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Light-emitting materials based on earth-abundant metals, such as manganese hold great promise as emitters for organic lighting devices. In order to apply such emitter materials and, in particular, to overcome the problem of self-quenching due to cross-relaxation, we investigated a series of tetrabromidomanganate ([MnBr4]2−) salts with bulky tetraalkylphosphonium counter cations [Pnnn]+, namely [Pnnnn]2[MnBr4] (n = 4 (1), 6 (2) and 8 (3)), which can be obtained by a straightforward reaction of the respective phosphonium bromide and MnBr2. Variation of the cation size allows control of the properties of the resulting ionic materials. 1 and 3 qualify as ionic liquids (ILs), where 1 features a melting point of 68 °C, and 3 is liquid at room temperature and even at very low temperatures. Furthermore, 1 and 2 show the formation of higher-ordered thermotropic mesophases. For 1 a transition to a thermodynamically metastable smectic liquid crystalline phase can be observed at room temperature upon reheating from the metastable glassy state; 2 appears to form a plastic crystalline phase at ∼63 °C, which persists up to the melting point of 235 °C. The photoemission is greatly affected by phase behaviour and ion dynamics. A photoluminescence quantum yield of 61% could be achieved, by balancing the increase in Mn2+-Mn2+ separation and reducing self-quenching through increasingly large organic cations which leads to adverse increased vibrational quenching. Compared to analogous ammonium compounds, which have been promoted as äinorganic hybrid perovskitesä, the phosphonium salts show superior performance, with respect to photoluminescent quantum yield and thermal and air/humidity stability. As the presented compounds are not sensitive to the atmosphere, in particular moisture, and show strong visible electroluminescence in the green region of light, they are important emitter materials for use in organic light-emitting devices. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and self-assembly of a new class of amphiphilic azo dyes derived from a plant-based phenol, cardanol. Analysis of the self-assembly of these new azo derivatives was intriguing, and they exhibit some unique nanostructures, such as bicelles and microgel-like structures, and smectic-type thermotropic mesophases. [ABSTRACT FROM AUTHOR]

The introduction of structural asymmetry in metallomesogens is an established strategy to improve their mesomorphic behaviour in terms of lower melting temperatures and higher stability ranges of the mesophase, which is particularly important for metallomesogens that have potential application as electrolytes that require wide operational temperature ranges. Here in this work, a novel series of unsymmetrical bis(isoquinolinylpyrazolate)palladium(II) compounds bearing four alkyl side-chains with different lengths are described. Rectangular and hexagonal columnar mesophases were formed with low melting temperatures of 42–45 °C in most cases, whereas the clearing temperatures reached values up to 412 °C. The charge transport properties have been studied by complex impedance spectroscopy, showing that the mesophase favours proton conduction in the absence of water or humidity. The exceptional thermal stability of these species makes them promising candidates to act as a platform for ionic conduction via the nanochannels originated in the columnar mesophases. The results presented confirm that introducing structural asymmetry in the Pd(II) metallomesogens studied is a valid strategy to enhance the liquid crystalline properties, which opens new ways to develop water-free electrolytes based on unsymmetrical bis(isoquinolinylpyrazolate) Pd(II) compounds for potential applications such as proton exchange membranes (PEMs). [ABSTRACT FROM AUTHOR]

Strongly halogen-bonded complexes are formed between 4-alkoxyphenyl-4-pyridines and iodine as well as the interhalogen compounds ICl and IBr, and examples of each are characterised by single crystal X-ray crystallography. On heating, all but one of the complexes display a liquid-crystalline smectic A phase, although there is evidence of decomposition as the materials are heated through the mesophase. For such short molecules, the mesophases are rather stable and small-angle X-ray scattering shows that the complexes form a type of antiparallel, head-to-head dimeric arrangement in the mesophase. Quantum chemical calculations at the DFT (M06-2X) and MP2 levels of theory show the complexes to have very high dipole moments (between ≈ 9–12 D) and the mesophase stability of the complexes is rationalised in terms of antiparallel correlations induced by the strong molecular dipoles. [ABSTRACT FROM AUTHOR]

Photoresponsive nanostructured materials are of great importance for photonic applications. Herein we report the design, synthesis, and liquid crystal (LC) self-assembly of two new series of photoresponsive hockey-stick LCs (HSLCs). The new HSLCs are azobenzene-based polycatenars derived from the 4-cyanoresorcinol bent-core unit. The long arm is a fork-like triple alkoxylated wing, while the short arm is terminated with a single variable alkoxy chain. The molecular self-assembly of these HSLCs is characterized using polarizing optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electro optical measurements. In both series of LC materials differing in the chain volume at the crowded end, wide temperature ranges of lamellar Smectic A phases (up to 170 K) are observed beside achiral isotropic liquid phases (Iso1) for the shorter derivatives. On chain elongation helical self-assembly of the π-conjugated rods in networks occurs resulting in the formation of nanostructured bicontinuous cubic network phases with Ia3¯d space group (Cubbi/Ia3¯d), in most cases stable even around room temperatures on cooling. At the transition from SmA to Cubbi phases, an additional unknown three-dimensional (3D) phase is formed. A possible explanation for the disappearance of the triple network Cubbi phases with I23 symmetry (Cubbi[*]/I23) in these HSLCs is represented based on the phase behaviour of a new material having the central 4-cyanoresorcinol unit shifted to a terminal position of the rod-like core. Finally, the reversible trans–cis photoisomerization for some selected examples was investigated in chloroform solution. [ABSTRACT FROM AUTHOR]

Multiple mesophases, including the smectic A phase (Sm A), chiral nematic phase (N*), and blue phase (BP I), were seen in a series of non-symmetric bent mesogenic dimers containing a cholesteryl benzoate group. FTIR, 1H-NMR, DSC, POM, UV, and XRD were used to analyze the chemical structure and liquid crystal characteristics of the dimers. The phase transition occurred when the azobenzene structure was treated with UV light, changing the structure of the molecules. There is evidence that when the length of the terminal alkoxy chain is longer than the flexible spacer, it exhibits a smectic A phase as well as a chiral nematic phase; however, when the length of the flexible spacer is shorter than the length of the terminal alkoxy chain, it only exhibits a chiral nematic phase. [ABSTRACT FROM AUTHOR]

A single-head/single-tail surfactant with a polymerizable group at each end is presented as a new simplified motif for intrinsically cross-linkable, gyroid-phase lyotropic mesogens. The resulting nanoporous polymer networks exhibit excellent structural stability in various solvents and are capable of molecular size discrimination. [ABSTRACT FROM AUTHOR]

A mononuclear ruthenium(II), [(L1IQ)Ru2+(PPh3)2Cl2]·CHCl3 (1·CHCl3), a di-ruthenium(II , II), [(L2IQ)2Ru24+Cl4(PPh3)2] (2) and a mixed-valence di-ruthenium(II , III), [(L3IQ)Ru25+Cl5(PPh3)2]·MeOH (3·MeOH) complex, where L1IQ, L2IQ and L3IQ are, respectively, o-diiminobenzoquinone forms of redox non-innocent N-(5-nitropyridyl)-o-phenylenediamine (L1H2), N-(2,4-dinitrophenyl)-o-phenylenediamine (L2H2) and N-(3-nitropyridyl)-o-phenylenediamine (L3H2) derivatives, were successfully isolated. The molecular and electronic structures of 1·CHCl3, 2 and 3·MeOH were confirmed by single-crystal X-ray crystallography, EPR, UV-Vis-NIR spectroscopies and density functional theory (DFT) calculations. Both 1·CHCl3 and 2 exhibited reversible anodic waves due to the Ru(III)/Ru(II) redox couple, while the cyclic voltammogram of 3·MeOH displayed two successive cathodic waves due to ruthenium(III)/ruthenium(II) and (L3IQ/L3ISQ) redox couples. EPR spectroscopy and DFT calculations inferred that 1+ is a ruthenium(III) complex of L1IQ, [(L1IQ)Ru3+(PPh3)2Cl2]+, 2+ is a mixed-valence di-ruthenium(II , III) complex of L2IQ, [(L2IQ)2Ru25+Cl4(PPh3)2]+ and 3− is a di-ruthenium(II , II) complex, [(L3IQ)Ru24+Cl5(PPh3)2]−, while 32− is a di-ruthenium(II , II) complex of L3ISQ, [(L3ISQ)Ru24+Cl5(PPh3)2]2−, where L3ISQ is the o-diiminobenzosemiquinonate anion radical form of the L3H2 with a significant contribution of the mixed-valence di-ruthenium(III , II) form, [(L3AM)Ru25+Cl5(PPh3)2]2− (L3AM is the di-amido form of the L3H2 ligand). The spin density obtained from the Mulliken spin population analyses of the broken-symmetry (BS) DFT calculations was localized on Ru(2) in 3, while it was delocalized over both Ru(1) and the o-phenylenediamine fragment in 32−. The inter-valence charge-transfer (IVCT) transitions of 2+ and 3 were relatively weaker and occurred at 1680 and 1685 nm, respectively, while 32− exhibited a broader NIR absorption band at 1500–2000 nm. The calculated electronic-coupling parameters (Hab) using the Mulliken–Hush equation for 3 and 2+ ion, respectively, were 62 and 103 cm−1, defining these as Robin–Day class II mixed-valence systems. [ABSTRACT FROM AUTHOR]

Phytantriol-based lipidic mesophases (LMs) are introduced as a platform for cryoenzymology, which relies on the presence of liquid water in LMs at subzero temperatures. After incorporation into LMs, the model enzyme Benzaldehyde lyase (BAL) shows high cryogenic stability and activity. In contrast, BAL in bulk solution undergoes significant secondary structural transitions caused by low temperatures (cold denaturation), demonstrating the potential of this approach to enable in meso cryoenzymology. [ABSTRACT FROM AUTHOR]

Herein, we aim to investigate the influence of the cooling rate from the melt on stereocomplex formation of equimolar blends of enantiomeric star-shaped poly(lactide)s with a dipyridamole core. As evidenced by differential scanning calorimetry, wide-angle X-ray scattering and Fourier-transform infrared spectroscopy, melt cooling of equimolar blends of star-shaped poly(L -lactide) (SSPLLA) and star-shaped poly(D -lactide) (SSPDLA) resulted in the non-crystalline state. A careful analysis of WAXS and FTIR data revealed that the slow-cooled sample (10 °C min−1) exhibited the amorphous phase and the fast-cooled sample (50 °C min−1) resulted in the mesophase. On subsequent heating, the slow-cooled sample remained in the amorphous phase, whereas the fast-cooled sample crystallized (cold crystallization) exclusively into the stereocomplex at ∼90 °C. Aging of the slow-cooled sample at room temperature and subsequent heating led to the formation of the stereocomplex. Photoluminescence studies revealed that the cooling rate from the melt has a strong influence on core molecule (dipyridamole) aggregation and determines the geometry of interactions between the branches of SSPLLA and SSPDLA. In the slow-cooled sample, because of the longer residence time above the glass transition temperature, dipyridamole molecules form aggregated structures, whereas in the fast-cooled sample, dipyridamole molecules are distributed within the polymer matrix without much aggregation. Based on these results, we propose antiparallel chain packing in fast-cooled SSPLLA/SSPDLA blends because of the non-aggregation of dipyridamole core molecules and this geometry favored the exclusive formation of stereocomplex. On the other hand, due to the possible aggregation of dipyridamole molecules, the slow-cooled sample led to topological and geometric constraints where the interactions between SSPLLA and SSPDLA chains prevented the crystallization. The present findings could open new avenues for the design of a variety of macromolecular architectures for a better understanding of the stereocomplex formation mechanism of chiral polymers. [ABSTRACT FROM AUTHOR]

A new family of supramolecular liquid crystalline compounds with a calix[4]arene core and two linking groups appended on four sides, exhibiting a wide range of hexagonal columnar phases, has been synthesised and well characterised. The liquid crystal behaviour of the novel materials was studied by using polarising optical microscopy (POM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and was further confirmed using high-temperature powder X-ray diffraction (XRD). An electrochemical study was carried out using cyclic voltammetry (CV) and the results were compared with theoretical values obtained from a DFT study. These compounds showed light sky-blue luminescence in solution and as a thin film under long-wavelength UV light. It was observed that all the prepared target compounds exhibited enantiotropic mesophases with good thermal stability. The structural and conformational characterisation of these new compounds was achieved using various spectroscopic techniques, including FT-IR, 1H NMR, 13C NMR and MALDI-TOF. The relationship between the structure and the mesomorphic behaviour of the compounds containing an ethyl bridge with linked ester groups (5a–5d) is discussed. This new class of supramolecular derivatives is promising, especially considering the emissive nature and stabilisation of their columnar hexagonal mesophases, and their high range of thermal stability. [ABSTRACT FROM AUTHOR]

Pressure effect is of great importance in injection and compression of poly(L -lactide) (PLLA). However, pressure induced crystallization (PIC) and structural change of PLLA have not been thoroughly studied. In this study, we investigated PIC and structure transitions of PLLA using in situ WAXS and SAXS. A mixture of α′ and α crystals were observed at temperatures above 170 °C at high pressures. A frustrated structure was induced at Pc ≥ 100 MPa owing to sliding of chains and crystal blocks upon volume shrinkage. A mesomorphic phase was observed at Pc ≥ 100 MPa or at 190 °C ≥ Tc ≥ 165 °C by SAXS and WAXS. Upon heating the samples prepared at high Pc, doubling lamellar thickening occurred via mutual chain rearrangement between the adjacent lamellae. Based on the results, a phase diagram was revealed for the crystal structures formed and under different crystallization conditions. [ABSTRACT FROM AUTHOR]

The bottleneck for the application and potential utilization of polybutenene-1 (PB-1) with excellent physical and mechanical properties is its inevitable phase transition. An additive to PB-1 (trade name TAB-1) that accelerates this transition was used to enhance the transition and explore its mechanism with DSC and X-ray techniques. It was found that TAB-1 could enhance the transition efficiently. The total crystallinity of form II and form I rises in the initial stage of the transition. The crystallization temperature-related transitions of neat PB-1 and PB-1 containing 2 wt% TAB-1 were investigated. When form II was crystallized at lower and higher temperatures, then cooled to the same temperature and heated to the same temperature, the "more stable" form II that formed at higher temperature transformed into form I faster than the "less stable" form II that formed at lower temperature. A possible mechanism of the enhanced crystal transition of PB-1 containing TAB-1 was proposed and discussed. The formation of form I triggers the transition, and the key to form I formation is the form II-related packed-mesophase during the transition. [ABSTRACT FROM AUTHOR]

A series of three triphenylene compounds – denoted 2,7-THTP-DiCnOH – bearing four hexyloxy ancillary chains and two variable-length alkoxy chains terminally functionalized with hydroxyl groups have been synthesized and characterized. The studied compounds exhibited thermotropic mesomorphism; the detailed nature of the mesophases was found to depend on the relative positions of the terminal functional groups relative to the crown formed by the ancillary chains. All the studied compounds were able to act as supramolecular gelators in a variety of alcohols; their organogelating ability has been rationalized in terms of physicochemical parameters like the dielectric constant, which allowed us to establish very precise predictive "solvent gelation windows" for each compound. Remarkably stable gels have been detected for 2,7-THTP-DiC6OH in methanol. As a proof of principle, we present the water sensing performance as a rapid method for the assessment of water content in alcohol samples based on the influence that the water content exerts on the gels' thermostability. [ABSTRACT FROM AUTHOR]

The enantiomer separation of a chiral Tröger's base analog and its use, as an optically active building block, in the construction of molecular superstructures are presented. Various strategies are illustrated here for the attachment of azo photoswitches to the Tröger's base scaffold without racemizing its stereogenic centers. The resulting optically active photoswitches introduced chirality, thermochromic, and phototunable properties to an achiral liquid crystal host. The doped mesophases reflected specific wavelengths of light owing to the formation of self-organized helical superstructures. These observations illustrate the potential use of the presented products as liquid crystal dopants. [ABSTRACT FROM AUTHOR]

Organoboron complexes are considered to be an important class of optically dynamic materials and because of their imperative properties, they have been unceasingly studied in a wide range of scientific areas. In this context, a new family of D–A–D′ architectured boron difluoride complexes FB1–4 derived from arylhydrazones HZ1–4 has been synthesized and characterized. The work also deliberates detailed studies on their thermal, self-assembling and optoelectronic properties with respect to structural modifications. The systematic studies reveal that the new arylhydrazone ligands and their BF2 complexes exhibit a prospective columnar mesomorphism with different 2D lattice geometries at room temperature, owing to their critical structural features. Interestingly, an unusual morphological cross-over from a columnar hexagonal to rectangular mesophase has been confirmed in one of the investigated pseudo-discoidal boron complexes, FB4. The optoelectronic studies showcased their ICT dominating dye properties. Finally, the experimental results have been consciously correlated with quantum chemical simulations. [ABSTRACT FROM AUTHOR]

A method is introduced to measure residual chemical shift anisotropies conveniently and accurately in the mesophase of poly-γ-(benzyl-l-glutamate). The alignment amplitude is substantially enhanced over common methods which greatly benefits measurements particularly on sp3 carbons. The approach offers significant improvements in data accuracy and utility for small molecule structure determination. [ABSTRACT FROM AUTHOR]

A new approach accompanied by superstructural frustration is reported. By attaching a cholesterol moiety directly to the central bent-core system it displayed exotic BPIII, BPII/I, Ncyb*, TGBA, SmAPA, SmA and SmX phases as shown by X-ray scattering results. While higher homologues of the series exhibited spontaneous formation of polar order (Ps∼ 61 nC cm−2) upon applied voltage, the lower homologues showed thermochromic behaviour which can also be trapped via temperature quenching. [ABSTRACT FROM AUTHOR]

Thermotropic liquid crystals with π-conjugated cores are increasingly witnessed due to their promising optoelectronic and optophotonic properties. As π-conjugated mesogens are often realized by direct linking of the rings of the core, the mesophase transitions are usually modulated by inserting the required alkyl/alkoxy chains either at a terminal or lateral location. In this work, five mesogens in which thiophene and two phenyl rings are common in the core unit with terminal alkyl/alkoxy chains are investigated to probe the influence of (a) a terminal alkyl chain on the mesophase characteristics, (b) the linking units on the mesophase range and (c) the disparity of thiophene orientational constraints. The mesophase properties reveal that whenever the alkyl chain is located at one end of the molecule, polymesomorphism is observed. The XRD studies reveal layer ordering typical of smectic mesophases with lower temperature and higher order phases, namely SmB and CrE phases. A detailed 13C NMR study of the mesogens in the liquid crystalline phase indicates that the order parameters are governed by the nature of the substitution of thiophene and its linkage with two phenyl rings. Importantly, the 13C NMR data of the terminal chains in the liquid crystalline phase are compared with the recently reported thiophene mesogen in which the n-hexyl chain is located at the lateral position and completely different orientation characteristics were found for the terminal versus lateral chains. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different lateral substituents at different locations of dimers as well as the direction of ester linkages on the mesogenic properties, several new homologous series of dimeric compounds are synthesised. Here, two rod-like non-mesogenic laterally substituted azo moieties are connected to each other by an alkylene spacer through ester linkages. In all these dimers, the end alkoxy chain length is kept constant and the length of the spacer chain is varied. An odd–even effect of methylene groups in the spacer chain is observed in addition to a clear effect of lateral substituents at different positions and the direction of ester linkages on the mesomorphic properties. These dimers exhibit nematic and smectic mesophases. The X-ray diffraction studies revealed that the nematic phases are composed of skewed smectic nanoclusters (NcybC) irrespective of whether a smectic phase exists below the nematic phase or not. We did not observe any bent-core phases in these dimers. They are photo-switching both in solution and in their nematic mesophases. We observed that the photo-induced effect is more pronounced in the case of dimers with an odd-spacer when compared to those with an even-spacer. The gelation properties of these dimers are also investigated and a comparison of the liquid crystalline and gelation properties of these dimers has been made with reported similar but laterally unsubstituted dimers. [ABSTRACT FROM AUTHOR]

One new series of boron difluoride complexes 1 derived from heterocyclic benzoxazoles 2 was reported, and their mesomorphic and optical properties were also investigated. One single crystal of the mesogenic BF2 complex 1a (m = 12, n = 8) was obtained, and its single crystal and molecular structure were resolved. The geometry coordination at the central boron atom is tetrahedral. It crystallizes in a triclinic space group P1̅ with Z = 4. The overall molecular shape was described as slightly bent Z-shapes, and the molecular length was ca. 34.06 Å. Weak intramolecular and intermolecular H-bonds observed in the crystal lattice were attributed to the formation of mesophases. The results indicated that benzoxazoles 2a (n = 6, 8, 12) formed monotropic SmA phases, while boron difluoride complexes 1a (n = 6, 8, 12, 16) exhibited monotropic SmC mesophases. In contrast, all compounds of 2b and 1b (m = 1, n = 12 for all) were not mesogenic. Boron complexes 1 emitted a pronounced violet emission at λmax = 399 nm in solution at room temperature. [ABSTRACT FROM AUTHOR]

Two new regioisomeric star-shaped tris(N-salicylideneaniline)s are synthesized and characterized. The arms of these star-shaped mesogens differ from each other with respect to the substitution on the 3,5-positions of the central 1,2,4-oxadiazole moieties. The unsymmetrical nature of substitution leads to a change in the distribution of electron density, which will have an effect on the type of columnar self-assembly. One of these molecules stabilizes the columnar hexagonal phase, while the other one stabilizes the columnar rectangular phase. The columnar rectangular phase, which requires enhanced intermolecular interactions, is observed in the case of the star-shaped molecule, where the trialkoxy phenyl group is connected at the 5-position of the heterocycle, whereas the columnar hexagonal phase is observed in the case of the star-shaped molecule, where the trialkoxy phenyl group is connected at the 3-position of the heterocycle. These compounds showed reduced melting points, clearing points and an enhanced mesophase range with respect to their symmetric counterpart (1,3,4-oxadiazole derivative) reported earlier. All the molecules exhibited green light emission in solution, with good quantum yield. The emission of 1,2,4-oxadiazole derivatives was considerably red-shifted in comparison to those of 1,3,4-oxadiazole derivatives. This study emphasizes how a minor change in the molecular structure brings about a beneficial change in the self-assembly characteristics of star-shaped molecules. [ABSTRACT FROM AUTHOR]

A simple but novel class of hydrogen bonding liquid crystalline benzoic acids with alkylthio (or alkylsulfanyl; SR) groups was established. In general, although it is difficult for laterally non-substituted rod-like molecules with an alkylthio group to form some mesophases, the present molecules exclusively form a nematic (N) regime, owing to spontaneous carboxylic dimerization. It was found that the number of carbons in the alkylthio groups strongly correlated with transition temperatures as well as nematogenic stability: odd–even effects. Even-members displayed wider monotropic and enantiotropic N phases, despite the fact that almost all odd-members showed either none or only monotropic-narrower ones. Interestingly, their thermal transition temperatures were lower compared to those for alkoxy (OR) analogues, on account of the small angle (or large bend) of the C–S–C bond as well as the low electron density on their aromatic ring due to the weak electron donor properties of alkylthio groups. Additionally, in-depth wide-angle X-ray diffraction measurements revealed that an alkylthio analogue exhibited significantly enhanced smectic clusters formed in the N regime (or Ncyb phase) as well as the cluster type close to smectic (Sm) A, in comparison with an alkoxy analogue exhibiting a clear SmC-type cluster. The results indicate that a robust S…S intermolecular interaction for an alkylthio group into a mesogen affects the kind of smectic cluster in the Ncyb phase. [ABSTRACT FROM AUTHOR]

Hexaalkoxy-di(phenylethynyl)-tetraphenyl-carbo-benzenes bearing six CnH2n+1 aliphatic chains (n = 12, 18) have been synthesized and characterized, including by single crystal XRD analysis. For n = 12, a liquid crystal behaviour was observed in the range of 109–130 °C. DSC, POM and PXRD analyses evidenced a rectangular columnar mesophase at 115 °C. The determined 3D lattice constants are consistent with 2D STM images of the so-called “carbo-mesogen” deposited on an HOPG surface. [ABSTRACT FROM AUTHOR]

We report structurally new type of dimers composed of bent-core molecules connected through their central cores by an alkylene spacer. Various self-assembling structures are discovered when prolonging the terminal alkyl chains in arms. Among diverse mesophases, the antiferroelectric type of switching under an applied electric field is observed. [ABSTRACT FROM AUTHOR]

A number of new states of matter have been reported in recent years for liquid crystal dimers, most notably the twist-bend nematic phase which exhibits spontaneous breaking of symmetry through the emergence of chiral structures in an achiral fluid. In this communication we report on an unsymmetrical liquid crystal dimer that exhibits a transition from the spontaneously chiral twist-bend nematic phase into a novel smectic liquid crystal phase. [ABSTRACT FROM AUTHOR]

Several new square planar platinum(ii) complexes based on modified 2-phenylpyridine derivatives as the main ligand and picolinic acid as the auxiliary ligand were synthesized and their photophysical properties, and mechanochromic and liquid crystalline behavior were investigated. It is found that only the Pt–L1 complexes, in which one flexible long chain is attached to each end of 2-phenylpyridine, display monotropic smectic liquid crystalline behavior. Moreover, mechanochromism has been observed by grinding the solid complexes. It seems that the liquid crystalline and mechanochromic properties of these complexes are relative to the number of flexible alkoxy chains in the cyclometalated ligand. [ABSTRACT FROM AUTHOR]

Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic behaviour and fast photo-response of the liquid crystals based on phloroglucinol. The presented results prove the benefits of a modular methodology towards highly responsive materials with tailor-made properties. [ABSTRACT FROM AUTHOR]

We report the synthesis and mesophase characterization of a series of novel di- and tetra-aryl acenequinones. Diphenyl-acenequinones 1 and 2 exhibit monotropic mesophases while tetra-aryl acenequinones 4 and 5 exhibit stable columnar hexagonal mesophases. Compound 4 exhibits a more stable columnar mesophase than 5, consistent with a packing motif where molecules are stacked in perpendicular arrangement. [ABSTRACT FROM AUTHOR]

Sustainable plant-derived N-oleyl-1,3-diaminopropane surfactant micelles cross-linked by divinylbenzene (DVB) have been intercalated in the pores of mesostructured silica and the resulting functionalized mesophases were used to immobilize heavy metal ions through complexation by the diamine head groups. Two methods were used to form the composite surfactant–silica compositions. In the “pre-assembly” approach, the unsaturated amine micelles were first cross-linked in aqueous solution and subsequently used as a structure-directing agent to form the composite silica–polymeric amine mesophase. In the second “post-assembly” approach, the unsaturated amine micelles were used to template the silica mesophase and then cross-linked in situ with DVB within the pores of the composite mesophase. The accessibility of the amine functional groups in the mesophases prepared by both assembly methods was demonstrated through the uptake of Cu(ii) and Pb(ii) ions from aqueous solution. [ABSTRACT FROM AUTHOR]

The competition between crystallization and phase separation has always been a major concern for semi-crystalline block copolymers. In this work, in order to examine the mesophase evolution during crystallization in an olefin block copolymer (OBC), a “two-step isothermal crystallization” strategy was designed elaborately: the OBC samples were first isothermally crystallized at different temperatures (Tc) to create diverse crystallization histories; after melting, the second crystallization process was carried out to detect the degree of mesophase separation change during the first crystallization. It was quite interesting that the first crystallization at a lower Tc displayed little influence on the second crystallization process, while the first crystallization at a higher Tc could obviously accelerate the subsequent crystallization. In combination with the observation of the crystalline morphologies and phase morphologies in the melt, we speculated that hard blocks mainly crystallized separately during relatively rapid crystallization with a large quantity of nuclei; while crystallization-induced aggregation of hard blocks occurred during slow crystallization with a limited number of nuclei, changing the distribution of the hard blocks and accelerating the subsequent crystallization as a consequence. This work contributes to the understanding of the phase evolution during crystallization of OBC and such multi-block copolymers under different circumstances. [ABSTRACT FROM AUTHOR]

Oil-swollen hexagonal mesophases resulting from the surfactant mediated self-assembly of a quaternary mixture of water, surfactant, co-surfactant, and oil, are versatile templates to synthesize anisotropic nanomaterials. Poly(diphenylbutadyine) (PDPB) polymer nanofibrous network structures were produced in the oil tubes of the mesophases by photo-induced radical polymerization using a chemical initiator or by gamma irradiation. The diameter of the nanofibers can be varied from 5 to 25 nm in a controlled fashion, and is directly determined by the diameter of the oil tube of the doped mesophases, proving thus a direct templating effect of the mesophase. The nanoIR technique allows chemical characterization and identification of the polymer nanostructures simultaneously with morphological characterization. Cyclic voltammetry has been used as an effective approach to evaluate both the energy level of the highest occupied molecular orbital (HOMO) as well as the energy of the lowest unoccupied molecular orbital (LUMO) and the band gap of the PDPB. The conductivity of the PDPB nanostructures obtained by gamma irradiation was estimated to be 10−1 S cm−1, which is higher than the conductivity of PDPB nanostructures previously reported in the literature. The soft template approach allows size tunable synthesis of anisotropic polymer structures with morphological homogeneity at the nanoscale with high conductivity, thus it appears to be an attractive opportunity for electronic device applications. [ABSTRACT FROM AUTHOR]

The synthesis of the corrole-based liquid crystal phase CorLC is described together with its full characterization using a combination of Polarised Optical Microscopy (POM), ThermoGravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) measurements and Small-Angle X-Ray Diffraction (SA-XRD), which shows that CorLC has a hexagonal columnar organization at room temperature. The light absorption and hole-transport properties of the mesophase CorLC are compared with those featured by assemblies of its parent meso-triaryl (Cor1) and per-aryl (Cor2) derivatives. J-Aggregates are replaced by H-aggregates when the intermolecular distance is increased by a higher peripheral steric hindrance producing lower hole-transport mobilities. [ABSTRACT FROM AUTHOR]

A new series of photoluminescent Zn(ii)-salen type asymmetric Schiff base complexes, [ZnL], H2L = [N,N′-bis-(4-n-alkoxysalicylidene)-1,2-diaminopropane] (n = 12, 14 and 16) have been accessed and their mesomorphic and photophysical properties investigated. Though the ligands are non-mesomorphic, coordination to Zn2+ ion induces liquid crystalline behaviour. The complexes exhibited a lamello-columnar phase (Coll) as characterized by a variable temperature powder X-ray diffraction (XRD) study. Intense blue emissions were observed for the complexes at room temperature in solution, in the solid state and in the mesophase. Aggregation properties of the complexes were explored in different solvents through absorption and photoluminescence studies. While de-aggregation to monomers occurred in coordinating solvents due to axial coordination to Zn(ii), aggregates were formed in the solution of non-coordinating solvents. Density functional theory (DFT) computation carried out on a representative complex using a GAUSSIAN 09 program at the B3LYP level suggested a distorted square planar geometry. The results of a time-dependent DFT (TD-DFT) spectral correlative study showed the electronic properties of the complex molecule to be in compliance with the spectral data. [ABSTRACT FROM AUTHOR]

The splitting of signals in the NMR spectra originating from enantiotopic sites in prochiral molecules when dissolved in chiral solvents is referred to as spectral enantiotopic discrimination. This phenomenon is particularly noticeable in chiral liquid crystals (CLCs) due to the combined effect of the anisotropic magnetic interactions and the ordering of the solute in the mesophase. The enantiorecognition mechanisms are different for rigid and flexible solutes. For the former, discrimination results from symmetry breaking and is restricted to solutes whose point groups belong to one of the following four (“allowed”) symmetries, Cs, C2v, D2d and S4. The nature of the symmetry breaking for each one of these groups is discussed and experimental examples, using mainly 2H 1D/2D-NMR in chiral polypeptide lyotropic mesophases, are presented and analyzed. When flexible optically active solutes undergo fast racemization (on the NMR timescale) their spectrum corresponds to that of an average prochiral molecule and may exhibit enantiotopic sites. In CLCs, such sites will become discriminated, irrespective of their average (improper) symmetry. This enantiodiscrimination results mainly from the different ordering of the interchanging enantiomers. Several examples of such flexible molecules, including solutes with average axial and planar symmetries, are commented. Dynamic processes in solution that are not accompanied by the modulation of magnetic interactions remain “NMR blind”. This is sometimes the case for interconversion of enantiomers (racemization) or exchange of enantiotopic sites in isotropic solvents. The limitation can be lifted by using CLCs. In such solvents, non-equivalence between enantiomers or between enantiotopic sites is induced by the chiral environment, thus providing the necessary interactions to be modulated by the dynamic processes. Illustrative examples involving exchange of both, enantiotopic sites and enantiomers are examined. In this comprehensive review, various important aspects of enantiodiscrimination by NMR are presented. Thus the possibility to reveal enantiotopic recognition using residual dipolar couplings or to determine the absolute configuration of enantiotopic NMR signals is discussed. The various kinds of chiral mesophases able to reveal enantiotopic discrimination in guest prochiral molecules are also described and compared with each other. Finally to illustrate the high analytical potentialities of NMR in CLCs, several and various applications involving the enantiodiscrimination phenomenon are described. A strategy for assigning the NMR signals of meso compound in a meso–threo mixture of cyclic molecules is first discussed. This is followed by a description of advantages of the method for the determination of (D/H) natural isotopic fractionation in biocompounds. [ABSTRACT FROM AUTHOR]

The type of the mesophase is altered by a small change in the molecular architecture, i.e. increasing the number of alkyl chains attached to the mesogenic core at terminal positions. Lamellar (1D) and columnar (2D) phases are formed for molecules with one and three terminal chains, respectively. For those with two chains 3D phases are observed with either cubic or triclinic symmetry structure. [ABSTRACT FROM AUTHOR]

Herein, we report on the synthesis, characterization, liquid crystalline behavior and chirooptical properties of five (R)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates and their enantiomers, namely, (S)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates. These three-ring rod-like mesogens were prepared by acid catalyzed condensation of (R)-/(S)-4-(octan-2-yloxy)anilines with 4-formylphenyl 4-(n-alkoxy)benzoates. Thus, each pair of enantiomers comprises (R)-2-octyloxy and (S)-2-octyloxy chiral tails. In order to understand the structure–property correlations, the length of the paraffinic chain incorporated at the other end has been varied from n-octyloxy to n-dodecyloxy. A detailed study carried out by means of several complimentary techniques reveals the stabilization of liquid crystal phases that hold great promise in applied sciences especially in various device applications. In particular, the occurrence of mesophases such as the blue phase-I/II (BPI or BPII) and chiral nematic (N*) and chiral smectic C (SmC*) phases has been evidenced unequivocally with the help of polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electrical switching. Besides, the occurrence of an unknown, metastable smectic (SmX) phase below the SmC* phase has been noted. This study shows that the length of the terminal tail seems to determine the thermal range of the SmC* phase. The enantiotropic SmC* phase exhibiting ferroelectric switching behavior occurs over 60 °C thermal range; notably, the spontaneous polarization (Ps) value crosses over 100 nC cm−2. The photophysical properties and chirooptical behavior of the mesogens have been studied with the aid of UV-vis absorption and circular dichroism (CD) spectroscopic methods, respectively; the latter technique has been especially used to ascertain the twist sense of the N* and SmC* phases formed by a pair of enantiomers. The reversal of the helix-sense (from right to left and vice versa) during the N*–SmC* phase transition has been observed for the first time. [ABSTRACT FROM AUTHOR]

Three novel gallic-perylene-gallic trimers 7, 8 and 9 were synthesized by reacting gallic amino derivatives 3, 4 or 6 with perylene tetracarboxylic anhydride in yields of 75%, 78% and 80%, respectively. Compounds 7 and 8 with soft bridging chains exhibit columnar mesophase at room temperature, but compound 9 with a rigid bridging chain exhibits no mesophase. [ABSTRACT FROM AUTHOR]

Membrane proteins have been reconstituted on lipid bilayers with zero mean-curvature (cubic phases or vesicles). Here we show that reconstitution of pore-forming membrane proteins can also occur on highly curved lipidic bilayers of reverse hexagonal mesophases, for which the mean-curvature is significantly different from zero. We further show that the membrane protein provides unique topological interconnectivities between the aqueous nanochannels, significantly enhancing mesophase transport properties. [ABSTRACT FROM AUTHOR]

We describe a single step preparation of nanostructures of poly(3,4-ethylenedioxythiophene), PEDOT, in the hydrophobic domains of cationic surfactant-based hexagonal mesophases via chemical oxidative polymerization of EDOT monomers using FeCl3 as an oxidizing agent. After polymerization, the hexagonal structure of the mesophases is preserved as demonstrated by polarized light microscopy and X-ray scattering measurements. After extraction from mesophases, the chemical structure of PEDOT is confirmed by Fourier transform infrared spectroscopy. Moreover, PEDOT morphology is checked by transmission and scanning electron microscopies. PEDOT nanostructures with spindle-like or vesicle-like shapes are obtained depending on the experimental conditions. In the original method, high resolution atomic force microscopy, coupled with infrared nanospectroscopy, is used to probe the local chemical composition of PEDOT nanostructures. Finally, the as-prepared PEDOT polymers are characterized by both good thermal stability up to 200 °C and a relatively high conductivity value up to 0.4 S cm−1 as determined by thermogravimetric analysis and four probe measurements respectively. [ABSTRACT FROM AUTHOR]

Supramolecular metal complexes formed through hydrogen bonding between tris(3,4,5-decyloxy)stilbazole and several metallo–organic acids of the type [Au(R)(CNC6H4CO2H)] (R = C6F5, C6F4OC10H21), [cis-[MCl2(CNC6H4COOH)2] and [trans-[MI2(CNC6H4COOH)2] (M = Pd, Pt) have been synthesized. All the supramolecular palladium and platinum polycatenar aggregates display a hexagonal columnar mesophase at temperatures close to room temperature. Most of the supramolecular trisalkoxystilbazole complexes exhibit luminescent behaviour. Aggregates of [Au(C6F4OC10H21)(CNC6H4CO2H)] and [trans-[MI2(CNC6H4COOH)2] (M = Pd, Pt) form stable Langmuir films at the air–water interface. [ABSTRACT FROM AUTHOR]

Lipidic mesophases are a class of highly ordered soft materials that form when certain lipids are mixed with water. Understanding the relationship between the composition and the microstructure of mesophases is necessary for fundamental studies of self-assembly in amphiphilic systems and for applications, such as the crystallization of membrane proteins. However, the laborious formulation protocol for highly viscous mesophases and the large amounts of material required for sample formulation are significant obstacles in such studies. Here we report a microfluidic platform that facilitates investigations of the phase behavior of mesophases by reducing sample consumption 300-fold, and automating and parallelizing sample formulation. The mesophases were formulated on-chip using less than 80 nL of material per sample and their microstructure was analyzed in situ using small-angle X-ray scattering (SAXS). The 220 μm-thick X-ray compatible platform was comprised of thin polydimethylsiloxane (PDMS) layers sandwiched between cyclic olefin copolymer (COC) sheets. Uniform mesophases were prepared using an active on-chip mixing strategy coupled with periodic cooling of the sample to reduce viscosity. We validated the platform by preparing and analyzing mesophases of the lipid monoolein (MO) mixed with aqueous solutions of different concentrations of β-octylglucoside (βOG), a detergent frequently used in membrane protein crystallization. Four samples were prepared in parallel on chip, by first metering and automatically diluting βOG to obtain detergent solutions of different concentration, then metering MO, and finally mixing by actuation of pneumatic valves. Integration of detergent dilution and subsequent mixing significantly reduced the number of manual steps needed for sample preparation. Three different types of mesophases typical for MO were successfully identified in SAXS data from on-chip samples. Microstructural parameters of identical samples formulated in different chips showed excellent agreement. Phase behavior of samples on-chip (~80 nL per sample) corresponded well with that of samples prepared via the traditional coupled-syringe method using at least two orders of magnitude more material (“off-chip”, 35-40 μL per sample), further validating the applicability of the microfluidic platform for on-chip characterization of mesophase microstructure. [ABSTRACT FROM AUTHOR]

The poly(d-lactide)/poly(l-lactide) (PDLA/PLLA) blends with low molecular weights were cast from solution. After heating to above the melting temperature, followed by cooling at various rates, DSC, WAXD and FTIR studies revealed that a mesomorphic phase developed in the PDLA/PLLA 90/10 and 80/20 (or 10/90 and 20/80) specimens when the temperature window spanned from 80 °C to 110 °C. The mesophase melted and reorganized into crystallites after the temperature increased to ∼130 °C. Although the formation and transition of the mesophase was observed at lower temperatures in partially crystallized specimens, the mesophase could exist steadily when the temperature did not exceed 100 °C. The content of the mesophase was proven to be strongly dependent on the cooling rate, the d/l weight ratio and the molecular weights in the blends. The formation of the mesophase could be explained by the fact that the crystallization of the PLA matrix was disturbed by the addition of small amount of enantiomeric PLA. [ABSTRACT FROM AUTHOR]

The first bent-core liquid crystal materials with a photo-active azo linkage exhibiting the B7 mesophase are reported. The lower homologues of the bent-core compounds display the B1 phase and higher homologues show the B7 mesophase. The mesomorphic properties were characterized using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. The B7 phase of these materials establishes ferroelectric switching characteristics with anticlinic organization (SmCAPF) of the molecules in the layers. The bent-core molecules with an azo linkage are important for photoisomerization studies, which indicate trans to cis isomerization at 30 s, whereas the reverse processes take place over 40 s in chloroform. [ABSTRACT FROM AUTHOR]

Today the capability to rationally design and construct hybrid materials utilizing a performance-property driven methodology is strongly dependent on our ability to control the structure and the dynamics of hybrid interfaces. This control needs a deep knowledge of their molecular and supramolecular dynamics that must be evaluated in situ, in the soft matter or colloidal states. For this purpose the use of modern methodologies of characterization such as time resolved synchrotron experiments and advanced pulsed field gradient NMR methods (DOSY) is particularly relevant. In this critical review, two important examples are discussed. They concern, first, the study of surface capping organic components’ affinity towards nanoparticle surfaces by DOSY NMR. The knowledge and therefore the tuning of this affinity is paramount because it controls solubility, transferability and stability of colloidal dispersions of nanoparticles (NPs). In the second part, the mechanism of micellar templated formation of hybrid mesophases will be discussed in the frame of the main results obtained via in situSAXS (107 references). [ABSTRACT FROM AUTHOR]

Platinum(II) complexes of 1,3-bis(2-pyridyl)benzene containing two alkyl chains are unexpectedly mesomorphic and capable of changing absorption and emission colour depending on the phase obtained after thermal treatment. [ABSTRACT FROM AUTHOR]

A series of photoresponsive halogen-bonded liquid crystals (LCs) were successfully constructed using molecular halogen and azopyridine compounds, which show interesting properties of photoinduced phase transition upon UV irradiation. In addition, bromine-bonded LCs were first obtained with high mesophase stability. [ABSTRACT FROM AUTHOR]

The first bent-core molecules comprising 4-iodoresorcinol as the central core unit and incorporating azobenzene units have been synthesized. A new type of dark conglomerate phase (DC phase) is observed, which remains over a wide temperature range down to room temperature without crystallization. [ABSTRACT FROM AUTHOR]

Silver and gold nanoparticle superlattices with a layered structure were obtained via grafting of mesogenic molecules onto a metallic cluster surface. For the Ag superstructures unusual orientational order of the mesogenic ligands and anisotropy of the assembly afforded tunable plasmonic properties. [ABSTRACT FROM AUTHOR]

Complexes of molecular iodine with alkoxystilbazoles are liquid crystals with unusually high mesophase stability, predicated on an intermolecular I…I contact. Attempts to prepare analogous complexes with bromine led to an unexpected electrophilic substitution product. [ABSTRACT FROM AUTHOR]