Graft polymerization free radicals

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. 

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. 

White, J. L. and Sasaki, A. 2003. Free radical graft polymerization. Polym-Plastics Technology and... 

The resulting N-radicals, which are all attached to substrate chains, initiate free-radical graft polymerization of suitable vinyl monomers. The method has been applied to synthesize hydrophilic grafts on poly(ether-urethanes)... 

Two popular methods of graft polymerization onto inorganic oxide supports (silica, alumina, and zirconia) are free-radical polymerization [16-34] and anioni-cally initiated polymerization [12, 35-37]. Studies have demonstrated that free-radical graft polymerization onto surface-active vinyl alkoxysilanes is an efficient and controllable method for obtaining a high polymer graft yield in the dense brush ... 

The kinetics of free-radical graft polymerization involves the following species solvent, initiator, monomer, surface vinylsilane, free and grafted polymer radicals, and terminated homo- and surface polymers. The consumption of monomer via covalent attachment to the silane-modified surface occurs by two processes homopolymerization and graft polymerization, with the sum of these two rates representing the overall rate of polymerization. Similar to classical free-radical homopolymerization, the reaction sequence in a free-radical graft polymerization can be divided into fottr main parts (1) initiation, (2) propagation, (3) chain transfer, and (4) termination. 

M Chaimberg. Free-radical Graft Polymerization of Vinyl Pyrrolidone. PhD dissertation, University of California, Los Angeles, 1989. 

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