Free-radical grafting

Free radical grafting without using a free radical initiator. 

FIGURE 11.2s Reaction scheme for styrene-assisted free radical grafting of glycidyl methacrylate onto natural ruhher. (From Suriyachi, P., Kiatkamjomwong, S., and Prasassarkich, P., Rubber Chem. TechnoL, 77, 914, 2004.)... 

A general reaction mechanism for the grafting of MA onto EPM is given in Figure 13.3 [15,16]. Free-radical grafting of MA starts with the decomposition of the radical initiator, usually a peroxide [15,18]. The peroxide decomposes at elevated temperamres into the corresponding oxy radicals, which may further degrade to alkyl radicals and ketones. These oxy and alkyl radicals abstract... 

Table 1. Mechanism of the free-radical graft of MA onto iPP with DCP as the initiator...

Photoinduced free radical graft copolymerization onto a polymer surface can be accomplished by several different techniques. The simplest method is to expose the polymer surface (P-RH) to UV light in the presence of a vinyl monomer (M). Alkyl radicals formed, e.g. due to main chain scission or other reactions at the polymer surface can then initiate graft polymerization by addition of monomer (Scheme 1). Homopolymer is also initiated (HRM-). 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

A major commercial effort is the free radical grafting of various styrenic, vinylic, and acrylic monomers onto cellulose, starch, dextran, and chitosan. Grafting has been... 

Kiefer et al. (4) prepared proton-conductive electrolytes for use in fuel cells by free radically grafting vinyl-phosphonic acid and vinylsulfonic acid onto a polyether ketone substrate. 

Poly( ethylene oxide)-block-poly (propylene oxide)-hZock-poly(ethylene oxide)-g-poly(acrylic acid) (PEO-fc-PPO-fc-PEO-g-PAA, Pluronic-PAA) graft copolymers were synthesized by free radical grafting copolymerization of acrylic acid monomers onto PEO-h-PPO-h-PEO (Pluronic F127) and the aqueous solution properties were characterized by Bromberg [133, 134]. Chiu et al. [135] reported on the micellization of (non-ionic) poly(stearyl methacrylate)-gra/f-poly(ethylene glycol) graft copolymers. 

Acrylic acid and derivatives have been free radically grafted onto the backbone of biodegradable polycaprolactone and poly(lactic-co-glycolic acid). These functionalized biocompatible materials are useful as drug delivery agents. 

Wang used reactive-extrusion polymerization with 2,5-di-methyl-2,5-di-t-bu-tylperoxy hexane to prepared a graft copolymer, (11), by free radically grafting polyethylene-glycol malonic acid onto the biodegradable substrate of poly((3-hydroxybutyrate-co- p-hydroxy valerate). 

Fig, 4, Free radical grafting fi-om azo modified poly(organosiloxane)s... 

Free-radical graft polymerization may be carried out in several ways1,5. However, only a few methods can be applied to the permanent production of graft-modified cellulose materials9"12, and the development of industrial methods to ensure the rapid (30-60 s) grafting of the required amount of a polymer onto cellulose is still a major problem. 

Vinyl Monomers and Other Reagants in Free Radical Grafting. 301... 

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