Synthesis of nearly monodisperse poly(α‐methylstyrene)s containing two Si atoms and an allyl group and the application to resist

The anionic polymerizations of 4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene (1), 4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene (2), and 4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene (3) have been conducted. Nearly monodisperse poly(4‐allyldimethylsilyldimethylsilyl‐α‐methylstyrene) (4), poly(4‐allyldimethylsilylmethyldimethylsilyl‐α‐methylstyrene) (5), and poly(4‐allyldimethylsilylethyldimethylsilyl‐α‐methylstyrene) (6) were obtained. The Tgs of 4, 5, and 6 are 100.5, 39.0, and 30.5°C, respectively. Among these, 4 has attracted most interest because of a high Tg (100.5°C) and a high Si content (20.5%, w/w). Therefore, a near‐UV resist (DMAS‐A) composed of 4 and a bisazide has been developed as a top resist layer for a bilayer system.