et al. Rational investigations in the ring opening of
cyclic carbonates by amines. Green Chem. 2014, 16 (9), 4286−4291.
H
DOI: 10.1021/acs.macromol.6b02787
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