Polymerization, phosphate anions

NaAs03 has an infinite polymeric chain anion similar to that in diopside (pp. 349, 529) but with a trimeric repeat unit LiAs03 is similar but with a dimeric repeat unit whereas /6-KASO3 appears to have a cyclic trimeric anion As309 which resembles the cyc/o-trimetaphosphates (p. 530). There is thus a certain structural similarity between arsenates and phosphates, though arsenic acid and the arsenates show less tendency to catenation (p. 526). The tetrahedral As 04) group also resembles PO4) in forming the central unit in several heteropoly acid anions (p. 1014). 

Fig. 3 Binding interactions between polymeric amine hydrochloride gels and phosphate anions...

The living cationic polymerizations discussed above are invariably based on the nucleophilic iodide counteranion (activation of the carbon-iodine terminal bond Eq. 3). It is expected, however, that similar living processes are equally possible with other counteranions that can exert, as the iodide anion does, a suitably strong nucleophilic interaction with the growing carbocation. We have in fact found the phosphate anions to meet this requirement (10). Similarly to hydrogen iodide, monoacidic phosphate esters [H0P(0)R 2 R alkyl, alkoxyl, etc.] like diphenyl phosphate ( ) form a stable adduct 5) with a vinyl ether (Eq. 5). Zinc chloride or iodide then activates the phosphate bond in 5 by increasing its polarization (as in 6), and living cationic polymerization proceeds via an intermediate (7) where the carbocationic site is stabilized by a phosphate anion coupled with the zinc halide activator. 

In acidic solution, vanadium(V) exists as the univalent cation, V02. The hydrolytic behaviour of this ion is quite complex, forming a large number of monomeric and polymeric hydrolysis species. In this review, these species are related to reaction (2.5) (M = V02 ). Species with 1, 2, 4, 5 and 10 V02" molecules are believed to form, although other species have been reported. Once the univalent cation is hydrolysed as V020H(aq), or equivalently HjVOjfaq), the chemistry it displays is quite similar to that of the phosphate anion, in terms of its ability to form polymeric species and the strength of the various steps of dissociation of phosphoric acid. 

The surfactants used in the emulsion polymerization of acryhc monomers are classified as anionic, cationic, or nonionic. Anionic surfactants, such as salts of alkyl sulfates and alkylarene sulfates and phosphates, or nonionic surfactants, such as alkyl or aryl polyoxyethylenes, are most common (87,98—101). Mixed anionic—nonionic surfactant systems are also widely utilized (102—105). 

The salts containing polymeric anions in die solid state melt retain die anion stiiicture, e.g. and on melting, while die phosphates in which die... 

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