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A recently developed crystallographic algorithm revealed an unexpected interwoven network structure in chiral thermotropic liquid crystals of achiral rodlike molecules. The two networks are homochiral in network geometry and molecular arrangement.

We examined the effects of alkali metal cations, Li+, Na+, and Cs+, on the internal structures of ionic aggregates and network rearrangement via interaggregate hopping of metal carboxylates in carboxylated polyisoprene ionomers.

A one-step route to a series of perfluoronaphthalene-based donor (D)-acceptor (A)-D fluorescent dyes with various electron-donating groups was developed. The perfluoronaphthalene moiety in the D-A-D dyes served as a good electron-accepting aromatic ring with excellent intramolecular charge transfer properties, as determined by density functional theory calculations and measurements of the fluorescence properties in solution, in poly(methyl methacrylate) (PMMA) films, and in crystal form. Notably, replacing the naphthalene ring with perfluoronaphthalene in the D-A-D dyes carrying the phenothiazine moiety not only stabilized the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels but also reduced the energy band gap to change the emission color from blue to yellow. Among the four synthesized perfluoronaphthalene D-A-D dyes, those bearing diphenylamino groups afforded the best fluorescence quantum yields in Et

A range of N,N-diarylthiazol-5-amines having a 4-pyridyl group on a thiazole ring were developed, and their photophysical properties were elucidated. Their synthesis was achieved by applying our me...

Stretching vibrations of aliphatic C-D bonds at the chain end and midchain site of partially deuterated polystyrene (PS) were determined by Fourier transform infrared (FT-IR) spectroscopy. It was first found that the stretching vibration at the chain end is more rapid compared to that at the midchain site in the glassy bulk state. The difference in the frequencies of the stretching vibrations at the chain end and midchain site changed little even when the PS was dissolved in toluene. Moreover, the DFT vibrational frequency calculations showed that the C-D bonds at the end site intrinsically have higher vibrational frequency because of lower intramolecular interactions at the chain end. From these results, it was concluded that the main origin for the local rapid stretching vibration at the chain end is not intermolecular effects but reduced intramolecular interactions induced by the discontinuity of the repeating unit at the chain end.

Herein, we designed a novel polyisoprene (PI) elastomer with high mechanical properties and autonomous self-healing capability at room temperature facilitated by the coexistence of dynamic ionic crosslinks and crystalline components that slowly reassembled. We prepared amorphous cis-PI and semicrystalline trans-PI that were ionically modified with partially sodium-neutralized carboxy groups; a small amount (less than 30 wt%) of ionic trans-PI was blended with the ionic cis-PI. Nanosized ionic aggregates in the elastomers were formed by the ionic groups and they acted as physical crosslinks; the ionic network continuously rearranged at room temperature. We found that the crystalline components formed in the blended elastomers exhibited a higher degree of internal disorder owing to the miscibility of cis- and trans-PIs despite having different stereoregularities. The highly disordered crystalline components served as extra physical crosslinks that reinforced the material's mechanical strength: the modulus of the blended elastomer containing the ionic trans-PI (30 wt%) was 28 MPa at room temperature, whereas the neat ionic cis-PI was 1.2 MPa. Cut pieces of the blended elastomers reconnected at room temperature, and their self-healing efficiency was comparable to that of the neat ionic cis-PI at a trans-PI concentration below 20 wt% despite their improved moduli. Fourier transform infrared analysis revealed that the highly disordered crystalline regions in the blended samples were destroyed at the damaged faces. When the composition of the ionic trans-PI was lower than 20 wt%, the reassembly of the highly disordered crystalline regions at room temperature was slow compared with the interdiffusion process of the polymer chains between the damaged faces, and thereby self-healing was not disturbed.

Selecting 1,2-bis(aryloyl)hydrazine as a model molecular framework, this article examines how the combined modification of two molecular moieties, i.e., variation of the molecular core motif (benzene B or naphthalene N as two aromatic rings) and use of bulky and flexible siloxane segments (disiloxane Si2, trisiloxane Si3, or its branched type iSi3) at the end of both chains, affects the phase behavior including the cubic (Cub) phases such as well-known achiral Ia3d or the so-called "Im3m" phase mostly recognized as a chiral one. It was found that the use of a naphthalene core as a larger core effectively provides the compound with improved thermal stability, and the clearing temperature in the N series is ca. 50 K higher than that of the B series. On the other hand, the introduction of siloxane segments at their terminals is effective for lowering the LC-phase temperature range by several tens of K. Focusing on the Cub phases, only the introduction of the disiloxane Si2 segment was useful for their formation, and we envisioned how much degree the anti-spindle shape of the average molecular shape is in the Ia3d phase. The use of the trisiloxane Si3/iSi3 segment primarily led to the formation of columnar (Col) phases. Consideration of the chemical composition revealed that the delicate balance between the three molecular moieties, siloxane terminal, alkyl spacer, and aromatic core part, is critical for the Cub phase formation, and it can be summarized as the threshold weight fraction of the alkyl spacer in the three moieties being 0.284 or larger, which derives an anti-spindle shape favorable for the formation of the Ia3d-Cub phase.

We have developed a novel aromatic fluorine-induced one-pot synthesis of ring-perfluorinated trimethine cyanine dye without the use of a pyridine by reacting hexafluorobenzoindolenine with 5 equiv of methyl trifluoromethanesulfonate in mixed solvents of dimethylformamide and toluene. The thus-obtained ring-perfluorinated trimethine cyanine dye shows much better fluorescence properties, including intensity, quantum yield, and lifetime, than the nonfluorinated dye, not only in CH2Cl2 solution and the poly(methyl methacrylate) film but also in the powder state. Furthermore, ring-perfluorinated trimethine cyanine dye 2a shows better photostability toward white light-emitting diode irradiation than nonfluorinated dye trimethine cyanine dye 2b.

A recent intriguing finding that a helical network arrangement forms the bicontinuous cubic phase is attracting great attention for the possibility of new routes to asymmetric synthesis by achiral molecules. However, the design of the molecular structure for the cubic phase is still unrevealed. In this work, a nonsymmetric core molecule with larger naphthalene and smaller benzene moieties at each side of the central linkage and the same disiloxanyldecyloxy terminal at both terminals is shown to be the first example of molecule forming both single-layered and double-layered core assembly modes in the Ia3d phase as a single molecule system. The molecule forms the former mode at high temperatures as a thermodynamically stable phase, similarly to the symmetric naphthalene core system, whereas, on cooling below a temperature (∼350 K), a metastable Ia3d phase forms a double-layered core state down to room temperature, which is common to the benzene core system. As another effect of the nonsymmetric core, the cubic phase is maintained at room temperature for more than 100 days with slight distortion. Infrared spectral studies and quantum chemical calculations suggested the easy transformation between the two core assembly modes. The core nonsymmetry can be a versatile fine-tuning of the core assembly mode and phase stability for the cubic phase molecules.

1,2-Bis(4′-n-alkoxybenzoyl)hydrazine [BABH(n), n is the number of carbon atoms in the alkyl chain] exhibits two different Iad cubic phases depending on the chain length (5 ≤ n ≤ 13 and 15 ≤ n ≤ 22). The molecular packing modes, not only of molecular cores but also of alkyl chains, are investigated through a maximum entropy method (MEM) and an analysis of the chain-length dependence of the body diagonal of the unit cell. The analyses revealed the difference in molecular packing. The short-chain Iad structure of BABH(n) (5 ≤ n ≤ 13) is constructed by single-layered core motifs and bilayers of alkyl chains, in which the orientation is tilted from the normal to the layer. The long-chain Iad structure (15 ≤ n ≤ 22) is formed by double-layered core motifs and monolayers of alkyl chains, in which the orientation is normal to the layer. Based on the molecular packing modes, the reentrant behavior between the two Iad phases was clarified. It was revealed that the alkyl chains of BABH(n) molecules play an essential role in the formation and stability of the two Iad structures.

Optical switching between one-dimensionally ordered layered smectic C (SmC) and three-dimensionally periodic bicontinuous cubic (Cubbi) liquid-crystalline (LC) phases is a fascinating challenge bec...

Local glass transition temperatures (Tg) for ionic aggregates, in sodium-neutralized poly (ethylene-co-methacrylic acid) (EMAA) ionomers plasticized with lauric acid (LA), have been position-selectively measured by electron spin resonance (ESR). This ESR study reveales that a restricted shell region surrounds the rigid ionic core with a thickness of approximately 10 A. Here, we directly observed that the shell region is preferentially plasticized by LA. When the local shell region Tg decreases to below room temperature, while the weight fraction of LA simultaneously increases, the specimen becomes remarkably stretchable during the tensile test. Based on these results, we suggest that ionic core–shell structures, which have rubbery shells, act as a sort of loose physical cross-link, under stretching behavior, due to the tendency of some carboxylic and/or carboxylate groups, attached to highly stressed polyethylene chains, to detach from the ionic cores.

Maintenance-free self-healing elastomers that switch their mechanical properties on demand would be extremely useful materials for improving the functionalities, safety, energy efficiency, and lifetimes of many kinds of products and devices. However, strength and stretchability are conflicting properties for elastomers because the inherent crosslinking density of a polymeric network is unchangeable. For example, heavily crosslinked elastomers are strong, but poorly stretchable. Here we report an ionically crosslinked polyisoprene elastomer in which the ionic moieties are continually hopping between ionic aggregates at room temperature. Thus, the network is dynamic. This elastomer spontaneously self-heals without the input of external energy or healing agents. Furthermore, it behaves like a strong elastic material under rapid deformation, but acts like a highly stretchable and viscoelastic material under slow deformation. Our ionic elastomer shows a variety of notable mechanical properties, including high fracture strength (≈7 MPa), good toughness (≈70 MJ m−3), and ultrastretchability (>13,400%). Imparting both high strength and stretchability in polymers is challenging as it requires changing the crosslinking density of the polymer network. Here, Miwa et al. use an ionic elastomer with dynamic crosslinks to achieve high strength under rapid deformation but high stretchability under slow deformation in a single material.

The dielectric properties of self-healing dynamic ion crosslink (DIC) elastomer and its performance as a dielectric elastomer actuator (DEA) were evaluated. The relative permittivity of the DIC elastomer was approximately 3.0 and it was almost constant in the frequency range of 20–200,000 Hz and in the field strength below 2.70 V/μm at 20 Hz. The expected large-scale ionic polarization of the ionic aggregates was not observed under the electric field examined. The maximum blocking stress of the DEA using the DIC elastomer (DIC-DEA) was much larger (approximately 22.6 times) than that of the DEA using a commercial tape (VHB4910) (VHB-DEA). This is brought by the advantage that the breakdown strength of DIC-DEA is much higher than that of VHB-DEA. The Young’s modulus of DIC showed a peculiar behavior; it was higher (1.4 times) under an electric field (3.00 V/μm) than in the absence of an electric field (0.39 ± 0.07 MPa). The maximum blocking stress at 1.0 kV/s was the same as that at 0.2 kV/s. This would reflect the fact that the blocking stress is independent of the Young’s modulus as a function of the deformation rate. In addition, cut DIC elastomer reconnected at room temperature, and the blocking stresses at 5.80 V/μm of the self-healed DIC-DEA was the same as that of the prior-to-cut DIC-DEA, regardless of the rate of change of voltage. These results suggest that DIC-DEA is a sustainable DEA that exhibits no deterioration of the performance because of its self-healing behavior even after the mechanical damage.

Chemical or electrochemical one‐electron oxidation of 5‐N‐arylaminothiazoles was found to afford stable radical cations. For chemical oxidation, 1 equivalent of [(4‐BrC6H4)3N][SbCl6] (Magic Blue, MB) was added to CH2Cl2 solutions of the thiazoles, and the thus‐obtained radicals showed light absorption in the near‐infrared region. Electrochemical oxidation also led to bathochromic shifts in the absorption bands, and the obtained spectra were similar to those derived from the chemically oxidized species. These radicals afforded electron paramagnetic resonance (EPR) spectra that are consistent with the notion of stable nitrogen radicals (half‐life≤385 h). The EPR spectrum of a thiazole containing 4‐dimethylaminophenyl groups on the nitrogen atom at the 5‐position changed significantly upon adding >3 equivalents of MB. Details of the electronic structures of the experimentally obtained radical cations were generated from theoretical calculations.

To compromise high mechanical strength and efficient self-healing capability in an elastomer with dynamic crosslinks, optimization of the molecular structure is crucial in addition to the tuning of the dynamic properties of the crosslinks. Herein, we studied the effects of molecular weight, content of carboxy groups, and neutralization level of ionically crosslinked polyisoprene (PI) elastomers on their morphology, network rearrangement behavior, and self-healing and mechanical properties. In this PI elastomer, nanosized sphere-shaped ionic aggregates are formed by both neutralized and non-neutralized carboxy groups that act as stickers. The number density of the ionic aggregates that act as physical crosslinks increased with increase in the stickers’ concentration, although the size of the ionic aggregates was independent of the molecular weight and the stickers’ concentration. The ionic network was dynamically rearranged by the stickers’ hopping between the ionic aggregates, and the rearrangement was accelerated by decreasing the neutralization level. We found that the 2Rg of the PI must be significantly larger than the average distance between the ionic aggregates to obtain a mechanically strong PI elastomer. We also found that further increase in the molecular weight is effective to enhance the dimensional stability of the elastomer. However, this approach reduced the elastomer's self-healing rate at the same time because the diffusion and randomization of the polymer chains between the damaged faces were reduced. In this work, we clearly demonstrated the principle in the optimization of the molecular structure for the ionically crosslinked PI elastomers to tune the mechanical and autonomous self-healing properties.

1,2-Bis(4'-n-alkoxybenzoyl)hydrazine [BABH(n), n is the number of carbon atoms in the alkyl chain] exhibits two different Ia3[combining macron]d cubic phases depending on the chain length (5 ≤n≤ 13 and 15 ≤n≤ 22). The molecular packing modes, not only of molecular cores but also of alkyl chains, are investigated through a maximum entropy method (MEM) and an analysis of the chain-length dependence of the body diagonal of the unit cell. The analyses revealed the difference in molecular packing. The short-chain Ia3[combining macron]d structure of BABH(n) (5 ≤n≤ 13) is constructed by single-layered core motifs and bilayers of alkyl chains, in which the orientation is tilted from the normal to the layer. The long-chain Ia3[combining macron]d structure (15 ≤n≤ 22) is formed by double-layered core motifs and monolayers of alkyl chains, in which the orientation is normal to the layer. Based on the molecular packing modes, the reentrant behavior between the two Ia3[combining macron]d phases was clarified. It was revealed that the alkyl chains of BABH(n) molecules play an essential role in the formation and stability of the two Ia3[combining macron]d structures.

Treatment of pyridyl-5-aminothiazoles (1–4) with alkyl triflates or benzyl iodide afforded the corresponding pyridinium 5-aminothiazoles (5–10), which exhibited bathochromically shifted absorption and fluorescence spectra relative to those of 1–4. Moreover, the vapochromic properties of 5 specific to halogenated solvents were examined by powder X-ray diffraction analysis. Pmma films containing 5 can thus be used to detect halogenated solvents, especially CH2Cl2.

Herein, we suggest the importance of the rigidness of the shell region surrounding the ionic core in controlling the tensile mechanical properties of sodium-neutralized poly(ethylene-co-methacrylic acid) (EMAA) ionomers blended with several fatty acids with different alkyl tail lengths. When dodecyl acid (DA) or lauric acid (LA) was blended, the local Tg of most of the shell region decreased to lower than room temperature, whereas the ionic core was still glassy at room temperature. However, the local Tg of the shell region was almost equal to room temperature when stearic acid or behenic acid was blended. The EMAA ionomers blended with DA and LA exhibited higher stretchability and toughness in the tensile test and shorter relaxation time in the stress–relaxation test than the other samples because some neutralized and/or unneutralized carboxy groups attached to highly stressed polyethylene chains detachfrom the ionic cores when the shell region was soft.

Rational design of molecules that exhibit a thermotropic bicontinuous cubic (Cub) phase has been earnestly desired. In this work, we describe the suitable selection of a molecular motif that has enabled the systematic exploitation of eight new series of Cub-phase molecules with symmetric molecular cores, N-n (1), PB-n (2), S-n (3), and PEB-n (4), and unsymmetric cores, B-N-n (5), B-PB-n (6), B-S-n (7), and B-PEB-n (8). These eight series all originate from achiral chain-core-chain type rod-like molecules that exhibit two types of Cub phases, an achiral Ia3d phase, and a chiral phase. All the Ia3d phases formed were found to be isomorphous structures, with their cell dimensions being proportional to the core size, and the same was true for the latter chiral phase. We demonstrated that the formation is mainly governed by the segregation between core and alkyl moieties of the molecules, and thus, by the weight fraction of the core portion fcore. This work also demonstrates that the central dicarbonylhydrazine linkage bearing intermolecular hydrogen bonding ability exhibits a pinning effect that prevents slippage of π-stacks of molecules, which is critical for the formation of the two Cub phases that are composed of chiral networks with twisted molecular arrangements. In each series, the emergence of spontaneous chirality formation that occurred in the chiral phase was limited to between 0.36 and 0.50 in the range of fcore. An interesting insight was that the introduced unsymmetry of the molecular core strongly influenced the phase behavior, which lowered the temperature range of Cub phases to around that of the smallest core series B-n, while the high temperature limit (Tc) was roughly proportional to the core size, as determined by the strength of intermolecular π-π interactions.

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.

The introduction of oligodimethyl siloxane segments at the termini of the alkyl tails has been employed to stabilize the bicontinuous cubic (Cub(bi)) phase of a chain-core-chain type molecule having a 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" indicates the two chains being the same, whereas the last one is asymmetric with respect to the core. The phase behaviors were examined by using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction techniques. All three compounds form Cub(bi) phases and their syntheses were compared including their parent compound bis-C18. It was clearly revealed that the introduction of oligodimethyl siloxane segments effectively suppresses the crystallization at low temperatures, and as a result stabilizes the Cub(bi) 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 self-assembly process in the Cub(bi) phases. The study also revealed that the introduction of oligodimethyl siloxane segments is not only an alternative for the hydrocarbon segment but also is able to provide a versatile design strategy for obtaining stable Cub(bi) phases.

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.

A series of 5-N-arylaminothiazoles was prepared by reacting thioamide dianions derived from secondary thioamides with thioformamides, followed by sequential oxidation with iodine. X-ray analyses demonstrated that they adopt structures that are highly twisted from planar conformations. Their orientations were tuned by the steric and/or electronic interactions of the substituents at their 2-, 4-, and 5-positions. The 5-aminothiazoles exhibited a range of fluorescent emissions, from blue to orange. Although the absorption spectra were independent of the polarity of the solvent, fluorescent emissions were influenced by the polarity of the solvent: in more polar solvents, the emissions were red-shifted. These phenomena were examined in terms of Lippert-Mataga plots and the change in the dipole moment between the ground and excited states. They also exhibited emissions in the solid state, again from blue to orange. Cyclic voltammetry of the 5-aminothiazoles showed reversible waves of one-electron oxidation. The half-potential of the oxidation was reduced by the introduction of electron-donating groups to the phenyl groups on the nitrogen atom at the 5-position. DFT calculations were carried out to determine the energy levels of the HOMO and LUMO. Finally, the results of TG-DTA showed that they are thermally stable.

Changes in intermolecular interactions and molecular geometry for two kinds of thermotropic cubic mesogenes, 4′-n-alkoxy-3′-nitrobiphenyl-4-carboxlic acid (denoted as ANBC-n, where n represents the number of carbon atoms in the alkoxy group) and 1,2-bis(4′-n-alkoxybenzoyl)hydrazines (BABH-n), at liquid crystal (LC) phase transitions were revealed utilizing the frequency shifts in Fourier transform infrared (FT-IR) bands as a guide. The ANBC-n and BABH-n form two kinds of bicontinuous cubic (Cubbi), Ia3d and Im3m types, and smectic LC phases depending on the length of the alkyl chain and temperature. In the present work, two kinds of phase transitions, i.e., smectic C ↔ Ia3d-Cubbi phase transition for the ANBC-16 and BABH-9 and Ia3d-Cubbi ↔ Im3m-Cubbi phase transition for the BABH-13 and BABH-16, were examined, and the experimental result was compared to the entropy changes predicted by the quasibinary picture model. In this model, it is postulated that the basic units in the BABH-n and ANBC-n, i.e., the “...

Glass transition temperature ( T g ) and vibrational properties at the chain end of polystyrene (PS) were selectively determined by a novel method utilizing Fourier transform infrared (FT-IR) spectroscopy. In this method, PSs having almost the same number average molecular weight ( M n ) but selectively deuterated at different sites, midchain (M-PS, M n = 10.7 kDa) or chain end (E-PS, M n = 10.3 kDa), were synthesized and the asymmetric stretching vibration of the main chain CD 2 ( ν as (CD 2 )) were analyzed in detail. We found that the temperature dependence of the ν as (CD 2 ) frequency shows a clear inflection at the calorimetric T g of PS. The inflection temperature was defined as T g,FTIR , which represents the T g at the local region around the deuterated sites. Although higher segmental mobility at the chain end had been shown above the T g in our earlier work, this study found that the T g,FTIR s of the M-PS and E-PS are the same. From this result, it was concluded that the chain ends move cooperatively with numerous neighboring other segments, averaging out those mobilities at temperatures around the T g . On the other hand, the ν as (CD 2 ) frequency of the E-PS was by a few cm −1 higher than that of the M-PS for any temperature. This was explained in terms of the discontinuity of the repeat unit at the chain end resulting in reduced interactions between repeat units along the chain.

We have synthesized a novel type of donor–acceptor liquid crystalline material, phthalocyanine-fullerene ( Pc - C 60) dyad, [m,p,m′-( C 14 O )3 PhO ]6 PcCu - C 60 (7), and the Pc precursors, [m,p,m′-( C 14 O )3 PhO ]6 PcCu - OFBA (6) and [m,p,m′-( C 14 O )3 PhO ]6 PcCu - OH (5), and established their mesomorphism by using a polarizing optical microscope, a differential scanning calorimeter and a small angle X-ray diffractometer. Very interestingly, their corresponding previous parent Pc derivative, [m,p,m′-( C 14 O )3 PhO ]8 PcCu (4), shows a very wide temperature region ca. 90°C of a bicontinuous Cub(Pn3m) mesophase, whereas the present children Pc precursors (5 and 6) and Pc- C 60 dyad 7 show not the Cub mesophase but a Colho mesophase. It is also noteworthy that the staking distance in the Colho mesophase of the Pc- C 60 dyad 7was a very big value of ca. 9.1 Å, which is the biggest in discotic liquid crystals to our best knowledge. It may be originated from the biggest excluded volume caused by thermal fluctuation of peripheral long alkoxy chains at m, m′-positions. The excluded volume caused by thermal fluctuation of the peripheral long chains is so big that the molecular shape of the Pc derivative 4 and the Pc- C 60 dyad 7 very resembles a flat pumpkin.

Phase transition 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.

The phase behaviour of the thermotropic cubic mesogen 1,2-bis(4′-n-hexyloxybenzoyl)hydrazine [BABH(6)] was investigated under pressure up to about 55 MPa using a polarising 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 the Cub and SmC phases exhibited a negative slope dT/dP of about –1.0 oC MPa−1.

To investigate the influence of the number of substituents on supramolecular assemblies of hydrogen-bonded disk-like (phenylethynyl)benzene derivatives with chiral L-alanine dodecyl groups, a tris(...

A local glass transition temperature, Tg, around ionic aggregates in poly(ethylene-random-methacrylic acid) (E-MAA) ionomers neutralized with sodium has been studied by the combination of the position-selective spin probing and microwave power saturation method of electron spin resonance (ESR). 5DSA, 7DSA, 10DSA, and 12DSA spin probes based on stearic acid allowed us to determine the local Tg at different distances from the center of the ionic core (multiplet), whereas 10DND probe based on a nonadecane backbone reflected the Tg at the polyethylene (PE) matrix. The local Tgs at the ionic multiplet itself and matrix region were determined to be 320 and 281 K, respectively, in the quenched E-MAA ionomer from the melt. Moreover, it was found that the region around the multiplets is dynamically restricted, and the thickness of the restricted region is ca. 10 A. In the restricted region, the Tg gradually decreased with receding from the ionic multiplet. The thickness of the dynamically restricted region was in ...

This review article focuses on recent advances and challenges in the field of thermotropic cubic phases of the bicontinuous type (Cubbi) formed by low molecular mass molecules. In the Cubbi phases, the constituent molecules self-organize into 3D network structures, although local molecular diffusional motions are preserved to some extent. This review illustrates which types of molecules form such structures, and summarizes the latest developments in structural characterization. Moreover, their phase behaviors, and analogies and differences in comparison with other related systems such as lyotropic liquid crystals and block copolymers are discussed. Finally, potential applications utilizing the dynamically ordered 3D network structures are presented.

The effect of pressure on the Im3m cubic phase of 1,2-bis(4'-n-tetradecyloxybenzoyl)hydrazine (BABH-14) was studied under pressures up to about 80 MPa using a wide-angle X-ray diffractometer equipped with a high-pressure system. The Im3m type cubic phase is held at pressures up to about 17 MPa and then transformed into the Ia3d type cubic phase under higher pressures. The Im3m–Ia3d cubic transition is reversible during an isothermal pressure cycling. Applying higher pressure induces a high-pressure smectic C phase.

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).

The phase behaviour of a homologous series of thermotropic cubic mesogens of 1,2-bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n, where n is the number of carbon atoms in both terminal alkoxy chains, ranging from n = 11 to n = 18) was studied under hydrostatic pressure using a polarising optical microscope (POM) equipped with a high-pressure optical cell. Pressure-temperature phase diagrams were constructed for all the samples. All of the samples showed the crystal (Cr)–cubic (Cub)–isotropic liquid (I) phase sequence under atmospheric and lower pressures, but the Cub phase was replaced completely by a high-pressure smectic C (SmC) phase; SmC(hp), under higher pressures. There is an intermediate-pressure region as a boundary in which the Cr–SmC(hp)–Cub–I phase sequence was recognised. The SmC(hp)–Cub transition lines showed positive slopes with pressure and shifted to higher pressures with increasing alkoxy chain length in BABH-n. What should noted here is the inversion of the Cub and SmC phases in the phase seq...

The phase behaviour of a thermotropic cubic mesogen of 1,2-bis(4′-n-tetradecyloxybenzoyl)hydrazine BABH-14 was studied under hydrostatic pressure using a polarising optical microscope equipped with a high-pressure optical cell, and the P–T phase diagram was constructed. BABH-14 shows the Cr–Cub–I transition sequence under atmospheric and lower pressures, but the Cub phase is replaced completely by the high-pressure SmC, SmC(hp), phase under higher pressures. There is a narrow intermediate-pressure region between the low- and high-pressure regions, in which the Cr–SmC(hp)–Cub–I phase sequence is recognised. The SmC(hp)–Cub transition line has a positive slope with pressure and there are two triple points: one is for the Cr, Cub and SmC(hp) phases and the other is for the I, Cub and SmC(hp) phases. Comparing the phase sequence of BABH-14 with those for BABH-8 and -10, the pressure-induced inversion of the phase sequence between the cubic and SmC phases occurs in the BABH-n homologous compounds. Another new ...

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.

Smectic C (SmC) to cubic (Cub) phase transition behavior of 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-22) and alternating-current (AC) electric field effect on the SmC phase were examined. The most important and unexpected finding is that even at a temperature 8 K below the zero-field SmC to Cub phase transition temperature (T(SmC-Cub) approximately 408 K) determined previously for the compound and without field, the Cub phase growth occurs, after a very long induction period of several hours. The X-ray diffraction measurements revealed the formation of an Im3m-type Cub phase at the temperature. It is suggested that the "true" transition temperature, which is difficult to determine precisely, exists around 396 K. The time-dependence of the Cub phase growth both without field and under field was analyzed using the well-known Avrami equation, implying the nucleation and growth mechanism mainly operating in the SmC to Cub phase transformation. The fact uncovered is that between 408 and 396 K, the SmC to Cub transformation is virtually prohibited by the strongly limited nucleation. It is concluded that the effect of the electric field on the transition is to promote the nucleation of the Cub phase in the temperature region where the Cub phase is potentially more stable than the precursory SmC phase.

The phase transitions of a homologous series of 1,2-bis(4′-n-alkoxybenzoyl)hydrazines (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 C═O 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 v...

The self-assembly of tris(phenylisoxazolyl)benzene 1b with photochemically addressable azobenzene moieties produced toroidal nanostructures, the formation and dissociation of which were reversibly regulated upon photoirradiation. 1b displayed a mesogenic behavior. In the solution, the stacked assemblies along with their C3 axes were formed. In the mesophase, two molecules of 1b most likely adopted the antiparallel arrangement to stabilize the columnar organization. This assembling behavior most likely triggered the development of the supramolecular toroidal nanostructures.

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 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.

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.