Highly disordered crystalline-phase transition of tetrakis(1- adamantanecarboxymethyl)methane

Article abstract of DOI:10.1246/bcsj.20110345

Tetrakis(1-adamantanecarboxymethyl)methane was prepared by indirect esterification. DSC traces of tetrakis(1-adamantanecarboxymethyl) methane showed two endothermic peaks. Entropy ratio of these two peaks is: ΔS _trs/ΔS_fus = 1.58 > 1. XRD confirmed the solidsolid transition and analysis of XRD by DICVOL demonstrated tetrakis(1-adamantanecarboxymethyl) methane is a new compound with a highly disordered crystalline phase. Analysis of entropy changes at transitions showed why fusion entropy (ΔS_fus = 70.07 Jmol^-1K ^-1) of tetrakis(1-adamantanecarboxymethyl)- methane is much larger than Timmermans' criterion.

Full text of DOI:10.1246/bcsj.20110345

© 2012 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 85, No. 4, 481-486 (2012)
481
Highly Disordered Crystalline-Phase Transition
of Tetrakis(1-adamantanecarboxymethyl)methane
Rong Li,1 Chunyue Pan,*1 Shaohui Xiong,1 Guipeng Yu,1
Pingshan Wang,1 Yingping Zou,1 and Aiqing Zhang2
1College of Chemistry and Chemical Engineering, Central South University, Changsha 4100831, P. R. China
2School of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan 430074, P. R. China
Received November 9, 2011; E-mail: chunyuepan@yahoo.cn
Tetrakis(1-adamantanecarboxymethyl)methane was prepared by indirect esterification. DSC traces of tetrakis(1-ada-
mantanecarboxymethyl)methane showed two endothermic peaks. Entropy ratio of these two peaks is: ¦Strs/¦Sfus
=
1.58 > 1. XRD confirmed the solid-solid transition and analysis of XRD by DICVOL demonstrated tetrakis(1-ada-
mantanecarboxymethyl)methane is a new compound with a highly disordered crystalline phase. Analysis of entropy
changes at transitions showed why fusion entropy (¦Sfus = 70.07 J mol¹1 K¹1) of tetrakis(1-adamantanecarboxymethyl)-
methane is much larger than Timmermans’ criterion.
Adamantane and pentaerythritol are both typical symmetric
globular compounds which undergo crystal to plastic crys-
tal transitions. A novel ester, tetrakis(1-adamantanecarboxy-
methyl)methane, supposed to undergo a transition to plastic
crystalline phase or highly disordered crystalline phase was
prepared by using esterification between two different plas-
tic crystalline compounds pentaerythritol and 1-adamantane-
carboxylic acid. Its structure was characterized by FT-IR,
NMR, and elemental analysis. Differential scanning calorim-
etry (DSC) and X-ray power diffraction (XRD) studies of
tetrakis(1-adamantanecarboxymethyl)methane showed that it
exhibited a solid-solid transition before melting. DSC thermo-
grams displayed two endothermic peaks at 178.6 and 278.8 °C,
and their entropies were 110.55 and 70.07 J mol¹1 K¹1, respec-
tive on solid-state ionics that the ion conductivity of solid-state
ion conductors is often associated with dynamics orientational
disorder or rotator motions in the crystalline lattice,10 Wang
et al. disclosed a highly conductive solid iodide/triiodide con-
ductor for a highly efficient, all-solid-state dye-sensitized solar
cell.11 Adebahr et al. studied the “filler-effect” of nanosized
ceramic TiO2 on the phase behavior and conductivity of organic
ionic plastic crystal ethylmethylpyrrolidinium bis(trifluoro-
methanesulfonyl)amide P12TFSA.12 Shekibi et al. added lithi-
um-functionalized silica nanoparticles to enhance ionic con-
ductivity of an organic ionic plastic crystal.13 All these studies
showed that due to plastic crystals’ outstanding properties,
they became a new promising class of materials which is
essential for solid-state electrolytes of fuel cells, batteries, solar
cells, and so on.14,15
tively. Entropy ratio of these two peaks is: ¦Strs/¦Sfus
=
1.58 > 1. XRD patterns at higher temperatures (180 °C < T <
275 °C) are much simpler than those at lower temperatures
(T < 175 °C). In low-temperature phase (155 °C), tetrakis(1-
adamantanecarboxymethyl)methane adopts a triclinic structure,
whereas it transforms into a more symmetric tetragonal unit cell
in its highly disordered crystalline phase. Hyperchem8.0.3 was
used to simulate the structure of tetrakis(1-adamantanecarboxy-
methyl)methane, and entropy changes of transitions were also
discussed.
Along with the development of plastic crystal, researchers
summed up the laws of plastic crystal forming. In the early
years, Timmermans16 concluded that for many plastic crys-
tals the entropy of fusion, ¦Sm, is remarkably small (<21
J mol¹1 K¹1) and their high-temperature phases are often of
high crystallographic symmetry (usually cubic). He further
noted that the molecules of such substances are often globular
or roughly spherical. Afterwards, Staveley reached the sum-
marization that the molecules in plastic crystalline phases
possess unusual freedom of movement. Consequently, the
positions of the atoms are less definite than its usual and the
X-ray diffraction patterns are less well defined.17 From the
studies of neopentane, tetrakis(fluoromethyl)methane, penta-
erythritol, and some of its derivatives, Murrill and Breed18
came to the conclusion that very subtle changes in molecu-
lar geometry and size can inhibit the mesocrystalline phase.
Even slight changes in substitution with loss of symmetry
can also inhibit the mesocrystalline phase. Unfortunately, until
now how the organic compounds19-21 translate into the plastic
crystalline states and their simultaneous changes of mechanical,
Since the discovery of plastic crystal by Timmermans1 nearly
eighty years ago, a lot of globular molecules, such as meth-
ane (CH4),2 carbon tetrafluoride (CF4),3 carbon tetrachloride
(CCl4),4 carbon tetrabromide (CBr4),5 neopentane C(CH3)4,6
7,8
and pentaerythritol C(CH2OH)4 have been found to be able
to form plastic crystals. The development of plastic crystals
was actually slow during past years. However, after Forsyth’s
research that doping lithium ions into a plastic crystalline matrix
¹1
resulted in conductivities as high as 2 © 10¹4 S cm at 60 °C
in 1999,9 a considerable amount of work has been devoted to
plastic crystals. MacFarlane and Forsyth raised a new perspec-
Published on the web April 10, 2012; doi:10.1246/bcsj.20110345

482
Bull. Chem. Soc. Jpn. Vol. 85, No. 4 (2012)
Crystalline Phase Transition of Adamantane Derivative
optical, dielectric properties and conformational composi-
tions are still difficult to predict. In-depth investigations and
studies should be conducted on some major issues related
to plastic crystal, such as what are the criterions of plastic
crystalline transitions, what kinds of compounds can be plastic
crystals, how to design plastic crystalline compounds and
whether there are any functional properties and application in
plastic crystals.
(a)
(b)
Most of the molecules investigated were small molecules
with comparatively small sizes. To better understand the
relationship between the molecular structure and the ability
to form plastic crystal or highly disordered crystalline state,
we have prepared a series of molecules with different sizes,
composed of the “plastic units” adamantane and some other
highly symmetric compounds. Adamantane is a typical glob-
ular or roughly spherical plastic crystalline compound whose
derivatives are widely used in many fields such as pharma-
ceutical science,22 photosensors,23 and photoresists.24 Research
on adamantane and some of its derivatives, such as adaman-
tanamine hydrochloride,25 1-adamantanol,26 and adamantane-
carboxylic acid27 demonstrated that the adamantane cage is
quite rigid and its geometry is not affected by substitution
and crystal packing forces. In this paper, we have prepared
a compound, tetrakis(1-adamantanecarboxymethyl)methane, of
a comparatively larger size by using esterification between
pentaerythritol and 1-adamantanecarboxylic acid. For the
highly symmetric nature of pentaerythritol and the good
rigidness of adamantane, the compound prepared was expected
to be a globular-like molecule with a transition to plastic
crystalline state or highly disordered crystalline state. DSC was
applied to characterize thermal transitions of tetrakis(1-ada-
mantanecarboxymethyl)methane. XRD was used to further
investigate the solid-solid phase transition, and XRD diffrac-
tions were resolved by the computer program DICVOL.28
Structural simulation was applied to confirm the conclusion
drawn from DSC and XRD. Entropy changes of its transitions
were also discussed.
150
200
250
300
T/°C
Figure 1. DSC thermograms of tetrakis(1-adamantane-
carboxymethyl)methane measured at a rate of (a) 1 and
(b) 10 °C min
¹1
.
197
185
179
175
T/°C
155
5
15
20
25
10
2θ/°
Figure 2. Changes in the powder diffraction pattern
of tetrakis(1-adamantanecarboxymethyl)methane between
145 and 197 °C.
Results and Discussion
Thermal Analysis. The DSC traces of tetrakis(1-adaman-
tanecarboxymethyl)methane between 140 and 310 °C are shown
in Figure 1 (No peak between 50 and 170 °C was found). The
material displays three different phases with transitions from
phase II ¼ I at 177.6 °C (conventionally, the highest temper-
ature solid phase is denoted phase I, with subsequent lower
temperature phases denoted phase II, III), and transitions from
phase I ¼ liquid at 278.8 °C. The endothermic transition at
177.6 and 278.8 °C correspond to the solid-solid transition
and melting of the crystalline tetrakis(1-adamantanecarboxy-
methyl)methane, respectively. Their corresponding values
¦Sfus ¯ 21 J mol¹1 K¹1, and there are some examples of plas-
tic crystals not coincident with Timmermans’ criterion, a
preliminary conclusion that tetrakis(1-adamantanecarboxy-
methyl)methane transforms to a highly disordered crystalline
phase at 177.6 °C can be drawn. XRD was used to further inves-
tigate the phase transition of tetrakis(1-adamantanecarboxy-
methyl)methane later in the article.
XRD. X-ray diffraction analysis of tetrakis(1-adamantane-
carboxymethyl)methane (Figure 2) clearly indicates that the
compound experiences structural changes with increasing
temperature. The changes appear to take place at the temper-
ature of 175 to 179 °C. XRD patterns of powdered samples
at 155 and 193 °C were selected as representatives of the low-
and the high-temperature phases, respectively, and they were
further used for indexing and solving the structures. From
low-temperature phase to high-temperature phase, there is a
diminution of the number of peaks. This reveals an evolution
to a phase of higher symmetry.
¹1
¹1
are ¦Strs = 110.55 J mol¹1 K and ¦Sfus = 70.07 J mol¹1 K
,
with ¦Strs/¦Sfus = 1.58 > 1. Plastic crystal formation is gen-
erally accompanied by a low fusion entropy (¦Sfus) and the ratio
¦Strs/¦Sfus ² 1.29 Transition entropy (¦Strs) of phase II ¼ I
larger than the fusion entropy (¦Sfus) suggested that phase I
of tetrakis(1-adamantanecarboxymethyl)methane is a highly
disordered crystalline phase.30 Since entropy change of tetra-
kis(1-adamantanecarboxymethyl)methane at fusion (¦Sfus
=
70.07 J mol¹1 K¹1) is larger than Timmermans’ criterion of

R. Li et al.
To determine the lattice parameters at 155 °C, 16 Bragg
peaks in the angular range 5-25° were fit with the program
DICVOL.28 When the calculated figures of merit (de Wolff,31
1968; Smith and Snyder,32 1979) were at the maximum:
M(16) = 37.2, F(16) = 31.7 (0.0013, 30), tetrakis(1-adaman-
tanecarboxymethyl)methane adopts a triclinic crystal system,
with the unit cell parameters: a = 16.4670(19) ¡, b =
Bull. Chem. Soc. Jpn. Vol. 85, No. 4 (2012)
483
FULLPROF35 and it converged at Rp = 13.2%, Rwp = 6.8%.
Linear interpolation between selected points was applied to
describe the background.
7 peaks were indexed at 193 °C by DICVOL28 in a primi-
tive tetragonal cell with the unit cell parameters: a =
16.0362(13) ¡, c = 4.9433(7) ¡, V = 1271.22(17) ¡3. System-
atic absences indicated the space group P4/mmm. The group-
subgroup relationship between tetragonal and triclinic as
well as the volumes of the two unit cells suggested that the
high-temperature phase contain only one molecule per unit cell,
so the density of tetrakis(1-adamantanecarboxymethyl)methane
at 193 °C is Dcalcd = 1.03 g cm¹3. Thus the X-ray density of
tetrakis(1-adamantanecarboxymethyl)methane decrease abrupt-
ly (approximately by 14%) at the solid-solid phase transition.
This confirms that phase I of tetrakis(1-adamantanecarboxy-
methyl)methane is a highly disordered crystalline phase.
Finally, Rietveld refinement (Figure 4b) was performed for
the high-temperature phase and it converged at Rp = 11.5%,
9.0489(6) ¡,
120.454(5)°, £ = 106.711(7)°, V = 1089.85(5) ¡3, Z = 1.
calcd = 1.19 g cm¹3. The space group was indicated to be
c = 9.2246(8) ¡,
¡ = 94.845(5)°,
¢ =
D
P1. Structure resolving in this space group by global opti-
mization in direct space using the program FOX33 failed, due to
the difficulty in converting the hyperchem export format into
FOX33 input format, so structure of the tetraester was only
obtained in hyperchem8.0.3, using molecular dynamics simu-
lation. Results are shown in ball and stick and CPK display
style (hydrogens were omitted). The structure (Figure 3) gotten
from calculation shows that the expected globular molecule
is not a spherically symmetric structure in three-dimensional
space. Tetrakis(1-adamantanecarboxymethyl)methane is neither
a centrosymmetric molecule, nor a tetrahedral-like molecule
in low-temperature phase (the twist of ester bonds causes the
adamantane group to be not well-distributed in three-dimen-
sional space, that is to say, the central C-C-C bond angle
is not 109°28¤). This is coincident with the conclusion of
the DICVOL28 solving. Finally, the refinement (Figure 4a)
was done by the Rietveld method34 using the program
R
wp = 5.3%.
There are a few reports in the literature that detail the
temperature dependence of XRD patterns for organic molecule
plastic crystals. Meersman et al.29 have reported that the hydro-
gen bonded N-isopropylpropionamide exhibits a diffraction
pattern that is consistent with the space group P2/a monoclinic
structure in low-temperature phase (4 °C), which simplifies
to a pattern of tetragonal structure in high-temperature phase
(13 °C). Descamps et al.36-38 have reported the powder XRD
spectra of anhydrous caffeine which adopts a monoclinic C-
centered unit cell in low-temperature phase (290 K), transforms
to tetragonal unit cell in high-temperature phase (425 K). Both
of these materials exhibit simpler diffraction patterns in their
higher temperature phases than those in their lower temperature
phases, respectively. In our research, the X-ray powder diffrac-
tion patterns of tetrakis(1-adamantanecarboxymethyl)methane
indicate that this compound exhibits tetragonal and triclinic
crystal structures in phase I and II, respectively, which is quite
consistent with the DSC analysis, as discussed above.
To obtain full tetragonal symmetry, a random distribution of
tetrakis(1-adamantanecarboxymethyl)methane among equiva-
Figure 3. Structure
methyl)methane showed in different styles.
of
tetrakis(1-adamantanecarboxy-
b
a
2θ /
°
2θ / °
Figure 4. Rietveld plot of the low-temperature phase of tetrakis(1-adamantanecarboxymethyl)methane at 155 °C (left) and the high-
temperature phase of tetrakis(1-adamantanecarboxymethyl)methane at 193 °C (right). Observed intensities are indicated by red dots,
the best-fit profile (upper black trace) and the difference pattern (lower blue trace) are solid.

484
Bull. Chem. Soc. Jpn. Vol. 85, No. 4 (2012)
Crystalline Phase Transition of Adamantane Derivative
For the fusion transition, the translational motions also take
place. So the sums of the entropy of fusion are:
7.16
7.14
7.12
7.10
7.08
7.06
7.04
7.02
7.00
6.98
α = 4.9 x10-3
X
X
X
ꢀfusSm0
¼
ꢀvSm0 þ
ꢀ
ꢀ
int:rot:Sm0
X
X
þ
orient:Sm0 þ
ꢀ
tra:Sm0
ð2Þ
P
where
ꢀ
tra:Sm0 denotes the contribution of translational
motion. Formula (1) applies to solid to plastic crystal transition
T = 177.8°C
of neopentane.
α = 3.5 x10-3
P
Why is
ꢀfusSm0 of tetrakis(1-adamantanecarboxymethyl)-
methane significantly larger than Timmermans’ criterion of
plastic crystal, and is it a plastic crystal or only a highly
disordered crystalline phase? The former question might
be explained based on the two formulas above. From the
comparison of the structures between neopentane and tetra-
kis(1-adamantanecarboxymethyl)methane we know that: 1)
The four arms of tetrakis(1-adamantanecarboxymethyl)methane
are much longer than the arms of neopentane, so there is more
space for the moving of the arms. 2) Good flexibility of the ester
bond makes the arms rotate more easily. 3) Timmermans’
criterion of plastic crystal is about the molar entropy change
of the fusion, and the additive property of entropy makes
the entropy change of tetrakis(1-adamantanecarboxymethyl)-
methane larger for the randomness probability of tetrakis(1-
adamantanecarboxymethyl)methane itself is larger than neopen-
tane. Since there is already isotropic reorientation of tetrakis(1-
adamantanecarboxymethyl)methane in phase I, its fusion en-
tropy (¦Sfus = 70.07 J mol¹1 K¹1) is smaller than structurally
similar compounds forming “rigid” crystal, even smaller
than the transition entropy of phase II ¼ I (¦Strs = 110.55
J mol¹1 K¹1). Combine this with the following two facts:
a) The fusion entropy (¦Sfus = 70.07 J mol¹1 K¹1) of tetra-
kis(1-adamantanecarboxymethyl)methane is much larger than
Timmermans’ criterion; b) The crystal system of tetrakis(1-
adamantanecarboxymethyl)methane in phase I is not highly
symmetric. This suggests that phase I of tetrakis(1-adamantane-
carboxymethyl)methane is not a plastic crystalline phase but a
highly disordered crystalline phase.
150 155 160 165 170 175 180 185 190 195
T/°C
Figure 5. Temperature evolution of cell volume in low-
and high-temperature phases. The cross-point temperature
is the solid-solid transition temperature.
lent positions can be assumed. With increasing temperature, the
whole tetrakis(1-adamantanecarboxymethyl)methane molecule
extended and distributed more uniformly in the three-dimen-
sional space. So we can image a picture that there is one
tetrakis(1-adamantanecarboxymethyl)methane molecule in each
tetragonal lattice, and tetrakis(1-adamantanecarboxymethyl)-
methane molecules can constantly spin on their own or oscillate
in their own lattice, that is to say, entropy change of 110.55
J mol¹1 K¹1 corresponds to isotropic reorientation of tetrakis(1-
adamantanecarboxymethyl)methane molecules. Thus, the struc-
ture must be highly disordered in the short range in phase I.
Volumes in low- and high-temperature phases at different
temperatures obtained from XRD are shown in Figure 5, and
they were fitted by a linear fit method. It is clear from this
figure that a break in the temperature evolution of the cell
volume occurs and the cross-point temperature of these two
straight-line segments is 177.8 °C, which is close to the
solid-solid transition temperature shown in DSC. The change
of slope results in an increment of the thermal expansion
coefficient by about 40%, which suggests that structure change
exists.
Conclusion
Entropy Changes of Transformations. Entropy, from a
statistical point of view, is a measurement of molecule disorder
or molecule randomness. Even in the solid state, the molecules
of a substance continually oscillate, creating an uncertainty in
position.39 The ways to increase the entropy include: 1) Adding
particles; 2) adding energy; 3) increasing the volume; 4)
decomposing molecules; 5) letting a linear polymer curl up.40
As for tetrakis(1-adamantanecarboxymethyl)methane, if
variations in vibration frequencies in crystal lattice and mole-
cules, changes of the concentration of positional defects and so
on, are ignored, the thermodynamic parameters corresponding
to the solid-solid transition can be represented as the following
sums:41
Tetrakis(1-adamantanecarboxymethyl)methane, which is
composed of pentaerythritol core and adamantane arms, was
prepared through esterification and its chemical structure
was confirmed by FT-IR, 1H NMR, and elemental analysis.
DSC and XRD were used to demonstrate tetrakis(1-adaman-
tanecarboxymethyl)methane is a novel compound with a
highly disordered crystalline phase. DSC characterization
displayed that tetrakis(1-adamantanecarboxymethyl)methane
goes through two phase transitions at 177.6 and 278.8 °C,
respectively, and entropy ratio of these two peaks: ¦Strs/
¦Sfus = 1.58 > 1. Further research by XRD confirmed that
there is a solid-solid transition before melting, and solving of
the XRD powder diffractions showed that in high-temperature
phase, tetrakis(1-adamantanecarboxymethyl)methane adopts te-
tragonal unit cell. The P4/mmm space group and the structure
of tetrakis(1-adamantanecarboxymethyl)methane suggests that
the high-temperature phase is a highly disordered crystalline
phase. The XRD also indicates an abrupt decrease of density
(approximately by 14%) at the solid-solid phase transition.
X
X
X
X
ꢀtrsSm0
¼
ꢀvSm0 þ
ꢀ
int:rot:Sm0 þ
ꢀ
orient:Sm0 ð1Þ
P
where
ꢀvSm0 denotes the contribution of volume changes
P
P
to the values of
internal rotation of the tops,
orientational motion.
ꢀtrsSm0 ,
ꢀ
int:rot:Sm0 the contribution of
P
ꢀ
orient:Sm0 the contribution of

R. Li et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 4 (2012)
485
O
O
Cl
Cl
CHCl3
reflux
+
S
O
Cl
O H
O
C
HO
C
O
O
OH
O
C
150 °C
DMF
+
C
C
HO
Cl
O
O
OH
O
C
C
O
Scheme 1. Synthetic routes of tetrakis(1-adamantanecarboxymethyl)methane.
Additionally, the present paper demonstrated that, for the
Synthesis (Scheme 1). 1-Adamantanecarbonyl Chloride
(1): 1-Adamantanecarboxylic acid (7.20 g, 40 mmol), 8 mL
of chloroform and a catalytic amount of pyridine were put into
a 100 mL flask. The mixture was cooled by ice-water bath, and
then thionyl dichloride (7.14 g, 60 mmol) was added in one
portion under nitrogen atmosphere. The reactant was stirred
overnight at reflux temperature, and a clear solution was
obtained. After removing the solvent and unreacted thionyl
dichloride, 7.36 g (92.6% yield) of 1-adamantanecarbonyl
chloride (1) was collected as colorless solid, mp 48.5-52.3 °C.
Tetrakis(1-adamantanecarboxymethyl)methane (2): To
the solution of 1 (7.36 g) in DMF at room temperature were
added a mixture of pentaerythritol (1.36 g, 10 mmol) and
pyridine (1 mL). The reaction mixture was warmed to 150 °C
and well stirred for 3 h. After cooling the reaction mixture to ca.
40 °C, it was poured into 15 mL saturated sodium hydrogen
carbonate, and extracted by 50 mL of xylene two times. The
organic layer was separated, and washed repeatedly with
saturated sodium hydrogen carbonate until the aqueous wash-
ings became distinctly alkaline, and finally with water until
neutral. The xylene solution was dried over anhydrous MgSO4,
then the solvent was removed by rotary evaporation. The crude
product was chromatographed on a silica column using CHCl3
as the eluent to give 2 as an oily light yellow solid. Finally
the oily solid was recrystallized from propanone to give 6.56 g
of colorless needle-shaped solid (83.6% yield), mp 277.6-
279.1 °C.
“core-arms” molecule, the length, the softness of arms and the
space among arms all affect its entropy; for the macromole-
cules, especially polymers, their fusion entropy might be larger
than Timmermans’ criterion due to the rotational freedom of
some structural units, but they can also highly disordered
before melting.
Experimental
Materials.
1-Adamantanecarboxylic acid was obtained
from Sigma-Aldrich. C(CH2OH)4 was obtained from Alfa
Aesar. Thionyl dichloride was obtained from Aladdin. All other
reagents and solvents were purchased commercially as ana-
lytical-grade quality and used without further purification.
Measurements. 1H NMR, FT-IR, and Elemental Analy-
sis: 1H NMR spectra were recorded using a Bruker DMX-300
spectrometer. Fourier transform infrared (FT-IR) spectra were
recorded on a BIO FTS-135 spectrometer by dispersing samples
in KBr pellets. The elemental analysis was performed on a
Vario EL elemental analysis instrument (ELEMENTAR Co.).
Differential Scanning Calorimetry: DSC measurement
was conducted on a METTLER TOLEDO STAR system-
DSC822. Baseline, heat capacity, and temperature were cali-
brated with sapphire and indium. TA Instruments hermetic
aluminum crucibles of 40 ¯L were used. The heating rates
¹1
applied were 1 and 10 °C min under a nitrogen atmosphere,
and the sample mass were recorded to be 3.18 and 3.68 mg,
respectively. The temperature range was 50 to 300 °C. The
onset of the melting (crystallization) peak is taken as the
melting (crystallization) temperature.
1H NMR, FT-IR, and Elemental Analysis.
1H NMR
(CDCl3): ¤ 4.038 (s, 8H), 1.950 (s, 12H), 1.792-1.799 (m,
24H), 1.635-1.647 (m, 24H).
X-ray Diffraction: The in situ XRD measurements were
performed on a Bruker-AXS D8 ADVANCE ª/ª type dif-
fractometer equipped with a diffracted-beam graphite mono-
chromator using Cu K¡ radiation and a Bruker-AXS MRI wide
range high temperature chamber in which flowing nitrogen gas
was used. The temperature was varied from 125 to 200 °C, with
an increment of 10 °C min¹1. The two-dimensional diffraction
images were azimuthally integrated, yielding one-dimensional
intensity (I) versus 2ª (where 2ª is the diffraction angle
5° < 2ª < 25°).
FT-IR (KBr, cm¹1): 2904, 2852 (H-C stretch vibration),
1725 (C=O stretch vibration), 1470, 1344 (H-C in-plane
bending vibration), 1229, 1074 (-CO-O- stretch vibration).
Element Anal. Calcd for C49H68O8: C, 74.97; H, 8.73;
O, 16.30%. Found: C, 75.00; H, 8.71; O, 16.33%.
We are grateful to Dr. Yu and Dr. Zou for their guidance. We
thank Dr. Wei Li for his assistance with the XRD experiments
and Graduate Rong Zhou for her assistance with the DSC
experiments.

486
Bull. Chem. Soc. Jpn. Vol. 85, No. 4 (2012)
Crystalline Phase Transition of Adamantane Derivative
Ziliox, R. A. Volkmann, J. Am. Chem. Soc. 2000, 122, 466.
23 H. Y. Acar, J. J. Jensen, K. Thigpen, J. A. McGowen, L. J.
Mathias, Macromolecules 2000, 33, 3855.
This research was supported by grants from the National
Natural Science Foundation of China (No. 20976199).
24 S. Fleischmann, V. Percec, J. Polym. Sci., Part A: Polym.
Chem. 2010, 48, 2251.
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2
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