Polymerization electron acceptors

Amphoteric am(p)-f9- ter-ik [ISV, ff. Gk amphoteros each of two, ff. ampho both] (ca. 1849) ad). Designating an element or a compound that can behave either as an acid or a base, i.e., as an electron donor or an electron acceptor. Polymerization... 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acryhc acid), poly(methacryhc acid), copolymers of maleic and acryflc acids, tannic acid, naphthoHc and phenoHc compounds, as well as urea and thiourea (42—47). 

These association reactions can be controlled. Acetone or acetonylacetone added to the solution of the polymeric electron acceptor prevents insolubilization, which takes place immediately upon the removal of the ketone. A second method of insolubiUzation control consists of blocking the carboxyl groups with inorganic cations, ie, the formation of the sodium or ammonium salt of poly(acryhc acid). Mixtures of poly(ethylene oxide) solutions with solutions of such salts can be precipitated by acidification. 

It is in the same order as the equilibrium constants of CTC of amine-FN. That is, the stronger the ability of an amine to form CTC with electron acceptors, the faster the rate of pholopolymerization. However, under 313-nm irradiation, local excitation plays a principal role and the rate of polymerization is observed to descend in a different order [80] ... 

This section describes polymerizations of monomer(s) where the initiating radicals are formed from the monomer(s) by a purely thermal reaction (/.e. no other reagents are involved). The adjectives, thermal, self-initialed and spontaneous, are used interchangeably to describe these polymerizations which have been reported for many monomers and monomer combinations. While homopolymerizations of this class typically require above ambient temperatures, copolymerizations involving certain electron-acceptor-electron-donor monomer pairs can occur at or below ambient temperature. 

The ability to ionically polymerize apparently correlates in many cases with the capacity of the substituents to act as electron acceptors (anionic polymerizability) or as electron donors (cationic polymerizability) on the rt-bond of the vinyl group. These relationships should be visible in carefully chosen quantum chemical parameters. 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

Polymerization of cyclic compounds may also occur by ionic mechanisms under the influence of strong acids or bases and in the absence of water and alcohols. Thus, in the presence of a strong acid or electron acceptor (BF3), ethylene oxide may polymerize violently. The mechanism may be the following, where the electron acceptor is represented by the hydrogen ion ... 

Stannylenes are in the first place Lewis acids (electron acceptors) as can be easily derived from the structures of the solids (Chapter 3). When no Lewis bases (electron donors) are present, they may also act as Lewis bases via their non-bonding electron pair (see polymerization of organic stannylenes). 

This idea was put forward first by Scott, Miller and Labes [57] for the polymerization of N-vinylcarbazole by organic electron-acceptors. It was then applied to initiation by the tropylium and other ions [52,58] by reducible metal ions but with emphasis on a possible radical reaction [59] and by sodium chloroaurate in which Au(III) is reduced (see also Section 4.5) [60]. Then Plesch suggested [6] an application of the idea of catalysis by metal halides generally, giving as an example, the following hypothetical scheme ... 

In polymerizations by ionizing radiations in the presence of strong electron acceptors which reduce the reactivity of the electrons, the termination reaction is inhibited, the concentration of ions grows and under these conditions the participation of paired cations becomes relevant (Hayashi et al. 1977 Yamamoto et al. 1977). 

Variations in ferritin protein coats coincide with variations in iron metabolism and gene expression, suggesting an Interdependence. Iron core formation from protein coats requires Fe(Il), at least experimentally, which follows a complex path of oxidation and hydrolytic polymerization the roles of the protein and the electron acceptor are only partly understood. It is known that mononuclear and small polynuclear Fe clusters bind to the protein early in core formation. However, variability in the stoichiometry of Fe/oxidant and the apparent sequestration and stabilization of Fe(II) in the protein for long periods of time indicate a complex microenvironment maintained by the protein coats. Full understanding of the relation of the protein to core formation, particularly at intermediate stages, requires a systematic analysis using defined or engineered protein coats. 

Some polymeric materials become conductive when illuminated with light. For instance, poly(A -vinylcarbazole) is an insulator in the dark, but when exposed to UV radiation it becomes conductive. Addition of electron acceptors and sensitizing dyes allows the photoconductive response to be extended into the visible and near-IR (NIR) regions. In general, such photoconductivity is dependent on the material s ability to create free-charge carriers, electron holes, through absorption of light, and to move these carriers when a current is applied. 

The anionic polymerization of 1,3-dienes yields different polymer structures depending on whether the propagating center is free or coordinated to a counterion [Morton, 1983 Quirk, 2002 Senyek, 1987 Tate and Bethea, 1985 Van Beylen et al., 1988 Young et al., 1984] Table 8-9 shows typical data for 1,3-butadiene and isoprene polymerizations. Polymerization of 1,3-butadiene in polar solvents, proceeding via the free anion and/or solvent-separated ion pair, favors 1,2-polymerization over 1,4-polymerization. The anionic center at carbon 2 is not extensively delocalized onto carbon 4 since the double bond is not a strong electron acceptor. The same trend is seen for isoprene, except that 3,4-polymerization occurs instead of 1,2-polymerization. The 3,4-double bond is sterically more accessible and has a lower electron density relative to the 1,2-double bond. Polymerization in nonpolar solvents takes place with an increased tendency toward 1,4-polymerization. The effect is most pronounced with... 

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