Mesophase Structure Research Articles

Activation of Petroleum Pitch for Production of Porous Carbons with High Electric Double Layer Capacitance

Petroleum pitch can be an alternative of coal tar pitch as the precursor of activated carbon because of their lower contents of detrimental impurities and less pollution to the environment when compared with coal tar pitch. High-porosity carbon derived from activation of mesophase pitch with KOH has been successfully used as the electrode materials for electric double layer capacitors (EDLCs).1 Formation of mesophase structure through thermal treatment coordinates the pitch molecules and eventually reinforces the structure of porous carbons obtained from activation. The present study devises a temperature-programmed heating strategy to convert petroleum pitch to mesophase that has a framework advantageous for producing porous carbons suitable for EDLCs. The porous carbon is synthesized by KOH activation and has a Brunauer-Emmett-Teller surface area exceeding 3000 m2/g, When assembled in a symmetric two-electrode cell, the carbon delivers capacitance values of 170 and 102 F g-1 at current densities of 0.5 and 100 A g-1, respectively, in 1 M tetraethylammonium tetrafluoroborate/acetonitrile electrolyte. The energy density of the cell based on the total carbon mass reaches 23 Wh kg- 1 at a power density of 40 kW kg- 1. The results of the present study demonstrate the feasibility of using petroleum pitch as the precursor for porous carbon production and the significance of mesophase pitch structure for regulating the structure of pores suitable for charge storage.

Flying-seed-like mesogens 6: Synthesis and mesomorphism of phthalocyanine derivatives substituted by pentafluorosulfanylphenoxy group

We have synthesized two novel phthalocyanines, (m-SF[Formula: see text]PhO)[Formula: see text]PcCu (7b) and (p-SF[Formula: see text]PhO)[Formula: see text]PcCu (7c), in order to investigate their flying-seed-like mesomorphism. Their phase transition behavior and the mesophase structure have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Very interestingly, the derivative (m-SF[Formula: see text]PhO)[Formula: see text]PcCu (7b) substituted a SF5group at [Formula: see text]-position showed a Col[Formula: see text](P21/a) ([Formula: see text] p2gg) mesophase from rt to 315.0[Formula: see text]C, whereas the derivative (p-SF[Formula: see text]PhO)[Formula: see text]PcCu (7c) substituted a SF5group at [Formula: see text]-position showed a crystalline (K) phase from rt to the decomposition temperature at ca. 336[Formula: see text]C without showing mesomorphism. Thus, the novel phthalocyanine derivative (m-SF[Formula: see text]PhO)[Formula: see text]PcCu (7b) substituted a strong electron withdrawing SF5group at [Formula: see text]-position shows only one columnar mesophase in a very wide temperature region from rt to 315.0[Formula: see text]C. Furthermore, the Q-band wavelengths (672.2 and 672.1 nm) of the present (m-SF[Formula: see text]PhO)[Formula: see text]PcCu (7b) and (p-SF[Formula: see text]PhO)[Formula: see text]PcCu (7c) are shorter than that (680.3 nm) of the previous [(m-C[Formula: see text])PhO][Formula: see text]PcCu (5c) derivative. It can be attributed to strong electron withdrawing nature of the SF5group on the phenoxy group.

Mesophase Transformation of Mixed Liquid Crystals Formed by Supramolecular Self‐Organization of 4‐Substituted Benzoic Acids

AbstractA mixed liquid crystalline system consisting of 4‐(octadeca‐1,3‐diynyl)benzoic acid (14PhDA) and 4‐tetradecanoxybenzoic acid (14OBA) exhibits different mesophases depending on their composition and the temperature. A mechanism is investigated for the formation of mixed liquid crystalline phases and the transformation of smectic to discotic lamellar mesophases. The three kinds of mesophases, the discotic columnar phase of 14PhDA, the smectic C phase of 14OBA, and the discotic lamellar phase of a mixture of 14PhDA and 14OBA, are simultaneously observed in a temperature range from 110 to 140 oC during the process of formation of the mixed liquid crystals by the molecular diffusion of 14PhDA and 14OBA. After rapid cooling the sample to room temperature, microscopic IR spectra are measured to estimate the composition ratio of 14PhDA and 14OBA at local positions in each mesophase. The composition ratio discontinuously changes at the boundary between the 14OBA and 14PhDA/14OBA phases due to a significant difference in the mesophase structures, i. e., the calamitic and the discotic phases, while the 14PhDA content continuously increases at another boundary between the 14PhDA/14OBA and 14PhDA mesophases. It is concluded that the diffusion of 14OBA dimer from the smectic phase to the discotic lamella phase is fast in contrast to the slow diffusion of disc‐like mesogens included in the discotic mesophases.

Self-Assembly Directed Organization of Nanodiamond During Ionic Liquid Crystalline Polymer Formation.

The UV-initiated free radical polymerization of a lyotropic mesophase prepared by co-assembly of an aqueous mixture of an ionic liquid (IL) monomer, 3-decyl-1-vinylimidazolium chloride, in a dimethyl sulfoxide dispersion of an IL-monomer nanodiamond conjugate yields a well-ordered 2D hexagonally structured network-polymer composite. The IL monomer is covalently bound to carboxylated detonation diamond via ester-linked 3-decyl-1-vinylimidazolium bromide. Successful preparation of the amphiphile-functionalized nanodiamond is determined by ATR/FT-IR, thermogravimetric analysis, and small-angle X-ray scattering (SAXS). Mesophase and composite structure are evaluated by SAXS, revealing a columnar architecture composed of amphiphilic ionic liquid cylinders containing solvent-rich cores. Self-assembly directed site localization of the nanodiamond positions the particles in the alkyl chain continuum upon polymerization. The composite reversibly swells in ethanol allowing structural variation and modulation of the nanoparticle internal packing arrangement. This work demonstrates that through careful molecular design, self-organization and site-directed assembly of nanodiamond into chemically distinct regions of a nanostructured organogel can be achieved.

Synthesis and mesomorphism of new aliphatic polycarbonates containing side cholesteryl groups

ABSTRACTNew cholesterol side-functionalised polycarbonate polymers were synthesised by the ring-opening homo- and copolymerisation reaction of the cyclic monomer cholesteryl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate and d,l-lactide using Sn(Oct)2 as a catalyst. The chemical structures and average molecular weights of the cyclic monomer, homopolymer and block copolymers obtained in this study were characterised using FT-IR, 1H NMR and gel permeation chromatographic measurement. The mesomorphism and mesophase structure were investigated with polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurement. As a result, the homopolymer and block copolymers showed an enantiotropic smectic A (SmA) phase. With the concentration of the lactide segment increasing, the glass transition temperature and isotropic temperature of the corresponding block copolymer all decreased. In addition, XRD suggested that the homopolymer and two block copolymers showed the SmA double-layer packing of side chains.

High-Throughput Screening of Saturated Fatty Acid Influence on Nanostructure of Lyotropic Liquid Crystalline Lipid Nanoparticles.

Self-assembled lyotropic liquid crystalline lipid nanoparticles have been developed for a wide range of biomedical applications with an emerging focus for use as delivery vehicles for drugs, genes, and in vivo imaging agents. In this study, we report the generation of lipid nanoparticle libraries with information regarding mesophase and lattice parameter, which can aid the selection of formulation for a particular end-use application. In this study we elucidate the phase composition parameters that influence the internal structure of lipid nanoparticles produced from monoolein, monopalmitolein and phytantriol incorporating a variety of saturated fatty acids (FA) with different chain lengths at varying concentrations and temperatures. The material libraries were established using high throughput formulation and screening techniques, including synchrotron small-angle X-ray scattering. The results demonstrate the rich polymorphism of lipid nanoparticles with nonlamellar mesophases in the presence of saturated FAs. The inclusion of saturated FAs within the lipid nanoparticles promotes a gradual phase transition at all temperatures studied toward structures with higher negative surface curvatures (e.g., from inverse bicontinuous cubic phase to hexagonal phase and then emulsified microemulsion). The three partial phase diagrams produced are discussed in terms of the influence of FA chain length and concentration on nanoparticle internal mesophase structure and lattice parameters. The study also highlights a compositionally dependent coexistence of multiple mesophases, which may indicate the presence of multicompartment nanoparticles containing cubic/cubic and cubic/hexagonal mesophases.

Multiscale Model for the Templated Synthesis of Mesoporous Silica: The Essential Role of Silica Oligomers

A detailed theoretical understanding of the synthesis mechanism of periodic mesoporous silica has not yet been achieved. We present results of a multiscale simulation strategy that, for the first time, describes the molecular-level processes behind the formation of silica/surfactant mesophases in the synthesis of templated MCM-41 materials. The parameters of a new coarse-grained explicit-solvent model for the synthesis solution are calibrated with reference to a detailed atomistic model, which itself is based on quantum mechanical calculations. This approach allows us to reach the necessary time and length scales to explicitly simulate the spontaneous formation of mesophase structures while maintaining a level of realism that allows for direct comparison with experimental systems. Our model shows that silica oligomers are a necessary component in the formation of hexagonal liquid crystals from low-concentration surfactant solutions. Because they are multiply charged, silica oligomers are able to bridge ad...

Unified Understanding of Ferroelectricity in n-Nylons: Is the Polar Crystalline Structure a Prerequisite?

Over the past decades, it has been commonly considered that ferroelectricity is closely related to the polar crystalline structure of odd-numbered nylons, and even-numbered nylons should not exhibit ferroelectricity due to their nonpolar crystalline structures. In this work, we ask a fundamental question: Are odd-numbered nylons with polar crystalline structures prerequisites for ferroelectricity? Here, ferroelectric properties are reported for mesomorphic even-numbered nylons (nylons-12 and -6) quickly quenched from the melt, using electric displacement–electric field (D–E) hysteresis loop measurements. From X-ray diffraction and infrared studies, the structure of the mesophases in the quenched samples was considered to contain multiple twists in the chain conformation, resulting in enlarged interchain distance and dangling/weak hydrogen bonds. Upon high field electric poling, the mesophase structure enables dipolar switching of the dangling/weak hydrogen bonds, forming electric-field-induced ferroelectr...

Lyotropic Liquid Crystalline Cubic Phases as Versatile Host Matrices for Membrane-Bound Enzymes.

Lyotropic liquid crystalline cubic mesophases can function as host matrices for enzymes because of their biomimetic structural characteristics, optical transparency, and capability to coexist with water. This study demonstrates that the in meso immobilized membrane-bound enzyme d-fructose dehydrogenase (FDH) preserves its full activity, follows ideal Michaelis-Menten kinetics, and shows improved stability compared to its behavior in solution. Even after 5 days, the immobilized FDH retained its full activity in meso, whereas a model hydrophilic enzyme, horseradish peroxidase, maintained only 21% of its original activity. We reason that the lipidic bilayers in the three-dimensional structures of cubic mesophases provide an ideal environment for the reconstitution of a membrane-bound enzyme. The preserved activity, long-term stability, and reusability demonstrate that these hybrid nanomaterials are ideal matrices for biosensing and biocatalytic fuel cell applications.

Nonreversible Enhanced Crystallization of Olefin Block Copolymer Induced by Preshearing

In this work, the influence of preshearing on crystallization of olefin block copolymer (OBC) was systematically investigated. It was found that upon an interval of melt preshear the crystallization rate of OBC was prominently elevated which was evidenced by both nonisothermal and isothermal crystallization results. The lamellar thickness of OBC increased and the size of spherulites decreased after shear. Interestingly, annealing and multiple heating and cooling experiments demonstrated that the enhancement effect on crystallization was nonreversible. The morphology observations suggested that preshearing caused an alteration in mesophase structure of OBC. On the basis of our results, we speculated that the increase in the amount of hard blocks that dissolved in the soft-block-rich matrix induced by shear promoted the unique “pass-through” crystallization process of OBC, which should be responsible for the largely enhanced crystallization of sheared OBC.

Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition.

We present structural studies of a dimeric compound composed of a central heptyl spacer linking two mesogens consisting of terphenyl units at which two adjacent fluoro groups are attached to each central ring. The terminal rings are linked to pentyl chains as terminal groups. The material exhibits a nematic-nematic transition and a low temperature modulated phase. The higher temperature nematic phase was found to exhibit an anomaly of the bend elastic constant similar to that of the dimers with N-Ntb phase sequence, and the physical properties of the low-temperature nematic phase are similar to those of the known Ntb materials. The structure of the low-temperature modulated smectic/columnar phase is described together with its ability to form freely suspended films and fibres. The relation of the modulated structure to the fibre formation and to the appearance of the labyrinthine instability in freely-suspended films is discussed.

Highly luminescent and stable lyotropic liquid crystals based on a europium β-diketonate complex bridged by an ethylammonium cation.

Soft lanthanide luminescent materials are impressive because of their tunable and self-assembling characteristics, which make them an attractive emerging materials field of research. In this report, novel luminescent lyotropic liquid crystals (LLCs) with four different mesophases have been fabricated by a protic ionic liquid (IL) based europium β-diketonate complex EA[Eu(TTA)4] (EA = ethylammonium, TTA = 2-thenoyltrifluoro-acetone) and an amphiphilic block copolymer (Pluronic P123). The protic IL, ethylammonium nitrate (EAN), was used as both the solvent and linkage to stabilize the doped complexes. Analyses by single-crystal X-ray diffraction for EA[Eu(TTA)4] and Fourier transform infrared spectroscopy for the LLC materials reveal convincingly that the ethylammonium cations establish an effective connection with both the carbonyl group of the β-diketonate ligand and the EO blocks of the amphiphilic block copolymer P123 via strong hydrogen bonding interactions. Due to this, an extremely long decay time of the excited state is obtained in EA[Eu(TTA)4] and excellent photostability of the luminescent LLCs could be achieved. The long-period ordered structures of the luminescent LLCs have been investigated by small-angle X-ray scattering measurements and the best luminescence performance was found in the most organized mesophase. Noteworthy, the LLCs could yield an effective confining effect on the europium complex accompanied by a sizeable elongation of the excited-state lifetime and an enhancement of the energy transfer efficiency, which reaches a remarkably high value of 52.6%. More importantly, the modulated luminescence properties observed in the four mesophase structures offer the potential and powerful possibility for these unique composite LLCs to be used in the fabrication of soft luminescent materials with tunable functions.

Инкапсулирование глобулярных молекул в структуру ламеллярных лантан-содержащих мезофаз

Инкапсулирование глобулярных молекул в структуру ламеллярных лантан-содержащих мезофаз

Unit cell structure of water-filled monoolein in inverted hexagonal mesophase in the presence of incorporated tricaprylin and entrapped lysozyme.

Molecular dynamics (MD) was employed by means of a specific simulation protocol to investigate the equilibrium structure at 25 °C of the hexagonal inverted (HII) mesophase composed from water, 1-monoolein (GMO), and tricaprylin, with or without entrapped lysozyme. Based on robust and fast MD simulations, the study provides a comprehensive analysis and visualization of the local structure of HII mesophase containing admixtures. The most important physical insight is the possibility to observe the strong self-recovery capacity of the GMO layer, which allows the HII mesophase tubes to reorganize and host lysozyme molecules with a size bigger than the diameter of the water channel. This is a direct message to the experimenters that the HII mesophase has the potential to host molecules larger than the diameter of the water channel. Collective character of the interlipid interactions is outlined, which is not affected by the presence of the cargo and may be the reason for the efficient GMO reorganization. Another important result is the possible explanation of the role of triacylglycerols on the low-temperature stabilization of the HII mesophase. The analysis shows that despite the low amount of tricaprylin, its molecules prevent the extreme inclination of the lipid tails and thus optimize the alignment capacity of the lipid tails layer. The study also reveals that the packing frustration does not depend on the temperature and the presence of admixtures. Hence, it might be numerically defined as a universal invariant parameter of a stable HII mesophase composed of a certain lipid.

Fast acquisition of multidimensional NMR spectra of solids and mesophases using alternative sampling methods

Unique information about the atom-level structure and dynamics of solids and mesophases can be obtained by the use of multidimensional nuclear magnetic resonance (NMR) experiments. Nevertheless, the acquisition of these experiments often requires long acquisition times. We review here alternative sampling methods, which have been proposed to circumvent this issue in the case of solids and mesophases. Compared to the spectra of solutions, those of solids and mesophases present some specificities because they usually display lower signal-to-noise ratios, non-Lorentzian line shapes, lower spectral resolutions and wider spectral widths. We highlight herein the advantages and limitations of these alternative sampling methods. A first route to accelerate the acquisition time of multidimensional NMR spectra consists in the use of sparse sampling schemes, such as truncated, radial or random sampling ones. These sparsely sampled datasets are generally processed by reconstruction methods differing from the Discrete Fourier Transform (DFT). A host of non-DFT methods have been applied for solids and mesophases, including the G-matrix Fourier transform, the linear least-square procedures, the covariance transform, the maximum entropy and the compressed sensing. A second class of alternative sampling consists in departing from the Jeener paradigm for multidimensional NMR experiments. These non-Jeener methods include Hadamard spectroscopy as well as spatial or orientational encoding of the evolution frequencies. The increasing number of high field NMR magnets and the development of techniques to enhance NMR sensitivity will contribute to widen the use of these alternative sampling methods for the study of solids and mesophases in the coming years.

Aperiodic “Bricks and Mortar” Mesophase: a New Equilibrium State of Soft Matter and Application as a Stiff Thermoplastic Elastomer

A new thermodynamically stable, aperiodic “bricks-and-mortar” (B&M) cellular mesophase structure is reported in PS1-b-(PI-b-PS2)3 miktoarm copolymer and PS homopolymer blends [PS1, long polystyrene; PI, poly(isoprene); PS2, short polystyrene], where PS comprises discrete hard “bricks” and PI the continuous soft “mortar”. The mesophase is unique in its extreme domain volume fractions, its lack of positional order, and quasi-long-range orientational order. On the basis of this unusual mesophase structure, a series of PS-based thermoplastic elastomers are realized, combining rigidity from an exceptionally high content of discrete glassy PS domains (up to 82 wt %) and high extensibility with recoverable elasticity from a low content of continuous rubbery PI (down to 18 wt %). The new elastomers show sharp yielding behavior while maintaining good elasticity at large strains. Tensile-SAXS experiments reveal that voiding plays an important role for the mechanical behavior and voids can open/close reversibly with/without loading. Plastic deformation only results in a slight loss of recoverable elasticity.

Cold Crystallization of PDMS and PLLA in Poly(l-lactide-b-dimethylsiloxane-b-l-lactide) Triblock Copolymer and Their Effect on Nanostructure Morphology

Poly(l-lactide-b-dimethylsiloxane-b-l-lactide) (PLLA-b-PDMS-b-PLLA) triblock copolymer was synthesized by ring-opening polymerization of l-lactide using bis(hydroxyalkyl)-terminated PDMS as a macroinitiator. The block copolymer was immiscible in the melt, and the melt morphology was preserved upon cooling the melt to −120 °C. It was also observed that at moderate cooling rates PDMS and PLLA blocks remain in the amorphous phase at temperatures below −120 °C. The breakout and preservation of the nanostructure morphology of the triblock copolymer have been investigated by variable temperature small-angle and wide-angle X-ray scattering (SAXS and WAXS) during heating. The crystallization and melting of PDMS block occurred within the confined space entrenched by the amorphous PLLA block in the temperature range from −120 to 40 °C by preserving the microphase-separated morphology. At around the glass transition temperature of PLLA (∼45 °C), chain stretching of PLLA and PDMS took place, resulting in the sudden increase of the lamellar long period. In this temperature region, amorphous PLLA transiently transformed to the mesophase structure that resulted in the increase of PLLA domain thickness. At higher temperature, the morphological perturbation was induced by the breakout crystallization of PLLA block. In addition, the effect of isothermal cold crystallization temperatures on the polymorphic behavior of PLLA in PLLA-b-PDMS-b-PLLA triblock copolymers was also investigated. It was found that the polymorphic behavior of PLLA was not influenced much by the presence of PDMS blocks. The disordered (α′) and ordered (α) forms are formed at low and high cold crystallization temperatures, respectively, similar to the PLLA homopolymer.

Flying-seed-like liquid crystals 5: Liquid crystals based on octakisphenylthiophthalocyanine and their optical properties

We have synthesized three novel flying-seed-like liquid crystals based on phthalocyaninato copper(II) (abbreviated as PcCu ) substituted by bulky groups {(o- C1) PhS (i), (m- C1) PhS (j), [m, p-( C1)2] PhS (k)} instead of using long alkyl chains, in order to investigate their mesomorphism. Their phase transition behavior and the mesophase structures have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. As the results, [(o-C1)PhS]8PcCu (8i), [(m-C1)PhS]8PcCu (8j) and {[m,p-(C1)2]PhS}8PcCu (8k) show a Coltet.omesophase at 314.9~362.9 °C, a Colro(P2m) mesophase at 287.4~334.2°C and a Colro(P2m) mesophase at 331.8~386.8°C, respectively. Very interestingly, each of the derivatives thus exhibits a columnar mesophase at very high temperatures. The mesomorphism is apparently originated from the novel bulky groups (i~k). It is also noteworthy that the Q-bands of the present PhS-containing Pc derivatives 8i~8k in THF significantly red-shift by about 35 nm in comparison with those of the corresponding PhO-containing derivatives in THF.

Phase behavior of a family of truncated hard cubes.

In continuation of our work in Gantapara et al., [Phys. Rev. Lett. 111, 015501 (2013)], we investigate here the thermodynamic phase behavior of a family of truncated hard cubes, for which the shape evolves smoothly from a cube via a cuboctahedron to an octahedron. We used Monte Carlo simulations and free-energy calculations to establish the full phase diagram. This phase diagram exhibits a remarkable richness in crystal and mesophase structures, depending sensitively on the precise particle shape. In addition, we examined in detail the nature of the plastic crystal (rotator) phases that appear for intermediate densities and levels of truncation. Our results allow us to probe the relation between phase behavior and building-block shape and to further the understanding of rotator phases. Furthermore, the phase diagram presented here should prove instrumental for guiding future experimental studies on similarly shaped nanoparticles and the creation of new materials.

Self-assembly of thiolated graphene oxide onto a gold surface and in the supramolecular order of discotic liquid crystals

Covalent functionalization of graphene oxide sheets with thiol produces thiolated graphene oxide which self assembles on gold surfaces and in the supramolecular structure of a discotic mesophase which have potential applications in optoelectronics.