Methoxystyrene, anionic polymerization

The solvation of ion pairs may also arise from intramolecular interaction. For example, the high reactivity of living poly(2-vinylpyridine) is probably caused by the intramolecular solvation of the Na+ ion by the adjacent pyridine rings (16, 23, 32). Interesting example of such a solvation has been discovered by Smets and van Beylen (30), who studied anionic polymerization of p- and o-methoxystyrene. The ion pair of the latter living polymer, but not of the former, showed exceptional reactivity, and the model reveals that only the o-methoxy group can participate in the intramolecular solvation. 

Predict the order of reactivity (and justify your prediction) of the given monomers, (a) Styrene, 2-vinylpyridine, 3-vinylpyridine, and 4-vinyl pyridine in anionic polymerization, (b) Styrene, p-methoxystyrene, p-chlorostyrene, and p-methylstyrene in cationic polymerization. 

Styrene undergoes anionic polymerization at a faster rate than / -methoxystyrene. 

Initiations of polymerizations of vinyl and other monomers by metal alkyls generally take place by anionic mechanisms. This is discussed further in this chapter. There are, however, reports in the literature of cationic polymerizations that are initiated by some metal alkyls. These are polymerizations of monomers like vinyl ethers, o- and p-methoxystyrene, and isobutylene " that are initiated by compounds like dialkyl aluminum chloride. 

Five tri-and tetra-substituted electron-poor olefins 1-5 containing 3-anionic leaving groups initiated cationic polymerization of p-methoxystyrene with widely varying rates. Compounds 1 and 2 were highly active organic initiators. 

An example of the first technique is provided by the polymerization of isobutyl vinyl ether (IBVE) on poly(p-methoxystyrene) (p-MOS). Iodine-initiated polymerizations of p-MOS at —15 conducted in solvents of low polarity or in the presence of excess common anions produce non-dissociated active centres that can... 

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