Thermally Stable Blue-Light-Emitting Copolymers of Poly(alkylfluorene)

Polyfluorene-poly(ethylene oxide) diblock copolymers: synthesis and electron transport behavior

Under mild reaction conditions, we synthesized diblock copolymers of poly(9,9-dioctylfluorene)-block-poly(ethylene oxide) (PFO-b-PEO) via end-capping poly(9,9-dioctylfluorene) (PFO) with poly(ethylene oxide) (PEO) on one end. We investigated the thermal, optical, electrochemical and crystalline properties as well as electron transport performance of these polymers. Our results demonstrate that PFO-b-PEO diblock copolymers with short PEO chains (M n = 1000 and 2000 g mol-1) exhibit higher electron mobilities compared to the PFO homopolymer and longer PEO chain (M n = 4000 g mol-1) attached copolymers. This enhanced electron mobility is attributed to the higher crystallinity induced by the shorter PEO chain end-capping.

Synthesis, Self-assembly, and Fluorescence Application of Bottlebrush Polyfluorene-g-Polycaprolactone with Conjugated Backbone and Crystalline Brushes

A series of bottlebrush copolymers with conjugated backbone and crystalline branch chains, polyfluorene-g-polycaprolactone (PF-g-PCL), are synthesized by combining Suzuki cross-coupling polymerization and cationic ring-opening polymerization. The PF-g-PCLs are prepared to self-assembled in solution and thin film. Due to the J-type aggregation of the polyfluorene main chains, the self-assembly spherical micelles have been observed. Meanwhile, in film, they exhibited self-assembly ringed spherulites because of the PF microregions in the bottlebrush copolymer. As a result of the interruption of PCL side chains, the aggregation tendency of PF main chains is weakened. And both the polymer solution and solid can overcome the aggregation-caused quenching to provide more pronounced fluorescence. Especially, owing to the good processability of the PF-g-PCL, as a fluorescent ink for different substrates, they can easily be prepared as high-brightness fluorescent films that are invisible under ambient light.

Palladium-catalyzed carbene coupling of N-tosylhydrazones and arylbromides to synthesize cross-conjugated polymers

Palladium-catalyzed cross-coupling reactions of N-tosylhydrazones and arylbromides have been applied for the first time in the synthesis of cross-conjugated polymers, namely poly(arylene-1,1-vinylidene)s (iso-PAVs).

Rodlike Tetracene Derivatives

Efficient and versatile synthetic access to rodlike tetracene derivatives was developed by means of Diels-Alder cycloaddition, halogenation, halogen-metal exchange, and transition metal mediated coupling reactions. Herein, the synthesis and structural, electrical, and charge-transport properties of three of the resulting materials, namely, 2-(tetracen-2-yl)tetracene, 1,4-bis(2-tetracenyl)benzene, and 2,5-bis(2-tetracenyl)thiophene, are presented. Good crystallization behavior on SiO₂ substrates, narrowing of the bandgap by 0.2 eV, and a decrease of the ionization potential of more than 0.5 eV compared to tetracene were observed. Charge-carrier field-effect mobilities on the order of 10^-1  cm²  V^-1  s^-1 , on/off ratios of 10⁵ , and threshold voltages V_th <15 V were found in thin-film organic field-effect transistors prepared by standard high-vacuum deposition techniques.

Influence of side chains on the self-alignment capability of electroluminescent polyfluorenes

We report a significant role of side chains in the propagation of molecular orientation upon annealing the liquid crystal phase of polyfluorenes. Direct rubbing of poly(9,9-di(octyl)fluorene) led to the orientation of polymer segments in the top-most region of the film and enhanced propagation of this orientation along the rubbing direction was observed upon annealing. In contrast, the rubbing-induced molecular orientation of poly(9,9-di(ethylhexyl)fluorene) segments completely disappeared upon annealing in the nematic melt state. The higher order of the side chain structures in poly(9,9-di(octyl)fluorene) were found to allow the propagation of the three-dimensional molecular alignment. From integrated experimental and density functional theory studies, we propose that side chain interdigitation generates a unique alignment behavior of poly(9,9-di(octyl)fluorene).

Rod–coil type miktoarm star copolymers consisting of polyfluorene and polylactide: precise synthesis and structure–morphology relationship

Rod–coil type miktoarm star copolymers consisting of PF and PLA have been precisely synthesized for investigating the effect of macromolecular architecture on self-assembled nanostructures.

All-organic optoelectronic sensor for pulse oximetry

Pulse oximetry is a ubiquitous non-invasive medical sensing method for measuring pulse rate and arterial blood oxygenation. Conventional pulse oximeters use expensive optoelectronic components that restrict sensing locations to finger tips or ear lobes due to their rigid form and area-scaling complexity. In this work, we report a pulse oximeter sensor based on organic materials, which are compatible with flexible substrates. Green (532 nm) and red (626 nm) organic light-emitting diodes (OLEDs) are used with an organic photodiode (OPD) sensitive at the aforementioned wavelengths. The sensor's active layers are deposited from solution-processed materials via spin-coating and printing techniques. The all-organic optoelectronic oximeter sensor is interfaced with conventional electronics at 1 kHz and the acquired pulse rate and oxygenation are calibrated and compared with a commercially available oximeter. The organic sensor accurately measures pulse rate and oxygenation with errors of 1% and 2%, respectively.

Synthesis and chemosensory application of water-soluble polyfluorenes containing carboxylated groups

Detection of metal ions in aqueous solutions is a major issue for environmental protection. Conjugated polyelectrolytes showing high sensitivity and selectivity towards the detection of metal ions are highly desirable. We report a water-soluble polyfluorene containing carboxylated groups (P1), poly[9,9'-bis(3''-propanoate)fluoren-2,7-yl] sodium salt, which shows high recognition capability toward Cu(+) and Cu(2+). P1 was prepared via the hydrolysis of poly[9,9'-bis(tert-butyl-3''-propanoate)fluoren-2,7-yl] (P0) which was synthesized by Suzuki coupling polymerization. The photoluminescence (PL) spectra of P1 in aqueous solution are significantly quenched in the presence of Cu(+) and Cu(2+). P1 shows high selectivity and sensitivity toward Cu(+) and Cu(2+), with the Stern-Volmer constants (Ksv) being 3.5 × 10(6) and 5.78 × 10(6) M(-1), respectively. Moreover, the stoichiometric ratio of the P1 repeat unit to Cu(+) or Cu(2+) is 2 : 1 obtained from Job's plot. P1 maintains high selectivity towards Cu(+) or Cu(2+) in the presence of various metal cations. Our results demonstrate that P1 shows very high sensitivity and selectivity in recognizing Cu(+) and Cu(2+), indicating that it is a promising functional material for chemical sensors.

H-shaped oligofluorenes for highly air-stable and low-threshold non-doped deep blue lasing

H-shaped oligofluorenes as gain media exhibit excellent photo- (large robustness against oxidation) and thermal stabilities in ambient atmosphere for large σe and low-threshold (0.22 nJ pulse(-1) ) deep blue distributed feedback (DFB) lasers. Their amplified spontaneous emission (ASE) thresholds increase less than 3-fold and the emission spectra exhibit almost no shift with film samples annealed up to 200 °C in open air.

Solution-processable hole-transporting material containing fluorenyl core and triple-carbazolyl terminals: synthesis and application to enhancement of electroluminescence

A novel solution-processable, efficient hole-transporting material 2,4,7-tri[2-(9-hexylcarbazole)ethenyl]-9,9-dihexylfluorene (FC), composed of a fluorenyl core and triple-carbazolyl terminals, is successfully synthesized and well characterized. The FC is a thermally stable, amorphous material because of its aromatic and asymmetric structure. The highest occupied molecular orbital (HOMO) level of FC is -5.21 eV, as determined by cyclic voltammetry, implying its applicability as a hole-transporting layer (HTL) to promote hole injection. Furthermore, the FC could be deposited by a spin-coating process to obtain a homogeneous HTL film, more convenient and cost-effective than conventional NPB which must be deposited by vacuum vapor deposition. When fabricated as multi-layer OLED [ITO/PEDOT:PSS/HTL(25 nm)/Alq3(50 nm)/LiF(0.5 nm)/Al(100 nm)], the maximum brightness (21,400 cd m(-2)) and current efficiency (3.20 cd A(-1)) based on the FC are superior to those using conventional NPB as the hole-transporting layer. In addition, a homogeneous FC film is readily prepared by simple wet processes (spin-coating). Our results indicate that the FC is a promising optoelectronic material which is readily processed by wet methods such as spin-coating.

Suzuki Polycondensation: Polyarylenes à la Carte

This review draws a rather comprehensive picture of how Suzuki polycondensation was discovered in 1989 and how it was subsequently developed into the most powerful polymerization method for polyarylenes during the last 20 years. It combines insights into synthetic issues with classes of polymers prepared and touches upon aspects of this method's technological importance. Because a significant part of the developmental work was carried out in industry, the present review makes reference to an unusually large number of patents.

3-(9H-Fluoren-9-yl)-1,3-diphenyl-propan-1-one

In the title compound, C₂₈H₂₂O, the fluorene ring system is approximately planar [maximum deviation = 0.044 (2) Å] and forms dihedral angles of 69.88 (6) and 89.46 (6)° with the phenyl rings. The crystal packing is stabilized by weak π–π stacking inter­actions, with centroid–centroid distances of 3.7172 (13) and 3.7827 (11) Å.

3-(9H-Fluoren-9-yl)-3-(4-methyl-phen-yl)-1-phenyl-propan-1-one

In the title compound, C₂₉H₂₄O, the phenyl and methyl­phenyl rings are approximately perpendicular to each other, making a dihedral angle of 87.67 (10)°, and are oriented at dihedral angles of 62.49 (9) and 84.77 (7)°, respectively, to the nearly planar fluorene ring system [maximum deviation = 0.077 (2) Å] In the crystal, weak C—H⋯π inter­actions are observed.

Band Gap and HOMO Level Control in Poly(thienylene vinylene)s Prepared by ADMET Polymerization

Three dipropenyl monomers were prepared for ruthenium-catalyzed acyclic diene metathesis (ADMET) polymerization. Homopolymerization afforded three poly(thienylene vinylene)s (PTVs) with distinct optoelectronic properties. Binary combinations of the monomers over a range of compositions gave three series of copolymer samples with tunable HOMO levels and band gaps. The utility of this method was further demonstrated by the preparation of a stoichiometric terpolymer. Polymers were characterized by ¹H NMR spectroscopy, size-exclusion chromatography, ultraviolet-visible spectroscopy, and cyclic voltammetry. This copolymerization approach effectively demonstrates the ability of ADMET polymerization to prepare conjugated copolymers with tuned optoelectronic properties that span a broad composition window.