Fluorine Units Research Articles

Improving optoelectronic properties of the 2,7-polyfluorene derivatives with carbazole and oxadiazole pendants by incorporating the blue-emitting iridium complex pendants in C-9 position of fluorine unit

To study the influence of a blue-emitting iridium complex pendant on the optoelectronic properties of its 2,7-polyfluorene (PF) derivatives with the carbazole and oxadiazole pendants, a class of 2,7-PF derivatives containing carbazole, oxadiazole, and/without the cyclometalated iridium complex pendants in the C-9 positions of fluorene unit were synthesized. Their thermal, photophysical, electrochemical, and electroluminescent (EL) properties were investigated. Among these 2,7-PF derivatives (P1–P4), P2 and P3 exhibited higher photoluminescence efficiency in dichloromethane and better EL properties in the single-emissive-layer polymer light-emitting devices. The highest brightness of 3888 cd/m2 and the maximum current efficiency of 2.9 cd/A were obtained in the P2- and P3-based devices, respectively. The maximum brightness and efficiency levels were 1.7 and 2.1 times, respectively, higher than the corresponding levels from the parent 2,7-PF derivative (P1)-based devices. Our work indicated that EL properties of 2,7-PF derivatives can be improved by introducing the blue-emitting iridium complex into the alkyl side chain of fluorine unit as pendant. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis and properties of two novel copolymers based on squaraine and fluorene units for solar cell materials

Abstract Two novel copolymers based on squaraine and fluorine units have been synthesized through palladium catalyzed Suzuki coupling reaction and Sonogashira coupling reaction, respectively. The structures and properties of the two copolymers were characterized by FT-IR, NMR, UV–vis absorbance (Abs), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry (CV). The solution absorption spectrums of P1 and P2 show two distinct absorption bands, one locates at 300–500 nm and the other at 600–800 nm. The absorption spectrums of P1 and P2 in films are broadened obviously and the spectral responses are extended up to 900 nm. Thermal gravimetric analysis demonstrates that the polymers are stable. Cyclic voltammetry experiment shows that the band gaps of the copolymers are 1.65 eV and 1.67 eV, respectively, suggesting their potential for applications as solar cells materials.

Charge transfer and trapping properties in polymer gate dielectrics for non-volatile organic field-effect transistor memory applications

We investigate here charge transfer and trapping characteristics of various chargeable polymer dielectric layers, polystyrene (PS), poly(4-vinyl naphthalene) (PVN), and amorphous fluoropolymer (Teflon ® AF) in non-volatile pentacene field-effect transistor (FET) memory devices. Non-volatile memory properties, i.e., the degree of threshold voltage ( V Th) shifts (memory window), the programming and erasing bias, and the retention time, strongly depended on the selection of a charge storage layer, due to its electronic and dielectric properties. The pentacene FETs with PVN or PS showed reversible positive and negative V Th shifts by an application of external gate bias. In Teflon ® AF device, most significant positive V Th shift was obtained indicating a efficient electron injection whereas showed inefficient erasing characteristics via hole injection and storing due to a high electronegative properties of fluorine units in the dielectric. This result indicates importance of a selection of the chargeable polymer dielectric to obtain efficient organic non-volatile memory with a long retention time.

Surface Depletion of the Fluorine Content of Electrospun Fibers of Fluorinated Polyurethane

For materials containing fluorine, it has been generally accepted that fluorinated segments or end groups tend to aggregate in the outer surface because of the low surface energy, which endows the fluorinated materials with special surface properties such as self-cleaning, superhydrophobicity, and so forth. However, for the electrospun fibrous membranes of polyurethane elastomers containing perfluoropolyether segments (FPU), abnormal fluorine aggregations in the core of the electrospun fibers were observed. The XPS analysis indicated a rather low fluorine content at the surface of the electrospun FPU fibers. Further study with dynamic light scattering and fluorescence showed that FPU chains can form aggregates in the concentrated solution. Therefore, it can be deduced that the rapid evaporation of solvent and fast formation of fibers during the electrospinning process could result in the freeze-in of the aggregated chain conformation and the depletion of fluorine units on the surface of the electrospun FPU fibers.

Polyamine Acetylation Modulates Polyamine Metabolic Flux, a Prelude to Broader Metabolic Consequences

Recent studies suggest that overexpression of the polyamine-acetylating enzyme spermidine/spermine N(1)-acetyltransferase (SSAT) significantly increases metabolic flux through the polyamine pathway. The concept derives from the observation that SSAT-induced acetylation of polyamines gives rise to a compensatory increase in biosynthesis and presumably to increased flow through the pathway. Despite the strength of this deduction, the existence of heightened polyamine flux has not yet been experimentally demonstrated. Here, we use the artificial polyamine precursor 4-fluoro-ornithine to measure polyamine flux by tracking fluorine unit permeation of polyamine pools in human prostate carcinoma LNCaP cells. Conditional overexpression of SSAT was accompanied by a massive increase in intracellular and extracellular acetylated spermidine and by a 6-20-fold increase in biosynthetic enzyme activities. In the presence of 300 microM 4-fluoro-ornithine, SSAT overexpression led to the sequential appearance of fluorinated putrescine, spermidine, acetylated spermidine, and spermine. As fluorinated polyamines increased, endogenous polyamines decreased, so that the total polyamine pool size remained relatively constant. At 24 h, 56% of the spermine pool in the induced SSAT cells was fluorine-labeled compared with only 12% in uninduced cells. Thus, SSAT induction increased metabolic flux by approximately 5-fold. Flux could be interrupted by inhibition of polyamine biosynthesis but not by inhibition of polyamine oxidation. Overall, the findings are consistent with a paradigm whereby flux is initiated by SSAT acetylation of spermine and particularly spermidine followed by a marked increase in key biosynthetic enzymes. The latter sustains the flux cycle by providing a constant supply of polyamines for subsequent acetylation by SSAT. The broader metabolic implications of this futile metabolic cycling are discussed in detail.

A novel polymer anti-irritant barrier film for cosmetics

Currently, we encounter many chemical substances that can affect the skin through contact in our daily life. To keep these irritants away from us, it is very effective to create a dermal barrier film that can prevent penetration of irritants into the skin. For the purpose, we evaluated the permeation characteristics of currently available film-forming polymers, but almost all were found ineffective as barriers. Our investigation led us to fluoroalkylacrylate–polyglycolmethacrylate–alkylmethacrylate–copolymer (F–copolymer), a new acrylic copolymer. This polymer is soluble in water and can easily be incorporated into various cosmetic products. It consists of hydrophilic and lipophilic groups with fluorine units, and forms a durable, continuous film that is resistant to both water and oil upon drying. Testing on human subjects has demonstrated F-copolymer's effectiveness in countering irritation caused by water-soluble materials, including methyl paraben, lactic acid, and oil-soluble materials, like butyl paraben and methyl saricylate.

Photo-induced liquid crystal alignment of poly(vinyl cinnamate) and fluorinated polyimide blends

Liquid crystal(LC) alignment properties were mainly affected by surface properties of alignment layers. In our previous work, we prepared poly(vinyl cinnamate) (PVCi) and polyimide blend alignment layer for thermally stable LC alignment. In this work, we utilized fluorinated polyimide for blend alignment layers in order to modify surface properties of alignment layers. For this purpose, polyimides containing fluorine unit were synthesized and used for the blend alignment layers. Fluorine containing diamine, 4,4′-bis[2-(4-aminophenyl)hexafluoropropyl]-diphenyl ether(BDAF), is used for the polyimide synthesis. We prepared the fluorinated polyimide and PVCi blend alignment layers and investigated the effect of fluorine on the LC alignment properties and pretilt angle of LC.

Fluorinated photosensitizers: synthesis, photophysical, electrochemical, intracellular localization, in vitro photosensitizing efficacy and determination of tumor-uptake by 19F in vivo NMR spectroscopy

For in vivo NMR studies, starting from pyrroles, a series of fluorinated porphyrins were synthesized by following the MacDonald reaction conditions. Upon reaction with osmium tetroxide, a fluorinated porphyrin containing four trifluoromethyl groups (12 fluorine units) was converted into the related chlorin and bacteriochlorin which exhibited long-wavelength absorptions at 652 and 720 nm, respectively. All compounds produced good singlet oxygen production efficiency. A comparative study of nine porphyrins with and without fluorine substituents indicated no adverse effects of the presence of fluorinated groups in the photophysical properties of the porphyrins, chlorins or bacteriochlorins. The first and second one-electron reduction potentials (vs SCE) of the investigated compounds range between −1.29 and −1.49 V and between −1.66 and −1.84 V in PhCN containing 0.1 M TBAP. UV–visible spectroelectrochemical data suggested the formation of π-anion and π-cation radicals upon the first reduction and first oxidation. The in vivo 19F MR study of a representative fluorine labeled compound with twelve equivalent fluorines confirmed the presence of the fluorine labeled sensitizer in mouse (C3H/HeJ) implanted with RIF tumors on mouse foot dorsum by inoculating 2×10 5 cells (the studies were repeated on four tumored mice to confirm the feasibility and reproducibility). All fluorinated compounds were found to be quite effective in vitro. In a comparative intracellular localization study with Rhodamine-123 in RIF tumor cells, the most soluble porphyrin containing two propionic ester side chains was found to localize in mitochondria as well as the related chlorin and bacteriochlorin.

Synthesis and electroluminescence properties of novel silicon-based copolymers containing oxadiazole and fluorene units for PLED

Novel silicon-based copolymers containing an electron-deficient oxadiazole unit and a fluorine unit have been successfully synthesized through the Heck reaction. They are soluble in common organic solvents such as THF, CHCl3, etc. Their UV–visible absorption spectra exhibit a strong maximum band at the range of 355–381 nm in thin film. Upon a photoexcitation of 350 nm, their photoluminescence spectra show a strong maximum band around 455–475 nm in thin film. The multi-layered light-emitting diodes (LEDs) of Al(200 nm)/Ca(50 nm)/EL polymer(80 nm)/PEDOT(50 nm)/ITO were fabricated. J–V curves show the turn-on voltage in the range of 4.4–7 V. These LEDs emit the white emissive color, due to the combination of a blue electroluminescent (EL) color and a red EL color arising from the formation of a certain charge complex.

Synthesis and Structure of Low-Dimensional Gallium Fluorodiphosphates Seen during the Crystallization of the Three-Dimensional Microporous Gallium Fluorophosphate ULM-3

Two one-dimensional gallium fluorodiphosphates Ga(P2O7)F·H3N(CH2)3NH3·3H2O, 1, and Ga(P2O7)F·H3N(CH2)3NH3·H2O, 2, have been synthesized under mild conditions (<100 °C) from aqueous mixtures of Ga(NO3)3·6H2O, P2O5, 1,3-diaminopropane, and HF. Their structures consist of anionic chains of formula Ga(P2O7)F2- containing corner-sharing {GaO4F2} octahedra linked together via fluorine and P2O7 units, which are charge-balanced by propyldiammonium dications. During the hydrothermal synthesis of the open-framework three-dimensional ULM-3, compound 2 has been identified as the crystalline intermediate phase when phosphorus pentoxide is used as a starting material. This process has been followed in situ with time-resolved energy-dispersive X-ray diffraction (EDXRD), which reveals that dissolution of the one-dimensional phase 2 occurs before the rapid crystallization of ULM-3. If compound 2 is quenched from hydrothermal conditions, rapid and reversible conversion to compound 1 takes place. The two chain phases are thus solid precursors of the microporous ULM-3, and tracking the transformation process using in situ EXDRD shows that dissolution of 1 takes place before crystallization of 2 and then further transformation into the 3D phase, with the 1 and 2 acting as reservoirs of reactive species for ULM-3 crystallization.