Phenylated ethylenes, radical anions

The cause of noninterpenetration in Vollmert s experiments was left up in the air because of the possibility of thermodynamic (and even steric) incompatibility. Braun (1976) endeavoured to circumvent this ambiguity by carrying out crosslinking reactions on identical polymer molecules. This was based upon the observation that 1,1-diphenylethylene in the presence of sodium metal forms radical anions that rapidly dimerize in quantitative yield. This reaction was applied to poly(l-phenyl-l-(4-vinylphenyl) ethylene-costyrene), which can in principle undergo both intramolecular and intermolecular reactions. Intramolecular reactions cause coil contraction, which is manifest by a decrease in the intrinsic viscosity of the polymer solutions. Intermolecular reactions stiffen the polymer chains, their structure... 

TABLE 7.5. Localization Energies SE for the Most Reactive Positions (O) hi Phenyl Derivatives of Ethylene and the Behavior of the Corresponding Radical Anions in Solution... 

Typical chain polymerizations are those of monomers containing the carbon-carbon double bond, e.g., ethylene, isobutylene, isoprene, styrene and acrylonitrile. Polymerization is initiated by radical, cationic, anionic or Ziegler-Natta (coordination) initiators. All monomers except 1-alkylethylenes, 1,1-dialkylethylenes and vinyl ethers undergo radical polymerization. Ionic chain polymerizations are much more selective than radical polymerizations. Cationic initiation is limited to monomers containing electron-donating substituents, e.g., alkoxy, 1,1-dialkyl, phenyl and vinyl. Anionic initiation is limited to monomers with electron-withdrawing substituents, e.g., CN, COOR, phenyl and vinyl. 1-Alkylethylenes such as propylene are polymerized only by... 

Electro-optical modulators are other examples whose efficiency is enhanced in the presence of ion-radicals. These devices are based on the sandwich-type electrode structures containing organic layers as the electron/hole-injecting layers at the interface between the electrode and the emitter layer. The presence of ion-radicals lowers the barrier height for the electron or hole injection. Anion-radicals (e.g., anion-radicals from 4,7-diphenyl-l,10-phenanthroline—Kido and Matsumoto 1998 from tetra (arylethynyl) cyclooctatetraenes—Lu et al. 2000 from bis (1-octylamino) perylene-3,4 9,10-bis (dicarboximide)s— Ahrens et al. 2006) or cation-radicals (e.g., cation-radicals from a-sexithienyl—Kurata et al. 1998 l,l-diphenyl-2-[phenyl-4-A/,A- /i(4 -methylphenyl)] ethylene— Umeda et al. 1990, 2000), all of them are electron or hole carriers. 

The value of 0 in a particular radical can be estimated by comparison of the experimental half-wave potential and HFSC with the results obtained from a series of HMO calculations using different assumed values of 0. A large number of phenyl-substituted aromatic compounds [62] and ethylenes [63] have been treated in this fashion. Similar evidence for the twisting of the nitro group in nitroaromatic anion radicals is summarized in Reference 1. Restricted rotation of alkyl substituents is also discussed in Reference 1, but this torsion does not significantly affect the electrochemical behavior. 

The intermediate expected to be formed upon protonation of 1,1-diphenyl-ethylene anion radical is [4 R = phenyl]. An LSV study has confirmed the structural hypothesis (Lerflaten and Parker, 1982a). Protonation by methanol... 

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