An IR study of poly-1,4-phenylenevinylene (PPV), the 2,5-dimethoxy derivative [(MeO)2-PPV], and their corresponding xanthate precursor polymers and monomers

A detailed comparison of the infrared (IR) spectra of poly-1,4-phenylenevinylene (PPV), its xanthate precursor polymer, and its bis-xanthate precursor monomer along with the corresponding 2,5-dimethoxy derivatives has provided a clearer basis for characterizing these species with regard to both structure and purity. All the xanthate precursor monomers and polymers exhibit characteristic intense absorptions typical of the xanthate group near 1220, 1110, and 1050 cm(-1). Upon complete conversion of the precursor polymer to the vinylene linked final product, the intense IR peaks of the xanthate group have disappeared and new bands resulting from the vinylene linkages are found. The latter include a moderately strong band near 965 cm(-1) due to the out-of-plane -CHCH- deformation of the trans-vinylene conjugated with and linking the phenyl rings into an optoelectronic polymer. Unfortunately, the corresponding C-H stretching vibration of this same group of atoms expected to appear near 3020 cm(-1) falls in the same region of the spectrum as the aromatic C-H stretches of the phenyl rings. Similarly, for the 2,5-dimethoxy polymer derivative, [(MeO)(2)-PPV], the C-H stretching vibration near 3055 cm(-1) contains contributions from both aromatic and vinylene C-H. Density functional theory (DFT) calculations on the monomers were instrumental in assigning the infrared spectra of these materials. This study provides a systemic means for verifying that the precursor monomer has been polymerized into the precursor polymer and that thermal conversion to the conjugated polymer is complete.     

聚(茚并芴-三苯胺)的合成及性能

设计并合成了一类新的可用于有机场效应晶体管(OFET)的聚合物半导体材料聚(茚并芴-三苯胺)(pIFTPA1~4), 通过核磁共振谱和凝胶渗透色谱等对聚合物进行了表征, 同时对其场效应薄膜晶体管性能进行了测试. 结果表明, 这些聚合物形成了无定形半导体膜, 在空气中稳定, 其载流子迁移率远高于聚三苯胺(pTPA)类材料, 其中pIFTPA1载流子迁移率高达4×10^-2 cm²/(V·s), 开关比为10⁶.     

PHOTOELECTRON SPECTROSCOPY STUDY OF AMMONIA-INDUCED CHANGES IN ELECTROSTATICALLY-ASSEMBLED CONJUGATED POLYMER FILMS

ABSTRACT

Exposure of electrostatically assembled polyelectrolyte films comprised of the anionic carboxylic conjugated polymer poly[2-(3-thienyl)-ethanolhydroxycarbonylmethyl-urethane], hereafter referred to as H-PURET, and polycations such as poly(diallyldimethylammonium) chloride, here after referred to as PDADMAC, to aqueous ammonia vapor leads to dra matic changes in the ultraviolet-visible absorption spectrum. In the case of H-PURET/PDADMAC, a shift from 442 to 494 nm is observed upon overnight ammonia exposure. X-ray photoelectron spectroscopy has been used to investigate the mechanism of the changes in optical properties. The C1s, O1s and S2p core levels exhibit negligible ammonia-induced changes. Two N1s peaks are observed in virgin H-PURET/PDADMAC assemblies, and ammonia exposure causes the nitrogen peak corresponding to the H-PURET side chain to become more intense relative to that of the PDADMAC layer. This selective change in the N1s feature suggests that ammonia interacts with the polythiophene side-chain, presumably by deprotonating the fraction of carboxylic acid groups that remain in the H-PURET layer. This deprotonation apparently leads to structural or single chain conformational changes in the conjugated polymer layers that alter the electronic absorption spectrum.     

Molecular Assembly by Sequential Ionic Adsorption of Nanocrystalline TiO2 and a Conjugated Polymer

Abstract

Cationic nanocrystalline TiO₂ particles have been synthesized for which the size and composition of the nanoparticles were analyzed by a transmission emission microscopy and energy dispersive x‐ray spectrometer (EDXS). Multilayered films have been fabricated by sequential adsorption of TiO₂ nanoparticles and poly(3‐thiophene acetic acid) (PTAA). Each layer of the nanoparticles and PTAA in the thin film has also been characterized by x‐ray photoelectron spectroscopy, atomic force microscopy, and UV‐visible spectroscopy. These types of multilayered nanocomposite films may find applications in the fabrication of efficient light harvesting photovoltaic cells.     

Examination of the statistical method in the conjugated circuit theory

Summary The recently proposed statistical method for the calculation of resonance energies in the conjugated circuit theory is tested on the example of polyacenes. It is found that for the estimation of the resonance energy with a 10% average error, the method requires a sample consisting of about 20 (randomly chosen) Kekulé structures. Further increase of the sample size gives no significant gain in the accuracy of the method.

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Überprüfung der statistischen Methode in der Konjugierten-Ring-Theorie

Zusammenfassung Die unlängst vorgeschlagene statistische Methode in der Konjugierten-Ring-Theorie (conjugated circuit theory) wird am Beispiel der Polyacene getestet. Es wurde festgestellt, daß für die Abschätzung der Resonanzenergien bei einem mittleren Fehler von 10% für diese Methode ungefähr 20 (willkürlich gewählte) Kekulé-Strukturen nötig sind. Weitere Erhöhung dieser Anzahl bringt keine signifikante Verbesserung der Genauigkeit der Methode.

     

含液晶基团的聚对亚苯基亚乙炔基类交替共聚物的合成、表征及性能研究

合成了两种含氰基联苯液晶基团的新型聚对亚苯基亚乙炔基(PPE)类交替共聚物,并对其进行了结构表征和性能研究.示差扫描量热仪(DSC)和偏光显微镜(POM)的结果证明了在液晶单元含量较大时聚合物才会出现明显的液晶形态.荧光光谱表明,在降温前后液晶聚合物的发光光谱发生了明显的变化.同时,对聚合物进行能量转移研究发现随着溶液浓度的增加,Frster能量转移更加完全;另外,利用原子力显微镜(AFM)对聚合物降温前后的形态变化进行了观察.结果表明,液晶性质可以导致聚合物形态的变化进而带来发光光谱的改变,为今后制备液晶可控型发光聚合物提供了理论依据.     

Polymer dispersions from catalytic polymerization in aqueous systems

By contrast to traditional free radical emulsion polymerization, catalytic polymerization allows for polymer microstructure control. In terms of polymerizable monomers, both techniques are largely complementary. Since the beginning of this decade, an increasing number of reports on polyolefin, polybutadiene, polyalkenamer, polynorbornene, polyketone, and polyacetylene dispersions prepared by catalytic polymerization in disperse aqueous systems has appeared. This contribution reviews the preparation of these dispersions, their colloidal properties, particle formation mechanisms, particle morphologies, and polymer microstructures.     

Optical behaviors of conjugated-chain compounds containing benzene and furan units

Thirteen conjugated-chain compounds which contain benzene and furan units were prepared, their optical behaviors, including UV-vis absorption coefficient (varepsilon), absorption wavelengths (lambdaa), fluorescence emission wavelengths (lambdae), and quantum yields (Phi) were measured. Meanwhile, their LUMO and HOMO energy were determined by cyclic voltammetry and their second-order polarizations (betaxxx) values were determined by solvatochromic method, respectively. The results showed that this kind of compounds possess a shorter lambdaa (320-365 nm) and performance a higher Phi values, especially for 2aa, 2ab, 2ac and 2bb, their Phi values are all more than 90%. These compounds, except 2db, showed a higher betaxxx values in DMSO, especially for 2dc (75.77x10(-30) m5 C-1) and 2dd (83.32x10(-30) m5 C-1), than that 10-methyl-acridone (6.578x10(-30) m5 C-1) or 10-benzylacridone (6.845x10(-30) m5 C-1) in DMSO did, and second harmonic generation value of 10-methylacridone and 10-benzylacridone in powder are, respectively, 1.381 and 1.861 times of that value of urea. The betaxxx values and Phi values determined for these compounds in this work were lower than these values which were desired in the original work, this phenomena was explained from their molecular structures. This work confirmed that as these compounds performance shorter lambdaa and higher Phi values, they could be good blue-color optical materials for some fields, such as OLED materials, two-photo absorption materials, fluorescent dyes.     

The reaction of fluorine-containing compounds with conjugated dienoic acids initiated by sodium dithionite

The reaction of fluorine-containing halides and acetamides with conjugated dienoic acids initiated by sodium dithionite gave halide-free 1,4-adducts in 40-80% yields, with the E configuration as the major products.     

Visual detection of Al ions using conjugated copolymer-ATP supramolecular complex

A colorimetric Al³⁺ sensor based on fluorescence recovery of a conjugated copolymer-ATP complex is proposed. An optimized ratio of two polythiophene (PT) monomers is utilized to synthesize copolymer (CP) that yielded maximized colorimetric response for Al³⁺ in deionized (DI) and tap water. The electrostatic disassembly of CP-ATP upon addition of Al³⁺ led to an evident visual color change. The lowest concentration of Al³⁺ for naked eye observation is around 4 μM, which is below the threshold levels in drinking water according to European Economic Community (EEC) standard. Besides, the proposed assay showed a similar response to Al³⁺ in tap water. The proposed methodology showed selective and sensitive detection for Al³⁺ in analytically relevant concentration ranges without involving sophisticated instrumentation, illustrating the applicability for on-site drinking water monitoring.