Fast response single‐ion transport light‐emitting electrochemical cell based on PPV derivative

We present the electrical and optical characteristics of a single‐ion transport light‐emitting electrochemical cell (SLEC) based on poly(p‐phenylene vinylene) (PPV) derivative containing aryl‐substituted oxadiazole in the backbone (MEH‐OPPV). Ionized polyurethane–poly(ethylene glycol) (PUI) used as polymer electrolyte is introduced into the active layer of the SLEC. The turn‐on voltage of the SLEC is about 3 V according to its current density–voltage (J–V) characteristics. The response time of the SLEC is less than 10 ms, lower than that of normal LECs by two orders of magnitudes roughly. The reasons of the quick response for the SLEC are discussed in the article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4253–4255, 2006     

Preparation and characterization of thin films of the poly(p‐phenylene vinylene) semiconducting polymer

Conjugated polymers have been the subject of many studies because of their widespread applications in electronic and optoelectronic devices. Poly(p‐phenylene vinylene) is a leading semiconducting polymer in optical applications. This work is focused on the development of thin films of poly(p‐phenylene vinylene) by spin coating and their characterization with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy to understand their changes. An empirical model has been developed to show the effect of the variables—the spin speed, polymer concentration, and spin time—on the film thickness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Controlling the photoluminescence of water‐soluble conjugated poly[2‐(3‐thienyl)ethyloxy‐4‐butylsulfonate)] for biosensor applications

The photoluminescence of poly[2‐(3‐thienyl)ethyloxy‐4‐butylsulfonate)] (PTE‐BS) in aqueous solution increases threefold on addition of the surfactant tetrabutylammonium perchlorate (TBA). Furthermore, the luminescence of the PTE‐BS/TBA system is reduced by more than five times by the addition of small amounts of the cationic electron acceptor methyl viologen (MV²⁺). The Stern–Volmer constant K_SV = 1.4 × 10⁴ L mol^?1 for the quenching of the polymer–surfactant complex by MV²⁺ is approximately 60 times smaller than the K_SV = 8.4 × 10⁵ L mol^?1 obtained in water polymer solutions without surfactant. Thus, the luminescence of PTE‐BS in aqueous solution can be modulated by complexing the polymer either with a surfactant or with a quencher. In this contribution we show that the surfactant/quencher tuning effect found in polymers of the phenylenevinylene family, such as poly(2,5‐methoxy‐propyloxysulfonate phenylenevinylene), also appears in polymers of the thiophene family such as PTE‐BS. Copyright © 2007 Society of Chemical Industry     

New fluorene–pyrazino[2,3‐g]quinoxaline‐conjugated copolymers: Synthesis,optoelectronic properties,and electroluminescence characteristics

New donor–acceptor conjugated copolymers called poly}2,7‐(9,9′‐dihexylfluorene)‐co‐5,10‐[pyrazino(2,3‐g)quinoxaline]{s or PFPQs [where F represents the 2,7‐(9,9′‐dihexylfluorene) moiety and PQ represents the 5,10‐(pyrazino[2,3‐g]quinoxaline) moiety], synthesized by the palladium‐catalyzed Suzuki coupling reaction, are reported. The PQ contents in the PFPQ copolymers were 0.3, 1, 5, and 50 mol %, and the resulting copolymers were named PFPQ0.3, PFPQ01, PFPQ05, and PFPQ50, respectively. Absorption spectra showed a progressive redshift as the PQ acceptor content increased. The relatively small optical band gap of 2.08 eV for PFPQ50 suggested strong intramolecular charge transfer (ICT) between the F and PQ moieties. The photoluminescence emission peaks of the PFPQ copolymer films also exhibited a large redshift with enhanced PQ contents, ranging from 551 nm for PFPQ0.3 to 592 nm for PFPQ50. However, the PFPQ copolymer based electroluminescence (EL) devices showed poor device performances probably due to the strong confinement of the electrons in the PQ moiety or significant ICT. This problem was resolved with a binary blend of poly[2,7‐(9,9‐dihexylfluorene)] (PF) and PFPQ with a volume ratio of 95/5 (BPQ05). Multiple emission peaks were observed at 421, 444, 480, 516, and 567 nm in the BPQ05‐based EL devices because the low PQ content led to incomplete energy transfer. The Commission Internationale de L'Eclairage 1931 coordinates of the BPQ05‐based EL device were (0.31, 0.32), which were very close to the standard white emission of (0.33, 0.33). Furthermore, the maximum luminescence intensity and luminescence yield were 524 cd/m² and 0.33 cd/A, respectively. This study suggested that a pure white light emission was achieved with the PFPQ copolymers or PF/PFPQ blends through the control of the energy transfer between F and PQ. Such PFPQ copolymers or PF/PFPQ blends would be interesting for electronic and optoelectronic devices. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of thermal annealing on the mechanical and thermal properties of polylactic acid–cellulosic fiber biocomposites

Polylactic acid (PLA) biocomposites were produced by a combination of extrusion and injection molding with three cellulosic reinforcements (agave, coir, and pine) and contents (10, 20, and 30%). In particular, some samples were subjected to thermal annealing (105 °C for 1 h) to modify the crystallinity of the materials. In all cases, morphological (scanning electron microscopy) and thermal (differential scanning calorimetry, dynamical mechanical thermal analysis) characterizations were related to the mechanical properties (Charpy impact, tensile and flexural tests). The results showed that annealing increased the crystallinity for all the materials produced, but different mechanical behaviors were observed depending on fiber type and content. For example, annealing increased the impact strength and flexural modulus of PLA and PLA biocomposites (agave, coir, and pine), while decreasing their flexural strength. But the main conclusion is that fiber addition combined with thermal annealing can substantially increase the thermal stability of the studied materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43750.     

Synthesis and characterization of a kind of poly(3‐butylthiophene methine) with azo side groups

To enhance the third nonlinear optical properties of poly(thiophene methine), we synthesized a new kind of poly(3‐butylthiophene methine) with azo side groups: poly[(3‐butylthiophene‐2,5‐diyl)‐p‐(N,N‐dimethylamino)azobenzylidenequinomethane] (PBTDMABQ). PBTDMABQ and its intermediate product were characterized with IR, ultraviolet–visible, and ¹H‐NMR spectroscopy. The band gaps of PBTDMABQ were calculated to be 1.94 and 2.06 eV with two different models. The thermal stability, determined by thermogravimetric analysis, indicated that PBTDMABQ decomposed above 345°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1261–1265, 2005     

Polymeric coatings for photostability enhancement of poly(p‐phenylene vinylene) derivative films

Poly(p‐phenylene vinylene) (PPV) derivatives are an important class of conjugated polymers, known for their applications as electroluminescent materials for light‐emitting devices and sensors. These derivatives are highly susceptible to photodegradation by the combined action of oxygen and light. Here, the use of various commercial polymers as protective coatings against the photodegradation of PPV derivatives was explored. Cast films of two similar PPV derivatives, poly[(2‐methoxy‐5‐n‐hexyloxy)‐p‐phenylene vinylene] and poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐p‐phenylene vinylene], were submitted to photodegradation by exposure to white light under atmospheric conditions in order to verify if the type of side chain (linear or branched) had an effect on the photodegradation. No significant differences in the photodegradation behaviour between the two polymers were noticed. The following commercial polymers were tested as protective coatings for the PPV derivative cast films: 99 and 80% hydrolysed poly(vinyl alcohol) (PVA) and starch. The best results were achieved using coatings of 99% hydrolysed PVA, which increased about 700 times the time necessary for complete degradation of the PPV derivative films. The results show the effectiveness of this coating in minimizing and, possibly, controlling the effects of the photodegradation of PPV derivative films, which can be useful in many applications, e.g. oxygen sensors. Copyright © 2009 Society of Chemical Industry     

Optical properties of MEH‐PPV conjugated polymer covered by silica nanoshells

Poly [2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] (MEH‐PPV) covered by nanostructured silica shells were synthesized via sol–gel process and investigated after freeze‐drying and heat‐drying in vacuum. The freeze‐dried sample consists of a light pink powder while the heat‐dried sample presents a redder coarse‐grained material. The freeze‐dried sample was analyzed using small angle X‐ray scattering (SAXS). Both samples were analyzed using photoluminescence (PL) and Raman spectroscopy at room temperature. The PL spectra presented relatively large red shifts compared with that of the MEH‐PPV in tetrahydrofuran solution, which was taken as a reference sample. The energy shifts observed in the PL and Raman spectra strongly support an explanation based on denser packing conditions inside the nanostructured silica shells, which can effectively lead the polymer molecules to a higher interchain interaction via aggregate sites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5620–5626, 2006     

Synthesis and properties of polyether with short alternating conjugated and nonconjugated blocks containing oxadiazole units

A polyether, poly[(2,5‐dimethylene‐1,3,4‐oxadiazole)dioxy‐1,4‐phenylene‐1,2‐ethenylene‐1,4‐phenylene‐1,2‐ethenylene‐1,4‐phenylene], based on short alternating conjugated oxadiazole units, has been synthesized, which is a kind of PPV derivative that emits blue light. The resulting polymer is fairly soluble in chloroform. The synthesized polymer shows a UV–visible absorbency maximum wavelength around 310 nm in solution. The photoluminescence maximum wavelength for the resulting polymer appears around 470 nm. The polymer also exhibits good thermal stability up to 300°C under N₂ atmosphere. It is also observed that the onset temperature of thermal decomposition is as high as 355°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2682–2686, 2002     

Effect of annealing on electrical conductivity and morphology of polyaniline films

We report structure–property relationships of polyaniline emeraldine base (EB) films that were produced by combining different processing steps in various sequences. The effect of annealing and doping processes on the surface structure of the films was investigated by atomic force microscopy (AFM), and the corresponding changes to the chemical structure of the EB films were monitored by Fourier transform infrared spectroscopy. AFM results indicate that after doping polyaniline (EB) films with HCl, the root mean square (rms) roughness of the surface of EB film increased ～ 46%. When the doped films were annealed at 180°C under a nitrogen atmosphere for 3 h, the rms roughness was essentially unchanged from that of the initial, undoped films. The electrical conductivity of the films also showed a significant dependence on the processing sequence. When the doped polyaniline (EB) films were annealed, no electrical conductivity was observed. When these films were redoped, only ～ 6% of the initial conductivity could be recovered. In another processing sequence in which the polyaniline (EB) films were first annealed and then doped, the electrical conductivity was only ～ 12% relative to the film that was doped immediately after being cast. From this work, a strategy to reduce the surface roughness of films made from electrically conducting polyaniline (EB) is proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3602–3610, 2001     

Effects of solution processing on the photovoltaic response of poly(n‐vinyl carbazole) films

The effects of solution processing on the photovoltaic response of poly(n‐vinyl carbazole) (PVK) films were investigated. PVK films were formed by spincasting onto glass coated with indium tin oxide (ITO) and poly(3,4‐ethylenedioxythiophene) (PEDOT)–polystyrenesulfonate (PSS). Some of the PVK films were redissolved in chlorobenzene and redried in the absence or presence of an electric field. Illuminated current–voltage characteristics were measured for an ITO/PEDOT:PSS/PVK/Ca:Al device. Films spincast from a 50 mg/mL solution, redissolved, and dried in the absence of the electric field exhibited a 26% higher charge collection efficiency than films dried in the presence of the electric field. The increased charge collection efficiency was attributed to changes in the molecular configuration of the PVK films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface,interface and electronic properties of F8:F8BT polymeric thin films used for organic light‐emitting diode applications

Ultrathin polymeric films consisting of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (F8) blended with poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT) grown onto PEDOT:PSS/ITO/PET were investigated by X‐ray photoelectron spectroscopy (XPS), depth‐profiling XPS, reflection electron energy loss spectroscopy (REELS) and angle‐dependent X‐ray absorption spectroscopy (XAS) to gain information on the films' electronic, order and interface properties. AFM studies provide valuable information on the films' nanotopographical properties and homogeneity. Spectroscopic ellipsometry and photoluminescence spectroscopy were used also to obtain information on the optoelectronic properties. Well‐ordered films were observed from the XAS analysis, measured at the sulfur K absorption edge. XPS measurements demonstrated that the surface composition of the polymer thin films prepared by a spin‐coating wet‐chemical deposition method matches the expected F8:F8BT blend stoichiometry. The interfacial properties were studied through an argon ion sputtering process coupled to the XPS acquisition, showing an enhancement of oxygen components at the interface. The films' inhomogeneity was verified by AFM images and analysis. We obtained a value of 3.1 eV as the electronic bandgap of the F8:F8BT film from REELS data, whereas analysis of the spectroscopic ellipsometry spectra revealed that the optical bandgap of F8:F8BT has a value of 2.4 eV. A strong green emission was obtained for the produced films, which is in agreement with the expected emission due to the 1:19 ratio of the F8 and F8BT blended polymers. © 2018 Society of Chemical Industry     

Electrical properties of poly(p‐phenylene vinylene) films with an incorporation of platinum metal nanoparticles

The effects of platinum metal nanoparticles on a conjugated polymer were investigated by monitoring the electronic structures and measuring the electrical properties of poly(p‐phenylene vinylene) (PPV) and PPV/Pt nanocomposites films. Enhanced current density in PPV/Pt nanocomposite films was obtained by the incorporation of Pt nanoparticles into the conjugated polymer PPV. This result agrees well with our observation of an increase in the electron affinity and an increase in roughness with increasing Pt nanoparticle content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Laser annealing and surface modification of plasma polymer-metal composite films

Plasma polymer films with encapsulated metal particles were prepared by simultaneous plasma polymerization and metal evaporation. Laser annealing (Nd-YAG, 1064 nm) causes dramatic changes in the particle size and shape without material ablation, but with changes in the surface topography. This results in changes in the optical plasma resonance absorption, as demonstrated by UV-visible-near-infrared (NIR) spectroscopy. The invariable transmission in the UV region of the plasma polymer matrix after laser annealing confirms that there is no material ablation. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) demonstrated particle size changes and modifications of the plasma polymer surface due to laser annealing.     

Effect of annealing on SiC thin films prepared by pulsed laser deposition

Crystalline cubic SiC thin films were successfully fabricated on Si(100) substrates by using laser deposition combined with a vacuum annealing process. The effect of annealing conditions on the structure of the thin films was investigated by X-ray diffraction and Fourier transform infrared spectroscopy. It was demonstrated that amorphous SiC films deposited at 800°C could be transformed into crystalline phase after being annealed in a vacuum and that the annealing temperature played an important role in this transformation, with an optimum annealing temperature of 980°C. Results of X-ray photoelectron spectroscopy revealed the approximate stoichiometry of the SiC films. The characteristic microstructure displayed in a scanning electron microscope image of the films was indicative of epitaxial growth along the (100) plane.     

Uniaxially aligned poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] thin films characterized by the X‐ray diffraction pole figure technique

Aligned thin films of the liquid‐crystalline polymer poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] were prepared, and the correlation between the optical anisotropy and the structural properties was shown. A series of samples with different thicknesses were prepared via a spin‐casting process on rubbed polyimide surfaces. The alignment of the polymer chains was obtained by a temperature treatment just below the clearing temperature. The degree of alignment was investigated with ultraviolet–visible absorption spectroscopy and in‐plane X‐ray diffraction. Independently, each technique revealed Hermans orientation functions in the range of 0.75–0.8. Surprisingly, a layer‐thickness dependence was not observed. In addition, the X‐ray diffraction pole figure technique revealed that the polymer chains were uniaxially aligned along the rubbing direction. The aligned films were in the nematic state, with the director elongated along the rubbing direction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of annealing on UV-visible absorption and photoluminescence behavior of liquid phase deposited TiO2 nanorods

In this work, anatase and rutile TiO₂ nanorods were fabricated using one-step liquid phase deposition process, followed by heat treatment in the range 300-800°C. The direct and indirect band gap of the TiO₂ nanorods was estimated form optical absorption data which illustrated a red shift at higher temperatures owing to the different nature of excitons in anatase and rutile phases. The photoluminescence (PL) spectra revealed the presence of two main emission bands consisting of four peaks. It was found that two high-energy peaks located at 2.95-3.30 eV could be generated from exciton transitions from the conduction band to the valence band of TiO₂ nanorods, while two low-energy peaks located at 2.43-2.64 eV may arise from surface state transitions. The PL intensity firstly increased with temperature and at 500°C reached a maximum value, then decreased through increasing temperature up to 800°C. These variations in the intensity of PL emission could be explained in terms of changes in phase structure, crystallinity, and amount of the oxygen vacancies, which are all dependent to the annealing temperature based on X-ray diffractometer and X-ray photoelectron spectrometer studies. These results indicated that annealing temperature allows to manipulate the properties of TiO₂ nanorods for opto-electronic applications.     

Synthesis and characterization of new anthracene‐based semiconducting polyethers

New anthracene‐based polyethers, anthracene/bisphenol A (An–BPA) and anthracene/fluorinated bisphenol A (An–BPAF), were synthesized and characterized. An–BPA and An–BPAF were fully soluble in common organic solvents and had number‐average molecular weights of 2580 and 3240, respectively. The optical properties of the polymers were investigated with ultraviolet–visible absorption and photoluminescence spectroscopy. Blue photoluminescence was observed in dilute solutions. In solid thin films, π–π interactions influenced the optical properties, and redshifted photoluminescence spectra were obtained; a green emission (504 nm) for An–BPAF and a green‐yellow emission (563 nm) for An–BPA were found. By cyclic voltammetry, the electrochemical band gap was estimated to be 2.72 and 3.05 eV for An–BPA and An–BPAF, respectively. Single‐layer diode devices of an indium tin oxide/polyether/aluminum configuration were fabricated and showed relatively low turn‐on voltages (3.5 V for An–BPA and 3.7 V for An–BPAF). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of titanium dioxide optical films by sol–gel processes

The main purpose of this study is to synthesize the front panel of monitor with a high refractive index optical film. Our experiment uses titanium dioxide nanoparticles mixed with methyl methacrylate (MMA), 2‐hydroxyethyl methacrylate (2‐HEMA), and tri(ethylene glycol) dimethacrylate (TEGDMA) of the wet type and economical sol–gel production process. Our product has a superior mechanical, thermal, and optical properties was demonstrated by Fourier transform infrared spectrum (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UV/visible spectrum, and Spectro Ellipsometer. In addition, we found the surface of the two series of thin film with the organic and inorganic high refractive index (TiO₂) mixed materials, has high transmittance for visible light above 90%, refractive index <1.65 and the hardness test 6H. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2271–2280, 2007     

Electrodeposition of iron–palladium thin films

FePd thin films were electrodeposited from ammonium citrate complex baths. The effects of various electrodeposition and post heat treatment conditions including pH, current density, bath concentrations, substrates and annealing temperature on composition, material, and magnetic properties were systematically investigated. In these baths, the deposited iron content increased linearly with an increase in current density from 1 to 5 mA cm⁻² producing films with compositions extending from Fe₇Pd₉₃ to Fe₉₁Pd₉. Magnetic saturation (M_S) of electrodeposited FePd thin films linearly increased with increase in deposited iron content (i.e. 1.8 T for Fe₈₂Pd₁₈ and 0.1 T for Fe₁₉Pd₈₁) which is similar to its bulk counterparts. The effects of post-heat treatment on the phase and crystal structure of near equiatomic FePd electrodeposits (i.e. Fe₄₈Pd₅₂) was investigated by subjecting electrodeposits to different annealing temperatures from 400 to 600 °C under reducing environment. L1₀ FePd phase was formed from nanocrystalline FePd solid solution and the crystallinity improved with increasing annealing temperatures.