N-vinylcarbazole Research Articles

Synthesis and photolytic properties of 1,5-di-N,N′-dialkylaminoanthraquinones containing acryloyl groups

Several l,5-di-N,N′-dialkyaminoanthraquinones containing acryloyl groups were synthesized and characterized by Fourier transform infrared (FTIR) and 1H NMR spectroscopy. The photophysical and photoinduction properties of these anthraquinone derivatives were examined in solution, in combination with free radical producing agents such as hexa-aryl-bis-imidazoles (HABI). When UV–vis absorption and fluorescence spectroscopy were employed to investigate the photophysical process, results showed that the photobleaching rate of N-alkylaminoanthraquinones containing an acrylate group and HABI was much faster than the acrylate group-free N-alkylaminoanthraquinone/HABI combination. N-alkylaminoanthraquinone induced polymerization of 2-phenoxyethyl acrylate (POEA)/N-vinyl carbazole (NVC)/cellulose acetate butyrate (CAB) mixtures was studied using real-time infrared spectroscopy (RTIR). It was found that the rate of polymerization was faster if the acryloyl groups were connected to the N,N′-dialkylaminoanthraquinone structure and that 1,5-di-N,N′-dialkylaminoanthraquinone containing acryloyl groups was more sensitive to visible light system.

Preparation of High Molecular Weight Poly(vinyl carbazole)/Polystyrene Blend Web by Electrospinning

To prepare fine and even poly(N-vinyl carbazole) (PVCz)/polystyrene (PS) blend webs, we performed a series of experiments varying processing parameters, including the type of solvent, PVCz/PS blend ratio, applied voltage, and tip to the collector distance (TCD). It was found that the morphology and the average diameter of PVCz/PS blend web were strongly correlated with electrospinning conditions. The morphologies of PVCz/PS blend webs were beaded or fine fibre structures, depending on the blend ratio of PVCz and PS. Increasing content of PS in the spinning solution tended to produce higher spinnability and the average diameter of electrospun web became smaller. The average diameter of the PVCz/PS blend web was slightly decreased with increasing applied voltage. In the case of TCDs, there was no significant effect on the PVCz/PS blend web morphologies but on increasing the TCD, the average diameter of the PVCz/PS blend webs slightly decreased.

Preparation and evaluation of microstructure, dielectric and conductivity (ac/dc) characteristics of a polyaniline/poly N-vinyl carbazole/Fe3O4 nanocomposite

A poly N-vinyl carbazole- Fe3O4 hybrid composite was prepared by solid state polymerization of N-vinyl carbazole (NVC) monomer in presence of Fe3O4 powder. This hybrid composite was dispersed in aqueous medium containing a known amount of potassium perdisulfate (KPS) as oxidant under constant sonication. A known amount of aniline (ANI) was injected in the system which started changing color and ultimately a black mass of (PANI-PNVC-Fe3O4) separated out. The composite was characterized by FTIR, FESEM and HRTEM analyses. XRD analyses using Williamson-Hall plot revealed average particle size of the PANI-PNVC-Fe3O4 composite to be around 34 nm. HRTEM analyses confirmed the particle size to be in the range 25–40 nm. The dielectric constants of PNVC–Fe3O4 system was low at 0.1–25 kHz whereas the PANI encapsulated PNVC–Fe3O4 nanocomposites showed significantly higher values of dielectric constant (>5500) at 0.1 kHz implying that the interfaces between grain and grain boundary of the composite play a dominant role for enhancing dielectric properties of the system. The ac conductivity was found to be independent of frequency in the range 102–103 Hz for all the nanocomposites implying contribution of free charges and rise thereafter appreciably in the frequency range of 1–25 kHz due to trapped charges in the grain boundary.

Orderly Ultrathin Films Based on Perylene/Poly(N‐vinyl carbazole) Assembled with Layered Double Hydroxide Nanosheets: 2D Fluorescence Resonance Energy Transfer and Reversible Fluorescence Response for Volatile Organic Compounds

Neutral poly(N-vinyl carbazole) (PVK) and perylene are coassembled within the interlayers of layered double hydroxide (LDH) nanosheets to form (perylene@PVK/LDH)(n) ultrathin films by the hydrogen-bond layer-by-layer assembly method. An efficient 2D fluorescence resonance energy transfer (FRET) process from PVK to perylene is demonstrated, and this FRET process can be inhibited/recovered reversibly by the adsorption/desorption of common volatile organic compounds (VOCs).

Quickly Updatable Hologram Images Using Poly(N-vinyl Carbazole) (PVCz) Photorefractive Polymer Composite

Quickly updatable hologram images using photorefractive (PR) polymer composite based on poly(N-vinyl carbazole) (PVCz) is presented. PVCz is one of the pioneer materials of photoconductive polymers. PR polymer composite consists of 44 wt % of PVCz, 35 wt % of 4-azacycloheptylbenzylidene-malonitrile (7-DCST) as a nonlinear optical dye, 20 wt % of carbazolylethylpropionate (CzEPA) as a photoconductive plasticizer and 1 wt % of 2,4,7-trinitro-9-fluorenone (TNF) as a sensitizer. PR composite gives high diffraction efficiency of 68% at E = 45 V μm−1. Response speed of optical diffraction is the key parameter for real-time 3D holographic display. The key parameter for obtaining quickly updatable holographic images is to control the glass transition temperature lower enough to enhance chromophore orientation. Object image of the reflected coin surface recorded with reference beam at 532 nm (green beam) in the PR polymer composite is simultaneously reconstructed using a red probe beam at 642 nm. Instead of using a coin object, an object image produced by a computer was displayed on a spatial light modulator (SLM) and used for the hologram. The reflected object beam from an SLM was interfered with a reference beam on PR polymer composite to record a hologram and simultaneously reconstructed by a red probe beam.

Synthesis and Characterization of Novel Polymer of Vinyl Carbazole Bearing Thiophene Groups

Combination of vinyl carbazole and thiophene groups’ excellent thermal properties and optical properties, a novel polymer named poly(2,7-bi-2-thienyl-9-vinyl-9-H-carbazole) was synthesized via radical polymerization and Suzuki reaction. The polymer was characterized using Fourier transform infrared spectrometer(FT-IR), gel permeation chromatography(GPC), differential scanning calorimetry(DSC), and X-Ray fluorescence spectrometer(XRF). It was found that this π-conjugated polymer containing vinyl carbazole and thiophene groups gave a high glass transition temperature (Tg=251°C). This feature made poly(2,7-bi-2-thienyl-9-vinyl-9-H-carbazole) possessing an excellent thermal performance.

A facile strategy to modulate the fluorescent properties of star polymers by varying the arm numbers

A simple approach to tune the fluorescent properties of star polymers was reported via only adjusting the arm numbers. Atom transfer radical polymerization (ATRP) using β-CD-based initiators was utilized to synthesize star-shaped poly(N-vinyl carbazole) (star PVK) consisting of β-cyclodextrin (β-CD) core and different arm numbers (3, 7, and 14). The conversion ratio was nearly 100 % characterized by 1H-NMR. Fluorescent properties of star PVKs could be modulated by varying the arm number at the same mass concentration of fluorescent groups. Fluorescence intensity declined with the increase of arm number and displayed “sandwich-like excimer” emission rather than “higher-energy excimer” emission. The unique structure of star polymer might effectively inhibit the formation of “random coil”, which often happened in linear polymer systems. In addition, all of the star PVKs with different arm numbers had the same emission peak centered at 395 nm and excimer band at 420 nm, respectively, which differed from their linear counterparts and demonstrated that the intramolecular interaction was not dominant in this system.

Synthesis of Triazole‐Based Amphiphilic Block Copolymers Containing Carbazole Moiety By RAFT Polymerization

AbstractN‐Vinyl‐1,2,4‐triazole (NVTri), which is a nonconjugated N‐vinyl monomer having a basic aromatic heterocycle, was polymerized by reversible addition–fragmentation chain transfer (RAFT) polymerization. With the xanthate‐type chain transfer agent (CTA), reasonable control of the polymerization of NVTri was confirmed by the formation of the relatively low polydispersity products, linear increase in the molecular weight with the conversion, feasibility to control molecular weight, and chain extension experiment. Chain extension from poly(NVTri) to N‐vinyl carbazole (NVC) could be well controlled under suitable conditions and provided novel amphiphilic block copolymers. We investigated assembled structures and basic optoelectronic properties of the block copolymers.

Semiconductor–LC Layer Boundary and Photonic Structures

Theoretical discussion and numerical results for experimentally obtained new kind of the optical waveguide has been presented. Discussed waveguide is optically self-induced during light beam propagation along boundary between liquid crystal and semiconducting polymer. Light is propagated in electrically driven liquid crystal (LC) cell. Experimental results obtained earlier are reported in here shortly, and theoretical model of the observed phenomena is discussed as well as numerical outcome. Exploited nematic liquid crystal was of high birefringence near to 0.35. Experimental data have been obtained in the case of poly (N-vinyl) carbazole as photorefractive polymer doped with 2, 4, 7-trinitro-fluorenone, and numerical simulation has been done for this case.

Free-standing poly[poly(N-vinyl carbazole)]-supported Pt-based catalysts with enhanced performance for methanol electro-oxidation in alkaline medium

Pt-based catalysts with free-standing poly[poly(N-vinyl carbazole)] (PPVK) as support (Pt–M/PPVK, M=Pd, Au, and Ru) on a glassy carbon electrode (GCE) have been successfully prepared by an electrochemical method. Cyclic voltammetric and chronoamperometric methods are used to investigate the electrocatalytic activity and stability of as-prepared catalysts. It is found that PPVK film as support effectively enhances the catalytic acitivity of Pt nanoparticles for methanol electro-oxidation in alkaline medium. The bimetallic Pt–M nanoparticles obtained potentiostatically on the PPVK film show the higher electrocatalytic activity than bare Pt/GCE and JM Pt/C. In addition, to pin down the external influencing factors, systematic studies have been conducted on the methanol electro-oxidation at as-prepared catalysts as a function of platinum loading, PPVK mass, methanol and KOH concentrations.

Particular thermally induced phase separation of liquid crystal and poly(N-vinyl carbazole) films and its application

In the current study, a method of particular thermally induced phase separation (TIPS) of liquid crystals (LCs) and polymers is presented. The method involves a combination of dissolution process and TIPS. The LCs and poly(N-vinyl carbazole) (PVK) play the roles of solvent and solute, respectively, during the processes of particular TIPS. The nematic LC sample fabricated by two substrates coated with uniform PVK films is heated and then cooled, generating the rough PVK layers onto the surfaces of the substrates. The LC sample having rough PVK layers produces micron-sized, multiple domains of disordered LCs that can scatter incident light. Additionally, an application of a scattering mode light shutter, having the advantages of low driving voltage, polarization-independent scattering, fast response, high contrast ratio, and being polarizer free, is reported.

Chain Transfer Kinetics of Acid/Base Switchable N-Aryl-N-Pyridyl Dithiocarbamate RAFT Agents in Methyl Acrylate, N-Vinylcarbazole and Vinyl Acetate Polymerization

The structures of the “Z” and “R” substituents of a RAFT agent (Z–C(S)S–R) determine a RAFT agent’s ability to control radical polymerization. In this paper we report new acid/base switchable N-aryl-N-pyridyl dithiocarbamates (R = −CH2CN, Z = −N(Py)(Ar)) which vary in substituent at the 4-position of the aryl ring and the use of these to control molecular weight and dispersity. In their protonated form, the new RAFT agents are more effective in controlling polymerization of the more activated monomer, methyl acrylate (MA), whereas in their neutral form they provide more effective control of the polymerization of less activated monomers, N-vinyl carbazole (NVC) and vinyl acetate (VAc). For each polymerization, the apparent chain transfer coefficient (Ctrapp) shows a good correlation with Hammett parameters. Dithiocarbamates with more electron-withdrawing aryl ring substituents have the higher Ctrapp. This demonstrates the influence of polar effects on Ctrapp and supports the hypothesis that the activity of these RAFT agents is determined by the availability of the lone pair of the dithiocarbamate nitrogen.

Electrical and optical properties of blue organic light-emitting devices fabricated utilizing color conversion CdSe and CdSe/ZnS quantum dots embedded in a poly(N-vibyl carbazole) hole transport layer

Blue organic light-emitting devices (OLEDs) with color conversion quantum dots (QDs) embedded in a poly(N-vinyl carbazole) (PVK) hole transport layer (HTL) were fabricated. The absorbance and the photoluminescence spectra for the CdSe and the CdSe/ZnS QDs showed dominant exciton peaks. Current densities as functions of the voltage showed enhanced hole trapping and a decreased hole current in the OLEDs containing CdSe and CdSe/ZnS QDs embedded in a HTL. The phenomena were intensified due to the existence of the ZnS shell. The luminance-voltage curve and the electroluminescence spectra showed that the brightness of the blue OLEDs fabricated utilizing the HTL based on CdSe and CdSe/ZnS QDs embedded in a PVK layer reached over 3,000 cd/m2 and that the dominant exciton peak was shifted to longer wavelength.

Energy Transfer from Poly(Vinyl Carbazole) to a Fluorene‐Vinylene Copolymer in Solution and in the Solid State†

This article reports a comparative study of the energy transfer processes in solution and the solid state from poly(vinyl carbazole; the donor) to dimethylphenyl-terminated poly[(9,9-dioctylfluorenyl-2,7-divinylene-fluorene)-co-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (the acceptor). The results in solutions suggest that a decrease of the donor emission intensity with an increasing acceptor concentration is more closely related to the trivial energy transfer process, indicating that the donor and acceptor chains are not in close contact during the lifetime of the donor excited state. This conclusion was reached using the amplitude-averaged lifetime of the donor, which is practically independent of the acceptor concentration. In the solid state, the polymer blends showed a decrease in the donor emission with an increasing acceptor concentration, and a decrease in the donor lifetime was also observed. Thus, in the solid state, changes in morphology interfere with the nonradiative resonant energy transfer process, but influence on the trivial process cannot be completely neglected. The lifetime does not follow a continuous decrease with the PFO-MEHPV concentration like the emission intensity does. The changes in the lifetime values occur over the same concentration range as do the changes of morphology, as shown by the scanning electron micrographs.

Copolymers of carbazoles and methyl ethyl ketone formaldehyde resin

PurposeThe purpose of this paper is to develop the soluble and processable conducting copolymers of carbazole (Cz), ethylcarbazole (ECz), N‐vinylcarbazole (NVCz) by oxidatively polymerising carbazoles by ceric ammonium nitrate (CAN) in the presence of methyl ethyl ketone formaldehyde resin (MEKF‐R); and to report the advantages of obtaining copolymer structure.Design/methodology/approachA new class of soluble and conductive P(Cz/MEKF‐R), P(NVCz/MEKF‐R) and P(ECz/MEKF‐R) copolymers were synthesised by the method of oxidative polymerisation with ceric ammonium nitrate. MEKF‐R, CAN and carbazole monomers (Cz, NVCz and ECz) were dissolved in acetonitrile separately. Then, the CAN solution was added dropwise into the mixture of MEKF‐R and Cz, NVCz or ECz solutions while stirring and a green powder was formed almost instantaneously. After one hour stirring at 25°C, the powder was filtered, washed with acetonitrile and dried at room temperature. A green coloured product was obtained. The colourless insulator copolymer present in this product was separated by selectively dissolving with toluene. The insoluble green copolymer was filtered off and dried at room temperature under vacuum. The products were characterised by FTIR, DSC thermograms, 1H‐NMR, four‐point probe conductivity and atomic absorption measurements.FindingsThe solubility and conductivity of the Cz/MEKF‐R copolymer P(Cz/MEKF‐R), the NVCz/MEKF‐R copolymer P(NVCz/MEKF‐R) and the ECz/MEKF‐R copolymer P(ECz/MEKF‐R) were regulated by the ratios of (Cz, NVCz, ECz)/CAN/MEKF‐R. By inclusion of the ketonic resin segments to the polycarbazole chains, thermally processable copolymers have been obtained with a melting point of about 80°C. FT‐IR results in different reaction time and the presence of metal in copolymers show together a complex between monomer‐metal and resin.Research limitations/implicationsThis study focuses on obtaining conductive, soluble and processable copolymers. Since the ketonic resin is an insulator, in order to obtain both conductive and totally soluble polymer, successively regulating the ratios of (Cz, NVCz, ECz)/CAN/MEKF‐R is necessary.Practical implicationsThis work provides technical information for the synthesis of conducting and totally soluble copolymer.Originality/valueThe conductive P(Cz/MEKF‐R), P(NVCz/MEKF‐R) and P(ECz/MEKF‐R) copolymers obtained by the method of oxidative polymerisation with ceric ammonium nitrate, which are totally soluble in DMF, could only be produced with this method and may increase the area of application of the carbazole polymers.

Electrospray deposition of polymer thin films for organic light-emitting diodes

Electrospray process was developed for organic layer deposition onto polymer organic light-emitting diode [PLED] devices in this work. An electrospray can be used to produce nanometer-scale thin films by electric repulsion of microscale fine droplets. PLED devices made by an electrospray process were compared with spin-coated ones. The PLED device fabricated by the electrospray process showed maximum current efficiency of 24 cd/A, which was comparable with that of the spin-coating process. The electrospray process required a higher concentration of hole and electron transport materials in the inks than spin-coating processes to achieve PLED maximum performance. Photoluminescence [PL] at 407 nm was observed using electrosprayed poly(N-vinyl carbazole) films, whereas a peak at 410 nm was observed with the spin-coated ones. Similar difference in peak position was observed between aromatic and nonaromatic solvents in the spin-coating process. PLED devices made by the electrospray process showed lower current density than that of spin-coated ones. The PL peak shift and reduced current of electrosprayed films can therefore be attributed to the conformation of the polymer.

Dye Sensitized Solar Cells Using Nanocrystalline CuAlO2/β-CuSCN Embedded Poly(vinyl carbazole) Composites as Solid Hole-Transporter

Dye Sensitized Solar Cells Using Nanocrystalline CuAlO₂/<i>β</i>-CuSCN Embedded Poly(vinyl carbazole) Composites as Solid Hole-Transporter

Electrochemical investigations on the corrosion protection effect of poly(vinyl carbazole)‐silica hybrid sol–gel materials

AbstractA series of sol–gel derived organic–inorganic hybrid coatings consisting of organic poly (vinyl carbazole) (PVK) and inorganic silica (SiO2), with 3‐(trimethoxysilyl)propyl methacrylate (MSMA) as coupling agent, were successfully synthesized. First of all, vinyl carbazole (VCz) monomers are copolymerized with MSMA by performing free‐radical polymerization reactions with AIBN as initiator. Subsequently, as‐prepared copolymer (i.e., sol–gel precursor) was further reacted with various feeding content of tetraethyl orthosilicate (TEOS) through organic acid (CSA)‐catalyzed sol–gel reaction to form a series of PVK‐silica hybrid (PSH) sol–gel materials. The as‐synthesized hybrid materials were subsequently characterized by Fourier‐Transformation infrared (FTIR) spectroscopy and solid‐state 29Si NMR. It should be noted that the PVK‐SiO2 hybrid (PSH) coating on cold‐rolled steel (CRS) electrode with low silica loading (e.g., 10 phr) was found to be superior in anticorrosion property over those of neat PVK based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current, and electrochemical impedance spectroscopy in 3.5 wt% NaCl electrolyte. The better anticorrosion performance of PSH coatings as compared to that of neat polymer may probably be attributed to the stronger adhesion strength of PSH coatings on CRS electrode, which was further evidenced by Scotch tape test evaluation. Increase of adhesion strength of PSH coatings on CRS electrode may be associated with the formation of Fe–O–Si covalent bonds at the interface of PSH coating and CRS electrode based on the FTIR–RAS (reflection absorption spectroscopy) studies. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers

Preparation and Optical Properties of CdS/PVK Nanocomposites Based on CdS Nanorod Arrays

Well-defined CdS nanorod arrays were pepared via a facile one-step hydrothermal approach and Poly (N-vinyl carbazole) (PVK)/CdS nanocomposites were fabricated by spin-coating chloroform solution of PVK on the surface of CdS film. A variety of techniques including scanning electron microscopy (SEM), optical absorption and photoluminescence (PL) were employed to investigate the surface morphology and optical properties of PVK/CdS nanocomposites. Photoluminescence efficiency of nanocomposites decreases compared to pure PVK and CdS nanorod arrays due to quenching through high photocharge generation quantum efficiency and high charge transport between inorganic semiconductor and conducting polymer.

Efficient and low potential operative host/guest concentration graded bilayer polymer electrophosphorescence devices

This study investigates enhanced electrophosphorescence and its mechanism in poly(N-vinyl carbazole) (PVK): N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1-biphenyl]-4,4′-diamine (TPD)/2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD): fac-tris(2-phenylpyridine)iridium [Ir(ppy) 3] concentration graded bilayer electroluminescence devices. The two layers are partially intermixed at the bilayer interface because the upper layer (composed of Ir(ppy) 3 and PBD) was spun cast from a solvent that slightly swells the bottom layer (composed of PVK and TPD). Moreover, PBD in the upper layer can act as an efficient electron transport layer as well as a hole blocking layer, resulting in greatly enhanced electron–hole recombination. An indium tin oxide (ITO)/3,4-polyethylenedioxythiophene–polystyrenesulfonate (PEDOT)/[PVK:TPD/Ir(ppy) 3:PBD] bilayer/LiF/Al device showed dramatically decreased turn-on and driving voltages, enhanced luminescence efficiency, and narrower emission spectra compared to those of conventional ITO/PEDOT:PSS/[PVK:TPD:Ir(ppy) 3:PBD] blend/LiF/Al devices.