Graft polymerization step reaction

The theory of radiation-induced grafting has received extensive treatment [21,131,132]. The typical steps involved in free-radical polymerization are also applicable to graft polymerization including initiation, propagation, and chain transfer [133]. However, the complicating role of diffusion prevents any simple correlation of individual rate constants to the overall reaction rates. Changes in temperamre, for example, increase the rate of monomer diffusion and monomer... 

The introduction of the functional group, being capable to initiate the radical graft-polymerization, has been sometimes carried out by two- or three-step reactions using reactive reagents, such as butyllithium or thionylchloride. Therefore, some... 

Following the corona-discharge treatment of a silicone surface and the subsequent graft polymerization of AAc, type I atelocollagen was immobilized onto the grafted surface with the use of water-soluble carbodiimide [176, 177]. As depicted in Fig. 17, the immobilization reaction involves two steps, i.e., activation of carboxylic acids and the following nucleophilic substitution with prima-... 

Recently, Hirao et and Paraskeva and Hadjichristidis succeeded in the synthesis of exact graft copolymer with two, three, four, and five branches via a new iterative methodology based on living anionic polymerization. The reaction involves three steps site transformation, linking, and addition (Figure 19). 

For surface modification with an added photoinitiator, the initiating radical sites should be generated on the membrane surface by the reaction of the photoinitiator with the base membrane polymer under UV irradiation. Benzophenon (BP) or its derivatives are most often used for the initiation of the UV-assisted graft polymerization of vinyl monomers on the surface of the polymer membranes. In this case, the key step in the initiation of generating radicals is hydrogen abstraction from the polymer backbone (Kato et al. 2003). 

This method of surface graft polymerization usually includes two steps surface activation and graft polymerization. Sites on the nanoparticle surface are first activated by high-energy electrons, plasma treatment, chemical reactions, etc. and, subsequently, the graft polymerization process is generated. 

Karesoja and coworkers reported grafting of clay with butyl acrylate and MMA by ATRP [60]. An ATRP initiator with trichlorosilane functionality was synthesized reacted with the hydroxyl groups on clay surfaces and initiated the copolymerization of BA and MMA. The three-step reaction was schemed in Figure 10.12. The ll-(2-bromo-2-methyl)propionyl-oxy-undecyl trichlorosilane ATRP initiator was covalently attached to clay platelets via silylation reactions. The initiator clay was used to polymerize BuA and MMA in the bulk monomer solution or dimethyl sulfoxide (DMSO). They found in the nanocomposites prepared from DMSO clay was well dispersed as individual platelets however, in the nanocomposites prepared from bulk solution big aggregates of clay platelets were observed. This indicates that DMSO is able to expand the distance between the clay layers and make the clay gallery more accessible to chemicals. 

This novel sequential photoinduced graft polymerization was tested by Bowman et al. [MA 99] on hydrophobic porous polypropylene (PP) membrane in the presence of acrylic acid. Experimental results showed that the grafting density and the graft polymer chain length could be controlled by choosing the suitable reaction conditions in both steps. In addition, the method substantially eliminates the formation of imdesired homopolymer... 

Table 5.14 [86]. Reaction conditions are the same as described for the system natural rubber-methyl methacrylate. The effect of monomer concentration and temperature on styrene polymerization [88] is illustrated in Fig. 5.18. The mastication reaction is slower than in vibromilling. It is useful to underline that in this last case the tests were run at temperatures well below the glass transition temperature of the resins and the system viscosities are nearly the same. The initial polymerization rate is influenced predominantly by the softening effect of added monomer. Subsequently, the reaction is strictly dependent on the properties of the plastomer product [86]. For extensive grafting, a step procedure is suggested to avoid a major initial softening effect [86].

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