Polymerization, anionic vinyl monomers grafting

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]. 

Recently, the methods of anionic graft polymerization of vinyl monomers have been adopted for graft pol3nnerization to cellulose, and a few papers have appeared in the literature.All of these involve the "grafting from" process. Alkali metal cellulosates are used as initiators for the anionic graft polymerization of vinyl monomers (Scheme 1). Although this method seems more versatile it does not allow adequate structural control, and it often yields rather polydisperse samples. 

Here we discuss dispersion polymerizations that are not related to vinyl monomers and radical polymerization. The first one is the ring-opening polymerization of e-caprolactone in dioxane-heptane (30). A graft copolymer, poly(dodecyl acrylate)-g-poly(e-caprolactone), is used as a stabilizer. The polymerization proceeds via anionic or pseudoanionic mechanism initiated by diethylaluminum ethoxide or other catalysts. The size of poly(caprolactone) particles depends on the composition of stabilizer, ranging from 0.5 to 5 i,m. Lactide was also polymerized in a similar way. Poly(caprolactone) and poly(lactide) particles with a narrow size distribution are expected to be applied as degradable carriers of drugs and bioactive compounds. 

PS macromonomers have been efficiently applied to the synthesis of well-defined polymer hybrids with controlled length of grafts. They are, in general, prepared via living anionic polymerization of styrene monomers and their treatment with vinyl compounds, such as -allyl, -undecenyl, and styryl compounds. 

A patent (71) describes a combination of anionic and radical techniques to produce a variety of graft polymers. The synthesis proceeds via a capped anionic block polymer, the capping producing a polymerizable vinyl end unit. The capped polymer is then free-radical polymerized with a selected vinyl monomer to produce the graft polymer ... 

There are numerous ways of attaching polymers to a solid surface. Examples are photo cross-linking of pre-formed polymer chains, in-situ atom transfer radical polymerization (ATRP), electron beam irradiation,and plasma polymeriza-tion.f Electrochemical techniques are particularly suited for conducting substrates. For example, Palacin et al. have grafted vinylic monomers from anhydrous solutions.f This technique is mainly based on an anionic polymerization and leads to a covalent link between the polymer and the metal. Schuhmann et al. 

Major commercial synthetic specialty polymers are made by chain-growth polymerization of functionalized vinyl monomers, carbonyl monomers, or strained ring compounds. Depending on monomer structure, the polymerization may be initiated free radically, anionically, or cationically. Copolymers or terpolymers with random, alternating, block, or graft sequences can be prepared under appropriate reaction conditions. There are numerous mediods used to prepare specialty polymers in the research laboratory. However, only a few are of commercial interest. Of particular commercial interest is synthesis of specialty polymers in solutions, dispersions, suspensions, or emulsions. 

From the environmental viewpoint, the solvent used for coating or film-forming materials is important. The macromonomer technique was therefore applied to form a miniemulsion system of PLA-graft copolymers, as a typical example of the use of water as a green solvent. Four MMm macromonomers (m = 4, 6, 8, and 12 Scheme 1) were prepared and used as comonomer. In the copolymerization, BMA or BA was employed as the vinyl monomer (reaction 2, Scheme 1) [41]. Sodium dodecyl sulfate (SDS) and sodium dioctyl sulfosuccinate (PEREX), both anionic, were found to be appropriate surfactants. To form a stable emulsion system, ultrasound sonication was applied to the mixture of comonomers and surfactant in water before the copolymerization. Then, radical copolymerization was carried out (Table 3) [41, 42]. Relevant to the use of water as reaction solvent. Sect. 4 describes the use of green solvents in enzyme-catalyzed polymerizations. 

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