A diacetylene-containing wedge-shaped compound: Synthesis, morphology, and photopolymerization

Article abstract of DOI:10.1002/chem.201203240

A novel wedge-shaped compound containing two diacetylene tails, namely, methyl 3,5-bis(trideca-2,4-diyn-1yloxyl)benzoate (DDABM), was synthesized. As shown by UV/Vis spectroscopy this compound can be polymerized under UV irradiation. The crystalline structure of DDABM was investigated by grazing-incidence wide-angle X-ray diffraction on oriented crystalline films deposited on PTFE-rubbed silicon wafer substrates. Furthermore, the spherulites formed in thicker films were analyzed by wide-angle X-ray diffraction. A molecular packing model of DDABM based on the X-ray diffraction data is proposed. The diacetylene units are oriented along a defined lattice direction with a reticular distance of 4.85 ?, which fulfills the requirements for topochemical polymerization. It was observed that UV polymerization does not affect the phase behavior of the compound, but mainly alters its optical properties. Tails of two diacetylenes: A wedge-shaped compound containing two diacetylene tails can be polymerized under UV irradiation. Detailed analysis of the crystalline structure of this compound revealed that the diacetylene units are oriented along a defined lattice direction (see picture) with a packing period of 4.85 ?, which fulfills the requirements for topochemical polymerization. Importantly, UV polymerization does not affect the phase behavior of the compound, but mainly alters its optical properties. Copyright

Full text of DOI:10.1002/chem.201203240

DOI: 10.1002/chem.201203240
A Diacetylene-Containing Wedge-Shaped Compound: Synthesis,
Morphology, and Photopolymerization
Martin Rosenthal,[b, c] Lei Li,[a] Jaime J. Hernandez,[b] Xiaomin Zhu,*[a]
Dimitri A. Ivanov,*[b, c] and Martin Mçller[a]
Abstract: A novel wedge-shaped com-
line films deposited on PTFE-rubbed
silicon wafer substrates. Furthermore,
the spherulites formed in thicker films
were analyzed by wide-angle X-ray dif-
fraction. A molecular packing model of
DDABM based on the X-ray diffrac-
pound containing two diacetylene tails,
namely, methyl 3,5-bis(trideca-2,4-diyn-
1yloxyl)benzoate (DDABM), was syn-
thesized. As shown by UV/Vis spectro-
scopy this compound can be polymer-
ized under UV irradiation. The crystal-
line structure of DDABM was investi-
gated by grazing-incidence wide-angle
X-ray diffraction on oriented crystal-
tion data is proposed. The diacetylene
units are oriented along a defined lat-
tice direction with a reticular distance
of 4.85 ꢀ, which fulfills the require-
ments for topochemical polymeriza-
tion. It was observed that UV polymer-
ization does not affect the phase be-
havior of the compound, but mainly
alters its optical properties.
Keywords: alkynes · photochemis-
try · polymerization · topochemis-
try · X-ray diffraction
Introduction
As first demonstrated by Wegner,[1] the solid-state polymeri-
zation of crystalline diacetylene follows the so-called topo-
chemical principles.[2] A unique feature of this reaction is
that polymerization advances with only minimal structural
rearrangements. Therefore, its occurrence and the stereo-
chemistry of the polymer products are determined by the
crystal structure of the monomer. As shown in Scheme 1,
the necessary conditions for topochemical polymerization of
diacetylene were identified as follows. The diacetylene units
should be oriented along a defined lattice direction with a
translational period d in the range of 4.7–5.2 ꢀ, Rv must be
smaller than 4 ꢀ, with a lower limit of 3.4 ꢀ corresponding
to the van der Waals contact between the reacting carbon
atoms, and the angle g between the diacetylene rod and the
translational vector must be close to 458.[3] This route pro-
Scheme 1. Schematic representation of topochemical polymerization of
diacetylenes.
vides a unique approach toward fabrication of well-defined
highly stereoregular polymers that cannot be synthesized by
any alternative means.
[a] L. Li,+ Dr. X. Zhu, Prof. Dr. M. Mçller
Interactive Materials Research - DWI an der RWTH Aachen e.V.
and
Since the diacetylene unit was first used for topochemical
polymerization, the molecular design of diacetylene deriva-
tives has been attracting considerable interest for several
decades.[4] It is well established that diacetylene substituted
with various side groups such as amide,[5] carboxyl,[6] and
perfluorophenyl[7] can undergo photopolymerization on UV
irradiation in a wide range of ordered structures such as
crystals,[1,4b,8] liquid crystals,[9] Langmuir–Blodgett films,[10]
self-assembled monolayers,[6,11] lipid bilayers,[12] vesicles,[4c,13]
and even gels.[14] Importantly, the resulting long p-conjugat-
ed molecular structure has two spectroscopically distinct
phases, that is, the so-called blue and red forms that got
their names from the exciton absorption peaks at about 640
and 540 nm. The presence of these two forms in polydiacety-
lenes makes them suitable for numerous promising applica-
Institute for Technical and Macromolecular Chemistry of RWTH
Aachen University
Forckenbeckstrasse 50, 52056 Aachen (Germany)
Fax : (+49)241-80-233-01
E-mail: zhu@dwi.rwth-aachen.de
[b] Dr. M. Rosenthal,+ J. J. Hernandez, Dr. D. A. Ivanov
Institut de Sciences des Matꢁriaux de Mulhouse (IS2M-CNRS)
15 rue Jean Starcky, 68057 Mulhouse (France)
Fax : (+33)389-60-87-99
E-mail: dimitri.ivanov@uha.fr
[c] Dr. M. Rosenthal,+ Dr. D. A. Ivanov
Moscow State University
Faculty of Fundamental Physical and Chemical Engineering
GSP-1, 1-51 Leninskie Gory, Moscow, 119991 (Russian Federation)
[+] These authors contributed equally.
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FULL PAPER
tions ranging from biosensors[4c,15] and nonlinear optics[16] to
electron-transport materials.[17]
Most of the diacetylene derivatives studied so far contain
only one diacetylene fragment, so the conditions of their
topochemical polymerization can be fulfilled by a judicious
choice of side groups (R1 and R2 in Scheme 1). Much less
studied are compounds substituted with two or more diace-
tylene units, which, however, form different interesting su-
pramolecular assemblies such as rods[18] and tubules[19] that
can be arrested by diacetylene polymerization. Furthermore,
these molecules can be linked by an intermolecular reaction
even at a rather low degree of diacetylene polymerization.
However, it is also clear that an intramolecular reaction can
result in cyclization without a significant increase of the mo-
lecular weight. Since single-crystal X-ray diffraction (XRD)
data are usually not available for such systems, the relation
between the molecular packing and polymerizability of
these diacetylene derivatives is not fully understood so far.
Here we report on the structure–property relationship for
a newly synthesized wedge-shaped molecule containing two
polymerizable diacetylene tails: methyl 3,5-bis(trideca-2,4-
diyn-1yloxyl)benzoate (DDABM). To address the crystalline
structure of DDABM before and after photopolymerization,
silicon wafers rubbed with polytetrafluoroethylene (PTFE)
were used as substrate to prepare oriented crystalline thin
films, which were analyzed by grazing-incidence wide-angle
X-ray diffraction (GIWAXD). In addition spherulites
formed by DDABM in thicker films were studied by means
of WAXD with a small beam size.
Figure 1. Polarizing optical micrographs of DDABM crystallized on cool-
ing from the isotropic melt to room temperature before (top) and after
(bottom) UV irradiation.
Results and Discussion
Wedge-shaped compound DDABM was obtained as a
white crystalline powder. It forms large spherulites on cool-
ing the isotropic melt to room temperature (see Figure 1).
On irradiation with 254 nm UV light, the compound
changes color from white to red and then to blue and
purple. The gradual color change can be attributed to con-
tinuous formation of conjugated backbones and is observed
because the electronic transition of the p electrons of the
backbone occurs in the wavelength region of visible light.
The polymerized compound reveals a clearly visible Maltese
cross in polarizing optical micrographs (Figure 1 bottom)
when crystallized at room tem-
The synthesis of wedge-shaped DDABM is schematically
depicted in Scheme 2. Firstly, 1-bromo-1-decyne (1) was ob-
tained by bromination of 1-decyne with N-bromosuccini-
mide (NBS) and AgNO3 as catalyst. Reacting 1 with prop-
argyl alcohol under catalysis by CuCl gave trideca-2,4-diyn-
1-ol (2), which was subsequently transformed into 1-bromo-
trideca-2,4-diyne (3) with triphenylphosphine dibromide
(PPh3Br2). DDABM was synthesized from methyl 3,5-dihy-
droxybenzoate by etherification with 3 in acetone in the
presence of K2CO3.
perature; this feature is absent
for non-irradiated samples. It is
noteworthy that the melt vis-
cosity has increased after pho-
topolymerization.
The conversion of diacety-
lene groups to polydiacetylene
in DDABM was monitored by
UV/Vis and Raman spectrosco-
py. The non-irradiated sample
shows no absorption in the
range of 400-700 nm. After ex-
posure to 254 nm UV irradia-
Scheme 2. Synthetic route for the preparation of methyl 3,5-bis (trideca-2,4-diyn-1yloxyl)benzoate (DDABM).
i) NBS, AgNO3, acetone, RT, 2 h; ii) NH2OH·HCl, CuCl, ethylamine, methanol, 358C 24 h; iii) PPh3Br2, di-
chloromethane, 08C to RT, 24 h; iv) 18-crown-6, K2CO3, acetone, reflux, 24 h.
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X. Zhu, D. A. Ivanov et al.
Figure 4. DSC curves of DDABM before and after UV irradiation for
1 h.
chromatography did not show any difference between the
initial sample and the sample irradiated for 1 h, likely due
to largely intramolecular cyclization. Importantly, after 2 h
of irradiation the sample becomes partly insoluble in organ-
ic solvents, most probably due to the onset of intermolecular
polymerization.
Differential scanning calorimetry (DSC) shows no signifi-
cant differences in the thermal behavior of the irradiated
and non-irradiated DDABM samples (Figure 4). Thus, on
heating at a rate of 5.0 KminÀ1, samples annealed at room
temperature for 24 h reveal a similar thermal behavior with
only one melting event, at Tm =47.0 and 45.88C for the UV-
irradiated and non-irradiated compounds, respectively. The
melting enthalpies also differ only slightly: 93.2 JgÀ1 for the
non-irradiated and 93.9 JgÀ1 for the irradiated sample. Al-
though the sample irradiated for 2 h is partly insoluble in or-
ganic solvents, its thermal behavior is not significantly differ-
ent from that of the initial sample.
Figure 2. UV/Vis spectra of a crystalline thin film of DDABM after expo-
sure to 254 nm UV light for 0–60 min (film thickness is (200Æ5) nm).
tion for 1 min, two absorption bands at lmax =593 and
540 nm appear (Figure 2). A sharp absorption band at
593 nm is assigned to the excitonic transition of the conju-
gated polydiacetylene chains; the position of this peak de-
pends on the effective conjugation length of the polymer.
The presence of a second band at 540 nm can be attributed
to a broad distribution of the conjugation lengths present in
the polymers overlaid on the vibronic side bands of the pol-
ydiacetylene due to the stretching frequency associated with
the carbon–carbon double and triple bonds.[20] On further ir-
radiation up to 1 h, a slight blueshift of the absorption band
and an increase of the absorbance are observed, after which
the UV/Vis spectrum of DDABM does not change anymore.
The modification of the chemical structure can be also evi-
denced by Raman spectroscopy (Figure 3). Thus, after UV
By quenching DDABM from the isotropic melt to À208C
at a cooling rate of 40 KminÀ1, crystallization is bypassed.
On heating, cold crystallization takes place with Tc at À2.8
and À3.98C for the irradiated and non-irradiated DDABM
samples, respectively. The melting transition of the polymer-
ized sample is characterized by a Tm value of 43.28C and a
melting enthalpy of 85.0 JgÀ1, while for the non-irradiated
material the melting enthalpy and temperature are 91.0 JgÀ1
and 44.18C, respectively. The minor differences in thermal
behavior of irradiated and non-irradiated samples suggest
that the diacetylene polymerization does not have a signifi-
cant effect on the crystalline structure. This assumption is
supported by WAXD measurements performed on
DDABM powders annealed at room temperature before
and after UV irradiation (Figure 5). The curves reveal only
marginal differences in relative peak intensities, while the
positions of all reflections are invariant to UV treatment.
To address the crystalline structure of DDABM, silicon
wafer rubbed with PTFE was used as substrate to fabricate
oriented crystalline thin films by drop casting. This substrate
treatment is based on the original method of Wittmann and
Smith,[23] which is widely used to induce epitaxial or grapho-
epitaxial interactions with deposited organic films resulting
in their pronounced orientation. On annealing the spin-
Figure 3. Raman spectra of DDABM during exposure to 254 nm UV
light.
irradiation, a new band appears at 2124 cmÀ1, which corre-
sponds to polydiacetylene.[21] Moreover, the frequency shift
and intensity increase of the C=C stretching bands at about
1500 cmÀ1 in the Raman spectrum also indicate conversion
of diacetylene to polydiacetylene.[22] The DDABM sample
irradiated for 1 h is still soluble in THF, chloroform, and
some other organic solvents. Interestingly, size-exclusion
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Diacetylene-Containing Wedge-Shaped Compound
FULL PAPER
Figure 5. One-dimensional WAXD curves corresponding to isotropic
powder samples of DDABM recorded before and after 1 h UV-irradia-
tion. The curves reveal only slight differences in the relative peak intensi-
ties.
Figure 7. 2D grazing-incidence X-ray diffraction patterns corresponding
to an oriented film of DDABM deposited on a PTFE-rubbed silicon
wafer. The sample was annealed for 24 h at room temperature prior to
measurements. The incident X-ray beam was oriented perpendicular
(top) and parallel (bottom) to the rubbing direction. The GIWAXD pat-
terns are recalculated into the planar s space.
bic unit cell (Figure 7, top). The strong orientation of the
layers on PTFE, which is evident from the GIWAXD pat-
terns in Figure 7, can be explained by the interaction be-
tween the film and the substrate. In particular, the b param-
eter of the DDABM unit cell is oriented parallel to the a pa-
rameter of the PTFE crystal, that is, perpendicular to the
PTFE backbones. The c parameter of the DDABM crystal
is parallel to the PTFE rubbing, so that the contact plane of
the DDABM unit cell is 100. Although in principle the
nature of the film–substrate interaction can be epitaxial or
grapho-epitaxial, that is, due to the substrate topography,
the close match of the b parameter of DDABM with the a
parameter of the PTFE crystal (3.2% mismatch) prompts us
to suggest that in this case one can talk about a truly epitax-
ial growth mechanism.
Figure 6. Polarizing optical micrograph of
DDABM deposited on a silicon wafer rubbed with PTFE.
a crystalline thin film of
coated films at room temperature for 24 h, DDABM forms
crystalline stripes which are oriented along the rubbing di-
rection (Figure 6).
Two-dimensional GIWAXD patterns obtained from ori-
ented crystalline films of DDABM are shown in Figure 7.
Patterns were recorded with the X-ray beam perpendicular
and parallel to the rubbing direction. The strong h00 reflec-
tions located strictly on the meridian of the patterns indicate
smectic-like stacking of layers parallel to the PTFE-rubbed
substrate. Furthermore, the material shows a single-crystal-
like orientation, as can be seen from the absence of hkl re-
flections with l different from 0 when viewed along the rub-
bing direction.
The absence of first-order diffraction peaks along a* and
b* directions from the patterns indicates that the unit cell is
centered in the ab projection. The observed reflections to-
gether with the experimental and calculated d spacings are
given in Table 1.
The fast growth axis of DDABM can be identified from
the crystal orientation in large spherulites such as those
grown in films of several tens of micrometers thickness for
24 h at room temperature (cf. Figure 1). By using a rather
small X-ray beam size (200ꢃ200 mm2) compared to the later-
al dimensions of the spherulites (see Figure 1), oriented X-
ray patterns can be obtained (Figure 8). This situation is
similar to what was observed previously in microfocus X-ray
experiments on polymer spherulites.[24] From the presented
pattern, the fast growth axis, that is, the radial direction of
the spherulitic crystals, can be assigned to the crystallo-
graphic c axis. The absence of the higher order smectic h00
reflections indicates that, even in a reasonably thick film,
The lattice of DDABM is identified to be monoclinic with
respect to b, with four molecules per unit cell, as derived
from density considerations. The lattice parameters are a=
39.77, b=16.26, c=4.85 ꢀ, and b=88.88. The slight mono-
clinicity of the unit cell can be deduced from a small split of
ꢀ
the hkl and hkl peaks, but is more clearly revealed by the
fact that the h0l and hkl peaks are not positioned on the
same vertical lines, as would be expected for an orthorhom-
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X. Zhu, D. A. Ivanov et al.
Table 1. Experimental (dexptl
) and calculated (dcalcd) d spacings of
DDABM annealed at room temperature. The values of dexptl are derived
from the GIWAXD patterns given in Figure 7.
h
k
l
dexptl [ꢀ]
dcalcd [ꢀ]
Sublattice
indexes (hkl)
2
4
6
10
2
6
7
8
9
1
4
6
7
0
0
0
0
1
1
1
1
1
2
2
2
2
0
0
0
0
0
0
0
0
0
0
0
0
0
19.90
9.92
6.62
3.97
12.61
6.14
5.36
4.75
4.25
8.00
6.28
5.12
4.64
19.88
9.94
6.63
3.98
12.59
6.14
5.36
4.75
4.2
7.97
6.29
5.14
4.66
1
2
3
5
7
1
2
3
4
2
2
6
6
8
8
3
3
3
3
3
4
4
4
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5.36
5.21
5.01
4.47
3.91
4.03
3.99
3.88
3.76
4.73
4.69
3.97
5.37
5.23
5.02
4.48
3.92
4.05
3.98
3.89
3.76
4.74
4.69
3.95
3.88
3.51
3.44
Figure 8. 2D WAXD pattern recorded in transmission geometry on large
spherulites of DDABM grown in thick films after annealing them for
24 h at room temperature. The pattern is recalculated into the planar s
space.
100
101
101
ꢀ
0
1
102
À1
1
À1
1
À1
3.52
1
1
2
2
3
3
1
1
1
1
1
1
1
4.63
4.56
4.40
4.63
4.61
4.55
4.51
4.41
4.36
010
À1
ꢀ
1
011
À1
1
À1
011
Figure 9. Sublattice formed by octyl chains in the crystalline phase of
DDABM at 258C. The shown unit cell resembles the lattice of n-octane,
apart from its increased c parameter.
1
1
2
2
1
À1
4.14
4.11
4.15
4.14
1
1
2
2
3
3
3
3
3
3
3
3
1
3.61
3.57
3.48
3.61
3.60
3.57
3.55
3.50
3.48
À1
1
À1
1
À1
the smectic layers are oriented parallel to the substrate.
However, since several diffraction zones are present in the
pattern, a significant distribution of the crystal orientation
can be assumed. This is also supported by the fact that the
smectic layers are characterized by azimuthally broad reflec-
tions.
Scheme 3. Proposed molecular packing of DDABM in the crystalline
structure. From left to right: schematic view of an individual molecule, a
unit cell, and a larger molecular aggregate emphasizing the smectic su-
perstructure of DDABM. The orientation of the alkyl chains was de-
duced from the characteristic peaks of the alkyl sub-lattice.
A characteristic feature of the discussed pattern is the
high intensity of far wide-angle peaks located on the first
and second layer lines, for example, the h40 and h11 reflec-
tions. This fact can be accounted for by the existence of a
sublattice formed by the octyl groups positioned in the tails.
The sublattice of the alkyl groups is a subunit of the main
lattice that shares reflections with it,[25] even if their symme-
tries are different. In this case, the sublattice (Figure 9) is
identified as a triclinic unit cell and is close to the lattice of
n-octane, apart from its c parameter.[26]
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Diacetylene-Containing Wedge-Shaped Compound
FULL PAPER
The indices of the sublattice and the corresponding main
lattice reflections are given in Table 1. Based on the WAXD
data, a sketch of a possible molecular packing in the crystal-
line phase of DDABM is proposed (Scheme 3). It is note-
worthy that the structure in Figure 9 highlights only the
alkyl part of the global unit cell such as sketched in
Scheme 3. The alkyl tails in Scheme 3 are shown as thick
cylinders. The b vector of the sublattice corresponds to the c
axis of the main lattice, while the ab plane of the sublattice
is parallel to the bc plane of the main lattice.
The projection of the sublattice a vector on the main lat-
tice ac plane corresponds to one-fourth of the main lattice b
vector. The c parameter of the sublattice is equal to approxi-
mately one-half of the a parameter of the main lattice. From
this fact, one can assume that the main lattice contains two
layers of quasi 2D “lamellar” arrays of the alkyl sublattice
along its a direction. The lattice parameters of the triclinic
sublattice are calculated to be a=4.23, b=4.85, c=19.71 ꢀ
and a=94.8, b=86.1, g=107.88. According to the proposed
model, the alkyl groups have a setting angle of about 608 in
the ab plane of the main lattice, while they are inclined by
about 158 toward the fast growth axis direction.
From the model depicted in Scheme 3, the inclination
angle of the straight diacetylene units can be estimated.
Thus, if one approximates the diameter of a diacetylene unit
by 2.3 ꢀ, it will be inclined by about 308 both towards the
fast growth axis and toward the b vector of the main lattice.
Therefore, the repeating distance of the diacetylene units
(i.e., d in Scheme 1) should correspond to the c parameter
of the main lattice of 4.85 ꢀ, which fulfills the requirements
for topochemical polymerization.
The thermal behavior in the temperature range of À158C
to 608C does not reveal any significant differences between
the polymerized and the unpolymerized materials, except
for a small variation in the transition temperatures, as
shown by temperature-dependent WAXD (Figure 10). On
heating DDABM samples which were previously annealed
at room temperature from À158C, both UV irradiated and
non-irradiated materials show a solid-state phase transition
at around 08C. The transition is characterized by a slight
change of the relative peak intensities of the sublattice re-
flections. Such a change in the relative intensities likely cor-
responds to a modification in the conformation of the alkyl
segments such as a change in the setting angles. Remarkably,
this transition is not accompanied by a thermal effect. More-
over, it coincides with the main exothermic event for the
quenched compound, as measured by DSC (Figure 4). The
observed low-temperature phase forms only on relatively
slow cooling from room temperature, whereas it does not
appear on fast cooling, as seen from Figure 10 (bottom).
Figure 10. Scattering intensity as a function of the modulus of the scatter-
ing vector s and temperature for DDABM measured during heating from
À158C to 608C at a rate of 5.0 KminÀ1. The results for samples annealed
at room temperature for 24 h before and after UV irradiation are given
in the top and middle panels, respectively. The bottom panel shows the
temperature-dependent structure evolution for a UV-irradiated sample
quenched from the isotropic melt to À208C.
spectroscopy, it can be polymerized under UV irradiation.
An oriented crystalline thin film of DDABM was obtained
on a silicon wafer substrate rubbed with polytetrafluoro-
ethylene and analyzed by grazing-incidence wide-angle X-
ray diffraction. Furthermore, the spherulites formed by
DDABM in thick films were investigated by wide-angle X-
ray diffraction measurements with a small X-ray beam.
DDABM was found to form a monoclinic crystalline lattice.
The main lattice contains two layers of quasi-2D arrays of
alkyl sublattice, which can be indexed to a triclinic unit cell,
close to the lattice of n-octane apart from its increased c pa-
rameter. A molecular packing model in the crystalline struc-
ture of DDABM was proposed on the basis of the X-ray dif-
fraction data, and it was found that the diacetylene units are
oriented along a defined lattice direction with a reticular
distance of 4.85 ꢀ, which fulfills the requirements for the
topochemical polymerization. UV polymerization does not
affect the phase behavior of the compound, but mainly
alters its optical properties.
Conclusion
A novel wedge-shaped compound containing two diacety-
lene tails, namely, methyl 3,5-bis(trideca-2,4-diyn-1yloxyl)-
benzoate (DDABM), was synthesized. As shown by UV/Vis
Chem. Eur. J. 2013, 19, 4300 – 4307
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X. Zhu, D. A. Ivanov et al.
C34H44O4 (516.32 gmolÀ1): C 78.08, H 8.60; calcd: C 79.03 , H, 8.58;
Experimental Section
1H NMR (400 MHz, CDCl3): d=0.815 (t, 9H; CH3), 1.21 (m, 30H,
ꢁ
CH3CH2), 1.44 (m, 9H, CH2), 2.12 (t, 6H, CH2C C), 4.25 (m, 2H,
Materials: Decyne (98%, Aldrich), N-bromosuccinimide (99%, Aldrich),
propargyl alcohol (99%, Aldrich), diethylamine, NH2OH·HCl, silver ni-
trate (ACS reagent, ꢀ99.0%, Aldrich), copper(I) chloride (ACS reagent,
ꢀ90%, Sigma-Aldrich), triphenylphosphine dibromide (96%, Aldrich),
methyl 3,5-dihydroxybenzoate (98%, Aldrich), potassium carbonate
(ACS reagent, ꢀ99.0%, Sigma-Aldrich), and 18-crown-6 (ꢀ99.0%, Al-
drich) were used as received. Acetone, dichloromethane, methanol, etha-
nol, ethyl acetate, n-hexane, sodium sulfate, sodium thiosulfate, sodium
chloride, and hydrochloric acid were purchased from VWR. The solvents
were purified by standard procedures.
ꢁ
COOCH2CH3) 4.72 (s, 6H, C CCH2O), 7.37 ppm (s, 2H, ArH ortho to
13
ꢁ
CO group); C NMR: 14.1 (CH3), 19.2 (CH2C ), 22.6 (CH3CH2), 28.3,
28.8, 29.1, 29.2, 31.9 (CH2), 57.8 (CH2O), 61.1 (CH2O), 61.2
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(COOCH2CH3), 64.4 (CH2C CC C), 69.9 (CH2C CC C), 71.9 (CH2C
ꢁ
ꢁ
ꢁ
CC C), 83.4 (CH2C CC C), 109 (ArC ortho to CO group), 126 (ArC
ipso to CO group), 141 (ArC in 4’-position relative to CO group), 151.4
(ArC in 3’,5’-positions relative to CO group), 165.8 ppm (COOCH2CH3).
Polymerization of DDABM: Quartz was cleaned by sonication in ace-
tone, water, and propan-2-ol for 2 min each, followed by drying in a
stream of nitrogen. A 10 gLÀ1 solution of DDABM was prepared in
chloroform. Films (200Æ5) nm thick were obtained by drop casting. Pho-
topolymerization was carried out by irradiation with a 6 W UV lamp at
254 nm at room temperature.
1-Bromo-1-decyne (1): A solution of decyne (10 g, 72.5 mmol), N-bromo-
succinimide (25.81 g, 145 mmol), and silver nitrate (3.815 g, 22.89 mmol)
in acetone (200 mL) was stirred at room temperature for 2 h. Acetone
was removed in vacuo, and the resulting product dissolved in CH2Cl2 and
passed through a short silica gel column. The solvent was removed on a
rotary evaporator to leave 1-bromo-1-decyne as a slightly yellow liquid.
Techniques: 1H NMR and 13C NMR spectra were recorded on a Varian
VXR 300 instrument at 300 MHz with TMS as internal standard in
CDCl3 solutions with concentrations of 15–30 mgmLÀ1
.
1
1
Yield: 14.86 g (94.5%), purity >98% by H NMR spectroscopy. H NMR
(400 MHz, CDCl3): d=0.815 (t, 3H, CH3), 1.21 (m, 10H, CH3CH2), 1.44
Polarized optical microscopy (POM) for thermo-optical analysis was per-
formed on a Carl Zeiss Axioplan 2 imaging polarizing microscope equip-
ped with a Mettler Toledo FP 82HT hot stage connected to a Mettler
Toledo FP 90 processor. The micrographs were recorded with a Carl
Zeiss AxioCam MRc digital camera.
(m, 2H, CH2), 2.12 ppm (t, 2H, CH2C C); 13C NMR: 14.1 (CH3), 19.6
ꢁ
ꢁ
ꢁ
(CH2C ), 22.6 (CH3CH2), 28.3, 28.8, 29.1, 29.2, 31.9 (CH2), 37.4 (C
ꢁ
CBr), 80.4 ppm (C CBr).
Trideca-2,4-diyn-1-ol (2): 1-Bromo-1-decyne 1 (23 g, 0.106 mol) in MeOH
(20 mL) was added dropwise to a stirred mixture of propargyl alcohol
(11.872 g, 0.212 mol), ethylamine (40 mL, aqueous solution, 70 wt%),
NH2OH·HCl (2 g), powdered CuCl (0.5 g), H2O (40 mL), and MeOH
(100 mL). Stirring was continued at 358C for 1 day. Afterwards, the reac-
tion mixture was filtered, and methanol was removed from the filtrate on
a rotary evaporator. The residue was extracted with diethyl ether. The or-
ganic layer was washed with water (3ꢃ30 mL) and then dried over anhy-
drous sodium sulfate, filtered, and concentrated on a rotary evaporator
to furnish the crude product. After column chromatography on silica gel
(eluent: ethyl acetate/n-hexane 1/5), 2 was obtained as a colorless crystal.
Yield: 9.38 g (86%), purity >98% by 1H NMR spectroscopy. 1H NMR
(400 MHz, CDCl3): d=0.815 (t, 3H; CH3), 1.21 (m, 10H, CH3CH2), 1.44
Raman spectra were measured on a Bruker RFS 100/S with Nd:YAG
laser (l=1064 nm) and 500 scans.
Size exclusion chromatography (SEC) was carried out with a high-pres-
sure liquid chromatography pump (ERC HPLC 6420) and a refractive-
index detector (Jasco RI-2031 plus) at 258C. The eluting solvent was
THF, and a flow rate of 1.0 mL·minÀ1 was used. Four columns with SD-
plus gel were employed. The length of each column was 300 mm, and the
diameter was 8 mm. The diameter of the gel particles was 5 mm, and the
nominal pore widths were 50, 100, 1000 and 10000 ꢀ. Calibration with
polystyrene standards was used to determine the molecular weights.
Differential scanning calorimetry (DSC) measurements were performed
with a Netzsch DSC 204 unit. Samples (typical weight: 5 mg) were en-
closed in standard Netzsch 25 mL aluminum crucibles. Indium and palmit-
ic acid were used as temperature calibration standards. The employed
heating and cooling rates were 5.0 KminÀ1. For quenching, a cooling rate
of 40 KminÀ1 was used.
ꢁ
ꢁ
ꢁ
(m, 2H, CH2), 2.12 (t, 2H, CH2C C), 4.25 ppm (C CC CCH2OH);
13
ꢁ
C NMR: 14.1 (CH3), 19.2 (CH2C ), 22.6 (CH3CH2), 28.3, 28.8, 29.1,
ꢁ
ꢁ
ꢁ
ꢁ
29.2, 31.9 (CH2), 49.9 (CH2OH), 64.3 (CH2C CC C), 70.9 (CH2C CC
C), 73.4 (CH2C CC C), 81.9 ppm (CH2C CC C).
ꢁ
ꢁ
ꢁ
ꢁ
1-Bromotrideca-2,4-diyne (3): Compound 2 (1.75 g, 9.1 mmol) in dry di-
chloromethane (6 mL) was added dropwise to an ice-cooled stirred solu-
tion of PPh3Br2 (4.58 g, 10.5 mmol) in dry dichloromethane (40 mL).
After stirring at the same temperature for 10 min, the reaction mixture
was warmed to room temperature and stirring continued for 1 day. After-
wards dichloromethane was removed and the reaction mixture was dilut-
ed with ethyl acetate. The organic layer was washed with sodium thiosul-
fate (10% solution, 2ꢃ30 mL), water (3ꢃ30 mL), and dried over anhy-
drous Na2SO4. The solvent was removed on a rotary evaporator. The
crude product thus obtained was purified by column chromatography on
silica gel (eluent: ethyl acetate/n-hexane 2/1) to yield 1.86 g (82%) of 3
as a white power, purity> 98% by 1H NMR spectroscopy. 1H NMR
(400 MHz, CDCl3): d=0.815 (t, 3H, CH3), 1.21 (m, 10H, CH3CH2), 1.44
UV/Vis spectra were recorded on the films of the samples at room tem-
perature on
a JASCO V-630 spectrophotometer at a scan rate of
100 nmminÀ1. The slit width was 2 nm. Prior to drop casting of the quartz
substrates, the stock 10 gLÀ1 chloroform solutions of the compounds
were filtered through 0.2 mm PTFE syringe filters. UV irradiation was
carried out with a 6 W UV lamp (Netz-Handlampe UVA/C, Dr. Grçbel
UV-Elektronik GmbH) at 254 nm placed at a distance of 5 cm from the
films.
Wide-angle X-ray diffraction (WAXD) experiments at variable tempera-
tures were conducted at the BM26 beamline of the European Synchro-
tron Radiation Facility (ESRF) in Grenoble, France, by using X-ray pho-
tons with energy of 12 keV. A small amount of DDABM was enveloped
in a polished aluminum foil for good heat contact and annealed for 24 h
at room temperature. The temperature of the sample was controlled by
using a Linkam heating stage adapted for X-ray experimentation. The
2D X-ray patterns were collected in transmission geometry by a 2D
Frelon CCD with 2ꢃ2 binning giving a pixel resolution of 100 mm in both
lateral directions.
ꢁ
ꢁ
ꢁ
(m, 2H, CH2), 2.12 (t, 2H, CH2C C), 3.89 ppm (s, 2H, C CC CCH2Br);
13
ꢁ
C NMR: 14.1 (CH3), 19.2 (CH2C ), 22.6 (CH3CH2), 28.3, 28.8, 29.1,
ꢁ
ꢁ
ꢁ
ꢁ
29.2, 31.9 (CH2), 14.8 (CH2Br), 64.4 (CH2C CC C), 69.9 (CH2C CC C),
71.9 (CH2C CC C), 83.4 ppm (CH2C CC C).
ꢁ
ꢁ
ꢁ
ꢁ
Methyl 3,5-bis (trideca-2,4-diyn-1yloxyl)benzoate (DDABM): K2CO3
(1.08 g, 1 mmol) and 18-crown-6 (2.6 mg, 0.01 mmol) were added to a
stirred solution of methyl 3,5-dihydroxybenzoate (0.5 g, 2.5 mmol) and 3
(2.55 g, 6.25 mmol) in acetone (40 mL). The reaction mixture was heated
to reflux for 24 h, and then filtered and evaporated to dryness. Water
(50 mL) was added and the mixture was extracted with CH2Cl2 (3ꢃ
30 mL). The organic phases were combined, dried over Na2SO4, and the
solvent evaporated in vacuo. The crude product thus obtained was puri-
fied by column chromatography on silica gel (eluent: ethyl acetate/n-
hexane 3/1) to afford DDABM as a white powder. Yield: 0.88 g (68%),
Grazing-incidence wide-angle X-ray diffraction (GIWAXD) measure-
ments were performed at the X6B beamline of the National Synchrotron
Light Source (NSLS) at the BNL, Brookhaven. The used X-ray photons
had an energy of 18 keV. The compounds were dissolved in chloroform
to give 0.01 wt% solutions and drop cast on the PTFE-rubbed silicon
wafer substrate followed by an annealing process at 258C for 24 h. The
drop-cast samples were placed in a six-circle Huber 5020 diffractometer
with vertical scattering geometry. The samples were oriented with the
rubbing direction parallel and perpendicular to the incident X-ray beam.
1
purity >98% by H NMR spectroscopy. Elemental analysis (%) calcd for
4306
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ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4300 – 4307

Diacetylene-Containing Wedge-Shaped Compound
FULL PAPER
The 2D diffraction patterns were collected by using a Princeton Instru-
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Acknowledgements
The financial support by German Research Foundation and French
Agence Nationale de la Recherche (DFG-ANR project “T2T”, MO 628/
13-1 and IUPAC project, PAC-PAL-10-02-26) is gratefully acknowledged.
L. L. thanks the Chinese Scholarship Council for the financial support.
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Received: September 11, 2012
Revised: December 5, 2012
Published online: January 24, 2013
Chem. Eur. J. 2013, 19, 4300 – 4307
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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