Grafting simultaneous method

In the simultaneous method, which is the one most commonly used, the substrate is irradiated while in direct contact with the monomer. The monomer can be present as a vapor, liquid, or solution. This grafting process can occur via free radial or ionic mechanism. With the simultaneous method, the formation of homopol5mier is unavoidable, but there are several systems to minimize it. The advantage of this method is that both monomer and substrate are exposed to the radiation source and both form reactive sites. The other two techniques rely upon rupture of the bond to form reactive sites, and therefore require higher radiation doses. Thus, the simultaneous method is more suitable for substrates sensitive to radiation. The simultaneous method can utilize UV radiation besides EB source. Logically, the UV irradiation requires a photoinitiator or sensitizer to achieve an acceptable level of grafting. 

Although considerable work has been reported using preirradiation grafting, the present treatment will be confined to the mutual or simultaneous procedure since by this latter technique, much lower doses are needed to accomplish a particular percentage graft The simultaneous method is also amenable to the use of additives to accelerate copolymerization. The additives to be discussed in this paper include solvent, mineral acid and polyfunctional monomers for the grafting of styrene monomer to polyethylene and polypropylene films in the presence of gamma radiation ... 

In the direct or simultaneous method, polymer A j is irradiated in the presence of monomer B (Scheme 5.9) free macroradicals generated by the radiolysis of A j then initiate the polymerization of B, thus forming grafts. Simultaneously, monomer B is homopolymerized because, apart from polymer A j, also monomer B is radiolyzed (though this might be an unwanted effect). Notably, this scheme operates in the absence of oxygen. 

The investigations have shown, however, that graft copolymerization carried out according to this method is accompanied with a simultaneous reaction of monomer homopolymerization which, naturally, reduces the effectiveness of the method. This is explained by the presence of hydroxyl radicals in the reaction medium, which are formed as formulated in the above scheme. 

Simultaneously Schwab, Stannett, Rakowitz, and Magrane (51) applied the ceric ion method to the grafting of vinyl monomers to paper. They studied the influence of a number of variables, such as the soaking of the paper with the monomer emulsion, the oxygen occlusion, the temperature during grafting, the monomer concentration, the time, and... 

In all these reactions homopolymerization occurs simultaneously indeed the released bromine atoms induce polymerization of the added monomer, so that the final graft or block copolymer always contains homopolymer. Therefore the method based on the reaction of ceric ions (Ce-IV) with polyvinyl alcohol seems especially attractive ... 

The simultaneous hydrosilylation and ring-opening polymerization process provides a powerful method for the construction of a variety of novel polymer networks including comb, block and graft polymers, e.g. 272 (equation 102)271. 

Radiation grafting [83, 84, 85, 86, 87, 88, 89] is a very versatile and widely used technique by which surface properties of almost all polymers can be tailored through the choice of different functional monomers. It covers potential applications of industrial interest and particularly for achieving desired chemical and physical properties of polymeric materials. In this method, the most commonly used radiation sources are high-energy electrons, y-radiation, X-rays, U.V.-Vis radiation and, more recently, pulsed laser [90], infrared [91], microwave [92] and ultrasonic radiation [93]. Grafting is performed either by pre-irradiation or simultaneous irradiation techniques [94, 95]. In the former technique, free radicals are trapped in the inert atmosphere in the polymer matrix and later on the monomer is introduced into... 

IPNs are fabricated along several general pathways. In one, a linear or slightly crosslinked polymer is swollen by a monomer, followed by polymerization of the monomer. Another method is the utilization of simultaneous graft polymer-... 

A desire to design high capacity adsorbents resulted in the synthesis of hybrid materials with multifunctional groups introduced via direct co-condensation of proper organosilanes instead of less effective post-synthesis si lanization.19,20 One-pot synthesis through self-assembly mechanism allows the creation of active sites inside mesopores, that after template removal become accessible for adsorption.21 An alternative method for chemical grafting of OMSs, known as template displacement synthesis, permits a simultaneous template removal and attachment of functional groups.22... 

Some of the areas where interfacial protein layers dominate the boundary chemistry are reviewed, and we introduce some nondestructive armlytical methods which can be used simultaneously and/or sequentially to detect and characterize the microscopic amounts of matter at protein or other substrates which spontaneously acquire protein conditioning films. Examples include collagen and gelatin, synthetic polypeptides, nylons, and the biomedically important surfaces of vessel grafts, skin, tissue, and blood. The importance of prerequisite adsorbed films of proteins during thrombus formation, cell adhesion, use of intrauterine contraceptives, development of dental adhesives, and prevention of maritime fouling is discussed. Specifics of protein adsorption at solid/liquid and gas/liquid interfaces are compared. 

Several laboratories have developed the methods of mesoporous silica surface functionalization with simultaneous removal of the surfactant and grafting of organic functionalities without prior calcination. A convenient and highly controllable approach to the surface functionalization of mesoporous silica[221] employs an alcoholic solution of... 

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