Electron deficient monomer

More recently, the copolymerization of ethyl cyanoacrylate with other 1,1 disubstituted electron deficient monomers and the effect of the monomers on adhesive properties have been studied. Monomers, such as diethyl methylene-malonate (DEMM), 8, were prepared [6,7]. Their homopolymers and copolymers... 

In the absence of heteroatom containing substituents (e.g. halo-, cyano-), at or conjugated with the radical center, carbon-centered radicals have nucleophilic character. Thus, simple alkyl radicals generally show higher reactivity toward electron-deficient monomers (eg. acrylic monomers) than towards electron-rich monomers (e.g, VAc, S) - Table 3.6. 

In the case of electron-deficient monomers (e.g, acrylics) it is accepted that reaction occurs by initial addition of the sulfate radical anion to the monomer. Reactions of sulfate radical anion with acrylic acid derivatives have been shown to give rise to the sulfate adduct under neutral or basic conditions but under acidic conditions give the radical cation probahly by an addition-elimination process. 

Alkyl mercuric hydrides are generated in situ by reduction of an alkyl mercuric salt with sodium borohydridc (Scheme 3.91). Their use as radical traps was first reported by Hill and Whitesides491 and developed for the study of radical-olefin reactions by Giese,489490 Tirrell492 and coworkers. Careful choice of reagents and conditions provides excellent yields of adducts of nucleophilic radicals (e.g. -hexyl, cyclohexyl, /-butyl, alkoxyalkyl) to electron-deficient monomers (e.g. acrylics). 

Addition of dithioacids to electron-deficient monomers (MA, MMA, AN) proceeds by Michael addition to pul sulfur at the unsubslituted end of the double bond.479... 

Only few reducible dyes—such as xanthene and acridine dyes—can directly react with electron deficient monomers but the efficiency remains low. As a consequence,... 

The kinetics of copolymerization and the microstructure of copolymers can be markedly influenced by the addition of Lewis acids. In particular, Lewis acids are effective in enhancing the tendency towards alternation in copolymerization of donor-acceptor monomer pairs and can give dramatic enhancements in the rate of copolymerization and much higher molecular weights than are observed for similar conditions without the Lewis acid. Copolymerizations where the electron deficient monomer is an acrylic monomer e.g. AN, MA, MMA) and the electron rich monomer is S or a diene have been the most widely studied." Strictly alternating copolymers of MMA and S can be prepared in the presence of, for example, dictliylaluminum scsquichloridc. In the absence of Lewis acids, there is only a small tendency for alternation in MAA-S copolymerization terminal model reactivity ratios are ca 0.51 and 0.49 - Section 7.3.1.2.3. Lewis acids used include EtAlCT, Et.AlCL ElALCL, ZnCT, TiCU, BCl- LiC104 and SnCL. 

As demonstrated earlier, the addition of other electron deficient monomers to copolymerize with the cyanoacrylate monomer has not proven to be an effective means of modifying the physical properties of cyanoacrylate-based adhesives. The most effective adhesive improvements have come through the incorporation of various additives, which modify the adhesive physical properties but do not copolymerize with the monomers. These product development efforts have been quite successful in improving the properties of alkyl cyanoacrylate-based adhesives to the point where they can now be used in a huge variety of applications. 

Chain-Growth Polymerization of Electron-Deficient Monomers... 

Until recently, catalyst-transfer polycondensations were limited to the preparation of p-type 7i-conjugated polymers and block copolymers comprising relatively simple electron-rich building blocks (such as thiophene). On the other hand, well-defined conjugated donor-acceptor alternate copolymers and donor-acceptor all-conjugated block copolymers are needed for practical applications. Very recently, controlled polymerizations of a few electron-deficient monomers were also reported." ... 

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