Protection and polymerization of functional monomers, 26. Synthesis of well-defined poly[4-(3′-butynyl)styrene] by means of anionic polymerization of 4-(4′-trimethylsilyl-3′-butynyl)styrene

Anionic polymerization of 4-(4′-trimethylsilyl-3′-butynyl)styrene ( 2 ) was carried out in THF at ?78°C for 0.5 h with oligo(α-methylstyryl)lithium, -dilithium, and -dipotassium. Poly( 2 )s possessing predicted molecular weights and narrow molecular weight distributions (M?_w/M?_n < 1.11) were quantitatively obtained in all cases. By sequential anionic copolymerization of 2 and styrene, novel block copolymers, polystyrene-block-poly( 2 ) starting either from living polystyrene or living poly( 2 ), were synthesized. After completion of the polymerization, there occurred some gradual deactivation of the propagating carbanion of poly( 2 ) at ?78°C. This deactivation reaction could be almost completely suppressed at ?95°C. The deprotection of poly( 2 ) was performed by treating with Bu₄NF in THF at 0°C for 1 h. The trimethylsilyl protecting group of poly( 2 ) was completely removed to afford a poly[4-(3′-butynyl)styrene] of a controlled molecular structure.