Anionic polymerization of 1,3-pentadiene in toluene: homopolymer, alternating and block copolymers

The anionic polymerization of (E)-1,3-pentadiene (EP) and (Z)-1,3-pentadiene (ZP) was performed in aromatic solvent using n-butyllithium as initiator. In contrast to poly(ZP) s, the resulting poly(EP) s possessed the predicted molecular weights and narrow molecular weight distributions ((D) over bar <= 1.15). However, THF as polar additive has proved its validity to reduce the molecular weight distribution of poly(ZP) from 1.55 to as low as 1.16. The H-1 NMR and C-13 NMR results indicated that both poly(EP) and poly(ZP) consist of 1,4-addition & 1,2-addition units, without 3,4-addition units. Moreover, a novel, well-defined styrene-pentadiene alternating copolymer has been synthesized in toluene via living anionic copolymerization and the NMR spectra demonstrated that the resulting copolymers obtained possess a strictly alternating structure and much narrower polydispersity ((D) over bar <= 1.17). Finally, the living nature of the polymerization was also inspected via sequential copolymerization with methyl methacrylate (MMA) and 2-vinylpyridine (2VP) to yield well-controlled diblock copolymers (poly(EP)-b-poly(MMA) & poly(EP)-b-poly(2VP)).