Precise synthesis of high Tg adamantane-containing polystyrene derivatives via anionic polymerization

Abstract

The precise synthesis of poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) was attempted via anionic polymerization of 4-(4-(N-adamantylimino)methyl)phenylstyrene to examine the substituent effect of polystyrene derivatives on their glass transition temperature (T_g) and the reactivity of 4-(4-(N-adamantylimino)methyl)phenylstyrene. The anionic polymerization of 4-(4-(N-adamantylimino)methyl)phenylstyrene was carried out with diverse initiator systems, such as oligo(α-methylstyryl)lithium, oligo(α-methylstyryl)dipotassium, and (1,1,4,4-tetraphenylbutanediyl)dipotassium, in tetrahydrofuran at −78 °C. It produced well-controlled poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) with the expected molecular weight and narrow molecular weight distribution. Sequential block copolymerization with 2-vinylpyridine as the first monomer resulted in the successful synthesis of well-defined poly(2-vinylpyridine)-block-poly(4-(4-(N-adamantylimino)methyl)phenylstyrene), indicating high monomer reactivity of 4-(4-(N-adamantylimino)methyl)phenylstyrene. The postpolymerization modification of poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) and poly(2-vinylpyridine)-block-poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) led to the quantitative preparation of poly(4,4′-formylphenylstyrene) and poly(2-vinylpyridine)-block-poly(4,4′-formylphenylstyrene), respectively, with an electrophilic formyl group. Thermogravimetric analysis and differential scanning calorimetry confirmed that poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) prepared in this study had high thermal stability and a high T_g owing to the bulky and rigid adamantyl group. In particular, among the adamantane-containing polystyrene derivatives reported thus far, high molecular weight poly(4-(4-(N-adamantylimino)methyl)phenylstyrene) showed the highest T_g (268 °C).