It has been believed that the anionic polymerization of styrene derivatives carrying ketone moieties is very difficult, since electrophilic carbonyl moieties readily react with the nucleophilic anionic initiators and the propagating carbanions. Furthermore, acidic alpha-hydrogens in the ketone moieties also prohibit the anionic polymerization via the proton abstraction. Therefore, a well-defined poly(4-acetylstyrene) has been obtained by the anionic polymerization of tert-butyldimethylsilyl enol ether of 4-acetylstyrene and the following deprotection. In this case, the electrophilic acetyl group was converted to the electron-rich silyl enol ether of monomer, and the acidic alpha-hydrogen of CH3CO group was eliminated to prevent the side reaction with the basic anionic species. In this study, we focus on the anionic polymerization behavior of a novel styrene derivative, 1-adamantyl 4-vinylphenyl ketone (1), which has a bulky adamantyl substituent without acidic alpha-hydrogen. No polymerization of 1 occurred with sec-BuLi in THF at –78 °C for 48 h, and 1 was quantitatively recovered from the polymerization system. On the other hand, the mixture of 1 and diphenylmethylpotassium (Ph2CHK) showed a characteristic dark red color in THF at –78 °C, and the polymerization of 1 quantitatively proceeded within 24 h to form the polymers with predicted molecular weights and narrow molecular weight distributions (Mw/Mn = 1.1). These results indicate that bulky pai-conjugated initiators and larger counter cation of initiators are preferable for the successful polymerization of styrene derivative carrying ketone functionality to prevent side reactions as well as the bulky adamantyl group. In addition, the propagating carbanion of poly(1) was effectively stabilized by the electron-withdrawing carbonyl group. The resulting poly(1) had a high glass transition temperature at 193 °C, indicating the effect of introduced bulky adamantyl group.

Living anionic polymerization of 1-adamantyl 4-vinylphenyl ketone

251st National Meeting (2016)

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