Photopolymerization of Pyrrole Initiated by the Ferrocene- and Iron-Arene Salts-Chlorinated Solvents Complexes

Abstract

Ferrocene- and iron-arene salts can photoinitiate polymerization of pyrrole in the presence of halogenated solvents, such as CH₂CH₂Cl₂, CHCl₃, and CCl₄, when irradiated with UV light (254 nm). The polypyrroles obtained are black colloidal powders and have low conductivity in the range of 10^?5 S cm^?1 and rather poor electrochemical properties, which can be the result of loss of conjugation by halogenation. Polypyrrole samples contain both covalently bounded CCl₃ groups (from CCl₄) and ionic FeCl^? ₄. A mechanism of photoinitiated polymerization of pyrrole has been proposed.     

Stabilisation of cis-1,4-polybutadiene against photo-oxidation and singlet oxygen oxidation by hindered phenols

The hindered phenols, 1,6-di-methylphenol, 2,4,6-tri-methylphenol, 2,6-di-tert-butylphenol and 2,4,6-tri-tert-butylphenol, were examined for their stabilising effect in free radical photo-oxidative and singlet oxygen oxidative degradation of cis-1,4-polybutadiene in solution. The stabilising activity was found to be a complex function of the ability of the hindered phenols to react with free radicals and singlet oxygen. Steric hindrance has an obvious effect on the stabilising activity of phenols.     

Production of Upsilon(1S) mesons from chi(b) decays in p&pmacr; collisions at sqrt

We have reconstructed the radiative decays chi(b)(1P)-->Upsilon(1S)gamma and chi(b)(2P)-->Upsilon(1S)gamma in p&pmacr; collisions at sqrt[s] = 1.8 TeV, and measured the fraction of Upsilon(1S) mesons that originate from these decays. For Upsilon(1S) mesons with p(Upsilon)(T)>8.0 GeV/c, the fractions that come from chi(b)(1P) and chi(b)(2P) decays are [27.1+/-6.9(stat)+/-4. 4(syst)]% and [10.5+/-4.4(stat)+/-1.4(syst)]%, respectively. We have derived the fraction of directly produced Upsilon(1S) mesons to be [50.9+/-8.2(stat)+/-9.0(syst)]%.     

Experiments with longitudinally polarized electrons in a storage ring using a siberian snake

We report on first measurements with polarized electrons stored in a medium-energy ring and with a polarized internal target. Polarized electrons were injected at 442 MeV (653 MeV), and a partial (full) Siberian snake was employed to preserve the polarization. Longitudinal polarization at the interaction point and polarization lifetime of the stored electrons were determined with laser backscattering. Spin observables were measured for electrodisintegration of polarized 3He, with simultaneous detection of scattered electrons, protons, neutrons, deuterons, and 3He nuclei, over a large phase space.     

Crosslinking photocopolymerization of acrylic acid (and N‐vinylpyrrolidone) with triethyleneglycol dimethacrylate initiated by camphorquinone/ethyl‐4‐dimethylaminobenzoate

In this article, we report the camphorquinone/amine visible‐light‐induced photocopolymerization of monofunctional acrylic acid (AA), N‐vinylpyrrolidone (NVP), or both with difunctional triethyleneglycol dimethacrylate (TEGDMA) monomers followed by the crosslinking of pendant double‐bond groups of the resulting homopolymers and copolymers. Our primary objective was to study the photocopolymerizability of various mixtures of AA, NVP, and TEGDMA compositions at different molar ratios in air. The photocopolymerization of AA with TEGDMA occurred with the formation of two peaks at different rates of polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 876–886, 2000     

Investigation of PVC Degradation Mechanism by ESR

During the γ-irradiation and UV-light photolysis of polyvinyl chloride) (PVC), free radicals are formed which may be detected by electron spin resonance (ESR) spectroscopy. In this paper interpretations of the ESR spectra and decomposition mechanisms of PVC are presented.     

A flash photolysis study of the triplet state quenching of anthracene by oxygen in the presence of polystyrene

The rate constant for the quenching of triplet anthracene by molecular oxygen in the presence or absence of polystyrene was measured. The quenching ability is not affected by the presence of polymer.     

Studies of the photooxidation mechanism of polymers. III. Role of tetrahydrofuran in the photooxidative degradation of poly(vinyl chloride)

The influence of tetrahydrofuran (THF) on photooxidative degradation of poly(vinyl chloride) in films cast from THF solution was studied. THF is partially retained in the polymer matrix in amounts of 6–8% after casting and drying the film. The last 2–3% is very difficult to remove. By use of thermogravimetric analysis, density measurements, and gas permeability measurements, it was shown that THF residues can be removed by preheating the PVC samples to 80°C. THF forms a charge-transfer complex with oxygen which is easily photolyzed. During this reaction hydroperoxide radicals are formed. Molecular weight distribution curves by gel-permeation chromatography (GPC) show that THF in the presence of air promotes the photodegradation of PVC. Attention has been given to the correct interpretation of the infrared absorption spectra of PVC films containing THF residues and ultraviolet-irradiated in air.