Shape dependence in the formation of condensed phases exhibited by disubstituted sucrose esters

Article abstract of DOI:10.1002/chem.200600368

We report on the self-organizing properties of sucrose esters that are di-(1′,6′, 1′,6, and 6,6′)-substituted with aliphatic chains of identical or different chain lengths and levels of saturation. For the materials possessing two saturated aliphatic chains, the compounds exhibited thermotropic lamellar smectic A phases. A remarkable new phase transition was observed for the di-octadecanoyl homologue in which one smectic A phase transformed into another with a continuous change in layer spacing, but with a discontinuous change in the correlation length. The incorporation of long cis-unsaturated chains led to increased cross-sectional areas of the chains relative to the sucrose head groups and, hence, columnar phases were observed.

Full text of DOI:10.1002/chem.200600368

FULL PAPER
DOI: 10.1002/chem.200600368
Shape Dependence in the Formation of Condensed Phases Exhibited by
Disubstituted Sucrose Esters
[
a, d]
[b, e]
[a]
[a, f]
[a, g]
ValØrie Molinier,
Paul J. J. Kouwer,
Juliette Fitremann, [Ac] lain Bouchu,
[
b]
Grahame Mackenzie, Yves Queneau,* and John W. Goodby*
Abstract: We report on the self-organ-
izing properties of sucrose esters that
are di-(1’,6’, 1’,6, and 6,6’)-substituted
with aliphatic chains of identical or dif-
ferent chain lengths and levels of satu-
ration. For the materials possessing two
saturated aliphatic chains, the com-
pounds exhibited thermotropic lamellar
smectic A phases. A remarkable new
phase transition was observed for the
di-octadecanoyl homologue in which
one smectic A phase transformed into
another with a continuous change in
layer spacing, but with a discontinuous
change in the correlation length. The
incorporation of long cis-unsaturated
chains led to increased cross-sectional
areas of the chains relative to the su-
crose head groups and, hence, colum-
nar phases were observed.
Keywords: fatty acids · glycolipids ·
liquid crystals · phase transitions ·
sucrose esters
Introduction
Glycolipids are typically found in the outer leaflets of bio-
logical membranes, and there is a particularly high incidence
of their presence in the membranes of axons and dendrons
[
a] Dr. V. Molinier, Dr. J. Fitremann, Dr. A. Bouchu, Dr. Y. Queneau
Laboratoire de Chimie Organique
UMR 5181 CNRS; UniversitØ Lyon 1; INSA
Institut National des Sciences AppliquØes de Lyon
Bât. J. Verne, 20 avenue A. Einstein
[1,2]
found in nerve cells.
Furthermore, glycolipids have been
used in the creation of artificial membranes and have often
been used as nonionic surfactants. In these applications, gly-
colipids have been shown to possess lyotropic and/or ther-
6
9621 Villeurbanne Cedex (France)
Fax : (+33)4724-38896
E-mail: yves.queneau@insa-lyon.fr
[3]
[
b] Dr. P. J. J. Kouwer, Dr. G. Mackenzie
Department of Chemistry, The University of Hull
Cottingham Road, Hull, HU6 7RX (UK)
motropic liquid-crystal properties. Property–structure anal-
yses indicate that most thermotropic mesogenic variants are
[4]
smectic A or columnar phases. Conversely, the addition of
[
c] Prof. J. W. Goodby
water to glycolipids, which causes swelling of the head
groups, results in the formation of lamellar, cubic and/or col-
umnar phases as a function of the induced curvature in the
packing arrangements of the molecules. Consequently, a
higher degree of liquid-crystalline diversity is found in the
lyotropic state relative to the thermotropic state. Interesting-
ly, although this richness is found in the lyotropic state,
more materials exhibit thermotropic phases than lyotropic
phases. Comparison of the number and range of thermo-
tropic materials with those possessing lyotropic phases indi-
cates that glycolipids are not particularly good amphiphiles.
Sucrose fatty-acid esters are nonionic surfactants, display-
ing good properties in terms of emulsification, mildness, and
Department of Chemistry, The University of York
Heslington, York, YO10 5DD (UK)
Fax : (+44)1904-432-516
E-mail: jwg500@york.ac.uk
[
d] Dr. V. Molinier
Current address:
Laboratoire de Chimie Organique et MacromolØculaire
UMR CNRS 8009, École Nationale SupØrieure de Chimie de Lille
BP 108, 59652 Villeneuve DꢀAscq Cedex (France)
[
e] Dr. P. J. J. Kouwer
Current address: Department of Chemistry, MIT
7
7 Massachusetts Avenue, Cambridge, MA02139–4307 (USA)
[
f] Dr. J. Fitremann
Current address: Laboratoire des IMRCP
CNRS UMR 5623, UniversitØ Paul Sabatier
Bât. 2R1, 118 Route de Narbonne, 31062 Toulouse Cedex 4 (France)
[5–16]
toxicology, and are used as food or cosmetic emulsifiers.
Due to structural complexity (i.e., mixtures with different
patterns of substitution and stereochemistry), the physico-
chemical properties of defined compounds have been stud-
[
g] Dr. A. Bouchu
Current address: Tereos, Service Innovation
rue du Petit Versailles, B.P. 16, 59239 Thumeries (France)
Chem. Eur. J. 2007, 13, 1763 – 1775
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1763

ied less extensively than other kinds of nonionic surfactants,
such as polyoxyethylenic surfactants or alkylpolyglucosides.
Although the surface activities and other properties for
monosubstituted sucrose esters in solution are well docu-
lose, which is associated with virulent strains of tubercle ba-
cilli, and 6,6’-di-O-palmitoylsucrose possess immunostimu-
[38–41]
lant properties and antitumour activity.
Our initial stud-
ies on the homologous material, 6,6’-di-O-stearoylsucrose,
demonstrate that it is liquid crystalline, and forms a smectic
liquid-crystal phase in which the molecules have extended
[17–24]
mented,
the thermotropic liquid-crystal properties for
such materials have only recently been investigated in
detail. One commercial mixture of sucrose oleate has been
[42]
conformational structures.
Our results indicate that the
[25]
studied, along with the shear-induced phase transitions of
liquid-crystal properties of such materials could possibly be
important in relation to their biological function. This report
provides an extensive study of the self-assembly and self-or-
ganization of a broad range of disubstituted sucrose esters.
Compounds 1a–d, 2a–h, 3a,b, and 4a were synthesized
from unprotected sucrose by using selective methods of
[26]
sucrose stearate blends. More recently, a systematic study
of the effects of aliphatic chain length and degree of unsatu-
ration on the thermotropic liquid-crystal properties of
[27]
monosubstituted sucrose fatty-acid esters has been made.
A
C
H
T
R
E
U
N
G
Amphiphiles with sugars or cyclic and acyclic polyols as
polar heads with single, apolar aliphatic chains attached to
[43]
esterification.
The 1’,6’-diesters, 1a–d, were prepared by
[3,4,28–30]
the head groups tend to display smectic phases.
Ther-
enzymatic methods, whereas the 6,6’-diesters 2a–h, 3a,b,
and the 1’,6-diester, 4a, were obtained by Mitsunobu cou-
motropic columnar mesophases with the head groups locat-
ed towards the interior of the columns have also been ob-
tained by grafting several fatty-acid chains onto the polar
head, thereby increasing the volume ratio of fatty-acid chain
to polar head group, leading to changes in curvature and,
[44]
pling reactions. These methods, though very selective, do
not supply totally pure regioisomers, therefore, further pu-
rification by using preparative HPLC was required. Due to
[45,46]
the known migration phenomena,
regioisomers at the
[3,31–33]
hence, packing constraints of the molecules.
Columnar
secondary positions cannot be synthesized in pure form. In-
vestigations of the thermotropic mesophase behavior and
structures of the sucrose derivatives were made by using
thermal polarizing light optical microscopy, differential scan-
ning calorimetry, and X-ray diffractrometry.
mesophases also have been obtained by increasing the
volume of the head group relative to the aliphatic region.
Thus, head groups containing more than one sugar moiety,
but still possessing a single aliphatic chain, tend to form col-
umnar phases in which the aliphatic chains are located to-
wards the interiors of the columns, with head groups to-
wards the exterior. Interestingly, in such molecular architec-
tures that maintain a rodlike shape, which is the case for
most alkylpolyglucosides, smectic phases are again ob-
Experimental Section
General synthetic strategies: 1’,6’-Diesters 1a–d were obtained by trans-
esterification of mono-1’-O-lauroylsucrose and mono-1’-O-palmitoylsu-
crose with the desired vinyl (or trifluoroethyl) ester (or the correspond-
ing carboxylic acid) in acetone in the presence of a lipase, as described
[34–36]
served.
As the polar head becomes more bulky, it also
adopts a wedge-shaped conformation, as in the case of
certain regioisomers of sucrose hydroxyalkylethers and
monosubstituted sucrose fatty-acid esters, with the conse-
quence that columnar or cubic mesophases are ob-
[
47]
previously.
The starting monoester sample was obtained after a first
esterification of unprotected sucrose in the presence of a protease, as de-
[48–52]
scribed in the literature,
and further purification by semipreparative
[4,27,37]
served.
HPLC to obtain the pure 1’-isomer. The synthesis of these 1’,6’-diesters is
In this study, we report on the thermotropic liquid-crystal-
line properties of amphiphilic glycolipids designed with two
aliphatic chains attached at the 1’,6’, 1’6, and 6,6’ positions
to the sucrose scaffold. This work is motivated by the fact
that both Cord Factor, the 6,6’-dimycolic ester of a,a-treha-
shown in Scheme 1.
Homogeneous 6,6’-diesters 2a–h were obtained by the reaction of su-
crose with the desired carboxylic acid under Mitsunobu conditions
[
40,41,44]
(
Scheme 2).
The pure diesters were isolated and purified by semi-
preparative HPLC. The mixture of diesters comprising 3a, 3b, and 4a
was obtained by treatment of sucrose monolaurate under the same condi-
Scheme 1. Synthesis of sucrose 1’,6’-diesters by enzymatic methods.
1764
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ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 1763 – 1775

Disubstituted Sucrose Esters
FULL PAPER
Scheme 2. Synthesis of sucrose, homogeneous, and mixed 6,6’-diesters by the Mitsunobu reaction.
tions. The relative position of the two chains at OH-6 and OH-6’, respec-
tively, could not be ascertained for each of the diesters 3a and 3b. As
these were synthesized from a mixture of monolaurate isomers, they
must be considered as a mixture of two compounds.
or vinylic ester or carboxylic acid in the presence of a lipase. The 1’-
monoester (1’-O-palmitoylsucrose, 86 mg, 0.15 mmol) was dissolved in
acetone (1.5 mL). The acylating agent (palmitoleyl acid trifluoroethyl
ester, 254 mg, 5 equiv) was added, followed by the immobilized lipase
(Novozyme 435, 170 mg). The reaction was conducted at 458C under
slowmagnetic stirring (100 rpm) for 16 h (up to 40 h in some cases). The
1’,6’-diester was obtained after filtration, evaporation of the solvent and
purification on a silica-gel column eluted with dichloromethane/acetone/
1
The purities of the compounds were ascertained by conducting H and
1
3
C NMR spectroscopy, HPLC, and HRMS or elemental analysis (if suffi-
cient sample was available).
Evaluation of physical properties: Phase identifications and determina-
tion of phase-transition temperatures were carried out, concomitantly, by
thermal polarizing light microscopy using a Zeiss Universal polarizing
transmitted light microscope equipped with a Mettler FP52 microfurnace
in conjunction with an FP50 Central Processor. Photomicrographs were
obtained by using a Zeiss polarizing light microscope equipped with a
Nikon AFM camera. Differential scanning calorimetry was used to deter-
mine enthalpies of transition and to confirm the phase-transition temper-
atures determined by optical microscopy. Differential scanning thermo-
methanol/water 78:10:10:1.5 v/v (R
8%).
f
=0.25 for compound 1d, 46 mg,
3
1’-O-Lauroyl-6’-O-palmitoylsucrose 1b: [a]
H NMR (500 MHz, MeOD): d=0.83–1.11 (m, 6H; 2CH
D
=+36 (c=0.6, THF);
), 1.17–1.47 (m,
1
3
40H; (CH ) ), 1.56–1.73 (m, 4H; 2CH ), 2.28–2.45 (m, 4H; 2CH2a),
2
20
2b
3.36 (t + MeOD, 1H; J4,3 =J4,5 =9.5 Hz, H ), 3.42 (dd, 1H; J =9.5 Hz,
4
2,3
2
3,4
3
6b,6a
J2,1 =3.8 Hz, H ), 3.69 (t, 1H; J =J3,2 =9.5 Hz, H ), 3.73 (dd, 1H; J =
12.3 Hz, J6b,5 =5.4 Hz, H ), 3.80–3.87 (m, 2H; H , H ), 3.88 (td, 1H;
6b
6a
5
À1
grams (scan rate 108Cmin ) were obtained by using a Perkin–Elmer
J5’,4’ =J5’,6’a =8.3 Hz, J5’,6’b =2.8 Hz, H ), 4.03 (t, 1H; J =J4’,5’ =8.3 Hz,
5’
4’,3’
DSC 7 PC system operating on DOS software. The results obtained were
H ), 4.08 (d, 1H; J =8.3 Hz, H ), 4.12 (d, 1H; J
1’b,1’a
=12.0 Hz, H1’b),
4
’
3’,4’
3’
À1
standardized to indium (measured onset 156.688C, DH 28.47 Jg , lit.
4
.33 (dd, 1H; J6’b,6’a =11.8 Hz, J6’b,5’ =2.8 Hz, H6’b), 4.39 (d, 1H; J1’a,1’b
=
À1 [53]
value 156.608C, DH 28.45 Jg ).
1
2.0 Hz, H1’a), 4.40 (dd, 1H; J6’a,6’b =11.8 Hz, J6’a,5’ =8.0 Hz, H6’a), 5.36 ppm
1
3
The X-ray diffraction experiments were performed by using a MAR345
diffractometer equipped with a 2D-image plate detector (CuKa radiation,
graphite monochromator, l=1.54 Š). The samples were heated in the
presence of a magnetic field (Bꢀ1 T) by using a home-built capillary fur-
nace. The diffraction patterns showthe intensity as a function of the
modulus of the scattering wave vector (q). The correlation length was de-
termined by using ORIGIN in conjunction with MARR software. These
programmes allowdeconvolution of the X-ray peaks and, therefore, de-
termination of the peak width at half the peak height, which can be com-
pared to the peak width of the X-ray beam. The differences were used to
determine the correlation length, and the data could then be fitted to a
Gaussian or Lorentzian function. Molecular lengths were determined by
using either Dreiding molecular models or computer simulations by using
an Apple MacIntosh G4 computer and ChemDraw3D as part of a Chem-
Draw Ultra6.0 program.
1 3
(d, 1H; J1,2 =3.8 Hz, H ); C NMR (125 MHz, MeOD): d=14.7 (2CH ),
26.3, 26.4 (2CH2b), 24.0, 30.5, 30.7, 30.8, 30.9, 31.0, 31.1, 33.4, 33.4
(20CH ), 35.3 (2CH ), 62.8 (C ), 63.8 (C ), 67.0 (C ), 71.8 (C ), 73.4
2
2a
6
1’
6’
4
(C ), 74.6 (C ), 75.0 (C ), 76.4 (C ), 78.7 (C ), 81.1 (C ), 94.3 (C ), 104.6
2
5
3
4’
3’
5’
1
(C ), 174.9 (1C=O on 1’), 175.7 ppm (1C=O on 6’); HRMS: m/z: calcd
2’
+
for C H O Na: 785.5027; found: 785.5040 [M+Na] ; elemental analysis
4
0
74 13
calcd (%) for C H O ·1.9H O: C 60.26, H 9.84; found: C 60.21, H 9.43.
4
0
74 13
2
1
’-O-Lauroyl-6’-O-dodec-5c-enoylsucrose 1c: [a]
D
=+35 (c=0.3, THF);
), 1.23–1.43 (m,
12), 1.61–1.74 (m, 4H; 2CH2b), 2.01–2.16 (m, 4H; CH CH=
), 2.34–2.43 (m, 4H; 2CH2a), 3.36 (t + MeOD, 1H; J4,3 =J4,5
), 3.42 (dd, 1H; J2,3 =9.7 Hz, J2,1 =3.9 Hz, H ), 3.69 (t, 1H;
3,4 =J3,2 =9.7 Hz, H ), 3.73 (dd, 1H; J6b,6a =11.7 Hz, J6b,5 =4.7 Hz, H6b),
.80–3.87 (m, 2H; H6a, H
1
H NMR (500 MHz, MeOD): d=0.88–0.98 (m, 6H; 2CH
2
CHCH
9
3
4H; (CH
2
)
2
2
=
.7 Hz, H
4
2
J
3
3
3
8
5
), 3.90 (td, 1H; J5’,4’ =J5’,6’a =8.0 Hz, J5’,6’b
=
=
=
.0 Hz, H5’), 4.03 (t, 1H; J4’,3’ =J4’,5’ =8.0 Hz, H4’), 4.08 (d, 1H; J3’,4’
.0 Hz, H3’), 4.12 (d, 1H; J1’b,1’a =12.0 Hz, H1’b), 4.33 (dd, 1H; J6’b,6’a
Synthetic methods for sucrose diesters
Chemicals: Sucrose was obtained from BØghin-Say. Reactants were pur-
chased from Aldrich and TCI (vinylic esters). Chromatography solvents
were purchased from SDS and Carlo Erba. HPLC solvents were pur-
chased from SDS. The enzymes were gifts from Novozyme.
11.8 Hz, J6’b,5’ =3.0 Hz, H6’b), 4.39 (d, 1H; J1’a,1’b =12.0 Hz, H1’a), 4.41 (dd,
1H; J6 =11.8 Hz, J6’a,5’ =8.0 Hz, H6’a), 5.31, 5.48 ppm (m, 3H; H1, CH=
’a,6’b
1
3
CH); C NMR (125 MHz, MeOD): d=14.8 (2CH ), 26.3, 26.4 (2CH ),
3
2b
2
7.8, 28.5 (2CH2aCH=CH), 24.0, 30.4, 30.5, 30.8, 30.8, 31.0, 31.1, 31.1,
33.3, 33.4 (12CH ), 34.6, 35.3 (2CH2a), 62.7 (C ), 63.7 (C1’), 67.0 (C6’),
71.8 (C ), 73.3 (C ), 74.6 (C ), 74.9 (C ), 76.3 (C4’), 78.6 (C3’), 81.1 (C5’),
94.3 (C ), 104.5 (C2’), 129.9, 132.3 (CH=CH), 174.9 (1C=O on 1’),
Enzymatically synthesized sucrose 1’,6’-diesters 1a–d (Scheme 1): 1’,6’-
2
6
[
47]
Diesters were synthesized as described, by transesterification of pure
’-monoester (obtained as in refs. [48–51]) with the desired trifluoroethyl
4
2
5
3
1
1
Chem. Eur. J. 2007, 13, 1763 – 1775
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1765

J. W. Goodby, Y. Queneau et al.
1
75.6 ppm (1C=O on 6’); HRMS: m/z: calcd for C36
H
64
O
13Li: 711.4507;
Mixtures of 6,6’- and 1’,6-diesters 3a, 3b, and 4a
+
found: 711.4509 [M+Li] .
Monolauroyl sucrose (mixture of isomers, 6/1’/6’: 40:10:33, 1.00 g,
1
’-O-Palmitoyl-6’-O-hexadec-9c-enoylsucrose 1d: [a]
D
=+17 (c=0.6,
), 1.14–
20), 1.57–1.73 (m, 4H; 2CH2b), 2.12–2.98 (m, 4H;
), 2.29–2.45 (m, 4H; 2CH2a), 3.36 (dd + MeOD, 1H;
4,3 =9.1 Hz, J4,5 =9.8 Hz, H ), 3.42 (dd, 1H; J2,3 =9.7 Hz, J2,1 =3.8 Hz,
), 3.69 (dd, 1H; J3,4 =9.1 Hz, J3,2 =9.7 Hz, H ), 3.73 (dd, 1H; J6b,6a
2.0 Hz, J6b,5 =5.0 Hz, H6b), 3.80–3.87 (m, 2H; H6a, H ), 3.90 (td, 1H;
5’,4’ =J5’,6’a =8.2 Hz, J5’,6’b =3.2 Hz, H5’), 4.03 (t, 1H; J4’,3’ =J4’,5’ =8.2 Hz,
4’), 4.08 (d, 1H; J3’,4’ =8.2 Hz, H3’), 4.12 (d, 1H; J1’b,1’a =12.3 Hz, H1’b),
1.9 mmol) was dissolved in anhydrous DMF (20 mL) under N at RT. Tri-
phenylphosphine (1.26 g, 2.5 equiv) and carboxylic acid (dodec-5c-enoic
2
1
THF); H NMR (500 MHz, MeOD): d=0.85–0.98 (m, 6H; 2CH
.50 (m, 40H; (CH
CH CH=CHCH
3
1
2
)
acid, 0.84 mL, 2 equiv) were added. After complete dissolution, the
medium was cooled to 08C and DIAD (0.94 mL, 2.5 equiv) was added.
TLC showed the formation of less-polar products without total consump-
tion of monolauroyl sucrose. After 17 h at RT, DMF was removed under
reduced pressure at T=36–388C and the crude residue was subjected to
2
2
J
H
1
J
4
2
3
=
5
chromatography on
a silica-gel column (elution gradient: dichloro-
H
ACHTREUNG
methane/acetone/methanol/water 78:10:10:1.5–67:15:15:3 v/v). The main
4
1
5
.33 (dd, 1H; J6’b,6’a =11.8 Hz, J6’b,5’ =3.2 Hz, H6’b), 4.39 (d, 1H; J1’a,1’b
=
mixed diester was collected (R =0.49 in the 67:15:15:3 v/v eluent, the
mixed 6,6’-diester, 453 mg, 34%) together with a second mixed diester
f
2.3 Hz, H1’a), 4.41 (dd, 1H; J6’a,6’b =11.8 Hz, J6’a,5’ =8.2 Hz, H6’a), 5.31–
1
3
.44 ppm (m, 3H; H1, CH=CH); C NMR (125 MHz, MeOD): d=14.8
), 26.3, 26.4 (2CH2b), 28.4, 28.5 (2CH2aCH=CH), 24.0, 30.4, 30.5,
0.6, 30.8, 31.0, 31.1, 33.2, 33.4 (20CH ), 35.3, 35.3 (2CH2a), 62.8 (C ),
), 74.6 (C ), 74.9 (C ), 76.4 (C4’),
), 104.6 (C2’), 131.1, 131.2 (CH=CH), 174.9
(R =0.60 in the 67:15:15:3 v/v eluent, 1’-O-dodec-5c-enoyl-6-O-lauroyl-
f
(
2CH
3
sucrose, 94 mg, 7%). These were subjected further to semipreparative
3
6
7
2
6
HPLC on a NH2 spherisorb column, 20”250 mm (injection loop: 2 mL,
À1
3.7 (C1’), 67.0 (C6’), 71.8 (C
8.7 (C3’), 81.1 (C5’), 94.3 (C
4
), 73.4 (C
2
5
3
flow: 20 mLmin ) by using a CH CN/THF/water 40:54:6 v/v eluent to
3
1
give the pure mixed diesters.
(
C
1C=O on 1’), 175.7 ppm (1C=O on 6’); HRMS: m/z: calcd for
In the mixed 6,6’-diester, the relative positions of the chains on OH-6
and OH-6’ could not be ascertained, thus, 3a and 3b should be consid-
ered as mixtures of compounds (3a=6C –6’C + 6C –6’C and 3b=
+
44
H
80
O
13Li: 823.5759; found: 823.5766 [M+Li] .
Sucrose 6,6’-diesters 2a–h, 3a,b, and 4a synthesized through the Mitsuno-
bu reaction (Scheme 2)
1
2
16
16
12
[
44]
1
2
12:1 12
6C –6’C + 6C12:1–6’C ).
Homogeneous 6,6’-diesters 2a–h
6-O-Palmitoyl-6’-O-lauroylsucrose and 6-O-lauroyl-6’-O-palmitoylsucrose
1
Sucrose (3.42 g, 10.0 mmol) was dissolved in anhydrous DMF (79 mL) by
3a: [a]
d=0.77–0.95 (m, 6H; 2CH
4H; 2CH2b), 2.25–2.43 (m, 4H; 2CH2a), 3.26 (dd, 1H; J4,3 =9.0 Hz, J4,5
10.0 Hz, H ), 3.46 (dd, 1H; J2,3 =9.6 Hz, J2,1 =3.7 Hz, H ), 3.57 (d, 1H;
1’b,1’a =12.4 Hz, H1’b), 3.66 (d, 1H; J1’a,1’b =12.4 Hz, H1’a), 3.76 (dd, 1H;
3,4 =9.0 Hz, J3,2 =9.6 Hz, H ), 3.88–4.08 (m, 4H; H , H3’, H4’, H5’), 4.17
D
=+41 (c=1, THF); H NMR (300 MHz, MeOD/CDCl
3
25:75):
stirring under N
of triphenylphosphine (7.06 g, 2.7 equiv), carboxylic acid (lauric acid,
.00 g, 2.5 equiv), and more DMF (21 mL). After complete dissolution,
the medium was cooled to 08C and diisopropyl azodicarboxylate
DIAD) (5.3 mL, 2.7 equiv) was added. TLC showed nearly total con-
2
at 708C. The mixture was cooled to RT before addition
3
), 1.15–1.40 (m, 40H; (CH 20), 1.50–1.67 (m,
2
)
=
5
4
2
J
J
(
3
5
sumption of sucrose after 26 h at RT. After removal of DMF under re-
duced pressure at T=36–388C, the crude residue was subjected to chro-
matography on a silica-gel column (elution gradient: dichloromethane/
acetone/methanol/water 78:10:10:1.5–67:15:15:3 v/v). The diester fraction
(dd, 1H; J6b,6a =11.8 Hz, J6b,5 =5.9 Hz, H6b), 4.23–4.45 (m, 3H; H6a, H6’a/b),
1
3
5.36 ppm (d, 1H; J1,2 =3.7 Hz, H
(2CH ), 25.6 (2CH2b), 23.4, 29.9, 30.1, 30.3, 30.4, 32.7 (20CH
(2CH2a), 64.3 (C1’), 64.7 (C ), 66.6 (C6’), 71.2 (C ), 71.4 (C
74.1 (C ), 76.6 (C4’), 79.7 (C3’), 80.3 (C5’), 92.6 (C ), 104.6 (C2’), 175.0
(1C=O on 6’), 175.4 ppm (1C=O on 6); HRMS: m/z: calcd for
1
); C NMR (75 MHz, MeOD): d=14.6
), 34.7, 34.8
), 72.6 (C ),
3
2
6
4
5
2
(
containing anhydroderivatives as side products) was collected (1.30 g,
3
1
1
8%) and subjected further to semipreparative HPLC on a NH
2
Spheri-
À1
+
sorb column, 20”250 mm (injection loop: 2 mL, flow: 20 mLmin ), by
C
40
H
74
O
13Na: 785.5027; found: 785.5023 [M+Na] ; elemental analysis
calcd (%) for C40 13·0.7H O: C 61.94, H 9.80, O 28.26; found: C
61.88, H 9.79, O 28.06.
6-O-Dodec-5c-enoyl-6’-O-lauroylsucrose and 6-O-lauroyl-6’-O-dodec-5c-
using a CH
ster (6,6’-di-O-lauroyl sucrose, 15%).
,6’-Di-O-lauroylsucrose 2c: [a] =+45 (c=1, THF); ref. [47]; H NMR
300 MHz, MeOD): d=0.80–1.00 (m, 6H; 2CH ), 1.15–1.45 (m, 32H; 2
(CH ), 1.50–1.70 (m, 4H; 2CH2b), 2.25–2.45 (m, 4H; 2CH2a), 3.23 (t,
H; J4,3 =J4,5 =9.4 Hz, H ), 3.41 (dd, 1H; J2,3 =9.4 Hz, J2,1 =3.7 Hz, H ),
.56 (d, 1H; J1’b,1’a =12.8 Hz, H1’b), 3.62 (d, 1H; J1’a,1’b =12.8 Hz, H1’a), 3.70
), 3.86–4.15 (m, 5H; H6b, H3’, H , H4’, H5’),
.30–4.40 (m, 2H; H6’a/b), 4.44 (dd, 1H; J6a,6b =10.9 Hz, J6a,5 ~0, H6a),
3
CN/THF/water 40:54:6 v/v mixture, leading to pure 6,6’-die-
H
74
O
2
1
6
D
1
(
3
enoylsucrose 3b: [a]
d=0.88–0.97 (m, 6H; 2CH
4H; 2CH2b), 2.01–2.16 (m, 4H; CH
2CH2a), 3.27 (dd, 1H; J4,3 =9.1 Hz, J4,5 =9.8 Hz, H
9.5 Hz, J2,1 =3.9 Hz, H
1’a,1’b =12.3 Hz, H1’a), 3.74 (dd, 1H; J3,4 =9.1 Hz, J3,2 =9.5 Hz, H
3.92 (m, 1H; H5’), 4.03 (t, 1H; J4’,3’ =J4’,5’ =8.2 Hz, H4’), 4.16–4.05 (m, 3H;
6b, H3’, H ), 4.42–4.35 (m, 2H; H6’a/b), 4.47 (dd, 1H; J6a,6b =11.7 Hz,
6a,5 =1.6 Hz, H6a), 5.39 ppm (m, 3H; H1, CH=CH); C NMR (125 MHz,
MeOD): d=14.8 (2CH ), 26.3 (2CH2b), 28.5, 27.8 (2CH2aCH=CH), 24.0,
30.4, 30.5, 30.8, 30.9, 31.0, 31.1, 33.2, 33.4 (12CH ), 34.6, 35.2 (2CH2a),
64.3 (C1’), 65.5 (C ), 67.2 (C6’), 72.1 (C , C ), 73.4 (C ), 74.8 (C ), 77.1
(C4’), 79.2 (C3’), 81.0 (C5’), 93.4 (C ), 105.6 (C2’), 130.0, 131.2 (CH=CH),
175.4 (1C=O on 6’), 175.6 ppm (1C=O on 6); HRMS: m/z: calcd for
D
=+44 (c=6, THF); H NMR (500 MHz, MeOD):
), 1.25–1.42 (m, 24H; (CH 12), 1.58–1.75 (m,
), 2.32–2.49 (m, 4H;
), 3.45 (dd, 1H; J2,3
A
C
H
T
R
E
U
N
G
2
)
8
3
2
)
1
3
4
2
2
CH=CHCH
2
4
=
(
t, 1H; J3,4 =J3,2 =9.4 Hz, H
3
5
2
), 3.61 (d, 1H; J1’b,1’a =12.3 Hz, H1’b), 3.65 (d, 1H;
), 3.98–
4
5
J
3
1
3
.33 ppm (d, 1H; J1,2 =3.7 Hz, H
), 26.3 (2CH2b), 24.1, 30.5, 30.8, 31.0, 31.1, 33.4 (16CH
2CH2a), 64.3 (C1’), 65.5 (C ), 67.2 (C6’), 72.2 (C , C ), 73.5 (C ), 74.9 (C
7.1 (C4’), 79.2 (C3’), 81.0 (C5’), 93.5 (C ), 105.6 (C2’), 175.4 (1C=O on 6’),
75.8 ppm (1C=O on 6); HRMS: m/z: calcd for C36 13Na: 729.4401;
1
); C NMR (75 MHz, MeOD): d=14.8
), 35.2
),
(
2CH
3
2
H
J
5
1
3
(
7
1
6
5
4
2
3
1
3
H
66
O
2
+
found: 729.4400 [M+Na] ; elemental analysis calcd (%) for C36
H
66
O
13: C
6
5
4
2
3
6
1.17, H 9.41, O 29.42; found: C 61.16, H 9.31, 28.96.
,6’-Di-O-stearoylsucrose 2e: [a]
/MeOD 2/1): d=0.89 (m, 6H; 2CH
14), 1.62 (m, 4H; 2CH2b), 2.35 (m, 4H; 2CH2a), 3.27 (t + MeOD,
H; J4,3 =J4,5 =9.4 Hz, H ), 3.46 (dd, 1H; J2,1 =3.7 Hz, J2,3 =10.0 Hz, H ),
.59 (d, 1H; J1’b,1’a =12.2 Hz, H1’b), 3.66 (d, 1H; J1’a,1’b =12.6 Hz, H1’a), 3.72
), 3.88–4.10 (m, 4H; H5’; t, J4’,3’ =J4’,5’ =7.6 Hz,
, H3’), 4.15 (dd, 1H; J6b,6a =11.8 Hz, J6b,5 =6.1 Hz, H6b), 4.36 (m,
1
1
6
D
=+39 (c=0.4, THF); H NMR
+
C
30
H
54
O
11Na: 727.4245; found: 727.4248 [M+Na] ; elemental analysis
calcd (%) for C36 13·0.9H O: C 59.96, H 9.20; found: C 59.95, H 9.13.
1’-O-Dodec-5c-enoyl-6-O-lauroylsucrose 4a: [a] =+31 (c=0.4, THF);
H NMR (500 MHz, MeOD): d=0.80–1.00 (m, 6H; 2CH ), 1.20–1.50 (m,
24H; (CH 12), 1.55–1.75 (m, 4H; 2CH2b), 2.00–2.20 (m, 4H; CH CH=
CHCH ), 2.30–2.50 (m, 4H; 2CH2a), 3.31 (dd MeOD, 1H; J4,3
9.4 Hz, J4,5 nd, H ), 3.42 (dd, 1H; J2,3 =9.8 Hz, J2,1 =3.8 Hz, H ), 3.68 (dd,
1H; J3,4 =9.4 Hz, J3,2 =9.8 Hz, H ), 3.73–3.85 (m, 3H; H6’a/b, H5’), 4.00–
4.08 (m, 2H; H , H4’), 4.09 (d, 1H; J3’,4’ =8.5 Hz, H3’), 4.14 (d, 1H; J1’b,1’a
(
300 MHz, CDCl
3
3
), 1.28 (m, 56H; 2
H
64
O
2
A
C
H
T
R
E
U
N
G
(CH
2
)
1
3
4
2
D
1
3
(
t, 1H; J3,4 =J3,2 =9.3 Hz, H
3
2
)
2
H
4’, H
5
2
+
=
2
H; H6’a/b), 4.44 (dd, 1H; J6a,6b =11.3 Hz, J6a,5 <1, H6a), 5.36 ppm (d, 1H;
4
2
1
3
J
1,2 =3.8 Hz, H
1
); C NMR (75 MHz, MeOD/CDCl
), 25.4 (2CH2b), 23.2, 29.7, 29.8, 30.0, 30.2, 32.4 (28CH
), 66.2 (C6’), 71.1 (C ), 71.4 (C
), 76.8 (C4’), 80.1 (C3’), 80.3 (C5’), 92.5 (C
74.7 (1C=O on 6’), 175.1 ppm (1C=O on 6); HRMS: m/z: calcd for
3
(4:1 v/v) at 508C):
3
d=14.4 (2CH
3
2
),
),
5
=
3
7
1
4.6, 34.7 (2CH2a), 64.4 (C1’), 64.5 (C
2.4 (C ), 74.2 (C
6
4
5
12.0 Hz, H1’b), 4.19 (dd, 1H; J6b,6a =11.8 Hz, J6b,5 =5.5 Hz, H6b), 4.38 (d,
1H; J1’a,b =12.0 Hz, H1’a), 4.43 (dd, 1H; J6a,6b =11.8 Hz, J6a,5 =1.9 Hz, H6a),
2
3
1
), 104.7 (C2’),
1
3
5.41 ppm (m, 3H; H
(2CH ), 26.3 (2CH2b), 27.8, 28.5 (2CH2aCH=CH), 24.0, 30.4, 30.5, 30.7,
30.8, 30.9, 31.0, 31.1, 33.3, 33.4 (12CH ), 34.6, 35.3 (2CH2a), 64.0 (C1’
6’), 65.0 (C ), 72.0 (C ), 72.3 (C ), 73.3 (C ), 74.7 (C ), 75.6 (C4’), 79.0
1
, CH=CH); C NMR (125 MHz, MeOD): d=14.7
+
C
48
H
90
O
13Na: 897.6279; found: 897.6271 [M+Na] ; elemental analysis
calcd (%) for C48 13: C 65.87, H 10.36, O 23.76; found: C 65.51, H
0.51, O 23.26.
3
H
90
O
2
,
1
C
6
4
5
2
3
1766
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Chem. Eur. J. 2007, 13, 1763 – 1775

Disubstituted Sucrose Esters
FULL PAPER
(
C
3’), 84.3 (C5’), 94.3 (C
1
), 104.4 (C2’), 129.9, 132.3 (CH=CH), 175.0 (1C=
that coalesced to form various defect patterns. Typically
focal-conic defects possessing elliptical and hyperbolic opti-
cal discontinuities were formed, together with homeotropic
textures. Oily streaks associated with edge dislocations were
also observed, and fanlike defect fringes were found to form
around air bubbles. These features are diagnostic for the
presence of the smectic A phase, and are indicated by the
white arrows in Figure 1a. Furthermore, the presence of ho-
meotropic defect textures (Figure 1b) unequivocally demon-
strates that there are no tilted smectic phases present for
these materials.
O on 1’), 175.7 ppm (1C=O on 6); HRMS: m/z: calcd for C30
7
54
H O11Na:
+
27.4245; found: 727.4245 [M+Na] .
Results and Discussion
The results are detailed in two sections, depending on the
incorporation or not of unsaturations in the aliphatic chains.
In Section 1, we describe the thermotropic behavior and the
structural features of the saturated fatty-acid derivatives,
and in particular we examine the nature of the clearing
points and the packing of the molecules in the lamellar
phases.
1. Saturated fatty-acid diesters
Classification of the mesophases formed by the compounds
a, 1b, 2a–2e, and 3a by optical microscopy, differential
1
scanning calorimetry (DSC), and X-ray diffraction:
Polarizing optical microscopy (POM): Table 1 summarizes
the transition temperatures, determined on heating, for the
saturated diesters. The lengths and positions of attachment
of the aliphatic chains markedly affect the transition temper-
atures. For example, compare the transition temperatures of
compounds 1a and 2c. There is approximately a 508C differ-
ence in the clearing points, possibly because 2c has a more
linear structure than 1a. Thus, the relative stereochemistries
of the materials appear to be important with respect to
mesophase thermal stability.
A
C
H
T
R
E
U
N
G
Examination of the microscopic defect textures of the ma-
terials showed that all of the compounds exhibited lamellar
smectic A phases (see, for example, Figure 1). Under
crossed polars (x100), and upon cooling from the isotropic
liquid, the mesophases separated in the form of bâtonnets
Figure 1. Defect textures of the smectic A phase of 6,6’-di-O-octanoylsu-
crose, 2a, (x100); a) the oily streak texture and fanlike defects around air
bubbles, b) the focal-conic defect and homeotropic textures.
Table 1. Transition temperatures of the saturated fatty-acid sucrose diesters determined by thermal polarizing
light microscopy as a function of aliphatic chain lengths.
If the clearing-point tempera-
tures for the 2a–e family of
compounds are evaluated as a
function of chain length, it can
be shown that the liquid-crystal
mesophase is stabilized as the
two aliphatic chains are length-
ened up to the dodecanoyl ho-
mologues. This behavior is typi-
cal of most glycolipids; howev-
er, as the chain length is in-
creased further, there is a drop
in the clearing points followed
by a further rise in temperature.
Compound structure
Chain length
Compound
Transition temperature [8C]
m=n=10
m=10, n=14
1a
1b
cryst. 42.1 smectic A 120 iso. liq.
cryst. ~30 smectic A 115.9 iso. liq.
m=n=6
m=n=8
[
a]
2
2
2
2
2
3
a
b
c
d
e
a
soft solid–smectic A 146.3 iso. liq.
cryst.~90 smectic A 163.0 iso. liq.
cryst. 87.3 smectic A 170.8 iso. liq.
m=n=10
m=n=14
m=n=16
m=10, n=14+
m=14, n=10
cryst. 106.6 smectic A 167.8 iso. liq. The drop cannot be attributed
cryst. 109.7 smectic A 164.3 iso. liq.
cryst. 84.7 smectic A 167.8 iso. liq.
to impurities associated with
the dihexadecanoyl homologue,
as the materials in the series
have similar purity levels, and
[
a] The melting point could not be determined by microscopy or DSC.
Chem. Eur. J. 2007, 13, 1763 – 1775
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www.chemeurj.org
1767

J. W. Goodby, Y. Queneau et al.
the transitions from the liquid crystal to the liquid states are
sharp in all cases. The details in respect of the depression in
the clearing points as a function of chain length were inves-
tigated further by X-ray diffraction, the results for which
will be described in the subsequent Section.
Notably, the classification of the mesophase is smectic A,
however, as the materials are chiral, the environmental sym-
metry of the phase is reduced from D8h to D , and as a con-
8
sequence, the mesophase should exhibit electroclinic proper-
ties. Thus, by symmetry, the mesophases should be classified
as SmA*.
Differential scanning calorimetry (DSC): Results of DSC
confirmed the transition temperatures obtained from polar-
izing light microscopy. Table 2 lists the enthalpy and entropy
Figure 2. Radially integrated diffraction pattern of 6,6’-di-O-octanoylsu-
crose, 2a, over a temperature range of 30–608C. Diffraction intensities
are given on a logarithmic scale.
Table 2. Enthalpies, DH, and entropies, DS, for the clearing-point transi-
Table 3. Distances (d) related to the Miller indices for the radially inte-
tions of the saturated fatty-acid esters.
grated diffraction pattern of 6,6’-di-O-octanoylsucrose, 2a, at 508C.
À1
Compd
DH
DS
[mJg
Compd
DH
DS
[mJg K ]
Miller index
q [nm
]
d [Š]
Ratio
À1
À1 À1
À1
À1 À1
A
C
H
T
R
E
U
N
G
[Jg
]
K
]
A
H
R
U
G
]
0
01
2.20
4.39
6.63
28.6
14.3
9.5
7.1
4.5
1
2
2
2
a
b
c
5.731
4.373
3.07
13.7
10.0
6.9
2d
2e
3a
1.633
1.147
1.972
3.7
2.6
4.5
002
003
004
alkyl
1/2
1/3
1/4
–
[
a]
8.82
13.9
[
a] Weak reflection.
values as a function of chain length for the 6,6’-esters. A
progressive decrease in the enthalpies for the clearing points
was a function of increasing saturated fatty-acid chain
length. A similar change in the entropy for this transition
shows that the smectic A phase becomes more disordered
and liquidlike as the fatty-acid chain increases in length.
The rate of decrease in the enthalpy and entropy as a func-
tion of chain length, per methylene unit, appears to be
linear up to the dodecanoyl homologue (m=n=10), at
which point the rate of change falls off more sharply.
perature range of the mesophase, the (003) and (004) reflec-
tions occur at lower temperatures, indicating that the layers
become better defined as the temperature is lowered.
The temperature dependence of the layer spacing d001 and
the correlation length x001 are presented together in
Figure 3. A large, but characteristic, temperature depen-
A
H
R
U
G
X-ray diffraction studies: X-ray diffraction studies were per-
formed on compounds 1b, 2a, 2d, 2e, and 3a over a wide
temperature range in the liquid-crystal phase. The results
obtained for selected members 2a, 2d, and 2e are described
first.
6,6’-Di-O-octanoylsucrose (2a): Figure 2 shows the diffrac-
tion intensity for 2a as a function of scattering vector, q,
and temperature. The diffraction data taken at a tempera-
ture of 508C are summarized in Table 3, and showthat the
mesophase formed is a lamellar smectic phase. The (001) re-
flection gives a layer spacing of 28.1 Š, which is similar to
the calculated molecular length of 28.2 Š. Coupling this
result with those from optical microscopy confirms that the
mesophase is smectic A with the molecules arranged orthog-
onal to the layer planes. Interestingly, the presence of the
fourth-order reflection indicates that the layers are relatively
well defined, rather than diffuse. Apart from the (001) re-
flection, all of the other reflections are relatively weak, with
the (003) reflection being slightly weaker than the (004). In
addition, although the (002) reflection is seen over the tem-
Figure 3. Temperature dependence of d001 and x001 for 6,6’-di-O-octanoyl-
sucrose, 2a.
linear increase in the layer spacing of approximately 2 Š
was observed over a 1008C temperature range (~7.5%
change). Conversely, the correlation length remained rela-
tively constant over the same temperature range.
6,6’-Di-O-hexadecanoylsucrose (2d): Figure 4 shows the dif-
fraction intensity as a function of q and the temperature for
1768
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Chem. Eur. J. 2007, 13, 1763 – 1775

Disubstituted Sucrose Esters
FULL PAPER
Figure 5. Temperature dependence of d001 and x001 for 6,6’-di-O-hexadeca-
noylsucrose, 2d.
Figure 4. Radially integrated diffraction pattern of 6,6’-di-O-hexadeca-
noylsucrose, 2d, over a temperature range of 30–1808C. Diffraction in-
tensities are given on a logarithmic scale.
6
,6’-O-Di-octadecanoylsucrose (2e): The diffraction intensity
compound 2d. The wide-angle reflection is very diffuse
throughout the temperature range of the smectic phase and
only becomes sharper in the crystal phase. The (001) value
of 44.9 Š at 508C (the lowest temperature at which the
smectic phase can exist) is slightly shorter than the calculat-
ed molecular length of 49.7 Š, and, thus, with the observa-
tions made by polarizing light microscopy, the phase is con-
firmed as smectic A. A (002) reflection is visible upon cool-
ing from 1458C, and a very weak (003) reflection is ob-
served at temperatures below80 8C. There is an indication
that a (004) reflection is present, but it is very weak and is
lost partly in the noise. Thus, the layers for 2d are much-less
well defined than those for 2a. This suggests that the longer
hexadecyl chains in 2d are having a disordering effect due
to their increased flexibility relative to the octyl chain of 2a.
The diffraction data at 508C are summarized in Table 4. The
compiled data as a function of temperature are shown in
Figure 5.
(using a logarithmic scale) as a function of the scattering
wave vector q and temperature is shown in Figure 6 for
Figure 6. Radially integrated diffraction pattern of 6,6’-di-O-octadeca-
noylsucrose, 2e, over a temperature range of 40–2008C. Diffraction in-
tensities are given on a logarithmic scale.
Table 4. Distances (d) related to the Miller indices for the radially inte-
grated diffraction pattern of 6,6’-di-O-hexadecanoylsucrose, 2d, at 508C.
compound 2e. Surprisingly, in contrast to the other materials
studied, an intense small-angle reflection is observed in the
isotropic phase, as shown by the light-grey curves in the
figure, which indicates pretransitional effects occurring in
the liquid. Upon cooling down into the smectic A phase
À1
Miller index
q [nm
]
d [Š]
Ratio
0
0
0
01
02
03
1.40
2.78
4.19
13.6
44.9
22.6
15.0
4.6
1
1/2
1/3
–
(
dark lines), the second-order reflection (002) can also be
alkyl
seen, which grows more intense as the temperature falls. At
higher temperatures the fundamental (001) reflection is best
fitted by a Lorentzian distribution function, taken from the
peak width at half the peak height, indicating short-range
positional order. At lower temperatures (T<1008C), the
shape of the reflection changes to a Gaussian distribution
function, indicating the presence of longer range positional
order. Within this temperature range, third- and fourth-
order reflections are also observed, indicating that the layers
become better defined. The change in shape of the diffrac-
tion patterns for the fundamental reflections at T=1058C
(Lorentzian) and T=958C (Gaussian) are illustrated togeth-
er in Figure 7. Note the difference in the shape of the
curves, particularly at the “wings” of the reflections. Further
cooling of the sample results in crystallization.
The temperature dependence of the layer spacing d001 and
the correlation length x001 are shown together in Figure 5. A
strong temperature dependence of the layer spacing is ob-
served for the smectic phase, with the d values ranging from
3
5 to 45 Š. Thus, over a temperature range of 1258C the
layer spacing of the smectic A varies by approximately 20–
5%; therefore, the behavior of this smectic A phase is very
2
different from the smectic A phase of compound 2a. Crys-
tallization is observed between 50 and 608C, at which d001
and x001 become virtually temperature independent. At the
transition from the smectic A phase to the isotropic liquid,
the correlation length collapses, as would be expected.
Chem. Eur. J. 2007, 13, 1763 – 1775
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1769

J. W. Goodby, Y. Queneau et al.
fourth-order reflection at 808C shows that the layers in the
smectic phase are well defined.
At lowtemperatures the layer spacing approaches 48 Š,
molecular modeling using ChemDraw3D Ultra gives the
length of the minimized, extended molecular conformation
of 54.8 Š, and Dreiding Molecular Models give a value of
5
3
6 Š. At high temperatures the layer spacing approaches
6 Š, whereas modeling of the folded molecular conforma-
tion gives a value of 31.6 Š, and Dreiding Models a value of
9.7 Š. Figure 9 shows the ChemDraw-modeled fully ex-
2
tended and folded structures.
Figure 7. Lorentzian and Gaussian fits to the diffraction data at tempera-
tures of 105 and 958C, respectively, for compound 2e.
A strong temperature dependence of the layer spacing is
also observed in the smectic phase, with the d values ranging
Figure 9. The fully extended structure (top), and the folded structure
(
bottom) for 6,6’-di-O-octadecanoylsucrose, 2e (oxygen dark-grey,
carbon mid-grey, hydrogen white).
One explanation for the transition in the smectic A phase
is that the molecules are interdigitated at high temperature,
and the extent of the interdigitation reduces as the tempera-
ture decreases as the phase becomes more ordered
(
Figure 10, top). Thus, it appears from the d-spacing meas-
urements that there is a continuous transformation from an
[54]
Figure 8. Temperature dependence of d001 and x001 for 6,6’-di-O-octadeca-
noylsucrose, 2e.
intercalated SmA to a nonintercalated SmA
structuring
c
1
of the layers. The transformation from the intercalated to
the nonintercalated may be related to the change from
Gaussian to Lorentzian line shape associated with the corre-
lation length.
from 35 to 50 Š; see Figure 8. Remarkably, the d spacing
changes continuously in the smectic phase and into the iso-
tropic liquid. Crystallization is observed between 70 and
An alternative explanation could be that molecules have
folded conformations, and at high temperatures the folded
molecules pack in interdigitated bilayers, that is, as in the
758C, at which d001 and x001 become virtually temperature in-
[55,56]
dependent. As the peak shape changes from Gaussian to
Lorentzian (T=1008C), a local minimum in the correlation
length (half-width of the reflection) is observed, which
marks a change in the form/structure of the smectic A
phase. Table 5 shows a “snap-shot” of the d spacings taken
at two temperatures, above and below this change. The
SmA phase.
As the temperature is lowered the interdi-
d
gitation is reduced and eventually the phase has only weak
[54,55]
interdigitation, as in the SmA2 phase
(Figure 10,
bottom). The changeover from one form of smectic A phase
to the other may not be detected from the X-ray layer spac-
ings, but it is possible that such a transition might be seen
through examination of the correlation length.
The change in the correlation length is also associated
with an increase in the number of reflections seen in the
radial scans. At high temperatures only the first- and
second-order reflections are seen, whereas at low tempera-
tures the number of reflections increases to the fourth re-
flection. This suggests that the layers are becoming better
defined at lower temperatures in the smectic A phase. The
increased layer definition may be a result of the sugar units
packing more strongly together due to extensive hydrogen-
bonding interactions. The second model is probably more
Table 5. X-ray data taken at two different temperatures in the smectic A
phase of 6,6’-di-O-octadecanoylsucrose, 2e.
À1
T [8C]
Miller index
q [nm
]
d [Š]
Ratio
8
1
0
001
1.32
2.64
3.98
5.27
1.53
3.04
47.4
23.8
15.8
11.9
41.1
20.7
1
0
0
0
02
03
04
1/2
1/3
1/4
1
10
001
02
0
1/2
1770
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Chem. Eur. J. 2007, 13, 1763 – 1775

Disubstituted Sucrose Esters
FULL PAPER
Figure 11. Radially integrated diffraction pattern of 1’-O-dodecanoyl-6’-
O-hexadecanoylsucrose, 1b, over a temperature range of 30–1608C. Dif-
fraction intensities are given on a logarithmic scale. The light-grey lines
are within the liquid state and the dark lines are within the smectic A
phase.
Table 6. Distances (d) related to the Miller indices for the radially inte-
grated diffraction pattern of 1’-O-dodecanoyl-6’-O-hexadecanoylsucrose,
1
b, at 508C.
À1
Figure 10. The intercalated to nonintercalated transformation for the
fully extended molecular model (top), and the interdigitated to noninter-
digitated transformation for the folded molecular model (bottom) for 2e.
For each drawing the left-hand side represents the lower-temperature
structure.
Miller index
q [nm
]
d [Š]
Ratio
0
0
01
02
1.64
3.26
13.8
38.6
19.3
4.5
1
–
–
alkyl/100
likely than the first model to give well-defined layers de-
scribed above. This is because the second arrangement
allows for flexible interactions both between and within the
layers, whereas the interlayer ordering for the first model
has a greater dependency on the interfacial interactions be-
tween the aliphatic chains.
Whichever model is applied, such a substantial change in
the layer spacing in a smectic A phase as a function of tem-
perature has not yet been observed in conventional thermo-
tropic liquid crystals, and smectic A polymorphism has not
yet been observed in sugar-based mesogens.
Materials with mixed chain lengths
Figure 12. Temperature dependence of d001 and x001 for 1’-O-dodecanoyl-
’-O-hexadecanoylsucrose, 1b.
6
1
’-O-Dodecanoyl-6’-O-hexadecanoylsucrose (1b): Figure 11
presents the diffraction intensity as a function of q and the
temperature for the mixed chain-length compound 1b, and
the diffraction data taken at 508C are summarized in
Table 6.
layer ordering into the liquid phase, hence, the liquid could
be said to be structured.
The temperature dependence of the layer spacing d001 and
the correlation length x001 are shown in Figure 12. The evo-
lution of x001 clearly indicates a phase transition between
Mixture of 6,6’-di-O-dodecanoyl-hexadecanoylsucroses (3a):
Figure 13 presents the diffraction intensity as a function of q
and temperature for the mixed system 3a. The diffraction
data taken at a temperature of 508C are summarized in
Table 7. A small (002) reflection is visible from 1458C on-
wards, and even a 004 reflection is obtained at low tempera-
tures, indicating that the layers are well defined in the smec-
tic A phase. However, the 003 reflection appears to be very
weak and almost nonexistent. The clearing-point transition
obtained between 155 and 1608C, rather than the expected
167.88C, is clearly visible from the change in shape of the
1
1
10–1208C, as observed by DSC and POM (value=
15.98C). The layer spacing shows a continuous increase as
temperature decreases, and over a temperature range of
08C it increases by 6 Š, an increase of approximately 17%.
8
Interestingly, the correlation length changes rapidly at the
transition to the liquid, however, the layer ordering is rela-
tively continuous over 158C above the phase transition.
These results suggest that there is some persistence of the
Chem. Eur. J. 2007, 13, 1763 – 1775
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1771

J. W. Goodby, Y. Queneau et al.
Figure 13. Radially integrated diffraction pattern of the mixture of 6,6’-
dodecanoyl-hexadecanoylsucroses, 3a, over a temperature range of 40–
1
808C.
Figure 15. Evolution of the layer spacing d (Š) as a function of the re-
duced temperature for the smectic A phases of the diesters 1b, 2a, 2d,
2
c
e, and 3a. T is the normalized clearing point for each material.
Table 7. Distances (d) related to the Miller indices for the radially inte-
grated diffraction pattern for the mixture of 6,6’-dodecanoyl-hexadeca-
noylsucroses, 3a, at 508C.
À1
Figure 15. This figure clearly demonstrates, for the materials
with shorter aliphatic chains, that the layer spacing is rela-
tively independent of temperature, whereas the longer chain
lengths showvery large temperature dependencies. More-
over, the temperature dependency increases as aliphatic
chain length increases (compare 2a (C8), 2d (C16), and 2e
Miller index
q [nm
]
d [Š]
Ratio
0
0
0
01
02
04
1.55
3.11
6.21
13.9
40.5
20.2
11.2
4.5
1
–
–
–
alkyl/001
(
C18)). In addition, for the longer chains the layer ordering
reflection. This change in clearing point is possible due to
slight decomposition of the sample.
Figure 14 shows the temperature dependence of the layer
spacing, d001, and the correlation length, x001. A strong de-
pendence of the layer spacing is observed throughout the
persists well into the liquid phase. Furthermore, comparison
of 1b, which has a defined substitution pattern, with the
mixed system 3a reveals a very similar temperature depen-
A
H
R
U
G
a much wider temperature range, possibly due to the disor-
dering introduced by having mixed systems.
2
. Unsaturated fatty-acid diesters
Polarizing light microscopy: Glycolipids found in nature
often possess cis unsaturations in their aliphatic chains.
Thus, to complement the study of the liquid-crystalline-satu-
rated sucrose esters, a selection of unsaturated analogues
were prepared. Table 8 summarizes the observations ob-
tained by microscopy of the phase transitions for homogene-
ous or mixed diesters with one or two chains being monoun-
saturated. The first observation to be made from the transi-
tion temperatures is that the unsaturated aliphatic materials
possess soft-crystal phases for which the phase transitions to
the liquid-crystalline state could not be determined by mi-
croscopy, and no definitive enthalpies could be observed for
the transitions by DSC.
Figure 14. Temperature dependence of d001 and x001 for the mixture of
6
,6’-dodecanoyl-hexadecanoylsucroses, 3a.
temperature range of the smectic A phase. However, a
small discontinuity in the layer spacing is observed at the
transition from the liquid-crystal phase to the liquid, thus,
the liquid of 3a appears to be structured. A much greater
discontinuity at the isotropization point is seen for the cor-
relation length; conversely, in the crystalline state the layer
spacing and the correlation length are nearly constant.
A comparison of the layer spacings as a function of tem-
perature for the materials 1b, 2a, 2d, 2e, and 3a is given in
Secondly, unlike the saturated materials, at long chain
lengths columnar phases replaced lamellar phases. For ex-
ample, compounds 1d and 2h, in which the total number of
carbon atoms in the chains ꢁ14, exhibited columnar phases,
whereas the shorter homologues 1c, 2 f, 2g, 3b, and 4a ex-
hibit smectic A phases. Compound 2g (6,6’-substitution and
two unsaturations) demonstrates that there is still some
effect of the positions of attachment of the chains and level
of unsaturation, as this material exhibits a smectic phase. In
1772
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Chem. Eur. J. 2007, 13, 1763 – 1775

Disubstituted Sucrose Esters
FULL PAPER
Table 8. Transition temperatures determined by optical microscopy for the unsaturated fatty-acid sucrose di-
esters.
Figure 16 shows the defect
texture of the columnar phase
of compound 2h. The texture is
characterized by the absence of
homeotropic alignment and the
lack of hyperbolic and elliptical
lines of optical discontinuity.
However, the fanlike regions
are classical signatures for the
presence of a columnar phase.
Sucrose diester
Chain length
Compd Transition temperature [8C]
m=10, n=5, p=3 1c
m=14, n=5, p=7 1d
soft solid–smectic A 110 iso. liq.
soft solid–col. 121 iso. liq.
Differential scanning calorime-
try (DSC): To aid comparison,
the DSC data for the clearing-
point enthalpies and entropies
of the esters 2 f, 2g, 2h, 3b, and
4a are listed in Table 9. By
comparing these results with
those in Table 2, it is clear that
the presence of a cis double
bond in the aliphatic chains in-
duces a decrease in the relative
n=5, p=3
n=5, p=7
n=7, p=7
2 f
2g
2h
soft solid–smectic A 138.5 iso. liq.
soft solid–smectic A 144.6 iso. liq.
soft solid–col. 146.3 iso. liq.
isotropization
temperature.
Similarly, the enthalpy and en-
tropy values are slightly lower,
indicating that the unsaturated
systems form more-disordered
liquid-crystal phases than their
m=10, n=5, p=3 3b
soft solid–smectic A 158.8 iso. liq. saturated analogues. In addi-
tion, the enthalpy and entropy
values for the columnar to the
isotropic liquid-crystal phase
transition for 2h are almost one
order of magnitude lower than
those for the lamellar phase to
the isotropic liquid transition
for compounds 2 f, 2g, and 3b.
This result indicates that the
structure within the columnar
phases is disordered and liquid-
like, and even the columns
m=10, n=5, p=3 4a
soft solid–smectic A 128.5 iso. liq.
themselves may not be periodi-
cally ordered on a hexagonal
lattice. Furthermore, the low
enthalpy and entropy values in-
dicate the structuring in the
liquid-crystal state is similar to
contrast, compound 1d, which has the same number of
carbon atoms in the chains (1’,6’-substitution and one unsa-
turation) possesses a columnar phase. The type of columnar
phases present appeared to be disordered hexagonal phases,
suggesting that the unsaturated aliphatic chain cross-section-
al areas were expanded relative to those of the saturated
chains, thereby causing the introduction of curvature into
the self-organization. Therefore, the structure of the col-
umns is disordered with respect to the positions of the mole-
cules and their up and down orientations.
that in the liquid, and, thus, the liquid itself is structured.
Conversely, compound 4a appears to have intermediary
values between the lamellar and the columnar materials, in-
dicating that this compound may be located at the crossover
in the phase behavior.
Chem. Eur. J. 2007, 13, 1763 – 1775
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1773

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Figure 16. Defect texture (x100) of the columnar mesophase of 6,6’-di-O-
oleoylsucrose, 2h.
[
[
1
1.
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DS [mJg
K
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[
[
[
[
[
[
2
2
2
3
4
f
2.645
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[
[
A
C
H
T
R
E
U
N
G
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Received: March 15, 2006
Revised: July 10, 2006
Published online: November 23, 2006
Chem. Eur. J. 2007, 13, 1763 – 1775
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1775