Bio-based aromatic polyesters from a novel bicyclic diol derived from d-mannitol

Article abstract of DOI:10.1021/ma3013288

2,4:3,5-Di-O-methylene-d-mannitol, abbreviated as Manx, is a d-mannitol-derived compound with the secondary hydroxyl groups acetalized with formaldehyde. The bicyclic structure of Manx consists of two fused 1,3-dioxane rings, with two primary hydroxyl gro

Full text of DOI:10.1021/ma3013288

Article
pubs.acs.org/Macromolecules
Bio-Based Aromatic Polyesters from a Novel Bicyclic Diol Derived
from D‑Mannitol
C. Lavilla, A. Martínez de Ilarduya, A. Alla, M. G. García-Martín, J. A. Galbis, and S. Mun
†
†
†
‡
‡
oz-Guerra*,†
̃
†
Departament d’Enginyeria Química, Universitat Politec
Departamento de Química Organica y Farmaceutica, Universidad de Sevilla, Profesor García Gonzal
S Supporting Information
̀
nica de Catalunya, ETSEIB, Diagonal 647, 08028 Barcelona, Spain
‡
́
́
́
ez 2, 41012 Sevilla, Spain
*
ABSTRACT: 2,4:3,5-Di-O-methylene-D-mannitol, abbreviated as
Manx, is a D-mannitol-derived compound with the secondary hydroxyl
groups acetalized with formaldehyde. The bicyclic structure of Manx
consists of two fused 1,3-dioxane rings, with two primary hydroxyl
groups standing free for reaction. A homopolyester made of Manx and
dimethyl terephthalate as well as a set of copolyesters of poly(butylene
terephthalate) (PBT) in which 1,4-butanediol was replaced by Manx up
to 50% were synthesized and characterized. The polyesters had M in
w
−1
the 30 000−52 000 g mol range and a random microstructure and
were thermally stable up to nearly 370 °C. They displayed outstanding
high T with values from 55 to 137 °C which steadily increased with the
g
content in Manx. Copolyesters containing up to 40% of Manx were
semicrystalline and adopted the crystal structure of PBT. Their stress−
strain parameters were sensitively affected by the presence of
carbohydrate-based units with elongation at break decreasing but tensile strength and elastic moduli steadily increasing with
the degree of replacement.
INTRODUCTION
known as isosorbide, which is prepared by dehydration of D-
glucose coming from cereal starch, is the only bicyclic
carbohydrate-based monomer industrially available today.
Isosorbide and other less accessible dianhydrohexitols deriva-
tives are receiving recently a great deal of attention as building
blocks for the synthesis of aromatic copolyesters with increased
■
Bio-based polymers are nowadays attracting a great deal of
interest, not only for their potential to reduce the utilization of
petrochemicals but also for increasing the added-value of
1
−4
agriculture products and wastes.
Carbohydrates constitute
an interesting renewable source for being used as polymer
building blocks; they are the most abundant type of biomass
feedstock, and they are found in a very rich variety of structures
displaying great stereochemical diversity. However, they
possess an excess of functional groups that upon poly-
condensation would lead to undesirable cross-linking reactions
unless special precautions are taken. Although some linear
polyesters have been synthesized using carbohydrate-based
13−15
T .
g
The two hydroxyl groups of isosorbide are secondary,
and due to their different spatial position in the molecule, they
display different reactivity. These features seriously hamper the
polycondensation reaction in the melt, so isosorbide polyesters
obtained by this method display rather limited molecular
16,17
weights.
Another type of carbohydrate-based bicyclic
monomer is that obtained by internal acetalization, which has
been shown to be very suitable to prepare polyesters by
polycondensation in the melt since they are able to react at a
rate similar to that of other acyclic conventional mono-
5
,6
monomers bearing free hydroxyl groups, most syntheses have
been carried out with derivatives in which the exceeding
functional groups have been appropriately protected.
7
−10
18−20
mers.
Among carbohydrate-derived monomers, those with a cyclic
structure have achieved a privileged position because, in
addition to their natural origin, they are able to provide
polycondensates with improved properties, especially those
related to polymer chain stiffness, as it is the case of the glass
transition temperature. A high Tg is nowadays a greatly
appreciated property in polyesters that are addressed to
packaging under heating or to the manufacture of containers
for pressurized gaseous beverages. Thus, 2,5-furandicarboxylic
acid has been reported as a potential alternative to replace
terephthalic acid for the preparation of aromatic polyesters
In this work we present a new bicyclic carbohydrate-based
monomer useful for the preparation of linear polycondensates.
2
,4:3,5-Di-O-methylene-D-mannitol, abbreviated as Manx, is a
D-mannitol-derived compound with the secondary hydroxyl
groups acetalized with formaldehyde. A set of copolyesters of
poly(butylene terephthalate) (PBT) in which the 1,4-
butanediol has been replaced by Manx have been synthesized
Received: June 27, 2012
Revised: September 10, 2012
1
1,12
based on renewable sources.
1,4:3,6-Dianhydro-D-glucitol,
©
XXXX American Chemical Society
A
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
temperature for 5 min, and then it was cooled at 20 °C min− to the
selected crystallization temperature, where it was left to crystallize until
saturation. For morphological study, isothermal crystallizations under
the same conditions were carried out in an Olympus BX51 polarizing
optical microscope coupled to a THMS LINKAM heating plate and a
cooling system LNP (liquid nitrogen pump). Thermogravimetric
1
and characterized. PBT is a well-known thermoplastic aromatic
polyester, with a melting temperature near 225 °C and a glass
transition temperature around 30 °C, which is used in a wide
21
variety of engineering applications. Nevertheless, despite
being innocuous for humans, PBT and other aromatic
polyesters are considered not to be environmentally friendly
−1
analyses were performed under a nitrogen flow of 20 mL min at a
22
materials due to their nonrenewable origin. In this work
special attention is paid to study the effect of the introduction
of renewable Manx on the glass transition temperature, thermal
stability, and crystallizability of the resulting PBT copolyesters
because of the relevance that these properties have not only for
the technical use of PBT but also for the potential application
that this novel carbohydrate-based monomer may have in the
synthesis of other polycondensates. Contrary to isosorbide, the
two hydroxyl groups of Manx remaining free for reaction are
primary, and since Manx possess a 2-fold axis of symmetry, they
display the same reactivity. Moreover, the use of Manx as
polycondensation monomer leads to regioregular polymer
chains, provided that it is made to react with nondirectional
monomers.
−1
heating rate of 10 °C min , within a temperature range of 30−600 °C,
using a PerkinElmer TGA 6 equipment. Sample weights of about 10−
15 mg were used in these experiments. Films for mechanical testing
measurements were prepared with a thickness of ∼200 μm by casting
−1
from solution (100 g L ) in either chloroform or a mixture of
chloroform and hexafluoroisopropanol (5:1); the films were then cut
into strips with a width of 3 mm while the distance between testing
marks was 10 mm. The tensile strength, elongation at break, and
−1
Young’s modulus were measured at a stretching rate of 30 mm min
at 23 °C on a Zwick 2.5/TN1S testing machine coupled with a
compressor Dalbe DR 150. X-ray diffraction patterns were recorded
on the PANalytical X′Pert PRO MPD θ/θ diffractometer using the Cu
Kα radiation of wavelength 0.1542 nm from powdered samples
coming directly from synthesis.
Monomer Synthesis. 1,6-Di-O-benzoyl-D-mannitol. A solution
of 28.1 g of benzoyl chloride (200 mmol) in dry pyridine (70 mL) was
added dropwise to a dispersion of 36.4 g of D-mannitol (200 mmol) in
70 mL of dry pyridine. The mixture was stirred at room temperature
for 5 h and then poured into ice−water. The precipitated solid was
filtered, washed with cold water and with chloroform, dried, and
EXPERIMENTAL SECTION
■
Materials. The reagents D-mannitol (ACS reagent grade), benzoyl
chloride (99+%), paraformaldehyde (95%), 1,4-butanediol (99%), and
dimethyl terephthalate (99+%) and the catalyst dibutyl tin oxide
23
recrystallized from ethanol. Yield: 36%; mp 189−193 °C [lit. 188−
1
(
DBTO, 98%) were purchased from Sigma-Aldrich. Solvents used for
192 °C]. H NMR (300.1 MHz, DMSO), δ (ppm): 8.1 (m, 4H, o-
purification and characterization were purchased from Panreac, and
they all were of either technical or high-purity grade. All the reagents
and solvents were used as received without further purification.
General Methods. H and C NMR spectra were recorded on a
Bruker AMX-300 spectrometer at 25.0 °C operating at 300.1 and 75.5
MHz, respectively. Samples were dissolved in either deuterated
chloroform, deuterated dimethyl sulfoxide, or a mixture of deuterated
chloroform and trifluoroacetic acid (9:1), and spectra were internally
referenced to tetramethylsilane (TMS). About 10 and 50 mg of sample
ArH), 7.6 (m, 2H, p-ArH), 7.5 (m, 4H, m-ArH), 5.1 (bs, 2H, OH),
4.7−4.3 (m, 6H, OCH
CH
CHOHCHOH). 13C NMR (75.5 MHz, DMSO), δ (ppm): 166.0
(CO), 133.1, 130.1, 129.3, 128.6, 69.1, 68.3, 67.7.
, OH), 3.9 (m, 2H, CH CHOH, 3.7 (d, 2H,
2
2
2
1
13
1,6-Di-O-benzoyl-2,4:3,5-di-O-methylene-D-mannitol. To a mix-
ture of 28.0 g of 1,6-di-O-benzoyl-D-mannitol (72 mmol) and 28.0 g of
paraformaldehyde (930 mmol), 22 mL of sulfuric acid 96% was added
dropwise, and the mixture was stirred for 3 h at room temperature.
The reaction mixture was then repeatedly extracted with chloroform.
The combined organic layers were washed with ammonia (12% w/w)
and water and dried over anhydrous sodium sulfate. The solution was
evaporated to a solid residue, which was recrystallized from ethanol.
Yield: 52%; mp 121−122 °C [lit. 121 °C]. H NMR (300.1 MHz,
CDCl ), δ (ppm): 8.1 (m, 4H, o-ArH), 7.6 (m, 2H, p-ArH), 7.4 (m,
4H, m-ArH), 5.0−4.8 (dd, 4H, OCH O), 4.8−4.3 (m, 4H, COOCH ),
4.4 (m, 2H, OCH CH), 4.2 (m, 2H, OCH
CHCH). 13C NMR (75.5
MHz, CDCl ), δ (ppm): 166.3 (CO), 133.2, 129.7, 129.6, 128.4, 88.5,
1
13
dissolved in 1 mL of solvent were used for1 H and C NMR,
respectively. Sixty-four scans were acquired for H and 1000−10 000
1
3
for C with 32K and 64K data points as well as relaxation delays of 1
1
24
1
and 2 s, respectively. For conformational studies H NMR spectra
were recorded from 60 to −60 °C in the NMR spectrometer equipped
with a variable-temperature unit. Temperatures were selected at 20 °C
interval. For each temperature the sample was held for 10 min to reach
thermal equilibrium. 2D NOE spectrum (NOESY) was recorded at a
fixed temperature (T = 298.1 K) with a standard pulse sequence
3
2
2
2
2
3
71.1, 66.7, 63.7.
(
noesytp) with a mixing time of 2 s over a sweep width of 1397 Hz
2,4:3,5-Di-O-methylene-D-mannitol. A dispersion of 15.5 g of 1,6-
di-O-benzoyl-2,4:3,5-di-O-methylene-D-mannitol (37 mmol) in 200
mL of dry methanol was stirred overnight with a small piece of
sodium. The solution was treated with cation exchange resin, the resin
was filtered, and the filtrate was concentrated to dryness. The resulting
semisolid residue was washed with diethyl ether and recrystallized
using 2048 data points in the t dimension and 256 increments in the
t1 dimension. The repetition delay was 2 s, and 256 scans were
collected for each t increment. H NMR simulated spectra were
obtained with SpinWorks 3.1.8 program (Kirk Marat, University of
Manitoba). Intrinsic viscosities of polymers dissolved in dichloroacetic
acid were measured in an Ubbelohde viscosimeter thermostated at
2
1
1
2
5
1
from ethanol. Yield: 72%; mp 139−140 °C [lit. 139 °C]. H NMR
(300.1 MHz, CDCl ), δ (ppm): 5.0−4.8 (dd, 4H, OCH O), 4.2 (m,
2H, HOCH CH), 4.1 (m, 2H, HOCH CHCH), 4.0−3.7 (m, 4H,
HOCH ), 1.9 (bs, 2H, OH). C NMR (75.5 MHz, CDCl ), δ (ppm):
2
5.0 ± 0.1 °C. Gel permeation chromatograms were acquired at 35.0
3
2
°C using a Waters equipment provided with a refraction index
2
2
13
detector. The samples were chromatographed with 0.05 M sodium
trifluoroacetate−-hexafluoroisopropanol (NaTFA−HFIP) using a
polystyrene−divinylbenzene packed linear column with a flow rate
of 0.5 mL min . Chromatograms were calibrated against poly(methyl
methacrylate) (PMMA) monodisperse standards. The thermal
behavior of polyesters was examined by DSC using a PerkinElmer
DSC Pyris 1. DSC data were obtained from 3 to 5 mg samples at
heating/cooling rates of 10 °C min under a nitrogen flow of 20 mL
min . Indium and zinc were used as standards for temperature and
enthalpy calibration. The glass-transition temperatures were deter-
mined at a heating rate of 20 °C min from rapidly melt-quenched
polymer samples. The treatment of the samples for isothermal
crystallization experiments was the following: the thermal history was
removed by heating the sample up to 250 °C and left at this
2
3
87.2, 73.5, 65.8, 59.6.
Polymer Synthesis. PB
Manx T copolyesters were obtained from
y
x
−
1
a mixture of 1,4-butanediol, 2,4:3,5-di-O-methylene-D-mannitol, and
dimethyl terephthalate with the selected composition. PBT and
PManxT homopolyesters were obtained by reacting dimethyl
terephthalate with 1,4-butanediol and 2,4:3,5-di-O-methylene-D-
mannitol, respectively. The reactions were performed in a three-
necked, cylindrical-bottom flask equipped with a mechanical stirrer, a
nitrogen inlet, and a vacuum distillation outlet. An excess of diol
mixture to dimethyl terephthalate was used, and dibutyl tin oxide
(DBTO, 0.6% molar respect to monomers) was the catalyst of choice.
The apparatus was vented with nitrogen several times at room
temperature in order to remove air and avoid oxidation during the
−1
−
1
−1
B
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
polymerization. Transesterification reactions were carried out under a
low nitrogen flow at the selected temperature. Polycondensation
reactions were left to proceed at the selected temperature under a
Scheme 1. Synthesis of 2,4:3,5-Di-O-methylene-D-mannitol
0
.03−0.06 mbar vacuum. Then, the reaction mixture was cooled to
room temperature, and the atmospheric pressure was recovered with
nitrogen to prevent degradation. The resulting polymers were
dissolved in chloroform or in a mixture of chloroform and
trifluoroacetic acid (9:1) and precipitated in excess of methanol in
order to remove unreacted monomers and formed oligomers. Finally,
the polymer was collected by filtration, extensively washed with
methanol, and dried under vacuum.
PBT Homopolyester. 60% molar excess of 1,4-butanediol to
dimethyl terephthalate. Transesterification reactions at 180 °C for 1
h, at 200 °C for 1 h, and at 240 °C for 0.5 h under a low nitrogen flow.
Polycondensation reactions at 260 °C for 2 h under a 0.03−0.06 mbar
1
vacuum. H NMR (300.1 MHz, CDCl /TFA), δ (ppm): 8.13 (s, 4H,
3
13
ArH), 4.50 (t, 4H OCH CH ), 2.02 (t, 4H, OCH CH ). C NMR
2
2
2
2
(
2
75.5 MHz, CDCl /TFA), δ (ppm): 168.0 (CO), 133.7, 129.9, 66.2,
5.1.
PManxT Homopolyester. 5% molar excess of 2,4:3,5-di-O-
3
in the Supporting Information and detailed in the Experimental
Section. The coupling between the two protons of the
methylene acetalic group with a J = −6.2 Hz confirms the
presence of the two fused six-membered rings and then the
2,4:3,5 arrangement of the bicyclic structure. It should be
stressed that the synthesis route used for the preparation of
Manx, although effective for the purpose of the work, is not
environmentally friendly. Obviously, an alternative synthetic
route or an improvement of the existing one will need to be
developed to make this monomer of fully practical use and to
render benefits to the environment.
This bicyclic diol Manx possesses a 2-fold axis of symmetry,
and therefore its two hydroxyl groups will display the same
reactivity in the polycondensation reaction producing regiore-
gular polymer chains. Since the two rings are fused, a fairly high
degree of rigidity should be in principle expected for Manx
although it could be largely relieved if interconversion between
possible conformers takes place. The rigidity of the monomer is
critical for the preparation of polymers with improved thermal
and mechanical properties. To appraise the effect that this novel
diol monomer will have on the stiffness of the polyesters thence
produced, a conformational analysis of 1,6-di-O-benzoyl-
methylene-D-mannitol to dimethyl terephthalate. Transesterification
reactions at 160 °C for 1 h and at 180 °C for 2 h under a low nitrogen
flow. Polycondensation reactions at 180 °C for 5 h under a 0.03−0.06
mbar vacuum. H NMR (300.1 MHz, CDCl /TFA), δ (ppm): 8.1 (s,
4
4
26
1
3
H, Ar−H), 5.2−5.0 (m, 4H, OCH O), 4.9−4.5 (m, 4H, OCH CH),
2
2
13
.7 (m, 2H, OCH CH), 4.3 (m, 2H, OCH CHCH). C NMR (75.5
2
2
MHz, CDCl /TFA), δ (ppm): 167.5 (CO), 133.5, 130.3, 88.6, 71.4,
6
3
6.7, 64.4.
PB Manx T Copolyesters. The copolyesters were obtained by a
x
y
similar procedure, with polymerization conditions slightly differing for
each composition feed.
PB Manx T and PB Manx T. 5% molar excess of the diol
9
0
10
80
20
mixture to dimethyl terephthalate. Transesterification reactions at 160
C for 1 h, at 200 °C for 1 h, and at 240 °C for 0.5 h under a low
nitrogen flow. Polycondensation reactions at 240 °C for 2.5 h under a
°
0
.03−0.06 mbar vacuum.
PB Manx T. 5% molar excess of the diol mixture to dimethyl
7
0
30
terephthalate. Transesterification reactions at 160 °C for 1 h, at 200 °C
for 1 h, and at 230 °C for 0.5 h under a low nitrogen flow.
Polycondensation reactions at 230 °C for 3 h under a 0.03−0.06 mbar
vacuum.
PB Manx T. 5% molar excess of the diol mixture to dimethyl
6
0
40
2
,4:3,5-di-O-methylene-D-mannitol was undertaken. This die-
terephthalate. Transesterification reactions at 160 °C for 1 h, at 200 °C
for 1 h, and at 220 °C for 0.5 h under a low nitrogen flow.
Polycondensation reactions at 220 °C for 3.5 h under a 0.03−0.06
mbar vacuum.
ster is an adequate model compound for aromatic polyesters
and copolyesters made from Manx. The two most probable
conformations for the 2,4:3,5-di-O-methylene-D-manno bicy-
27
PB Manx T. 5% molar excess of the diol mixture to dimethyl
5
0
50
clic structure are depicted in Scheme 2. In order to assess the
terephthalate. Transesterification reactions at 160 °C for 1 h, at 200 °C
for 1 h, and at 210 °C for 0.5 h under a low nitrogen flow.
Polycondensation reactions at 210 °C for 4 h under a 0.03−0.06 mbar
vacuum.
Scheme 2. Preferential Conformers of 1,6-Di-O-benzoyl-
2,4:3,5-di-O-methylene-D-mannitol
1
NMR Characterization of PB Manx T Copolyesters . H NMR
x
y
(
300.1 MHz, CDCl /TFA), δ (ppm): 8.1 (s, 4H, Ar−H), 5.2−5.0 (m,
3
y·4H, OCH O), 4.9−4.5 (m, y·4H, OCH CH), 4.7 (m, y·2H,
OCH CH), 4.5 (t, x·4H, OCH CH ), 4.3 (m, y·2H, OCH CHCH),
2
(
7
2
2
2
2
2
2
13
.0 (t, x·4H, OCH CH ). C NMR (75.5 MHz, CDCl /TFA), δ
2
2
3
ppm): 168.3 (CO), 167.5 (CO), 134.2−133.3, 130.4, 130.2, 88.6,
1.4, 66.7, 66.5, 64.4, 25.4.
RESULTS AND DISCUSSION
■
Monomer Synthesis and Conformation. The bicyclic
diol 2,4:3,5-di-O-methylene-D-mannitol (Manx) was prepared
from D-mannitol following the chemical synthetic route
depicted in Scheme 1. Primary hydroxyl groups of D-mannitol
were first protected as benzoyl esters, and then the addition of
paraformaldehyde led to cyclic acetalization of the secondary
hydroxyl groups in the 2,4:3,5 arrangement with the two fused
relative preference of Manx for these two conformations, a
variable temperature H NMR study was carried out in the +60
1
to −60 °C range, and 2D-NOESY spectra were recorded at
room temperature. In the case that I and II conformers were
1
present, two signals for each proton should appear in the H
1
13
1,3-dioxane rings. H and C NMR spectra of Manx are shown
NMR spectra at low temperatures since no interconversion is
C
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
3
0
expected to take place under such conditions. On the contrary,
single proton signals were observed along the whole interval
and the only detected change was an upfield shift of the signals
with heating (see Supporting Information). It can be concluded
therefore that no conformational interconversion occurs and
that only one conformer is present along the whole range of
namate established a conformation in the solid state for the
bicyclic unit similar to which is determined in this work. The
conclusion derived from this conformational study is that the
preferred conformation of Manx is I and that this conformation
is well stable; such features will confer to this monomer an
enhancing stiffness effect on the polymer chain in which it is
inserted.
1
temperatures. The analysis of the coupling constants of the H
NMR spectra suggested that conformer I is the preferred one
for Manx. In fact, NMR spin simulation using the SpinWorks 3
program provided the spin−spin coupling constants (see
Supporting Information) for the ABXYY′X′A′B′ system, in
which small long-range couplings between Y and X′ protons
were detected. The calculated coupling constants were
Polymer Synthesis and Chemical Structure. The
polymerizations involving 2,4:3,5-di-O-methylene-D-mannitol
were carried out in the total absence of solvents to imitate as
far as possible the conditions usually applied in the industrial
practice. PManxT homopolyester, from 2,4:3,5-di-O-methyl-
ene-D-mannitol and dimethyl terephthalate, as well as
PB Manx T copolyesters from 2,4:3,5-di-O-methylene-D-man-
nitol, 1,4-butanediol, and dimethyl terephthalate, were prepared
by a two-step melt-polycondensation process using DBTO as
catalyst (Scheme 3). For comparison purposes, the parent PBT
x
y
JAB = JA′B′ = −11.98 Hz;
JBY = JB′Y′ = 6.71 Hz;
JYX = JY′X′ = 8.60 Hz;
JAY = JA′Y′ = 2.91 Hz;
J
= JY′Y = 5.3 Hz;
YY′
J
= JY′X = −0.58 Hz
YX′
Scheme 3. Polymerization Reactions Leading to PB Manx T
x
y
Applying these coupling constants to the Karplus equation
Copolyesters
2
8,29
derived for alditols,
the torsional angles Ψ and Φ could be
estimated. The values obtained were 160° and 48°, respectively,
which are very close to the angles measured for conformer I but
very far from those of conformer II.
The identity of conformer I as the preferred one was strongly
supported by 2D NOESY spectrum (Figure 1). As expected for
homopolyester was obtained from 1,4-butanediol and dimethyl
terephthalate using the same polycondensation procedure. In
the preparation of PB Manx T copolyesters, the incorporation
x
y
of the diols into the copolyesters was accurately controlled by
using a 5% molar excess of the diol mixture to dimethyl
terephthalate and by initiating transesterification reactions at
mild temperature to prevent volatilization of diols. Temper-
ature was progressively increased to avoid crystallization of
oligomers, and polycondensation reactions were performed at
temperatures between 210 and 240 °C and under vacuum to
facilitate the removal of volatile byproducts; lower temperatures
and longer reaction times were used in copolyesters with higher
contents in Manx to minimize the decomposition of this sugar
compound. When polymerizations were ended, the reaction
mixtures were dissolved either in chloroform or in a mixture of
chloroform and trifluoroacetic acid and precipitated in
methanol to obtain the polymers in yields close to 85−90%.
The synthesis results obtained for sugar-based PManxT
homopolyester and PB Manx T copolyesters are gathered in
Figure 1. 2D NOESY spectrum of 1,6-di-O-benzoyl-2,4:3,5-di-O-
methylene-D-mannitol. Small arrows indicate NOE signals.
x
y
Table 1 together with data for the parent PBT homopolyester.
The precipitated PB Manx T copolyesters were obtained
x
y
−1
conformation I, strong NOE signals were detected for H and
one of the acetal methylene protons, whereas no NOE signals
with intrinsic viscosities between 0.8 and 1.2 dL g , weight-
Y
average molecular weights confined in the 38 000−52 000 g
−1
were observed for H . In conformation II the short distances
mol interval, and dispersities in the 2.3−2.5 range. Molecular
X
between H and one of the protons of the acetal methylene
weights of PB Manx T copolyesters slightly decay with the
X
x
y
should be reflected in the 2D spectra with strong NOE signals,
which is not the case. It is worthy to note that crystal structure
studies on 2,4:3,5-di-O-methylene-D-mannitol-1,6-di-trans-cin-
content in Manx, in accordance with the values observed for
PManxT homopolyester. The GPC analysis of the reaction
product (without being subjected to any treatment) afforded
D
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 1. Molar Composition, Molecular Weight, and Microstructure of PB Manx T Copolyesters
x
y
molar composition
microstructure
number-
average
sequence
lengths
a
d
feed
copolyester
molecular weight
dyads
randomness
yield
(%)
BManx/
ManxB
b
c
c
c
copolyester
PBT
X
B
X
Manx
X
B
X
Manx
[η]
M
n
M
w
D
BB
ManxManx
n
B
n
Manx
R
90
86
87
86
85
88
85
100
90
80
70
60
50
0
0
100
0
0.93
1.18
0.84
0.75
0.83
0.77
17 100
11 800)
20 300
14 200)
16 500
11 500)
16 600
10 400)
16 400
11 600)
16 300
10 900)
12 900
41 300
(40 500)
51 200
2.4
(3.4)
2.5
(
(
(
(
(
(
PB90Manx10
PB80Manx20
PB70Manx30
PB60Manx40
PB50Manx50
PManxT
T
10
20
30
40
50
91.0
9.0
75.6
59.9
44.9
35.0
23.1
21.7
34.0
44.0
47.8
48.4
2.7
6.1
8.0
4.5
3.0
2.5
2.0
1.3
1.4
1.5
1.7
2.2
0.92
0.96
0.99
0.99
0.97
(50 800)
41 000
(3.6)
2.5
T
T
T
T
80.3
69.2
59.2
49.0
0
19.7
30.8
40.8
51.0
(40 200)
38 500
(3.5)
2.3
11.1
17.2
28.5
(37 900)
40 100
(3.6)
2.4
(39 800)
38 900
(3.4)
2.4
(38 400)
30 200
(3.5)
2.3
100
100
0.51
1
(
8100)
(29 300)
(3.6)
a
b
−1
Molar composition determined by integration of the H NMR spectra. Intrinsic viscosity in dL g measured in dichloroacetic acid at 25 °C.
Number- and weight-average molecular weights in g mol and dispersities measured by GPC in HFIP against PMMA standards after (without
parentheses) and before purification (in parentheses). Randomness index of copolyesters statistically calculated on the basis of the C NMR
c
−1
d
13
analysis.
weight-average molecular weights very close to those obtained
for the precipitated product but with significantly higher
dispersities. Such differences indicate the presence of minor
amounts of oligomeric fractions or remaining monomers in the
showing that all copolyesters had compositions very close to
those of their corresponding feeds.
The microstructure of PB Manx T copolyesters was
x
y
determined by 13C NMR analysis. The signals of all the
1
raw product that were then removed by precipitation. The H
magnetically different carbons contained in the repeating units
1
3
NMR spectra corroborated the chemical structure of the
copolyesters with all signals being correctly assigned to the
different protons contained in their repeating units (Figure 2).
Integration of the proton signals arising from B and Manx units
led to quantify the composition of the copolyesters in such
units. Data provided by this analysis are given in Table 1,
of the copolyesters appear well resolved in the C NMR
spectra (see Supporting Information) and in particular those
arising from the nonprotonated aromatic carbons, which come
out to be sensitive to sequence effects at the dyad level. As
shown in Figure 3 for the whole set of PB Manx T
x
y
copolyesters, each resonance of the nonprotonated aromatic
carbons appears split so that four peaks are seen in the 133−
1
35 ppm chemical shift interval corresponding to the three
types of dyads (BB, BManx and ManxB, ManxManx) that are
feasible along the copolyester chain. By integration of these
peaks, the dyad contents, the number-average sequence lengths,
and the degree of randomness were estimated (Table 1),
leading to the conclusion that the microstructure of the
copolyesters was at random in all cases.
Thermal Properties. 2,4:3,5-Di-O-methylene-D-mannitol is
a thermally fairly stable solid compound which starts to
volatilize above 150 °C and displays a sublimation temperature
of 280 °C without perceivable decomposition. The thermal
stability of PManxT homopolyester and PB Manx T copolyest-
x
y
ers made from this compound was evaluated by thermogravim-
etry under inert atmosphere and compared with that displayed
by PBT. TGA traces are depicted in Figure 4, and thermal data
provided by this analysis are presented in Table 2. The weight
loss profiles generated reveal that all polyesters start to
decompose well above 360 °C with a thermal degradation
mechanism involving one main step with the maximum rate at
temperatures steadily increasing with the content in Manx
units. The same trend is observed for °T , and these results are
5%
in accordance with the high thermal stability observed for
max
PManxT homopolyester, with °T5% and Td at 378 and 421
°C, respectively. The valuable conclusion drawn from this
1
Figure 2. Compared H NMR spectra of PB Manx T copolyesters.
x
y
E
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 3. 13C NMR signals used for the microstructure analysis of PB Manx T copolyesters with indication of the dyads to which they are assigned.
x
y
higher than the aromatic PBT homopolyester. Regarding
PB Manx T copolyesters, their T increase steadily with the
x
y
g
content in Manx units, with minimum and maximum values
corresponding to their respective PBT and PManxT homo-
polyesters (Figure 5), as should be expected from their
statistical microstructure. As expected from its cyclic stiff
nature, the effect of Manx on T of PBT is largely greater than
g
that exerted by the incorporation of acyclic sugar units such as
31
trimethoxy xylitol or L-arabinitol. It has even a much more
pronounced effect than 2,3:4,5-di-O-methylene-galactitol, an-
other acetalized sugar diol constituted by two nonfused
dioxolane rings, which has been recently reported by us as
capable of raising the T of PBT by near 30 °C when it replaces
g
20
1
,4-butanediol in a 40%. The effect of Manx turns to be
similar to that of isosorbide; in fact, both PBT copolyesters
1
4,16
containing 40% of either Manx or isosorbide
display a T of
g
around 90 °C. No doubt the fused bicyclic structure
characteristic of both Manx and isosorbide is unique in
providing the polyester chain with a degree of stiffness not
achievable with the insertion of rotable bicyclic units, as it is the
case of the acetalized hexitol with galacto configuration.
DSC traces of polyesters in the powdered form registered at
first heating are depicted in Figure 6b. PB Manx T copolyesters
x
y
with molar contents in Manx below or equal to 40%, as well as
PBT homopolyester, gave heating traces with melting
endotherms indicating that they are semicrystalline. Compar-
ison of melting temperatures and enthalpies of semicrystalline
PB Manx T copolyesters with that of PBT homopolyester leads
Figure 4. (a) TGA traces (solid lines) and derivative curves (dashed
lines) of PBT and PManxT homopolyesters. (b) TGA traces of
PB Manx T copolyesters.
x
y
x
y
to the conclusion that the insertion of Manx units gives place to
a significant decrease in both Tm and ΔHm (Table 2).
thermogravimetric study is that the insertion of Manx units in
aromatic polyesters instead of reducing their thermal stability
contributes to a significant increase in their decomposition
temperatures. The fact of improving the thermal stability of
commonly used aromatic polyesters such as PBT can broaden
even more the application window of these materials.
PB Manx T copolyester and PManxT homopolyester appear
50
50
to be amorphous. DSC data recorded from polyester films
prepared by casting from solution are not far from those
obtained from powders, the higher coincidence being found for
lower contents in Manx units.
Other thermal properties of prime importance in connection
with the potential application of these copolyesters are the glass
transition temperature (T ) and the melting temperature (T ).
Isothermal Crystallization. The cooling DSC traces
obtained from molten samples revealed that PB Manx T
x
y
g
m
For instance, an increase in the T of these polyesters could
copolyesters with molar contents in Manx below or equal to
20%, as well as PBT homopolyester were able to crystallize
from the melt. After crystallization from the melt, these
polyesters recovered about 75−95% of their initial crystallinity
and displayed almost the same melting temperatures. Given the
relevance of this property regarding polymer processing, the
isothermal crystallization of PB Manx T and PB Manx T
g
open their use in the hot-filled and pasteurized-container fields.
The glass transition temperatures of the PManxT and PBT
homopolyesters and PB Manx T copolyesters were measured
x
y
as the inflection point of the heating DSC traces of samples
quenched from the melt (Figure 6a). A remarkable feature of
PManxT homopolyester is that it has a T more than 100 °C
g
90
10
80
20
F
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 2. Thermal Properties of PB Manx T Copolyesters
x
y
TGA
DSC
e
e
e
first heating
cooling
second heating
a
b
c
d
ΔHm (J g−1
ΔH (J g−1)
ΔHm (J g−1
)
copolyester
PBT
°T5% (°C)
Td (°C)
W (%)
Tg (°C)
Tm (°C)
)
Tc (°C)
Tm (°C)
c
371
371
372
374
376
408
2
31
55
66
77
88
223
56.2
(54.3)
34.1
196
43.3
30.4
23.4
223
44.0
(
(
(
(
(
223)
PB Manx T
408
410
411
411
3
8
8
9
197
159
140
198
184
31.3
24.1
90
10
196)
184
(33.0)
26.0
PB Manx T
80
20
183)
162
(27.0)
5.5
PB Manx T
70
30
162)
122
(16.6)
5.0
PB Manx T
60
40
119)
(9.8)
PB Manx T
377
378
412
421
11
13
100
137
50
50
PManxT
a
b
c
d
Temperature at which 5% weight loss was observed. Temperature for maximum degradation rate. Remaining weight at 600 °C. Glass-transition
−1
e
temperature taken as the inflection point of the heating DSC traces of melt-quenched samples recorded at 20 °C min . Melting (T ) and
crystallization (T ) temperatures and melting (ΔH ) and crystallization (ΔH ) enthalpies measured by DSC at heating/cooling rates of 10 °C min
of precipitated samples (without parentheses) and of films (in parentheses).
m
−1
c
m
c
Figure 5. Glass-transition temperature versus composition plot for
PBT copolyesters containing 2,4:3,5-di-O-methylene-D-mannitol
2
0
(
Manx), 2,3:4,5-di-O-methylene-galactitol (Galx), 2,3,4-tri-O-meth-
31
yl-L-arabinitol (Ar), or 2,3,4-tri-O-methylxylitol (Xy).
copolyesters and PBT homopolyester was comparatively
studied in the 150−210 °C interval. Unfortunately, not all of
them could be compared at exactly the same isothermal
crystallization temperature due to the large differences in
crystallization rates displayed by them and to the short ranges
of temperature in which crystallization evolution is measurable
by DSC. Nevertheless, crystallization conditions were chosen as
close as possible in order to be able to draw out meaningful
conclusions. The Hoffman−Weeks plot of T versus T showed
m
c
a good correlation (see Supporting Information) and provided
the equilibrium melting temperatures, which, as expected,
continue to display the same trend with composition as was
observed for the T measured for nonisothermally crystallized
samples.
m
Figure 6. (a) DSC heating traces of PB Manx T copolyesters
x
y
quenched from the melt. (b) DSC melting traces of the PB Manx T
x
y
Kinetic data afforded by the Avrami analysis of the results
obtained at the selected crystallization temperatures are
gathered in Table 3. The evolution of the relative crystallinity,
Xc, with crystallization time and the corresponding Avrami data
plots log[−ln(1 − X )] versus log(t − t ) for some illustrative
copolyesters without being subjected to any thermal treatment.
temperature, the values of the latter being in the 2.0−2.6 range
corresponding to a complex axialitic−spherulitic crystallization
as was observed by polarizing optical microscopy. The double-
logarithmic plot indicates that only primary crystallization takes
place in the selected time intervals and that the presence of
Manx units depresses the crystallizability in terephthalate
copolyesters. The valuable conclusion that can be drawn from
c
0
crystallization experiments are depicted in Figure 7. The
morphological appearance of the crystallized material observed
by polarized optical microscopy is shown in the Supporting
Information. It is seen that for each polyester the crystallization
half-time as well as the Avrami exponent n increase with
G
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 3. Isothermal Crystallization Data of PB Manx T
x
y
Copolyesters
Tc
t0
t1/2
Tm
copolyester
PBT
(°C)
(min)
(min)
n
−log k
(°C)
200
0.19
0.51
2.33
0.15
0.26
0.31
0.59
1.93
0.19
0.23
0.29
0.44
0.98
0.82
2.68
12.83
1.13
2.14
4.37
8.53
19.43
1.61
2.45
3.50
5.60
11.85
2.14
2.45
2.56
2.01
2.12
2.43
2.52
2.57
2.02
2.04
2.07
2.13
2.20
−0.25
1.02
2.78
0.15
0.75
1.64
2.42
3.34
0.56
0.93
1.26
1.74
2.46
223.9
225.5
226.9
194.5
196.3
198.0
199.8
202.1
184.1
185.3
186.9
188.8
190.5
2
2
05
10
PB Manx T
165
90
10
1
1
1
1
70
75
80
85
PB Manx T
150
80
20
1
1
1
1
55
60
65
70
Figure 8. Powder WAXS profiles (a) and stress−strain curves (b) of
PB Manx T copolyesters.
x
y
regarding both spacing and relative intensities is shared by
PB Manx T copolyesters with low content in Manx, revealing
x
y
32
that the triclinic crystal structure of PBT must be retained in
polyesters. The crystallinity index was estimated as the quotient
between crystalline area and total area of the X-ray diffraction
pattern, showing that PB Manx T, PB Manx T,
9
0
10
80
20
PB Manx T, and PB Manx T were semicrystalline with
70
30
60
40
crystalline indexes decreasing for increasing contents in Manx
units. However, PB Manx T copolyester and PManxT
5
0
50
copolyester did not show any discrete reflection characteristic
of crystalline material. These X-ray diffraction results are in full
agreement with DSC results and confirmed that PB Manx T
Figure 7. Isothermal crystallization of PBT, PB Manx T, and
x
y
90
10
PB Manx T at the indicated temperatures. Relative crystallinity
versus time plot (a) and log−log plot (b).
copolyesters with molar contents in Manx below or equal to
40% are semicrystalline.
8
0
20
To evaluate the influence of the presence of Manx in the
mechanical properties of copolyesters, tensile assays of PManxT
copolyester as well as PB Manx T copolyesters were carried out
this study is that PB Manx T and PB Manx T copolyesters
9
0
10
80
20
continue displaying the ability of crystallizing from the melt as
their parent homopolyester PBT although at lower crystal-
lization rates.
x
y
using the films that were prepared by casting as described in the
Experimental Section. For comparison purposes, mechanical
properties of PBT were also tested. According to enthalpy
values (Table 2), the degree of crystallinity of these films must
be close to that displayed by powders with Xc steadily
decreasing with the increasing content of the copolyester in
Manx units to become 0 for PB Manx T and PManxT (Table
Crystal Structure and Stress−Strain Behavior. Powder
X-ray diffraction analyses were performed for all PB Manx T
x
y
copolyesters as well as PManxT and PBT homopolyesters.
Powder X-ray diffraction profiles are presented in Figure 8a,
and Bragg spacings present in such patterns are listed in Table
50
50
4
. In agreement with DSC results, copolyesters containing up
4). The stress−strain curves resulting from tensile essays are
depicted in Figure 8b, and the mechanical parameters measured
in these tests are compared in Table 4. PManxT homopolyester
displayed higher elastic modulus and tensile strength than PBT,
and accordingly PB Manx T copolyesters present a nearly
to 40% of Manx produced discrete diffraction scattering
distinctive of semicrystalline material, whereas fully plain
profiles characteristic of amorphous material were obtained
from PB Manx T as well as from the PManxT homopolyester.
50
50
x
y
The PBT pattern is characterized by five prominent reflections
at 5.6, 5.1, 4.3, 3.8, and 3.6 Å. Essentially the same pattern
steady trend consisting of a continuous increase in both elastic
modulus and tensile strength and a decrease in ductility when
H
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 4. Powder X-ray Diffraction Data and Mechanical Properties of PB Manx T Copolyesters
x
y
X-ray diffraction data
mechanical properties
elastic modulus (MPa) tensile strength (MPa) elongation at break (%)
a
b
copolyester
d
(Å)
Xc
PBT
5.6 s
5.1 s
4.3 s
3.8 s
3.6 m
3.6 m
3.6 w
3.6 w
3.6 w
0.48
0.39
0.32
0.11
0.10
0
841 ± 15
852 ± 13
871 ± 25
888 ± 17
891 ± 19
909 ± 26
1067 ± 29
42 ± 5
44 ± 6
45 ± 7
46 ± 5
50 ± 7
52 ± 5
59 ± 6
14 ± 3
12 ± 3
9 ± 2
8 ± 3
5 ± 2
3 ± 1
2 ± 1
PB Manx T
5.6 s
5.1 s
4.3 m
4.3 m
4.3 w
4.3 w
3.8 s
90
10
PB Manx T
5.6 m
5.6 w
5.6 w
5.1 m
5.1 w
5.1 w
3.8 m
3.8 w
3.8 w
80
20
PB Manx T
70
30
PB Manx T
60
40
PB Manx T
50
50
PManxT
0
a
Bragg spacings measured in powder diffraction patterns for samples coming directly from synthesis. Intensities visually estimated as follows: m,
b
medium; s, strong; w, weak. Crystallinity index calculated as the quotient between crystalline area and total area. Crystalline and amorphous areas in
the X-ray diffraction pattern were quantified using PeakFit v4.12 software.
their content in Manx units increases. The observed variations
Notes
in the stress−strain behavior are fully consistent with the
The authors declare no competing financial interest.
changes in T . Apparently, the mechanical moduli of these
g
copolyesters are mainly determined by the mobility of the
chains in the amorphous phase rather than by the structural
stiffness induced by the presence of crystalline domains.
ACKNOWLEDGMENTS
■
Financial support for this work was provided by MICINN
Spain) with Grant MAT2009-14053-C02 and by AGAUR
Catalonia) with Grant 2009SGR1469. The authors are also
indebted to MEC (Spain) for the FPU grant awarded to
Cristina Lavilla.
(
(
CONCLUSIONS
■
For the first time, polyesters from the biobased 2,4:3,5-di-O-
methylene-D-mannitol monomer, obtained by internal acetali-
zation of the secondary hydroxyl groups of D-mannitol, have
been successfully synthesized. By taking special care of
polycondensation conditions, polyesters and statistical copo-
lyesters with pretty high molecular weights were obtained in
good yields. The incorporation of the sugar derived diol
improved appreciably the thermal stability of the resulting
polyesters. The most remarkable effect of copolymerization was
however noticed on the glass-transition temperature which
increased with the content in 2,4:3,5-di-O-methylene-D-
mannitol almost linearly with a slope of about of 1 °C/%
REFERENCES
■
(
1) Wool, R.; Sun, S. Biobased Polymers and Composites; Academic
Press: New York, 2005.
(2) Pillai, C. K. S. Des. Monomers Polym. 2010, 13, 87−121.
(3) Gandini, A. Green Chem. 2011, 13, 1061−1083.
(
(
5
(
2
(
4) Chen, G. Q.; Patel, M. K. Chem. Rev. 2012, 112, 2082−2099.
5) Kiely, D. E.; Chen, L.; Lin, T. H. J. Am. Chem. Soc. 1994, 116,
71−578.
6) Kiely, D. E.; Chen, L.; Lin, T. H. J. Polym. Sci., Polym. Chem.
000, 38, 594−603.
7) Okada, M. Prog. Polym. Sci. 2002, 27, 87−133.
(8) Metzke, M.; Guan, Z. Biomacromolecules 2008, 9, 208−215.
9) Williams, C. K. Chem. Soc. Rev. 2007, 36, 1573−1580.
mol, allowing fine-tuning of T of PBT over a wide range.
g
Consequently, the mechanical moduli of the copolyesters also
increased significantly in the same sense. Although copoly-
merization depressed the crystallinity and crystallizability of
PBT, those copolyesters containing up to 40% of sugar based
units were semicrystalline and adopted the crystal structure of
PBT, and those containing up to 20% were able to crystallize
from the melt. The 50/50 copolyester and the polyester
entirely made of Manx units were amorphous, at least under the
crystallization conditions used in this work. The bicyclic sugar-
based diol investigated in this work as monomer for
polycondensation stands out not only for being a sustainable
compound but also for providing polyesters with satisfactory
molecular weights and with improved thermal and mechanical
properties; nevertheless, the synthesis of this compound will
need to be improved in order to make it simpler and to avoid
the use of environmentally unfriendly reagents.
(
(10) Kricheldorf, H. R. J. Macromol. Sci. 1997, C37, 599−631.
(11) Gandini, A.; Coelho, D.; Gomes, M.; Reis, B.; Silvestre, A. J. D.
J. Mater. Chem. 2009, 19, 8656−8664.
(
12) Gomes, M.; Gandini, A.; Silvestre, A. J. D.; Reis, B. J. Polym. Sci.,
Polym. Chem. 2011, 49, 3759−3768.
13) Fenouillot, F.; Rousseau, A.; Colomines, G.; Saint-Loup, R.;
Pascault, J. P. Prog. Polym. Sci. 2010, 35, 578−622.
14) Sablong, R.; Duchateau, R.; Koning, C. E.; de Wit, G.; van Es,
D.; Koelewijn, R.; van Haveren, J. Biomacromolecules 2008, 9, 3090−
097.
15) Wu, J.; Eduard, P.; Thiyagarajan, S.; Jasinska-Walc, L.; Rozanski,
A.; Fonseca Guerra, C.; Noordover, B. A. J.; van Haveren, J.; van Es, D.
S.; Koning, C. E. Macromolecules 2012, 45, 5069−5080.
(16) Kricheldorf, H. R.; Behnken, G.; Sell, M. J. Macromol. Sci., Pure
Appl. Chem. 2007, 44, 679−684.
(
(
3
(
(
1
(
17) Storbeck, R.; Ballauff, M. J. Appl. Polym. Sci. 1996, 59, 1199−
202.
18) Lavilla, C.; Alla, A.; Martínez de Ilarduya, A.; Benito, E.; García-
Martín, M. G.; Galbis, J. A.; Munoz-Guerra, S. Biomacromolecules 2011,
2, 2642−2652.
19) Lavilla, C.; Alla, A.; Martínez de Ilarduya, A.; Benito, E.; García-
Martín, M. G.; Galbis, J. A.; Munoz-Guerra, S. J. Polym. Sci., Polym.
Chem 2012, 50, 1591−1604.
20) Lavilla, C.; Alla, A.; Martínez de Ilarduya, A.; Benito, E.; García-
Martín, M. G.; Galbis, J. A.; Munoz-Guerra. Polymer 2012, 53, 3432−
445.
21) Gallucci, R. R.; Patel, B. R. Poly(Butylene Terephthalate). In
ASSOCIATED CONTENT
■
̃
1
(
*
S
Supporting Information
Additional figures (Figures 1−7). This material is available free
of charge via the Internet at http://pubs.acs.org.
̃
(
AUTHOR INFORMATION
̃
■
3
(
Corresponding Author
*E-mail sebastian.munoz@upc.edu.
Scheirs, J., Long, T. E., Eds.; Modern Polyesters, Chemistry and
I
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Technology of Polyesters and Copolyesters; John Wiley & Sons:
Chichester, 2004; pp 293−321.
(
22) Tripathy, A. R.; MacKnight, W. J.; Kukureka, S. N.
Macromolecules 2004, 37, 6793−6800.
(
(
(
23) Brigl, P.; Gruner, H. Ber 1932, 65B, 641−645.
24) Haworth, W. N.; Wiggins, L. F. J. Chem. Soc. 1944, 58−61.
25) Haskins, W. T.; Hann, R. M.; Hudson, C. S. J. Am. Chem. Soc.
1
(
943, 65, 67−70.
26) Burden, I. J.; Stoddart, J. F. J. Chem. Soc., Perkin Trans. 1 1975, 7,
6
(
(
66−674.
27) Mills, J. A. Adv. Carbohydr. Chem. 1955, 10, 1−53.
28) Franks, F.; Dadok, J.; Ying, S.; Kay, R. L.; Grigera, J. R. J. Chem.
Soc., Faraday Trans. 1991, 87, 579−585.
29) Jardetzky, O.; Roberts, G. C. K. Molecular Biology; Academic
Press: New York, 1981; p 201.
30) Bernstein, J.; Green, B. S.; Rejto
02, 323−328.
31) Alla, A.; Hakkou, K.; Zamora, F.; Martínez de Ilarduya, A.;
Galbis, J. A.; Munoz-Guerra, S. Macromolecules 2006, 39, 1410−1416.
32) Hall, I. H. The determination of the structures of aromatic
(
(
̈
, M. J. Am. Chem. Soc. 1980,
1
(
̃
(
polyesters from their wide-angle X-ray diffraction patterns. In Hall, I.
H., Ed.; Structure of Crystalline Polymers; Elselvier Applied Science:
London, 1984; pp 39−78.
J
dx.doi.org/10.1021/ma3013288 | Macromolecules XXXX, XXX, XXX−XXX