High Fluorine Content Research Articles

Synthesis and equilibria in solutions of hafnium fluoro complexes with phosphoryl-containing bases Ph3PO, Bu3PO, and (Me2N)3PO

The composition and equilibria in solutions of the products of reaction of HfF4(dmso)2 with monodentate phosphoryl-containing bases L = Ph3PO, Bu3PO, and (Me2N)3PO in CH2Cl2 are studied by 19F NMR. Octahedral molecular complexes cis-[HfF4L2] and minor amounts of trans-[HfF4L2] and fac-[HfF3L3]+ cations were the main products for all ligands. The oxytrifluoride complex (μ-O)[HfF3(Bu3PO)2]2 and the [HfF5(Bu3PO)]– anion were identified in the case of Bu3PO. The conclusion about the formation of the hafnium oxytrifluoro complex was verified via hydrolysis of the product of reaction between HfF4 and Ph3PO upon exposure to air. As a result, (μ-O)[HfF3(Ph3PO)2]2 were detected; fine-structure 19F NMR resonance lines were obtained and the spin–spin coupling constant JFF was measured for the first time. Hydrolysis via adding a Bu4NOH solution in i-PrOH to the HfF4L2 solutions in CH2Cl2 did not yield the expected zirconium oxyfluoro complexes with the smaller number of fluorine atoms. Due to deeper hydrolysis, equilibrium in fluoride complexes shifted towards species with higher fluorine contents, [ZrF5L]– and [ZrF6]2–, resulting in the formation of Hf(O)x(OH)у(i-PrOH)z complexes that were not observed in the 19F NMR spectra and the substitution of the released fluoride ions for molecular ligands in HfF4L2 complexes.

Fluorine in Coal: The Modes of Occurrence and its Removability by Froth Flotation

ABSTRACTFluorine is one of the trace elements in coal that is harmful to the ecological environment and human’s health. Flotation, a method of fine-coal processing, may be useful in reducing the fluorine content in coal before coal combustion. For this purpose, a coal sample with high fluorine content (357 μg/g) was selected for the present work. The modes of occurrence of fluorine were examined by sequential chemical extraction, screening tests, and float-and-sink tests; the removability of fluorine in coal was investigated by bench-scale flotation tests. Results indicated that fluorine tends to enrich in large-density fractions and fine-size fractions; fluorine mainly occurred in residual-associated form and carbonate- and Fe/Mn-associated form. Flotation can play an important role in the removal of fluorine from coal. In this study, the optimal amount of flotation reagents was determined by statically designed experiments. Under the optimum condition of 100 g/t diesel oil, 150 g/t 2-octanol, and 200 g/t sodium hexametaphosphate and a 5-minute flotation time provided a 56.81% yield of clean coal. The relative fluorine removal rate was 57.84%, and a total of 76.05% of the total fluorine was removed.

Study on Treatment of acidic and highly concentrated fluoride waste water using calcium oxide-calcium chloride

There are problems with treating acidic waste water containing high concentration fluorine by chemical precipitation, including the low sludge setting velocity and the high difficulty of reaching the criterion. In Heilongjiang province, a graphite factory producing high-purity graphite generates acidic waste water with a high concentration of fluorine. In this paper, the effect of removals on the concentration of fluoride with the combined treatment of calcium oxide and calcium chloride were discussed with regard to acid waste water. The study improved the sludge characteristics by using polyacrylamide (PAM) and polymeric aluminum chloride (PAC). The effect of different coagulants on sludge was evaluated by the sludge settlement ratio (SV), sludge volume index (SVI) and sludge moisture content. The results showed that the optimal combination for 100 ml waste water was calcium oxide addition amount of 14 g, a calcium chloride addition amount of 2.5 g, a PAM addition amount of 350 mg/L, and the effluent fluoride concentration was below 6 mg/L. PAM significantly improved the sludge settling velocity. The sludge settlement ratio reduced from 87.6% to 60%. The process for wastewater treatment was easily operated and involved low expenditure.

(19)F Magnetic Resonance Imaging Signals from Peptide Amphiphile Nanostructures Are Strongly Affected by Their Shape.

Magnetic resonance imaging (MRI) is a noninvasive imaging modality that provides excellent spatial and temporal resolution. The most commonly used MR probes face significant challenges originating from the endogenous (1)H background signal of water. In contrast, fluorine MRI ((19)F MRI) allows quantitative probe imaging with zero background signal. Probes with high fluorine content are required for high sensitivity, suggesting nanoscale supramolecular assemblies containing (19)F probes offer a potentially useful strategy for optimum imaging as a result of improved payload. We report here on supramolecular nanostructures formed by fluorinated peptide amphiphiles containing either glutamic acid or lysine residues in their sequence. We identified molecules that form aggregates in water which transition from cylindrical to ribbon-like shape as pH increased from 4.5 to 8.0. Interestingly, we found that ribbon-like nanostructures had reduced magnetic resonance signal, whereas their cylindrical counterparts exhibited strong signals. We attribute this drastic difference to the greater mobility of fluorinated tails in the hydrophobic compartment of cylindrical nanostructures compared to lower mobility in ribbon-like assemblies. This discovery identifies a strategy to design supramolecular, self-assembling contrast agents for (19)F MRI that can spatially map physiologically relevant changes in pH using changes in morphology.

Electrical characterization of MIS structures with HfOx gate dielectric films fabricated on silicon substrates modified by ultra‐shallow ion implantation from RF plasma

AbstractThe feasibility of ultra‐shallow fluorine and nitrogen implantation from RF plasma into silicon substrates, and the correlation between implantation process parameters, and electro‐physical properties of obtained Metal‐Insulator‐Semiconductor (MIS) structures with hafnium oxide (HfOx) layer as a gate dielectric was investigated. The analysis of electrical characteristics of MIS structures proved that almost all fabricated structures after plasma implantation are characterized by lower flat‐band voltage (Ufb) value (in absolute values) and lower effective charge (Qeff) in comparison to reference samples. However, the limitation of such an improvement is the specified value of power applied to the reactive chamber (i.e., 120 W). MIS structures are also characterized by a lower leakage current and very significant increase in the breakdown voltage (Ubr) value. The structural characterization has demonstrated that both types of plasma implantation result in the introduction of the relatively high concentration of fluorine and nitrogen into silicon subsurface area. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Iodine in groundwater of the Guanzhong Basin, China: sources and hydrogeochemical controls on its distribution

Groundwater sampling at 179 sites in the Guanzhong Basin, China, indicated iodine concentrations ranging from 2 to 28,620 μg/L. 7.3 % of the sites have iodine concentrations 300 μg/L and are defined as “iodine excess water.” Sites with low groundwater iodine concentrations are mainly distributed at the edge of a piedmont alluvial–proluvial fan containing bicarbonate-rich water with a low mineral content, near-neutral pH values and low fluorine concentrations. The piedmont fan is characterized by a fast groundwater flow and active leaching of iodine from the sediments. Conversely, high groundwater iodine concentrations are principally located in silty or clayey sedimentary zones having low groundwater flow rates, weakly alkaline to alkaline pH values, and water containing HCO3·SO4, SO4·Cl and Cl·SO4 hydrochemical types. Elevated iodine concentrations in shallow groundwater commonly occur in discharge areas where there is a high rate of solute evaporation; elevated iodine concentrations in deep groundwater are likely attributed to microbial decomposition of organic matter under anaerobic conditions. Processes of iodine enrichment lead to correlations between high iodine and high fluorine contents in shallow groundwater, and between high iodine and high arsenic concentrations in deep groundwater. Moreover, redox processes and active water recycling are important factors for groundwater iodine enrichment.

Hydrogeochemical appraisal of fluoride in groundwater of Langtang area, Plateau State, Nigeria

Consumption of high fluoride in groundwater of Langtang area, manifest in the inhabitants of the area in form of dental fluorosis and skeletal fluorosis in older group. The aim of this study was to appraise the hydrogeochemistry of fluoride in the groundwaters of Langtang area. Thirty seven surface and groundwater samples and nine rock samples were collected in Langtang area for geochemical analysis. The Inductively Coupled Plasma Emission Spectrometry (ICPOES) was used to detect cations. The anions (Cl - , SO 4 = and Br - ) were determine by Ion Chromatography method. Fluoride was determined by the Specific Ion Electrode and bicarbonate was determined by titration. Major oxides, trace elements and rare earth elements for the rock samples were determined by the XRF method and fluorine by the Fusion method. Polished thin sections for rocks were prepared and studied. Geochemical results from analysis of the samples (rock and water) show that four major rock units make up the geology of the area; coarse porphyritic biotite granite, migmatite, rhyolite and riebeckite granites, the minor ones are pegmatite, trachyte, aplite and fine to medium grained biotite granites. The rhyolite, the riebeckite granites and trachyte have the highest level of fluorine content in the area (1,470, 1000, 900 and 800 ppm) respectively. The fluorine mineral (Fluorite) crystallized in the late stage of the magma as replacement of Fe/Mg mineral probably hornblende or biotite. Fluorine is leached into the groundwater from the rhyolite under the slightly alkaline (Ca-Mg-HCO 3 evolving Na-HCO 3 ) water in the area. The two major groundwater types (Ca-Mg-HCO 3 and Na-HCO 3 ) in the area have good relationship with content of fluoride in water. Although, the riebeckite granites have high fluorine content, contribution of fluoride from them is towards the southern portion of the map, owing to the groundwater flow direction. The different water sources in the area do not show variation in content of fluoride in water. However, groundwater barriers (dykes) may be responsible for some area having low fluoride (<1.5 mg/l) content. The consumption of high content of fluoride in the area has resulted in severe dental fluorosis in both children and youths and bowing of legs ( Genu Valgum ) in children with no discrimination between the sexes. Keywords: Fluoride, Fluorite, Fluorine, Fluorosis, Riebeckite Granite, Groundwater

Dual C-F, C-H Functionalization via Photocatalysis: Access to Multifluorinated Biaryls.

Multifluorinated biaryls are challenging to synthesize and yet are an important class of molecules. Because of the difficulty associated with selective fluorination, this class of molecules represent a formidable synthetic challenge. An alternative approach to selective fluorination of biaryls is to couple an arene that already possesses C-F bonds in the desired location. This strategy has been regularly utilized and relies heavily on traditional cross-coupling strategies that employ organometallics and halides (or pseudohalides) in order to achieve the coupling. Herein we report conditions for the photocatalytic coupling via direct functionalization of the C-F bond of a perfluoroarene and C-H bond of the other arene to provide an expedient route to multifluorinated biaryls. The mild conditions and good functional group tolerance enable a broad scope, including access to the anti-Minisci product of basic heterocycles. Finally, we demonstrate the value of the C-F functionalization approach by utilizing the high fluorine content to systematically build complex biaryls containing between two and five Caryl-F bonds via the synergistic use of photocatalysis and SNAr chemistry.

Fluoride removal from Double Leached Waelz Oxide leach solutions as alternative feeds to Zinc Calcine leaching liquors in the electrolytic zinc production process

The most important limitation of leached Waelz Oxide from the pyrometallurgical treatment of Electric Arc Furnace Dust (EAFD) is its high fluorine content. This work deals with the reduction of the harmful effects of the Double Leached Waelz Oxide fluorine content in the hydrometallurgical process for electrolytic zinc production process when it is used as raw material directly in the leaching stage. The resulting process is a purification treatment of Double Leached Waelz Oxide leach solution to remove the dissolved fluoride in this unpurified zinc liquor. Leached fluorides from this liquor are precipitated in order to reduce their concentration until the specified values, avoiding cathode corrosion in the electrowinning cells. In this paper a selective precipitation process to maximize the fluoride removal and to minimize the zinc losses is presented, achieving the industrially specified solution composition when the Zinc Calcine is the used raw material. The formation of aluminium-fluoride complexes and the variation of their solubilities with the pH evolution are the basis of the proposed treatment. In addition, this fluoride removal has also been improved and optimized in order to be integrated in the overall industrial hydrometallurgical process and the obtained results are presented and discussed proving the viability of this improved stage.

Comparison of fluoride effects on germination and growth of Zea mays, Glycine max and Sorghum vulgare

Fluorosis is a disease caused by over-exposure to fluoride (F). Argentina's rural lands have higher fluorine content than urban lands. Evidence confirms that plants grown in fluoridated areas could have higher F content. We compared F uptake and growth of crops grown in different F concentrations. The effect of 0-8 ppm F concentrations on maize, soybeans and sorghum germination and growth was compared. After 6 days seeding, the germination was determined, the roots and aerial parts lengths were measured, and vigor index was calculated. F content was measured in each part of the plants. Controls with equal concentrations of NaCl were carried out. Significant decrease in roots and aerial parts lengths, and in vigor index of maize and soybeans plants was observed with F concentrations greater than 2 ppm. This was not observed in sorghum seedlings. Also, the amount of F in all crops augmented as F increases, being higher in roots and ungerminated seeds. Sorghum was the crop with the highest F content. Fluoride decreased the germination and growth of maize and soybeans and therefore could influence on their production. Conversely, sorghum seems to be resistant to the action of F. © 2015 Society of Chemical Industry.

高硬質ナノ粒子添加ワックス素材の滑走特性評価

In Ski Jumping and Nordic Skiing, good gliding properties are required for success. Among many parameters, the tribological system is affected by the material properties of the ski running surface and various wax combinations that are applied on the top of the ski sole to minimize kinetic friction. The major research of this study has focused on the material changes due to the waxing process, in addition to the evaluation of the content of fluorine in waxes. Moreover, special attention has been paid to the additives like BN and SiC particles in nanometer size, mixed with high fluorine content waxes as powder. Characterization on the ski base materials, both with and without waxes, were evaluated by X-ray-fluorescence (XRF) analysis, Vickers hardness test, surface roughness analysis, contact angle measurement of water droplets, and tribometry to measure the coefficient of friction (C.O.F). It was found that the fluorine content in waxes on the top surface was not directly affected by the hardness, the surface roughness and the contact angle. The COF on ice was slightly lowered with the increase of fluorine content in waxes. The hardness was significantly improved by the addition of BN and SiC nanoparticles in high fluorine content waxes, especially twice as high as that for the case of BN nanoparticle, without any degradation in the surface roughness and the contact angle.

Synthesis and characterization of novel acrylic comb-shaped copolymer containing long fluorinated side chains

A novel acrylic comb-shaped copolymer containing long fluorinated side chains (ACCLF) was successfully synthesized by conventional radical polymerization of a novel mono-methacryloyloxy terminated fluorinated macromonomer (PHFBMA-MA), methyl methacrylate (MMA), isobutyl acrylate (IBA), and γ-methacryl propyl trimethoxyl silane (MPTS). GPC, FTIR, and 1H-NMR data successfully verified the synthesis. The influence of both the molecular weight and concentration of PHFBMA-MA on the surface properties of ACCLF films was investigated. By increasing both the concentration and the molecular weight of PHFBMA-MA, the surface energy of the films decreased and contact angle increased. The surface energy of ACCLF-1/3-8 with just 8 wt% PHFBMA-MA-1/3 (20.68 mN/m) was almost the same as that of the neat PHFBMA (20.36 mN/m), indicating the high efficiency of the macromonomer in lowering the surface energy of the comb-shaped copolymer. The surface composition of ACCLF was characterized and quantified by X-ray photoelectron spectroscopy (XPS). XPS results strongly confirmed that, at the same fluorinated content, long fluorinated chains modified film (9.36 % fluorine content for ACCLF-1/3-4 and 8.19 % fluorine content for ACCLF-1/6-4) showed higher fluorine concentration at the top surface than that of ACSF-4 modified film (1.52 %). ACCLF films also had excellent adhesion [on glass, tin plate, and polycarbonate (PC)], pencil hardness, and thermal properties. The novel ACCLF prepared via conventional radical polymerization not only had excellent comprehensive performance, but also has prominent potential application in large-scale industrialization.

Study of Microorganism Trench-Leaching of a Chinese High Fluorine-Bearing Uranium Ore

The microorganism trench-leaching process of a low-grade uranium ore with a high content of fluorine was experimentally studied through the technique of Real-time PCR by using the fluorine-tolerance bacteria of Retech-3 as the leaching-ore bacteria. It was found that the Retech-3 strains of fluorine-tolerance domestication grown well in a fluoride solution with concentration of 0.0~3.0 g·L-1, and the oxidation of Fe2+ ions to Fe3+ ions occurred rapidly to promote the extraction of uranium. The experimental results showed that the bioleaching rate (89.82%) of uranium can be improved of 13.80% than acid leaching in 30 days with 65 kg ore and its particle size of-6 mm (fraction of 100%) in trench. The Real-time PCR analysis of microbial population compositions revealed that Retech-3 strains were mainly composed of Leptospirillum sp. and Acidithiobacillus sp. in the leaching process. The obvious improvements of fluorine-tolerance domestication of bacteria and the uranium leaching process will provide fundamentals for the smooth utilization of a high fluorine-containing uranium ore with the aid of microorganism trench-leaching.

Variations in the chemical composition of lamprophyllite-group minerals and the crystal structure of fluorine-rich barytolamprophyllite from new peralkaline dyke

The variations in the chemical composition of lamprophyllite-group minerals from a peralkaline dyke of the Mokhnatye Roga area (Kandalaksha region, Kola Peninsula), which are crystallized during the entire period of dyke formation and form several generations, have been investigated. The early generations differ in a steadily high fluorine content, while the later ones exhibit reduced amount of fluorine, impurity elements, and sodium, with a simultaneous increase in the potassium content. The crystal structure of fluorine- rich barytolamprophyllite (potentially a new representative of the lamprophyllite group, differing by the predominance of fluorine in the anion X site) has been analyzed by single crystal X-ray diffraction. This mineral is found to have a monoclinic unit cell with the following parameters: a = 19.5219(8) A, b = 7.0915(2) A, c = 5.3925(2) A, β = 96.628(3)°, and sp. gr. C2/m. The structure is refined to R = 5.73% in the anisotropic approximation of the atomic displacement parameters using 3668I > 2σ(I). The idealized formula (Z = 2) is (Ba,Sr)2[Na(Na,Fe)2(Ti,Mg)F2][Ti2(Si2O7)2O2].

Identification of organic fluorides and distribution of organic species in an anthracite with high content of fluorine

Identification of organic fluorides and distribution of organic species in an anthracite with high content of fluorine

Synthesis and characterization of highly-fluorinated colorless polyimides derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) and aromatic dianhydrides

The authors report the synthesis and characterization of a polyimide (PI) series derived from 4,4′-((perfluoro-[1,1′-biphenyl]-4,4′-diyl)bis(oxy))bis(2,6-dimethylaniline) (8FBPODMA). The 8FBPODMA monomer containing a perfluorobiphenyl group with two 2,6-dimethylaniline units connected by an ether bond was synthesized and polycondensed with several aromatic dianhydrides, including 4,4′-biphthalic anhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA), pyromellitic dianhydride (PMDA), and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), by the traditional two-step imidization procedure. All PIs shows high optical transparency, higher than 80% at 500 nm for a thickness of ca. 10 μm and good thermal properties. The thermal decomposition temperatures (T10%) of the PIs are in the range of 507–527 °C and the glass transition temperatures (Tg) are in the range of 280–345 °C. In addition, the PIs have low refractive indices because of their high fluorine contents. In particular, 8FBPODMA–6FDA shows a very low refractive index (1.5389) and a low birefringence (0.0054) at 637 nm.

Construction of Highly Ordered Fluorinated Graphene Composite Coatings with Various Fluorine Contents for Enhanced Lubrication Performance

The presence of fluorine makes fluorinated graphene (FG) exhibit extraordinary properties and provides effective route to engineer and modulate the surface and interface properties, which endows FG with promising prospect as ultrathin solid lubricant. Herein for the first time, a strongly integrated FG composite coating was fabricated by facile and scalable solution-based process. The pretreatment with alkali hydroxides both enhances the dispersibility of FG in aqueous medium and realizes the control of fluorine content. The incorporated dopamine could simultaneously function as adhesion and mechanical buffer layer. The as-prepared coatings almost show the full coverage (>90 %) of FG nanosheets over centimeter scale substrates with uniform thickness of 2.36–2.66 nm. The synthesis–structure–performance relationship, particularly the influence of fluorine content and coating structure on the lubricating properties, has been systematically investigated and discussed. Based on this fascinating testing platform, the results of tribological investigations demonstrate the composite coating with higher fluorine content has more stable friction state, lower friction coefficient, and longer duration.

Segmented Highly Branched Copolymers: Rationally Designed Macromolecules for Improved and Tunable (19)F MRI.

Highly branched polymers are a promising platform for the design of next-generation contrast agents for (19)F magnetic resonance imaging (MRI). A series of segmented highly branched polymers (SHBPs) consisting of fluoro- and PEG-based monomers were synthesized by self-condensing vinyl copolymerization (SCVP) using the reversible addition-fragmentation chain transfer (RAFT) technique. SHBPs having different compositions and degrees of branching were obtained by varying the monomer type and feed ratio of monomer to chain transfer agent (CTA). The chemical structures and physical properties of the branched polymers were thoroughly characterized in detail by NMR, SEC and DSC. The systematic variation in structural parameters allowed the relationships between molecular structure, sequence distribution, and imaging performance to be examined. The (19)F NMR properties were strongly affected by the sequence distribution of the fluorinated monomers, the type of polymer backbone and the degree of branching. As a result, SHBPs consisting of statistical copolymeric segments of acrylate units were identified as excellent candidates for imaging due to a single (19)F signal, long T2 relaxation times, and high fluorine contents. The SHBPs could be all imaged or selectively imaged by taking advantage of the differences in relaxation times, demonstrating tunable and selective imaging performance through tailoring the structure and composition of the SHBPs.

Compositional Evolution and Formation Conditions of Magmas and Fluids Related to Porphyry Mo Mineralization at Climax, Colorado

To reconstruct the magmatic–hydrothermal processes leading to porphyry Mo ore formation at the Climax Mo mine, Colorado, four magma units that were emplaced before, during and shortly after the mineralization events were investigated: (1) a pre-mineralization white dike of the Alma district; (2) the syn-mineralization Chalk Mountain Rhyolite; (3) a late- to post-mineralization rhyolite porphyry dyke; (4) a mafic enclave within the productive Bartlett stock. Melt inclusions, mineral inclusions and fluid inclusions in quartz phenocrysts were investigated by means of laser ablation inductively coupled plasma mass spectrometry, electron microprobe and microthermometry. Based on melt inclusion data both the Chalk Mountain Rhyolite and the rhyolite porphyry were � 10 times more fractionated than average granite and show geochemical characteristics of topaz rhyolites. They were saturated in magnetite, Mn-rich ilmenite, fluorite, aeschynite, monazite, pyrrhotite and thorite, and crystallized predominantly at 710–730 � C, 1� 2–2� 6 kbar and log fO2 � FMQ þ 2� 2 (where FMQ is fayalite–magnetite–quartz). The silicate melt of the Chalk Mountain Rhyolite contained 3� 5 6 0� 4 wt % F, 0� 09 6 0� 03 wt % Cl, � 3� 0w t %H 2O, 15–90m gg –1 Cs, 500–1500m gg –1 Rb and 5–7m gg –1 Mo, whereas that of the rhyolite porphyry contained 1� 1 6 0� 3 wt % F and 4� 9 6 1� 2w t % H2O, but otherwise had a virtually identical major and trace element composition. The fluid exsolving from the latter melt had a bulk salinity of 10 6 2 wt % NaClequiv and contained of the order of 100m gg –1 Mo. After emplacement of the Chalk Mountain Rhyolite magma at subvolcanic levels, extremely fractionated silicate melts coexisting with hypersaline brines (salt melts) and low-density vapor percolated at near-solidus conditions through the rock. These silicate melts contained 6� 6 6 0� 4w t % F,� 7� 5 6 0� 6w t %H 2O, 0� 51 6 0� 05 wt % Cl, and up to 0� 5 wt % Cs and 100m gg –1 Mo, whereas the hypersaline brines contained 1–2 wt % Cs and 0� 3–0� 6 wt % Mo. However, owing to their negligible masses these liquids are unlikely to have played a major role in the mineralization process. The majority of Mo in the Climax deposit appears to have been derived from melts containing 5–7m gg –1 Mo and bulk fluids containing � 100m gg –1 Mo. These concentrations are similar to those found in similarly fractionated melts and fluids in barren and sub-economically mineralized intrusions. However, whereas in the latter intrusions fractionated melts occurred in a rather dispersed state, they seem to have been present as large, coherent masses in the apical parts of Climax-type porphyry Mo-forming magma systems. Efficient segregation of fractionated melts and fluids into the top of mineralizing magma chambers appears to have been promoted by high fluorine concentrations in the silicate melt, which was partly a primary feature, and partly an indirect consequence of other characteristics of within-plate magmatism.

Synthesis of novel fluorinated bis(biphenyl)diacetylene derivatives as highly birefringent nematic liquid crystalline materials

Three novel fluorinated bis(biphenyl)diacetylene (1,4-bis(biphenyl-4-yl)buta-1,3-diyne) derivatives, with alkoxy tails at the terminal positions, were prepared for use as high-birefringent nematic materials. To lower the thermal transition temperatures and determine the origin of the nematic phase of these compounds, fluorine atoms were introduced at lateral positions. Thermal transition temperatures and mesomorphic properties were investigated by differential scanning calorimetry and polarized optical microscopy. In addition, birefringence was measured using a microscopic method based on the interference method. Both the nematogenic properties and optical performances depended not only on the number of fluorine substituents, but also on the position of the substituents. The compound having the highest fluorine content exhibited the lowest birefringence, and the compound bearing fluorine atoms only on the inner benzene rings of the biphenyl cores exhibited an enantiotropic nematic phase with a maximum birefringence value of 0.48 at 550 nm and 140 °C.