Synthesis and characterization of new polymer systems containing very bulky tris(trimethylsilyl)methyl substituents as side chains

The 4-chloromethyl styrene (CMS) was copolymerized with different styrenic monomers such as methyl styrene, 4-methoxy styrene and α-methyl styrene by free radical polymerization method at 70 ± 1 °C using α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator and the copolymers I, II and III collected respectively. The very bulky tris(trimethylsilyl)methyl {trisyl} substituents were covalently attached to the obtained copolymers with replacement of all the chlorine atoms in CMS units. The polymers, obtained in quantitative yields, were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy; differential scanning calorimetry (DSC) and GPC studies. All the polymers containing trisyl groups showed a high glass transition temperature (in the range 150-190 °C) in comparison with copolymers I-III (in the range 90-95 °C). The increase of the glass transition temperature reflects the substantial increase in rigidity of new polymers bearing very bulky substituents in side chains.     

Electrochemical Biosensing of DNA Immobilized Poly(Vinylferrocenium) Modified Electrode

The polymer, poly(vinylferrocenium) (PVF⁺) modified electrode was developed as the first time herein for the improved electrochemical sensing of DNA based on the oxidation signals of polymer and guanine. The morphologies of polymer film and DNA immobilized polymer film were examined using scanning electron microscope (SEM). The electrochemical behavior of polymer modified electrode was investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in the absence/presence of DNA. Experimental parameters, such as the polymeric film thickness, the DNA immobilization time, the concentration of buffer solution, pH and DNA concentration were examined in order to obtain more sensitive and selective electrochemical signals. After optimization studies, DNA hybridization was also investigated.     

聚中性红膜修饰电极测定痕量NO2^—的研究

研究了聚中性红膜修饰电极对ＮＯ－２的催化氧化性能，建立了测定ＮＯ－２的新方法。ＮＯ－２的浓度在２．０×１０－６～５．０×１０－３ｍｏｌ／Ｌ范围内与催化氧化峰电流呈良好的线性关系，检测限为６．０×１０－７ｍｏｌ／Ｌ。若利用计时电流法分析，检测限可达８．０×１０－８ｍｏｌ／Ｌ。     

Poly(ester sulphonic acid) coated mercury thin film electrodes: characterization and application in batch injection analysis stripping voltammetry of heavy metal ions

Mercury-thin film electrodes coated with a thin film of poly(ester sulphonic acid) (PESA) have been investigated for application in the analysis of trace heavy metals by square wave anodic stripping voltammetry using the batch injection analysis (BIA) technique. Different polymer dispersion concentrations in water/acetone mixed solvent are investigated and are characterised by electrochemical impedance measurements on glassy carbon and on mercury film electrodes. The influence of electrolyte anion, acetate or nitrate, on polymer film properties is demonstrated, acetate buffer being shown to be preferable for stripping voltammetry applications. Although stripping currents are between 30 and 70% less at the coated than at bare mercury thin film electrodes, the influence of model surfactants on stripping response is shown to be very small. The effect of the composition of the modifier film dispersion on calibration plots is shown; however, detection limits of around 5 nM are found for all modified electrodes tested. This coated electrode is an alternative to Nafion-coated mercury thin film electrodes for the analysis of trace metals in complex matrices, particularly useful when there is a high concentration of non-ionic detergents.     

Poly(Organophosphazenes): Use in the Improvement of Standard Materials. Application to the Modification of Surface Properties of Poly(Vinyl Alcohol)

Abstract

Modification of surface properties of poly(vinyl alcohol) by grafting of poly(organophosphazenes).     

聚萘胺膜与金属离子的络合及催化特性的研究

系统研究了聚萘胺膜与Ａｇ、Ｈｇ（２＋）等十余种金属离子的络合特性。以循环伏安法、交流阻抗分析等方法研究了Ａｇ－ＰＮＡ电极对抗坏血酸（Ｈ２Ａ）氧化的催化作用，提出了电极反应的可能机理。Ａｇ－ＰＮＡ电极可用于测定试样中的Ｈ２Ａ含量。     

Poly(arylene ether) ionomers containing sulfofluorenyl groups: Effect of electron-withdrawing groups on the properties

For polymer electrolyte membrane fuel membrane cell (PEMFC) applications, the effect of electron-withdrawing groups on the properties of sulfonated poly(arylene ether) (SPE) ionomer membranes was investigated. A series of poly(arylene ether)s containing fluorenyl groups and electron-withdrawing groups (sulfone, nitrile, or fluorine) was synthesized, which were sulfonated with chlorosulfonic acid using a flow reactor to obtain the title ionomers. The ionomers had high molecular weight (M_n > 77 kDa, M_w > 238 kDa) and gave tough, ductile membranes by solution casting. The ion exchange capacity (IEC) of the membranes ranged from 1.6 to 3.5 mequiv/g as determined by titration. The electron-withdrawing groups did not appear to affect the thermal properties (decomposition temperature higher than 200 °C). The presence of nitrile groups, especially at positions meta to the ether linkages, improved the oxidative stability of the SPE membranes, while it led to a deterioration of the hydrolytic stability. The perfluorinated biphenylene groups were effective in providing high mechanical strength with reasonable dimensional change, probably due to a somewhat decreased water absorbability. The SPE membrane containing sulfone groups showed the highest proton conductivity (10⁻³-10⁻¹ S/cm) at 20-93% RH (relative humidity) and 80 °C. The nitrile-containing SPE membrane showed smaller apparent activation energies for oxygen and hydrogen permeability and is thus considered to be a possible candidate for applications in PEMFCs.     

Evaluation of the chiral recognition properties as well as the column performance of four chiral stationary phases based on cellulose (3,5-dimethylphenylcarbamate) by parallel HPLC and SFC

The performance of four commercially available cellulose tris(3,5-dimethylphenylcarbamate) based chiral stationary phases (CSPs) was evaluated with parallel high performance liquid chromatography (HPLC) and super critical fluid chromatography (SFC). Retention, enantioselectivity, resolution and efficiency were compared for a set of neutral, basic and acidic compounds having different physico-chemical properties by using different mobile phase conditions. Although the chiral selector is the same in all the four CSPs, a large difference in the ability to retain and resolve enantiomers was observed under the same chromatographic conditions. We believe that this is mainly due to differences in the silica matrix and immobilization techniques used by the different vendors. An extended study of metoprolol and structure analogues gave a deeper understanding of the accessibility of the chiral discriminating interactions and its impact on the resolution of the racemic compounds on the four CSPs studied. Also, a clear difference in enantioselectivity is observed between SFC and LC mode, hydrogen bonding was found to play an important role in the differential binding of the enantiomers to the CSPs.     

The role of chiral dopants in organic/inorganic hybrid materials containing chiral Schiff base Ni(II), Cu(II) and Zn(II) complexes

Chiral Schiff base complexes containing azo-groups, bis(N-R-1-cyclohexylethyl-4-phenyldiazenylsalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, and without azo-groups, bis(N-R-1-cyclohexylethyl-3,5-dichlorosalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, affording a distorted square planar trans-[MN₂O₂] coordination geometry were prepared. Organic/inorganic hybrid materials in polymethylmethacrylate (PMMA) spincoat films of the complexes (both the azobenzene (AZ) containing type and the latter complexes of the AZ separated type) were assembled for a comparison of polarized UV light induced molecular arrangement caused by the Weigert effect. Investigation of the parameters for the optical anisotropy of the metal complexes as well as AZ suggested that the degree of increasing optical anisotropy of the containing type was higher than that of the separated type based on π-π^∗ (of which a characteristic band appeared around 380 nm) and n-π^∗ bands of polarized absorption electronic spectra. In the AZ containing type, the rigid nickel(II) or zinc(II) complexes easily increase the optical anisotropy compared to the flexible copper(II) complexes. In the AZ separated type, interestingly, enhancement of some CD bands suggests the role of chiral dopants of some complexes without azo-groups for AZ.     

聚氯乙烯薄膜的压电性研究

系统地研究了极化条件、热历程、增塑作用等与聚氯乙烯薄膜压电性的关系,并且讨论了聚氯乙烯薄膜压电性对时间的稳定性。研究结果表明,极化聚氯乙烯薄膜的压电应变常数d_(33)值为2.1×10~(-12)C/N,压电电压常数g_(33)达到73.9×10~(-3)V·m/N,与经典的压电材料石英晶体的压电性相当。     

Electrochemical Behaviour of Poly(benzopyrene) Films Doped with Eriochrome Black T as a Pb2+‐Sensitive Sensors

Poly(benzopyrene) films were electrosynthesized on glassy carbon disk electrodes from benzo(a)pyrene by cyclic voltammetry in the presence of eriochrome black T, which forms strong complexes with lead ions. In consequence, by conditioning the films in high concentration of lead (0.1 mol dm^?3 Pb(NO₃)₂) potentiometric sensitivity to lead ions down to 10^?5 mol dm^?3 Pb²⁺ was induced, and a novel type of lead‐sensitive electrode was obtained. The electrode is characterized by high stability of the potential readouts, good reproducibility of the calibration curves as well as a minor hysteresis effects. The performance of our lead‐sensitive electrode was favourable compared to PEDOT and PPy‐based electrodes doped with eriochrome black T. We conclude that poly(benzopyrene) doped with eriochrome black T is a new electroactive material that may be applied in sensor technology.     

Use of poly(ester-sulfonic acid) film-coated electrodes as amperometric detectors in flow injection analysis

Within the past several years significant advances have been made towards the development and incorporation of chemically modified electrodes as selective detectors for high performance liquid chromatography and flow injection analysis. In many cases the chemically modified electrode systems closely approach the “ideal” detector specifications of chemical and mechanical stability along with a significant linear response region. This paper will discuss the characterization and incorporation of ionomeric poly(ester-sulfonic acid) coated electrodes as nonaqueous electrochemical detectors. The orientation of the electrodes in the detector system as well as the increased sensitivity levels to 10⁻¹⁰ g ml⁻¹ for cationic species and 10⁻⁹ g ml⁻¹ for neutral species will be presented. Also the applicability of the ionomer coated electrodes as nonelectrolyte detectors achieved a reproducible response with detection limits to 10⁻⁶ g ml⁻¹. Overall this system performed as well as, or better than, more specialized and expensive thin layer electrochemical detectors.     

Synthesis and characterization of polymethacrylates containing conjugated oligo(phenylene ethynylene)s as side chains

In order to form suitable systems designed for resonance energy transfer, a series of monodisperse methacrylate‐based monomers containing rigid π‐conjugated oligo(phenylene ethynylenes) with different sizes of the conjugated systems ( M1 – M3 ), and therefore different optoelectronic properties, were synthesized and subsequently polymerized using the reversible addition–fragmentation chain transfer polymerization technique ( P1 – P3 ). In addition, these oligomers were also copolymerized with methyl methacrylate. The obtained polymers were characterized by ¹H NMR spectroscopy, size exclusion chromatography, and analytical ultracentrifugation. The photophysical properties of the polymers were studied by UV–vis absorption and emission spectroscopy in diluted solutions as well as in thin films and compared to the photophysics of the corresponding monomers. Thereby, changes going from monomeric to polymeric systems could be detected in fluorescence quantum yields and lifetimes pointing to energy trapping, e.g., energy transfer. Donor–acceptor copolymers containing different numbers of monomeric units within the side chain exhibit differences in the emission spectra, indicating that energy trapping in polymers is very sensitive to structural properties such as the chain length. UV–vis absorption spectroscopy as well as time‐resolved lifetime studies indicate intrapolymer and interpolymer energy transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Poly(ethylene-oxide)-para-disubstituted benzene intercalates. Molecular conformation of the polymer molecule from far infrared spectra

The far infrared spectra of various poly(ethylene oxide)-para-disubstituted benzene intercalates are reported. From a detailed discussion, it is strongly suggested that the formula of these intercalates is either [(p-C₆H₄XY)₃(CH₂CH₂O–)₁₀] _n (for XY=ClCl, BrBr, BrCl, ICl, ClF and CH₃Br) or [(p-C₆H₄XY)₂(CH₂CH₂O)₇] _n (for XY=BrF and IF). In both cases the conformation of the polymer molecule is nearly TTG. In addition the previously described relative disposition of the host and guest molecules is confirmed.     

Poly(4-vinylpyridinium tribromide) as metal-free, green and recoverable oxidizing polymer for the chemoselective oxidation of sulfides into sulfoxides

Poly(4-vinylpyridinium tribromide) was prepared from poly(4-vinylpyridin) and used for the selective oxidation of a variety of sulfides to the corresponding sulfoxides.The oxidation reaction was carried out heterogeneously in acetone/water,as green solvent, at room temperature.     

Asymmetric catalysis,part 91: Enantioselective monophenylation ofcis-1,2-cyclopentanediol with triphenylbismuth diacetate and chiral copper(II) complexes as catalysts

Summary The monophenylation ofcis-1,2-cyclopentanediol with triphenylbismuth diacetate in the presence of chiral Cu(II) complexes as catalysts gavecis-2-hydroxy-1-phenoxy-cyclopentane with enantiomeric excesses up to 38%. The optically active ligands used were triamine derivatives of 2,6-bis(aminomethyl)pyridine and diamine derivatives of 2-(aminomethyl)pyridine. Selectivity in the monophenylation occurred only in the presence of the latter as auxiliary ligands.

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Asymmetrische Katalysen, 91. Mitt.: Enantioselektive Monophenylierung voncis-1,2-Cyclopentandiol mit Triphenylwismutdiacetat und chiralen Kupfer(II)-Komplexen als Katalysatoren

Zusammenfassung Die Monophenylierung voncis-1,2-Cyclopentandiol mit Triphenylwismutdiacetat in Gegenwart chiraler Cu(II)-Komplexe als Katalysatoren ergabcis-2-Hydroxy-1-phenoxy-cyclopentan mit Enantiomerenüberschüssen von bis zu 38%. Die eingesetzten optisch aktiven Liganden waren Triamin-Derivate von 2,6-bis(Aminomethyl)pyridin und Diamin-Derivate von 2-(Aminomethyl)pyridin. Selektivität bei der Monophenylierung war nur in Gegenwart letzterer als Auxiliar-Liganden zu beobachten.

     

Exploiting π shielding interactions of η arene chromium (0) complexes: New auxiliaries derived from the biogenic chiral pool

A family of highly selective chiral auxiliaries containing arene chromium (0) complexes has been prepared using biogenic precursors from the chiral pool. The systems, derived from isomannide, prolinol, and xylofuranose were applied to the asymmetric Diels-Alder reaction of derived acrylate esters. Factors influencing stereoselectivity with the auxiliaries have been investigated and delineated including the impact of mixed ligands on the chromium (0) complex. Under optimal conditions, the auxiliaries give >95% e.e. and 98:2 exo:endo ratio in cycloaddition with cyclopentadiene.     

Revealing the effect of oligo(ethylene glycol) side chains on n-doping process in FBDPPV-based polymers

The low doping efficiency of n-doped systems limits the development of n-type organic conducting materials. Oligo(ethylene glycol) (OEG) as the flexible chain in conjugated small molecules and polymers may improve doping efficiency. However, OEG side chains also bring unexpected low mobility and poor film morphology. Herein, we propose the stronger solution-state aggregation plays a dominated role in charge transport and morphology of OEG-substituted polymer. The solution-state aggregation also affects doping process. Therefore, we develop a series of polymers based on 3,7-bis((E)-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione (FBDPPV) with different ratios of OEG side chain to investigate the effect of side chain on solution-state aggregation and n-doping process. After n-doped by hexahydro-1H,3a1H,4H,7H-3a,6a,9a-triazaphenalene (TAM), FBDPPV with 50% OEG affords the highest doping efficiency and conductivity, while FBDPPV with 100% OEG shows lower conductivity. Combination of ultraviolet–visible–near infrared absorption spectra, grazing-incidence wide-angle X-ray scattering and atomic force microscopy, we reveal that serious aggregated extent in solution of OEG-substituted polymer result in phase separation and rough morphology, which are the origins of poor conductivity. Our work provides a new perspective on the effect of the OEG side chain on the doped polymer systems, suggesting suitable solution-state aggregation is crucial to high doping efficiency and high conductivity.     

AC Impedance Studies on the Relationship between the Fractal Characteristics and Electrochemical Properties of Poly(Para‐Phenylene) Film

The effects of experimental conditions on the fractal structure of electrosynthetic polyparaphenylene films were studied by electrochemical impedance spectroscopy. The results indicate that, at the potential range (0‐0.6 V), the film surface fractal dimension rises while the corresponding charge transfer resistances R_ct decrease as charge increases. This is consistent with the oxidized behavior of the conducting polymer. As for the degradation of electrolytes, scanning electron microscopy observations of poly(para‐pheneylene) (PPP) film provide evidence of the close relationship between the degradation of electrolytes and the film morphology, also in good agreement with the electrochemical impedance results interpretation. The X‐ray photoelectron spectroscopic analysis results present that the relative oxygen content ratio (O/C) of the films increases with the times the electrolyte is used, which reveals that the degradation of the electrolyte may result in a compact and passivation PPP film.