Polyethylene, diffusion electrons

Johnson and Willson interpreted the main feature of the observations on solid polyethylene doped with aromatic solutes in terms of an ionic mechanism it was analogous to that proposed for irradiated frozen glassy-alkane-systems in which ionization occurred with G = 3 — 4 [96], The produced charged species, electron and positive hole, were both mobile as indicated by the radiation-induced conductivity. The production of excited states of aromatic solutes was caused mainly by ion-electron neutralization. The ion-ion recombination was relatively slow but it might contribute to the delayed fluorescence observed. On the basis of Debye-Simoluchovski equation, they evaluated the diffusion coefficients of the radical anion of naphthalene and pyrene as approximately 4 x 10 12 and 1 x 10 12 m2 s 1 respectively the values were about three orders of magnitude less than those found in typical liquid systems. 

When biphenyl was added to polyethylene [174], the biphenyl anion and cation absorption spectra were obtained after irradiation, together with an apparently unchanged trapped-electron absorption. QJ and Qj were both removed by photobleaching. On warming, Qj starts to decay at —120°C, the temperature which corresponds to the first transition in polyethylene. This suggests that the decay is due to diffusion and reaction of the Q2 ion rather than to thermal ejection of the attached electron. 

The two electrons transferred from TDAE to PEDOT-PSS are expected to undope the conjugated polymer chains. Since TDAE diffuses into PEDOT-PSS, long exposures to the electron donor induce changes in the optical properties of the polymer film. Optical absorption experiments on 200 nm thick PEDOT-PSS films coated onto a transparent polyethylene terephthalate (PET) substrate. The pol5mier film was exposed to the TDAE vapor in an inert nitrogen atmosphere and shows the difference in absorption spectrum between a film exposed to TDAE and the pristine PEDOT-PSS layer (Figs. 3.10 and 3.11). The modification of the optical properties and the sheet resistance of the pol5mier layer were recorded versus exposure time. The two absorption features at 550 nm and... 

Most polymers are partially crystalline. The degree of crystallinity of polymers may, however, range very widely from 0 percent for noncrystalhzable polymers, through intermediate crystallinities, up to nearly 100 percent for polytetra uoroethylene and linear polyethylene. A direct evidence of the crystallinity in polymers is obtained from x-ray dilfraction studies. The x-ray patterns of many crystalline polymers show both sharp features characteristic of ordered regions (called crystallites) and diffuse features characteristic of a molecularly disordered phase like liquids. X-ray scattering and electron microscopy have shown that the crystallites are made up of lamellae which, in turn, are built-up of folded polymer chains as explained below. 

An important staining technique was developed by Kanig [246] for the enhanced contrast of PE, a material that has been a model compound for fundamental polymer studies. Polyethylene crystals cannot be sectioned, nor are they stable in the electron beam, due to radiation damage. The chlorosulfonation procedure cross links, stabilizes, and stains the amorphous material in crystalline polyolefins, permitting ultrathin sectioning and stable EM observation. Chlorosulfonic acid diffuses selectively into the amorphous material in the semicrystalline polymer, increasing the density of the amorphous zone compared with the crystalline material. The treatment stains the surfaces of the... 

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