Hydrotalcites catalyze the acidolysis polymerization of phenolic acid to create highly heat-resistant bioplastics

Article abstract of DOI:10.1002/adfm.201200427

Acidolysis polymerization has been used to prepare phenol-derived polymers such as liquid crystalline (LC) polymers, and is catalyzed by mildly-alkaline salts. The catalytic effects of hydrotalcites (HTs), which are natural alkalescent minerals with controllable basicity, are investigated on the acidolysis copolymerization of coumarates such as p-coumaric acid and caffeic acid. As a result, the LC copolymer prepared in the presence of HT with a Mg/Al ratio of 3 shows higher molecular weight values than copolymers prepared in the presence of any other alkalescent salts. On the other hand, the copolymers prepared in the presence of HTs show a clear LC state where the polymer chains are oriented on the surface of the glass fibers. The resin, which is oriented by glass fiber fillers aligning along its longitudinal axis and is annealed at 300 °C for 20 min, shows a softening temperature of 305 °C while keeping a high mechanical strength of 85 MPa and a high mechanical modulus over 1 GPa. Hydrotalcites efficiently catalyze acidolysis copolymerizations of bioavailable coumarates such as acetylated p-coumaric acid and caffeic acid to prepare liquid crystalline polymers exhibiting a clear orientation state on the surface of the glass fibers (GF). The GF-reinforced resins show an extremely high softening temperature of 305 °C while keeping a high mechanical strength of 85 MPa and modulus over 1 GPa. Copyright

Full text of DOI:10.1002/adfm.201200427

www.afm-journal.de
www.MaterialsViews.com
Hydrotalcites Catalyze the Acidolysis Polymerization of
Phenolic Acid to Create Highly Heat-Resistant Bioplastics
Manu Chauzar, Seiji Tateyama, Takanori Ishikura, Keitaro Matsumoto, Daisaku Kaneko,
Kohki Ebitani, and Tatsuo Kaneko*
generally used after acetylation, followed
by acidolysis polycondensation to create
aromatic polyesters. We have previously
developed highly heat-resistant polyesters
using acetylated phenolic acids such as
p-coumaric acid (4-hydroxycinnamic acid;
4HCA) and caffeic acid (3,4-dihydroxycin-
namic acid; DHCA); the poly(4HCA-co-
DHCA) with a copolymer composition of
4HCA/DHCA =60/40 mol/mol showed
a glass transition temperature of 156 °C,
which is high enough for use as a
bio-based engineering plastic[5]. In order
to increase the heat-resistance perfor-
Acidolysis polymerization has been used to prepare phenol-derived polymers
such as liquid crystalline (LC) polymers, and is catalyzed by mildly-alkaline
salts. The catalytic effects of hydrotalcites (HTs), which are natural alkalescent
minerals with controllable basicity, are investigated on the acidolysis copoly-
merization of coumarates such as p-coumaric acid and caffeic acid. As a result,
the LC copolymer prepared in the presence of HT with a Mg/Al ratio of
3 shows higher molecular weight values than copolymers prepared in the
presence of any other alkalescent salts. On the other hand, the copolymers pre-
pared in the presence of HTs show a clear LC state where the polymer chains
are oriented on the surface of the glass fibers. The resin, which is oriented by
glass fiber fillers aligning along its longitudinal axis and is annealed at 300 °C
for 20 min, shows a softening temperature of 305 °C while keeping a high
mechanical strength of 85 MPa and a high mechanical modulus over 1 GPa.
mance to achieve usage as
a super-
engineering plastic, the development of an
efficient and facile method for hybridiza-
tion with mechanical reinforcing fillers is
required.
1. Introduction
The acidolysis reaction is catalyzed by mildly-alkaline com-
pounds such as sodium acetate and sodium phosphate[6].
Stronger alkaline catalysts can also promote the acidolysis
reaction, but the reverse hydrolysis reaction of the generated
polyesters can occur easily. Thus, the development of an appro-
priate catalyst that can promote the acidolysis chain-propagation
without inducing the reverse reaction is required. The alka-
lescent natural mineral hydrotalcite (HT; [Mg6Al2(OH)16]
(CO3)4H2O) belongs to the layered-double-hydroxides family
as schematically-illustrated in Figure 1a [7]. HT has a structure
isomorphous to that of brucite, Mg(OH)2, in which magnesium
cations (Mg2+) occupy the centers of hydroxide octahedra. These
octahedra form a continuous two-dimensional sheet by sharing
edges. It has been reported that HT can be used as a hetero-
geneous catalyst for acetylation using acetic anhydride[7]. The
hydroxide groups of HT are important for their catalytic activi-
ties, which are proportional to the number and basicity of the
interlayer anions. HT derivatives were also reported to be safer,
cheaper, and more efficient catalysts than conventional catalysts
for poly(alkylene terephthalate) production by the catalysis of
the transesterification[8] reaction, which is an intrinsically sim-
ilar reaction to acidolysis. Furthermore, the structural control
of HT is possible; aluminum cations (Al3+) can replace some
of the magnesium cations (Mg2+), thus inducing a net positive
charge in the cationic sheet, which is counterbalanced by inter-
layer anions such as carbonate and nitrate anions.
Bio-based plastics originating from biochemicals, which are
produced as metabolites from plant carbon-fixation by photo-
synthetic activity or are derived from these metabolites by the
following reactions, are significant for the establishment of a
sustainable society through the carbon-stock inside of their
plastics. However, conventional bio-based plastics are generally
composed of aliphatic polyesters whose applications have been
limited due to their poor thermal and mechanical properties[1].
On the other hand, the introduction of an aromatic component
into the polymer backbone is an efficient method to intrinsi-
cally improve material performance, since aromatic polyesters
such as liquid crystalline (LC) polymers have been used in
the engineering of plastics[2]. Most aromatic biochemicals are
phenolic compounds obtained by the sikimate biosynthetic
pathway[3], and are widely available in various environments.[4]
Phenolic compounds are used as building blocks of LC poly-
mers (LCP), but are very easily oxidized. Therefore, they are
M. Chauzar, Dr. S. Tateyama, T. Ishikura, K. Matsumoto,
Prof. D. Kaneko, Prof. K. Ebitani, Prof. T. Kaneko
School of Materials Science
Japan Advanced Institute of Science and Technology
(JAIST)1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
E-mail: kaneko@jaist.ac.jp
In this study, we investigate the effects of HT as a catalyst on
the acidolysis polymerization of acetylated phenolic compounds.
DOI: 10.1002/adfm.201200427
©
wileyonlinelibrary.com
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1

www.afm-journal.de
www.MaterialsViews.com
003
a
b
006
Mg/Al: 1/1
OH
Mg, Al
OH
Mg/Al: 2/1
-
NO3
Mg/Al: 3/1
Mg/Al: 4/1
Mg/Al: 5/1
Calcinated
(Mg/Al: 3/1)
0 10 20 30 40 50 60 70 80
Diffraction angle, 2 (deg)
Figure 1. a) Schematic illustrate of representative hydrotalcite structure. b)X-ray diffraction patterns of HT with various Mg/Al ratios.
peak at 1728 cm−1 indicates the formation of ester bonds from
4HCA and DHCA, and there was also an IR shoulder around
1765 cm−1 which could be assigned to the vibration of acetyl
groups. In addition, the IR peaks of carboxylic acid detected
at 1667 and 1642 cm−1 in the spectra of the monomers disap-
peared in the copolymer spectrogram. These findings support
copolymer formation by the acidolysis of acetylated monomers.
As a result, we find that HT of a specific composition can be
an excellent catalyst to promote the preparation of poly(4HCA-
co-DHCA) LCP. Consequently, we develop a high-performance
resin with a heat-resistance temperature over 300 °C, which is
sufficient for use as a bio-based super-engineering plastic.
1
The copolymers were also characterized by H-NMR spectros-
2. Results and Discussion
copy (Figure S2), and proton signals appeared at δ = 2.20−
2.43 ppm (acetyl, -CH3), δ = 6.60−6.82 ppm (α-CH), δ = 7.13−
7.82 ppm (aromatic protons), and δ = 7.82−8.18 ppm (β-CH).
The detailed assignment of the aromatic protons is shown in
the chemical structure. The aromatic protons marked a′ and a″
which are adjacent to the O-substituted carbons of the monomers
showed multiple signals, suggesting the coexistence of various
ester environments such as a coumaryloyl ester, and 3-O- and/or
4-O-acetyloyl esters unreacted due to steric hindrance.
Various alkalescent catalysts such as NaOAc, Na2CO3,
NaH2PO4, Na2HPO4 and HT were used in the copolymeri-
zation of 4HCA with DHCA. The molecular weights meas-
ured by GPC were summarized in Table 1. The copolymers
prepared in the presence of HT catalysts showed narrower
Mw/Mn values than those in the other catalysts. As shown in
the upper chromatogram of Figure S3, the copolymers prepared
with the HT catalyst showed only one structureless monomodal
2.1. Polymer syntheses using various catalysts
The copolymer poly(4HCA-co-DHCA) with a 4HCA feed-com-
position of 60 mol% was prepared in the presence of various
alkalescent catalysts (Scheme 1). The reaction mixture was
treated by acetic anhydride at 150 °C, and was polymerized for
200 °C in vacuo. The excess acetic anhydride was evaporated
during polymerization, and gradually increased its viscosity to
finally solidify and not allow further agitation. If the reaction
speed was high, the polymerization period until solidification
became shorter. In particular, polymerization in the presence
of HT as a catalyst took 4 hours less than in the other catalysts
(6 h).
Figure S1 shows a representative infrared (IR) spectrogram of
poly(4HCA-co- DHCA)s prepared in the presence of HT. The IR
©
2
wileyonlinelibrary.com
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427

www.afm-journal.de
www.MaterialsViews.com
Scheme 1. Syntheses of poly(4HCA-co-DHCA)s from acetylated monomers via acidolysis.
T a b le 1 . Molecular weights of poly(4HCA-co-DHCA) prepared in the
2.2. Polymer Syntheses Using HT
presence of hydrotalcite with different weight contentsa).
The copolymers were prepared with HT at a content of 0.6 wt%
for different polymerization periods (Table 2). The molecular
weight of the copolymers increased with an increase in the
polymerization period, but the molecular weight distribution
also increased. Finally, the polymerization liquid was solidi-
fied by 240 min. agitation to restrict any further reaction as
mentioned above. These results indicate that the inhomoge-
neous catalyst HT efficiently catalyzed the acidolysis reaction
of coumarate carboxylic acid with the acetylated phenol ends
of the hyperbranched polymers, even in a melt polymerization
Catalysts
Feed ratio to
monomers (wt%)
Mw
Mn
Mw/Mn
0.2
0.4
0.6
0.8
1.0
24,900
70,800
82,300
54,800
25,200
126,000
50,500
64,600
48,000
14,400
51,000
68,600
21,100
12,400
24,100
8,400
1.7
1.4
1.2
2.6
2.4
5.2
6.0
6.6
7.2
HT
CH3COONa
Na2CO3
1.0
NaH2PO4
Na2HPO4
9,800
T a b le 2 . Molecular weights of poly(4HCA-co-DHCA)s prepared in the
6,700
presence of HT for different polymerization periodsa).
a)Polymerization was carried out for 2 hrs at 150 °C and for 4 hrs at 200 °C. Molec-
ular weights were estimated by gel permeation chromatography (GPC, eluent
DMF) in a polystyrene standard.
Polymerization
period (min)
Mw
Mn
Mw/Mn
30
16,300
28,700
26,800
36,900
34,000
54,800
11,500
16,500
18,000
19,600
19,900
21,100
1.4
1.7
1.5
1.9
1.7
2.6
peak. On the other hand, the copolymers prepared in the pres-
ence of CH3COONa, Na2CO3, NaH2PO4, and Na2HPO4 showed
multimodal GPC peaks as shown in the representative chro-
matogram in the lower panel of Figure S3. Besides the Mn of
the copolymer prepared in the presence of Na2CO3, NaH2PO4,
and Na2HPO4 showed low values. These results indicated the
presence of various side reactions during the polymerization.
Regarding the feed ratio of the monomer to the catalysts, the
copolymer in HT at ratios of 0.4 and 0.6 showed high values
and narrow molecular weight distributions.
90
120
180
210
240
a)Polymerization was carried out for 2 hrs at 150 °C and for various periods at
200 °C in the presence of HT with a content of 0.8 wt% to monomers. Molecular
weights were estimated by gel permeation chromatography (GPC, eluent DMF) in
a polystyrene standard.
©
wileyonlinelibrary.com
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
3

www.afm-journal.de
www.MaterialsViews.com
relative to the monomers, the hydrolysis of the polymer chains
may be enhanced. HT-5 has the highest alkalinity of all HTs
prepared here and yet showed the lowest Mw value, which sug-
gests that this result may be due to the high hydroxyl content of
HT. On the other hand, the use of HT-3 gave the highest Mw at
around 0.6 wt%. Since HT-3 had the highest structural ordering
of the layer structure, a layer structure may have a close cor-
relation with the catalysis activity. Moreover, the effects of the
increased ordering in the layer structure on the Mw increase
is higher than the countervail effects of the abovementioned
alkalinity increase, because the Mw values of HT-3 were higher
than those of HT-2 and HT-1.
In order to investigate the layer structure effects on the Mw
in more detail, we calcinated the HT to lower the layer ordering.
As shown in the lowest XRD diagram of Figure 1, the diffrac-
tion peaks of the layer structure in the HT-3 XRD diagram dis-
appeared in the XRD diagram of the calcinated HT-3. Figure 3
shows the Mw values of the copolymers prepared in the pres-
ence of calcinated HT catalysts with contents of 0.4 and
0.6 wt%. One can observe that calcination reduced the Mw values
of the copolymers prepared in the presence of HT-1, HT-2, HT-3
and HT-4, although the Mw differences were not very dramatic
for HT-5, which has a high alkalinity. Thus, the layer structures
were effective to catalyze the acidolysis by HT. The polymer
chains seem too large to intercalate into the gaps of the HT’s.
However, the literature on PET preparation has reported that
aromatic compounds such as terephthalic acid intercalated
efficiently into HT layers, where polymer chains ends can
react with them[11]. In the present case, coumarate compounds
and a number of acetylated chain ends for the hyperbranched
poly(4HCA-co-DHCA)s might react around the surface of the
layer portions, which can effectively catalyze their acidolysis.
HT1
HT2
HT3
HT4
HT5
90
80
70
60
50
40
30
20
10
0
0
0.2
0.4
0.6
0.8
1
1.2
Catalyst (wt %)
Figure 2. Molecular weights of poly(4HCA-co-DHCA)s prepared in the
presence of HT with various Al/Mg ratios.
without a solvent. In order to investigate the catalysis in more
detail, various HT’s were prepared and used for the copoly-
merization. Figure 1 shows the X-ray diffraction patterns of
HT with various Mg/Al ratios, where HT-X was prepared by a
Mg/Al ratio of X/1. All HTs showed the XRD patterns character-
istic of HT, including the intense diffraction peaks at 2θ = 11.5o
(003) and 23.1o (006) (arrows in Figure1) assigned to the layer
structure with a spacing of 7.69 Å[9]. When the Mg/Al ratio was
increase from 1 to 3, the intensity of the layer diffraction peaks
increased, and showed a maximum at the Mg/Al ratio of 3. In
addition, the alkalinity of HT should increase with an increase
in the Mg/Al ratio according to the literature[10]
.
2.3. High-performance Resin Preparation
The effects of the HT composition change on the Mw of
the copolymers were investigated (Figure 2). Figure 2 shows
the catalyst amount dependence of the Mw, and demonstrated
maximum values at 0.6 wt% for all HT compositions. If the
hydroxyl ions of HT are present at too high of a composition
The copolymers with this monomer composition were liquid
crystalline, as previously reported[5], and showed glass tran-
sition around 120−140 °C independent of catalysis species
(representative DSC chart: Figure S4). We then made liquid
90
90
0
0 wt%
catalyst
.4.4wt
0.4 wt catalyst
0.4 wt%
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
a
b
0.6 wt catalyst
0.6 wt%
0.6wt catalyst
0.6 wt%
1
2
3
4
5
1
2
3
4
5
Mg composition to Al in HT
Mg composition to Al in calcinated HT
Figure 3. Mw values of poly(4HCA-co-DHCA) prepared in the presence of calcinated (a) and normal (b) HT catalysts with contents of 0.4 and 0.6 wt%.
©
4
wileyonlinelibrary.com
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427

www.afm-journal.de
www.MaterialsViews.com
crystalline observations of these copolymers. Figure 4 shows
crossed-polarizing microscopic images of the poly(4HCA-co-
DHCA)s prepared in the presence of various catalysts. The
copolymers prepared in NaOAc showed a clear birefringence
and fluidity in their melted state, thus demonstrating the for-
mation of the liquid crystalline structure. However, no textures
typical of a nematic phase were observed. The copolymers in
the other catalysts except for the HT’s also gave similar results.
On the other hand, the copolymers prepared in the presence of
HT’s showed some clear threads (Figure 4), where represent-
ative threads were marked by arrows in the HT-3, HT-4, and
HT-5 images. These results indicate that copolymers prepared
in the presence of HT catalysts formed clear interfaces in their
orientation domains, which might be induced by the fineness
of the copolymer structures.
The fine structure inducing efficient liquid crystallization
might also induce good orientation of the copolymer resins. We
then tried to prepare oriented resins using the long glass fillers
(GF; 3 μm ϕ × 5 mm) set along the longitudinal axes of the
molding as shown in the illustration inset in Figure 5b. The
pictures from Figure 5a are microscopic photos of the GF, taken
under cross-nicol polarization using a first-order retardation
plate (λ = 530 nm) inserted into the light path. The left picture
showed no light transmission through the GF itself to demon-
strate non-orientation. On the other hand, the polymer coating
on the GF showed birefringence in the middle and right
pictures. From these figures, it was observed that the polymer
birefringence was negative, as evidenced by both the subtractive
birefringence (blue color) in the GF lying from the upper left to
the lower right, and the additive birefringence (orange color) in
the fibers lying from the upper right to the lower left. Since the
polymers have phenylene vinylene groups in their main chains,
the negative birefringence may indicate that the polymer back-
bones and branches were oriented along the GF axes. If GF was
incorporated into the resin in the LC state, the polymer chains
should be oriented along the GF. As a result, the mechanical
strength (σ) measured by the three-point bending test showed
a good correlation with the GF composition, to attain a ca.
140 MPa mechanical strength, which is high enough to use as
a super-engineering resin (Figure 5b). If the polymer prepared
in the presence of sodium acetate was used, the σ was reduced
to around 100 MPa. This high value may be strongly attributed
to the LC orientation induced by GF incorporation. Next, the
dynamic moduli were measured by dynamic mechanical
Figure 4. Crossed-polarizing microscopy of poly(4HCA-co-DHCA)s prepared in the presence of various catalysts.
©
wileyonlinelibrary.com
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
5

www.afm-journal.de
www.MaterialsViews.com
Figure 5. (a) Mechanical strength, σ, at fracture of oriented poly(4HCA-co-DHCA) resin reinforced by glass fibers (GF) lying along the orientation
direction. (b) Dynamic mechanical analyses of the same resin with GF content of 30 wt% which was annealed at 300 °C for 20 min. The inset picture
was the image of the annealed resin whose σ at fracture was kept high 85 MPa.
analyses. The temperature dependence of the storage modulus
G′, the loss modulus G″, and the G″/G′ = Tan δ were shown
in Figure 5c. The G′ decreased slightly at two steps around
120 and 220 °C with the accompanying G″ peaks, but stayed
high (0.6−0.7 GPa) at 300 °C. The G′ values are easily converted
into the elastic modulus E’ by the Equation 1:
were used in the copolymerization of 4HCA with DHCA. The
copolymer poly(4HCA-co-DHCA) prepared in the presence of
HT catalysts showed high molecular weight values and a narrow
molecular weight distribution. A 0.6 wt% concentration was con-
sidered to be the best ratio for copolymer preparation. On the
other hand, the use of HT with a Mg/Al ratio of 3 (HT-3) gave the
highest values for the copolymer Mw at around 0.6 wt%. Since
HT-3 had the highest structural ordering of the layer structure,
the layer structure may have a close correlation with the catalysis
activity for acidolysis. The copolymers prepared in the presence
of HTs showed some clear threads. These results indicate that
the copolymers prepared in the presence of the HT catalysts
formed clear interfaces in orientation domains, which might be
induced by the fineness of the copolymer structures. Cross-polar-
izing microscopy revealed that the polymer chains were oriented
on the surface of glass fibers, and that the resin hybridized by
the glass fiber fillers aligning along the longitudinal axis showed
a very high mechanical strength. Furthermore, the hybrid resin
annealed at 300 °C for 20 min showed a softening temperature
of 305 °C while keeping a high mechanical strength of 85 MPa
and a high mechanical modulus over 1 GPa. These values were
high enough for use as a bio-based super-engineering plastic.
E = 2G(1+γ )
(1)
under the assumption of a Poisson’s ratio, γ, of 0.2-0.5 (most
solids showed this γ range). The resin showed an E’ range
between 1.3−2.1 GPa at 300 °C, which is also high enough to
use as a super-engineering resin. The Tan δ curves showed no
peaks at 120 or 220 °C, but a peak at around 305 oC, and thus the
softening temperature of the resin was regarded as 305 °C. After
this measurement, the resin darkened in color, possibly due to
the negative thermal effects on σ. However, the resin showed a
high σ value of 85 MPa at room temperature after thermal treat-
ment at 305 °C for 20 min. Thus, we prepared a bio-based resin
with high-thermal resistance and high-mechanical properties.
3. Conclusions
We successfully prepared high-performance and functional poly-
mers with rigid and photoreactive phenols, especially poly(p-cou-
maric acid-co-caffeic acid). Various alkalescent catalysts such as
Na2CO3, NaOAc, NaH2PO4, Na2HPO4, Na3PO4, and hydrotalcite
4. Experimental Section
Hydrotalcite Preparation: Mg-Al-NO3-hydrotalcite (Mg-Al-HT) with 2:1
atomic ratio of Mg to Al was prepared in a nitrogen atmosphere to avoid
©
6
wileyonlinelibrary.com
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427

www.afm-journal.de
www.MaterialsViews.com
carbonation in air. Magnesium nitrate hexahydrate (20.5 g, 0.08 mol)
and aluminum nitrate nonahydrate (15.0 g, 0.04 mol) were dissolved in
100 mL of deionized water, and sodium carbonate and sodium hydroxide
were dissolved in distilled water. The solution of sodium hydroxide and
sodium carbonate was then added into the above solution by a peristaltic
pump at a rate of 1 ml/min. The resultant slurry was stirred for 2 h under
nitrogen at room temperature. The slurries were cooled down to room
temperature slowly over 2 h, and filtered under nitrogen to obtain a
white powder. The powder was washed with distilled water until the pH
reached 7. It was dried under vacuum at 100 °C to obtain Mg-Al-NO3-
hydrotalcite. Mg-Al-NO3-hydrotalcites (Mg-Al-HTs) with different atomic
ratios of Mg to Al (1:1, 2:1, 3:1, 4:1, 5:1) were prepared in a nitrogen
atmosphere to avoid carbonation in air. All of the Mg-Al-hydrotalcites
(HT-1, HT-2, HT-3, HT-4, HT-5) were calcinated by incubating them at
450 °C for 4 h.
microscopy. The samples were sandwiched between two glass plates,
and were heated at a rate of 10 °C/min by a METTLER TOLEDO FP82HT
Hot Stage (Greifensee, Switzerland). The glass transition temperatures
were confirmed by differential scanning calorimetry (DSC) measurement
(EXSTAR6100; Seiko Instruments Inc., Chiba, Japan). The three-point
bending test was performed using a tensile materials testing machine
(INSTRON, Canton City, MA, USA, 3365-L5). The samples were set over
two fixtures 30 mm apart, and the center of each sample was pressed
from the opposite direction. The fracture strength was defined as the
maximum stress in the stress–strain curve.
Supporting Information
Supporting Information is available from the Wiley Online Library or
from the author.
Polymerization: Poly(4HCA-co-DHCA)s were synthesized by a two-
step reaction in one bottle by the following procedure (Scheme 1).
Monomers of 4HCA (60 mmol) and DHCA (40 mmol) were mixed and
mechanically stirred at 150 °C in the presence of acetic anhydride (40 ml)
as a condensation reagent plus catalysts such as HT, until the solution
became homogeneous (for about 2 hours). The solution was further
heated to 200 °C, and the polymerization was carried out for another
4 hours in vacuo. The reaction solution increased its viscosity gradually,
and was finally solidified to not allow further stirring. After the reaction
was finished by cooling to room temperature, the materials were milled
into a powder and purified by washing with acetone (yields: 76−93 wt%).
Resin preparation: The resins were prepared in a casting mold to a
length of 50 mm, a width of 6.5 mm and a thickness of 3.5 mm by the
following procedure. The polymer powders were placed into the mold,
and glass filler-fibers (3 μm ϕ × 5 mm) of various compositions were set
along the longitudinal axis. The mixture was then heated to 200 °C and
pressed at 5 MPa, and kept for 5 min.
Acknowledgements
This research was financially supported partially from a Grant-in-Aid for
Comprehensive Support Programs for Creation of Regional Innovation
Science and Technology Incubation Program in Advanced Regions
“Practical Application Research” (Kaneko project) in Japan Science and
Technology Agency (JST), and mainly a Grant-in-Aid for Advanced Low
Carbon Technology Research and Development Program (ALCA) in JST.
Received: February 11, 2012
Revised: April 5, 2012
Published online:
Measurements: The 1H-NMR spectra of the poly(4HCA-co-DHCA)
were measured with a NMR spectrometer (JEOL FX 400) at 400 MHz..
[1] K. Okano, A. Kondo, H. Noda, Eco Ind. 2006, 11, 43.
[2] Y. Imai, High Perform. Polym. 1995, 7, 337.
[3] N. Ricarda, J. M. Anthony, M. Cathie Nat. Biotechnol. 2004, 22, 746.
[4] D. C. Whitehead, Nature 1964, 202, 417.
[5] T. Kaneko, H. T. Tran, D. J. Shi, M. Akashi, Nat. Mater. 2006, 5, 996.
[6] S. Vaiionpaa, P. Rokkanen, P. Tormala, Prog. Polym. Sci. 1989, 14,
679.
1
The H NMR chemical shifts in parts per million (ppm) were recorded
downfield from 0.00 ppm using tetramethylsilane (TMS) as an internal
reference using TFA-d/CD2Cl2 as a solvent. The FT-IR spectra of the
copolymers were measured at 25 °C on a Perkin Elmer Spectrum One
spectropolarimeter between 4000−400 cm−1 . The molecular weight
of the poly(DHCA-co-4HCA)s was determined by gel permeation
chromatography (GPC) using a Shodex GPC-101 with a connection
column system of 803 and 804 that was calibrated with polystyrene
standards (eluant: dimethylformamide). The wide angle X-ray diffraction
(WAXD) of hydrotalcite and calcinated hydrotalcite as a catalyst was
recorded on an X-ray diffractometer (RINT UltraX18) equipped with a
scintillation counter, using CuKα radiation (20 kV, 80 mA; wavelength =
1.5418 Å), which was monochromated by a parabolic multilayer mirror
using transmission geometry. The thermotropic properties, such as the
phase transition, of P(4HCA-co-LCA) was observed by crossed-polarizing
[7] A. Vaccari, Catal. Today 1998, 41, 53.
[8] H. Staeuber, V. Voerckel, J. Wiegner, WO 2 003004547, 2003.
[9] A. Vaccari, M. Gazzano, in Preparation of Catalysts VI, Studies in Sur-
face Science and Catalysis, (Eds: G. Poncelet, J. Martens, B. Delmon,
P. A. Jacobs, P. Grange), Elsevier, Amsterdam, 1995, 91, 309.
[10] C.-M. Yang, C.-N. Lee, C.-H. Chou, Bot. Bull. Acad. Sin. 2002, 43,
299.
[11] F. A. Toufaili, G. Feix, K. H. Reichert Macromol. Mater. Eng. 2006,
291, 1144.
©
wileyonlinelibrary.com
Adv. Funct. Mater. 2012,
DOI: 10.1002/adfm.201200427
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
7