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The fabrication of truly hierarchically folded single‐chain polymeric nanoparticles with primary, secondary, and defined 3D architecture is still an unfulfilled goal. In this contribution, a polymer is reported that folds into a well‐defined 3D structure from a synthetic sheet‐helix block copolymer. The sheet‐like poly(p‐phenylene vinylene) (PPV) block is synthesized via the ring‐opening metathesis polymerization of a thymine‐bearing dialkoxy‐substituted [2.2]paracyclophane‐1,9‐diene. The PPV block is terminated with a Pd complex using a Pd‐containing chain‐terminating agent. The terminal Pd complex catalyzes the polymerization of isocyanide monomers with side‐chains containing either a chiral menthol or an achiral diaminopyridine resulting in the formation of a helical poly(isocyanide) (PIC) random copolymer. The PIC side‐chains are capable of engaging in complementary hydrogen‐bonding with thymine units along the PPV block resulting in the folding of the two secondary structural domains into a well‐defined 3D structure. The folding and unfolding of the polymer in both chloroform and THF are monitored using dynamic light scattering and NMR spectroscopy. This work is the first example of a hierarchically folded synthetic polymer featuring a defined 3D structure achieved by using two different polymer backbones with two distinct secondary structures. [ABSTRACT FROM AUTHOR]

Poly(p-phenylene vinylene) (PPV) is one of the earliest discovered photoluminescent polymer with regular structure and high fluorescence quantum yield. Many methods have been reported for the synthesis of PPV, but most of them are not feasible for controlling the molecular weight and molecular weight distribution of PPV. Confining chemical reactions in porous channels is a common method to control the chemo- and stereo- selectivity and modulate the reaction rate. Therefore, many methods have been developed for loading the catalysts inside porous materials to regulate chemical reactions and polymerizations. To this end, palladium catalysts were selectively loaded into the pores of mesoporous silica materials with different pore sizes for the controlled synthesis of PPV. Six types of mesoporous palladium nanoreactors were prepared using three different types of mesoporous silica materials (dendritic mesoporous silica nanospheres, SBA-15, and low aspect ratio SBA-15). Their stable mesoporous structure and efficient loading of palladium catalysts in the pores were determined by nitrogen adsorption-desorption analysis and transmission electron microscopy. The palladium content was measured by plasma emission spectroscopy. Heck coupling polymerizations between dihexoxy substituted diiodobenzene and divinylbenzene monomers were thus ushered inside the nanopores to get the molecular weight of the PPV product controlled through the spatial confinement effect of the pores. The reactions were carried out at 135 °C for 3 d and the polymeric products were directly subjected for structural analysis. Fourier transform infrared spectroscopy showed that the obtained PPV consisted of para-substituted benzene rings and trans-ethylene groups, similar to the literature reported ones. The molecular weight of PPV was measured by gel permeation chromatography. It can be found that PPV with narrower molecular weight distributions was obtained in six kinds of palladium-loaded nanoreactors in comparison with that obtained in homogeneous catalytic system. The dispersity of the PPV obtained through this strategy reached as low as 1.53. [ABSTRACT FROM AUTHOR]

Sensitive detection of nitrogen dioxide (NO2) is of significance in many areas for health and environmental protections. In this work, we developed an efficient NO2 sensor that can respond within seconds at room temperature, and the limit of detection (LOD) is as low as 100 ppb. Coating cyano-substituted poly(p-phenylene vinylene) (CN-PPV) films on graphene (G) layers can dope G sheets effectively to a heavy n state. The influences of solution concentrations and annealing temperatures on the n-doping effect were investigated in detail. The CN-PPV–G transistors fabricated with the optimized parameters demonstrate active sensing abilities toward NO2. The n-doping state of CN-PPV–G is reduced dramatically by NO2, which is a strong p-doping compound. Upon exposure to 25 ppm of NO2, our CN-PPV–G sensors react in 10 s, indicating it is almost an immediate response. LOD is determined as low as 100 ppb. The ultrahigh responding speed and low LOD are not affected in dry air. Furthermore, cycling use of our sensors can be realized through simple annealing. The superior features shown by our CN-PPV–G sensors are highly desired in the applications of monitoring the level of NO2 in situ and setting immediate alarms. Our results also suggest that transfer curves of transistors can react very promptly to the stimulus of target gas and, thus, are very promising in the development of fast-response sensing devices although the response values may not reach maximum as a tradeoff. [ABSTRACT FROM AUTHOR]

Poly(p‐phenylene vinylene)s (PPVs) and poly(arylene vinylene)s are key materials for a variety of applications ranging from organic light emitting diodes to fluorescent optical probes. Their syntheses, however, have been hampered by non‐living or step‐growth polymerization techniques. The development of functional‐group tolerant olefin metathesis catalysts has enabled the use of living ring‐opening metathesis polymerization (ROMP) of cyclophane monomers yielding PPVs and poly(p‐phenylene‐co‐arylene vinylene)s in a living manner. Low dispersity and soluble PPVs are afforded with control over the number of repeat units with easy incorporation of different end‐groups at their heads or tails. In this review, a comprehensive overview of tetrasubstituted and disubstituted alkyl and alkoxy containing [2.2]paracyclophane‐1,9‐diene, [2.2]metaparacyclophane‐1,9‐diene, [2.2.2]paracyclophane‐1,9,17‐triene, and benzothiadiazole‐[2.2]paracyclophane‐1,9‐diene is provided. The high ring strain of these monomers enables efficient polymerizations with ruthenium initiators. A particular emphasis is on [2.2]paracyclophane‐1,9‐dienes as it is the most investigated class of polymerized cyclophanediene since initially reported 30 years ago. Additionally, applications for soft materials synthesized by ROMP are examined, highlighting easily accessed PPV copolymers and PPV block copolymers that can be phototriggered, as well as PPVs featuring supramolecular recognition units installed at their termini to afford orthogonally self‐assembled architectures. [ABSTRACT FROM AUTHOR]

Composites of poly(p-phenylene vinylene) (PPV) and different carbon nanostructures, such as fullerene C60, multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), graphene oxide (GO), and graphene nanoplatelets (GNPLs), were produced by Wittig's soluble precursor procedure in solutions containing dispersed particles of carbon nanomaterials. These composites were investigated using infrared and Raman spectroscopy, scanning and transmission electron microscopy, thermogravimetry analysis, adsorption/desorption of N2 measurement, and electrochemistry. Composites are produced in the form of nanostructural porous materials. A significant increase in the BET (Brunauer–Emmett–Teller) surface is observed for composites in comparison to unmodified PPV. The highest BET surface area of 125 m2·g−1 was obtained for the PPV/SWCNT composite. Compared to pristine PPV, composites also exhibit higher thermal stability. The effect of the content of composite components on their electrochemical properties was also investigated. The electronic interaction between components of composite significantly affects their electrochemical properties, particularly in the case of oxidation processes. PPV incorporated into network of carbon nanostructures exhibit two well separated oxidation steps. The carbon component is responsible for the shift of the PPV reduction and oxidation processes toward less negative and less positive potentials, respectively, significantly lowering the energy of the band gap. [ABSTRACT FROM AUTHOR]

Sensitive detection of nitrogen dioxide (NO2) is of significance in many areas for health and environmental protections. In this work, we developed an efficient NO2 sensor that can respond within seconds at room temperature, and the limit of detection (LOD) is as low as 100 ppb. Coating cyano-substituted poly(p-phenylene vinylene) (CN-PPV) films on graphene (G) layers can dope G sheets effectively to a heavy n state. The influences of solution concentrations and annealing temperatures on the n-doping effect were investigated in detail. The CN-PPV–G transistors fabricated with the optimized parameters demonstrate active sensing abilities toward NO2. The n-doping state of CN-PPV–G is reduced dramatically by NO2, which is a strong p-doping compound. Upon exposure to 25 ppm of NO2, our CN-PPV–G sensors react in 10 s, indicating it is almost an immediate response. LOD is determined as low as 100 ppb. The ultrahigh responding speed and low LOD are not affected in dry air. Furthermore, cycling use of our sensors can be realized through simple annealing. The superior features shown by our CN-PPV–G sensors are highly desired in the applications of monitoring the level of NO2 in situ and setting immediate alarms. Our results also suggest that transfer curves of transistors can react very promptly to the stimulus of target gas and, thus, are very promising in the development of fast-response sensing devices although the response values may not reach maximum as a tradeoff.

A quasi‐one‐dimensional organic semiconductor, hepta(p‐phenylene vinylene) (HPV), was incorporated into a DNA tensegrity triangle motif using a covalent strategy. 3D arrays were self‐assembled from an HPV‐DNA pseudo‐rhombohedron edge by rational design and characterized by X‐ray diffraction. Templated by the DNA motif, HPV molecules exist as single‐molecule fluorescence emitters at the concentration of 8 mM within the crystal lattice. The anisotropic fluorescence emission from HPV‐DNA crystals indicates HPV molecules are well aligned in the macroscopic 3D DNA lattices. Sophisticated nanodevices and functional materials constructed from DNA can be developed from this strategy by addressing functional components with molecular accuracy. [ABSTRACT FROM AUTHOR]

The intramolecular oxidative photocyclization of 1,2‐diarylhexafluorocyclopentene (1) under light irradiation (λ = 365 nm) provided hexafluorocyclopentene‐fused phenanthrene with formyl groups (2) in moderate yield. The copolymerization of 2 with tetraethyl(2,5‐bis(dodecyloxy)‐1,4‐phenylene)bis(methylene)diphosphonate by the Horner–Wadsworth–Emmons reaction gave a fluorine‐containing poly(phenylene vinylene), Polymer‐2, in 41% yield. For comparison, a diphenylethene‐type copolymer, Polymer‐1, was also prepared analogously. The number‐average molecular weights of Polymer‐1 and Polymer‐2 were 8900 and 3300 g mol−1, respectively. The copolymers showed high thermal stability, as revealed by their thermogravimetric analysis. UV–visible spectra of the copolymers in CHCl3 showed π–π* transition peaks at around 420 nm, and the peaks shifted to longer wavelengths by ca 10 nm for samples in film form. The photoluminescence spectra of Polymer‐1 and Polymer‐2 exhibited peaks at 542 and 560 nm in CHCl3, respectively, whereas the photoluminescence intensity of Polymer‐2 was very low in the solid state, presumably owing to the partial aggregation of the polymer molecules. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

Conducting polymers (CPs), by virtue of their important properties, like ready availability, easy processing, cost effectiveness, ease of functionalization and derivatization, and excellent electrical, optical, electrochemical and photochemical properties, have gained such enormous attention in the last few decades that they have found extensive employment in a wide variety of real-life applications, including bioimaging, tissue engineering, sensors, energy storage devices and optoelectronic devices. The most widely studied CPs are polyaniline, polythiophene, polypyrrole, poly(3,4-ethylenedioxythiophene) and polyacetylene. On the other hand, the CP poly(p-phenylene vinylene) (PPV) has attracted relatively much lesser attention over the years, in spite of it possessing several extraordinary attributes, like tuneable optical properties, good reactivity and high electrical conductivity. These properties can be achieved by merely changing the side chains attached to the main polymer backbone. Research on development of PPV has been going on for nearly about three decades; and it has been able to find some important applications in certain crucial fields, as mentioned below. Keeping this in mind, this review aims at focusing entirely on PPV, with the objective of bringing out its several positive attributes. The objective of this review is to analyze the potential of PPV towards getting involved in a number of practically important applications. For this purpose, discussions have been made on the major routes to synthesize PPV and its exciting properties (viz. electroluminescence and photoluminescence). In terms of applications, its involvements in light-emitting diodes, solar cells, sensors, bioimaging, field-effect transistors, supercapacitors, and actuators have been presented. [ABSTRACT FROM AUTHOR]

Abstract: A flexible, natural rubber (NR) patch was developed for electrically controllable transdermal drug delivery. NR latex was crosslinked at various crosslinking ratios under the UV curing method. Ibuprofen (Ibu) was the model drug and was used as the dopant for poly(p‐phenylene vinylene) (PPV) acting as the drug encapsulating host. For the pristine Ibu‐loaded NR patch, the amount of Ibu permeation increased with decreasing crosslink density and increasing electrical potential. For the Ibu‐doped PPV/NR patch, the amount of Ibu release−permeation also increased with increasing electrical potential and was higher than that of the pristine NR matrices. Without an applied electric field, the drug remained attached to the PPV during an initial period of 6 h. Under an applied electric field, the oxidation state of the conductive polymer was altered, the iontophoretic effect, pore formation in the NR matrix, expansion of the pore size in hair follicles and PPV chain expansion combined to increase the Ibu release−permeation amount. Thus, the flexible PPV/NR transdermal drug delivery patch was demonstrated to be effective in drug release−permeation based on the strength of the electrical potential, the crosslinking density and the presence of PPV as the encapsulation host. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Substitution of selected CC units in π-conjugated organic frameworks by their isoelectronic and isosteric BN units (BN/CC isosterism) has proven to be a successful concept for the development of BN-doped polycyclic aromatic hydrocarbons (PAHs) with intriguing properties and functions. The first examples have just demonstrated the applicability of this approach to polymer chemistry. Herein, we present the synthesis and comprehensive characterization of the first poly(p-phenylene iminoborane). This novel inorganic-organic hybrid polymer can be regarded as a BN analogue of the well-known poly(p-phenylene vinylene) (PPV). Photophysical investigations on the polymer and a series of model oligomers provide clear evidence of some π-conjugation across the B=N bonds and extension of the conjugation path with increasing chain length. TD-DFT calculations provide deeper insight into the electronic structure of the new materials. [ABSTRACT FROM AUTHOR]

In this report, we studied the thickness effect on the optical and morphological properties of self-assembled (SA) poly(p-phenylenevinylene) (PPV) films, wich were processed with 5 and 75 layers from a PPV precursor polymer and dodecylbenzenesulfonate, and then, thermally converted at 230 °C. The increase of the film thickness yielded more intense peaks in the vibrational spectral range. The electron-phonon coupling was quantified by the Huang - Rhys factor, that shows the effects on the polymer chain mobility in the interface substrate/polymer. A strong emission anisotropy r=0.57 was observed for the film with 5 layers of thickness decreasing to 0.34 for the film with 75 layers. Finally, the surface topology of the films was measured using Atomic Force Microscopy.

In this report, we studied the thickness effect on the optical and morphological properties of self-assembled (SA) poly(p-phenylenevinylene) (PPV) films, wich were processed with 5 and 75 layers from a PPV precursor polymer and dodecylbenzenesulfonate, and then, thermally converted at 230 degreesC. The increase of the film thickness yielded more intense peaks in the vibrational spectral range. The electron-phonon coupling was quantified by the Huang - Rhys factor, that shows the effects on the polymer chain mobility in the interface substrate/polymer. A strong emission anisotropy r=0.57 was observed for the film with 5 layers of thickness decreasing to 0.34 for the film with 75 layers. Finally, the surface topology of the films was measured using Atomic Force Microscopy.

A study is presented of the formation and optical properties of polymeric heterostructures from poly(p-phenylene vinylene) (PPV) and poly(o-methoxyaniline) (POMA) produced via the self-assembly technique. POMA layers were obtained in a non self-limiting process from its emeraldine salt, semiconducting form in HCl solution. Thermal conversion of PPV was performed at low temperatures with the substitution of the counter-ion Cl in the PPV precursor by a long sulfonic chain, the dodecylbenzenesulfonate (DBS) ion. The optical properties of PPV films converted in this way are not affected by POMA, which can be used as transparent electrode of PPV luminescent devices.

A systematic investigation into the chain transfer polymerization of the so-called radical precursor polymerization of poly(p-phenylene vinylene) (PPV) materials is presented. Polymerizations are characterized by systematic variation of chain transfer agent (CTA) concentration and reaction temperature. For the chain transfer constant, a negative activation energy of -12.8 kJ·mol-1 was deduced. Good control over molecular weight is achieved for both the sulfinyl and the dithiocarbamate route (DTC). PPVs with molecular weights ranging from thousands to ten thousands g·mol-1 were obtained. To allow for a meaningful analysis of the CTA influence, Mark–Houwink–Kuhn–Sakurada (MHKS) parameters were determined for conjugated MDMO-PPV ([2-methoxy-5-(3′,7′-dimethyloctyloxy)]-1,4-phenylenevinylene) to α = 0.809 and k = 0.00002 mL·g-1. Further, high-endgroup fidelity of the CBr4-derived PPVs was proven via chain extension experiments. MDMO-PPV-Br was successfully used as macroinitiator in atom transfer radical polymerization (ATRP) with acrylates and styrene. A more polar PPV counterpart was chain extended by an acrylate in single-electron transfer living radical polymerization (SET-LRP). In a last step, copper-catalyzed azide alkyne cycloaddition (CuAAC) was used to synthesize block copolymer structures. Direct azidation followed by macromolecular conjugation showed only partial success, while the successive chain extension via ATRP followed by CuAAC afforded triblock copolymers of the poly(pphenylene vinylene)-block-poly(tert-butyl acrylate)-block-poly(ethylene glycol) (PPV-b-PtBuA-b-PEG). [ABSTRACT FROM AUTHOR]

Highlights: [•] We produce novel composite nanofibers based on poly(p-phenylene vinylene) derivatives. [•] The nanofibers show a novel morphology consisting of spontaneously stacked nanofibers. [•] We examine in detail the factors that influence the nanofibers morphology. [•] The highly fluorescent and porous nanofibers mats provide good biosensing substrates. [•] The results show that the nanofibers can be used to construct a simple oligonucleotide sensor. [Copyright &y& Elsevier]

Block copolymers show great promise and are widely studied due to their improved properties (thermal, luminescent). However, the combination of these compounds with ionic liquids (ILs) can alter/improve the physical properties of the formed composite even further. In this study a composite formed by the poly(p -phenylene vinylene- b -ethylene glycol) PPV/PEG block copolymer and the IL butyltrimethylammonium bis(trifluoromethanesulfonyl) imide was prepared, and its interactions and properties analyzed. Composites with two different proportions were prepared (PPV/PEG + IL 1:1 and 3:1) and later analyzed by different techniques: FTIR, TGA, DSC, XRD, UV–vis and fluorescence spectroscopy. FTIR results demonstrated the occurrence of an interesting physical interaction between the IL and PEG fraction of the block copolymer, an observation confirmed by the DSC and XRD analyses. The addition of the IL also results in the alteration of degradation events and a decrease in the crystallinity of the copolymer. Finally, the absorption and emission spectra showed that the block copolymer preserves its luminescent characteristics, even when a higher amount of IL is added. In addition, an interesting increase in the emission intensity for the two composites was noted due to the addition of IL in the material, being an promising feature for future devices. [Display omitted] • Ionic liquid and PPV/PEG composites demonstrated interaction between IL and the PEG portion of the block copolymer. • The addition of IL alters the degradation of the block copolymer, also altering the crystallinity of the copolymer (CP). • With the addition of IL, luminescent properties of the CP are preserved, with an increase in emission intensity as well. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid (HSt) Langmuir–Blodgett (LB) films, and their conducting and luminescent properties were enhanced by the incorporation of palladium nanoparticles stabilised by glucose oxidase (GOx-PdNPs). The nanobiocomposite, based on HSt, PPV, and GOx-PdNPs, was transferred from the air-water interface onto solid supports using the LB technique. The films were characterised by surface pressure–area isotherms, polarisation modulation infrared reflection–absorption spectroscopy, fluorescence spectroscopy, and conductivity measurements. The results indicated that the incorporation of GOx-PdNPs in PPV-HSt LB films enhances the luminescence and conducting properties of the PPV. Based on the higher conductivity and emission obtained with the hybrid LB films and the ability to tune the molecular-level interactions between the film components by changing the experimental conditions, thus allowing for further optimisation, one may envisage applications for these films in optical and electronic devices, such as organic light-emitting diodes. [Copyright &y& Elsevier]

Abstract: In the present paper the layer-by-layer self-assembly (LbL) technique was used to obtain poly(p-phenylenevinylene) (PPV) films exchanging the counter-ion Cl of the poly(xylylidene tetrahydrothiophenium) (PTHT ) precursor polymer by Congo Red (CR) azodye. The objective of the present paper is to study the azodye photoisomerization trans→cis→trans process as a function of the PPV thermal annealing procedure. The LbL PTHT/CR films were thermally converted into LbL PPV/CR films at low (110°C) and conventional (230°C) temperatures, and characterized through both absorption and emission techniques. We found that the unexpected emission band above 650nm, attributed to the azodye, for LbL PPV/CR film thermally converted at lower temperature (110°C) is an evidence of the considerable decrease of CR degradation in the polymeric matrix. Emission anisotropy and selective photoluminescence were carried out to characterize qualitatively the exciton energy transfer. [Copyright &y& Elsevier]

Two novel poly( p-phenylene vinylene) (PPV) derivatives with conjugated thiophene side chains, P1 and P2, were synthesized by Wittig-Horner reaction. The resulting polymers were characterized by H-NMR, FTIR, GPC, DSC, TGA, UV-Vis absorption spectroscopy and cyclic voltammetry (CV). The polymers exhibited good thermal stability and film-forming ability. The absorption spectra of P1 and P2 showed broader absorption band from 300 to 580 nm compared with poly[( p-phenylene vinylene)-alt-(2-methoxy-5-octyloxy- p-phenylene vinylene)] (P3) without conjugated thiophene side chains. Cyclic voltammograms displayed that the bandgap was reduced effectively by attaching conjugated thiophene side chains. This kind of polymer appears to be interesting candidates for solar-cell applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Polyelectrolyte multilayers built via the layer-by-layer (LbL) method has been one of the most promising systems in the field of materials science. Layered structures can be constructed by the adsorption of various polyelectrolyte species onto the surface of a solid or liquid material by means of electrostatic interaction. The thickness of the adsorbed layers can be tuned precisely in the nanometer range. Stable, semiconducting thin films are interesting research subjects. We use a conducting polymer, poly(p-phenylene vinylene) (PPV), in the preparation of a stable thin film via the LbL method. Cyclic voltammetry and electrochemical impedance spectroscopy have been used to characterize the ionic conductivity of the PPV multilayer films. The ionic conductivity of the films has been found to be dependent on the polymerization temperature. The film conductivity can be fitted to a modified Randle's circuit. The circuit equivalent calculations are performed to provide the diffusion coefficient values. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the photoluminescence properties and the performance enhancement of organic light-emitting diodes (OLEDs) of a series of well-defined π-conjugated rigid rod oligomers analogous to poly(p-phenylenevinylene) (PPV). They are based on benzene-1,4-bis(phenylene vinylene) (OPPV) with electron-withdrawing (nitro) or electron-donating (methyl and dimethylamino) substituents in para-position of the terminal rings of the molecule. Substitution with methoxy and a long alkoxy group (hexadecyloxy) in 2,5-positions is also examined. Photoluminescence spectra obtained from films are discussed and compared to those previously reported in tetrahydrofuran solutions. OPPV oligomers were then used as emissive material in OLEDs and the I–V–L characteristics of the devices are presented. The results show that donating groups placed on the OPPV backbone increases the performances of the devices. [Copyright &y& Elsevier]

Abstract: Dopings of vaporized cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl) ethane (CMTE) into poly(methyl methacrylate) (PMMA), polystyrene, and polycarbonate were performed by a vacuum process, and the doping behaviors of CMTE were evaluated. Among the matrix polymers, PMMA was dispersed CMTE densely in its surface region. By using the CMTE-doped PMMA, we could fabricate a novel rewritable medium: a multi-layered film was prepared from over-coating of CMTE-doped PMMA onto poly(p-phenylene vinylene) (PPV) film, which set on a transparent substrate. Image storage could be performed upon irradiation at 365 nm at the side of CMTE/PMMA layer: color of the irradiated area changed a light yellow to a red due to photo-isomerization of CMTE. Next, upon irradiation at 365 nm at the side of the transparent substrate, PPV emitted a green fluorescence at around 530 nm, and the CMTE absorbed the emission from PPV causing image-erasure based on back-isomerization of CMTE. [Copyright &y& Elsevier]

Abstract: Proton exchange membranes based on Nafion/poly(p-phenylene vinylene) (PPV) composites were prepared by the heat treatment of a Nafion/PPV precursor, and investigated regarding their applicability for direct methanol fuel cells (DMFCs). The power density of MEA using Nafion/PPV composites was increased with increasing the PPV precursor concentration of the precursor solutions and reached 34mW/cm2, which is much greater than that using bare Nafion (∼26mW/cm2). The improved MEA performance was primarily due to a significant decrease in the methanol permeability with only a minimal loss of the ionic conductivity through the formation of PPV grains inside of the ionic channels and on the Nafion surface. The structure and properties of the Nafion/PPV composites were characterized by UV–vis spectroscopy, scanning electron microscopy, ion exchange capacity, water contact angle, and water uptake. [Copyright &y& Elsevier]

Abstract: Several oligomers analogous to poly(p-phenylene vinylene) (PPV) were synthesised by the Wittig reaction, to be used as model compounds for the study of structure/properties relationship. They are based on benzene-1,4-bis(phenylene vinylene) (OPPV) substituted by electron-withdrawing (nitro) or electron-donating (methyl and dimethylamino) groups on the terminal rings of the molecule. Moreover, two other oligomers 2-hexadecyloxy-5-methoxybenzene-1,4-bis(phenylene vinylene) (1-16-OPPV) and 2-hexadecyloxy-5-methoxybenzene-1,4-bis(4-dimethylaminophenylene vinylene) (1-16-NC-OPPV) were prepared with alkoxy groups on the central ring of the molecule. After a complete structural characterization by FTIR, 1H and 13C NMR, particular emphasis was placed upon the investigation of their thermal stability by TGA and their optical properties in tetrahydrofuran (THF) solutions. Depending on the substituent and on its position in the molecule a different thermal behaviour was observed. Moreover, a red-shift from 10 to 50nm was observed for the emission wavelength, with respect to unsubstituted OPPV. Several model compounds (with donating groups) exhibited high fluorescence quantum yields, from 51% to 68%. On the other hand, a very low yield was obtained for the oligomer with nitro groups, that was explained from semi-empirical calculations. These results showed promising properties for the incorporation of these oligomers in electroluminescent diodes. [Copyright &y& Elsevier]

Abstract: Poly(2-hexyloxy-5-((10-(4-(phenylazo)phenoxy)decyl)oxy)-1,4-phenylene vinylene) (HPA-10-PPV) is an azobenzene-functionalized poly(p-phenylene vinylene) derivative that previously has been shown to undergo changes in the position and shape of its fluorescence spectrum in response to trans → cis-azobenzene photoisomerization. This effect was initially observed in a binary dichloromethane-methanol solution and was attributed to a phototriggered expansion of polymer coil dimensions. In this report we explore the mechanism by which azobenzene isomerization induces this conformational change and the solvent properties that govern the magnitude of the change. Phototriggered fluorescence shifts are observed in mixtures of dichloromethane and each of 12 cosolvents, 7 protic and 5 aprotic. The shifts are largest in protic solvents but do not correlate with any single solvent parameter or combination of parameters. Smaller shifts are observed in mixtures with aprotic cosolvents, and the magnitude of these shifts correlates with solvent polarity/polarizability. The conformational changes responsible for the fluorescence shifts are attributed to a change in polymer–solvent interactions induced by the difference between properties of the trans- and cis-azobenzene isomers. Isomerization to the more polar cis-azobenzene promotes an increase in polymer–solvent interactions. These results suggest a means by which the magnitude of phototriggered fluorescence changes could be increased in future derivatives. [Copyright &y& Elsevier]

Abstract: We report on the thermal degradation characteristics of heat treated poly(p-phenylene vinylene) (PPV) films deposited using chemical vapor deposition. It was found that no decrease in the thickness of the films (110nm) occurred after isothermal heat treatment in vacuum at 450°C for up to 1h, while films treated at 500°C for 1h decreased to 70% of their original thickness. In situ mass spectrometry during heat treatment of the film at 500°C showed the release of significant amounts of material including toluene and xylene ion fragments. However, Fourier transform infrared spectroscopy shows no significant change in bond structure, indicating that the decrease in film thickness after heat treatment is due to release of material and densification, not crosslinking or bond breaking. [Copyright &y& Elsevier]

Abstract: Two series of poly(p-phenylene vinylene) and polyfluorene derivatives (PPV1–PPV4 and PF1–PF5) containing laterally attached penta(p-phenylene) mesogenes were synthesized and characterized. These polymers show nematic liquid crystalline behavior. The optical properties of the polymers were investigated by UV–vis absorption and photoluminescence spectrometers and these polymers were fabricated to form the polarized electroluminescent devices using poly(ethylenedioxythiophene)–poly(styrene sulfonic acid) (PEDOT–PSS) as an alignment layer. In the series of poly(p-phenylene vinylene) derivatives, polymer PPV4 offered the best EL device performance. It emitted yellow light at 588nm at 4V. The maximum brightness was about 1337cd/m2 at 9V with a polarized ratio of 2.6. In another series of polyfluorene derivatives, PF4 offered the best EL device performance with the polarized ratio of 12.4 and a maximum luminescence of 1855cd/m2. In the case of polarized white light, as a consequence of blending small amount of PF4 and PF5 with a host polymer PF2, polarized ratio of up to 10.2 and a maximum brightness of 2454cd/m2 have been attained. The aligned films exhibited pronounced polarized ratio, implying that the polymers exhibit potential for linearly polarized LED application. [Copyright &y& Elsevier]

Abstract: The elimination process of n-alkyl-sulphinyl precursor polymers towards conjugated poly[2-(3′,7′-dimethyloctyloxy)-5-methoxy-1,4-phenylene vinylene], or OC1C10-PPV, was studied with modulated temperature differential scanning calorimetry (MTDSC) and thermogravimetric analysis (TGA), with a focus on the subsequent reactions of the elimination products. The latter reactions were monitored using the non-reversing heat flow and the heat capacity (C p) measured in non-isothermal MTDSC experiments. The disproportionation reaction occurs in a temperature range between 85 and 135°C and is seen as an increase in C p. Water and elimination products released during the elimination reaction act as plasticizers and lower the T g. TGA experiments show that the temperature, film thickness, and the eliminated group play an important role on the diffusion and evaporation of the elimination products. The elimination products can further decompose and interact with the conjugated system to form undesirable crosslinks (network formation) in a temperature range of 140–160°C. [Copyright &y& Elsevier]

Abstract: Functional dyes could be dispersed into non-substituted poly(p-phenylene vinylene) (PPV), which shows a poor processability due to its insolubility and infusibility, by the vacuum process. Using this methods, it was possible to change the color of PPV from yellow to green with the blue dye, 1,4-(N,N′-diethylamino)anthraquinone (SV59). The fluorescence color of PPV could be changed from green to red by 2 min doping of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). Furthermore, a pattern doping with DCM could be carried out resulting in production of multicolored luminescent medium. [Copyright &y& Elsevier]

Functional dyes could be dispersed into non-substituted poly(p-phenylene vinylene) (PPV), which shows a poor processability due to its insoluble and infusible, by the vacuum process under the thermal equilibrium state without the structural damage of PPV. Using this methods, it was possible to change the color of PPV from yellow to green with the blue dye, 1,4-(N,N′-diethylamino)anthraquinone (SV59). The amount of SV59 doped into PPV increased with temperature and treatment time. The fluorescence color of PPV could be changed from green to red by 2 min doping of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). Furthermore, a pattern doping with DCM could be carried out resulting in production of multicolored luminescent medium. [ABSTRACT FROM AUTHOR]