Living anionic polymerization of monomers with functional groups, 15 - Anionic polymerization and reaction of styrene and 1,1-diphenylethylene derivatives substituted with alkoxymethyl groups

Anionic polymerizations of ortho-, meta-, and para-substituted styrene derivatives with alkoxymethyl groups have been studied. It was found that their polymerization behaviors were significantly affected by the substituted position of the alkoxymethyl group. The meta- and ortho-substituted styrenes successfully underwent living anionic polymerization in THF at -78°C with the initiators having K+ as a counter cation such as cumylpotassium and oligo(α-methylstyryl)potassium, and potassium napthalenide. On the other hand, no appreciable polymerization of the para-substituted styrenes occurred under the identical conditions. The similar positional effect was also observed in the reactions of polystyryllithium with o,o-, m,m-, and p,p-disubstituted 1,1-diphenylethylene (DPE) derivatives with methoxymethyl groups. Instead of the expected 1:1 addition products, undesirable high molecular weight polymers were formed especially using p,p-disubstituted DPE. In order to account for such anomalous polymerization and reaction behaviors of the para-substituted styrene and DPE derivatives, we postulated the reaction pathway based on the anion-mediated rearrangement followed by a 1,6-elimination reaction to produce very reactive p-xylylene and/or biradical intermediates that were coupled to each other. This postulated reaction pathway was discussed throughout the results of the stoichiometric reactions of sec-BuLi with p-methoxymethylstyrene and 1-(4-methoxymethylphenyl)-1-phenylethylene.