New semi-conducting poly(phenylene vinylene-alt-anthrylene vinylene)s: Synthesis,characterization and photophysical properties

An anthracene-based semi-conducting polymer (P1) and its cyano-analogue (P2) were synthesized via the Wittig and Knoevenagel polycondensations. The polymers were soluble in common organic solvents and have number-average molecular weights of 13,750 and 6430 g mol⁻¹ for P1 and P2, respectively. The DSC analyzes show a good thermal stability and an amorphous morphology in solid state for these organic materials. The optical properties of the polymers were investigated by UV–visible absorption and fluorescence spectroscopies. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis. The effect of cyano group on the photophysical properties of poly(phenylene vinylene-alt-anthrylene vinylene)s was investigated. The results demonstrate an enhancement in the ionization potential and a significant improvement of the fluorescence yield due to introduction of such groups into the π-conjugated system. Single-layer diodes based on these organic semiconductors have been fabricated and showed relatively low turn-on voltages.     

Pure blue light-emitting fluorene-based conjugated polymer with excellent thermal, photophysical, and electroluminescent properties

A functionalized polyfluorene (FPF) with dendritic carbazole and oxadiazole side chains have been successfully designed, synthesized, and characterized. The weight-average molecular weight (M _w) and number-average molecular weight (M _n) were measured by gel permeation chromatography (GPC) to be 71280 and 31185, respectively. The FPF is thermally stable with high decomposition temperature (T _d = 495 °C) and glass transition temperature (T _g = 160 °C), and show good solubility in organic solvents, such as N,N-dimethyl formamide, tetrahydrofuran, CHCl₃, and toluene. The photoluminescent and electroluminescent (EL) emissions and Commission Internationale de L’Eclairage coordinates indicated pure blue light emission of FPF and its device. The luminance–voltage (L–V) and current density–voltage (J–V) characteristics of the devices based on FPF indicated typical diode characteristics with a maximum luminance of 980 cd/m² at a drive voltage of 13.0 V, a maximum current density of 726 mA/cm², and a turn-on voltage of 8.54 V. The maximum EL efficiency of the device based on FPF was measured to be 0.46 % at the current density of 12.5 mA/cm². These results indicate that the FPF polymer could be a promising candidate for pure blue light-emitting polymer with excellent thermal, photophysical, and electroluminescent properties.     

Synthesis, characterization, photophysical properties of a novel organic photoswitchable dyad in its pristine and hybrid nanocomposite forms

In the present paper the method of synthesis and characterization of a novel organic dyad, 3-(1-Methoxy-3,4-dihydro-naphthalyn-2-yl-)-1-p-chlorophenyl propenone, have been reported. In this paper our main thrust is to fabricate new hybrid nanocomposites by combining the organic dyad with different noble metals, semiconductor nanoparticle and noble metal-semiconductor core/shell nanocomposites. In this organic dyad, donor part is 1-Methoxy-3, 4-dihydro-naphthalen-2-carboxaldehyde with the acceptor p-chloroacetophenone. We have carried out steady state and time-resolved spectroscopic measurements on the dyad and its hybrid nanocomposite systems. Some quantum chemical calculations have also been done using Gaussian 03 software to support the experimental findings by theoretical point of view. Both from the theoretical predictions and NMR studies it reveals that in the ground state only extended (E-type or trans-type) conformation of the dyad exists whereas on photoexcitation these elongated conformers are converted into folded forms (Z- or cis-type) of the dyad, showing its photoswitchable character. Time resolved fluorescence spectroscopic (fluorescence lifetime by TCSPC method) measurements demonstrate that in chloroform medium all the organic-inorganic hybrid nanocomposites, studied in the present investigation, possess larger amount of extended conformers relative to folded ones, even in the excited singlet state. This indicates the possibility of slower energy destructive charge recombination rates relative to the rate processes associate with charge-separation within the dyad. It was found that in CHCl3 medium, the computed charge separation rate was found to be approximately 10(8) s(-1) for the dyad alone and other hybrid nanocomposite systems. The rate is found to be faster than the energy wasting charge recombination rate approximately 10(2)-10(1) s(-1), as observed from the transient absorption measurements for the corresponding hybrid systems. It indicates the conformational geometry has a great effect on the charge-separation and recombination rate processes. The suitability for the construction of efficient light energy conversion devices especially with Ag-Dyad nanocomposite of all the systems studied here is hinted from the observed long ion-pair lifetime.     

Thermal, photophysical, and electrochemical characterization of a conjugated polyazomethine prepared by anodic electropolymerization of a thiophenoazomethine co-monomer

A novel conjugated azomethine co-monomer consisting uniquely of thiophenes is presented, which was prepared by a simple condensation reaction in the absence of solvent. The conjugated thiophenoazomethine triad sustained anodic electropolymerization to afford a conjugated polymer that was deposited as a thin film onto a transparent ITO electrode. The resulting polymer undergoes unprecedented reversible radical cation formation in addition to a reduction, illustrating its p- and n-type character. The measured spectroscopic properties showed that the polymer is conjugated with a low band-gap ca. 1.5 eV and its excited state energy is dissipated by nonradiative means.     

Synthesis and photophysical properties of two-photon absorbing spirofluorene derivatives

New spirofluorene-based quadrupolar two-photon absorbing dyes having triphenylamine and N,N-dibutylaniline as electron donors at the end of molcules were designed and synthesized. The third-order nonlinear optical properties of these compounds were studied using a two-photon excited fluorescence method. They were found to have high two-photon absorption cross-section owing to extended conjugation of the spirofluorene moiety. The effect of varying the donor strength could be discerned by comparing the two compounds. They were successfully used as a photosensitizers for two-photon initiated polymerization of three-dimensional micro-objects.     

Novel metallomesogenic polyurethanes: Synthesis,characterization and properties

A series of tetradentate Schiff base metallomesogenic diols were synthesized from two simple dihydroxy benzenes. The metallomesogenic diol was constructed from three ring containing mesogen linked through ester and azomethine with terminal hydroxy group. This upon complexation with copper(II) formed metallomesogenic diol with varying terminal chain length. A series of metallomesogenic polyurethanes were synthesized using these metallomesogenic diols as chain extenders for the prepolymers based on polytetramethylene glycol (PTMG) of varying molecular weight (M_n = 650, 2000) and 2,4-toluene diisocyanate (TDI), or 4,4′-methylene bis(phenyl isocyanate) (MDI). The molar ratio of metallomesogenic diol and PTMG were varied in the polyurethane to find their role in liquid crystalline and mechanical properties. Extensive characterization of all metallomesogenic compounds and intermediates were carried out by FT-IR, ¹H and ¹³C NMR, EPR, VSM, Mass (EI and FAB) and UV–visible spectroscopy. Hot stage polarizing microscope and differential scanning calorimetry were used to ensure the phase characteristics such as nature of phase, melting and clearing temperatures and phase range. The appearance of enantiotropic smectic A phases indicated high molecular polarizability of the core due to the metal ion.     

Lanthanides-clay nanocomposites: Synthesis, characterization and optical properties

Complexes of Europium(III) and Terbium(III) with 2,2-bipyridine and 1,10-phenanthroline were inserted into Na-bentonite by ion exchange reactions at room temperature. The products display interlaminar distances and stoichiometries in agreement with the ion exchange capacity and the interlayer space available in the clay. The optical properties of the intercalates, being qualitatively similar to those of the free complexes, are additionally improved with respect to exchange processes with the medium, especially in a moist environment. The protection again hydrolysis, together with the intensity of the optical transition ⁵D₀-⁵F₂ observed in the nanocomposite, makes these products promising for the development of novel optical materials.     

Synthesis,surface profile,nonlinear reflective index and photophysical properties of curcumin compound

Curcumin and other three curcuminoids (bisdemethoxycurcumin, α-chlorocurcumin and α-methylcurcumin) were synthesized. Fourier transform infrared spectroscopy, Fluorescence quantum yields, AFM analysis and image surface profiles were characterized. All compounds possessed electron donor moieties at both ends of the conjugated π-system and an electron acceptor moiety in the middle of the molecules (D-A-D system) and should exhibit different optical properties depending on substituents on the benzene rings. The third order nonlinear optical properties of the curcuminoids have been investigated by z-scan technique. The optical response was characterized by measuring the refractive index (n₂) of the derivatives of curcumin using the Z-scan technique. The compounds showed negative and large nonlinear refractive index values of the order of 10^?7 cm²/W and reverse saturable absorption with high values of the nonlinear absorption coefficient of the order of 10^?4 cm/W. The nonlinear refractive index was found to vary with the different compound. The optical constants of the different compound films were studied and the dispersion of the refractive index was discussed in terms of the Wemple-DiDomenico single oscillator model. The photo-physical properties of these compounds are compared to those of native curcumin, in order to provide a rationale to the design of samples with molecular structures optimized for a photosensitizer. These types of materials may be considering new photonic applications.     

Synthesis and properties novel polyurethane-hexafluorobutyl methacrylate copolymers

Novel physically crosslinked polyurethane-hexafluorobutyl methacrylate (PU-M) copolymers were prepared by the macroiniferter-controlled radical polymerization method. The chemical structures of the PU-M copolymers were characterized by FT-IR, (1)H-NMR, GPC, DSC, and XPS. The self-assembly and surface properties of the PU-M copolymers have been investigated. The results revealed that PU-M copolymers have good hydrophobility, so the hydrophobility of polyurethane could be easily adjusted by controlling the content of the hydrophobic vinyl monomers. The mechanical evaluation shows that PU-M copolymers exhibit good mechanical properties. The effects of the fluorine content on the surface properties and self-assembly of the PU-M copolymers were investigated. The morphology of the PU-M copolymers' self-assembly was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the mechanism of self-assembly was investigated. Antimicrobial property of the chlorinated PU-M copolymers against both Escherichia coli and Bacillus subtilis bacteria was examined and showed increase compared to that of pure polyurethane.     

Vanadium oxide nanodisks: Synthesis,characterization, and electrochemical properties

Highly crystallined VO_1.6·H₂O nanodisks assembled from nanoparticles have been successfully fabricated under hydrothermal conditions by using bulk V₂O₅ and Na₂S₂O₃ as the starting materials in the presence of surfactant polyethylene glycol 4000 (PEG-4000). The nanodisks have a diameter of 200 nm and thickness of 40 nm. Hollow nanodisks are occasionally observed, which is similar to Chinese ancient copper coins. The formation of nanodisks can be ascribed to a novel solid-solution-solid growth mechanism. Compared with other methods, the solid state transformation method is simple and economic. In addition, the nanodisks exhibit good electrochemical behavior and promising to be used in lithium-ion battery.     

Urchin-like ZnO nanostructures: Synthesis, characterization and optical properties

Urchin-like ZnO nanostructures have been synthesized by a two-step thermal evaporation method. The product was characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and spectrofluorometry. The results of characterization revealed that the urchin-like ZnO nanostructure consists of a spherical metallic Zn core and wurtzite ZnO nanowires growing on the surface of the ZnO buffer which covers the Zn core and the growth directions of wurtzite ZnO nanowires are along <10-10>. According to the analysis on these results, a possible two-step growth mechanism was proposed to explain the formation of the urchin-like ZnO nanostructures. The fluorescence-emission mechanisms were also discussed.     

一种新型红色磷光材料的合成及光物理性能研究

以2-甲基苯并噻唑、苯甲醛为原料,通过与三氯化铱配合,得到一种新型红色金属铱(Ⅲ) E-2-苯乙烯基苯并噻唑(SBT)乙酰丙酮(acac)配合物(SBT)2Ir(acac).通过质谱、核磁、红外光谱对其结构进行了表征,并对其光致发光性能进行了研究.研究结果表明:配合物(SBT)2 Ir(acac)在428和471nm处的紫外吸收属于单线态和三线态金属铱到配体的电荷转移吸收(1MLCT和3MLCT);在632nm处有强的金属配合物三线态磷光发射;(SBT)2Ir(acac)金属配合物的EHOMO=-4.8 eV,ELUMO=-2.5eV,磷光量子效率Φ (SBT)2Ir(acac) =0.19.(SBT)2Ir(acac)可能是一种极有潜力的电致磷光材料.     

Phenylenevinylene copolymers of dihexylthienylbenzothiadiazole and triphenylamine or tetraphenylbenzidine: synthesis, characterization and photovoltaic properties

Three novel low-band gap phenylenevinylene copolymers (P1, P2, and P3), containing dihexylthienylbenzothiadiazole (DTBT) and triphenylamine (TPA) or tetraphenylbenzidine (TPD) were synthesized via the Wittig–Horner reaction. The effects of TPA and TPD on the thermal, optical, electrochemical and photovoltaic properties were investigated. The UV–Vis spectrum of P3, which contains TPD in the polymer backbone, exhibits a broader and stronger absorption in the film than those of P1 and P2. The bulk heterojunction solar cells were fabricated with the as-synthesized polymers as the donors and [6,6]-phenyl-C₆₁-butyric acid methyl ester as the acceptor in a 1:4 weight ratio. The device based on P3 exhibits the maximum power conversion efficiency of 1.11?% under simulated AM 1.5?G solar irradiation (100?mW/cm²).     

羟乙基壳聚糖接枝聚乳酸的合成与表征

首先采用壳聚糖(CS)与2-氯乙醇反应制备了羟乙基壳聚糖(HECS),然后通过本体开环聚合法,以辛酸亚锡为催化剂,CS和HECS为大分子引发剂引发消旋-丙交酯开环聚合制备了一系列CS-g-PDL-LA和HECS-g-PDLLA共聚物,用FTIR、1HNMR、XRD、TG和溶解实验对产物的结构与性能进行了分析表征。结果表明,与CS相比,HECS明显具有较高的反应活性,当n(D,L-LA):n(aminoglucoside)投料比从10:1增大到40:1,对应CS-g-PDLLA和HECS-g-PDLLA共聚物的接枝率分别从24.01%和77.42%上升到114.85%和380.51%,而两者中的聚乳酸侧链上的平均乳酰单元数也相应从0.61和2.51分别上升到2.48和12.31。另外,原料投料比对共聚物的组成与性能有显著影响,随n(D,L-LA):n(ami-noglucoside)值增大,共聚物的接枝率和聚乳酸侧链上的平均乳酰单元数也逐渐增大,共聚物的结晶性能下降,起始热分解温度有所降低。与CS-g-PDLLA相比,HECS-g-PDLLA在常用有机溶剂中的溶解性能有所改善。     

Synthesis and material and electronic properties of conjugated polymers

Conjugated polymers such as polyacetylene are semiconductors, and can be chemically doped to give very high values of conductivity (up to 150 000 S cm^–1). The semiconducting properties are due to delocalization of the electron system formed along the polymer chain, and this general class of materials shows many desirable semiconductor properties for electrical and optical applications. There are considerable challenges to find synthetic routes to allow processing of the polymer to the forms required for applications, and many of the recent important advances in the field are due to improvements in this area.     

PMTFPSb-PEO-b-PMTFPS含氟三嵌段共聚物的合成及其溶液性质研究

通过阴离子开环聚合制备了Si-H封端聚[1,3,5-三甲基-1,3,5(3,3,3-三氟丙基)硅氧烷](PMTFPS)大分子单体,进而与双烯丙基聚氧乙烯醚(PEO)进行硅氢加成反应合成了不同亲水/疏水嵌段比例的PMTFPS-b-PEO-b-PMTFPS三嵌段共聚物。分别利用GPC和1H-NMR等手段表征了嵌段共聚物的结构组成,测定了不同结构嵌段共聚物的平衡表面张力及临界胶束浓度(cmc)。研究表明,当疏水嵌段链长一定时,临界胶束浓度(cmc)值随聚醚嵌段的增长而下降;当聚醚嵌段长度一定时,cmc值不随疏水嵌段长度的变化而变化。     

二苄基二硫代氨基甲酸四甲基铵的合成、表征及性能研究

以二苄基胺、NaOH和CS2为原料,四氢呋喃作溶剂合成二苄基二硫代氨基甲酸钠,再与四甲基氯化铵反应,合成了新型的离子盐促进剂——二苄基二硫代氨基甲酸四甲基铵。通过红外(FT-IR)、核磁(1H NMR)、质谱(MS)及元素分析等分析方法确定了产物的结构。为了研究新型促进剂的性能,实验将合成的二苄基二硫代氨基酸四甲基铵、二硫化四甲基秋兰姆(TMTD)分别添加到天然橡胶中制成胶片,对其进行溶胀指数(SI)和力学性能测试,结果表明合成的二苄基二硫代氨基酸四甲基铵具有优异的促进性能,是一种性能优异绿色环保的天然橡胶促进剂。