Polarizing energy transfer in photoluminescent polymer blends

The occurrence of polarizing energy transfer in uniaxially oriented polymer blend films is investigated. A poly(2,5-dialkoxy-p-phenylene ethynylene) derivative (EHO-OPPE) and poly[2-methoxy-5-[2-ethyl-hexyloxy]-p-phenylene vinylene] (MEH-PPV) were used as the acceptors, and various sensitizers were used as donors. Some of the properties of the chromophores required for polarizing energy transfer to occur efficiently are elucidated, such as form-isotropy and thermal characteristics. The energy transfer efficiency is quantified, and for the present, optimized systems, values as high as 85% were demonstrated.     

Different thallium(III) oxide nano-structures from direct thermal decomposition of two thallium(I) coordination polymers

Two thallium(I) coordination polymers, [Tl(3-np)] and [Tl(2,4-dnp)], 3-np⁻ = 3-nitrophenoxide and 2,4-dnp⁻ = 2,4-dinitrophenoxide, have been synthesized and characterized by elemental analyses and IR spectroscopy. Flower-like nano-structure and nano-powders thallium(III) oxide, Tl₂O₃, have been prepared by direct thermal decomposition of two different Tl(I) coordination polymers, [Tl(3-np)] and [Tl(2,4-dnp)]. The nano-materials were characterized by scanning electron microscopy, X-ray powder diffraction (XRD) and IR spectroscopy. The thermal stability of nano-structure Tl₂O₃ was studied by thermal gravimetric and differential thermal analyses and showed that there is no reportable loss of weight in the TGA curves that proves the existence of thallium(III) oxide. This study demonstrates that coordination polymers may be suitable precursors for the preparation of nanoscale materials with different and interesting morphologies.     

Synthesis, characterization and fluorescence quenching of poly(fluorene-alt-enylenevinylene)s

Two poly(fluorine-alt-phenylenevinylene)s fluorescent conjugated polymers, poly(9,9-dioctylfluorene-alt-phenylenevinylene) (PFO/PPV1) and poly (fluorene-alt-2,5-dioctoxyphenylenevinylene) (PFO/PPV2), were obtained through a Heck polycondensation. The structures of the obtained polymers were characterized by FT-IR, ¹H-NMR and GPC. The thermal stabilities of the polymers were evaluated by TGA. The photophysical properties were studied by UV and photoluminescence (PL) spectroscopy both in solution and film. Their applications in the detection of nitro compounds were researched, and the results show high fluorescence quenching sensitivity of PFO/PPV1 towards nitro compounds such as 2,4-dinitrotoluene (DNT) and 4-nitrotoluene (p-NT) in solution and thin film.     

Synthesis and characterization of aromatic and aliphatic ether bridged polymers containing carbazole moieties

In this study, the polymers were synthesized ether bridged containing carbazole moieties via HBr elimination. Also, these polymers include the aliphatic chains at the different lengths and aromatic groups in their structures. However, the polymers were characterized by FT-IR, NMR and UV–vis spectroscopy, and their thermal stabilities were determined via TGA measurements. Fluorescence measurements were performed using N,N′-dimethyl formamide solutions and also, the optimization of the concentrations to obtain maximal emission intensity was investigated in N,N′-dimethyl formamide. The morphologic properties of the polymers were investigated at different particle sizes by using Scanning Electron Microscopy (SEM). Additionally, the number average molecular weight (M_n), weight average molecular weight (M_w) and polydispersity index (PDI) values of the polymers were determined by size exclusion chromatography (SEC) technique. Resultantly, the remarkable properties related to the fluorescence and thermal measurements of the polymers were obtained. Therefore, these polymers could be used in various application fields because of the fluorescent and thermal properties.     

Dielectric,thermal and mechanical properties of Sr<Subscript>2</Subscript>ZnSi<Subscript>2</Subscript>O<Subscript>7</Subscript> based polymer/ceramic composites

Polymer/Sr₂ZnSi₂O₇ (SZS) ceramic composites suitable for substrate applications have been developed using the polymers polystyrene (PS), high density polyethylene (HDPE) and Di-Glycidyl Ether of Bisphenol A (DGEBA). The dielectric, thermal and mechanical properties of the composites are investigated as a function of various concentrations of the ceramic filler. The obtained values of relative permittivity, dielectric loss tangent, thermal conductivity and coefficient of thermal expansion of the composites are compared with the corresponding theoretical predictions. The relative permittivity of the polymer/ceramic composites increases with filler loading. The dielectric loss tangent also shows the same trend except for DGEBA/SZS composites. The major advantages of the ceramic loading are improvement in thermal conductivity and a decrease in the coefficient of thermal expansion. The tensile strength of the composites decreases with increase in filler content, whereas an improvement is observed in microhardness. The variation of relative permittivity (at 1 MHz) of the composites is also studied as a function of temperature.     

Enhanced Charge Injection Properties of Organic Field‐Effect Transistor by Molecular Implantation Doping

Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large‐area fabrication. However, OSC devices still have to overcome contact resistance issues for better performances. Because of the Schottky contact at the metal–OSC interfaces, a non‐ideal transfer curve feature often appears in the low‐drain voltage region. To improve the contact properties of OSCs, there have been several methods reported, including interface treatment by self‐assembled monolayers and introducing charge injection layers. Here, a selective contact doping of 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) by solid‐state diffusion in poly(2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) to enhance carrier injection in bottom‐gate PBTTT organic field‐effect transistors (OFETs) is demonstrated. Furthermore, the effect of post‐doping treatment on diffusion of F₄‐TCNQ molecules in order to improve the device stability is investigated. In addition, the application of the doping technique to the low‐voltage operation of PBTTT OFETs with high‐k gate dielectrics demonstrated a potential for designing scalable and low‐power organic devices by utilizing doping of conjugated polymers.     

Synthesis,characterization and fluorescence quenching of poly(fluorene-alt-enylenevinylene)s

Two poly(fluorine-alt-phenylenevinylene)s fluorescent conjugated polymers, poly(9,9-dioctylfluorene-alt-phenylenevinylene) (PFO/PPV1) and poly(fluorene-alt-2,5-dioctoxyphenylenevinylene) (PFO/PPV2), were obtained through a Heck polycondensation. The structures of the obtained polymers were characterized by FT-IR, ¹H-NMR and GPC. The thermal stabilities of the polymers were evaluated by TGA. The photophysical properties were studied by UV and photoluminescence (PL) spectroscopy both in solution and film. Their applications in the detection of nitro compounds were researched, and the results show high fluorescence quenching sensitivity of PFO/PPV1 towards nitro compounds such as 2,4-dinitrotoluene (DNT) and 4-nitrotoluene (p-NT) in solution and thin film.     

Novel heterocyclic based blue and green emissive materials for opto-electronics

Two different novel heterocyclic compounds namely 2,5-bis(1,3-diphenyl-4,5-dihydro-1H-pyrazol-5-yl)thiophene (Material I) and 2,5-bis(3-(naphthalen-1-yl)-1-phenyl-4,5-dihydro-1H-pyrazol-5-yl)thiophene (Material II) were designed, synthesized and characterized by spectral methods. The synthesized materials were confirmed by standard techniques such as FT-IR, ¹H NMR and elemental analysis. Physical properties include thermal, surface morphology of the materials were explained from TGA, DSC and SEM analysis. Optical properties such as absorption, emission, solvent effect have been investigated by UV–Visible and fluorescence spectrophotometers. The blue and green emission of the materials was confirmed by using UV light as well as fluorescence spectrophotometers. Bandgap energies of these materials were obtained by both experimental and theoretical calculation from of cyclic voltammetry, UV–Visible spectrophotometer and DFT calculation. I–V characteristic analysis used to determine the threshold voltage (V_on) of the two materials. The obtained results of the materials have promising to be applicable for opto-electronic applications.     

含1,3,4-噻二唑环聚合物的合成及应用研究进展

含1,3,4-噻二唑环聚合物作为一类新型功能性的芳香杂环聚合物,由于其独特的储能性能、电催化活性、富电子特性而备受关注。近20年来对于含1,3,4-噻二唑环聚合物的研究从未间断,主要集中在材料的电化学合成和结构表征及其在可充电锂电池正极材料、生物化学传感器、临床诊断和药理学等领域的应用。电化学合成的方法有利于制备厚度可控的自支撑膜和对电极进行修饰,缺陷是造成电解液污染、成本高以及不适合规模化生产。研究者们尝试使用化学氧化聚合的方法来合成含1,3,4-噻二唑环聚合物,但除了2,5-二巯基-1,3,4-噻二唑聚合物可通过此方法成功合成外,主要得到的是一些配合物或配位聚合物。采用绿色的规模化的制备工艺来合成含1,3,4-噻二唑环聚合物是大势所趋。含1,3,4-噻二唑环聚合物的结构表征由于受到溶解性的限制,表征手段主要为X射线光电子能谱和红外(拉曼)光谱。2,5-二巯基-1,3,4-噻二唑聚合物由于具有高能量密度和高比容量而在二次锂电池正极材料的应用方面受到研究者们的青睐,但存在着充放电缓慢和电容量衰减快等缺陷。基于含1,3,4-噻二唑环聚合物修饰电极构建的传感器可高灵敏且高选择性地探测许多生物相关分子,但电极的稳定性有待改善。在所有的1,3,4-噻二唑环聚合物中,聚2-氨基-1,3,4-噻二唑(PAT)、聚5-氨基-1,3,4-噻二唑-2-硫醇或5-氨基-2-巯基-1,3,4-噻二唑(PAMT)以及聚2,5-二巯基-1,3,4-噻二唑(PBT)已通过电化学方法合成;PBT也在绿色的合成条件下采用化学氧化合成法合成得到,为其他1,3,4-噻二唑环聚合物的合成提供了借鉴,本课题组也通过化学氧化聚合法制备了PAT、PAMT和聚2-巯基-1,3,4-噻二唑(PTT)三类聚合物。目前,PBT作为二次锂电池正极材料研究得最多,其理论比容量高达362mAh/g,研究者们将PBT与聚吡咯、聚苯胺或水溶性磺化石墨烯等导电聚合物制成复合电极,进一步提高比容量和电极的稳定性并且加速充放电过程。基于含1,3,4-噻二唑环聚合物修饰电极构建的传感器在探测天然产物有效成分的含量、人和哺乳动物血液和体液或药品注射液中药物或代谢产物的含量、中药材或食品中的农药残留量以及水溶液中的重金属离子含量等方面取得了丰硕的成果;而将1,3,4-噻二唑环聚合物与全氟磺酸粘合剂、多壁碳纳米管复合可减少聚合物流失,从而起到增强电极稳定性和延长使用寿命的作用。本文归纳了1,3,4-噻二唑环聚合物研究进展,分别对1,3,4-噻二唑环聚合物的合成、结构表征途径及其应用等进行了介绍,分析了1,3,4-噻二唑环聚合物的研究中面临的问题并展望了其应用前景,以期为1,3,4-噻二唑环聚合物的制备工艺和功能拓展提供参考。     

Synthesis and properties of Na<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>CoO<Subscript>2</Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0.55, 0.89) oxide thermoelectrics

Na_xCoO₂ (x = 0.55, 0.89) sodium cobaltites have been prepared by solid-state reactions; their structural parameters have been determined; their microstructure has been studied; and their thermal (thermal expansion, thermal diffusivity, and thermal conductivity), electrical (electrical conductivity and thermoelectric power), and functional (power factor, thermoelectric figure of merit, and self-compatibility factor) properties have been investigated in air at temperatures from 300 to 1100 K. The results demonstrate that, with increasing sodium content, the electrical conductivity and thermoelectric power of the materials increase and their thermal conductivity decreases. As a result, the power factor and thermoelectric figure of merit of the Na_0.89CoO₂ ceramic at a temperature of 1100 K reach 0.829 mW/(m K²) and 1.57, respectively. The electron and phonon (lattice) contributions to the thermal conductivity of the ceramics have been separately assessed, and their linear thermal expansion coefficients have been evaluated.     

Thermo-mechanical characteristics of thermally aged polyethylene/polypropylene blends

Polyethylene (PE), polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications. Therefore, the current work has been carried out with the main objective of investigating the impact of the thermal aging/treatment and blend ratio (composition range) on the mechanical (tensile and hardness) and thermal characteristics (using thermogravimetric analysis in a dynamic air atmosphere) of PE, PP and PE/PP binary blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 wt.% were prepared via injection moulding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however, thermal aging at 100 °C has not affected the polymers hardness which holds also true for the tensile properties, showing a good correlation between tested mechanical properties. The thermogravimetric analysis (TGA) in a dynamic air atmosphere and derivative thermogravimetric analysis (DTA) were conducted to study the thermal degradation and stability of thermally unaged and aged PE, PP and PE/PP blends in terms of the initial (T_d and T_d(1%)) and final (T_d(99%)) decomposition temperatures and maximum decomposition rate temperature (T_max). All polymers start to decompose at no less than 365 °C. As for mechanical properties, the blend ratio has affected the thermal properties however, aging time has not.     

N-丁基吡咯与对苯二胺交替共聚物的合成与表征

以N,N′-二氯对苯醌二亚胺、N,N′-二氯-2,5-二甲基对苯醌二亚胺与N-丁基-2,5-二溴吡咯的格氏试剂通过二价镍配合物催化法合成了相应的交替共聚物,PNBuPAN和PNBuPDMAN,上述两种聚合物的产率分别为56.8%,52.6%。利用红外光谱、紫外-可见吸收光谱、循环伏安、凝胶色谱（GPC）等对所得聚合物的...     

Gas permeability of graphite foil modified with iron,cobalt, and nickel oxides

Graphite foils containing iron(III), cobalt(II), and nickel(II) oxides have been prepared via the impregnation of oxidized graphite in aqueous FeCl₃, Co(NO₃)₂, and Ni(NO₃)₂ solutions, followed by exfoliation via thermal shock and pressing of the resultant exfoliated graphite. The materials thus prepared have been characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. We have studied the gas transport properties of the modified graphite foil samples and observed a considerable increase in the nitrogen and hydrogen permeabilities of the metal oxide-modified graphite foils relative to the unmodified graphite foil. The thermal properties of the samples have been studied by thermogravimetry and differential scanning calorimetry. The results demonstrate that their oxidation onset temperature reaches 570°C.     

Preparation and properties of multi-walled carbon nanotube/poly(organophosphazene) composites

Carbon nanotubes (CNTs) are promising materials because of their unique properties. However, the poor solubility in solvents limits the function of CNTs and hinders their applications in many fields. Surface modification of CNTs with polymers is an efficient method to solve this problem. Several polymers were tested for the preparation of CNT dispersions. In comparison with organic polymers, poly(organophosphazenes) are highly stable macromolecules with adjustable properties which depend on the side groups. This article is to describe the synthesis of thermally stable and soluble multi-walled CNT/poly(organophosphazene) composites. The poly(organophosphazene)s substituted with (a) 100 % quaternary protonated pyridinoxy (PPY), (b) 50 % quaternary protonated pyridinoxy and 50 % a long aliphatic chain alcohol (1-dodecanol) (PDK), and (c) 50 % quaternary protonated pyridinoxy and 50 % a glycol ether [(2-(2-methoxyethoxy)ethanol] (PET) have been synthesized. f-MWCNT/poly(organophosphazene) composites have been prepared by the treatment of the functionalized multi-walled carbon nanotubes (f-MWCNT) with the protonated polyphosphazenes (PPY, PDK, and PET) using different feed ratios [R _feed = 1:1, 1:3, 1:5, 1:10 (w:w)]. The thermal stability of prepared composites (f-MWCNT/PPY, f-MWCNT/PDK, and f-MWCNT/PET) have been investigated by TGA. By considering thermal stabilities and solubility of all prepared composites, f-MWCNT/PPY_1:5, f-MWCNT/PDK_1:5, and f-MWCNT/PET_1:5 have been chosen as optimum composite composition and characterized by ³¹P NMR, ¹H NMR, XRD, Raman spectroscopy, and EDX analysis. The morphologic characterizations of the f-MWCNT/PPY_1:5, f-MWCNT/PDK_1:5, f-MWCNT/PET_1:5 nanocomposites have been carried out by HRTEM. Excellent dispersions of the nanocomposites in water and common organic solvents have been achieved. The solubility and thermal stability of nanocomposites depend on the side groups on poly(organophosphazene).     

Synthesis and characterization of poly(2,5-dimethoxyaniline) and poly(aniline-Co-2,5-dimethoxyaniline): The processable conducting polymers

Poly(2,5-dimethoxyaniline) (PDMOA) and its copolymers with aniline (PADMOA), which exhibit remarkably improved solubility in common organic solvents, were obtained by chemical polymerization, and characterized by a host of physical techniques. The lowering of the quinoid absorption in the IR spectra and the upshifting of the N_1s envelope in the XPS spectra indicate residual doping in the XPS polymers and thermal characteristic of the polymers provide evidence for hydrogen bonding, which appear to enhance the thermal stability of the homopolymer. These polymers are highly planar and conjugated, with well-developed polaronic features, shown by the XRD, ESR and UV-spectral data. The conductivity, however, is not high and apparently may be due to localization of polaronic charges at the hydrogen-bonding sites and the increased proportion of the insulating methoxy component in the polymer matrix.     

Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O₂TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O₂TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.     

Effect of annealing of poly(3-hexylthiophene)/fullerene bulk heterojunction composites on structural and optical properties

Composite films of P3HT/PCBM-(poly[3-2,5-diyl]/[6,6]-phenyl C₆₁ butyric acid methyl ester) are widely used as an active layer in plastic solar cells. We have studied the influence of thermal annealing on nano-structural and optical properties of thin spin-coated P3HT/PCBM-films. Their structural properties were studied by X-ray diffraction in grazing incidence geometry. It was found that the crystallinity of the investigated films is drastically increased upon annealing. Furthermore, the anisotropic dielectric function of such films was determined by spectroscopic ellipsometry. Significant changes were observed both in parallel and perpendicular components of the dielectric function after annealing. These changes were attributed to the formation of crystalline domains upon annealing.     

合成方法对导电高分子聚取代PPV性能的影响

采用４种不同方法合成了导电高分子聚（２，５－二甲氧基对苯乙炔）（ＰＰＶ），并对性能进行了研究。实验结果表明，不同合成方法影响前聚物的产率、分子量及其分布、以及微观结构。由４种方法所得导电聚合物的结构也有差别，由此影响产物的光致发光效率、导电率。并对合成方法的适用性进行了比较，筛选出适宜的方法以制备高质量的聚（２，５－二甲氧基对苯乙炔）。     

Synthesis and properties of novel chiral side-chain liquid crystalline polysiloxanes containing different chiral pendant groups

Two novel chiral liquid crystalline monomers, and a series of their corresponding chiral side-chain polymers (P₁–P₇) based on poly(methylhydrogeno)siloxane have been prepared. The chemical structures and liquid crystalline properties of the synthesized monomers and polymers have been investigated using various experimental techniques. Thermal analysis shows that all polymers have wide mesophase temperature ranges with a high thermal stability. With the increase of M₂ molar ratio in the polymer systems, the isotropic phase transition and glass transition temperatures of all polymers increase, and the temperature ranges of N* phase and mesophase become broad. The effect of cholesteryl mesogens on mesophase behaviors, optical properties, and molecular arrangement of LC polysiloxanes and their advanced applications have also been discussed. For homopolymer P₁, it shows a single S_A phase. With increasing the content of M₂ in the polymer systems, P₂ and P₃ reveal a S_A–N* phase transition when they are heated, and P₄–P₇ reveal a N* phase. For N* phase polymers P₄–P₇, the reflection wavelengths exhibit blue shift, suggesting that the pitch decreases with a decrease in the amount of the smectic domains induced by the M₁. The reflection wavelengths of P₄–P₇ are almost across the entire visible region when they are heated, which offer stremendous potential for various optical applications. For P₂ and P₃, the reflection wavelengths show a very steep change around the temperature of the S_A–N* phase transition, which can be used as thermally sensitive liquid crystal devices requiring fast response, such as sensors, and thermally induced tuning.     

Development of composites incorporating carbon nanofibers and nanotubes

Nanocomposites provide significantly increased modulus, thermal, and electrical properties when compared to traditional reinforced composites. Present work was undertaken to study the microstructure, thermal, and electrical properties of carbon nanostructured reinforced polymer matrix composites. Composites were made with carbon nanofibers and nanotubes (produced by CVD method) as reinforcement with thermoplastic polymers as matrices. The amount of nanoreinforcements was varied between 1 to 5 wt% in different matrices. The problems associated with dispersion of reinforcing materials have been studied. Dispersion of nanofillers in thermoplastics, microstructures, and thermal stability of the reinforced thermoplastics have been studied using SEM, DSC, and TGA. Experimental results show that small amount of carbon nanofillers present in thermoplastic matrix systems enhance the thermal, mechanical, and electrical properties of the composites.