Partially bio-based polyimides from isohexide-derived diamines

Article abstract of DOI:10.1016/j.polymer.2015.07.051

Abstract Novel partially bio-based polyimides were prepared from 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol (diaminoisosorbide, DAIS) dihydrochloride, 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydroiditol (diaminoisoidide, DAII) dihydrochloride

Full text of DOI:10.1016/j.polymer.2015.07.051

Accepted Manuscript
Partially bio-based polyimides from isohexide-derived diamines
Xiaodong Ji, Zikun Wang, Jingling Yan, Zhen Wang
PII:
S0032-3861(15)30133-6
10.1016/j.polymer.2015.07.051
JPOL 18011
DOI:
Reference:
To appear in: Polymer
Received Date: 7 April 2015
Revised Date: 19 July 2015
Accepted Date: 26 July 2015
Please cite this article as: Ji X, Wang Z, Yan J, Wang Z, Partially bio-based polyimides from isohexide-
derived diamines, Polymer (2015), doi: 10.1016/j.polymer.2015.07.051.
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ACCEPTED MANUSCRIPT
Partially bio-based polyimides from isohexide-derived
diamines
a, b
a
a
a
Xiaodong Ji, Zikun Wang, Jingling Yan,* and Zhen Wang*
a
Laboratory of Polymer Composites Engineering, Changchun Institute of Applied Chemistry,
Chinese Academy of Science, Changchun, 130022, China.
b
University of Chinese Academy of Sciences, Beijing 100049, China.
*
Corresponding author: Jingling Yan, Email: jyan@ciac.ac.cn. Phone: +86-431-85262682, Fax:
86-431-85262682.
+
Abstract
Novel partially bio-based polyimides were prepared from 2, 5-diamino-2, 5-dideoxy-1, 4: 3,
-dianhydrosorbitol (diaminoisosorbide, DAIS) dihydrochloride, 2, 5-diamino-2, 5-dideoxy-1, 4:
, 6-dianhydroiditol (diaminoisoidide, DAII) dihydrochloride, and various dianhydrides via a
6
3
conventional one-step method in m-cresol. Inherent viscosity values of these polyimides spanned a
range of 0.5-1.5 dL/g. Flexible and transparent films can be easily cast from their corresponding
solutions. The chemical structures and properties of isohexide-derived polyimides were fully
characterized by using a variety of analytical techniques. The results revealed that the thermal and
mechanical properties of isohexide-derived polyimides were similar to those derived from
petrochemical-based diamines. Moreover, these polyimides exhibited good optical transparency,
and optical activity. The good overall properties of isohexide-derived polyimides can be
contributed to the incorporation of unique isohexide moieties that were rigid, thermally stable,
fully aliphatic and chiral.
Keywords: bio-based polyimides, isohexide-derived diamines, structure-property relationship
1
. Introduction
Aromatic polyimides are a class of polymers featuring high glass transition temperatures,
high thermal stability, excellent mechanical and electrical properties, and good chemical resistance.
Thus, polyimides have been utilized for a variety of applications in the electronics, automotive,
1
-4
and aerospace industries. However, most of polyimides are prepared with petrochemical-based
monomers as the raw materials, and some of these monomers, especially aromatic diamines, are
5
-7
highly toxic or carcinogenic. Due to the foreseeable limit of fossil feedstocks and the increasing
environmental concerns, it is of great scientific and practical significance to develop polyimides
from bio-renewable raw materials. To obtain polyimides with adequate thermal resistance,
monomers with high purity and intrinsic rigidity are required. However, among the existing

ACCEPTED MANUSCRIPT
bio-based monomers only a few possessed sufficient purity (>99%) and structural rigidity for
8
-10
polyimide synthesis.
Consequently, there were only a few reports dealing with the preparation
of polyimides from bio-based dianhydrides or diamines. Recently, Kaneko and coworkers reported
the synthesis of bio-based aromatic diamines and polyimides from the photodimers of
4
-aminocinnamic acid. Moreover, they demonstrated that these polyimides showed reasonable
11
thermal and mechanical properties, high optical transparency, and good cell-compatibility.
Recently, 1,4:3,6-dianhydrohexitols (isohexides) and their derivatives have been attracting
increasing attentions as bio-based monomers for high performance polymers due to their intrinsic
rigidity, environmental friendliness, chirality, as well as biodegradability. Isohexide can be derived
from polysaccharides (such as starch) via degradation, hydrogenation, and dehydration reactions.
Depending on the positions of hydroxyl groups, isohexides are departed into three stereoisomers,
8
, 10
isosorbide (exo-endo isomer), isomannide (endo-endo isomer), and isoidide (exo-exo isomer).
Due to their desirable structural features, isohexides have been extensively investigated as
1
2-13
14-15
bio-based building blocks for a variety of polymers including polyesters,
polycarbonates,
1
6
17
18-19
20
poly (ester amide)s, poly (ester imide)s, polyurethanes,
and polyethers. The incorporation
of isohexides into polymer backbones can lead to several benefits, such as high glass transition
1
0
temperatures (T ) and special optical properties. However, isohexides show relatively lower
g
reactivity than petrochemical-based diols in polycondensation reactions since their hydroxyl
groups are secondary and sterically hindered. As a result, it is difficult to prepare
8
, 10
high-molecular-weight polymers using isohexide as the sole monomers.
Therefore, many
chemical modifications have been explored to enhance the reactivity of isohexides, including
1
0
chain extensions by nucleophilic substitution, as well as the introduction of more reactive
2
1-23
24-25
25-26
functionalities, such as amines,
primary hydroxyl groups,
carboxylic acids,
and
2
7-28
isocyanates.
Polymers with reasonably high molecular weights can be easily prepared using
these isohexide derivatives.
Among all the isohexide derivatives, dideoxy isohexide diamines are highly preferred in the
preparation of bio-based high performance polymers because their reactivity are greatly enhanced
without sacrificing structural rigidity or bio-renewable contents. Dideoxy isohexide diamines are
usually transformed from isohexides via a procedure that comprises three steps: the tosylation or
mesylation of hydroxyl groups to afford a good leaving group, the nucleophilic substitution with
1
8
29-30
23
22
azides, ammonia,
potassium phthalimide, or benzylamine, and the reduction of azides or
the deprotection of benzylamine and phthalimide. Thiem and coworkers described the preparation
of bio-based polyamides via interfacial polymerization in basic medium using isohexide-derived
3
1
diammonium salts and various acid chlorides as monomers. These polyamides showed T values
g
o
of 50-70 C, which were higher than those of benchmark polyamides, e.g. PA6 or PA66. More

ACCEPTED MANUSCRIPT
recently, a renewed interest in bio-based polymers has promoted several reports on the synthesis
and structure-property relationship of isohexide-derived polyamides. Koning and co-workers
developed a combined synthetic method for isohexide-based polyamides, which comprised a
3
2-35
conventional melt-polymerization and a solid-state postpolycondensation.
Polyamides with
number average molecular weights of above 20,000 g/mol could be easily produced by this
optimal approach. The local conformation and crystallinity of these polymers were also studied
using FT-IR, solid state NMR, and wide angle X-ray diffraction. The results demonstrated that the
incorporation of diamino-isosorbide (DAIS) and diamino-isoidide (DAII) into polyamide
backbones led to lower degree of hydrogen bonding density and therefore lower melting points of
the resulting polymers.
However, to the best of our knowledge, there was no report on the synthesis and
characterization of polyimides derived from dideoxy isohexide diamines. In this work, we
present a series of novel partially bio-based polyimides using DAIS and DAII as the diamines
monomers. These polyimides showed comparable thermal and mechanical properties to those
derived from petrochemical-based diamines. Furthermore, these polymers exhibited chiral activity
and excellent optical transparency due to the unique architecture of isohexide moieties.
2
. Experimental
2
2
.1 Materials
, 3', 3, 4'-Biphenyltetracarboxylic acid dianhydride (3, 4'-BPDA) and 2, 3', 3,
4
'-benzophenonetetracarboxylic acid dianhydride (3, 4'-BTDA) were prepared in our laboratory
3
6-37
according to the procedures in the literatures.
4, 4'-(Hexafluoroisopropylidene) diphthalic
anhydride (6FDA), 1, 2, 4, 5-cyclohexanetetracarboxylic dianhydride (HPMDA), and 4, 4'-(4,
'-isopropylidenediphenoxy) bis (phthalic anhydride) (BPADA) were purchased from Changzhou
4
Sunlight Pharmaceutical Co., Ltd. (Changzhou, China). The dianhydride monomers were purified
by sublimation in vacuum. All the other chemicals were obtained from J&K Scientific (Beijing,
China). N, N-dimethylformamide (DMF) was dried over calcium hydride and then distilled under
reduced pressure and stored over 4Å molecular sieves. All the other reagents were of analytical
grade and used as received unless specified.
2
.2 Synthesis of monomers
The synthesis of 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol (DAIS)
dihydrochloride and 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydroiditol (DAII) dihydrochloride
2
1, 33
was adapted from literature procedures based on a Gabriel route.
monomer synthesis is shown below.
A typical procedure for
Synthesis of 1, 4: 3, 6-dianhydro-2, 5-di-O-p-tosyl- -sorbitol.
D
Isosorbide (40.00 g, 0.2737 mol), p-toluenesulfonyl chloride (156.50 g, 0.8209 mol), and

ACCEPTED MANUSCRIPT
dichloromethane (600 mL) were placed into a three-necked, round-bottomed, 1 liter flask
o
equipped with a magnetic stirrer and nitrogen inlet and outlet. The mixture was stirred at 0 C for
1
4
hour under nitrogen atmosphere. Triethylamine (89.38 g, 0.8833 mol) was added dropwise over
o
o
5 minutes at 0 C with stirring. The temperature was then raised to 25 C and kept for 20 hours.
The mixture was washed completely with DI water (3×500mL), and dried over magnesium sulfate.
Dichloromethane was removed by rotary evaporation, and the crude product was recrystallized
from ethanol to afford 1, 4: 3, 6-dianhydro-2, 5-di-O-p-tosyl- -sorbitol as a pale yellow crystal.
D
o
22
o
1
Yield: 99.41 g, 80%; m.p. 104-108 C (lit. m.p. 106-108 C); purity: 97%. H NMR (400 MHz,
CDCl ) δ (ppm): 7.78 (4H, dd), 7.35 (4H, dd), 4.86 (2H, m), 4.60 (1H, t), 4.44 (1H, d), 3.87 (2H,
3
1
3
dt), 3.70 (2H, dd), 2.45 (s, 6H). C NMR (400 MHz, CDCl ) δ (ppm):145.7, 133.1, 130.3, 128.1,
3
8
4.3, 79.3, 71.7, 21.7.
Synthesis of 2,5-Diphthalimido-2,5-dideoxy-1,4:3,6-dianhydrosorbitol.
1
, 4: 3, 6-Dihydro-2, 5-di-O-p-tosyl- -sorbitol (22.84 g, 0.050 mol), toluene (100 mL) and
D
anhydrous DMF (300 mL) were placed into a three-necked, round-bottomed, 500 mL flask
equipped with a Dean-Stark trap and condenser, magnetic stirrer, and gas inlet and outlet. The
o
mixture was heated to 140 C under nitrogen atmosphere. The toluene and residual water from the
reaction solvent were removed from the system as an azeotrope by distillation. After 4 hours,
potassium phthalimide (20.50 g, 0.110 mol), and 18-crown-6 (2.642 g, 0.010 mol) were added.
o
Then the mixture was held at 140 C for 48 hours. After cooling to room temperature, the dark
brown solution was poured into DI water (800 mL). The mixture was extracted with CHCl3
(
3×400mL). The extracts were combined, washed with DI water (3×500mL), dried over
magnesium sulfate. Chloroform was removed by rotary evaporation to afford crude 2,
-diphthalimido-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol. The crude product was further purified
5
o
1
by washing with ethanol. Yield: 2.729 g, 13.5%; m.p. 238-243 C; purity: 96%. H NMR (400
MHz, CDCl ) δ (ppm): 7.86 (4H, m), 7.72 (4H, m), 5.21 (2H, d), 4.93 (2H, dd), 4.53 (1H, m), 4.26
3
1
3
(
2H, dd), 3.94 (1H, dd). C NMR (400 MHz, CDCl ) δ (ppm): 168.7, 134.3, 131.7, 123.3, 83.7,
3
6
8.1, 55.7.
Synthesis of 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol dihydrochloride
, 5-Diphthalimido-2, 5-deoxy-1, 4: 3, 6-dianhydroiditol (21.000 g, 0.052 mol), and 6M HCl
2
in acetic acid (137.5mL) were placed into a three-necked, round-bottomed, 500 mL flask equipped
o
with a mechanical stirrer and a condenser. The mixture was then heated at 140 C for 45 hours.
After cooling to room temperature, the precipitate, phthalic acid, was removed by filtration. The
filtrate was thoroughly washed with diethyl ether (3×200mL). The aqueous phase was collected
and concentrated under reduced pressure to afford a pale yellow solid. The crude product was
3
1
further purified by recrystallization from ethanol. Yield: 93594 g, 85%, m.p. 278-282 (dec) (lit.

ACCEPTED MANUSCRIPT
1
m.p.: 300 (dec.)), purity: >99%. H NMR (400 MHz, D O) δ (ppm): 5.06 (1H, t), 4.97 (1H, d),
2
1
3
4
.31 (2H, m), 4.16 (3H, m), 3.93 (1H, t). C NMR (400 MHz, D O) δ (ppm): 83.2, 70.1, 54.1.
2
Synthesis of 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydroiditol dihydrochloride
It was prepared according to the procedure for 2, 5-diamino-2, 5-dideoxy-1, 4: 3,
-dianhydrosorbitol dihydrochloride, except that isomannide was used as the starting material
6
3
1
instead of isosorbide. Yield: 66%, m.p. 287-296 (dec.) (lit. m.p. 260-280(dec.)), purity: >99%.
1
13
H NMR (400 MHz, D O) δ (ppm): 5.04 (2H, s), 4.26 (2H, dd), 4.08 (4H, d). C NMR (400 MHz,
2
D O) δ (ppm): 84.7, 70.1, 56.0.
2
2
.3 Synthesis of polyimides
All polyimides in this work were prepared via a conventional one-step method in m-cresol in
the presence of triethylamine. An equimolar amount of dianhydride and diamine monomers were
used in all cases. A representative procedure follows.
2
, 5-Diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol dihydrochloride (0.6513 g, 0.0030
mol), triethylamine (1.2142 g, 0.0120 mol), and m-cresol (17 mL) was charged into a three-necked,
round-bottomed, 50 mL flask equipped with a mechanical stirrer, and gas inlet and outlet. The
mixture was stirred at room temperature until DAIS salt completely dissolved. Then BPADA
o
(
1.5616 g, 0.0030 mol) was added in one portion. The mixture was heated at 80 C for 4 hours and
o
o
then at 190 C for 24 hours under nitrogen atmosphere. After cooling to 100 C, the viscous
solution was poured into ethanol (200mL). The fibrous precipitate was collected by filtration,
o
Soxhlet extracted with ethanol for 24 hours, and dried in vacuum at 200 C to afford polyimide
BPADA/DAIS as an off white solid (1.7916 g, 95 %).
2
.4 Film formation and characterization
A solution of polyimide in N, N-dimethylacetamide (DMAc) or m-cresol (10 wt%) was
filtrated to remove insoluble impurities, and cast onto a flat glass substrate. After the solvent was
o
o
o
removed by evaporation at 80 C for 8 hours, the film was then dried at 80 C for 2 hours, 100 C
o
o
o
for 2 hours, 150 C for 2 hours, 200 C for 2 hours, and 250 C for 4 hours in vacuum to deplete
the solvent. The dry film was removed from the substrate by immersion in hot water.
Fourier transform infrared spectroscopy (FT-IR) was performed using a Bio-Rad Digilab
1
13
Division FTS-80 spectrometer. H NMR and C NMR spectra were obtained on a Bruker-400
spectrometer. Tetramethylsilane was used as an internal standard. Tris (6, 6, 7, 7, 8,
8
-heptafluoro-2, 2-dimethyl-3, 5-cotanedinato) europium was used as a chiral chemical shift
reagent to determine the optical purities of isohexide-derived diamines. Melting points were
determined on an XT-4 melting point apparatus (Beijing Taike Apparatus, Inc.). The purities of the
synthesized compounds were determined using a Shimadzu SPD-10A liquid chromatography
equipped with a UV-Vis detector and a Hyperisl-C-18 column, using a mixture of THF and water

ACCEPTED MANUSCRIPT
(volume fraction: 7:3) (for neutral compounds) or methanol and water (volume fraction: 5:5) (for
isohexide diamines dihydrochloride) as the eluents. Inherent viscosities were measured with
o
Ubbelodhe viscometer at 30 C with a concentration of 0.5 g/dL in m-cresol. Thermal stability was
o
-1
evaluated using a Perkin-Elmer TGA 2 analysis system with a heating rate of 10 C minute under
a continuous nitrogen flow. Dynamic mechanical thermal analysis (DMTA) was conducted on a
o
-1
Q800 DMTA (TA Instruments) with a frequency of 1 Hz and a heating rate of 3 C minute from
o
room temperature to 350 C under nitrogen atmosphere. Glass transition temperature (T ) was
g
determined as the peak temperature of tan δ curve. Mechanical properties of polyimide films were
measured on an Instron material testing system (Model 5982, Instron) under a constant
-1
displacement rate of 2.0 mm minute . Five samples were tested for each film, and the averages
were reported. UV-Vis spectra were measured with a Shimadzu UV-2550 spectrometer in the
transmittance mode with a wavelength of 200-800 nm. Specific rotation was obtained on a Perkin
o
Elmer Polarimeter 341LC at 20 C under 589 nm with a sodium lamp, using
N-methyl-2-pyrrolidone (NMP) or chloroform as the solvent. Wide-angle X-ray diffraction
(WXRD) measurements were undertaken on a Rigaku max 2500V PC X-ray diffractomerer (Japan)
o
o
with Cu Kａ radiation (40kV, 200mA) at a scanning rate of 2 /min from 2 to 50 .
HO
TsO
O
2
ClH H N
O
O
O
O
O
O
N
N
O
O
NK
O
O
OH
OTs
O
O
2
NH HCl
SO
2
Cl
O
Et
3
N, CH
2
Cl
2
DMF, Toluene
O
AcOH / 6M HCl
TsO
HO
O
O
2
ClH H N
O
N
O
O
N
O
O
O
O
O
OTs
O
OH
NH2 HCl
NH2
2
H N
O
O
O
O
NH2
Diamino-isoidide
H N
2
Diamino-isosorbide
Scheme 1. Synthesis of isohexide-derived diamine dihydrochlorides.
ClH
2
H N
O
O
O
O
N
R
N
CF
3
O
O
O
n
O
O
R=
NH
2
HCl
Triethylamine
O
O
O
O
CF3
O
R
O
+
m-Cresol
ClH H
2
N
O
O
O
O
O
O
N
R
N
O
NH
2
HCl
O
O
O
n
Scheme 2. Synthesis of partially bio-based polyimides.
3
. Results and discussion
3
.1 Synthesis of isohexide-derived diamines
As depicted in Scheme 1, 2, 5-diamino-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol (DAIS)

ACCEPTED MANUSCRIPT
dihydrochloride and 2,5-diamino-2,5-deoxy-1,4:3,6-dianhydroiditol (DAII) dihydrochloride were
prepared according to a literature procedure that comprised three steps: tosylation with
p-toluenesulfonyl chloride, nucleophilic substitution using potassium phthalimide, and
2
1, 33
deprotection by refluxing in HCl/glacial acetic acid solution.
The isolated yield for tosylation
reaction was high (>80%) for both isomannide and isosorbide, and the products were readily
purified by recrystallisation from ethanol. The isolated yield of the nucleophilic substitution of 1,
4
: 3, 6-dianhydro-2, 5-di-O-p-tosyl- -mannitol was higher than 80%, while that of 1, 4: 3,
D
6
-dianhydro-2, 5-di-O-p-tosyl- -sorbitol was only around 13%. The S 2 reaction on the
D
N
exo-leaving group of isosorbide bistosylate was much less effective than that on the endo-leaving
group of isomannide bistosylate, which accounted for the low yield of 2, 5-diphthalimido-2,
3
8
5
-dideoxy-1,4:3,6-dianhydrosorbitol. The hydrolysis of bistosylate was observed, and the main
side product was phthalimido-2-deoxy-1, 4:3, 6-dianhydrosorbitol. This phenomenon was also
2
3
observed by van Es and coworkers. Subsequently, diphthalimido isosorbide and diphthalimido
isoidide were deprotected by refluxing with 6M HCl in acetic acid, which gave dideoxy-diamino
isosorbide (DAIS) and dideoxy-diamino isoidide (DAII) HCl salts with high purity and high
isolated high yield (>85%). Since the amino groups can be easily released in-situ with
triethylamine, DAII and DAIS HCl salts were directly utilized for polyimide synthesis without
further neutralization with base. The specific rotation values in chloroform for DAII and DAIS
o
o
were (+) 33 and (+) 63 , respectively. Moreover, isohexide-derived diamines did not show any
spectral nonequivalence in the presence of chemical shift reagent, which confirmed that no
racemization happened during the conversion from hydroxyl to amino groups.
3
.2 Synthesis of partially bio-based polyimides
6
FDA/DAII
6
FDA/DAIS
Asymmetric C=O
stretching
asymmetric C-O-C
stretching
Symmetric C=O
stretching
C-N stretching
3
000
2500
2000
1500 1000
-1
Wavenumber (cm )
Figure 1. FT-IR spectra of polyimides based on 6FDA and diamino isohexides

ACCEPTED MANUSCRIPT
O
O
1
3
CF3
5, 5'
O
N
N
6
7
4
CF3
2
9
n
O
O
O
2
1
+3
+3
4+7
8, 8'
6+9
5'+8
5
8'
O
O
1
CF3
5, 5'
O
N
N
6
4
CF3
2
2
3
n
O
O
O
4
1
6
5
5
'
8
7
6
5
4
Chemical shift (ppm)
1
Figure 2. H NMR spectra of polyimides based on 6FDA and diamino isohexides
Polymerization of isohexide-drived diamines and various dianhydrides was performed via a
conventional one-step method in the presence of triethylamine (Scheme 2). The selection of
dianhydride monomers is crucial to prepare polyimides with adequate molecular weights. The use
of conventional rigid dianhydrides (such as pyromellitic dianhydride (PMDA), 3, 3', 4,
4
4
'-Biphenyltetracarboxylic
acid
dianhydride
(4,
4'-BPDA),
3,
3',
4,
'-benzophenonetetracarboxylic acid dianhydride (4, 4'-BTDA), and 4, 4'-oxydiphthalic anhydride
(4, 4'-ODPA)) can lead to early precipitation during polymerization in m-cresol. Consequently,
only insoluble oligomers with low molecular weights were obtained. Table 1 lists the inherent
viscosities (η ) of the partially bio-based polyimides. All the polymers showed moderate to high
inh
-1
molecular weights, indicated by their inherent viscosity values of 0.5-1.5 dL g . For a given
dianhydride, there was no significant difference in inherent viscosity values between DAII and
DAIS-based polymers. Furthermore, flexible and free-standing films were easily cast for property
1
characterizations. Figure 1 and 2 display representative FT-IR and H NMR spectra of the
polyimides 6FDA/DAII and 6FDA/DAIS. In FT-IR spectra, the absorption bonds around 1780
-1
(asymmetric C=O stretching), 1710 (symmetric C=O stretching), and 1380 (C-N stretching) cm
were assigned to the imide groups. Moreover, no characteristic amide peak was found at about
-1
-1
3
080 cm , which indicated the completion of imidization. Meanwhile, the peaks around 1100 cm ,
which were attributed to asymmetric C-O-C stretching in ether, proved the presence of isohexide
moieties. The successful incorporation of isohexide residues into polyimide backbone was also
1
evidenced by the group signals in the H NMR spectra at 3.9-5.4 ppm (Figure 2). The proton
peaks for polyimides 6FDA/DAII and 6FDA/DAIS were fully assigned, and the signals for DAIS
or DAII residues were in good agreement with other isohexide-derive polymers including

ACCEPTED MANUSCRIPT
3
2-35
polyamides and polyesters.
Table 1. Inherent viscosity and solubility of partially bio-based polyimides
b
ηinh
Solubility in organic solvents
Polymer
-
1 a
(
dL g ) m-Cresol DMAc CHCl3 NMP DMSO 1, 4-dioxane THF
HPMDA/DAII
0.70
0.68
0.90
0.92
0.55
1.05
0.79
1.07
1.49
0.53
++
++
++
++
++
++
++
++
++
++
+
-
-
-
+
+
-
-
-
-
-
-
3
,4'-BPDA/DAII
FDA/DAII
6
+
+-
-
++
++
-
++
++
+
-
++
-
++
-
BPADA/DAII
-
3
,4'-BTDA/DAII
+-
+-
-
-
-
HPMDA/DAIS
,4'-BPDA/DAIS
FDA/DAIS
+-
-
-
++
+-
++
+
-
-
3
+-
++
++
-
-
-
6
+
+-
-
-
+-
+
-
-
BPADA/DAIS
-
-
3
,4'-BTDA/DAIS
+-
+-
-
a
-1
o
:
Determined at a concentration of 0.5g dL in m-cresol at 30 C.
b
:
Key: ++: soluble at room temperature; +: soluble upon heating; +-: partially soluble upon
heating; -: insoluble. Solvents: DMAc: N, N-dimethylacetamide; CHCl : chloroform; NMP:
3
N-methyl-2-pyrrolidone; DMSO: dimethyl sulfoxide; THF: tetrahydrofuran.
3
3
.3 Properties of partially bio-based polyimides
.3.1 Solubility and bio-based content
The solubility of isohexide-derived polyimides is shown in Table 1. Most of the polyimides
were soluble in m-cresol and NMP but insoluble in THF, DMSO, and 1, 4-dioxane. Polyimides
derived from 6FDA and BPADA showed the highest solubility in organic solvents among all the
polymers. This phenomenon was also observed by other polyimides from 6FDA and BPADA,
1
, 3-4
which is contributed to the introduction of bulky –C(CF ) – or flexible bisphenol A segments.
3
2
For a given dianhydride, polyimides from DAII showed similar solubility behavior to those from
DAIS.
According to US Department of Agriculture, the bio-based content of a product was defined as
the percentage of bio-based carbons in the total organic carbons of the product. The bio-based
3
9
content of the polyimides in this study can be estimated from this definition. Isohexide-derived
diamines, DAII or DAIS, were made of bio-renewable raw materials-starch, while the

ACCEPTED MANUSCRIPT
dianhydrides were petrochemical-based monomers. Thus, the bio-based contents of DAII and
DAIS were 100%, whereas those of the dianhydrides were 0%. As listed in Table 2, the bio-based
contents of isohexide-based polyimides ranged from 16.2 to 37.5%, which meet or are close to the
minimum requirement for bio-based products (25%).
3
.3.2 Thermal properties
Table 2. Bio-based contents, thermal and mechanical properties of partially bio-based polyimides
Bio-based
Tensile Strength
(MPa)
Elongation
o
a
o
b
Polymer
T ( C)
T5% ( C)
Modulus (GPa)
g
content (%)
at break (%)
HPMDA/DAII
37.5
27.3
24.0
16.2
26.1
37.5
27.3
24.0
16.2
26.1
322
318
292
219
300
320
313
291
214
288
397
448
457
459
428
378
452
457
462
420
103
113
114
103
101
90
3.4
3.1
3.3
2.5
3.6
3.6
3.2
3.6
2.8
3.4
63.2
6.3
3
,4'-BPDA/DAII
FDA/DAII
6
9.1
BPADA/DAII
10.2
4.0
3
,4'-BTDA/DAII
HPMDA/DAIS
,4'-BPDA/DAIS
FDA/DAIS
73.1
9.3
3
126
132
104
6
11.3
12.7
4.4
BPADA/DAIS
3
,4'-BTDA/DAIS
99
a
o
-1
:
Glass transition temperature determined by DMTA at heating rate of 30 C min at 1 Hz.
b
o
-1
:
5% Weight loss temperature measured by TGA in nitrogen at a heating rate of 20 C min
a)
HPMDA/DAIS
,4-BPDA/DAIS
3
1
1
1
E9
E8
E7
1
0
0
3
,4'-BTDA/DAIS
BPADA/DAIS
.1
6FDA/DAIS
.01
5
0
100
150
200
250
300
o
Temperature ( C)

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b)
HPMDA/DAII
,4'BPDA/DAII
3
1
0
0
1
1
1
E9
E8
E7
BPADA/DAII
6
FDA/DAII
.1
3
,4'-BTDA/DAII
.01
1
00
150
200
250
300
o
Temperature ( C)
Figure 3. DMTA curves of isohexide-derived polyimides (a: DAIS-based polyimides, b:
DAII-based polyimides)
The glass transition temperatures (T s) of isohexide-derived polyimides were characterized via
g
dynamic mechanical thermal analyses (DMTA), and the results are summarized in Table 2. Figure
3
displays the temperature dependence of storage modulus and tan δ for partially bio-based
polyimides. Glass transition temperature (Tg) was regarded as the peak temperature of tan δ
o
curves. The T values of partially bio-based polyimides ranged from 214 to 322 C, which were
g
comparable to the T values of their counterparts derived from petroleum-based diamines, such as
g
1
, 3-4
m-phenylenediamine (m-PDA) and 4, 4-oxydianiline (4, 4-ODA).
The storage modulus values
of these polymers decreased sharply above T , which is typical for thermoplastic polymers. For a
g
given diamine, the T values of partially bio-based polyimides were in the order of HPMDA>3,
g
4
'-BPDA>3, 4'-BTDA≈6FDA>BPADA. The T s of linear polymers were predominated by chain
g
rigidity, rotational barrier for conformation change, and intermolecular interactions. There was no
flexible linkage or freely rotatable single bond in the dianhydride residue of HPMDA-based
polyimides. As a consequence, HPMDA-based polyimides possessed the highest T values for a
g
given diamines. In contrast, there were three flexible linkage (ether and isopropyl groups) in the
dianhydride residue of BPADA-based polyimides, which led to their lowest T values stemmed
g
from the increased free volume. Meanwhile, for a given dianhydride, DAII-based polyimides
possessed higher T values than DAIS-based ones, except for 6FDA-based polymers. According to
g
the conformational information reported by Koning et al, the majority of DAII moiety in polymer
backbone adopts a ‘boat’ conformation. On the contrary, the most abundant conformer for DAIS
moiety has a twisted ‘chair’ conformation due to its asymmetric and sterically hindered
3
2-35
structure.
The highly distorted, exo-endo oriented DAIS residue decreased chain linearity and

ACCEPTED MANUSCRIPT
prevented the formation of intermolecular charge-transfer complexes, which accounted for the
relatively lower T values of DAIS-based polymers in comparison with DAII-based ones.
g
6
FDA-based polyimides showed very close T values because the chain packing was already very
g
loose due to the bulky –C(CF ) – groups regardless of diamine structures.
3
2
The thermal stability of isohexide-derived polyimides was assessed using thermogravimetric
analyses (TGA), and the temperatures of 5% weight loss (T5%) of these polyimides are listed in
Table 2. The T5% values of partially bio-based polyimides in this study spanned a range of 378-462
o
C, which indicated that the incorporation of bio-renewable isohexide moieties into polyimide
backbone was not noticeably detrimental to the thermal stability of the resulting polymers. As
shown in Figure 4, T5% values of partially bio-based polyimides showed strong dependence on the
structures of the dianhydrides and the molecular weights. Polyimides from HPMDA exhibited the
lowest T5% values due to their fully aliphatic architectures, which are more susceptible to chain
scission at elevated temperature. 3, 4'-BTDA-based polyimides displayed inferior thermal stability
to other semi-aromatic polymers because of their relatively low molecular weights indicated by
their lower inherent viscosities. In general, DAII-based polyimides showed similar thermal
degradation behavior to DAIS-based ones for a given dianhydride.
3
.3.3 Mechanical properties
The mechanical properties of isohexide-derived polyimides were characterized by tensile
testing, and the results are summarized in Table 2. The tensile strength, modulus, and elongation at
break of these polyimide films were in the range of 90-132 MPa, 2.5-3.6 GPa, and 4.0-73.1%,
respectively. In general, the tensile properties of these polyimides are related to their chemical
compositions and molecular weights. Fully aliphatic polyimides from HMPDA showed much
higher elongation at break (>60%). For polyimides derived from aromatic dianhydrides, the
phthalimide segment is linear and coplanar. On the contrary, the diimide segment in
HMPDA-based polyimides is non-linear and non-coplanar, and showed a distorted
4
0
conformation. Consequently, HPMDA-based polyimide chains were more prone to unfolding
than aromatic dianhydride-based ones during stretching test, which accounted for their highest
elongation at break. Polyimides based on BPADA possessed the highest elongation at break and
lowest tensile modulus among all the semi-aromatic polyimides, which could be contributed to
their lowest imide content and the abundance of flexible linkages (ether and isopropyl). Polymers
from 3, 4'-BTDA displayed the lowest elongation at break owing to their lowest molecular
weights.
3
.3.4 Optical properties
The images of representative isohexide-derived polyimides are shown in Figure 4. All the
polyimide films were colorless or pale yellow, while the reference film (polyimide from 4,

ACCEPTED MANUSCRIPT
4
'-BPDA and p-phenylenediamine) was dark-brown. The UV-Vis spectra of 20-30 ꢀm thick
isohexide-derived polyimide films are illustrated in Figure 5. The cutoff wavelength values (λ0)
for these polyimides were in the range of 265-368 nm. Except polyimide 3, 4-BTDA/DAIS,
isohexide-derived polyimides possessed a transmittance at 450 nm (T450) of higher than 70%. The
color reduction and high optical transparency of isohexide-derived polyimides stemmed from the
unique structure of isohexide moieties. The absorption in the UV-Vis region for conventional
polyimides is due to the presence of inter- and intra-molecular charge transfer interactions and
4
1
electron conjugation. However, the formation of intra-molecular charge transfer complexes and
electron conjugation was suppressed by aliphatic isohexide moieties since the electron donating
properties of aliphatic diamines residues were relatively weak. In addition, the highly twisted,
sterically-hindered architecture of DAII and DAIS further decreased the inter-molecular charge
transfer interactions.
Table 3. Optical properties of isohexide-derived polyimides
Specific
b
c
Polymer
λ0 (nm)
T450 (%)
o
a
rotation ( )
HPMDA/DAII
(+)93
(+)143
(+)29
265
366
325
368
352
285
364
329
365
358
79
82
87
83
76
75
71
82
82
57
3
,4'-BPDA/DAII
FDA/DAII
6
BPADA/DAII
(+)56
3
,4'-BTDA/DAII
(+)79
HPMDA/DAIS
,4'-BPDA/DAIS
FDA/DAIS
(+)154
(+)164
(+)96
3
6
BPADA/DAIS
(+)136
(+)141
(+)147
(+)132
3
,4'-BTDA/DAIS
e
DPIS
f
DPII
a
o
:
Measure at 20 C in NMP with a concentration of 0.10 g/dL.
The wavelength with a transmittance of <1%.
Transmittance at 450 nm.
b
c
:
:
d
:
:
2,5-Diphthalimido-2,5-dideoxy-1,4:3,6-dianhydrosorbitol.
2,5-Diphthalimido-2,5-dideoxy-1,4:3,6-dianhydroiditol.
e

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For a given diamines, polyimides from HPMDA showed the lowest λ values because of their
0
fully aliphatic structures. Polyimides from 3, 4'-BTDA exhibited the lowest transparency due to
the side reactions associated with benzophenone segment, such as photo-crosslinking and the
4
1
formation of imino groups. Meanwhile, polyimides from 6FDA exhibited the highest
transmittance values at 350-800 nm owing to the bulky –C(CF ) – residue which further loosened
3
2
4
0
the chain packing. For a given dianhydride, the transmittance values of DAII-based polyimides
were higher than those of DAIS-based polymers.
The specific rotations of partially bio-based polyimides were measured in NMP at a
o
concentration of 0.10 g/dL at 20 C, and the results were listed in Table 3. The specific rotation
values showed strong dependence on the structure of dianhydrides and diamines. DAII-based
polyimides possessed lower specific rotation values than the corresponding DAIS based one,
which agreed with the order of the specific rotation values for their model compound, 2,
5-diphthalimido-2, 5-dideoxy-1, 4: 3, 6-dianhydrosorbitol and 2, 5-diphthalimido-2, 5-dideoxy-1,
4: 3, 6-dianhydroiditol. Generally, polyimides from rigid dianhydrides (3,4'-BPDA, HPMDA, and
3,4'-BTDA) showed higher specific rotation values than those from flexible dianhydrides (6FDA,
BPADA) for a given diamine.
.3.5 Wide-angle X-ray diffraction
3
The crystallinity of isohexide-derived polyimides was examined by wide angle X-ray
o
diffraction. All of the polymers exhibited broad peaks centered at 15-22 , which indicated that
these polymers are amorphous (Figure S3).
4
. Conclusion
In this study, a series of novel partially bio-based polyimides were successfully synthesized
from two isohexide-derived diamine dihydrochloride salts and various dianhydrides via a
conventional one-step method in the presence of triethylamine. Since isohexide moieties are
intrinsically rigid and thermally stable, the thermal and mechanical properties of these partially
bio-based polyimides were comparable to their counterparts from petrochemical-based diamines.
Furthermore, isohexide-derived polyimides exhibited excellent optical transparency, which can be
attributed to the decreasing inter- and intra-molecular interactions stemmed from the aliphatic and
highly twisted isohexide moieties. Moreover, isohexide-derived polyimides also showed optical
o
activity, with specific rotation values ranging from 29 to 164 . For a given dianhydride,
DAII-based polymers showed higher glass transition temperatures and transmittance but lower
specific rotation values than DAIS-based ones, whereas their solubility, thermal stability, and
mechanical properties were similar. Due to a good combination of impressive overall properties
and reasonable bio-based contents, these polyimides showed great potential in the applications of
solar cell and liquid crystal alignment, replacing polyimides from petroleum-based diamines. This

ACCEPTED MANUSCRIPT
study provided new insights into how to design and prepare high performance polymers from
bio-renewable feestocks.
A
B
C
D
E
Figure 4. Images of representative isohexide-derived polyimides (A: BPADA/DAII, B:
FDA/DAII, C: BPADA/DAIS, D: 6FDA/DAIS, E: reference (BPDA/PDA))
6
100
a)
8
6
4
2
0
0
0
0
0
HPMDA/DAIS
6
3
FDA/DAIS
,4'-BPDA/DAIS
BPADA/DAIS
,4'-BTDA/DAIS
3
3
00
400
500
600
700
800
Wavelength (nm)
100
b)
8
6
4
2
0
0
0
0
0
HPMDA/DAII
3
6
,4'-BPDA/DAII
FDA/DAII
BPADA/DAII
,4'-BTDA-DAII
3
3
00
400
500
600
700
800
Wavelength (nm)
Figure 5. UV-Vis spectra of isohexide-derived polyimides (film thickness: 20-30 ꢀm, a:
DAIS-based polyimides, b: DAII-based polyimides)

ACCEPTED MANUSCRIPT
Acknowledgement
The authors express their thanks to the National Science Foundation of China (No. 51173178,
1304093, and 51473157) for their financial supports.
References
2
1
2
3
4
5
. Sroog CE. Prog Ploym Sci 1991; 16: 561-694.
. Wilson D, Stenzewberger HD, Hergenrother PM. Polyimides. Glasgow: Blackie, 1990: p58-77.
. Abajo JH, Campa JG. Adv Polym Sci 1999; 140: 23-59.
. Ding M. Prog Ploym Sci 1991; 32: 653-668.
. Martin ER, Timothy EL, editors. Synthetic Methods in Step-Growth Polymers. John Wiley &
Son, 2003: p265-326.
6
2
7
. Imai Y, Yokota R. Saishin Polyimide, Kiso to Ouyou. HE FF, WU ZW, Trans. Trans. NTS Inc.,
002: p182-193.
. Pohanish RP. Sitting’s Handbook of Toxic and Hazardous Chemicals and Carcinogens (6 ed.),
Elsevier Science Publisher, 2012: p873-875.
. Belgacem MN, Gandini, A. Monomers, Polymers and Coposites from Renewable Resources,
Elsevier Science Publisher, 2008: p 89-114.
8
9
1
5
. Raquez JM, Deleglise M, Lacrampe MF, Krawczak P. Prog Polym Sci 2010; 35: 487-509.
0. Fenouillot F, Rousseau A, Colomines G, Saint-Loup R, Pascault JP, Prog Polym Sci 2010; 35:
78-622.
11. Suvannasara P, Tateyama S, Miyasato A, Matsumura K, Shimoda T, Ito T, Yamagata Y, Fujita
T, Takaya N, and Kaneko T. Macromolecules 2014; 47: 1586-1593.
1
1
1
5
1
1
1
1
1
2. Yoon WJ, Oh KS, Koo JM, Kim JR, Lee KJ, Im SS. Macromolecules 2013; 46: 2930-2940.
3. Kricheldorf HR, Weidner SM. Macromol Chem Phys 2013; 214: 726-733.
4. Li Q, Zhu W, Li C, Guan G, Zhang D, Xiao Y, and Zheng L. J Polym Sci Polym Chem 2013;
1: 1387-1397.
5. Lee CH, Takagi H, Okamoto H, and Kato M. J Appl Polym Sci 2013; 127: 530-534.
6. Philip B, Sreekumar K. Polym Int 2001; 50: 1318-1323.
7. Kricheldorf HR, Gomourachvili Z. Macromol Chem Phys 1997; 198: 3149-3160.
8. Thiem J. Makromol Chem 1986; 187: 2775-2785.
9. Besse V, Auvergne R, Carlotti S, Boutevin G, Otazaghine B, Caillol S, Pascault JP, Boutevin B.

ACCEPTED MANUSCRIPT
React Funct Polym 2013; 73: 588-594.
2
2
2
2
2
6
2
2
0. Kricheldorf HR, Almasri M. J Polym Sci Polym Chem 1995; 33: 2667-2671.
1. Montgomery R, Wiggins LF. J Chem Soc 1946; APR: 393-396.
2. Thiyagarajan S, Gootjes L, Vogelzang W, van Haveren J, Lutz M, van Es DS. ChemSusChem
011; 4: 1823-1829.
3. Thiyagarajan S, Gootjes L, Vogelzang W, Wu J, van Haveren J, van Es DS. Tetrahedron 2011;
7: 383-389.
4. Hayes R, Brandenburg C. US Patent 2003; 6,608,167.
5. Wu J, Eduard P, Thiyagarajan S, Van Haveren J, Van Es DS, Koning CE, Luts M, Guerra CF.
ChemSusChem 2011; 4: 599-603.
2
2
2
2
2
2
3
6. Caouthar AA, Roger P, Tessier M, Chatti S, Blais JC, Bortolussi M. Eur Polym J 2007; 43:
20-230.
7. Bachmann F, Reimer J, Ruppenstein M, Thiem J. Macromol Rapid Commun 1998; 19:
1-26.
8. Zenner MD, Xia Y, Chen JS, Kessler MR. ChemSusChem 2013; 6: 1182-1185.
9. Pingen D, Diebolt O, Vogt D. CHEMCATCHEM 2013; 5: 2905-2912.
0. Imm S, Bahn S, Zhang M, Neubert L, Neumann H, Klasovsky F, Pfeffer J, Haas T, Beller M.
Angew Chem Int Ed 2011; 50: 7599-7603.
3
3
1. Thiem J, Bechmann F. Makromol. Chem 1991; 192: 2163-2182.
2. Wu J, Jasinska-Walc L, Dudenko D, Rozanski A, Hansen MR, van Es D, Koning CE.
Macromolecules 2012; 45: 9333-9346.
3
4
3
3. Jasinska L, Villani M, Wu J, van Es D, Klop E, Rastogi S, Koning CE. Macromolecules 2011;
4: 3458-3466.
4. Jasinska-Walc L, Villani M, Dudenko D, van Asselen O, Klop E, Rastogi S, Hansen MR,
Koning CE. Macromolecules 2012; 45: 2796-2808.
5. Jasinska-Walc L, Dudenko D, Rozanski A, Thiyagarajan S, Sowinski P, van Es D, Shu J,
Hansen MR, Koning CE. Macromolecules 2012; 45: 5653-5666.
3
3
3
3
6. Ding M, Wang Z, Yang Z, Zhang J. US Patent 1992; 5,081,281.
7. Fang X, Wang Z, Yang Z, Gao L, Li Q, Ding M. Polymer 2003; 44: 2641-2646.
8. Stoss P, Hemmer R. Adv Carbohydr Chem Biochem 1991; 49: 93-173.

ACCEPTED MANUSCRIPT
3
4
2
4
9. Norton GA, Devlin SL. Bioresour Technol 2006; 97: 2084-2090.
0. Hesegawa M, Fujii M, Ishii J, Yamaguchi S, Takezawa E, Kagayama T, Ishikawa A. Polymer
014; 55: 4693-4708.
1. Hasegawa M, Horie K. Prog Ploym Sci 2001; 26: 259-335.
Graphic abstract
O
N
O
CF3
CF3
O
N
n
O
O
O

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Supporting information
Partially bio-based polyimides from isohexide-derived
diamines
a, b
a
a
a
Xiaodong Ji, Zikun Wang, Jingling Yan,* and Zhen Wang*
a
Laboratory of Polymer Composites Engineering, Changchun Institute of Applied Chemistry,
Chinese Academy of Science, Changchun, 130022, China.
b
University of Chinese Academy of Sciences, Beijing 100049, China.
*
Corresponding author: Jingling Yan, Email: jyan@ciac.ac.cn. Phone: +86-431-85262682, Fax:
86-431-85262682.
+
Content
1
Figure S1. H NMR spectra of pure diamino-isoidide and diamino-isoidide whith chiral chemical
shift reagent (A: pure diamino-isoidide, B: diamino-isoidide whith chiral chemical shift reagent)
Figure S2. TGA traces of isohexide-derived polyimides (a: DAIS-based polyimides, b:
DAII-based polyimides)
Figure S3. WXRD diagrams of isohexide-derived polyimides (a: DAIS-based polyimides, b:
DAII-based polyimides)

ACCEPTED MANUSCRIPT
B
A
9
8
7
6
5
4
3
2
1
Chemical shift (ppm)
1
Figure S1. H NMR spectra of pure diamino-isoidide and diamino-isoidide whith chiral chemical
shift reagent (A: pure diamino-isoidide, B: diamino-isoidide whith chiral chemical shift reagent)
100
a)
8
6
4
2
0
0
0
0
0
6
FDA/DAIS
BPADA/DAIS
,4'-BPDA/DAIS
HPMDA/DAIS
3
3,4'-BTDA/DAIS
1
00
200
300
400
500
600
o
Temperature ( C)

ACCEPTED MANUSCRIPT
100
b)
8
6
4
2
0
0
0
0
0
6
FDA/DAII
HPMDA/DAII
3
BPADA/DAII
3
,4'-BPDA/DAII
,4'-BTDA/DAII
200
1
00
300
400
500
600
o
Temperature ( C)
Figure S2. TGA traces of isohexide-derived polyimides (a: DAIS-based polyimides, b:
DAII-based polyimides)
3
,4'-BPDA/DAIS
a)
BPADA/DAIS
6FDA/DAIS
3,4'-BTDA/DAIS
HPMDA/DAIS
10
20
30
40
o
( )
2
θ

ACCEPTED MANUSCRIPT
b)
HPMDA/DAII
BPADA/DAII
6
3
3
FDA/DAII
,4'-BPDA/DAII
,4'-BTDA/DAII
10
20
o
( )
30
40
2
θ
Figure S3. WXRD diagrams of isohexide-derived polyimides (a: DAIS-based polyimides, b:
DAII-based polyimides)

ACCEPTED MANUSCRIPT
Highlights
1
2
3
4
. Partially bio-based polyimides were prepared using isohexide-derived diamines.
. The properties of the polymer were characterized using various analytical techniques.
. Isohexide-derived polyimides showed good thermal and mechanical properties.
. These polyimides exhibited good optical transparency, and optical activity.