Oxygen reaction with polymeric anions

One of the earliest examples of this methodology involves the reaction of a polymeric anion (formed by living anionic polymerization) with molecular oxygen to form a polymeric hydroperoxide which can be decomposed either thermally or, preferably, in a redox reaction to initiate block polymer formation with a second monomer (Scheme 7.25). However, the usual complications associated with initiation by hydroperoxides apply (Section 3.3.2.5). 

Saturated hydrocarbons have lower electron affinity than unsaturated hydrocarbons. In dry argon, the decalin anion radicals are formed, if at all, in extremely low concentration. It suggests that their further reactions are insignificant. In the presence of decalin, no wear occurs. In dry or wet air, decalin works worse, but still effectively. The anion radicals of oxygen, which are formed in greater concentration than that of the anion radicals of decalin, can initiate decalin oxidation. Oxidation products were capable of accepting exoelectrons and were involved in further reactions, with the formation of polymeric or organometallic lubricants. 

Anionic polymerizations must be carried out in the absence of water, oxygen, carbon dioxide, or any other impurities which may react with the active polymerization centers. Glass surfaces carry layers of adsorbed water which react with carban-ions. It is necessary to take special precautions, such as flaming under vacuum, to remove this adsorbed water in laboratory polymerizations. Anionic reactions are easier to carry out on a factory scale, however, because the surface-to-volume ratio is much less in large reactors. 

The ether oxygen is a Lewis base (electron donor), and polymerization of vinyl and cyclic ethers can be initiated by reaction with an ion pair comprising an acidic cation and a weakly nucleophilic base. These monomers do not polymerize by free-radical or anionic processes. Thio ethers behave similarly. 

The mapping shown in Fig. 1 includes references to SBR and styrene block copolymers in the PB search. Removing these citations from the database reduced the number to 4297, which can be seen mapped in Fig. 3. the area of high activity is centered on hydroxy terminated PB (HTPB). Low-Mn HTPB can be prepared by a variety of polymerization processes such as radical, anionic, or even using acyclic diene metathesis (ADMET).f The HTPB has a variety of uses as a propellant. " Other uses include reaction with epoxy resins, nylon, urethane, or even in the formulation of adhesives.t" The use of HTPB as an oxygen scavenger in polyamide, polyvinyl alcohol, and multilayer... 

Anionic polymerization proceeds by nucleophilic reaction of the anion with the carbonyl and the subsequent acyl-oxygen cleavage. This reaction produces an alkoxide end group, which continuously propagate to prepare polylactic acid (Figure 7.5) [12]. 

Lactide anionic polymerizations proceed by the nucleophilic reaction of the anion with the carbonyl group and the subsequent acyl-oxygen bond cleavage, which produces an alkoxide end-group, which continues to propagate. The general mechanism for this anionic polymerization has been discussed in various publications [2, 3, 15, 16]. Some authors [16] have shown that the use of alkoxides, such as potassium methoxide, can yield weU-defined polymers with negligible racemization. 

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