Radiation, conducting polymer-based

Electroluminescence. In Section 6.3.2.5, we saw that some materials—in particular, semiconductors—can reemit radiation after the absorption of light in a process called photoluminescence. A related type of emission process, which is common in polymer-based semiconductors, called electroluminescence, results when the electronic excitation necessary for emission is brought about by the application of an electric field rather than by incident photons. The electric field injects electrons into the conduction band, and holes into the valence band, which upon recombination emit light. 

In this chapter, monitoring of radiation-induced reactions will be discussed using examples of organic and polymer based nanomaterials. Those materials mostly display low to medium conductivity. The approach described might be used in other types of systems of similar conductivity, but it is not suitable for reactions in aqueous or similar solutions. The latter are better studied using conductometry, which is beyond the scope of this chapter. 

P. Saini, V. Choudhary, Conducting Polymer Coated Textile Based Multilayered Shields for Suppression of Microwave Radiations in 8.2-12.4 GHz Range. /App/ Polym Sci 2013,129, 2832-2839. 

A resist composition containing a soluble electrically conductive polymer like 3-dodecylPT together with a radiation sensitive (UV, deep UV, electron beam) acid-or base-generating agent is described to be of high sensitivity and resolution [147]. 

Considerable disagreement still prevails as to the mechanism of crosslinking in polymers. Is it an ionic or a radical process While the author admits the existence of some ionic species (as revealed by ESR at low temperature and by radiation-induced conductivity), his present view is that the ionic contribution to crosslinking in solids and liquids is only minor. This attitude is based inter alia on the following evidence. 

Irradiation techniques are more and more widely utilized for industrial applications for instance, for food preservation, medical sterilization, and polymer processing. Such techniques require specific rules of control by means of accurate dosimetry [89]. In this context, new promising dosimeters based on resistance measurements of organic conducting crystals have been reviewed by Zuppiroli et al. [89]. The crystals utilized as dosimeters are either small needles (0.01 x 0.01 x 3 mm3) or larger plates (0.1 x 0.5 x 3 mm3), and their electrical resistances ( 1 kfl in the first case, 1 H in the second) increase exponentially with the adsorbed radiation dose, up to quite high doses. 

A modern series of new plastics are based on transition metals (e.g. Fe, Ti, Cr, Zn, V) to form polymers and possess unusual properties such as variable oxidation states, and ligand exchange on the metal atom. They have reduced UV absorption and visible radiation and exhibit electrical conductivity. Examples include cyclopentadienyl and arene metal n polymeric complexes that act as electron rich aromatic system and are very reactive to a range of monomers to form polymers. 

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