Anionic techniques, grafting

An anionic technique by indirect grafting was proposed for N-metallation of Nylon by Yamaguchi (153-155), in which alcali metals dissolved in liquid ammonia displace the amidic hydrogen atoms. Nylon derivatives and graft copolymers can be synthetized from the N-metallated Nylon (153). For ethylene oxide as grafting monomer, the metallated fibers were soaked in a tetrahydro-furan solution of the monomer, at 60° C (154). Methyl methacrylate is grafted on Nylon with a conversion over 90% by this technique (155). Other procedures involve the use of sodium methoxide in methanol solution and subsequent anionic graft copolymerization of acrylonitrile in a tetrahydrofuran solution (156). 

Arborescent graft copolymers having a highly branched PS core and a PEO shell were prepared by a combination of anionic polymerization, grafting onto and from techniques [278]. The synthetic procedure is described in the following scheme (Scheme 107). 

Bamford, Eastmond and coworkers have employed metal complexpolymeric halide redox systems to initiate block and graft copolymerization. The polymeric halides can be synthesized by a variety of techniques, including radical polymerization,281 anionic polymerization (Scheme 7.28),"so... 

Recently it has been shown that anionic functionalization techniques can be applied to the synthesis of macromonomers — macromolecular monomers — i.e. linear polymers fitted at chain end with a polymerizable unsaturation, most commonly styrene or methacrylic ester 69 71). These species in turn provide easy access to graft copolymers upon radical copolymerization with vinylic or acrylic monomers. 

Anionic polymerization techniques can also be applied to the synthesis of graft copolymers 6 7 87 1U). Kennedy s classification 134) is used here as shown in Scheme 5. 

The purpose of this review is to show how anionic polymerization techniques have successfully contributed to the synthesis of a great variety of tailor-made polymer species Homopolymers of controlled molecular weight, co-functional polymers including macromonomers, cyclic macromolecules, star-shaped polymers and model networks, block copolymers and graft copolymers. 

Gauthier and M oiler [4] described in 1991 the use of anionic polymerization and grafting techniques to prepare poly(styrenes) with a dendritic structure. Styrene is well suited to be incorporated into a synthetic scheme aimed at producing... 

Among the two ionic polymerization techniques mentioned above, a living anionic polymerization should show the best possible control of polymer architecture and composition. Mono dispersed homopolymers, complex-block, graft, star, and miktoarm architectures have been accessible primarily by anionic polymerization methods [22]. They have been used to grow polymer brushes from various small particles such as silica gels graphite,carbon black, and flat surfaces [23-26]. Recent results have been reported on living anionic polymerizations on clay [27] and silica nanoparticles [28,29]. 

Diene substrate latices were prepared by seeding techniques following the scheme shown in Figure 1. Persulfate anion was the initiator, and an alkyl aryl sulfonate was the emulsifier. Reaction time varied between 13 and 33 hours. Since all the substrates were prepared by similar techniques, the volumetric swell index and gel gravimetric data (toluene) varied little with particle size. Small differences in swell and gel characteristics should not be a variable in this study because of the polarity of the grafting monomer mixture and rapidity of the graft reactions. 

Ionic polymerisation is a well-known technique for the preparation of graft copolymers but the fate of these reactions is determined by the reaction conditions. Since the discovery of living polymerisation , (anionic polymerisation) [67] it has become an excellent method for the synthesis of block and graft copolymers. In anionic polymerisation the graft copolymerisation is initiated by the anion generated by the reaction of bases with acidic protons in the polymer chain as shown in Scheme 2. 

---