Anionic polymerization of monomers containing functional groups, 14 - Anionic polymerizations of aryl 4-vinylbenzoates

摘要

Full Paper: Anionic polymerizations of phenyl (2a), 4-methoxyphenyl (2b), 2-methylphenyl (2c), 2-tert-butylphenyl (2d), 3,5,-di-tert-butylphenyl (2e), 2,6-dimethylphenyl (1f), 2,6-diisopropylphenyl (2g), 2,6-di-tert-butyl-4-methyphenyl (2h), and 2,6-di-tert-butyl-4-methoxyphenyl (2i) 4-vinylbenzoates were carried out in THF at 78 degrees C with diphenylmethylpotassium and oligo(a-methylstyrl)lithium and -dipotassium. No apparent polymerizations of 2a-2e occurred probably due to the inherent side reactions such as nucleophilic attack of the anionic initiators toward the ester carbonyl groups. On the other hand, the polymerizations of 2f-2i, the monomers possessing bulky aryl ester substituents, certainly proceeded to afford the polymers in quantitative yields. The molecular weight distribution (MWD) of poly(2f) was broad ((M) over bar(w)/(M) over bar(n) = 1.3-1.8), indicating partial side reactions during the course of the polymerization. By contrast, the resulting poly(2g-2i) possessed narrow MWDs ((M) over bar(w)/(M) over bar(n) = 1.1) and predicted molecular weights based on the molar ratios between monomers to initiators. It was thus demonstrated that the steric hindrance around the ester carbonyl group was essential to obtain polymers having well-defined chain structures via controlled anionic polymerizations of aryl 4-vinylbenzoates. Novel tailored block copolymers, polyisoprene-block-poly(2h), poly(2h)-block-polystyrene- block-poly(2h), poly(tert-butyl methacrylate)-block-poly(2h), and poly(2h)-block-poly(2-isopropenylbenzoxazole) were synthesized by the sequential copolymerization of 2h and the corresponding comonomers. It was elucidated from the results of block copolymerization that anionic polymerizability of 2h was apparently higher than that of styrene because of the electron-withdrawing effect of the COOAr substituent. References: 28