Polystyrene Chain Growth Initiated from Dialkylzinc for Synthesis of Polyolefin-Polystyrene Block Copolymers.

Polyolefins (POs) are the most abundant polymers. However, synthesis of PO-based block copolymers has only rarely been achieved. We aimed to synthesize various PO-based block copolymers by coordinative chain transfer polymerization (CCTP) followed by anionic polymerization in one-pot via conversion of the CCTP product (polyolefinyl)Zn to polyolefinyl-Li. The addition of 2 equiv -BuLi to (1-octyl)Zn (a model compound of (polyolefinyl)Zn) and selective removal or decomposition of (Bu)Zn by evacuation or heating at 130 °C afforded 1-octyl-Li. Attempts to convert (polyolefinyl)Zn to polyolefinyl-Li were unsuccessful. However, polystyrene (PS) chains were efficiently grown from (polyolefinyl)Zn; the addition of styrene monomers after treatment with -BuLi and pentamethyldiethylenetriamine (PMDTA) in the presence of residual olefin monomers afforded PO--PSs. Organolithium species that might be generated in the pot of -BuLi, PMDTA, and olefin monomers, i.e., [MeNCHCHN(Me)CHCHN(Me)CHLi, MeNCHCHN(Me)Li·(PMDTA), pentylallyl-Li⋅(PMDTA)], as well as PhLi⋅(PMDTA), were screened as initiators to grow PS chains from (1-hexyl)Zn, as well as from (polyolefinyl)Zn. Pentylallyl-Li⋅(PMDTA) was the best initiator. The values increased substantially after the styrene polymerization with some generation of homo-PSs (27-29%). The values of the extracted homo-PS suggested that PS chains were grown mainly from polyolefinyl groups in [(polyolefinyl)(pentylallyl)Zn][Li⋅(PMDTA)] formed by pentylallyl-Li⋅(PMDTA) acting onto (polyolefinyl)Zn.