Generation of liquid crystallinity from a Td-symmetry central unit

Article abstract of DOI:10.1039/c6sm01019a

A series of new columnar liquid crystals containing an adamantane central unit with its four bridgehead positions partially or fully decorated with different numbers (1-4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups were designed and investigated carefully to explore the structure-property correlations. The molecular structures and mesomorphic properties of the DLCs were characterized by ¹H-NMR, ¹³C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives. No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited a rectangular columnar phase, which switched to a square columnar phase possessing a wide temperature range. Similarly, a hexagonal columnar mesophase was observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized 1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.

Full text of DOI:10.1039/c6sm01019a

View Article Online
View Journal
Soft Matter
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. M. Sayed, B. Lin
and H. Yang, Soft Matter, 2016, DOI: 10.1039/C6SM01019A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/softmatter

Please do not adjust margins
Soft Matter
Page 1 of 10
View Article Online
DOI: 10.1039/C6SM01019A
Soft Matter
ARTICLE
Generation of Liquid Crystallinity from a Td-Symmetry Central Unit
Sayed Mir Sayed, Bao-Ping Lin, and Hong Yang*
Received 00th January 20xx,
Accepted 00th January 20xx
A series of new columnar liquid crystals containing an adamantane central unit with the four bridgehead positions partially
or fully decorated with different numbers (1 - 4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups, were designed and
investigated carefully to explore the structure-property correlations. The molecular structures and mesomorphic
properties of the DLCs were characterized by 1H-NMR, 13C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the
mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives.
No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were
observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups
at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited rectangular columnar phase which
switched to square columnar phase with a wide range of thermal stability. Similarly, hexagonal columnar mesophase was
observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized
1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.
DOI: 10.1039/x0xx00000x
www.rsc.org/
such as benzene, pyridine, triazine, triphenylene,
diazatriphenylene, hexaazatriphenylene, dibenzonapthacene,
pyrene, tristriazolotriazine, rufigallol, etc.2,16-20
Introduction
Discotic Liquid Crystals (DLCs) have attracted the attention of many
Adamantane molecule has a rigid tetrahedral Td-symmetry
which is made up of four cyclohexane rings fused in chair
conformation. It has two equivalent sites, the bridge and
bridgehead positions, its polycyclic cage is similar to that of the
unit cell of diamond crystal lattice with an almost identical
carbon-carbon bond length corresponding to 1.54Å.21,22
Adamantane derivatives are ideal candidates for various
researchers due to their extraordinary physical properties since the
first discovery in 1977.1 Owing to the long-range self-assembling,
ease of processing, solubility in a variety of organic solvents, and
high charge-carrier mobilities along the stacking axis has made DLCs
ideal candidates for organic semiconductor device applications.2-11
The ability of a molecule to exhibit a particular mesophase
is closely related to its shape, dipolar property, aspect ratio,
conformational dynamics, and specific intermolecular
associations.12 Disc-shaped molecules generally self-assemble
into columnar phases, while rod like molecules often display
nematic or smectic phases. A discotic mesogen generally
comprises a central rigid organic core (aromatic or non-
aromatic) functionalized by a number of flexible peripheral
chains. These molecules are known to pack in one dimensional
column in their mesophases,13 and exhibit different
symmetries like hexagonal columnar (Colh), rectangular
columnar (Colr), square columnar (Cols), columnar oblique,
columnar plastic, columnar lamellar, nematic columnar and
columnar helical phases.14,15 Interestingly, by changing the
temperature range, columnar mesophases may transform
from one mesophase symmetry to another.15 Most of the core
structures that form DLCs are Cn-symmetry planar molecules,
applications,
such
as
catalysis,23,24
supramolecular
chemistry,25,26 surface functionalization,27,28 biocompatible
surface tailoring,29,30 and materials science.31-33 From liquid
crystallinity perspective, adamantane is a perfect rigid core for
the design of DLC molecules. To our surprise, although few
works have been done on adamantane-based calamitic LCs,34-
39
adamantane-core DLCs have never been reported so far.
Most importantly, such a Td-symmetry structure brings us a
precious opportunity to grow one-dimensional, two-
dimensional or three-dimensional flexible peripheral chains
selectively from one to four of its bridgehead positions, to
study the structure-property correlations of bridgehead
substituted adamantane derivatives with respect to the
columnar mesophase self-assembly, which is the key objective
of this work.
Herein, we describe the application of rigid adamantane
core in the synthesis of DLCs. For comparison, DLCs of
different mesophase symmetry were obtained by partially or
fully functionalizing the four bridgehead positions of
adamantane ring with different numbers (1 - 4) of 3,4,5-
tris(dodecyloxy)phenyl groups (Fig. 1). Colh, Colr and Cols
phases were discovered and their mesomorphic properties
were investigated in detail.
School of Chemistry and Chemical Engineering, Jiangsu Province Hi-Tech Key
Laboratory for Bio-medical Research, Jiangsu Optoelectronic Functional Materials
and Engineering Laboratory, Southeast University, Nanjing, 211189, China
E-mail: yangh@seu.edu.cn
Electronic Supplementary information (ESI) available: [It contains DSC, XRD and
UV-vis spectroscopic data of ADLCs]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 2 of 10
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
Journal Name
commercially available, a little work has been contributed to
the syntheses of di-, tri- and tetra- carboxyl derivatives so far.
Moreover, the activation of C-H or C-OH bonds of the
adamantane needs harsh conditions like the use of fuming
nitric acid and fuming sulfuric acid. We synthesized
adamantane 1,3-di- and 1,3,5-tri- carboxylic acids by following
the literature protocols as shown in Scheme 1.31,46 Their
structures were characterized by NMR spectroscopy and used
for further reactions. 1,3,5,7-Adamantane tetracarboxylic acid
was received as a gift from Prof. Qiu.47
Results and Discussion
To get a complex architecture containing adamantane scaffold,
it is necessary to functionalize adamantane unit at different
bridgehead positions. However, the syntheses of bridgehead
tri- and tetra-substituted adamantanes are challenging,
because of steric and electronic peculiarities.40-44 Moreover,
adamantane derivatives are highly symmetrical molecules that
can incorporate various and multifunctional substituents at the
periphery to give different symmetries.45 As shown in Fig. 1,
we chose carboxyl derivatives to prepare adamantane-core
DLCs. Although the adamantane mono-carboxylic acid is
Fig. 1 Adamantane functionalization and its application to syntheses of adamantane-core DLCs.
With four adamantane carboxylic acids in hand, we chose and reduction of 1,2,3-trihydroxybenzene. To get carbonyl
3,4,5- tris(dodecyloxy)-benzenamine as the flexible peripheral chloride derivatives of adamantane, mono-, di-, tri- and tetra-
chain decorations. Scheme 1 summarizes the adamantane carboxyl derivatives of adamantane were refluxed in thionyl
functionalizations and DLCs syntheses. Following literature chloride from 2 - 24 hours, depending on the number of
protocols,48 3,4,5-tris(dodecyloxy)-benzenamine (compound
was successfully prepared by successive alkoxylation, nitration number of substituents. The obtained carbonyl chloride
4)
substituents. Refluxing time increased with increase in the
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 3 of 10
Journal Name
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
derivatives of adamantane were treated with 3,4,5- allowed it to cool to 176 0C at a rate of -1 0C/min, and kept for
tris(dodecyloxy)-benzenamine to get the desired DLCs.
5-6 hours. After this period, a beautiful focal conic texture with
elongated stripes was observed, as shown in Fig. 2A.
Fig. 2 Polarized optical microscope (POM) textures of A) ADLC2 at 176 0C, and B) ADLC3
at 155 0C.
ADLC3
which
has
three
flexible
3,4,5-
tris(dodecyloxy)phenyl carbamoyl tails attached on 1,3,7-
positions exhibited LC phase from room temperature on
heating. A typical pseudo focal conic fan-shaped texture was
obtained on cooling from isotropic phase at the rate of -1
0C/min, as shown in Fig. 2B. Interestingly, ADLC4 which has
four flexible groups attached on 1,3,5,7-positions did not show
any mesomorphic phase, but a crystalline spherulite texture.
To get the exact transition temperatures and associated
enthalpy changes, DSC studies were performed at the scanning
Scheme 1 Synthetic routes of adamantane core DLCs. Reagents and conditions: a)
C12H25Br, K2CO3, DMF, 90 0C, 24 h. b) NaNO2, HNO3, H2O, CH2Cl2. RT, 3h. c) Hydrazine,
Graphite, EtOH, 24 h, 110 0C. d) SOCl2, reflux, 2 h. e) CH2Cl2, Et3N, 4, RT, overnight. f)
H2SO4, HNO3, HCOOH, RT, overnight. g) SOCl2, reflux, 4 h. h) CH2Cl2, Et3N, 4, RT,
overnight. i) Oleum, HNO3, HCOOH, RT, overnight. j) SOCl2, reflux, 20 h. k) CH2Cl2, Et3N,
4, RT, 24 h. l) SOCl2, reflux, 24 h. m) CH2Cl2, Et3N, 4, RT, 24 h.
0
rate of 10 C/min. DSC data is summarized in Table 1, which is
in the closed agreement with POM studies. ADLC1 and ADLC4
showed one thermal peak/transition on the first cooling as
well as on the second heating (Fig. S2), which indicated the
absence of any mesomorphic properties. Enthalpy changes for
the endothermic transition of ADLC1 and ADLC4 appeared as
15.52 J/g and 90.13 J/g, respectively.
1
The resulting products were characterized by HNMR, 13C
NMR and IR spectroscopy. Thermotropic liquid crystalline
properties of ADLCs 1-4 were investigated by polarized optical
microscope (POM) and differential scanning calorimetory
(DSC). The mesophase symmetries of ADLC 2-3 were further
studied by Wide Angle X-ray Scattering (WAXS). It was found
that mono- and tetra-substituted adamantane derivatives
Table 1 Phase transition temperatures (0C) and the corresponding enthalpies (J/g) of
ADLCs (1-4):
ADLC
Heating
Cooling
(
ADLC1
tri- substituted derivatives (ADLC2
organized columnar self-assembly.
,
ADLC4) did not show any mesophases, while di- and
1
Cr 60.46 (15.52) → Iso
Iso → Cr 22.31 (36.82)
,
ADLC3) exhibited well
2
Cr 60.29 (20.43) → Colr 73.28
(9.93) → Cols 185.37 (17.54)
→ Iso
Iso → Cols 178.59 (14.63) →
Colr 66.63 (10.06) → Cr 54.4
(21.36)
Initially POM was used to study the liquid crystalline
properties of all the synthesized ADLCs 1-4. On heating from
0
35 C ADLC1 which has only one 3,4,5-tris(dodecyloxy)phenyl
3
4
Cr 15.12 (34.29) → Colh
163.79 (7.156) → Iso
Cr 57.65 (90.13) → Iso
Iso → Colh 157.68 (7.67) →
Cr 9.11 (34.75)
carbamoyl flexible group attached on C-1 position, did not
exhibit any fluid LC phase neither on heating nor on cooling.
ADLC2, which has two 3,4,5-tris(dodecyloxy)phenyl carbamoyl
Iso → Cr 22.59 (77.36)
Note. Peaks temperatures in the DSC thermograms obtained during the second
flexible chains attached on C-1,3 positions, exhibited two heating and first cooling cycles at 10 °C/min.
mesomorphic phases. First was a short thermal phase while
0
second was a quite long range phase observed between 73 C
0
0
and 185 C. On cooling from isotropic phase at -1 C/min, we
observed some irregular textures. To get characteristic
0
columnar textures, we filled ADLC2 in a LC cell at 190 C and
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 4 of 10
View Article Online
DOI: 10.1039/C6SM01019A
Soft Matter
ARTICLE
Fig. 3 (A) DSC thermogram of ADLC2. (B) WAXS profile depicting the intensity against 2θ obtained for the Colr phase of ADLC2 at 65 0C. (C) WAXS profile depicting the intensity
against 2θ obtained for the Cols phase of ADLC2 at 150 0C. (D) DSC thermogram of ADLC3. (E) WAXS profile depicting the intensity against 2θ obtained for the Colh phase of ADLC3
at 120 0C. (F) Bar graph summarizing the thermal behavior of ADLCs 1-4.
thermal peaks on the heating-cooling cycle, which confirmed
ADLC2 and ADLC3 exhibited mesomorphic states over a the mesomorphic state. ∆H value comes out as 7.15 J/g. The
large temperature ranges. It is worth mentioning here that decrease in clearing point and ∆H values of ADLC3 is probably
number of peripheral flexible tails greatly influenced the liquid due to the steric hindrance of surrounding flexible tails that
crystalline properties. ADLC3 with more number of side tails make mesophase less stable. Representative DSC
exhibited mesomorphic state from room temperature upon thermograms of ADLC2 and ADLC3 are shown in Fig. 3A and D,
heating, while ADLC2 with less number of flexible tails showed respectively.
0
LC phase over relatively higher temperature range 60-185 C.
In order to get further insight into the mesophase
Similarly, the isotropization temperature (Tiso) is also geometry, powder XRD studies have been performed for
influenced accordingly. ADLC2 and ADLC3 have higher values ADLC2 and ADLC3. The results are summarized in Table 2.
of Tiso than ADLC1 and ADLC4. This increase in the Tiso might be ADLC2 which has two mesophases as per the DSC transitions
explained in term of hydrogen bonding between the amide was subjected to XRD analysis at different temperatures. The
groups of mesogens which give extra stability to the wide angle X-ray scattering (WAXS) diffraction pattern at 65 0C
mesophase.49-53On the first cooling and the second heating (Fig. 3B) shows one strong reflection at 43.7 Å, together with
scans, ADLC2 exhibited three thermal transition peaks (Fig. two weak reflections at 23.86 Å and 21.53 Å with reciprocal d-
3A), which confirmed two LC phases. First mesomorphic phase spacing ratio 1:1.8:2. These peaks are indexed 100, 110, and
0
existed over short thermal range 60-73 C with ∆H=9.93 J/g. 020, respectively. The values of the lattice parameters “a” and
The second phase existed over a long temperature range 73- “b” comes out as 43.7 Å and 28.48 Å, respectively. These
0
185 C with ∆H=17.54 J/g. ADLC3 showed two characteristic values were found according to the literature procedure for
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 4
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 5 of 10
Journal Name
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
Colr mesophases.54 On the basis of the above calculations; we 4.55 with d-spacing 27.2 Å and 19.4 Å, respectively. These
0
conclude that the mesophase at 65 C has columnar phase peaks are indexed as 100, 110 and 020, respectively. The
with a rectangular symmetry. Next to the small angle region a reciprocal d-spacing ratio appears as 1:√2:2, confirming a
broad halo is observed at 2θ = 10o - 17o, is assigned to the square symmetry. The value of lattice parameter “a”
molten alkyl chains. Two diffused peaks are also observed in calculated for all the three reflections in small angle region
the WAXS region at 3.67 Å and 3.31 Å. These peaks should appear as 38.7 Å, 38.5 Å, and 38.8 Å, respectively. The average
come from the correlation between peripheral alkyl chains and value is 38.7 Å. These calculations prove that the mesophase
core-core stacking of the adjacent adamantane units, exists after the second transition in DSC thermogram is square
respectively.
columnar phase. Next to the small angle region a broad halo is
To find the mesophase nature and geometry of the second observed at 2θ = 10o - 17o, which should be referred to molten
transition in DSC thermogram of ADLC2, WAXS pattern at 150 alkyl chains. Two diffuse peaks are also observed in the WAXS
0C was studied. One can see from the WAXS diffractogram (Fig. region at 3.6 Å and 3.3 Å. These peaks arise from the
3C) that small angle region has three peaks. The intense peak correlation between side alkyl chains and core-core stacking of
appears at 2θ value 2.28 with d-spacing 38.7 Å, and the other the adjacent adamantane units.
two peaks with low intensities appear at 2θ values 3.24 and
Table 2 Results of (hkl) indexation of XRD profiles of ADLC2 and ADLC3 at a given temperature (T) of mesophases:
Compounds (D/ Å)
Phase (T/0C)
d-spacing (Å)
Mesophase
Colr
Miller Indices
Lattice Parameter (Å)
Molar Volume (Å)3
Lattice Area S (Å)2
(khl)
ADLC2 (52.4)
65
43.7
23.86
100
110
020
a=43.7, b=28.48
c=3.31, S= 1244.576
V=4119.547
21.53
3.67 (ha)
3.31 (hc)
n=1.7
ADLC2 (52.4)
150
120
38.7
27.2
Cols
100
110
020
a=38.7
c=3.3, S=1497.69
V=4942.377
n=2
19.4
3.6 (ha)
3.3 (hc)
ADLC3 (49.64)
37.7
21.8
Colh
100
110
200
a=43.5
c=3.29, S=1638.737
V=5391.4433
n=1.5
18.5
3.65 (ha)
3.29 (hc)
Diameter (D) of the disk (estimated from Chem 3D Pro 12.0 molecular model software from Cambridge Soft). d: spacing deduced from Bragg’s equation; c is height of
the unit cell. The spacing marked ha and hc correspond to diffused reflections in the wide-angle region arising from correlations between the alkyl chains and core
regions, respectively. “n” indicates the average number of molecules per columnar slice of thickness, hc estimated from the lattice area S and the volume V.
ADLC3 showed a characteristic intense peak in the small peaks are also observed in the WAXS region at 3.65 Å and 3.29
angle region at 2θ value 2.34 with d-spacing 37.7 Å along with Å. These peaks should also come from the correlation between
two small peaks with d-spacing 21.8 Å and 18.5 Å. The peripheral alkyl chains and core-core stacking of the adjacent
reciprocal d-spacing ratio comes out 1:√3:2, which matches adamantane units.
the literature values for Colh phase.55 Moreover, a single (intensity vs 2θ) of ADLC3 is shown in Fig. 3E. Fig. 3F
intense reflection in the small angle region and the absence of summarizes the thermal behaviors of ADLCs 1-4
expected multiple low intensity peaks can also satisfy the One can calculate the average number of molecules (n) per
A representative XRD diffractogram
.
hexagonal columnar symmetry.56 These peaks in the small columnar disc/slice by the formula, n = ρ × NA × V/Mw,57
angle region are indexed 100, 110 and 200. The value of lattice where “ρ” stands for density, NA is Number of Avogadro, V is
parameter “a” calculated is 43.5 Å. These observations satisfy volume and Mw is molecular weight. V = S × hc, where S is the
a hexagonal symmetry for ADLC3, and we can say that ADLC3 lattice area and hc is core-core stacking distance. One can
has hexagonal columnar mesophase symmetry. Next to the calculate S by the formula S = (abc × sinγ), where abc are the
small angle region a broad halo is observed at 2θ = 10o - 17o, cell parameters and γ is the angle of the mesophase symmetry.
which should come from the molten alkyl chains. Two diffuse For rectangular and square system γ = 90, while for hexagonal
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 6 of 10
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
Journal Name
system its value is 60. ρ for organic materials is generally
assumed as 1.0 g cm-3. Detail of XRD analysis is given in Table
2.
Typically, 3,4,5-tris(dodecyloxy)-benzenamine is an ideal
candidate to induce columnar liquid crystallinity in a molecule
if attached to a proper-sized nucleus. ADLC1 which has only
one flexible 3,4,5-tris(dodecyloxy) phenyl carbamoyl group at
position C-1, does not exhibit any mesophase, it may be
because of the high rigid nature of adamantane which
maintains its crystallinity in ADLC1. In addition, ADLC4 which
has fully functionalized tetrahedral adamantane nucleus also
loses LC properties. We assume that, tetrahedral arrangement
of surrounding groups in 3-dimensional pattern destabilize the
discs to arrange themselves in 1-dimensionalcolumnar
packing. ADLC3 has three flexible groups at C-1,3,5 positions in
a planner arrangement. Such arrangement is an ideal condition
for one dimensional columnar packing. It is the reason that
ADLC3 has a perfect hexagonal columnar mesophase, as
shown in Fig. 4A. To understand the mesomorphic behaviors
of ADLC2 which exhibits two different columnar phases (Colr
and Cols), we propose a hypothesis as schematically illustrated
in Fig. 4B. At low temperature ADLC2 mesogens with a
notched-disc-like shape may arrange themselves in side-by-
side packing in the form of rectangular columnar self-assembly,
at high temperature the notched discs might tilt and slide over
one another to give more stable edge-side interaction of the
discs in the form of square columnar packing. This scenario
might be very similar to the well-known Smectic A-to-Smectic
C phase transition of calamitic mesogens which is also driven
by the tilt action of molecules.
Fig. 4 Schematic illustration of (A) hexagonal packing of columns in ADLC3, and (B)
reversible thermal switching of Colr and Cols phases in ADLC2.
Experimental Section
General Consideration
All reagents and solvents were purchased from commercial
suppliers and used without further purification. Solvents were
distilled from CaH2 and stored. All non-aqueous reactions were
conducted in oven-dried glasswares, under a dry nitrogen
1
atmosphere. All H NMR and 13C NMR spectra were obtained
on Bruker HW300 MHz spectrometer (AVANCE AV-300) and
recorded in CDCl3 or DMSO-d6 while using TMS as an internal
standard. Olympus BX53P microscope with a Mettler PF82HT
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 7 of 10
Journal Name
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
hot stage was used to observe the liquid crystals textures of suspended particles. Solvent was removed under reduced
DLCs. DSC studies were performed on TA Q100 instrument pressure and the crude product was recrystallized from glacial
under nitrogen purge at a heating rate of 10 °C/min from −40 acetic acid to provide 1,3,5-adamantanetricarboxylic acid as a
to +220 °C. UV-vis spectra were recorded in methylene white solid (0.109 g, yield: 14.97%). 1H-NMR (300 MHz,
chloride on TU-1810 ultraviolet-visible spectrophotometer DMSO):
(UV/vis spectrometer) (Beijing Purkinje General Corp., China). H).
Fourier transform infrared (FT-IR) spectra were obtained on a
ꢀ (ppm) = 12.25 (3H, s, COOH), 1.71-2.17, adamantane
Nicolet 5700 FT-IR spectrometer. X-ray scattering experiments
were performed on a high-flux small angle X-ray scattering
instrument (SAXSess, Anton Paar) equipped with Kratky block-
collimation system and a temperature control unit (Anton Paar
TCS300).
Synthesis of ADLC1
1-Adamantanecarboxylic acid (1.000 g, 5.548 mmol) was
dissolved in thionyl chloride (10.0 mL, SOCl2) at 0 0C and
refluxed at 75 0C for 2 hours. The obtained solution was cooled
to room temperature and concentrated under reduced
pressure. The obtained oily residue was put in vacuum
desiccator for one hour. 3,4,5-Tris(dodecyloxy)-benzenamine
Synthesis
General synthetic procedure along with characterization data (3.584 g, 5.548 mmol) was added to a schlenk flask and
for the known precursors and ADLCs 1-4 is given below. 3,4,5- degassed multiple times. Dry dichloromethane (20.0 mL) was
Tris(dodecyloxy)-benzenamine (compound
by following the literature protocol.48
4
) was synthesized injected through a syringe into the schlenk flask and stirred at
room temperature. After getting a clear solution, Et3N (0.70
ml, 7.20 mmol) was added as a catalyst. Acid chloride was
dissolved in 5.0 mL of dry dichloromethane and injected in the
stirring solution. Dense fumes appeared inside the schlenk
Synthesis of 1,3-adamantanedicarboxylic Acid
1,3-Adamantanedicarboxylic acid was synthesized by following
the literature protocol.58 1-Adamantanecarboxylic acid (1.000
g, 5.548 mmol) was added to sulphuric acid (7.5 mL, 98%),
which was then stirred at room temperature for sufficient time
to get a clear solution. To the obtained acid solution, fuming
nitric acid (0.5 mL) was added while stirring vigorously and
kept on stirring for one hour. It is important to mention that
flask, indicating a quick reaction. This mixture was stirred
overnight at room temperature. The reaction mixture was
concentrated under reduced pressure, extracted with ethyl
acetate, washed with water and brine. The organic layer was
dried over anhydrous MgSO4, filtered and concentrated. The
crude product was purified on silica gel column, using
petroleum ether and ethyl acetate (20:1) as eluting solvents. A
sticky solid was obtained, which was dried in vacuum
desiccator over P2O5 overnight to provide ADLC1 as a light
brown solid (3.223 g, yield: 71.86 %). 1H-NMR (300 MHz,
0
solution temperature must be kept below 25 C. After one
hour stirring, formic acid (12.0 mL, 100%) was added drop wise
during 30 minutes. After the addition of formic acid, the
mixture was allowed to stir for 12 more hours at RT. The
mixture was poured on crushed ice (ca. 40 g) and filtered. The
filtrate was recrystallized from glacial acetic acid to provide
1,3-adamantanedicarboxylic acid as a white solid (0.341 g,
CDCl3):
ꢀ (ppm) = 0.88 (9H, t, J = 6 Hz, CH3), 1.26 (48H, m,
C8H16), 1.44 (6H, m, CH2), 1.73 (6H + 6H, m, CH2, adamantane H
), 1.95 (6H, d, J = 3 Hz, adamantane H), 2.1 (3H, m,
adamantane H), 3.89 (2H, t, J = 6 Hz, OCH2), 3.95 (4H, t, J = 6
Hz, OCH2), 6.82 (2H, s, ArH), 7.16 (1H, s, NH). 13C-NMR (75
1
yield: 27.41%). H-NMR (300 MHz, DMSO): ꢀ (ppm) = 12.08
(2H, s, COOH), 1.61-2.06, adamantane H).
MHz, CDCl3):
ꢀ (ppm) = (14.08, 22.67, 26.07, 26.14, 28.15,
29.35, 29.39, 29.63, 29.69, 29.74, 30.28, 31.92, 36.44, 39.33,
41.55, 69.15, 73.49, 76.57, 76.99, 77.42, 98.88, 133.06, 153.19,
Synthesis of 1,3,5-adamantanetricarboxylic acid
175.63). IR (KBr, cm-1):
⊽ = 3326, 2922, 2852, 1649.
1,3,5-Adamantanetricarboxylic acid was prepared according to
the literature procedure.31 1,3,5-Trihydroxyadamantane (0.500
g, 2.714 mmol) was added in portions into pre-cooled oleum
(22.0 mL, 20%). The resulting suspension was stirred vigorously
Synthesis of ADLC2
0
ADLC2 was synthesized as per the procedure for ADLC1 and
was purified by silica gel column using petroleum ether and
ethyl acetate (10:1) as eluting solvents. A sticky solid was
obtained, which was dried in vacuum desiccator over P2O5
for 20 minutes at 0 C. The mixture was heated in water bath
up to 55 0C to get a clear light yellow solution. To this solution,
formic acid (8.0 mL, 100%) was added drop wise under
extensive stirring during 30 minutes. It’s worth mentioning
here that an outlet must be available to exhaust the rapid
production of CO from the reaction mixture and the addition
of formic acid must be slow. After the addition of formic acid,
the mixture was further stirred for two more hours at given
temperature and then cooled to room temperature, and kept
on stirring overnight. The resulting solution was poured on
crushed ice (ca. 250 g) and kept in a refrigerator for 5 hours.
The crystalline precipitate formed was filtered, washed with
overnight to provide ADLC2 as a light brown solid (1.113g,
1
yield: 67.37 %). H-NMR (300 MHz, CDCl3):
ꢀ (ppm) = 0.88
(18H, t, J = 6 Hz, CH3), 1.26 (96H, m, C8H16), 1.44 (12H, m, CH2),
1.75 (12H + 2H, m, CH2, adamantane H), 1.97 (8H, m,
adamantane H), 2.16 (2H, s, adamantane H), 2.32 (2H, m,
adamantane H), 3.90 (4H, t, J = 6 Hz, OCH2), 3.95 (8H, t, J = 6
Hz, OCH2), 6.82 (4H, s, ArH), 7.21 (2H, s, NH). 13C-NMR (75
MHz, CDCl3):
ꢀ (ppm) = (14.08, 22.67, 26.07, 26.14, 28.23,
0
29.35, 29.37, 29.40, 29.64, 29.69, 29.74, 30.29, 31.92, 35.32,
38.44, 40.36, 42.10, 69.15, 73.50, 76.57, 77.00, 77.42, 98.95,
ice cold water, and put in oven at 100 C overnight. It was
further dissolved in acetone and filtered to remove the
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 8 of 10
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
Journal Name
133.27, 134.86, 153.22, 174.75). IR (KBr, cm-1):
2853, 1649.
⊽ = 3331, 2920,
Conclusions
A series of new adamantane core columnar liquid crystals
were synthesized by functionalizing adamantane ring at
different bridgehead positions. Their molecular structures
were characterized by 1H NMR, 13C NMR, IR and UV
spectroscopy. Their mesophases were investigated by POM,
DSC and XRD. It was found that mesophase symmetry
depended on number of peripheral chains attached to the
central adamantane unit. Our work revolves around the
tetrahedral adamantane unit to examine the structure-
property correlation. With one side tails no mesophase was
observed, while two mesophases were observed for the
adamantane core with two flexible groups at 1,3-positions. A
transition from rectangular columnar mesophase to square
columnar phase was investigated for ADLC2. Rectangular
columnar phase was observed over short thermal range while
square columnar phase existed over wide temperature range
Synthesis of ADLC3
1,3,5-Adamantanetricarboxylic acid (0.100 g, 0.373 mmol) was
0
dissolved in thionyl chloride (10.0 mL) at 0 C and refluxed at
0
75 C for 20 hours. The obtained solution was cooled to room
temperature and concentrated under reduced pressure. The
obtained oily residue was put in vacuum dissector for one
hour. (0.72 g, 1.12 mmol) of 3,4,5-tris(dodecyloxy)-
benzenamine was added to a schlenk flask and degassed
multiple times. Dry dichloromethane (10.0 mL) was injected
through a syringe into the schlenk flask and stirred at room
temperature. After getting a clear solution, Et3N (0.2 mL, 1.34
mmol) was added as a catalyst. Acid chloride was dissolved in
5 ml of dry dichloromethane and injected in the stirring
solution. This mixture was stirred for 24 hours at room
temperature. The reaction mixture was concentrated under
reduced pressure, extracted with dichloromethane, washed
with water and brine. The organic layer was dried over
anhydrous MgSO4, filtered and concentrated. The crude
product was purified by silica gel column. Purification was
done in two steps, as the final product and the starting
material appeared to have almost same Rf values. First of all
column was washed with dichloromethane and petroleum
ether (2:1) to get rid of the starting material, second, with
petroleum ether and ethyl acetate (4:1) to get the final
product. A sticky solid was obtained, which was dried in
vacuum desiccator over P2O5 overnight to provide ADLC3 as a
0
73-185 C with higher ∆H value. ADLC3 with three side tails
exhibited liquid crystalline phase from room temperature
upon heating. Hexagonal columnar mesophase symmetry was
observed for ADLC3. ADLC4 was expected to be liquid crystal,
but did not show any mesomorphic phase.
In conclusion, from a rigid Td-symmetry central unit,
building two-dimensional disc molecules could generate
diverse columnar mesophases, while growth of one-
dimensional or three-dimensional molecular structures might
decrease the probability of inducing liquid crystallinity. We
hope these findings can provide a novel strategy for design
and functionalization of adamantane-based liquid crystals.
1
dark brown solid (0.509 g, yield: 63.39 %). H-NMR (300 MHz,
CDCl3):
ꢀ (ppm) = 0.88 (27H, t, J = 6 Hz, CH3), 1.26 (144H, m,
C8H16), 1.44 (18H, m, CH2), 1.77 (18H, m, CH2), 1.98 (6H, s, Acknowledgements
adamantane H), 2.19 (6H, m, adamantane H), 2.49 (1H, m,
This research was supported by National Natural Science
adamantane H), 3.89 (6H, t, J = 9 Hz, OCH2), 3.95 (12H, t, J = 6
Hz, OCH2), 6.82 (6H, s, ArH), 7.32 (3H, s, NH). 13C-NMR (75
Foundation of China (Grant No. 21374016) and Priority
Academic Program Development of Jiangsu Higher Education
Institutions. We thank Prof. Shilun Qiu (Jilin University) for
providing us 1,3,5,7-adamantane tetracarboxylic acid.
MHz, CDCl3): ꢀ (ppm) = (14.07, 22.67, 26.07, 26.13, 28.66,
29.35, 29.36, 29.40, 29.63, 29.69, 29.73, 30.29, 31.91, 38.01,
39.59, 42.77, 69.13, 73.51, 76.57, 76.99, 77.42, 98.97, 132.93,
134.92, 153.23, 173.76). IR (KBr, cm-1):
1649.
⊽ = 3321, 2922, 2851,
References
1 S. Chandrasekhar, B. K. Sadashiva and K. A. Suresh, Pramana,
1977, 9, 471.
Synthesis of ADLC4
2 B. R. Kaafarani, Chem. Mater., 2011, 23, 378.
3 T. D. Choudhury, N. V. S. Rao, R. Tenent, J. Blackburn, B.
Gregg and I. I. Smalyukh, J. Phys. Chem. B, 2011, 115, 609.
4 L. Schmidt-Mende, A. Fechtenkotter, K. Mullen, E. Moons, R.
H. Friend and J. D. MacKenzie, Science, 2001, 293, 1119.
5 X. Feng, V. Marcon, W. Pisula, M. R. Hansen, J. Kirkpatrick, F.
Grozema, D. Andrienko, K. Kremer and K. Mullen, Nature
Mater., 2009, 8, 421.
It was synthesised as per the procedure for ADLC3 and was
purified by silica gel column using petroleum ether and ethyl
acetate (5:1) as eluting solvents to provide ADLC4 as an off-
white solid (0.143 g, yield: 31.64 %). 1H-NMR (300 MHz, CDCl3):
ꢀ
(ppm) = 0.88 (36H, t, J = 6Hz, CH3), 1.26 (192H, m, C8H16),
1.45 (24H, m, CH2), 1.75 (24H, m, CH2), 2.31 (12H, s,
adamantane H), 3.95 (8H, t, J = 3 Hz, OCH2), 4.00 (16H, t, J = 6
Hz, OCH2), 6.78 (8H, s, ArH), 6.94 (4H, s, NH). 13C-NMR (75
6 B. A. Gregg, M. A. Fox and A. J. Bard, J. Phys. Chem., 1990,
94, 1586.
MHz, CDCl3): ꢀ (ppm) = (14.08, 22.69, , 26.10, 26.16, 29.36,
29.39, 29.48, 29.65, 29.69, 29.75, 30.32, 31.93, 37.90, 46.00,
7 O. Bunk, M. M. Nielsen, T. I. Solling, A. M. van de Craats and
N. Stutzmann, J. Am. Chem. Soc., 2003, 125, 2252.
8 A. M. Van de Craats, N. Stutzmann, O. Bunk, M. M. Nielsen,
M. Watson, K. Mullen, H. D. Chancy, H. Sirringhaus and R.
H. Friend, Adv. Mater., 2003, 15, 495.
48.87, 69.24, 72.52, 76.75, 77.00, 77.26, 98.98, 133.55, 134.98,
153.24, 171.14). IR (KBr, cm-1):
⊽ = 3327, 2921, 2854, 1649.
9 I. McCulloch, M. Heeney, C. Bailey, K. Genevicius, I.
MacDonald, M. Shkunov, D. Sparrowe, S. Tierney, R.
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Soft Matter
Page 9 of 10
Journal Name
Wagner, W. Zhang, M. L. Chabinyc, R. J. Kline, M. D.
View Article Online
DOI: 10.1039/C6SM01019A
ARTICLE
43 M. Saunders, and H. A. Jimenez-Vazquez, Chem. Rev., 1991,
91, 375.
44 N. Pannier and W. Maison, Eur. J. Org. Chem., 2008, 1278.
45 M. Tominaga, K. Katagiri and I. Azumaya, CrystEngComm,
2010, 12, 1164.
46 Е. А. Ivleva, V. S. Gavrilova, D. I. Gnusarev, V. А. Osyanin and
Y. N. Klimochkin, Russ. J. Org. Chem., 2015, 51, 180.
47 Q. Fang, S. Gu, J. Zheng, Z. Zhuang, S. Qiu and Y. Yan, Angew.
Chem. Int. Ed., 2014, 53, 2878.
48 F. Lincker, P. Bourgun, P. Masson, P. Didier, L. Guidoni, J. Y.
Bigot, J. Nicoud, B. Donnio and D. Guillon, Org. Lett., 2005,
7, 1505.
49R. I. Gearba, M. Lehmann, J. Levin, D.A. Ivanov, M.H.J.
Koch, J. Barbera, M.G. Debije, J. Piris and Y.H. Geerts,
Adv. Mater., 2003, 15, 1614.
50D. J. Broer, C. M. W. Bastiaansen, M. G. Debije and A. P.
H. J. Schenning, Angew. Chem. Int. Ed., 2012, 51, 7102.
51T. Kato, T. Yasuda, Y. Kamikawa and M. Yoshio, Chem.
Commun., 2009, 7, 729.
52F. Vera, J. L. Serrano and T. Sierra, Chem. Soc. Rev., 2009,
38, 781.
McGehee and M. F. Toney, Nature Mater., 2006, 5, 328.
10 H. Engelkamp and R. J. M. Nolte, J. Porphyrins
Phthalocyanines, 2000, 4, 454.
11 A. S. Matharu, S. Jeeva and P. S. Ramanujam, Chem. Soc.
Rev., 2007, 36, 1868.
12 K. Venkatesan, P. H. Kouwer, S. Yagi, P. Muller and T. M.
Swager, J. Mater. Chem., 2008, 18, 400.
13 X. Crispin, J. Cornil, R. Friedlein and K. K. Okudaira, J. Am.
Chem. Soc., 2004, 126, 11889.
14 S. Kumar, Chem. Soc. Rev., 2006, 35, 83.
15 S. K. Pal, S. Setia, B.S. Avinash and S. Kumar, Liq. Cryst., 2013,
40, 1769.
16 S. Kumar, Liq. Cryst., 2005, 32, 1089.
17 Y. D. Zhang, K. G. Jespersen, M. Kempe, J. A. Kornfield, S.
Barlow, B. Kippelen and S. R. Marder, Langmuir, 2003, 19,
6534.
18 H. Meier, M. Lehmann, H. C. Holst and D. Schwoppe,
Tetrahedron, 2004, 60, 6881.
19 A. J. Attias, C. Cavalli, B. Donnio, D. Guillon, P. Hapiot and J.
Malthete, Mol. Cryst. Liq. Cryst., 2004, 415, 169.
20 M. Ichihara, H. Suzuki, B. Mohr and K. Ohta, Liq. Cryst., 2007,
34, 401.
53J. J. van Gorp, J. A. J. M. Vekemans and E. W. Meijer, J.
Am. Chem. Soc., 2002, 124, 14759.
21 V. V. S. Yanova, M. M. Krayushkin and A. G. Yurchenko, Russ.
Chem. Rev., 1970, 39, 817.
54 T. N. Ahipa, V. Kumar and A. V. Adhikari, Struct Chem, 2014,
25, 1165.
22 R. C. Fort and P. R. Schleyer, Chem. Rev., 1964, 64, 277.
23 R. Grigg, E. E. Elboray, M. F. Aly and H. H. Abbas-Temirekb,
Chem. Commun., 2012, 48, 11504.
24 S. Zarwell, S. Dietrich, C. Schulz, P. Dietrich, F. Michalik and
K. Ruck-Braun, Eur. J. Org. Chem., 2009, 13, 2088.
25 F. M. Menger and V. A. Migulin, J. Org. Chem., 1999, 64,
8916.
55 T. Yasuda, T. Shimizu, F. Liu, G. Ungar and T. Kato, J. Am.
Chem. Soc., 2011, 133, 13437.
56 C. V. Yelamaggad, A. S. Achalkumar, D. S. Rao and S. K.
Prasad, J. Org. Chem., 2009, 74, 3168.
57 R. K. Gupta, B. Pradhan, S. K. Pathak, M. Gupta, S. K. Pal and
A. A. Sudhakar, Langmuir, 2015, 31, 8092.
58Е. А. Ivleva, V. S. Gavrilova, D. I. Gnusarev, V. А. Osyanin
and Y. N Klimochkin, Russ. J. O. Chem., 2015, 51, 180.
26 D. N. Chin, D. M. Gordon and G. M. Whitesides, J. Am. Chem.
Soc., 1994, 116, 12033.
27 T. Kitagawa, H. Matsubara, K. Komatsu, K. Hirai, T. Okazaki
and T. Hase, Langmuir, 2013, 29, 4275.
28 S. Thyagarajan, A. Liu, O. A. Famoyin, M. Lambertoy and E.
Galoppini, Tetrahedron, 2007, 63, 7550.
29 F. Khalil, E. Franzmann, J. Ramcke, O. Dakischew, K. S. Lips,
A. Reinhardt and P. Heisig, Colloids Surf. B, 2014, 117, 185.
30 E. Franzmann, F. Khalil, C. Weidmann, M. Schrçder, M.
Rohnke, J. Janek, B. M. Smarsly and W. A. Maison, Chem.
Eur. J., 2011, 17, 8596.
31 G. A. Senchyk, A. B. Lysenko, I. Boldog, E. B. Rusanov, A. N.
Chernega, H. Krautscheidc and K. V. Domasevitch, Dalton
Trans., 2012, 41, 8675.
32 C. F. Huang, H. F. Lee, S. W. Kuo, H. Xu and F. C. Chang,
Polymer, 2004, 45, 2261.
33 M. Grillaud and A. Bianco, J. Pept. Sci., 2015, 21, 330.
34 A. Jakli, I. C. Pintre, J. L. Serrano, M. B. Ros and M. R. Fuente,
Adv. Mater., 2009, 21, 3784.
35 T. Gushiken, S. Ujiie, T. Ubukata and Y. Yokoyama, Bull.
Chem. Soc. Jpn., 2011, 84, 269.
36 M. Prehm, C. Enders, M. Y. Anzahaee, B. Glettner, U.
Baumeister and C. Tschierske, Chem. Eur. J., 2008, 14,
6352.
37 N. Gimeno, M. B. Ros, J. L. Serrano and M. R. D. Fuente,
Chem. Mater., 2008, 20, 1262.
38 D. Pociecha, K. Ohta, A. Januszko, P. Kaszynski and Y. Endo, J.
Mater. Chem., 2008, 18, 2978.
39 S. J. Cowling, A. W. Hall and J. W. Goodby, Liq. Cryst., 2005,
32, 1483.
40 A. Schwenger, W. Frey and C. Richert, Chem. Eur. J., 2015,
21, 8781.
41 W. Maison, J. V. Frangioni and N. Pannier, Org. Lett., 2004, 6,
4567.
42 C. Fleck, E. Franzmann, D. Claes, A. Rickert and W. Maison,
Synthesis, 2013, 45, 1452.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Soft Matter
Page 10 of 10
View Article Online
DOI: 10.1039/C6SM01019A
Table of Contents Graphic
Generation of Liquid Crystallinity from a Td-Symmetry Central Unit
Sayed Mir Sayed, Bao-Ping Lin, and Hong Yang*
Liquid crystals containing an adamantane central unit with its four bridgehead
positions partially or fully decorated with different numbers (1 - 4) of
3,4,5-tris(dodecyloxy)phenyl carbamoyl groups, present diverse columnar phases
(rectangular, square, hexagonal).