Crystal Mixture Research Articles

Structural Comparisons, Fluorescence Properties, and Glass-to-Crystal Transformations of Heat-Cooled and Melt-Quenched Zeolitic Imidazolate Framework Glass.

As a representative of zeolitic imidazolate framework glass, agZIF-62 has been reported to be synthesized using a melt-quenching method in which the ZIF-62 crystal is heated to a temperature above the melting point. Interestingly, we unexpectedly found that agZIF-62 can also be synthesized by simple heating at temperatures lower than the melting point, which may be assisted by the release of encapsulated solvent molecules. The structural differences between melt-quenched agZIF-62 (MQ-agZIF-62) and heat-cooled agZIF-62 (HC-agZIF-62) were investigated. The results indicated that MQ-agZIF-62 is closer to the liquid state, while HC-agZIF-62 is closer to the crystal state. Interestingly, their luminescent emissions exhibit significant differences. Compared with the ZIF-62 crystal, MQ-agZIF-62 showed a blue-shift of 14 nm, whereas HC-agZIF-62 showed a red-shift of 9 nm. The emission intensity of agZIF-62 is also significantly stronger than that of ZIF-62; thus, rapid semiquantitative detection of the content of the MOF glass in glass and crystal mixtures can be achieved. In addition, HC-agZIF-62 and MQ-agZIF-62 can transform into ZIF-62 crystals via a solvent-media mechanism. This study provides new insights into ZIF-62 glass.

1-(Pyridin-4-yl)-4-thiopyridine (PTP) in the crystalline state - pure PTP and a cocrystal and salt.

The first in situ preparation and single-crystal structure identification of pure 1-(pyridin-4-yl)-4-thiopyridine (PTP), C10H8N2S, a simple and basic derivative of mercaptopyridine, from a crystallization mixture is described. The same PTP was found in two multicomponent crystal forms with 3,5-dinitrobenzoic acid as a classic two-component cocrystal, namely, 1-(pyridin-4-yl)-4-thiopyridine-3,5-dinitrobenzoic acid (1/1), C7H4N2O6·C10H8N2S, and with 2-hydroxy-3,5-dinitrobenzoic acid as a salt formed via proton transfer from the hydroxy group of the acid to the pyridyl N atom of PTP, namely, 4-(4-sulfanylidene-1,4-dihydropyridin-1-yl)pyridin-1-ium 1-carboxy-3,5-dinitrophenolate, C10H9N2S+·C7H3N2O7-. The protonation energy of PTP is 944.64 kJ mol-1, indicating slightly greater N-basicity compared to pyridine, a well characterized and very basic chemical reference. A variety of molecular interactions can be observed in the three new crystal structures of PTP, which are all discussed in detail. Our findings confirm those of previous studies, indicating that PTP and 4-mercaptopyridine may, under suitable conditions, be chemically converted to one another, and that this process can be stimulated by light (UV-Vis).

Beef tallow/lard blends in O/W emulsions: Characterization of fat crystals, partial coalescence, rheology, and aeration performance

This study aimed to find new strategies for enhancing the stability and texture properties of aerated emulsion by combining different animal fats with different ratios. Beef tallow (BT)/ lard (LA) were mixed at different ratios to prepare oil-in-water (O/W) emulsions, with and without aeration. The compatibility, crystallization behavior, stability, and rheology in both O/W and aerated emulsion systems prepared with BT/LA binary blends were further investigated. Larger and inhomogeneous β′ and β crystal mixtures appeared as the BT ratio increased. Monotectic or eutectic interaction was displayed according to different BT/LA ratios, solid fat content (SFC) and temperatures. O/W emulsion prepared with BT/LA binary showed higher apparent viscosity with larger fat globules distributed as the BT ratio increased. BT had higher SFC at any given temperature and the fat globule aggregation extent was higher. Partial coalescence occurred as the LA ratio increased when SFC < 35 %. Higher foam firmness of the aerated emulsion was achieved by BT/LA binary with higher BT ratios. As a result, combining BT and LA with different ratios achieved higher emulsion stability and foam properties. This study provides a novel insight into the application of different animal fats and the improvement of high-quality whippable products.

New native Bacillus thuringiensis strains induce high insecticidal action against Culex pipiens pallens larvae and adults

Mosquitoes of many species are key disease vectors, killing millions of people each year. Bacillus thuringiensis-based insecticide formulations are largely recognized as among the most effective, ecologically safe, and long-lasting methods of managing insect pests. New B. thuringiensis strains with high mosquito control effectiveness were isolated, identified, genetically defined, and physiologically characterized. Eight B. thuringiensis strains were identified and shown to carry endotoxin-producing genes. Using a scanning electron microscope, results revealed typical crystal forms of various shapes in B. thuringiensis strains. Fourteen cry and cyt genes were found in the strains examined. Although the genome of the B. thuringiensis A4 strain had twelve cry and cyt genes, not all of them were expressed, and only a few protein profiles were observed. The larvicidal activity of the eight B. thuringiensis strains was found to be positive (LC50: 1.4–28.5 g/ml and LC95: 15.3-130.3 g/ml). Bioassays in a laboratory environment demonstrated that preparations containing B. thuringiensis spores and crystals were particularly active to mosquito larvae and adults. These new findings show that the novel preparation containing B. thuringiensis A4 spores and crystals mixture might be used to control larval and adult mosquitoes in a sustainable and ecologically friendly manner.

The Electroless Monolayer and Duplex Ni–B and Ni–P Coatings for 316L Stainless Steel in Synergistic Combination of Mechanical (Wear) and Chemical (Corrosion) Processes

Conventional processes are performed to improve the low hardness and low wear resistance properties of 316L steel, but these processes generally decrease the corrosion resistance. Electroless nickel alloy coatings provide a hard, wear‐resistant, and corrosion‐resistant surface. Thus, the present study aims to investigate the wear, corrosion, and tribocorrosion behaviors of monolayer and duplex coatings with nickel–boron (Ni–B) and nickel–phospore (Ni–P) on 316L steel in comparison with 316L steel in dry sliding and 0.9 wt% NaCl solution environments. It is determined that the coatings have a mixture of crystal and amorphous structures, the interfaces on the 316L are uniform, and the compatibility between the layers is good. The Ni–B, Ni–P/Ni–B, and Ni–B/Ni–P coatings are 2.3, 2.06, and 1.6 times as hard as the 316L, respectively. The wear rates of Ni–B, Ni–P/Ni–B, and Ni–B/Ni–P coatings show decrease by 99.3%, 92.5%, and 99.1% in the dry‐sliding condition and by 98.5%, 30.1%, and 19.1% in the tribocorrosion condition compared with that of 316L, respectively. It is observed that the monolayer Ni–B coating exhibits superior hardness, a higher contact angle, low electrical conductivity, and better tribological performance in both dry sliding and tribocorrosion conditions compared to the 316L and duplex coatings.

New Class of Polymer Materials-Quasi-Nematic Colloidal Particle Self-Assemblies: The Case of Assemblies of Prolate Spheroidal Poly(Styrene/Polyglycidol) Particles.

Assemblies of colloidal polymer particles find various applications in many advanced technologies. However, for every type of application, assemblies with properly tailored properties are needed. Until now, attention has been concentrated on the assemblies composed of spherical particles arranged into so-called perfect colloidal crystals and on complex materials containing mixtures of crystal and disordered phases. However, new opportunities are opened by using assemblies of spheroidal particles. In such assemblies, the particles, in addition to the three positional have three angular degrees of freedom. Here, the preparation of 3D assemblies of reference microspheres and prolate spheroidal poly(styrene/polyglycidol) microparticles by deposition from water and water/ethanol media on silicon substrates is reported. The particles have the same polystyrene/polyglycidol composition and the same volumes but differ with respect to their aspect ratio (AR) ranged from 1 to 8.5. SEM microphotographs reveal that particles in the assembly top layers are arranged into the quasi-nematic structures and that the quality of their orientation in the same direction increase with increasing AR. Nano- and microindentation studies demonstrate that interactions of sharp and flat tips with arrays of spheroidal particles lead to different types of particle deformations.

Effect of the nature of the liquid crystal on the phase separation kinetic behaviour in polymer/liquid crystal mixtures

Effect of the nature of the liquid crystal on the phase separation kinetic behaviour in polymer/liquid crystal mixtures

Deciphering Cryptic Multi-Stage Crystal-Melt Separation during Construction of the Tonglu Volcanic–Plutonic Complex, SE China

Abstract Revealing the origin of explosive eruptions of silica-rich magma is of paramount importance for understanding the evolution of continental crust and volcanic hazards. However, it remains controversial as to how the erupted magmas form and how they connect with plutonic realms, partly owing to the rarity and the obscurity of the ‘cumulate’ complementary to such eruptions of silica-rich magmas. Here the issues are explored by comparing the volcanic rocks (rhyodacite + rhyolite) and their associated subvolcanic intrusions (monzodiorite + monzonite + quartz monzonite) within Tonglu volcanic basin (SE, China). The Tonglu plutonic and volcanic units are consistent with each other in age (~130 Ma), space and source materials (e.g. Sr-Nd-Hf isotopes), strongly suggesting that they are cogenetic. Mineral mapping demonstrates that abundant plagioclase clusters (and chains in monzodiorite) occur in plutonic units, implying the processes of crystal gathering and/or accumulation. Rhyolite-MELTS modeling, and geochemical studies coupled with textural observations suggest that the Tonglu volcanic and plutonic rocks represent the residual melts and the complementary cumulate residues, respectively. The compositional and mineral variations in the plutonic rocks can be explained by two-stage, low-pressure crystal-melt separation of a dacitic magma. The monzodiorite represents the first-stage cumulate that was unsaturated in zircon and biotite/K-feldspar on the basis of low Zr and Ba concentrations and the occurrence of these two phases in the interstices between plagioclase and amphibole. The monzonite and quartz monzonite are the second-stage cumulates after saturation of zircon and biotite/K-feldspar as indicated by abrupt increases in Zr and Ba concentrations and zircon inclusions within euhedral biotite. Mass balance calculation and textural estimation indicate that the cumulates actually are a mixture of crystals and melt, containing ~40 vol% interstitial melt. Interstitial zircons from monzodiorite, largely crystallized from trapped melt, show contrasting trace-element trends (e.g. Ti, Zr/Hf, Eu/Eu*, Gd/Yb) to those of the other rock types (i.e. monzonite, quartz monzonite, rhyodacite and rhyolite), consistent with fractional crystallization (FC). We interpret these divergences to heating-induced partial dissolution of a basal crystal framework of monzodiorite due to recharges of hot mafic magmas, but the limited dissolution fails to rejuvenate the crystal mush. The Tonglu volcanic–plutonic system demonstrates that compositional distillation via crystal–liquid separation within the upper crust is an effective mechanism by which a potentially eruptible rhyolitic cap can be generated. Recharges of hot mafic magmas at shallow crustal levels may prolong the lifespan of granitic magma reservoirs. A combined study including texture, geochemistry, thermodynamic modeling and mass-balance calculations can help us identify the fingerprints of cumulates in felsic magma systems and thus track the processes responsible for producing large eruptions of silica-rich magmas.

Mesomorphic behaviors of some acrylate liquid crystals and their application for polarizer preparation

ABSTRACT Two series of acrylate liquid crystals with enantiotropic SmA and SmC phases were synthesised. With increasing the alkoxy chain length, SmC phase was favourable to be formed. The mesophases were confirmed by taking small angle X-ray scattering patterns. Moreover, a diacrylate liquid crystal with an enantiotropic SmA phase was synthesised. Smectic liquid crystal mixtures were prepared using the diacrylate liquid crystal (or a mixture of an acrylate liquid crystal and the diacrylate one) and a dichroic dye. After photopolymerisation at the SmA phase, polymeric polarisers were obtained. The degree of polarisation was increased with increasing the dye concentration and film thickness.

Speciation of Transition-Metal-Substituted Keggin-Type Silicotungstates Affected by the Co-crystallization Conditions with Proteinase K.

We report on the synthesis of the tetrasubstituted sandwich-type Keggin silicotungstates as the pure Na salts Na14[(A-α-SiW10O37)2{Co4(OH)2(H2O)2}]·37H2O (Na{SiW10Co2}2) and Na14[(A-α-SiW10O37)2{Ni4(OH)2(H2O)2}]·77.5H2O (Na{SiW10Ni2}2), which were prepared by applying a new synthesis protocol and characterized thoroughly in the solid state by single-crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Proteinase K was applied as a model protein and the polyoxotungstate (POT)–protein interactions of Na{SiW10Co2}2 and Na{SiW10Ni2}2 were studied side by side with the literature-known K5Na3[A-α-SiW9O34(OH)3{Co4(OAc)3}]·28.5H2O ({SiW9Co4}) featuring the same number of transition metals. Testing the solution behavior of applied POTs under the crystallization conditions (sodium acetate buffer, pH 5.5) by time-dependent UV/vis spectroscopy and electrospray ionization mass spectrometry speciation studies revealed an initial dissociation of the sandwich POTs to the disubstituted Keggin anions HxNa5–x[SiW10Co2O38]3– and HxNa5–x[SiW10Ni2O38]3– ({SiW10M2}, M = CoII and NiII) followed by partial rearrangement to the monosubstituted compounds (α-{SiW11Co} and α-{SiW11Ni}) after 1 week of aging. The protein crystal structure analysis revealed monosubstituted α-Keggin POTs in two conserved binding positions for all three investigated compounds, with one of these positions featuring a covalent attachment of the POT anion to an aspartate carboxylate. Despite the presence of both mono- and disubstituted anions in a crystallization mixture, proteinase K selectively binds to monosubstituted anions because of their preferred charge density for POT–protein interaction.

Self-Assembly of an Equimolar Mixture of Liquid Crystals and Magnetic Nanoparticles

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found that the LCs show isotropic, nematic, and smectic phases when the mixture is compressed at a fixed temperature. The DSS form chain-like structures, which remain randomly oriented at low densities where the LCs are in the isotropic phase. At intermediate and high densities, the DSS chains align along the nematic and smectic directors of LCs. We found that the DSS inside a chain follow a ferromagnetic ordering. However, the mixture does not show a significant macroscopic magnetization. The extent of nematic order in the DSS remains very similar to the LCs in intermediate densities. At high densities, the DSS have a lower extent of nematic order than the LCs. The structure of the LC–DSS mixture was further analyzed via projected pair correlation functions for distances parallel and perpendicular to directors in the nematic and smectic phases.

Heat capacity, entropy, configurational entropy, and viscosity of magnesium silicate glasses and liquids

In this work, five Mg-silicate glasses with compositions between MgSiO_3 and Mg_2SiO_4 were synthesized by aerodynamic levitation combined with laser melting. Low-temperature heat capacity (C_p) was measured (by relaxation calorimetry in the range 2–310 K) for all of them, with the resulting vibrational entropies at T = 298.15 K: sample MG50 with composition Mg_{0.996}SiO_{2.996} and entropy 72.88 J mol^{-1} K^{-1}; MG54 Mg_{1.174}SiO_{3.174} 78.54; MG58 Mg_{1.364}SiO_{3.364} 85.05; MG62 Mg_{1.611}SiO_{3.611} 91.40; and MG67 Mg_{1.907}SiO_{3.907} 102.75. Heat capacity of the glasses is higher than that of the corresponding crystal mixtures below 200 K but plunges below the C_{p,mathrm{crystal}} at higher temperatures. High-temperature C_p was measured (by differential scanning calorimetry in the range 300–970 K) for MG50 and MG67 up to approx 1000 K. Using our C_p data, selected data for entropies of fusion, C_p of crystals, and fictive temperatures, the configurational entropy (S_mathrm{conf}) at glass transition temperature (T_mathrm{g}) were calculated. For the near-forsterite glass MG67, the S_mathrm{conf} is 1.9 J mol^{-1} K^{-1} at T_mathrm{g} = 1040 K. As this small value is a difference of several large numbers, its uncertainty is relatively high; we consider a conservative estimate of 15 J mol^{-1} K^{-1}. Using the expression log eta = A + B/[T S_mathrm{conf}(T)], the available experimental viscosities (eta ) and the temperature-dependent configurational entropy from our work, we refined the parameters A = -2.34 and B = 76,500 for this equation, with S_mathrm{conf} (T) = 1.90+(83.7 ln (T/1040)). The configurational entropy for the enstatitic MG50 glass is 16.8 J mol^{-1} K^{-1} at T_mathrm{g} = 1063 K. The presented data can be combined with enthalpies of formation and thermophysical properties of Mg-silicate glasses for models that could elucidate geological and geophysical observations in the crust and mantle of the Earth.

Plant Polysaccharides Modulate Biofilm Formation and Insecticidal Activities of Bacillus thuringiensis Strains.

After the biological pesticide Bacillus thuringiensis (Bt) is applied to the field, it has to remain on the surface of plants to have the insecticidal activities against insect pests. Bt can form biofilms on the surface of vegetable leaves, which were rich in polysaccharides. However, the relationship between polysaccharides of the leaves and the biofilm formation as well as the insecticidal activities of Bt is still unknown. Herein, this study focused on the effects of plant polysaccharides pectin and xylan on biofilm formation and the insecticidal activities of Bt strains. By adding pectin, there were 88 Bt strains with strong biofilm formation, 69 strains with weak biofilm formation, and 13 strains without biofilm formation. When xylan was added, 13 Bt strains formed strong biofilms, 98 strains formed weak biofilms, and 59 strains did not form biofilms. This indicated that two plant polysaccharides, especially pectin, modulate the biofilm formation of Bt strains. The ability of pectin to induce biofilm formation was not related to Bt serotypes. Pectin promoted the biofilms formed by Bt cells in the logarithmic growth phase and lysis phase at the air–liquid interface, while it inhibited the biofilms formed by Bt cells in the sporangial phase at the air–liquid interface. The dosage of pectin was positively correlated with the yield of biofilms formed by Bt cells in the logarithmic growth phase or lysis phase at the solid–liquid interfaces. Pectin did not change the free-living growth and the cell motility of Bt strains. Pectin can improve the biocontrol activities of the spore–insecticidal crystal protein mixture of Bt and BtK commercial insecticides, as well as the biofilms formed by the logarithmic growth phase or lysis phase of Bt cells. Our findings confirmed that plant polysaccharides modulate biofilm formation and insecticidal activities of Bt strains and built a foundation for the construction of biofilm-type Bt biopesticides.

Pearl-inspired polymer films with chiral nematic and multi-lamellar structures

ABSTRACT Structural coloured materials have been widely found in nature. More and more artificial materials were created based on structural colour. However, fabrication of polymer films with pearly lustre remains a challenging task. Herein, a strategy is reported to prepare broadband reflection polymer films based on the fluorophilic association. A monomer with a perfluorooctyl chain is synthesised. After photo-crosslinking a mixture of a chiral nematic liquid crystal and the fluorinated monomer, broadband reflection film with pearly lustre is obtained. The broadband reflection originates from the broad distribution of the helical pitch. The pearly lustre is caused by the periodically ordered layers formed by the microphase separation between hydrocarbon and fluorocarbon chains.A strategy for the preparation of color liquid crystal polymer film with pearly luster is developed. The Bragg-reflection color originates from the supramolecular helical structure of the cholesteric liquid crystal and the pearly luster originates from the multilayer structure formed by the fluorocarbon/hydrocarbon microphase separation

A novel technique of fabrication of nanoparticle acrylate doped polymer dispersed liquid crystal (PDLC) film

In order to investigate the electro-optical characteristics of the current polymer dispersed liquid crystal (PDLC) film, zinc acrylate nanoparticles (NPs) were doped into the PDLC prepared samples. Generally for the fabrication of NPs–based PDLC film, two conventional methods such as the sandwich method and capillary methods are considered. In the conventional fabrication method of Np-doped PDLCs, the homogenous distribution of nanoparticles remained an unresolved issue. Particularly, upon the fabrication of Np-doped PDLC films, it is important to emphasis that nanoparticles are uniformly distributed inside the indium tin oxide (ITO) coated glass. For the purpose, here in this work, a new PDLC manufacturing method has been proposed to improve such shortcoming. Unlike the conventional method, the NPs acrylate layer was first coated on the ITO glass, which maintained evenly distributed NPs and then was placed onto the polymer/LC crystal mixture. By adopting the current PDLC fabricated method (with 1.0 wt% ZnA layer coating into PDLC film) the transmittance remained 93.9% and a good contrast ratio (CR) ∼ 7.0 was observed at a low driving voltage (∼ 20 V). Moreover the morphology study of current PDLCs showed a uniform size distribution of droplet morphology as well as a homogeneous distribution of NPs. Thus our investigations indicated that PDLC films prepared by this new technique achieved the goal of uniform distribution of NPs particles, homogeneous distribution of droplet morphology with the improved electro-optical characteristics.

Preparation of Carbamazepine-Nicotinamide Cocrystal

The focus of this investigation was to prepare the cocrystal of carbamazepine (CBZ) using nicotinamide as a coformer and to compare its different preparation methods. The cocrystal was prepared by grinding, solvent-Assisted grinding and ultrasound-assisted cocrystallization methods. They were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), and morphology by electron microscopy. In conclusion, ultrasound can be applied as a process intensification parameter along with cooling or slurry cocrystallization to produce pure cocrystals under conditions that might result in crystal mixtures in conventional processes.

Effect of Solution Composition on the Crystallization of Multicomponent Forms of Carbamazepine beyond Crystal Form and Shape: Surface as a Source of Diversity in the Solid-Form Landscape

This paper reports on the solution growth of carbamazepine dihydrate and discusses the relative development of the {h00} and {0k0} faces as a function of the crystallization conditions. While the overall shape of the obtained crystals remains lathlike, it is shown that from ethanol/water mixtures and at high water content (91 mol %) the dominant faces are {0k0}, whereas at lower water content (52 mol %) they are the {h00} faces. Our computational and systematic analyses suggest that the relative development of these faces is likely related to the anisotropic nature of the crystal structure and the existence of hydrophobic {0k0} and hydrophilic {h00} faces and as a consequence the importance of the ethanol/water composition in the crystallization mixture. The results of this solvent effect on crystal growth are further probed by assessing the characteristics and behavior of other multicomponent forms of carbamazepine, including one cocrystal and two solvates which are structurally related to the dihydrate. The kinetic effect of solution composition in the crystallization outcome appears to be more pronounced in CBZ·2H2O, although the 2:1 cocrystal with 1,4-benzoquinone and the formamide solvate also seem to vary as a function of solution composition. The results provide an illustration of how the crystal surface serves as an additional source of diversity in the solid-form landscape of pharmaceuticals, going beyond the crystal form and shape.

Quasi-Stationary States in Ionic Liquid-Liquid Crystal Mixtures at the Nematic-Isotropic Phase Transition

An open system is a system driven away from equilibrium by a source that supplies an inflow of energy and a sink to maintain an outflow. A typical example of an open system is a system close to its phase transition temperature under irradiation by a laser. This provides a steady flow of energy through a photon flux. The sink in that case is the environment to which energy is lost in the form of heat dissipation. Creation of such a thermodynamically open state suggests that we can expect generation of exotic spatio-temporal structures length-scale independent correlation maintained under the global dissipative forces provided by the surroundings. Internal long-range forces can bring in additional spatio-temporal correlations, giving rise to states with a very long lifetime, the ‘quasistationary states’ (QSS). In this communication, we report evolution of quasistationary states, in a mixture of the well-known liquid crystal (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) and an iron-based room temperature ionic liquid (RTIL), namely, 1-ethyl-3-methylimidazolium tetrachloroferrate (EMIF) at the Nematic-Isotropic phase transition, when focused radiation with 532 nm wavelength from a Nd:YAG laser (200-300 mW optical power) is incident on the sample. We explain the QSS by invoking a sharp negative thermal gradient due to the laser photon flux and dipolar interactions. In our model, the dipoles are the charge transfer complexes (CTCs) formed in the RTIL by resonant laser pumping, which create an orientational ordering and balance the fluctuating force of the thermal gradient to create the QSS. In the absence of such CTCs in a mixture of MBBA and a Gallium-based RTIL (1-ethyl-3-methylimidazolium tetrachlorogallate, EMIG), the QSS was not observed.

Kinetic Difference between Concomitant Polymorphism and Solvent-Mediated Phase Transformation: A Case of Tolfenamic Acid

Detection of two or multiple polymorphs in solution is a result of concomitant polymorphism or due to solvent-mediated phase transition. In this work, crystallization of tolfenamic acid (TFA) was conducted under several different supersaturation and temperature conditions. Form I and form II were identified from crystallized samples. Solute concentration and polymorph composition were respectively determined by UV–vis and Raman spectroscopy through the course of crystallization. Kinetic modeling was also conducted to further examine the crystallization kinetics, revealing that the observed simultaneous nucleation of the two forms is characteristically associated with an intermediate recession of the relative amount of form I in crystal mixtures. This unambiguous kinetic event proves to be indicative of the concomitant crystallization of TFA, shedding light on its nucleation mechanism.

Tuneable ferroelectric liquid crystal microlaser

ABSTRACT We demonstrate electric field tuning of Whispering Gallery Mode resonances in microdroplets of a dye-doped ferroelectric liquid crystal suspended in highly transparent fluorinated polymer solution CYTOP. The ferroelectric liquid crystal is a 9:1 mixture of CE3 and CE14 ferroelectric liquid crystals, exhibiting the ferroelectric Sm C* phase between 42°C and 74°C with a rather short helical pitch of 300 to 500 nm. In the Sm C* phase, the droplets show excellent optical homogeneity with perpendicular anchoring of liquid crystal molecules at the surface. Upon the excitation with a pulsed laser, the ferroelectric liquid crystal microdroplets emit laser light showing multimode WGM spectrum. When an external slowly varying electric field is applied along the direction of the excitation laser beam, we observe a red-shift of the WGM resonances, indicating an effective increase of the optical path for WGM resonant light. The shift is fully reversible, it is quadratic in the applied electric field and has a value of 4.5 nm at an electric field of 2 V. It is qualitatively explained by considering the soliton-like deformation of the helical ferroelectric Sm C* structure in an external electric field.