Self-Assembly of a Low-Symmetry Monodendron Containing Two Asymmetrically Linked Molecular Wedges

Article abstract of DOI:10.1002/cphc.201000567

Herein, we describe the synthesis of a low-symmetry monodendron, 3,4-bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyloxy]benzoic acid, following a simple route which starts from gallic acid ethyl ester and does not require any protecting groups. The self-a

Full text of DOI:10.1002/cphc.201000567

DOI: 10.1002/cphc.201000567
Self-Assembly of a Low-Symmetry Monodendron
Containing Two Asymmetrically Linked Molecular Wedges
Janis Lejnieks,[a] Xiaomin Zhu,[a] Jingbo Wang,[a] Ahmed Mourran,[a] Helmut Keul,*[a]
¯
Martin Mçller,[a] Denis V. Anokhin,[b] and Dimitri A. Ivanov*[b]
Herein, we describe the synthesis of a low-symmetry mono-
dendron, 3,4-bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyl-
zene rings form crystalline and amorphous domains. Upon
cooling from the isotropic melt the compound exhibits a
monotropic smectic mesophase. In 100-nm-thick films on a
neutral substrate the structure loses its biaxiality, adopting a
hexagonal columnar structure with the columns oriented paral-
lel to the substrate. By contrast, in ultrathin films on graphite
the SFM likely reveals two crystal orientations, which can de-
velop due to the epitaxial adsorption on the substrate of the
alkyl chains pertinent to different benzene rings.
oxy]benzoic acid, following a simple route which starts from
gallic acid ethyl ester and does not require any protecting
groups. The self-assembled structures formed by the com-
pound in 3D and 2D were investigated by synchrotron X-ray
scattering and scanning force microscopy (SFM). In 3D, the
compound forms a stable crystalline phase with an orthorhom-
bic lattice in which the alkyl chains connected to different ben-
1. Introduction
The morphology of liquid-crystalline materials is known to be
strongly dependent on the molecular architecture of the meso-
gen. For optimal packing high molecular symmetry is consid-
ered to be preferred. Thus, columnar liquid-crystalline phases
exhibiting 2D- or 3D-positional order[1] are usually formed from
molecules with flat rigid[2] or semirigid[3] cores surrounded by
flexible peripheral chains resembling a disc[1] or part of a disc,
such as a wedge or monodendron.[4,5] Monodendrons can self-
assemble into smectic or columnar phases with or without the
formation of supramolecular discs,[5] which can be in turn
stacked in columns stabilized by specific interactions, such as
p–p interactions,[6] H-bonding,[7,8] or ionic interactions.[9] The ar-
rangement of the bulky side groups can be sometimes im-
proved by rotation of each layer in the column by a certain
angle relative to the previous layer. As a result, regular heli-
coidal structures with a circular cross section are formed. In
contrast, self-assembly of low-symmetry molecular architec-
tures is more problematic in terms of achieving dense packing
and completely different supramolecular structures can often
be formed in this process. The two most fascinating examples
of such self-assembly are the theoretically predicted chiral
smectic C phases formed by chiral rod-like molecules display-
ing ferroelectric properties[10,11] and biaxial nematic phases of a
boomerang-shaped molecule recently discovered by E. T. Sa-
mulski et al.[12,13] Such biaxial mesophases exhibit fast switching
(between different orientations of molecules and is induced by
an external electrical field) and therefore are superior in com-
parison with classical uniaxial nematic phases widely used in
displays and other opto-electrical devices.[14] Other examples of
low-symmetry molecules are, for instance, banana-shaped[15]
and hockey-stick-shaped molecules.[16]
are 3,4,5-tris(alkyloxy)-,[4,5] 2,3,4-tris(alkyloxy)-[17] as well as
3,5-bis(alkyloxy)-[5] substituted benzene ring motifs of wedge-
shaped architectures. In contrast to deformed calamitic mole-
cules with broken symmetry, low-symmetry monodendrons
have attracted much less attention so far. These systems show
a wide variety of crystalline and liquid-crystalline phases in-
cluding ferroelectric phases.[18] Herein, we propose a new
model of architecture of wedge-shaped amphiphilic molecules
with low symmetry (molecule A in Scheme 1) and explore their
self-assembling properties. The molecular core geometry ex-
plored here can be viewed as a hybrid of two molecular
Scheme 1. Wedge-shaped amphiphilic molecule A with low symmetry syn-
thesized herein.
[a] J. Lejnieks, Dr. X. Zhu, J. Wang, Dr. A. Mourran, Dr. H. Keul, Prof. M. Mçller
DWI an der RWTH Aachen e.V. and
Institut fꢀr Technische und Makromolekulare Chemie der RWTH Aachen
Pauwelsstr. 8, 52056 Aachen (Germany)
Fax: (+49)241-8023301
E-mail: keul@dwi.rwth-aachen.de
[b] Dr. D. V. Anokhin, Dr. D. A. Ivanov
Institut de Sciences des Matꢁriaux de Mulhouse (CNRS LRC 7228, IS2M)
15 rue Jean Starcky, 68057 Mulhouse (France)
Fax: (+33)389608799
Some of the most powerful molecular building blocks for
supramolecular (hexagonal) columnar liquid-crystalline phases
E-mail: dimitri.ivanov@uha.fr
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Self-Assembly of Low-Symmetry Monodendron
wedges functionalized with a carboxylic acid group at the
focal point. In our previous work we discovered the contribu-
tion of different structural units to the self-assembling process
of a wedge-shaped amphiphilic molecule in 2D and 3D by
means of scanning tunneling microscopy and X-ray diffraction
(XRD).[19] Here, we aim at understanding the self-organization
mechanism for this novel molecular architecture in different
conditions of spatial confinement using the combination of
XRD and scanning force microscopy (SFM) techniques.
2. Results and Discussion
Scheme 3. Synthesis of 3,4-bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyl-
oxy]benzoic acid (A). Conditions: i) LiAlH4, THF, 08C–r.t., then NaOH/H2O;
ii) SOCl2, DCM, 08C–r.t. iii) KOH, EtOH, H2O, reflux, then HCl (conc.).
To design a low-symmetry benzyl ether dendron with long
alkyl chains at the periphery functionalized with a carboxylic
acid group at the focal point we developed a simple synthetic
route. The synthesis of the target low-symmetry dendron A via
the asymmetrically substituted ester 2a does not necessitate
protective groups (Scheme 2) and is based on the fact that the
XRD was used to address the phase behavior of compound A.
The DSC traces of this material recorded during the first heat-
ing showed only one endothermic peak at 728C characterized
by a high transition enthalpy of 92.3 JgÀ1 (Figure 1). According
Scheme 2. Etherification of gallic acid ethyl ester with 2 eq of 1-bromo-
dodecane. Conditions: 2 eq C12H25Br, 2 eq K2CO3, DMF, 1208C, 24 h.
Figure 1. DSC traces of compound A recorded at 108CminÀ1: 1) first heating,
2) subsequent cooling, and 3) second heating scan.
nucleophilicity of the hydroxy group at position 4 of the gallic
acid ethyl ester 1 is higher than that of the hydroxy groups at
positions 3 and 5. Etherification of gallic acid ethyl ester 1 with
two equivalents of 1-bromododecane (Scheme 2) yields a mix-
ture of ethyl 3,4-bis(dodecyloxy)-5-hydroxybenzoate 2a, ethyl
3,4,5-tris(dodecyloxy)benzoate 2b, and ethyl 4-(dodecyloxy)-
to POM observations, this peak corresponds to sample iso-
tropization. During the following cooling run, two distinct exo-
thermic peaks at 388C (4.50 JgÀ1) and 148C (24.7 JgÀ1) were
observed. Upon cooling from the isotropic melt, compound A
reveals a fan-shaped texture (Figure 2), which is typical of a
1
3,5-dihydroxybenzoate 2c. According to H NMR analysis, the
ratio of 2a:2b:2c is about 2:1:1, as expected. Pure products
were obtained by column chromatography using silica gel as
stationary phase and a solvent mixture of hexane/ethyl acetate
(9/1 v/v) as eluent.
Higher generation low-symmetry benzyl ether dendrons
were obtained starting with ethyl 3,4-bis(dodecyloxy)-5-hy-
droxybenzoate 2a and ethyl 3,4,5-tris(dodecyloxy)benzoate 2b
(Scheme 3). Etherification of 2a at position 5 with 5-(chloro-
methyl)-1,2,3-tris(dodecyloxy)benzene 4b obtained from 2b
through reduction with LiAlH4 and subsequent conversion of
the hydroxymethyl group of 3b into a chloromethyl group
using thionyl chloride resulted in the desired low-symmetry
ester 5 in quantitative yield. Finally, ester 5 was hydrolyzed to
the corresponding acid A, which was isolated as a white
powder.
Figure 2. Polarized optical microscopy image showing liquid-crystalline tex-
ture of compound A at 408C formed upon cooling from the isotropic phase
A combination of differential scanning calorimetry (DSC),
variable-temperature polarizing optical microscopy (POM), and
at a rate of 108CminÀ1
.
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H. Keul, D. A. Ivanov et al.
smectic or columnar liquid-crystalline phase (cf. for example
ref. [9]). It is likely that the compound crystallizes upon further
cooling to 148C, since the enthalpy of this transition is rather
high. The DSC curve obtained during the second heating ap-
pears to be rather complex: it reveals a number of endother-
mic and exothermic peaks. This signifies that compound A un-
dergoes several phase transitions before isotropization. To
identify the different phases formed by compound A we car-
ried out synchrotron XRD experiments at variable tempera-
tures.
thermal expansion becomes positive with the value typical of
organic crystals aCr =1.1ꢂ10À4 KÀ1.[21] In this temperature range
an additional crystalline peak, which corresponds to crystalliza-
tion of the alkyl chains, appears in the diffractograms at
s=0.24 ꢁÀ1.
A typical X-ray diffractogram of a fiber of A recorded at
room temperature is shown in Figure 5. In contrast to the
sample that was freshly cooled to 08C (Figure 3), the sample
The XRD measurements were performed on fibers of com-
pound A extruded from the mesophase. By cooling the sam-
ples from the isotropic melt, a smectic liquid-crystalline phase
was formed at 488C (Figure 3). This is slightly higher than the
Figure 5. 2D X-ray diffraction pattern of a fiber of A extruded at room tem-
perature directly after cooling from the isotropic state and subsequently an-
nealed for 2 h at room temperature. The fiber axis is vertical.
annealed at room temperature for two hours exhibits several
orders of the 100 reflection on the equator of the pattern
(Table 1). This infers a smectic-type ordering of the sample. Fur-
Figure 3. Temperature-dependent X-ray diffraction measurements of com-
pound A. The experiment was conducted on cooling from 100 to 08C at
108CminÀ1. TI–LC and TLC–Cr denote the temperatures of the isotropic-to-
liquid-crystal and liquid-crystal-to-crystal transitions, respectively. The peak
at 0.065 ꢁÀ1 originates from the Kapton film.
Table 1. Experimental (dexp) and calculated (dcalc) d-spacings correspond-
ing to diffraction peaks of A at room temperature. The peaks were in-
dexed to an orthorhombic lattice with a=40.14 ꢁ, b=30.38 ꢁ, and
c=4.62 ꢁ.
corresponding transition temperature found in the DSC mea-
surements. It is noteworthy that the smectic period increases
upon cooling and reaches 38 ꢁ at 258C. The negative linear
thermal expansion coefficient (aLC =À2ꢂ10À3 KÀ1) measured in
the range of 48–208C (Figure 4) is comparable to the values
obtained for other supramolecular liquid-crystalline systems.[20]
Importantly, this coefficient is equal to that found for the iso-
tropic phase, which still exhibits a broad halo at approximately
the same angular position. At temperatures below 208C the
h
k
l
dexp
dcalc
1
0
1
2
0
3
4
2
4
5
0
4
6
0
7
7
4
0
8
0
3
2
0
6
0
1
1
0
2
0
0
3
2
0
4
3
0
5
0
2
5
6
0
0
0
3
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
40.0
30.1
25.1
20.1
14.8
13.2
9.83
8.98
8.61
8.15
7.65
7.16
6.58
6.12
5.89
5.38
5.26
5.07
4.9
40.1
30.4
24.2
20.1
15.2
13.4
10
9.04
8.37
8.03
7.59
7.13
6.69
6.08
5.73
5.37
5.2
5.06
5.02
4.62
4.37
4.12
3.95
3.80
4.63
4.35
4.13
3.95
3.80
Figure 4. Position of the first diffraction peak as a function of temperature
for compound A upon cooling from 100 to 08C at 108CminÀ1 (Figure 3).
The dashed lines show the phase transition temperatures.
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Self-Assembly of Low-Symmetry Monodendron
thermore, a number of intense equatorial reflections were ob-
served which were assigned to 0k0 peaks. A small c-parameter
(4.62 ꢁ) indicates stacking of the flat molecules of A along the
meridonal direction. Importantly, it was also found that the
fiber annealed for several days at room temperature did not
exhibit any further structural evaluation. The annealed struc-
ture was also preserved during heating up to the isotropiza-
tion temperature of 728C.
As can be seen from 1D X-ray scattering curves (Figures 6,7),
the intensity of 100 and 010 peaks is of the same order of
magnitude as that of the peaks corresponding to the packing
Figure 8. Unit cell structure of A in the ab-projection.
after annealing the sample for several days in the crystalline
state, which is rather unusual for mesogens with lateral alkyl
chains containing twelve carbon atoms.[20,22] Generally, it seems
that this is the optimal length of the alkyl chains to enable
self-organization of the 3,4,5-tris(alkyloxy) group in a liquid-
crystal-like phase at room temperature at a reasonable pace.
The lack of one side group thus drastically hinders the forma-
tion of the sublattice. As a result, an unusual rectangular co-
lumnar phase is developed with three different regions, that is,
the crystalline and amorphous domains of alkyl chains and
crystalline rigid aromatic cores. Due to the noncircular cross
section of columns, this phase has a particular density contrast.
In the a-direction, the high-density regions of stacked phenyl
cores alternate with ordered alkyl chains. Such a partly ordered
phase of the side chains can be the driving force for self-or-
ganization of the aromatic molecular cores and formation of
the main lattice.[22,23] In the b-direction the phenyl cores are
separated by small amorphous domains of disordered side
groups. The alternation of the low- and high-density layers
generates a series of intense h00 and 0k0 reflexes. For further
refinement of the model, electron density map calculations as
well as molecular simulations will be required.
Figure 6. Small-angle XRD curve of A upon annealing for 2 h at room tem-
perature.
The structure of a thin film of A of ~100 nm thickness de-
posited on a silicon wafer was studied by grazing incidence
wide-angle X-ray scattering (GIWAXS) measurements. Figure 9
displays a typical 2D GIWAXS pattern revealing a three-spot
picture characteristic of a columnar hexagonal phase. In this
case, the hexagonally packed columns lie parallel to the sub-
strate. Given that the meridional peak is much more intense
Figure 7. Wide-angle XRD curves of A measured during cooling at 308C
(a) and upon annealing for 2 h at room temperature (c).
of the alkyl chains. The predominantly meridional position of
the peaks of the alkyl sublattice indicates that the alkyl chains
are aligned parallel to the ab-plane. The diffractogram can be
accounted for by a unit cell structure in which two molecules
have their rigid cores close to each other (Figure 8). From mo-
lecular modeling we found that these cores are stabilized by
hydrogen bonds formed in the direction of the c-axis, that is,
between the ab-planes. In this case, three alkyl chains of each
molecule in the layer are oriented along the a-axis and form a
regular sublattice. On the opposite side of the molecular cores,
the two alkyl groups are probably not numerous enough to
pack in the crystalline register, and therefore form disordered
low-density regions that generate an amorphous halo in the
diffractogram (Figure 7). The halo stays quite intense even
Figure 9. GIWAXS pattern recorded on a thin film of A. The film surface is
horizontal. The diffraction peaks correspond to a hexagonal phase with
a=40.5 ꢁ.
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H. Keul, D. A. Ivanov et al.
than the two other peaks of the lattice, the direction of the
columns is isotropic in the plane of the substrate. The lattice
of compound A in thin films substantially differs from the one
in the bulk. It is thus likely that the conditions of sample prep-
aration and geometrical confinement limit molecular mobility,
thereby impeding the formation of a regular three-dimensional
lattice. In this case, the structure of A in the direction perpen-
dicular to the columnar axis loses its asymmetry and exhibits
only one characteristic distance close to the a-parameter of
the 3D crystalline phase described above (Table 1).
3. Conclusions
A new low-symmetry monodendritic molecule functionalized
with a carboxylic group at the focal point, 3,4-bis(dodecyloxy)-
5-[3,4,5-tris(dodecyloxy)benzyloxy]benzoic acid, was synthe-
sized in high yield via a simple route starting from gallic acid
ethyl ester without the need for protecting groups. The result-
ing compound was characterized by a combination of DSC,
POM, and XRD. It was shown that the compound exhibits a
stable rectangular columnar crystalline phase and a monotrop-
ic smectic phase formed upon cooling from the isotropic melt.
In the crystalline structure the columns with noncircular cross
section are formed due to specific arrangement of crystalline
and amorphous domains of alkyl chains.
Figure 10 shows the morphology of an ultrathin film of A on
graphite after annealing the sample at 458C. The SFM height
image, generated in tapping mode, reveals two morphological
The structure of the compound crucially depends on the
conditions of the geometrical confinement. Thus, a 100-nm-
thick film reveals a columnar hexagonal phase with the col-
umns oriented parallel to the substrate.
The SFM investigation of ultrathin films of the compound on
graphite likely shows two crystal orientations that can develop
due to epitaxial adsorption of the alkyl chains attached to dif-
ferent benzene rings.
This compound exhibits a very peculiar structure in which
three alkyl chains crystallize and the other two remain in the
amorphous state. Meanwhile the crystalline and amorphous
domains are well-ordered in 3D. Such a structure might be
used to create membranes for gas separation. Furthermore,
the compound is a unique building block for the construction
of new functional materials. Different groups such as crown
ether and sulfonic acid can be linked to the acid site. This
could lead to the formation of various fascinating structures.
Figure 10. Height and phase images of a thin film of A on HOPG acquired in
tapping mode. The arrows (left image) point at smooth adlayers with a mo-
lecular thickness of 4.2 ꢁ (cf. cross section). This featureless film coexists
with a substructured layer (right image). The inset is a phase image to high-
light the substructure. The power spectral density (PSD) indicating an in-
plane periodicity of 43 ꢁ is shown at the bottom.
Experimental Section
Materials
1-Bromododecane (97%), LiAlH4 (95+ %), SOCl2 (99+ %), NaOH
(97%), ethyl 3,4,5-trihydroxybenzoate (98%), and anhydrous K2CO3
(all from Aldrich) were used as received. DMF was dried over calci-
um hydride (CaH2) for 12 h and distilled under vacuum.
traits. The first is a featureless layer with a thickness of 4.2 ꢁ,
which is close to the c-parameter of the crystalline lattice mea-
sured by XRD. The sharp edges of this layer indicate on its
crystalline nature (right image in Figure 10). The second is a
substructured layer with less defined height. The inner sub-
structure is better resolved in the phase image where the
Synthesis
stripes with
a periodicity of 43 ꢁ can be seen (insert,
Ethyl 3,4-bis(dodecyloxy)-5-hydroxybenzoate (2a) and Ethyl 3,4,5-
tri(dodecyloxy)benzoate (2b): Anhydrous K2CO3 (4.44 g, 32 mmol,
2 eq) and 1-bromodecane (8 g, 32 mmol, 2 eq) were added to a so-
lution of gallic acid ethyl ester (3.18 g, 16 mmol, 1 eq) in dry DMF
(60 mL). The mixture was heated at 1208C under N2 atmosphere
for 20 h. The reaction mixture was allowed to cool to room tem-
perature before water (150 mL) was added. The formed brownish
precipitate was filtrated and dried in vacuo. A brownish solid was
obtained, a mixture of 2a, 2b, and 2c, which were successfully
separated using column chromatography (silica gel, hexane/ethyl
acetate=9/1).
Figure 10). This periodicity is close to the a-parameter of the
crystalline lattice.
The two morphologies may simply correspond to two differ-
ent crystal orientations of A on graphite. The thickness of the
smooth layer matches the c-parameter of the unit cell, thus
the crystal is oriented with its ab-plane lying on the substrate.
The elongated stripes would then correspond to a crystal ori-
entation in which the ac-plane runs parallel to the substrate. In
the first orientation, the alkyl chains can probably extend
easier on the graphite surface toward which they have a spe-
cial affinity (Figure 8). However, even for the second orienta-
tion the epitaxial interactions of the alkyl chains with the
graphite surface are not excluded.
1
2 a: H NMR (300 MHz, CDCl3, TMS): d=0.88 (t, 3H), 1.26 (m, 36H),
1.37 (t, overlapped, 3H), 1.75 (m, 4H), 4.03 (t, 2H), 4.15 (t, 2H), 4.33
(q, 2H), 5.88 (s, 1H), 7.18 (d, 1H), 7.29 ppm (d, 1H); 13C NMR
(75 MHz, CDCl3, TMS): d=14.1, 14.3, 22.7, 25.9, 26.2, 29.3, 29.4,
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Self-Assembly of Low-Symmetry Monodendron
29.4, 29.6, 29.7, 30.2, 31.9, 61.0, 68.9, 73.6, 76.7, 77.0, 77.4, 106.4,
125.6, 138.6, 149.1, 151.3, 166.3 ppm.
2b: H NMR (300 MHz, CDCl3, TMS): d=0.88 (t, 3H), 1.27 (m, 54H),
1.38 (t, overlapped, 3H), 4.02 (t, 6H), 4.34 (q, 2H), 7.26 ppm (s, 2H);
13C NMR (75 MHz, CDCl3, TMS): d=14.1, 14.4, 22.7, 26.1, 29.4, 29.4,
29.6, 29.7, 29.7, 30.4, 32.0, 61.0, 69.2, 73.5, 108.0, 125.1, 142.3,
152.8, 166.5 ppm.
Polarizing Optical Microscopy: POM analyses were performed with
Zeiss AXIOPLAN 2 polarizing microscope, equipped with
METTLER FP 90 hot stage. Images were taken with a digital Zeiss
AxioCam MRC4 camera in combination with Zeiss AxioVision soft-
ware.
a
a
1
Differential Scanning Calorimetry: DSC measurements were per-
formed using a Netzsch DSC 204 unit. Samples (typical weight:
5 mg) were enclosed in standard Netzsch aluminium crucibles.
Indium and palmitic acid standards were used for calibration. The
[3,4,5-Tris(dodecyloxy)phenyl]methanol (3b): Ester 2b (2 g,
2.85 mmol, 1 eq) was dissolved in THF (20 mL) and cooled down to
08C. Then LiAlH4 (130 mg, 3.42 mmol, 1.2 eq) was added in small
portions and the reaction mixture was stirred at room temperature
overnight. Then the reaction mixture was cooled to 08C and water
(2 mL) was added slowly. The reaction mixture was diluted with
THF, the ice bath was removed and an aqueous solution (5 mL) of
NaOH (456 mg, 11.4 mmol, 4 eq) water added. The inorganic pre-
cipitate formed was filtered and disposed. The solvent was evapo-
rated and the product recrystallized from acetone yielding 1.54 g
heating and cooling rates were 108CminÀ1
.
Scanning Force Microscopy: SFM investigations were carried out
with a multimode AFM (NanoScope IIIa, Digital Instruments Veeco
Instruments, Santa Barbara, CA) under ambient conditions. Com-
mercially available silicon cantilevers (PPP-SEIH-W from Nanosen-
sors) with a nominal spring constant of 5–40 NmÀ1 and a reso-
nance frequency of 70–300 kHz were used. The tapping-mode to-
pography and phase images were processed with the Digital In-
struments NanoScope software (version 5.12r5).
1
white powder. Yield: 77%. H NMR (300 MHz, CDCl3, TMS): d=0.88
(t, 3H), 1.27 (m, 54H), 1.76 (m, 6H), 3.96 (m, 6H), 4.57 (s, 2H),
6.54 ppm (s, 2H); 13C NMR (75 MHz, CDCl3, TMS): d=14.1, 22.7,
25.8, 26.1, 29.4, 29.7, 29.7, 29.8, 30.3, 32.0, 65.5, 69.0, 73.5, 105.3,
136.2, 153.2 ppm.
X-Ray Diffraction: XRD experiments were carried out on the BM26B
beamline[24] at the European Synchrotron Radiation Facility (ESRF,
Grenoble, France) with a Frelon CCD camera. A wavelength of
1.24 ꢁ was used. Oriented fibers with a diameter of 0.5 mm were
extruded at room temperature after rapid cooling from melt using
a homemade mini-extruder. Variable-temperature measurements
were carried out in a Linkam heating stage using an acquisition
time of 24 s. Small-angle X-ray scattering measurements were per-
formed with a 2D gas detector at a sample–detector distance of
1.5 m. The modulus of the scattering vector s (s=2 sinV/l, where
V is the Bragg angle and l the wavelength) was calibrated using
several diffraction orders of silver behenate.
5-(Chloromethyl)-1,2,3-tris(dodecyloxy)benzene (4b): [3,4,5-Tris(do-
decyloxy)phenyl]methanol (1 g, 1.51 mmol, 1 eq) was dissolved in
chloroform (20 mL) and cooled to 08C. Thionyl chloride (198 mg,
1.66 mmol, 1.1 eq) in chloroform (2 mL) was added dropwise and
the reaction mixture was stirred under N2 atmosphere at room
temperature for 1 h. The solvent and excess of thionyl chloride
were evaporated in vacuo and the slightly yellowish solid obtained
was used immediately for the next step. Yield: 100%.
Ethyl
3,4-bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyloxy]ben-
Grazing Incidence Wide-Angle X-Ray Scattering: GIWAXS experi-
ments were conducted on the ID10 beamline of the ESRF using a
wavelength of 1.55 ꢁ and an incidence angle of 0.28. The samples
for GIWAXS were prepared by spin-coating of a 10 mgmLÀ1 solu-
tion of A in chloroform on cleaned silicon wafers. The scattering
was recorded with a MAR CCD camera.
zoate (5): Freshly prepared chloride 4b (1.04 g, 1.51 mmol, 1 eq)
was placed in DMF (30 mL) and anhydrous K2CO3 (0.42 g,
3.02 mmol, 2 eq) and 2b (0.82 g, 1.51 mmol, 1 eq) were added. The
mixture was heated under N2 atmosphere at 1208C for 24 h and
poured hot into ice water (250 mL). The product was filtered and
dried, yielding
a
yellowish solid (1.7 g). Yield: 96%. 1H NMR
(300 MHz, CDCl3, TMS): d=0.88 (t, 3H), 1.26 (m, 90H), 1.39 (t, over-
lapped 3H) 1.79 (m, 10H), 3.96 (m, 10H), 4.34 (q, 2H), 5.02 (s, 2H),
7.29 ppm (s, 1H); 13C NMR (75 MHz, CDCl3, TMS): d=14.1, 14.4,
22.7, 26.1, 26.2, 29.3, 29.4, 29.5, 29.6, 29.7, 29.7, 30.4, 32.0, 61.0,
69.1, 71.5, 73.4, 73.6, 76.7, 77.0, 77.2, 77.4, 105.7, 108.3, 109.1,
125.1, 132.0, 137.7, 142.6, 152.3, 152.9, 153.2, 166.3 ppm.
Acknowledgements
The authors acknowledge the French Agence Nationale de la Re-
cherche (projects SPIRWIND and T2T) and Deutsche Forschungs-
gemeinschaft (Project T2T) for financial support. The authors ac-
knowledge the European Synchrotron Radiation Facility for pro-
viding the excellent environment for X-ray measurements. We are
grateful to W. Bras and G. Portale (BM26, ESRF) and to O. Kono-
valov (ID10, ESRF) for assistance in the diffraction experiments
and fruitful discussions.
3,4-Bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyloxy]benzoic acid
(A): Ester 5 (0.9 g 0.764 mmol, 1 eq), KOH (0.172 g, 3.06 mmol,
4 eq), ethanol (30 mL), and water (5 mL) were refluxed for 12 h.
Then the reaction mixture was cooled to 30–408C and concentrat-
ed hydrochloric acid was added carefully until a pH of 1 was
reached. The white precipitate formed was filtered and dried in
1
vacuo. Yield: 85%. H NMR (300 MHz, CDCl3, TMS): d=0.88 (t, 3H),
1.26 (m, 90H), 1.82 (m, 10H), 3.97 (m, 10H), 5.04 (s, 2H), 6.66 (s,
2H), 7.36 (d, 1H), 7.41 ppm (d, 1H); 13C NMR (75 MHz, CDCl3, TMS):
d=14.1, 22.7, 26.1, 26.2, 29.3, 29.4, 29.4, 29.5, 29.6, 29.7, 30.4, 32.0,
69.1, 71.5, 73.4, 73.7, 105.9, 108.9, 109.7, 123.8, 131.8, 137.8, 143.5,
152.4, 153.0, 153.2, 171.6 ppm.
Keywords: monodendrons · phase transitions · self-assembly ·
thin films · X-ray diffraction
[1] S. Chandrasekhar, B. K. Sadashiva, K. A. Suresh, Pramana 1977, 9, 471–
480.
[2] R. I. Gearba, A. Bondar; M. Lehmann, B. Goderis, W. Bras, M. H. J. Koch,
D. A. Ivanov, Adv. Mater. 2005, 17, 671–676, B. Goderis, W. Bras, D. A.
Ivanov, Chem. Mater. 2005, 17, 2825–2832.
Characterization
[3] M. Lehmann, R. I. Gearba, M. H. J. Koch, D. A. Ivanov, Chem. Mater. 2004,
16, 374–376.
1
NMR Spectroscopy: H NMR (300 MHz) and 13C NMR (75 MHZ) spec-
tra were recorded on a Bruker DPX-300 spectrometer in chloroform
(CDCl3) with tetramethylsilane (TMS) as internal standart at 208C.
[4] V. Percec, G. Johansson, J. Heck, G. Ungar, S. V. Batty, J. Chem. Soc.,
Perkin Trans. 1 1993, 1411–1420.
ChemPhysChem 2010, 11, 3638 – 3644
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemphyschem.org
3643

H. Keul, D. A. Ivanov et al.
[5] U. Beginn, Prog. Polym. Sci. 2003, 28, 1049–1105.
[6] S. Kumar, Chem. Soc. Rev. 2006, 35, 83–109.
[7] V. Percec, A. E. Dulcey, M. Peterca, M. Ilies, J. Ladislaw, B. M. Rosen, U.
Edlund, P. A. Heiney, Angew. Chem. 2005, 117, 6674–6679; Angew.
Chem. Int. Ed. 2005, 44, 6516–6521.
[16] F. C. Yu, L. J. Yu, Chem. Mater. 2006, 18, 5410–5420.
[17] X. Zhu, M. A. Scherbina, A. V. Barikov, B. Gorzolnik, S. N. Chvalun, U.
Beginn, M. Mçller, Chem. Mater. 2006, 18, 4667–4673.
[18] K. Kishikawa, S. Nakahara, Y. Nishikawa, S. Kohmoto, M. Yamamoto, J.
Am. Chem. Soc. 2005, 127, 2565–2571.
[8] V. Percec, A. E. Dulcey, M. Peterca, P. Adelman, R. Samanta, V. S. K. Bala-
gurusamy, P. A. Heiney, J. Am. Chem. Soc. 2007, 129, 5992–6002.
[9] X. Zhu, B. Tartsch, U. Beginn, M. Mçller, Chem. Eur. J. 2004, 10, 3871–
3878.
[19] X. Zhu, A. Mourran, U. Beginn, M. Mçller, D. V. Anokhin, D. A. Ivanov,
Phys. Chem. Chem. Phys. 2010, 12, 1444–1452.
[20] R. I. Gearba, A. Bondar; M. Lehmann, B. Goderis, W. Bras, M. H. J. Koch,
D. A. Ivanov, Adv. Mater. 2005, 17, 671–676.
[10] P. Oswald, P. Pieranski, Smectic and Columnar Liquid Crystals: Concepts
and Physical Properties Illustrated by Experiments, Taylor & Francis, Boca
Raton, 2006.
[21] R. I. Gearba, D. V. Anokhin, A. I. Bondar, Y. K. Godovsky, V. S. Papkov,
N. N. Makarova, S. N. Magonov, W. Bras, M. H. J. Koch, F. Masin, B. Gode-
ris, D. A. Ivanov, Macromolecules 2006, 39, 988–999.
[11] Handbook of Liquid Crystals (Eds. D. Demus, J. Goodby, G. W. Gray, H. W.
Spiess, V. Vill), Wiley-VCH, Weinheim, 1998.
[22] R. I. Gearba, D. V. Anokhin, A. I. Bondar, W. Bras, M. Lehmann, D. A.
Ivanov, Adv. Mater. 2007, 19, 815–820.
[12] T. J. Dingemans, N. S. Murthy, E. T. Samulski, J. Phys. Chem. B 2001, 105,
8845–8860.
[13] T. J. Dingemans, L. A. Madsen, N. A. Zafiropoulos, W. Lin, E. T. Samulski,
Philos. Trans. R. Soc. A 2006, 364, 2681–2696.
[23] R. I. Gearba, M. Lehmann, J. Levin, D. A. Ivanov, M. H. J. Koch, J. Baberꢃ,
M. G. Debije, J. Piris, Y. H. Geerts, Adv. Mater. 2003, 15, 1614–1618.
[24] W. Bras, I. P. Dolbnya, D. Detollenaere, R. van Tol, M. Malfois, G. N.
Greaves, A. J. Ryan, E. Heeley, J. Appl. Crystallogr. 2003, 36, 791–794.
[14] V. Prasad, Sh.-W. Kang, K. A. Suresh, L. Joshi, Q. Wang, S. Kumar, J. Am.
Chem. Soc. 2005, 127, 17224–17227.
Received: July 14, 2010
[15] R. A. Reddy, B. K. Sadashiva, V. A. Raghunathan, Chem. Mater. 2004, 16,
4050–4062.
Published online on October 26, 2010
3644
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