Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Novel porphyrin‐grafted poly(phenylene vinylene) derivatives: Synthesis and photovoltaic properties

A series of novel porphyrin‐grafted poly (phenylene vinylene) derivatives, Porp‐RO‐PPV, were synthesized by a simple two‐step method. These copolymers contain conjugated poly(phenylene vinylene) derivatives as polymer backbone and covalently linked porphyrin units as side chain, which were confirmed by FTIR and ¹H NMR, and used for photovoltaic devices. The thermal, optical properties and sensitizing effect, and photovoltaic properties have been investigated. The emission spectra of Porp‐RO‐PPV copolymers revealed the existence of strong energy transfer from PPV backbone to porphyrin units. The energy conversion efficiency (η_e) of photovoltaic devices based on Porp‐RO‐PPV+PCBM reached 0.33% (78.2 mW/cm², AM1.5) and porphyrin units in the copolymers showed good sensitizing effect at low concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electroluminescence and photovoltaic properties of poly(p‐phenylene vinylene) derivatives with dendritic pendants

A copolymer of dendronized poly(p‐phenylene vinylene) (PPV), poly{2‐[3′,5′‐bis (2′‐ethylhexyloxy) bnenzyloxy]‐1,4‐phenylene vinylene}‐co‐poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylene vinylene] (BE‐co‐MEH–PPV), was synthesized with the Gilch route to improve the electroluminescence and photovoltaic properties of the dendronized PPV homopolymer. The polymer was characterized by ultraviolet–visible absorption spectroscopy, photoluminescence spectroscopy, and electrochemical cyclic voltammetry and compared with the homopolymers poly{2‐[3′, 5′‐bis(2‐ethylhexyloxy) benzyloxy‐1,4‐phenylene vinylene} (BE–PPV) and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH–PPV). Polymer light‐emitting diodes based on the polymers with the configuration of indium tin oxide (ITO)/poly(3,4‐ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/polymer/Ca/Al were fabricated. The electroluminescence efficiency of BE‐co‐MEH–PPV reached 1.64 cd/A, which was much higher than that of BE–PPV (0.68 cd/A) and a little higher than that of MEH–PPV (1.59 cd/A). Photovoltaic properties of the polymer were studied with the device configuration of ITO/PEDOT : PSS/polymer : [6,6J‐phenyl‐C₆₁‐butyric acid methyl ester] (PCBM)/Mg/Al. The power conversion efficiency of the device based on the blend of BE‐co‐MEH–PPV and PCBM with a weight ratio of 1 : 3 reached 1.41% under the illumination of air mass 1.5 (AM1.5) (80 mW/cm²), and this was an improvement in comparison with 0.24% for BE–PPV and 1.32% for MEH–PPV under the same experimental conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization, and photophysical properties of novel poly(p‐phenylene vinylene) derivatives with conjugated thiophene as side chains

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 ¹H‐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     

Micropatterning of poly(p‐phenylene vinylene) by femtosecond laser induced forward transfer

Conjugated polymers are important materials for optical applications, among which poly(p‐phenylene vinylene) (PPV) has a major role due to its applicability in sensors, organic light‐emitting diodes and large area displays. Despite advances on the synthesis of PPV‐based polymers and the improvements of their properties, its printing process, in particular involving the solid phase, remains unsuitable for the development of electro‐optical microcircuits. This paper demonstrates the printing of PPV from the solid phase in 2D micropatterns. Such an achievement was performed using laser induced forward transfer with femtosecond pulses, which allows area‐selective deposition within reduced scales as thin as ca 100 nm and 5 µm wide. Raman, fluorescence and electrochemical impedance spectroscopies confirm that the printed PPV micropatterns have the same structure, emission spectrum and conductivity as the target material, revealing the conservation of their original properties even after laser irradiation. The printing process was carried out using PPV films, overcoming the insolubility issue of this material. The optical and electrical characterization of the transferred PPV demonstrates the potential of this method for the patterning of electro‐optical microdevices, since luminescence and electrical conductivity were preserved. © 2018 Society of Chemical Industry     

Phase-transfer catalysed synthesis of disubstituted poly(phenylene vinylene)

An attempt to synthesize a series of phenyl ring disubstituted poly(o-, m- and p-phenylene vinylene) is reported. In this ‘one-pot’ reaction, a phase-transfer catalyst was used to promote the extraction of strong base deprotonated bischloromethyl aromatic anions from the aqueous to the organic phase to sustain a nucleophilic substitution reaction with the remaining bischloromethyl monomers. The polymers obtained were characterized for their chemical compositions and physical properties by elemental, i.r. and u.v. spectroscopic, and thermal analyses. The o-substituted polymers were found to have low melting temperatures, good solubilities and high molecular weights, but low yields. The m-substituted monomers, however, produced only non-conjugated poly-m-xylylenes. The p-substituted polymers offered the best combination of yield and physical properties. Films cast from soluble poly(2,5-dibutoxy-p-phenylene vinylene) have electrical volume resistivity in the range 300–500 ohm cm when doped with concentrated sulfuric acid.     

Synthesis and characterization of novel phenyl‐substituted poly(p‐phenylene vinylene) derivatives

Two novel phenyl‐substituted poly(p‐phenylene vinylene) derivatives, poly{2‐[3′,4′‐(2″‐ethylhexyloxy)(3″,7″‐dimethyloctyloxy)benzene]‐1,4‐phenylenevinylene} (EDP‐PPV) and poly{2‐[3′,4′‐(2″‐ethylhexyloxy)(3″,7″‐dimethyloctyloxy)benzene]‐5‐methoxy‐1,4‐phenylenevinylene} (EDMP‐PPV), and their copolymer, poly{2‐[3′,4′‐(2″‐ethylhexyloxy)(3″,7″‐dimethyloctyloxy)benzene]‐1,4‐phenylene‐vinylene‐co‐2‐[3′,4′‐(2″‐ethylhexyloxy)(3″,7″‐dimethyloctyloxy)benzene]‐5‐methoxy‐1,4‐phenylenevinylene} (EDP‐co‐EDMP‐PPV; 4:1, 1:1, and 1:4), were successfully synthesized according to the Gilch route. The structures and properties of the monomers and the resulting conjugated polymers were characterized with ¹H‐NMR, ¹³C‐NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, ultraviolet–visible absorption spectroscopy, and photoluminescence and electroluminescence (EL) spectroscopy. The EL polymers possessed excellent solubility in common solvents and good thermal stability with a 5% weight loss temperature of more than 380°C. The weight‐average molecular weights and polydispersity indices of EDP‐PPV, EDMP‐PPV, and EDP‐co‐EDMP‐PPV were 1.40–2.58 × 10⁵, and 1.19–1.52, respectively. Double‐layer light‐emitting diodes with the configuration of indium tin oxide/polymer/tris(8‐hydroxyquinoline)aluminum/Al devices were fabricated, and EDP‐co‐EDMP‐PPV (1:1) showed the highest EL performance and exhibited a maximum luminance of 1050 cd/m² at 19.5 V. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1259–1266, 2005     

Electrical and electroluminescent properties of poly(p-phenylene vinylene) LB films based LEDs using aluminum metal as the electrode

The electrical properties of poly(p-phenylene vinylene) (PPV) Langmuir-Blodgett (LB) films were investigated, wherein transparent indium-tin oxide (ITO) and aluminum (Al) were used as the electrodes. Their I–V characteristics depended strongly on the thickness of PPV LB film, and the electric conductivity of the PPV LB film was in the range of 10⁻²–10⁻¹⁵ (S/cm). Their C–V characteristics showed that the capacitance was reversibly proportional to the thickness of PPV LB film and was kept constant when the applied voltage changed from −1.0 V to +1.0 V. These results indicated that PPV LB film was an insulator in this range of applied voltage without doping. Under forward bias, yellow-green light emission was observed in PPV LB film based light emitting diodes (LEDs), the highest light emission reached more than 100 cd/m² in the case that PPV LB film was deposited for 80 layers, i.e. a ITO/PPV(80L)/Al device.     

Surface grafting of a poly(organophosphazene) onto poly(vinyl alcohol) and poly(ethylene-co-vinyl alcohol) using triethoxysilane as a coupling agent

Triethoxysilane HSi(OEt)₃ was used as coupling agent to graft a poly(organophosphazene) (POPZ) containing allylic functions to the surface of poly(vinyl alcohol) or poly(ethylene-co-vinyl alcohol) films. Hydrolyzed HSi(OEt)₃, which contained both inorganic (Si–OH) and organic (Si–H) reactivities, acted at the interface between the hydroxylated substrates (via a condensation reaction) and the allylic functions in POPZ (via a hydrosilylation reaction). Starting materials and grafting surfaces were studied by ATR-IR and XPS spectroscopies and contact angle measurements. Data obtained indicated that different POPZ layers were produced, depending on whether the functionalization of materials with silane, and the grafting reaction were separately or simultaneously made. The POPZ layer thickness was higher when the grafting reaction was preceded by the POPZ functionalization. In each cases, the modified surfaces showed marked increases in hydrophobicity character. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1965–1974, 1998     

超支化聚苯硫醚与线性聚苯硫醚的对比表征

以2,4-二氯苯硫酚为原料,采用一步法合成超支化聚苯硫醚。笔者运用红外光谱、拉曼光谱、荧光光谱、示差扫描量热分析、热重分析、广角X-射线衍射、溶解实验等分析手段,对超支化聚苯硫醚和线性聚苯硫醚的基本性能进行了对比。由于两者结构上的差异,使得两者表现出不同的特性。超支化聚苯硫醚具有三取代苯结构,具有很强的荧光效应、完全的不结晶、溶于有机溶剂、热降解温度低于线性聚苯硫醚约60℃等特性。广角X-射线衍射谱图也和结晶、无定型线性聚苯硫醚有很大不同。     

Shear-induced crystallization of poly(phenylene sulfide)

The crystalline morphology of poly(phenylene sulfide) (PPS) isothermally crystallized from the melt under shear has been observed by polarized optical microscope (POM) equipped with a CSS450 hot-stage. The shish–kebab-like fibrillar crystal structure is formed at a higher shear rate or for a longer shear time, which is ascribed to the tight aggregation of numerous oriented nuclei in the direction of shear. The crystallization induction time of PPS decreases with the shear time, indicating that the shear accelerates the formation of stable crystal nuclei. Under shear, the increase of spherulite growth rate results from highly oriented chains. The melting behavior of shear-induced crystallized PPS performed by differential scanning calorimetry (DSC) shows multiple melting peaks. The lower melting peak corresponds to melting of imperfect crystal, and the degree of crystal perfection decreases as the shear rate increases. The higher melting peak is related to the orientation of molecular chains. These oriented molecular chains form the orientation nuclei which have higher thermal stability than the kebab-like lamellae that are developed later. A new model based on the above observation has been proposed to explain the mechanism of shish–kebab-like fibrillar crystal formation under shear flow.     

The preparation and characterization of high‐performance and thermally stable electroluminescent poly(p‐phenylene‐vinylene‐b‐oligoethylene oxide)

Two luminescent block copolymers (PPVPEO₂₀₀ and PPVPEO₆₀₀), composed of poly(p‐phenylene‐vinylene) (PPV) segments with three phenylene vinylene units and poly(ethylene oxide) (PEO) segments with molecular weight of 200 and 600, respectively, have been successfully synthesized. The structures of the copolymers were verified using FTIR, ¹H‐NMR, and elemental analysis. Single‐layer polymer light‐emitting electrochemical cells (LEC) devices fabricated on the bases of thin films of PPVPEO₆₀₀ and on the bases of thin films of blends of PPVPEO₂₀₀ with additional PEO both demonstrated good electroluminescent (EL) performance with the onset voltage of 2.6 V and EL efficiency of 0.64 cd/A and 0.68 cd/A at 3.2 V, respectively. Thermal analysis shows that the decomposition temperature of PPVPEO₆₀₀ is about 305°C, which is higher than that of PPVPEO₂₀₀ and PEO. AFM studies of PPVPEO₆₀₀ thin films exhibits that the block copolymer self‐assembles to form nanoscale network structures with pseudo‐cross‐linking points, thus accounting for its high thermal stability and good EL performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1118–1125, 2007     

The preparation of microporous membranes from blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) and sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is a chemically resistant polymer and, therefore, an attractive material for the formation of membranes. However, membranes of unmodified PPO prepared by an immersion precipitation possess very low hydraulic permeabilities at the filtration processes. The membranes with higher hydraulic permeabilities can be prepared from sulfonated PPO and/or from blends of unsulfonated PPO and sulfonated PPO. In conclusion, the mechanism of the formation of membranes from blends of unsulfonated PPO and sulfonated PPO is suggested. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 161–167, 1999     

Synthesis and characterization of novel soluble alternating copoly(phenylene vinylene) derivative for light‐emitting electrochemical cell

A novel alternating copolymer, poly{[2,5‐di(2‐(2‐ethoxy ethoxy)ethoxy)‐1,4‐phenylene vinylene]‐alt‐1,4‐[phenylene vinylene]}, has been synthesized through the Wittig condensation as electroluminescent material. In this copolymer, one component is phenylene vinylene with flexible oligo(ethylene oxide) side chain that facilitates ion transportation and phase miscibility between nonpolar and polar part of composite luminescent layer, and another is a rigid phenylene vinylene moiety to improve luminescent quantum efficiency and tune color. The copolymer shows good solubility and thermal stability for device fabrication compared to poly(phpeylene vinylene)(PPV). The band gap value of copolymer is between those of corresponding homopolymers, which indicates that alternating copolymerization is a suitable way to obtain luminescent polymer with desired band gap. The maximum wavelength of photoluminescence of copolymer is 539 nm (yellowish‐green). The HOMO and LUMO energy levels obtained by cyclic voltammetry measurement indicate that the electron injection ability of copolymer has been greatly improved compared with that of the PPV. A more balanced carrier injection and higher quantum efficiency are proved by electroluminescent properties of corresponding light‐emitting devices. The turn‐on voltage of LEC device (ITO/copolymer + PEO + LiClO₄/Al) is found to be 2.3 V, with current comparative to LED (ITO/copolymer/Al) at 9.5 V. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1350–1356, 2003     

Synthesis and characterization of poly(1,5-naphthylene vinylene) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene)

Poly(1,5-naphthylene vinylene) (PNV) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) were synthesized via a liquid-solid two-phase reaction. The liquid phase was a tetrahydrofuran (THF) solution of the monomers, 1,4-bis(bromomethyl)-2-methoxy-5-(2-ethylhexyloxy)benzene (MOEHODCX) and 1,5-bis(bromomethyl) naphthalene (DBMN), and contained a certain amount of tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. The solid phase was potassium hydroxide particles with diameters smaller than 2 mm. The structures of the polymers were studied by infrared and Raman spectroscopies. The solutions of the copolymers emitted green light. The UV-vis and photoluminescence spectral bands of the copolymers showed blue shifts with the increase in their PNV contents. A polymer light-emitting diode was fabricated with the copolymer prepared by copolymerization MOEHODCX and DBMN with feeding molar ratio of 1:1, and its luminescence efficiency was measured to be 0.069.     

Hybrid transdermal drug delivery patch made from poly(p‐phenylene vinylene)/natural rubber latex and controlled by an electric field

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     

Crosslinkable poly(phenylene oxide) containing pendent 1,2-diphenylcyclopropane groups

Crosslinkable poly(phenylene oxide)s containing pendent 1,2-diphenylcyclopropane groups have been synthesized by oxidative polymerization from four new phenols containing the 1,2-diphenylcyclopropane group. The monomers were prepared by base-catalysed decomposition of the corresponding hydroxy-substituted 3,5-diphenyl-2-pyrazolines, which were the products of the reaction between hydroxy-substituted chalcones and hydrazine monohydrate. Characterization of and crosslinking studies on these polymers were carried out utilizing differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography and nuclear magnetic resonance. The polymers can be thermally cross-linked when heated to 350°C and the glass transition temperatures (T_g) of the polymers increase after crosslinking. The resulting crosslinked networks are insoluble in all solvents examined. Thermogravimetric analysis shows that no significant weight loss accompanies the crosslinking reaction.     

Investigation on the crystallization behavior of poly(ether ether ketone)/poly(phenylene sulfide) blends

The morphology of nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with poly (ether ether ketone) (PEEK) have been observed by polarized optical microscope (POM) equipped with a hot stage. The nonisothermal crystallization behavior of PPS and PEEK/PPS blend has also been investigated by differential scanning calorimetry (DSC). The maximum crystallization temperature for PEEK/PPS blend is about 15°C higher than that of neat PPS, and the crystallization rate, characterized by half crystallization time, of the PEEK/PPS blend is also higher than that of the neat PPS. These results indicate that the PEEK acts as an effective nucleation agent and greatly accelerates the crystallization rate of PPS. The Ozawa model was used to analyze the nonisothermal crystallization kinetics of PPS and its blends. The Avrami exponent values of neat PPS are higher than that of its blend, which shows that the presence of PEEK changed the nucleation type of PPS from homogeneous nucleation to heterogeneous nucleation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Molecular weight determination of poly(phenylene sulfide ether)

Poly(phenylene sulfide ether) and poly(phenylene sulfoxide ether sulfide ether) (PPSOESE) were successfully prepared and their structures were proved by several analytical techniques in the present work. The molecular weight (MW) of PPSOESE, a soluble polymer in common organic solvent at room temperature, was determined by gel permeation chromatography. Based on the conversion reaction of the two polymers, the MW of PPSE was calculated and correlated with its intrinsic viscosity. As a result, the Mark‐Houwink equation for PPSE was concluded. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development and characterization of homogeneous membranes prepared from sulfonated poly(phenylene oxide)

This article investigates the comprehensive properties of sulfonated poly(phenylene oxide) (SPPO) membranes with different sulfonation degrees and presents the completion of previous work necessary for the application of SPPO membranes to proton‐exchange membrane fuel cells. The sulfonation level has been accurately determined by conductometric titration and ¹H‐NMR, and the glass‐transition temperature has been obtained with both differential scanning calorimetry and dynamic mechanical thermal analysis. Sulfonic groups attached to the aromatic ring in the poly(phenylene oxide) backbone split at 220–340°C, but the main‐chain splitting temperature of SPPO is similar to that of the pure polymer. In addition, the effects of sulfonic groups and water on the tensile strength of these membranes have been studied. An increase in the sulfonate groups in the polymer results in an increase in the water uptake. Atomic force microscopy phase images of the acid‐form membranes clearly show the hydrophilic domains, and the ionic regions of the membranes with a low sulfonation degree are isolated and become connected to produce a cocontinuous morphology as the degree of sulfonation increases. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1244–1250, 2005