Fluorene Groups Research Articles

Nanorings Resembling Beehives for Ultrasensitive Fluorescence Detection.

In this study, we showcase the fabrication of two nanorings resembling beehives using intricately designed donor-acceptor (D-A) fluorophores. The D-A fluorophores, featuring three twisted fluorene groups on each side of the acceptor group, adopt a bent conformation that promotes the creation of a nanoring morphology upon aggregation. With porosity for maximum binding sites, high emission efficiency, and well-organized arrangements, the nanoring-based hives offer exceptional sensitivity and selectivity in the detection of organic sulfides. Particularly, nanorings formed from benzselenodiazole-containing molecules exhibit heightened sensitivity, achieving a limit of detection (LOD) of 0.2 ppb for dimethyl sulfide and 17 ppb for dimethyl disulfide. Due to its unparalleled sensitivity and selectivity, which was not achievable with previous optical sensors, this technology enables the continuous monitoring of meat spoilage in its early stages on an hourly basis. This provides crucial insights into the exact moments when freshness begins to deteriorate and how long the meat can be stored for.

Structural designs and synthesis of co-polycarbonates with cyclohexyl and fluorene structures: Low-dielectric constant, high solubility, and superior mechanical properties

The rapid developments of high-speed communication and large-scale integrated circuits have accelerated the research for insulating dielectric materials with low dielectric constant, low dielectric loss, and good mechanical properties. In this study, a series of polycarbonate resins containing cyclohexyl and fluorene structures are synthesized by melt transesterification, which is low dielectric, highly thermally resistant, and soluble. The effects of fluorene structure contents on the properties of a co-polycarbonate resin were studied systematically. The results showed that the non-polar fluorene group could reduce the molecular polarization of co-polycarbonate, resulting in low permittivity of co-polycarbonate are 2.41-2.71@1MHz. In addition, the resin has excellent solubility and can be dissolved in NMP, CH2Cl2, THF, and other solvents at room temperature. Furthermore, the co-polycarbonate resins also exhibit superior heat resistance with glass transition temperature (Tg) of 160.6-173.1 °C as well as admirable mechanical properties with a tensile strength of 50.54-70.72 MPa. This makes it a promising candidate for high-speed communications and large-scale integrated circuits.

Bifunctionalized MOFs modified poly (aryl ether ketone sulfone) ultrafiltration membranes with high-efficient BSA separation and dye adsorption

In this study, by connecting the amino ligand in ZIF-8-NH2 with an alkyl side chain containing sulfonic acid groups in a one-step method, a novel nanofiller (ZIF-8-NS) with bifunctional amino and sulfonic acid groups was formed. Sulfonated poly (aryl ether ketone sulfone) containing fluorene group (F-SPAEKS) was chosen as the polymer matrix. The nanofiller not only had good hydrophilicity but also had electrostatic interaction with the polymer matrix, which effectively promoted the compatibility problem among the polymer matrix and the filler. The nanofillers were characterized by XRD, FT-IR, SEM and XPS. The composite membranes were prepared by the NIPs method. The antifouling and separation properties of the prepared mixed matrix membranes (MMMs) were investigated using positively charged dye (RHB) and negative charge bovine serum albumin (BSA) as model contaminants. The water flux of the pure membrane achieved 529.16 L/m2 h. When the addition amount of ZIF-8-NS was 0.1 %, the water flux of M4 (F-SPAEKS/ZIF-8-NS-0.1 %) could reach 838.84 L/m2 h. The retention rate of the BSA solution could reach 99.06 %, and the FRR value was kept at a high level (81.45 %). Meanwhile, the dynamic retention of M4 on the primary adsorption of the dye RHB could even reach 99.89 %. Therefore, the innovative design of the novel MMMs not only improved the flux, retention, and other separation properties but also enhanced their excellent adsorption capacity for RHB dyes. This result indicated that the nanofiller ZIF-8-NS provided an interesting reference for the study of ultrafiltration membranes.

High stable poly (terphenyl-co-fluorene quinuclidinium) anion exchange membrane for alkaline water electrolysis

Developing anion exchange membranes (AEMs) is an effective way to reduce the cost of water electrolyser systems and fuel cell systems because of the no requirement of platinum-group-metal (PGM) catalysts. However, low conductivity and poor stability are the bottlenecks that constrain its development. In this work, we propose a series of performance enhanced poly (terphenyl-co-fluorene quinuclidinium) (TPFQ) AEMs. The hydroxide conductivity of TPFQ-10 reached 178.5 mS cm−1 at 80 °C. The rigid fluorene group gives the membrane better dimensional stability (swelling ratio: 7.7% in pure water and 1.2% in 10 M NaOH at 80 °C for TPFQ-10). In particular, the membranes exhibit extremely high alkaline stability, with almost no conductivity loss over more than 2000 h in a 10 M NaOH solution. The AEM water electrolysers (AEMWEs) with nickel-alloy foam electrodes shows an excellent current density of 2.32 A cm−2 at 2.0 V. The AEMWEs can work steadily at a current density of 0.5 A cm−2 in 5 M NaOH at 80 °C for more than 500 h, with a low voltage rising rate of 56 μV h−1.

Sensing of Co2+ and Cu2+ Ions Using Dimethylamino-functionalized Poly(azomethine-1,3,4-oxadiazole)s.

The ability of OxT and OxFl azomethines to recognize metal ions in THF solutions was investigated using UV-vis absorption techniques. Various metal ions, including Cd2+, Hg2+, Co2+, Sn2+, Cu2+, Ni2+, Zn2+ and Ag+, were tested. The absorption spectra revealed two distinct π-π* transition bands in the 273-278nm and 330-346nm wavelength ranges. Additionally, OxFl displayed an absorption peak at 309nm, attributed to the fluorene group. Spectral titrations were used to study the fluorescence behavior in the presence of these metal ions. The results showed significant quenching with Co2+ and Cu2+ ions, while other metal ions had minimal effects on the fluorescence intensity. The quenching mechanism was further analyzed using the Stern-Volmer and Lehrer equations, and the binding constants ( ) were calculated using the Benesi-Hildebrand relations. The results confirm that Co2+ has a 1:2 stoichiometry and Cu2+ has a 1:1 stoichiometry, indicating the strong affinity of OxFl and OxT for these ions. The negative values of ΔG (Gibbs free energy) suggest that complex formation occurs spontaneously at room temperature.

Design, synthesis and characterization of high refractive index aromatic polyesters containing fluorene and thioether groups

9,9-bis(4-hydroxyphenyl)fluorene (BPF) is a highly structurally symmetric bisphenol with excellent optical properties of low birefringence and high refractive index, however, the glass transition temperature ( Tg) of its polyester is high ( Tg>300°C), which makes it difficult to be thermally processed and limits its application. On the other hand, 4,4′-Thiobis (2-methylphenol) (T2MP) has a flexible thioether group, its introduction not only brings high refractive index, but also can appropriately reduce the Tg of the polymer. Therefore, by combining the advantages of both of them, we prepared aromatic polyesters with high refractive index and stabilization. This study provides a route that can appropriately reduce Tg without loss of refractive index.

Study of the Dielectric and Corona Resistance Properties of PI Films Modified with Fluorene Moiety/Aluminum Sec-Butoxide.

With the policy tilt and increased investment in research and development in the world, new energy vehicle technology continues to progress and the drive motor power density continues to improve, which puts forward higher requirements for the comprehensive performance of the core insulating material enameled wire enamel for drive motors. Polyimide (PI) has excellent electrical insulation properties, and heat resistance is often used to drive the motor winding insulation. To further improve the corona resistance and insulating properties of PI wire enamel varnish, in this paper, firstly, fluorene groups with a rigid conjugated structure were introduced into the molecular chain of the PI film by molecular structure modulation, and then uniformly dispersed alumina nanoclusters (AOCs) were introduced into the PI matrix by using an in situ growth process to inhibit the migration of high-energy electrons. The quantum size effect of the alumina nanoclusters was exploited to synergistically enhance the suppression and scattering of energetic moving electrons by PI-based composite films. The results show that the breakdown field strength of the PI-based composite film (MPI/1.0 vol% AOC) reaches 672.2 kV/mm, and the corona resistance life reaches 7.9 min, which are, respectively, 1.55 and 2.19 times higher than those of the initial PI film. A PI-based composite film with excellent insulating and corona resistance properties was obtained.

Adjusting structure-activity relationship to obtain hybrid proton exchange membrane with enhanced transport efficiency by introducing functionalized nano-coated MOFs

Designing proton exchange membranes (PEMs) with high H+ conductivity and good dimensional stability has been a challenge. The porous structure of ZIF-8 could load ionic liquids (IL) (ZIF-8@IL). The ZIF-8@IL was coated by sulfonated polydopamine (SPDA), then ZIF-8@IL-SPDA as proton conductors was fabricated. ZIF-8@IL-SPDA would not lose in water environment like small molecule proton conductors (such as sulfuric acid, phosphoric acid, imidazole, etc.). The different loadings of ZIF-8@IL-SPDA were introduced into sulfonated poly (aryl ether ketone sulfone) containing fluorene groups (F-SPAEKS). The novel composite PEMs was investigated. The prepared hybrid matrix membrane with optimum ZIF-8@IL-SPDA doping content (1.5 wt%) showed the highest H+ conductivity of 149.87 mS cm−1 at 80 °C. In addition, a maximum peak power density of 818 mW cm−2 was achieved in a single-cell performance test of this membrane. The good dispersion of ZIF-8@IL-SPDA nanoparticles in the F-SPAEKS matrix reduced the fuel cross-over flux to 2.15 mA cm−2. Therefore, the newly prepared hybrid matrix membranes were expected to be applied in proton exchange membrane fuel cells.

Fluorene and Tetraphenylsilane Based Conjugated Microporous Polymer Nanoparticles for Highly Efficient Nitroaromatics Detection in Aqueous Media

AbstractConjugated microporous polymers (CMPs) are considered promising sensing materials for the detection of nitroaromatics. Unfortunately, the photoluminescence (PL) sensing application in water media is limited, owing to the poor solubility/dispersion in aqueous media. Here, two novel CMPs named poly(dimethylfluorene‐co‐tetrakis(4‐phenyl)silane)s (P4SiF) and poly(dimethylfluorene‐co‐tetrakis(3‐phenyl)silane)s (P3SiF) nanoparticles based on fluorene group and tetraphenylsilane unit are prepared using Suzuki coupling in water/toluene miniemulsion. P4SiF and P3SiF possess spherical particle morphology with sizes of 45 and 60 nm, respectively, and porous structure with pore diameters of both 1.9 nm. PL sensing experiments based on P4SiF and P3SiF nanoparticles in aqueous media show a sensitive and selective detection toward 2,4,6‐trinitrophenol (TNP). It is worth noting that the PL quenching effect toward TNP is not significantly changed after the addition of other nitro compounds, proving the excellent anti‐interference characteristic and highly selective detection of the polymers in water. Moreover, the t‐test indicates that the PL sensing method using P4SiF and P3SiF nanoparticles as sensing materials realizes the reliable detection of TNP in actual water samples at a 95% confidence level. Finally, the PL sensing mechanism is investigated, showing that the inner filter effect is the main factor in the PL quenching process of TNP in aqueous media.

The effect of 3D printing fluorene-containing poly (aryl ether ketone)/poly (ether ketone) blends on interlayer strength

The limited diffusion and entanglement of the chains between beads cause pronounced anisotropy in the mechanical properties of 3D printed parts. Therefore, amorphous poly (aryl ether ketone) (aPAEK) containing fluorene groups with high intrinsic strength and good interfacial fusion is synthesized and employed to improve the interlayer adhesion of poly (ether ether ketone) (PEEK) parts. Herein, we designed an aPAEK with high intrinsic strength and good interfacial fusion with PEEK blends. The tensile strength of 30 mol% fluorene groups aPAEK was improved to 75 MPa, and the interlayer strength of 20 wt% blends was increased by 315 % compared to PEEK. Moreover, the selection of an appropriate molecular weight for aPAEK is crucial in maintaining the elevated tensile strength while promoting interlayer diffusion during the printing process. These results highlight a novel strategy for the design and development of blend polymers for interlayer reinforcement in 3D printing applications.

Photophysical properties of several multi-branched oligomers: An ultrafast excited state dynamics and quantum chemical calculation study

Multi-branched oligomers F1, F2 and F3 were investigated by spectroscopic experiments as well as quantum chemical calculations to elucidate the structure–property relationships and intramolecular charge transfer (ICT) characteristics of typical nonlinear optical materials. A better ICT property of F2 is obtained by replacing terminal electron donors with stronger electron-donating ability. The degree of ICT is effectively increased, which can be clearly seen from the frontier molecular orbitals contribution of central anthracene between HOMO and LUMO. The central group plays a major role in the direction as well as effective path of ICT process. In the X-shaped oligomers with anthracene as central group, ICT process takes place from terminal groups of [Formula: see text] position branches, to the central anthracene group. However, the electron distribution as well as the ICT of tri-branched oligomer F3 with triazine as central group is not symmetric. ICT process of F3 takes place from terminal triphenylamine groups to the central triazine and two fluorene groups at [Formula: see text] position branches. Y-shaped oligomer F3 has a longer lifetime of ICT state as well as a higher fluorescence quantum yield, which is consistent with the results of time-resolved fluorescence spectroscopy. Z-scan results show that the TPA cross-section value of F3 is 10.6 and 2.9 times higher than that of X-shaped F1 and F2. The dynamics curves of transient absorption spectroscopy also indicate that oligomer F3 structure has relatively stronger ICT properties. To verify the substituent effect, two linear molecules F4 and F5 were also calculated. The quantum chemical calculations result shows that the branches at positions 4 and 11 of the central anthracene group have little effect on the electron cloud distribution, and there are indeed significant differences in the contributions of branches at different positions. Our results may provide some reference for molecular design.

Design and Synthesis of Low Dielectric Poly(aryl ether ketone) from Incorporation Bulky Fluorene Groups and Regular Hydroquinone Structure.

To decrease the dipole polarization rate and reduce the dielectric constant of poly(aryl ether ketone) (PAEK) resin, 1,4-di(4-fluorobenzoyl) cyclohexane (DFBCH), a weakly polarizing cyclohexane-based monomer, was designed and synthesized as the primary reactant. The bulky fluorene group was incorporated to increase the free volume of the resin, further reducing the dielectric constant. Additionally, hydroquinone with a symmetric and regular structure was utilized to enhance the molecular chain's regularity and reduce dipole relaxation, further lowering the resin's dielectric constant and dielectric loss. The PFQEKs series resins exhibited excellent thermal stability with glass transition temperature (Tg) ranging from 222 to 239 °C and 5% weight loss (Td5%) ranging from 458 to 463 °C, with different monomer ratios. As the hydroquinone content increased, the dielectric constant (Dk) and dielectric loss (Df) of the resin decreased significantly, with Dk ranging from 2.92 to 2.77 and Df ranging from 0.011 to 0.008 at 10 GHz.

Synergistically Improving the Thermal Conductivity and Mechanical Strength of PEEK/MWCNT Nanocomposites by Functionalizing the Matrix with Fluorene Groups

AbstractNanofiller reinforcement is an effective method to prepare high thermally conductive polymer‐matrix composites. However, the poor dispersion of nanofillers and high interfacial thermal resistance between the filler and matrix seriously affect the thermal conductivity and mechanical properties of composites. To solve this problem, a small amount of conjugated fluorene group is introduced into the polymer chain of poly (ether ether ketone) (PEEK) to afford the fluorene‐functionalized copolymer matrix (FD‐PEEK). In an in situ polymerization procedure, the matrix non‐covalently binds to multi‐walled carbon nanotubes (MWCNT) to allow highly filled PEEK/MWCNT nanocomposites. With the filler dispersion and matrix–filler interfacial bonding improved, the prepared nanocomposites possess both high thermal conductivity and tensile strength. At the optimal ratio of 2 mol% fluorene groups in the polymer chain, the nanocomposite with 10 wt% MWCNT exhibits an excellent thermal conductivity of 2.41 W m−1 K−1, which is 868% higher than pristine PEEK, with tensile strength remaining 104.3 MPa. The PEEK/MWCNT nanocomposites can be further used as matrix resins to build double‐segregated network multi‐component composites, which contributes to an innovative strategy to design high‐performance thermally conductive materials.

ПОЛИАРИЛЕНЭФИРКЕТОНЫ В КАЧЕСТВЕ ПРОВОДНИКА В ТОКОСЪЕМНОЙ СИСТЕМЕ СОЛНЕЧНОГО ЭЛЕМЕНТА

The paper investigates the thermomechanical and electrical properties of a number of thermoplastic copolymers poly(arylene ether ketones) (co-PAEK) containing fluorene groups in the main chain of the macromolecule. Co-PAEKs are being studied for the purpose of their use in the contact system of a solar cell with a transparent conductive oxide (TCO) electrode and a multiwire contact grid. Polymer films are used as conductive adhesives to form an electrical contact between metal wire and TCO. The formation of an electrically conductive contact occurs during lamination at an excess pressure of 1 atm and a temperature of maximum deformation of co-PAEK, while the copolymer switches from the initial dielectric to a stable highly conductive state. Co-PAEKs with the content of fluorene groups ( q ) 5, 10, 15, 20 and 25 mol.% are synthesized, having the same molecular weight and the reduced viscosity of ~0.38 dl/g. To select the optimal contact system formation temperature for each coPAEK, the glass transition temperature ( T g) and the peak strain temperature ( T d) were determined from thermo mechanical curves. It was found that with increasing q , the temperature T g increases from 162 to 185°С, and T d from 203 to 223°С. The specific contact resistances (ρС) in the metal wire/co-PAEK/TCO (ITO - In2O3:Sn) system were determined for a round copper wire coated with indium:tin (In:Sn) solder, as well as for tin-plated wire, depending on the content of fluorene groups in the copolymer. The specific contact resistance ρС for wire with (In:Sn) solder varies in the range of 0.56-0.83 mΩ cm2, for tin-plated wire - 0.84-1.43 mΩ cm2, and co-PAEK with q = 5 mol % showed the lowest ρС in both cases. The ρC of wire/co-PAEK/ITO contacts has been studied as a function of the resistivity of ITO grown by ultrasonic spray pyrolysis on silicon substrates. The temperature dependence of the resistivity of the wire/co-PAEK/ITO contact was studied in the temperature range of 5-85°C, and a conclusion was made about the metallic type of dependence. According to the results of microscopic studies of the contact area, the typical minimum co-PAEK layer thickness between the wire and ITO after the formation of the contact was determined, which is in the range of 0.5-2.4 μm.

Terpolymer-Based Anion Exchange Membranes: Effect of Pendent Hexyl Groups on Membranes Properties

Abstract In the pursuit of better functioning anion exchange membranes, pendent hexyl side chains were introduced onto terpolymers composed of perfluorohexylene (PHB), hexafluoroisopylidene (BAF), and quaternized fluorene groups. The resulting QBPHBA membranes exhibited similar water absorbability and gas (hydrogen and oxygen) permeability to those of the previous terpolymer-based AEMs without aliphatic side chains. In contrast, hexyl groups contributed to improving the OH− conductivity. The highest OH− conductivity (163 mS cm−1 at 80 °C) was achieved with the QBPHBA membrane with 2.49 meq. g−1 of ion exchange capacity (IEC). Furthermore, mechanical properties were also improved; the strain at break increased from 12% (BAF-containing copolymer membrane) to 284%. The terpolymer composition for the best-balanced properties turned out to be 17 mol% of the side-chain substituted PHB groups, in particular, with high IEC (2.49 meq. g−1).

Copper-catalyzed oxidative dehydrogenative dearomatization of indole derivatives: A new strategy to construct spirocyclic indolenines.

A concise copper-catalyzed oxidative dehydrogenative dearomatization of indole derivatives for the direct synthesis of spirocyclic indolenines containing fluorene and indeno[2,1-b]indole groups has been established. The utility of this method has also been successfully accomplished by dual oxidative dehydrogenative dearomatization to deliver the desired spirocyclic indolenines containing fluorene groups. According to mechanistic analyses, the C-H cleavage of the phenyl ring was not implicated in the rate-limiting phase. This transformation underwent a single-electron-transfer oxidation by copper(II) catalyst to afford a radical-cation intermediate, yielding the final product by nucleophilic attack and dual deprotonation.

Retraction Note to: Synthesis and characterization of a novel sulfonated poly (aryl ether ketone sulfone) containing rigid fluorene group for DMFCs applications

Retraction Note to: Synthesis and characterization of a novel sulfonated poly (aryl ether ketone sulfone) containing rigid fluorene group for DMFCs applications

Slowing crystallization to enhance interlayer strength of 3D printed poly (ether ether ketone) parts by molecular design

The major challenge restricting the application of 3D printed PEEK parts is the weak interlayer strength. Herein, the fluorene-based poly (ether ether ketone)s (FD-PEEK) were designed and synthesized to solve the problem. A remarkable improvement in the interlayer strength of materials was achieved. By introducing 10 mol% fluorene groups into the polymer chain (10 %-FD-PEEK), the interlayer strength of 10 %-FD-PEEK was improved to 41 MPa, which is close to that of the commercial PEEK resin for 3D printing (Victrex, AM 200). The introduction of 15 mol% fluorene groups (15 %-FD-PEEK) enabled the interlayer strength and strain at break of 400 % and 500 % higher than that of PEEK, reaching 67 MPa and 11.23 %, respectively. The improvement of the interlayer strength was attributed to the slower crystallizing rate of FD-PEEK, which was verified by the isothermal and non-isothermal crystallization kinetics. Meanwhile, the chain rigidity caused by fluorene groups and the larger spherulite generated by the slower crystallization allowed FD-PEEK to reach a similar tensile strength to PEEK in the X-axis and Y-axis directions. Achieved by slowing crystallization and introducing rigid structure into the molecular chain, the results significantly promote the engineering application of 3D printing parts and provide new insights into the performance enhancement of semi-crystalline additive manufacturing materials.

Robust poly(alkyl–fluorene isatin) proton exchange membranes grafted with pendant sulfonate groups for proton exchange membrane fuel cells

The development of high-performance low-cost membrane materials is crucial for application in proton exchange membrane fuel cells (PEMFCs). In this study, two types of poly(alkyl–fluorene isatin)-based proton exchange membranes (PEMs) are designed and prepared successfully via facial superacid-catalyzed Friedel–Crafts polycondensation. The fluorene-based polymers exhibit good solubility and film-forming ability, and the produced PEMs possess excellent mechanical properties, dimensional stability, and oxidization stability because of the aromatic backbone. Atomic force microscopy showed that HFxDPy-PS-based PEMs have more significant phase separation structures than MFxDPy-PS-based PEMs due to the longer soft alkyl chains on the fluorene groups. HF3DP1-PS exhibits high proton conductivity that reached 88.56 mS cm−1 at 80 °C. The H2/O2 single fuel cell assembled with HF3DP1-PS exhibits a power density of 753 mW cm−2, which is close to that of a fuel cell with commercial Nafion 212 (774 mW cm−2) under the same conditions. All these results indicate the broad potential application of poly(alkyl–fluorene isatin)-based PEMs in PEMFCs.

Chemical structure-based design of triboelectric materials for high-performance TENGs

Triboelectric nanogenerator (TENG) has attracted much interest due to its efficiency, flexibility and cost-effectiveness to harvest wasted mechanical energy. However, the relationship between the chemical composition and output performance of triboelectric materials is still not completely revealed. As an attempt to understand the structure-performance relationship at the molecular level, representative fluorinated poly (arylene ether)s with varying content of electron-donating groups (fluorene groups) in the backbone are synthesized and compared in the performance of TENGs. The structure-dependent performance of triboelectric materials in TENGs is closely related to the potential energy difference (∆E) between the HOMO energy level of the positive material and the LUMO energy level of the negative material. With an introduction of 50 mol% fluorene groups and the smaller ∆E, the fluorinated poly (arylene ether) (DFAFW50) contacting with PEEK provides the best output performance of the TENG, and remains stable output performance in 120,000 cycles. For fluorinated poly (arylene ether)s, the introduction of electron-donating groups makes materials tend to lose electrons. Within this effort, a potential molecular design protocol is proposed to develop high-performance positive and negative triboelectric materials applicable in TENGs.