Orders Exhibited by Ensemble of Headless Spins Preferring Twisted Alignment: Phase Diagram of Extended Maier-Saupe Model on Simple Cubic Lattice

Kazuya SAITO, Mafumi HISHIDA and Yasuhisa YAMAMURA

Effect of the preference for non-parallel alignment without a preferred twist sense of neighboring headless spins is examined through computer simulations on extended Maier-Saupe models on the simple cubic lattice with/without next-nearest neighbor interactions. Phase diagrams containing four phases are constructed for a varying degree of the preference for the local twist and for a strength of the next-nearest-neighbor interaction. It is shown that the preference for the local twist brings about not only the instability for the nematic (uniaxial) order but also that for a spatial order to reduce the frustration arising from the local twist. The next-nearest-neighbor interaction can produce even a weak spatial order of local chirality. The results are discussed in relation to the formation of a liquid crystalline gyroid phase and chiral phases in ensembles consisting of anti-spindle molecules that are axially symmetric and achiral.
(J. Phys. Soc. Jpn., 86, 084602 (2017))


Mirror Symmetry Breaking by Mixing of EquimolarAamounts of Two Gyroid Phase-forming Achiral Molecules

Shoichi KUTSUMIZU, Suguru MIISAKO, Yohei MIWA, Makoto KITAGAWA, Yasuhisa YAMAMURA and Kazuya SAITO

Mirror symmetry breaking was observed by mixing of equimolar amounts of two gyroid phase-forming achiral molecules, one having a short and the other with a long tail. This fact indicates the importance of a critical chain length for the appearance of the chiral bicontinuous cubic (Cubbi) phase. It also demonstrates that the molecular-level mobility is closely connected to the formation and stabilisation of those Cubbi phases.
(Phys. Chem. Chem. Phys., 18, 17341-17344 (2016))


Stabilization of the Bicontinuous Cubic Phase in Siloxane-Terminated
Mesogens, 1,2-Bis[4'-(n-(oligodimethylsiloxyl)alkoxy)benzoyl]hydrazine

Shoichi KUTSUMIZU, Issei TOKIWA, Akane KAWAFUCHI, Yohei MIWA, Yasuhisa YAMAMURA and Kazuya SAITO

Introduction of oligodimethyl siloxane segments at the termini of the alkyl tails has been employed to stabilize bicontinuous cubic (Cubbi) phase of a chain-core-chain type molecule having 1,2-bis(benzoyl)hydrazine central core with two chains attached at the 4' position of each benzoyl moiety. In this study, three silylated molecules, bis-C10Si2, bis-C10Si3, and C10Si2-C8C=C were synthesized, where "CnSim" represents the number of carbon and silicon atoms in the chain and "bis" means the two chains being the same whereas the last one is asymmetric with respect to the core. The phase behaviors were examined by using polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction techniques. All three compounds forms Cubbi phases and their formations were compared including their parent compound bis-C18. It was clearly revealed that the introduction does effectively suppress crystallization at low temperatures and as a result, stabilizes the Cubbi phases, in an extreme case down to room temperature. The semi-quantitative analyses in terms of lattice constant and three-dimensional electron density map help us to better understand the selfassembly process in the Cubbi phases. The study also revealed the introduction of oligodimethyl siloxane segments is not only an alternative of hydrocarbon segment but is able to provide versatile design strategy for obtaining stable formation of the Cubbi phases.
(Phys. Chem. Chem. Phys., 18, 9013-9020 (2016))


A Structural Model of the Chiral Im3m Cubic Phase

Kazuya SAITO, Yasuhisa YAMAMURA, Yohei MIWA and Shoichi KUTSUMIZU

Assuming the twisted arrangement of rodlike molecules as the origin of the chirality as in the existing model, a new model of the molecular arrangement in the cubic "Im3m" phase is proposed. The adoption of a basic structure different from that assumed in the existing model resolves most difficulties of the model including the random placement of defects concerning the sense of twist.
(Phys. Chem. Chem. Phys., 18, 3280-3284 (2016))


Effects of the Lateral Substituent on the Cubic Phase Formation of Two Analogous Compounds, 4'-n-Hexadecyloxy-3'-cyanobiphenyl-4-carboxylic acid (ACBC-16) and Its 3'-Nitro Compound (ANBC-16)

Ryoji OGAWA, Yohei MIWA, Masato SUMITA, Kazuya SAITO and Shoichi KUTSUMIZU

Two cubic (Cub)-phase forming compounds, 4'-n-hexadecyloxy-3'-cyanobiphenyl-4- carboxylic acid (ACBC-16) and its 3'-nitro analogue (ANBC-16) were studied by infrared (IR) spectroscopy and quantum chemical calculation at DFT/B3LYP level. In contrast with the identical stabilization energies for dimerization and frequencies of aromatic ring C=C stretching (nu_(C=C)ring) band predicted for their respective model compounds, in the temperature region of the Cub phase, the molar fraction of hydrogen-bonded COOH groups estimated for ACBC-16 was different from, and by ca. 5 % at maximum larger than, that for ANBC-16, and the nu_(C=C)ring band frequency of ACBC-16 was by 3 cm-1 lower than that of ANBC-16. These results can be ascribed to the different steric effects of the side groups; the CN group would make possible the close contact of neighboring phenyl rings while the bulky NO2 group would not, giving slightly more stabilized dimerization of ACBC-16 in the Cub phase than in ANBC-16.
(Liq. Cryst., 42, 143-157 (2015))


Liquid-Crystallinity of Cubic Phase of BABH (6) through Thermal Analysis of Solid-Solid Phase Transitions

Mika UMEYAMA, Shuhei FUJIMURA, Mafumi HISHIDA, Yasuhisa YAMAMURA, Shoichi KUTSUMIZU and Kazuya SAITO

Phase transitional behavior of 1,2-bis(4'-n-hexyloxybenzoyl)hydrazine (BABH(6)) was studied by differential scanning calorimetry (DSC) and polarizing microscopy. While the DSC trace above melting temperature is consistent with the existing report, it is not for crystalline states. A number of tiny and spiky anomalies was observed in the first cooling run whereas the number of anomalies decreases, and finally disappeared in repeated runs. Microscopic observation revealed that the tiny and spiky anomalies arise from collapsing of crystals. When the sample was cooled from the cubic phase (430 K), the tiny and spiky anomalies revived on the cooling process, which can be ascribed to the liquid-crystallinity of the cubic phase.
(Thermochim. Acta, 590, 160 (2014))


Phase Behavior of a Thermotropic Cubic Mesogen of 1,2-Bis(4'-n-hexyloxybenzoyl)hydrazine under Pressure

Yoji MAEDA, Yasuhisa YAMAMURA, Shoichi KUTSUMIZU and Kazuya SAITO

Phase behavior of a thermotropic cubic mesogen, 1,2-bis(4'-n-hexyloxybenzoyl)hydrazine [BABH(6)] was investigated under pressure up to about 55 MPa using a polarizing optical microscope equipped with a high-pressure optical cell. BABH(6) shows the crystal (Cr) - cubic (Cub) - isotropic liquid (I) phase transition at ambient pressure on heating. The smectic C (SmC) phase was induced above 32 MPa, showing the unusual phase sequence of Cr - Cub - SmC - I similar to those in BABH(n) (n = 8 - 10). The boundary between Cub and SmC phases exhibited a negative slope dT/dP of about -1.0 K MPa-1.
(Liq. Cryst., 41, 731 (2014))


Molecular Mechanism Responsible for Reentrance to Ia3d Gyroid Phase in Cubic Mesogen BABH(n)

Yuri NAKAZAWA, Yasuhisa YAMAMURA, Shoichi KUTSUMIZU and Kazuya SAITO

Maximum entropy analyses of small-angle X-ray diffraction patterns of a series of title compounds [1,2-bis(4'-n-alkyloxybenzoyl)hydrazine, n: number of carbon atoms in an alkyl group] yield a new description of the so-called gyroid phase. The structure is described as two sets of connected triangles, instead of jungle gyms consisting of rods, embedded in two spaces separated by a mathematical gyroid. The reconstructed electron density provides new evidence of molecular packing: While molecules having short alkyl chains laterally aggregate to form single layers of triangular shape with nearly vertical alignments, those with long chains split into two groups on both sides of the triangular planes. The formation of double layers of the molecular cores is tolerable with the possible formation of hydrogen bonds between shifted molecules, and adjusts the volume fraction of the core part to attain the stability of the reentrant gyroid phase upon chain elongation.
(J. Phys. Soc. Jpn., 81, 094601 (2012): Paper of Editors' Choice)
[Commentary by T. Dotera at JPSJ site]


Temperature-Jump Time-Resolved X-ray Diffraction Study of Cubic-Cubic Phase-Transition Kinetics in Thermotropic Cubic Mesogen 1,2-Bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n)

Hiroyuki MORI, Shoichi KUTSUMIZU, Kazuya SAITO, Katsuhiro YAMAMOTO, Shinichi SAKURAI and Koichi SAKAJIRI

The transformation between two thermotropic bicontinuous cubic (Cub) phases has kinetically been determined by time-resolved X-ray diffraction. The system investigated was 1,2-bis(4'-n-alkoxybenzoyl)hydrazines (denoted as BABH-n, where n is the number of carbon atoms in the alkyl chain). Transitions from the Ia3d to Im3m phases of BABH-13 and from the Im3m to Ia3d phases of BABH-16 were induced by a temperature jump. Although the two Cub phases have quite different aggregation structures, the transitions between them appeared to occur without any diffractive intermediate states. A clear increase in the rate of transformation was observed upon increasing the extent of superheating, and the rate was slower than that reported previously for lyotropic systems. In addition, a comparison between the two transformations revealed that the rate of the Im3m to Ia3d transformation (of BABH-16) is ca. 5 times faster than that of Ia3d to Im3m (of BABH-13).
(Langmuir, 26, 11605 (2010))


Microphase-Separated Multicontinuous Phase in Low-Molecular-Mass Thermotropic Liquid Crystals

Kazuya SAITO

Extensive application of chemical thermodynamics to exotic aggregation formed in thermotropic liquid crystals is briefly described. Through thermodynamic analyses and considerations of experimental results on liquid crystals, the unexpected sharing of common properties by thermo- and lyotropic liquid crystals is demonstrated. In some thermotropic liquid crystals, the terminal alkyl chain attached to the molecular core is highly disordered, as indicated by the magnitude of configurational entropy. The molten chain serves as intramolecular solvent (self-solvent), as evidenced by the close similarity between phase diagrams against chain length and composition in the binary system with n-alkane. These facts lead to the quasi-binary picture of thermotropic liquid crystals. Consideration of the thermodynamic potential expanded in terms of density fluctuation gives a new insight into the multicontinuous phases formed in simple systems consisting of anisotropic, rodlike particles.
(Pure & Appl. Chem., 81, 1783 (2009), review)


Structure Analyses of Highly Symmetric Superstructures Formed by Rodlike Mesogen

Kazuya SAITO and Shoichi KUTSUMIZU

Process of structure determination of liquid-crystalline superstructures formed in a mesogenic series, bis(n-alkoxybenzoyl)hydrazine [BABH(n); n, the number of carbon atoms in the alkoxy group], is described. The chain-length (n) dependence of relative diffraction intensities from the Ia3d phase resolves the phase problem, leading to the structural description that the molecular centers are on the rods forming two interpenetrating jungle gyms. Theoretical consideration on the stability of superstructures and systematic MEM analysis reveal the coexistence of two aggregation modes (rods forming an extending jungle gym and closed sheets forming spherical shells) for the Im3m phase.
(J. Crystallogr. Soc. Jpn., 51, 169 (2009), review in Japanese)


Thermodynamic Symptom of Coexistence of Two Aggregation Modes in the Im3m Cubic Phase Formed in Thermotropic Mesogen, ANBC(n)

Kazuya SAITO, Tadahiro NAKAMOTO, Michio SORAI, Haruhiko YAO, Kenji EMA, Kunio TAKEKOSHI and Shoichi KUTSUMIZU

The heat capacities of two members of a representative cubic mesogen, 4'-alkoxy-3'-nitrobiphenyl-4-carboxylic acid, were measured precisely. In accordance with the tendency reported previously for other members, the heat capacity in the cubic phase is smaller than that in the neighboring smectic C phase. The chain-length dependence of the reduction in the heat capacity upon the phase transition showed opposing trend depending on symmetry of the cubic phase (Ia3d or Im3m). This finding is rationalized by assuming the existence of two aggregation modes (rod and shell) in the Im3m phase in contrast to only the former mode in the Ia3d phase.
(Chem. Phys. Lett., 469, 157 (2009))


Coexistence of Two Aggregation Modes in Exotic Liquid-Crystalline Superstructure: Systematic Maximum Entropy Analysis for Cubic Mesogen, 1,2-Bis(4'-n-alkoxybenzoyl)hydrazine [BABH(n)]

Kazumi OZAWA, Yasuhisa YAMAMURA, Syuma YASUZUKA, Hiroyuki MORI, Shoichi KUTSUMIZU and Kazuya SAITO

Structure of a complex superstructure self-organized by thermotropic mesogen, 1,2-bis(4'-n-alkoxybenzoyl)-hydrazine [BABH(n), where n is the number of carbon atoms in an alkoxy chain] was studied while paying special attention to the structure at the molecular level. Maximum entropy (MEM) analysis revealed that the molecular cores form two kinds of aggregates: Jungle gym with 3-fold junctions roughly on P minimal surface and spherical shells.
(J. Phys. Chem. B, 112, 12179 (2008))


Possible Formation of Multicontinuous Structures by Rodlike Particles

Kazuya SAITO, Yasuhisa YAMAMURA and Shoichi KUTSUMIZU

It is shown by extending the Landau theory of freezing that a tendency to form multicontinuous complex structures is possessed by simple systems consisting of rigid rodlike particles. The excellent stability of the Gyroid phase, which is most widely observed in nature, is naturally explained. An exotic structure found in thermotropic liquid crystals can be further regarded as an example.
(J. Phys. Soc. Jpn., 77, 093601 (2008))


Cubic Phase Formation and Interplay between Alkyl Chains and Hydrogen Bonds in 1,2-Bis(4'-n-alkoxybenzoyl)hydrazine (BABH-n)

Shoichi KUTSUMIZU, Hiroyuki MORI, Machiko FUKATAMI, Shigeharu NAITO, Koichi SAKAJIRI and Kazuya SAITO

The phase transitions of a homologous series of 1,2-bis(4'-n-alkoxybenzoyl) hydrazine (BABH-n, where n is the number of carbon atoms in the alkyl chain and in this investigation varies from 4 to 22) were investigated by differential scanning calorimetric (DSC), polarizing optical microscopic (POM), X-ray diffraction (XRD), and infrared (FT-IR) measurements. The formation of bicontinuous type cubic (Cub) mesophases was observed enantiotropically for n > 6 and only on cooling for n = 5. The structures were examined by XRD, which revealed the presence of two types with symmetries Ia3d and Im3m, depending on n, and for n = 13, 15, and 16, phase transitions between the two Cub phases were observed. The FT-IR studies elucidated the formation of intermolecular hydrogen bonding between the CdO bond of one molecule and the NH group of another molecule, whose binding strength was temperature-dependent. The temperature dependence of the Cub lattice parameter (da/dT) varied from a large positive to a large negative value with increasing alkyl chain length n, which can be well-explained in terms of the temperature-responsive shape change of the constituent molecules. The packing structures of two Ia3d-Cub phases formed by shorter and longer alkyl chain members are compared and discussed. It is revealed that two competitive mechanisms are mainly operated on the self-organization, i.e., the preferential orientation of the long axes of the aromatic core parts parallel to each other and microsegregation between the aromatic core and alkyl chain parts of the molecules; the former mechanism is effective in the shorter chain members, whereas the latter is predominant in the longer chain members.
(Chem. Mater., 20, 3675 (2008))


X-ray Studies of the Self-Organized Structure Formed by 1,2-Bis(4'-n-alkoxybenzoyl)hydrazine (BABH-n) Homologues. 1. Ia3d-Gyroid Structure

Shoichi KUTSUMIZU, Hiroyuki MORI, Machiko FUKATAMI and Kazuya SAITO

The cubic (Cub) phase structure of a thermotropic mesogen 1,2-bis(4'-n-alkoxybenzoyl) hydrazine (BABH-n, where n is the number of C atoms in the aliphatic tail) was examined by small-angle X-ray scattering. The BABH-n system exhibits two types of Cub phases, Ia3d type and Im3m type. In the phase diagram as a function of the tail length (n) the Im3m-Cub phase region (n = 13-16) was sandwiched by two Ia3d-Cub phase regions with n < 13 and n > 16. On the basis of the triply periodic minimal surface (TPMS) picture, the Ia3d and Im3m structures are described by the gyroid (G) and doubled-P (PP) surfaces, respectively. In this paper we focused attention on the internal structure of the Ia3d-Cub phase at the molecular level. By examining how the relative intensity of the 220 reflection with respect to the 211 reference peak varies with n, we have successfully determined the position of the aliphatic tails, which are located on the G-TPMSs. As far as we know, this is the first approach to clarifying the internal structure of the thermotropic Ia3d-Cub phase. The usefulness of the systematic studies with respect to the tail length n has also been demonstrated.
(J. Appl. Crystallogr., 40, s279 (2007))


Two Cubic Phases of 1,2-Bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n)

Hiroyuki MORI, Shoichi KUTSUMIZU, Takeya ITO, Machiko FUKATAMI, Kazuya SAITO, Koichi SAKAJIRI and Keiichi MORIYA

The structure type of bicontinuous cubic phase formed by 1,2-bis(4'-n-alkoxybenzoyl)hydrazines (BABH) was strongly dependent on the alkoxy chain length, showing the phase sequence of Ia3d - Im3m - Ia3d with lengthening the chain.
(Chem. Lett., 35, 362 (2006))


Cubic Phase of 4'-n-Hexadecyloxy-3'-cyanobiphenyl-4-carboxylic Acid (ACBC-16)

Shoichi KUTSUMIZU, Kazuya SAITO, Shuichi NOJIMA, Michio SORAI, Yuri G. GALYAMETDINOV, Irina GALYAMETDINOVA, Rudolf EIDENSCHINK and Wolfgang HAASE

The cubic phase structure of 4'-n-hexadecyloxy-3'-cyanobiphenyl-4-carboxylic acid (ACBC-16) was examined by X-ray diffraction. Unlike the octadecyloxy homologue showing an Im3m-type cubic phase, the cubic phase of ACBC-16 was of Ia3d type, both on heating and on cooling, similarly to the corresponding nitro-substituted analogue (ANBC-16). The lattice dimension a at 453 K was a =11.0 nm, 2.5% larger than the value for ANBC-16 and rather close to the value of ANBC-17 or -18. It is expected that the appearance of the cubic phase type, as a function of the number of carbon atoms n in the alkoxy chain in the ACBC-n series, is essentially the same as in the ANBC-n series, but shifted towards shorter n by 1 or 2. In the latter ANBC-n series, the cubic phase type is Ia3d for 15 <= n <= 18, while an Im3m type is formed for 19 <= n <= 21, both on heating and on cooling.
(Liq. Cryst., 33, 75 (2006))


Calorimetric Study of Cubic Mesogen, ACBC(16)

Michio SORAI, Kazuya SAITO, Tadahiro NAKAMOTO, Mayumi IKEDA, Yuri G. GALYAMETDINOV, Irina GALYAMETDINOVA, Rudolf EIDENSCHINK and Wolfgang HAASE

Heat capacity of cubic mesogen ACBC(16) was measured by adiabatic calorimetry.  Besides the known condensed phases, a new crystalline phase was found to undergo a glass transition around 165 K. The first-order nature of the SmC-cubic phase transition at 431.15 K was confirmed by observation of supercooling of the cubic phase for the first time.  The entropy of this transition (DeltatrsS) lies on an extrapolating line of the chain-length vs DeltatrsS plot for the SmC - Im3m transition in ANBC, suggesting nearly the same core size for ANBC and ACBC.  A broad hump in the Cp curve above the transition to isotropic liquid at 474.30 K was demonstrated to continue to a low-temperature side if the isotropic liquid was supercooled.  The experimental results are discussed in the light of the structural model of the cubic phases in the classical cubic mesogens by the authors.
(Liq. Cryst., 30, 861 (2003))


Degree of Disorder in Cubic Mesophases in Thermotropics: Thermodynamic Study of a Liquid Crystal Showing Two Cubic Mesophases

Kazuya SAITO, Takashi SHINHARA, Tadahiro NAKAMOTO, Shoichi KUTSUMIZU, Shinichi YANO and Michio SORAI

Heat capacity of a thermotropic mesogen ANBC(22) showing two cubic mesophases was measured by adiabatic calorimetry between 13 and 480 K. Excess enthalpies and entropies due to phase transitions were determined. A small thermal anomaly due to the cubic Im3m -> cubic Ia3d phase transition was successfully detected. Through an analysis of chain-length dependence of the entropy of transition, the sequence of two cubic mesophases (with space groups Ia3d and Im3m) is deduced for thermotropic mesogens ANBC( n). It is shown that the disorder of the core arrangement decreases in the order of SmC -> cubic (Im3m) -> cubic (Ia3d) while that of the chain in the reverse order cubic (Ia3d) -> cubic ( Im3m) -> SmC.
(Phys. Rev. E, 65, 031719 (2002))


Thermodynamics of Thermotropic Cubic Mesogens: Cubic Liquid Crystals as a ``Binary System'' between Molecular Cores and Conformationally Melted Alkyl Chains

Kazuya SAITO and Michio SORAI

Characteristics of cubic liquid crystals are demonstrated through heat capacity measurements, comparison of phase diagram, and analysis of chain-length dependence of the entropy of SmC -> cubic transition. Molecular structures of cubic mesogens similarly consists of a central rigid core and long terminal alkyl chains. Alkyl chains in cubic mesogens (ANBC and BABH) attain large entropy on phase transitions in the solid state, resulting in highly disordered state in liquid crystalline phases. The chains behave like a solvent in the cubic liquid crystalline phase. The phase diagrams of some cubic mesogens show that the diagram is primarily determined by attractive interaction in molecular lateral direction and by geometrical factor, but is insensitive to the details of intermolecular interaction. The chain-length dependence of DeltatrsS(SmC ->cubic) shows that the molecular core in the cubic phase is more ordered in terms of entropy than in the SmC phase whereas the chain is more disordered by 0.5 J K-1 (mol of CH 2)-1 in the cubic phase.
(EKISHO (Liq. Cryst.), 5, 20 (2001), review in Japanese)


Toward the Molecular-Statistical Modeling of the Optically Isotropic Mesophase in Neat Systems: From the Thermodynamic Point of View

Kazuya SAITO, Takashi SHINHARA and Michio SORAI

Phase diagrams of some compounds showing optically isotropic mesophases are compared as a function of the number of paraffinic carbon atoms per molecular core. In spite of a wide range of the transition temperatures, the number of paraffinic carbon atoms required for the appearance of the isotropic mesophases is limited within a narrow range, irrespective of molecular structure and/or intermolecular interaction. Combining this finding with the previous results obtained from thermodynamic studies, a possible framework toward the molecular-statistical modeling is proposed.
(Liq. Cryst., 27, 1555 (2000))


Possibility of the Isostructural Condensed States of Matter in the D Phase of ANBC and the Cubic Mesophase of BABH: Heat Capacity of 4'-n -Octadecyloxy-3'-nitrobiphenyl-4-carboxylic acid, ANBC(18)

Ayako SATO, Yasuhisa YAMAMURA, Kazuya SAITO and Michio SORAI

Heat capacity of ANBC(18) has been measured at the temperatures 8 K to 490 K by adiabatic calorimetry. All known phases were detected. The temperatures, enthalpies and entropies of transitions were determined for the phase transitions observed. On the basis of the entropy of transition to SmC phase from the D or the cubic phases, it is pointed out that the D phase of ANBC and the cubic phase of BABH might be identical in nature. It is shown that the arrangement of "molecular" core has higher degree of order in the isotropic (D and cubic) phases than in SmC phase, whereas the terminal alkoxy chains are more disordered in the isotropic phases than in SmC phase. The degrees of disorder in the D and cubic phases relative to the SmC phase are very similar in terms of the entropy of transition per methylene group. The inverted phase sequence in ANBC (SmC -> D on heating) and BABH (cubic -> SmC) can be accounted for in terms of the competing roles in the entropy between the molecular core and the chains.
(Liq. Cryst., 26, 1185 (1999))


Calorimetric Study on the Thermotropic Cubic Mesogen, 4'-n-Hexadecyloxy-3'-nitrobiphenyl-4-carboxylic acid, ANBC(16)

Ayako SATO, Kazuya SAITO and Michio SORAI

Heat capacity of ANBC(16) has been measured between 15 K and 500 K by adiabatic calorimetry. Three (one known and two newly-found) crystal-crystal phase transitions and all known liquid crystalline phases (SC , cubic D and SA) were detected. The temperatures, enthalpies and entropies of transitions were determined for all the phase transitions observed. The entropy of transition is very small for the transition from/to the cubic D mesophase. The results are compared with the thermal properties of another cubic mesogen, BABH(8). The logical possibility is pointed out that the cubic mesophases of ANBC(16) and BABH(8) are of the identical higher-order structure, while discussing why they are immiscible.
(Liq. Cryst., 26, 341 (1999))


Thermodynamic Investigation on the Thermotropic Cubic Mesogen, 1,2-Bis(4- n-octyloxybenzoyl)hydrazine

Nobuyuki MORIMOTO, Kazuya SAITO, Yasushi MORITA, Kazuhiro NAKASUJI and Michio SORAI

The molar heat capacity of the thermotropic cubic mesogen 1,2-bis(4- n-octyloxybenzoyl)hydrazine, BABH(8) for short, with a purity of 99.43 mole per cent has been precisely measured with an aduiabatic calorimeter at temperatures between 14 K and 480 K. The enthalpy and entropy gained at each phase transition across the phase sequence of {crystal(2) -> crystal(1) -> cubic mesophase -> SC -> isotropic liquid} have been determined. The existence of a solid-solid phase transition with a fairly large entropy change seems to be necessary for the alkyl moieties attached to both sides of the molecule to play the role of "solvent" in the cubic mesophase. On the basis of curvature elasticity consideration, the small energy difference between the cubic and SC phases is favorably accounted for in terms of the jointed-rod micelles model. The reason for the immiscibility of BABH(8) with the cubic D mesogen, 4'- n-hexadecyloxy-3'-nitrobiphenyl-4-carboxylic acids is discussed in terms of the large difference in their molecluar size and of the "structure breaking" arising from the admixture of heterogeneous hydrogen bonds.
(Liq. Cryst., 26, 219 (1999))


Do Alkoxy Chains Behave Like a Solvent in the D Phase?
DSC Study of Binary Systems, ANBC(nC) (n C = 8, 16 and 18) - n-Tetradecane

Kazuya SAITO, Ayako SATO and Michio SORAI

Phase behavior of the binary systems, ANBC(nC) - n-tetradecane for nC = 8, 16 and 18, was examined by using a DSC, paying a special attention to the role of the alkoxy chain of the ANBC molecule in the D phase. The dependence of the SC - D and D - isotropic liquid transition temperatures upon apparent average number of paraffinic carbon atoms closely resembles the nC dependence in a series of neat ANBC's, demonstrating that the alkoxy chain behaves, at least in part, like a solvent in lyotropic liquid crystals. The D phase was not detected in ANBC(8) - n-tetradecane.
(Liq. Cryst., 24, 525 (1998))


See also Quasi-Binary Picture of Thermotropics and Lyotropic Liquid Crystal


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