Anionic polymerization of monomers containing functional groups. 13. Anionic polymerizations of 2-, 3-, and 4-(3,3-dimethyl-1-butynyl)styrenes, 2-, 3-, and 4-(1-hexynyl)styrenes, and 4-(phenylethynyl)styrene

The anionic polymerizations of 4-, 3-, and 2-(3,3-dimethyl-1-butynyl)styrenes (3a, 3b, and 3c), 4-, 3-, and 2-(1-hexynyl)styrenes (4a, 4b, and 4c), and 4-(phenylethynyl)styrene (5) were carried out in THF at -78 degrees C with oligo(alpha-methylstyryl)dipotassium and sec-butyllithium. The polymerizations of these monomers proceeded quantitatively at -78 degrees C for 0.5 h. The resulting polymers all possessed the predicted molecular weights based on the molar ratios of monomer to initiator and the narrow molecular weight distributions (M-w/M-n = 1.03-1.15). The living character of the propagating carbanion derived from these monomers was further confirmed by the quantitative initiation efficiency in the second-stage polymerization. A variety of novel block copolymers with well-defined chain structures were synthesized by the sequential block copolymerization of 3a, 4a, 5, and 4-((trimethylsilyl)ethynyl)styrene (1a) with isoprene, styrene, 2-vinylpyridine, and tert-butyl methacrylate. Furthermore, the relative reactivities of the monomers and the resultant living polymers were evaluated from the results of the anionic block copolymerizations. Higher reactivity of 3a, 4a, 5, and la and lower nucleophilicity of their living polymers were clearly demonstrated, compared with those of styrene and living polystyrene, respectively. Both of these features can be explained by the electron-withdrawing character of the ethynyl substituents and the extended pi-conjugation system including the carbon-carbon triple bond. The anionic polymerizabilities of 3a, 4a, 5, and 1a are estimated to be the same level of 2-vinylpyridine.