Chain initiation ionizing radiation

Ionizing radiation. Further studies on the effects of ionizing radiation such as 60Co y-ray radiation and ion beams on polysilanes have been reported.295 304-306 Both positive and negative resist properties can be shown, depending on the side-chain type, branch density, and the presence or absence of radical initiators. 

Using ionizing radiation for intramolecular cross-linking of individual polymers, the synthesis can be performed in the absence of additional initiators, cross-linkers, or additives. For this approach, a pure aqueous solution of the polymer is exposed to a short intense pulse of ionizing electron beam radiation (typically a few microseconds, see Sect. 2.3, Fig. 1). During the exposure many radicals are generated simultaneously along each polymer chain. The intramolecular recombination of these... 

Polymerization initiated by ionizing radiation such as y rays or high-energy electron beams is somewhat similar to plasma polymerization. Understanding of radiation polymerization is very helpful in elucidating mechanisms of plasma polymerization. In radiation polymerization, no initiator is employed, and the chain-carrying species are created by the ionization of monomer. In this respect, radiation polymerization... 

In case the anion is the polymeric species (anionic polymerization) a carbanion or an alkoxide anion forms the active chain end. Initiation is achieved by direct attack of organometaUic compounds, or by electron transfer from alkali metals, alkali metal complexes, or ionizing radiation. In case the cation is the polymeric species (cationic polymerization) a... 

Effects of ionizing radiation on lipid molecules have been understood by studying model systems which are simpler than the real biological membranes, such as PUFA micelles and liposomes. The formation of lipid oxidative modifications of PUFAs appears as a dynamic process initiated by hydroxyl free radicals generated by water radiolysis, amplified by a propagating-chain mechanism involving alkyl and peroxyl free radicals, and leading not only to hydroperoxides but also to a lot of other lipidic oxidized end-products. Kinetic data, such... 

Polymer radicals, that have radical centers on the backbone chain to initiate grafting, can also be produced by irradiation of a polymer-monomer mixture with ionizing radiation. Most radiation graft polymerizations are carried out as heterogeneous reactions. The typical reaction system involves equilibration (swelling) of polymer with monomer followed by irradiation of the monomer-swollen polymer while immersed in excess monomer. For example, to produce poly(ethylene-gra/t-styrene),... 

Polymerization initiated by ionizing radiation can be carried out by both a free-radical and an ionic (cationic or anionic) mechanism. The determining factor is the nature of the end of the growing chain. 

Considerable work has been done on the initiation of the vinyl fluoride by ionizing radiation much as y-radiation from a °Co source. A selection of references on this research includes Usmanov and other authors [4,48-62], Of these, Usmanov et al. [4] deal with the graft copolymerization of vinyl fluoride to some natural and synthetic polymers. Usmanov et al. [53] discuss the formation of branched polymers during radiation-induced polymerization. Gubareva et al. [54] deal with solution polymerizations. Nakamura et al. [58, 59, 61] deal with emulsion polymerizations of vinyl fluoride by radiation initiations. Usmanov et al. [60,61] discuss the effects of chain-transfer agents during radiation-initiated polymerization. Some copolymerization studies are described in Usmanov et al. [55]. 

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