Summary: Solid‐state olefin metathesis of rigid‐rod acyclic diene metathesis (ADMET) polymers and ring‐closing metathesis (RCM) have been investigated. 1,4‐Dipropoxy‐2,5‐divinylbenzene ( 4 ) was synthesized and used in a bulk ADMET polymerization to produce oligomers of dialkoxy poly(phenylene vinylene). The reaction was continued in the solid state, effectively doubling the molecular weight. Solid‐state RCM was investigated with a variety of solid dienes and metathesis catalysts, and demonstrated in low conversions using amide diene 5 with catalysts 9 , 13 , and 14 .
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 synthetic route that allows modification of 1‐vinyl‐2‐pyrrolidone with an alcohol or thiol group in its 3‐position in a one‐pot reaction without using protecting groups is described. The strategy used to achieve this goal is the reaction of the carboxamide anion of 1‐vinyl‐2‐pyrrolidone with cyclic precursors of these functionalities. It is furthermore shown that VP‐monomers functionalized with OH groups are suitable for the preparation of the corresponding copolymers with pure VP. As a second application of the new compounds, we also describe the synthesis of the first asymmetric crosslinker based on VP.
Zirconium pyrophosphate (ZPP)/poly(2,5‐benzimidazole) composites were prepared by polymerization of 3,4‐diaminobenzoic acid with zirconium hydrogen phosphate in polyphosphoric acid. The composite membranes for polymer electrolyte membranes were prepared by casting the polymerization solutions directly onto stainless steel plates. Membranes doped in 60 wt.‐% phosphoric acid solution had high proton conductivity values of more than 0.12 S · cm?1 (at 180 °C and 1% RH). Physical properties of the doped membranes, including the mechanical strength and dimensional stability, improved as ZPP content in the composites increased to 10–20 wt.‐%.
The optimization of photorefractivity (PR) based on a poly(N‐vinylcarbazole) (PVCz) composite devise is proposed from the perspectives of chemistry and physics. The device's PR chemistry (dependence of PVCz's molecular weight) and physics (dependence of grating periodicity and laser wavelength) are studied. Increasing the molecular weight of PVCz from 23 000 to 1 270 000 g mol?1 significantly increases diffraction efficiency, grating build‐up speed (inverse of response time), and sensitivity. Narrowing grating period from 5.1 to 1.1 μm gives faster response time and larger optical gain. Shorter wavelength of writing laser from 633 to 532 nm provides higher diffraction efficiency, faster response time, and larger optical gain.
PEDOT is one of the most frequently studied conducting polymers in literature but values for optical transmission and electrical conductivity vary greatly. Therefore measurement protocols are examined and insights are suggested into why the protocols themselves may lead to differences. Reported PEDOT conductivity is the result of contact and non‐contact film thickness and four‐point probe measurements. The soft nature of PEDOT implies that any contact method must be executed with extreme care as values of conductivity ranging from 780 to 2 775 S · cm?1 can be obtained. Similarly, variations in the optical minimum, maximum, and transmission range are found based on different switching voltage protocols. The results present here highlight the need for explicitly stating the measurement protocol used.
Summary: Stable free‐radical copolymerizations (SFRP) of styrene with N‐acryloyl morpholine (AMo), 2‐ethoxyethyl acrylate (EOEA) and isobornyl acrylate (iBoA), respectively, were carried out under control of the stable nitroxide radical 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (OH‐TEMPO). The polymerizations were initiated by a polystyrene macroinitiator (PS‐MI). No accelerating agents were used. In contrast to the experiences made with methacrylates there was no decrease in the polymerization rates up to 50 mol‐% of AMo or EOEA in the monomer mixture. This behavior was ascribed to a compensation of the lack of thermal initiation by the high propagation rate constants of the acrylates. The produced AB diblock polymers were successfully employed in block extension reactions in styrene yielding ABA triblock polymers. Copolymerization reactivity ratios (r‐values) and glass transition temperatures have been estimated.
A series of π‐conjugated alternating copolymers consisting of Th‐ITN‐Th and p‐C6H2(OR)2 units were synthesized. XRD indicated that the copolymers assume an interdigitation packing mode, and UV‐Vis spectra revealed a strong tendency for self‐assembly. Upon molecular assembly of the copolymer, the UV‐Vis absorption shifted by about 100 nm to a longer wavelength from that of the single molecule. The copolymers underwent electrochemical oxidation (or p‐doping) and reduction (or n‐doping) at 0.2 and ?2.0 V versus Ag+/Ag, respectively. A p‐doped copolymer film showed an electrical conductivity of 182 S · cm?1, and the temperature dependence of electrical conductivity was measured. The copolymer showed piezochromism and served as a p‐channel material for a field‐effect transistor.
The present paper reports the synthesis of π‐conjugated organometallic polymer networks based on poly[2,5‐dioctyloxy‐1,4‐diethynyl‐phenylene‐alt‐2,5,‐bis(2′‐ethylhexyloxy)‐1,4‐phenylene] (EHO‐OPPE), a soluble poly(p‐phenylene ethynylene) (PPE) derivative. The ethynylene moieties of the polymer coordinate to Pt0 centers, which act as conjugated cross‐links. These materials are readily accessible through ligand‐exchange reactions between the linear PPE and Pt(styrene)3. The in‐situ NMR investigation of model reactions of Pt(styrene)3 with diphenylacetylene (DPA) has shown that the ethynylene moieties comprised in the PPE readily coordinate to Pt0 centers under release of the relatively weakly‐bound styrene ligands. Spin‐coating has resulted in cross‐linked films of good optical quality. We also have been able to produce PPE‐Pt‐gels with high solvent content (> 95 wt.‐%). As expected, the coordination of Pt markedly influences the photophysical characteristics of the PPE. The photoluminescence is efficiently quenched, and the absorption maximum in the visible regime experiences a hypsochromic shift.
Ligand‐exchange reaction between EHO‐OPPE and [Pt(PhCH?CH2)3] leading to the target EHO‐OPPE‐Pt0 networks. 相似文献
By suspension polymerization using styrene, divinylbenzene, and synthetic poly(ethylene glycol) (PEG) macromonomers, we have prepared core–shell‐type resins that have a highly crosslinked polystyrene core and a PEG shell. The PEG macromonomer, which has a vinyl group and an amino group at each terminal, plays a role as a stabilizer in the suspension polymerization system. All the resins were of the bead type with a diameter of 38–150 μm. The loading capacities of the amino groups were 0.1–0.2 mmol · (g resin)−1 and the thickness of the PEG shell 2–4 μm, which was verified by cross‐sectioned views of the fluorescamine‐coupled beads. During coupling of amino acids in solid‐phase peptide synthesis, the resin showed better yields than TentaGel resin, especially during the first coupling step. In the enzymatic cleavage reaction, the resin‐bound peptides were shaved about 5–10 times more than TentaGel resin.
Low band‐gap conjugated polymers based on naphthalene bisimide (NBI) and 3,4‐ethylenedioxythiophene (EDOT) were synthesized by Stille cross‐coupling reaction. The alternating conjugated poly(EDOT‐NBI) ( P1 ) and random poly(EDOT‐NBI) ( P2 ) are both solution‐processable due to the existence of bulky 2,6‐diisopropylphenyl substituent. Their optical and electrochemical properties were characterized. P1 and P2 films show optical band gaps of 1.75 and 1.38 eV estimated from UV‐Vis absorption spectra. Cyclic voltammograms of both polymers display reversible reduction peaks with onset reduction potentials at ?0.55 V for P1 and ?0.61 V for P2 , which correspond to the electron affinity (EA) values (LUMO energy level) of 3.85 and 3.79 eV, respectively. The ionization potential (IP, HOMO level) values of 5.60 eV for P1 and 5.17 eV for P2 were also calculated by combining solid‐state optical and electrochemical data. A double heterojunction device was fabricated. It exhibits an open circuit voltage of 0.30 V and average power conversion efficiency of 0.15%.
Summary: This paper describes the use of trialkylsilanes for photoinduced patterning of electroluminescent polymers as a new field of application for this type of organosilicon compounds. Under UV irradiation, trialkylsilanes selectively saturate the vinylene groups in poly(p‐phenylenevinylene) (PPV)‐type polymers, while leaving aromatic units virtually unaffected (selective photobleaching). Spin cast films of polymer blends consisting of two or three different conjugated polymers were UV irradiated in the presence of gaseous trialkylsilane reagents (trimethylsilane and ethyldimethylsilane) to achieve multicolor patterning. Exploiting the host‐guest concept with polyfluorene (PF) derivatives as totally aromatic host matrix and PPV derivatives as guest polymers, dual‐color displays and, with constraints, three‐color LED displays were realized. Compared to previously reported reagents such as hydrazine and thiols, trialkylsilanes enable photochemical patterning under non‐toxic and odorless conditions. Possible mechanisms for the photoreaction with trialkylsilanes as well as perspectives for applications are discussed.
Electroluminescence spectra of LEDs based on the host‐guest system. 相似文献
This paper describes a novel spray emulsion polymerization technique for the preparation of aqueous‐dispersible nanoscale core/shell poly(3,4‐ethylenedioxythiophene) (n‐PEDOT) colloids doped with poly[(4‐styrenesulfonic acid)‐co‐(maleic acid)] (PSS‐co‐MA). Scanning electron microscopy and transmission electron microscopy images revealed that these n‐PEDOT:PSS‐co‐MA colloids possessed sharp core/shell morphologies. X‐ray diffraction and Raman spectroscopy measurements revealed semi‐crystalline morphologies and quinoid‐dominated structures for these n‐PEDOT:PSS‐co‐MA colloids. The conductivities of n‐PEDOT and n‐PEDOT:PSS‐co‐MA pellets were ca. 3.2 and 0.29 S · cm?1, respectively, suggesting that PSS‐co‐MA acted as a shell that blocked the hopping of charges from the n‐PEDOT core to neighboring latexes. The work functions of pristine n‐PEDOT and n‐PEDOT:PSS‐co‐MA, measured using photoelectron spectroscopy, were ca. 4.7 and 5.05 eV, respectively; thus, they are close to that of indium tin oxide. The PSS‐co‐MA used in this study featured two different types of interactive functional groups, which acted as oxidative sites, dopants, and core/shell stabilizers during polymerization.
An electroactive polymer with well‐defined oligoanilines in the main chain has been prepared by oxidative coupling polymerization. The detailed characteristics of the polymer were systematically studied by FT‐IR, 1H NMR, GPC and XRD. Its electrochemical behavior was explored with UV‐Vis spectra and cyclic voltammetry showing that its intrinsic electroactivity was maintained and exhibited three distinct reversible oxidative states. Its electrical conductivity is about 3.91 × 10?4 S · cm?1 in HCl‐doped form at room temperature. Furthermore, the polymer displays a dielectric constant of 48.4 and 13.6 at 10 and 1 MHz, respectively, mainly attributed to the improvement in delocalized charge density and electrical conductivity of the polymer by introduction of the conjugated oligoaniline segments.
A series of anthracene‐based conjugated copolymers containing 9,10‐bis(6‐bromonaphthalen‐2‐yl)‐2‐tert‐butylanthracene (BNA) and 2,7‐diphenyl substituted fluorene (DPPF) moieties are prepared via a palladium‐catalyzed Suzuki polymerization. All of the synthesized polymers emit blue light at around 450 nm and show good thermal and color stability. Their electroluminescence spectra remain unchanged at high driving voltage. The double‐layer polymer light‐emitting diode (PLED) fabricated with ITO/PEDOT:PSS/DPPFBNA3/CsF/Al, produces a maximum brightness of 1 650 cd · m?2 and has a luminance efficiency of 0.39 cd · A?1. The ITO/PEDOT:PSS/TFB/DPPFBNA3/CsF/Al multilayer PLED, incorporating a TFB layer to facilitate hole transportation, produces a maximum brightness of 5 371 cd · m?2 and a luminance efficiency of 1.18 cd · A?1.
A new dithienyl benzotriazole‐based conjugated polymer was synthesized by Suzuki coupling reaction. The polymer was found to be soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene, with excellent film‐forming properties. The structure of the polymer was confirmed by 1H NMR, the molecular weights determined by GPC and the thermal properties investigated by TGA and DSC. The polymer films exhibited an absorption band in the wavelength range 300 to 610 nm. Preliminary photovoltaic cells based on the composite structure of indium tin oxide (ITO)/PEDOT:PSS/ PCDTBTz:PC 60 BM (1:2 w/w)/Al showed an open‐circuit voltage of 0.92 V, a power conversion efficiency of 2.2% and a short circuit current of 5.33 mA cm?2.
Summary: This paper focuses on the addition of tert‐butylcalix[4]arene (CA) to cross‐linked poly(dimethylsiloxane) (PDMS) membranes derived from poly(dimethylsiloxane) di(methyl methacrylate) macromonomer (PDMSDMMA) and various divinyl cross‐linker compounds, on the pervaporation characteristics for the removal of dilute benzene from an aqueous solution. When an aqueous solution of 0.05 wt.‐% benzene was permeated through the cross‐linked PDMSDMMA membranes containing CA they showed high benzene/water selectivity and permeability. Both the benzene/water selectivity and permeability of the membranes were enhanced by increasing both the divinyl compound cross‐linker content and the amount of CA, and were significantly influenced by the type of divinyl compound. Addition of CA to PDMSDMMA membranes cross‐linked with divinylperfluorohexane (DVF) showed the best pervaporation performance. The normalized permeation rate, benzene/water separation factor, and pervaporation separation index of these membranes were 1.86 × 10−5 kg · m/(m2 · h), 5 027, and 9 350, respectively. The pervaporation characteristics of the cross‐linked PDMSDMMA membranes containing CA were studied with respect to their chemical and physical structure. Furthermore, the mechanism of the selective permeation of benzene over water through these membranes was investigated.
Summary: 5,5′,6,6′‐Tetra(trimethylsiloxy)‐4,4,4,4′‐tetramethyl‐1,1‐spirobisindane was polycondensed with 1,4‐dicyanotetrafluorobenzene under variation of solvent temperature, time, and feed ratio. Under optimized reaction conditions, all products detectable by MALDI‐TOF mass spectrometry (up to masses around 8 000 Da) proved to be cyclic ladder oligomers and polymers. In N‐methylpyrrolidone and dimethylsulfoxide odd‐numbered cycles were formed in addition to the prevailing even‐numbered ones. However, in sulfolane exclusively even‐numbered cycles were obtained (detectable up to masses around 10 000 Da), together with even‐numbered linear chains. Temperatures above 100 °C enhanced the molecular weights by side reactions. With the less reactive cyano‐2,3,5,6‐tetrafluorobenzene (CTB) again cycles were formed, but their content and the conversions were lower. Polycondensation of CTB up to 160 °C and all polycondensations of cyanopentafluorobenzene gave crosslinked products.
Novel polyurethane (PU) cationomers are synthesized using an imidazolium diol‐based ionic liquid (IL) chain extender. A systematic comparison with a non‐ionic PU analogue reveals effect of the imidazolium cation on physical properties, hydrogen bonding, and morphology of segmented PU. Casting resulting PU solutions with various contents of IL generates novel membranes. Thermal study reveals that IL‐containing PU membranes exhibit a constant soft segment Tg at ?81 °C; however, the Tg of imidazolium hard segments systematically shifts to lower temperatures with increasing IL content. This suggests that IL preferentially locates into the imidazolium ionic hard domains, which is also evident in small‐angle X‐ray scattering. Moreover, dielectric relaxation spectroscopy demonstrates increased ionic conductivity of PU membranes by 5 orders of magnitude upon incorporation of 30 wt% IL.
Summary: Poly[ethylene‐co‐(butyl acrylate)‐co‐(carbon monoxide)] (polyEBC) samples, prepared from 13C‐labeled carbon monoxide, were characterized using two dimensional (2D) pulsed field gradient (PFG) 750 MHz NMR spectroscopy. To elucidate the complex mixture of structures present in this terpolymer, 2D 1H/13C‐heteronuclear multiple bond correlation (HMBC) experiments were conducted by selectively exciting the enhanced peaks resulting from 13C‐labeling. High resolution 2D NMR combined with 13C‐labeling of the polymer greatly simplifies the 2D NMR spectra, selectively enhances the weak peaks from low occurrence C‐centered triad structures and aids in their resonance assignments.
