Summary: Two types of bis(2,5‐diphenyl‐1,3,4‐oxadiazole)s, macrocyclic and acyclic, were prepared and evaluated as electron‐transporting and hole‐blocking materials in phosphorescent EL devices. Maximum efficiencies of ηext = 10.4% at J = 0.11 mA · cm−2 for the macrocycle and ηext = 14.1% at J = 3.01 mA · cm−2 for the acycle were observed. X‐ray crystallographic analysis and DSC measurements revealed a strong intermolecular interaction between the macrocycles and weaker intermolecular interactions between the acycles. The EL characteristics depend on the intermolecular interactions.
The two types of bis(2,5‐diphenyl‐1,3,4‐oxadiazole)s used in the study. 相似文献
We synthesized a series of polystyrene derivatives containing coumarin side groups using polymer analogous reactions. The liquid‐crystal (LC) alignment director for these polymer films was found to be perpendicular to the rubbing direction. The contrast ratio and anchoring‐energy values of these polystyrene derivatives were found to be much greater than those of polystyrene and poly(chloromethylstyrene), indicating that the coumarin side groups increase the aligning ability. For example, the anchoring energy of a polymer with 82 mol‐% of coumarin‐containing monomeric units, compared to polystyrene, is about 7 × 10?5 J · m?2 and 1 × 10?7 J · m?2, respectively.
Benzo[1,2‐b:4,5‐b′]diselenophene (BDS) has been incorporated for the first time in a polymer. bis(Stannyl)‐functionalized BDS was copolymerized with 3,3′‐bis(alkyl)‐5,5′‐bithiophenes (dodecyl and tetradecyl side chains) through Stille copolymerization, to yield p‐type polymer semiconductors for organic field‐effect transistor application. The electronic and structural effect of the selenium atoms, compared to sulphur atoms in analogous copolymers, is described. The molecular weight has a decisive influence on the photophysical properties and supramolecular ordering, expressed in field‐effect transistor measurements. Saturation mobilities around 10?2 cm2 · V?1s?1 are obtained on standard silicon substrates.
Synthesis and characterization of a series of PAEs containing DPP units in the main chain are described. of the polymers was in the range 10 800–111 900. The polymers formed a deep blue solution in chloroform with absorption maxima between 589 and 645 nm and optical band gaps ranging from 1.61 to 1.74 eV. When excited at the absorption maxima, the polymer solutions showed red fluorescence with emission maxima between 656 and 676 nm. The polymers exhibited quasi‐reversible oxidation process with HOMO energy levels between ?5.60 and ?6.17 eV. EL properties of three polymers were investigated with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. When appropriate bias voltage was applied, a red EL with a maximum brightness of 17.5–24 cd · m?2 could observe from the devices.
Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.
A series of three recently synthesised tetradentate chelated α‐diimine nickel complexes of the type [NiBr2(Ar‐BIAN)] (where Ar = 2‐(1‐R‐1H‐1,2,3‐triazol‐4‐yl)phenyl; R = benzyl 1 , 1‐phenylethyl 2 , phenyl 3 ) are used as precatalysts for the polymerisation of norbornene. When activated with MAO, 1 – 3 are highly active catalysts for the production of high molecular weight polynorbornene (e.g., 1.39 × 107 g PNB mol Ni?1 · h?1). The catalytic activity and polymer molecular weight increase markedly with the initial concentration of norbornene, but both parameters decrease with the reaction time. The characterisation of the polynorbornenes by NMR, GPC/SEC, X‐ray diffraction, and DSC/TGA leads to the assignment of a structure typical of a polynorbornene originated by a coordination vinyl addition mechanism.
A copolymer of 2,3,5,6‐tetrafluoro‐1,4‐phenylenevinylene and 2,5‐dioctyloxy‐1,4‐phenylenevinylene [co(TFPV‐DOPV)], containing more than 60% of tetrafluorophenylenevinylene monomeric units, was synthesized by the Stille cross‐coupling reaction. Its linear and nonlinear optical properties were investigated. Linear absorption and photoluminescence measurements performed on thin films and solution indicate interchain migration upon excitation. The Z‐scan technique was used to evaluate the third‐order nonlinear susceptibility at λ = 1064 nm. A very high refractive nonlinearity (n2 = (?10 ± 2) × 10?12 cm2 · W?1) was measured with a value one order of magnitude larger than that of the corresponding dialkoxy‐substituted homopolymer.
A silicone‐based radical polymer 2 was synthesized by hydrosilylation of PMHS with 4‐allyl‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl ether 1 in the presence of a platinum‐ or rhodium‐catalyst. A reversible redox peak of 2 at 3.56 V (vs. Li/Li+) was observed by CV measurements. A coin‐shaped cell of 2 shows a discharge capacity of 46 mAh · g?1, which is 47% of the theoretical capacity of 2 (98 mAh · g?1). A directly TEMPO‐substituted silicone, poly[methyl(2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐4‐oxyl)siloxane] 3 was also obtained by rhodium‐catalyzed dehydrogenative alcoholysis of PMHS with TEMPO‐OH. The coin‐shaped cell of 3 shows a discharge capacity of 80 mAh · g?1, which is 69% of the theoretical capacity of 3 (116 mAh · g?1).
Cross‐linked poly(3,4‐ethylenedioxythiophene) (PEDOT) films were synthesized by the oxidative polymerization of 3,4‐ethylenedioxythiophene in the presence of five different conjugated and non‐conjugated cross‐linkers. The concentration and structure of the cross‐linker was systematically varied to explore the influence on the electrical conductivity. Optimized compositions displayed an electrical conductivity of up to ≈800 S · cm?1; this corresponds to a conductivity increase of up to 36% compared to linear PEDOT prepared under identical conditions. An increase in the conductivity was only observed for the conjugated cross‐linkers that were incorporated in low concentrations, typically at a level of less than 2 mol‐%. Attempts to incorporate higher concentrations of cross‐linker led to phase separation and crystallization of the cross‐linker and afforded materials in which a significant reduction of the electrical conductivity was observed. The optical properties of the polymer were only marginally affected upon cross‐linking, even at high cross‐linker concentrations.
Crystallization kinetics of the biodegradable and fast crystallizing poly(butylene succinate) is studied, under both isothermal and non‐isothermal conditions. For the isothermal process at temperatures from 75 to 95 °C it is found that the Avrami model successfully describes the transformation kinetics. The non‐isothermal crystallization data obtained at a wide range of cooling rates from 0.1 to 20 °C · min?1 are treated with several models, which include the modified Avrami, the Ozawa, the combined Avrami‐Ozawa, and the Tobin model. The Lauritzen‐Hoffman parameters are estimated from isothermal and non‐isothermal differential scanning calorimetry data, using different approximations for the growth rate and from the effective activation energy equation proposed by Vyazovkin and Sbirrazzuoli. The multiple‐melting behavior has been interpreted in the context of the melting–recrystallization–remelting phenomena.
A microwave‐assisted method of synthesizing high‐molecular‐weight PLA using SSA as green catalyst was developed. Yellowish PLA with above 2.0 × 104 g · mol?1 was obtained when the reaction was run at 260 °C within 60 min under microwave irradiation with 0.4 wt.‐% SSA. This method used only 10% of the energy consumption necessary for conventional heating, and the catalyst could be used five times without losing catalytic activity. The improvement in and the decrease in the energy consumption under microwave irradiation suggested that selective heating and hot spots effects played a crucial role. The method was shown to be a time‐saving, green and a promising way to lower the cost and spread the application of PLA.
Two oligo‐(aryleneethynylene)s, with coplanarity of main chain and tetrathiafulvalene (TTF) side chains, have been prepared and characterized. The X‐ray diffractions (XRDs) show that their π‐extended coplanar backbones can form continuous π‐stacking. For the two oligomers, one stacks in the inter‐digitation packing mode; another stacks in the end‐to‐end packing mode. Cyclic voltammetries reveal that the two oligomers have almost the same reversible electroactive properties. The TTF units of the two oligomers can be oxidized to TTF . 1+ by Fe(bpy)3(PF6)3 (bpy = 2,2′‐bipyridine). The band gaps, deduced from UV‐Vis absorption spectra, are 1.92 and 2.03 eV, respectively. The conductivities of the two oligomers are 1 × 10?5 and 6 × 10?8 S · cm?1 at room temperature. The charge transfer (CT) complexes of the oligomers and tetracyanoquinodimethane (TCNQ) exhibit higher conductivity up to 0.2 S · cm?1.
A new solution‐processable bipolar dendrimer with carbazole units as hole‐transporting units and oxadiazole units as electron‐transporting units was efficiently synthesized based on a convergent approach by alternation of a Cu‐catalyzed azide/alkyne cycloaddition reaction and Williamson ether synthesis. The orthogonal chemistry completely avoided protection and activation of the focal points in the process of dendrimer synthesis. The dendrimer showed a wide bandgap and good thermal stability. Electrophosphorescent devices with the configuration ITO/PEDOT:PSS/bipolar dendrimer:Ir(ppy)3/TPBI/LiF/Al were fabricated. The devices showed a maximum current efficiency of 16.8 cd · A?1, a maximum power efficiency of 4.22 lm · W?1 and an external quantum efficiency of 5.7%.
pH‐sensitive micelles formed by interchain hydrogen bonding of poly(methacrylic acid)‐block‐poly(ethylene oxide) copolymers were prepared and investigated at pH < 5. Both and Rh of the micelles increase with decreasing pH of the solution, displaying an asymptotic tendency at low pH values. The observed micelles are well‐defined nanoparticles with narrow size distributions (polydispersity ΔRh/Rh ≤ 0.05) comparable with regular diblock copolymer micelles. The CMCs occur slightly below c = 1 × 10?4 g · mL?1. The micelles are negatively charged and their time stability is lower than that of regular copolymer micelles based purely on hydrophobic interactions.
Ring polymers are synthesized using a cyclic bifunctional thioester as initiator for REP of thiiranes. PMT yields satisfactory results, whereas polymerization with MT appears to develop dead polymeric material as by‐product and TBMT gives only negligible conversion rates. The process produces high yields and high conversion rates. The corresponding molecular weight distributions show increasing broadening and multimodal character with increasing reaction time due to thermodynamically controlled ring‐merging reactions between macrocycles. The polymerization rate of PMT obeys a pseudo first‐order kinetics with an activation energy of 38.8 kJ mol?1. 1H NMR, ESI‐MS, and glass transition temperatures independent of the molecular weight demonstrate the presence of cyclic polymer.
Needle‐like poly(aniline p‐toluenesulfonic acid) complex aggregates were synthesized by oxidative polymerization, yielding conductivities of up to 3 S · cm?1 and maximum aspect ratios of 26. Rod‐like aggregates as precursors to be developed into needle‐like aggregates were obtained with 1 to 2 h APS addition time at 15 °C. Flake‐like polyanilines were prepared at ?2 or +20 °C with 1.9 to 2.5 h of APS addition time, giving aspect ratios of 2 to 10. Plate‐like polyaniline aggregates emerged when xylene was added, and an optimum xylene concentration was 15 vol.‐%, giving 1.3 S · cm?1 conductivity. The polyanilines were characterized by optical microscopy, SEM and UV‐vis/NIR spectroscopy.
Novel polymer electrolyte materials based on a polyelectrolyte‐in‐ionic‐liquid principle are described. A combination of a lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSLi) and N,N′‐dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (≥ 2 · 10?2 S · cm?1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol‐% in the copolymer (P(AMPSLi‐co‐DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10 ? 15 wt.‐% of total polyelectrolyte. Conductivities higher than 8 · 10?3 S · cm?1 at 30 °C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques.
Comparison of the measured and calculated lithium conductivity at 30 °C. 相似文献
Cyclopentyl‐ and cyclohexyl‐substituted polysiloxanes terminated with amino groups were prepared. Initially, the cycloalkene and dichlorosilane were reacted at high pressure (approx. 250 psi) and high temperature (120 °C) to yield the cycloaliphatic dichlorosilane in a two‐step process. Both the mono‐ and disubstituted chlorosilane monomers underwent an oligomerization to produce cyclic oligomers of low molecular weight (≈2 000 g · mol?1). Amine‐terminated polysiloxanes were produced via a base‐catalyzed ring‐opening polymerization of the cyclic oligomers with 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane to yield low molecular weight polysiloxanes (≈9 000 g · mol?1, amine equivalent weight = ≈4 300 g · equiv.?1). The polysiloxanes were characterized by 1H and 29Si NMR, and Fourier transform‐infrared spectroscopy (FT‐IR). The amine‐terminated polysiloxane was mixed with a cycloaliphatic epoxy‐functionalized cycloaliphatic polysiloxane in order to produce crosslinked epoxy–amine films. The mechanical and physical properties of the film were evaluated and afford a glass transition of the material was 29.5 ± 0.7 °C for the cyclopentyl‐substituted polysiloxane and 38.6 ± 0.7 °C for the cyclohexyl‐substituted polysiloxane. Evaluation of pull‐off adhesion indicated that 0.5 MPa of normal force was required to remove the epoxy/amine film from an aluminum substrate.
Multiarm PEO star polymers with a purely aliphatic polyether structure have been synthesized using hyperbranched polyglycerol (PG) with different molecular weights as a multifunctional initiator. Different degrees of deprotonation of the initiator were studied with respect to molecular weight control. The results show that the degree of deprotonation is a crucial parameter for the synthesis of well‐defined polymers with controlled molecular weights. Partial deprotonation of the PG hydroxyl groups (5–8%) was proven to represent an optimum for the synthesis of star polymers with molecular masses close to the theoretical values. Molecular weights of the stars ranged between 9 000 and 30 000 g · mol?1. MALDI‐ToF spectra confirmed that the PEO arms in the star polymers possess homogeneous lengths.
Summary: Soluble conjugated random and alternating copolymers (PCz‐PSP) derived from N‐hexyl‐3,6‐carbazole (Cz) and 1,1‐dimethyl‐2,3,4,5‐tetraphenylsilole (PSP) were synthesized by palladium(0)‐catalyzed Suzuki coupling reactions. The feed ratios of Cz to PSP were 95:5, 90:10, 80:20, 70:30, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by 1H NMR, 13C NMR, UV absorption, cyclic voltammetry, photoluminescence, electroluminescence, and field effect transistor. HOMO levels of the copolymers are between −5.15 and −5.34 eV. Single‐layer devices with a configuration of ITO/copolymer/Ba/Al were fabricated and the copolymer with PSP content of 20% displayed the highest external quantum efficiency of 0.77%. Field effect transistors with tantalum pentoxide‐polyacrylonitrile double insulators demonstrated that hole mobilities of the copolymers decreased with their PSP contents, and the hole mobility up to 9.3 × 10−6 cm2 · (V · s)−1 could be achieved.
Synthesis of coplymers derived from 3,6‐carbazole and silole. 相似文献
