Living Anionic Polymerization of <i>N</i>‑(1-Adamantyl)‑<i>N</i>‑4-vinyl­benzylidene­amine and <i>N</i>‑(2-Adamantyl)‑<i>N</i>‑4-vinyl­benzylidene­amine: Effects of Adamantyl Groups on Polymerization Behaviors and Thermal Properties

Abstract

The anionic polymerization of <i>N</i>-(1-adamantyl)-<i>N</i>-4-vinylbenzylidene­amine (<b>1</b>) and <i>N</i>-(2-adamantyl)-<i>N</i>-4-vinylbenzylidene­amine (<b>2</b>) was performed using various initiators, such as oligo­(α-methylstyryl)­dipotassium, potassium naphthalenide, diphenyl­methylpotassium, and diphenyl­methyllithium, in THF at −78 °C for 1 h to investigate the effects of adamantyl groups on the polymerization behaviors and thermal properties of the resulting polymers. The well-defined poly­(<b>1</b>) and poly­(<b>2</b>) with predictable molecular weights and narrow molecular weight distributions were successfully obtained, indicating that the bulky adamantyl groups effectively protected the carbon–nitrogen double bond (CN) from the nucleophilic attack of the initiators and the propagating chain ends. The stability of the propagating chain end of poly­(<b>1</b>) was confirmed by the quantitative efficiencies in the postpolymerization and the sequential copolymerization with <i>tert</i>-butyl methacrylate. A poly­(4-formylstyrene) was quantitatively formed by the acidic hydrolysis reaction of the <i>N</i>-adamantylimino groups of the poly­(<b>1</b>). The resulting poly­(<b>1</b>) and poly­(<b>2</b>) showed significantly high glass transition temperatures (<i>T</i>_g) at 257 and 209 °C, respectively, due to the bulky and stiff adamantyl substituents. It was also found that the substituted position of adamantane unit and the linkage between polystyrene backbone and adamantyl groups played very important roles to determine the <i>T</i>_g values of the substituted polystyrenes