114442-01-2Relevant academic research and scientific papers
Anionic polymerization of p-pentamethyldisilyl-, p-heptamethyltrisilyl-, and p-nonamethyltetrasilylstyrenes
Hirao, Akira,Ando, Yushi,Ishizone, Takashi,Nakahama, Seiichi
, p. 5081 - 5087 (2007/10/03)
The anionic polymerizations of p-pentamethyldisilylstyrene (1), p-heptamethyltrisilylstyrene (2), and p-nonamethyltetrasilylstyrene (3) were carried out under various conditions. The polymerizations of 1 and 2 proceeded in a living manner in THF at -78 °C to quantitatively afford polymers with predictable molecular weights and narrow molecular weight distributions. Suitable initiators for these living anionic polymerizations were sec-BuLi, lithium, sodium, and potassium naphthalenides, cumylpotassium, and living oligomers of α-methylstyrene lithium, sodium, and potassium salts. Well-defined diblock copolymers, poly(1)-block-polystyrene, poly(2)-block-polystyrene, polystyrene-block-poly(1), and polystyrene-block-poly(2) were successfully synthesized under similar conditions by a two-step sequential monomer addition, namely, styrene followed by 1 or 2, or vice versa. In contrast, the polymerization of 3 was problematic. No polymer was obtained in the polymerization of 3 in either THF at -78 °C or benzene at 40 °C with sec-BuLi and oligo(α-methylstyryl)lithium. Using oligo(α-methylstyryl)potassium as an initiator, 3 was polymerized quantitatively in THF at -78 °C for 0.5 h. Unfortunately, the side reaction, presumably attack of the Si-Si-Si-Si bond by the growing chain-end anion, could not be completely suppressed during the polymerization, which resulted in the formation of high molecular weight polymers by coupling between polymer chains.
