Grafting, anionic

Strongly acidic monomers, such as nitroethylene, can only be grafted under anionic conditions. Also, anionic grafting is useful for conventional monomers such as acrylonitrile and methylmethacrylate. In addition to the... 

Anionic grafting of 0-propiolactone onto acrylate copolymers was extensively studied333-33s. ... 

Anionic grafting methods (vide infra) can be applied to the synthesis of comb-shaped polymers. As an example, a polystyrene backbone is partially chloromethylated (under mild conditions) and used as an electrophilic deactivator for a living polystyrene 89). The grafting onto process yields well defined species that have been characterized accurately. The branches are distributed randomly along the backbone 90). 

Gauthier, M. and Mdller, M. Uniform highly branched polymers hy anionic grafting Arborescent graft polymers. Macromolecules, 24, 4548, 1991. 

A Cationic Graft Copolymer of Lignin. The applications of the anionic graft copolymers described above are many but the negative charge on the polymer or the behavior of the anionic polymer under application conditions often limit the utility of these materials. 

Concerning the synthesis of graft copolymers, Jedlinski et al. have prepared poly(MMA-g-(3BL) copolymers via anionic grafting of 3BL from a modified PMMA backbone [85]. PMMA chains were partially saponified by potassium hydroxide and complexed by 18C6 crown ether so as to act as multifunctional mac-... 

The anionic graft polymerization of vinyl monomers onto carbon fiber or graphite powder initiated by metalized carbon fiber has been investigated. The metalation of polycondensed aromatic rings of a carbon fiber surface was achieved by treatment of the carbon fiber with BuLi in Ar,Ar,Ar, AT -tetramethylethylenediamine. The anionic polymerization of methylmethacrylate and styrene was reported. No grafting was observed when carbon fiber was treated simply with BuLi in THF or toluene [44,45]. 

Anionic Polymerization. Anionic grafting polymerization initiated on the inorganic particles is also possible to give composite particles. The amino group incorporated into the surface of silica caused anionic polymerization of N-carboxy-a-amino acid anhydride to give poly(amino acid) grafting [Reaction (8)1 (21). 

Table 4. A summary of the anionic graft-from polymerization reactions by using lithiated poly(ethylene-co-p-methylstyrene) as initiator...

Table 4 summarizes the reaction conditions and the experimental results. Overall, the experimental results clearly show a new class of PE graft copolymers which can be conveniently prepared by the tranformation of metallocene catalysis to anionic graft-from polymerization. 

Anionic Graft Copolymerization onto Polystyrene. We have been able to initiate graft copolymerization onto polystyrene by the use of anionic initiators but even here the reaction does not proceed as one may expect. Once again one would likely think that the benzylic hydrogen is the most acidic and should be the one removed by a lithium reagent... 

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). 

Zilkha, A., B. A. Feit, and A. Bar-Nun Anionic graft copolymerization of vinyl monomers on natural polyhydroxy compounds, their derivatives, and on synthetic polyhydroxy polymers. Israeli Pat. 15 962, Oct. 1962 C. A. 58, 5803 (1963). 

Polyvinylchloride can also be anionically grafted. With this method the chain breaking property of alkyl halides is utilised whereby the active anionic polymer is terminated with the alkyl group in the case of PVC the anionically synthesised polymer becomes the grafted chain 21). Hereafter, this review will be concerned only with those grafting methods involving azo functions. 

Anionic graft-polymerization of paraformaldehyde onto starch and dextrin has been effected in methyl sulfoxide solution, polymerization being initiated by the carbohydrate potassium alcoholate formed from the reaction of the carbohydrate with naphthalene potassium, a metallation procedure not previously described for carbohydrates.220... 

The discovery of the powerful metalating agent, n-BuLi-N,N,N, N -tetramethylethylenediamine, opened a new chapter in anionic grafting. This complex has been reported to metalate toluene and benzene within a few minutes to give quantitative yields of benzyllithium and phenyl-lithium, respectively (4). It also has been reported to polylithiate aromatic compounds (24, 25). 

Better control of grafting and less homopolymer formation is achievable in ionic reactions than can be obtained in free-radical reactions. Anionic grafting via backbone initiation has been demonstrated (22) with caprolacteim on macromolecular ester sites of styrene/methyl methacrylate copolymers. Cationic grafting of isobutylene onto poly(vinyl chloride) with the aid of aluminum alkyl has been carried out by J. P. Kennedy (23). 

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