Anionic Synthesis of Well-Defined Poly(m-halomethylstyrene)s and Branched Polymers via Graft-onto Methodology

The anionic polymerization of m -( tert -butyldimethylsilyl)oxymethylstyrene ( 1 ) was carried out with s -BuLi in THF at −78 °C. Under these conditions, the polymerization proceeds in a living manner to afford polymers with predictable molecular weights and narrow molecular weight distributions. Well-defined block copolymers of 1 with styrene were successfully synthesized. Poly( 1 )s were transformed quantitatively into poly( m -halomethylstyrene)s (halogen: Cl, Br, I) by treating with BCl 3, (CH 3 ) 3 SiCl−LiBr, and (CH 3 ) 3 SiCl−NaI, respectively. The resulting polymers with highly reactive benzyl halides in all monomer units retained the well-controlled structures of their parent polymers. The well-defined poly( m -halomethylstyrene)s were then coupled with living anionic polymers of styrene in THF. Well-defined comblike branched polystyrenes having almost one branch per monomer unit were prepared by coupling poly( m -chloromethylstyrene) both with polystyryllithium in THF at −78 °C for 72 h and with polystyryllithium end-capped with 1,1-diphenylethylene (DPE) in THF at −40 °C for 168 h. They were also prepared by the coupling reactions of poly( m- bromomethylstyrene)s with the DPE end-capped polystyryl anions in THF at −78 °C for 72 h and at −40 °C for 168 h. Their backbone and branch chains had well-controlled molecular weights and narrow molecular weight distributions.