Ionizing radiation, initiator, grafting

The growth in popularity of radiation as the initiating system for grafting arises from the improvement in availability and cost of ionizing radiation. This is due to the introduction of more powerful nuclear reactors. Apart from its inexpensiveness, radiation is a very convenient method for graft initiation because it allows a considerable degree of control to be exercised over such structural... 

Effects of Various Additives on Accelerated Grafting and Curing Reactions Initiated by UV and Ionizing Radiation... 

Polymer radicals can also be produced by the irradiation of a polymer-monomer mixture with ionizing radiation. Thus, the interaction of ionizing radiation with polyethylene-styrene produces radical centers on polyethylene, and these initiate graft polymerization of styrene to produce poly(ethylene-gra/i-styrene) [Rabie and Odian, 1977]. 

In materials such as catalysts where surface properties are of importance it should be possible to alter or enhance activity by use of ionizing radiation. Investigations of the possibility of using radiation to achieve graft polymerizations have recently been initiated. For this application ionizing radiation enjoys some very special advantages. 

Two important factors in initiating graft copolymerization reactions of vinyl monomers with activated cellulose are (1) the lifetime of the free radical sites and (2) the accessibility of the free radical sites to the monomers. For ceric ion initiation or hydroxyl radical initiation the lifetimes of the free radicals on the cellulose molecule were short (5, 19) therefore, the monomer should be present when the free radicals were formed. For ionizing radiation both short lived and long lived (trapped) free radicals were formed (22, 26, 44). Consequently, the activation reaction and the copolymerization reaction could either be conducted... 

It is important to pay attention to the potential role of peroxides created on the surface of plasma-treated, including plasma polymer-coated, TPOs in the formation of durable bonds between the substrate and primer. It has been known for decades that the peroxides formed on the irradiated polymers (by y-ray. X-ray, electron beams, etc.) can be utilized in graft copolymerization of various monomers. This method is known as the peroxide method of radiation copolymerization [27]. The trunk polymer is first irradiated by ionizing radiation in a vacuum or in an inert gas environment. The irradiated polymer is exposed to air or oxygen to convert free radicals to peroxides. Thus created peroxides-containing polymers were used as the initiator of the free radical polymerization of the second monomer. The polymer peroxides are decomposed by heat or by the use of reduction/oxidation accelerator, i.e., peroxides are converted to free radicals. 

This paper summarizes chemical grafting techniques explored in this laboratory that have potential biomedical application. These reactions, initiated by ceric ions, persulfate-bisulfite redox systems, or the presence of comonomers forming donor-acceptor complexes, were carried out in an aqueous environment under conditions which, with suitable modifications, might be tolerated in vivo. Grafting onto tissue surfaces by means of ionizing radiation will not be discussed since techniques for avoiding undesirable side reactions have not yet been developed. 

This involves the formation of graft copolymers from a reaction between polymers and monomers. " Monomer units can be propagated onto the polymer backbone to form a graft structure. Free radicals, air, or ionizing radiations are used to initiate the reaction. A... 

Graft copol3rmers can be synthesized by various initiation methods such as using ultraviolet and ionizing radiations, and thermal and chemical reactions (, . Despite considerable re-... 

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