Controlled Anionic Synthesis of Polyisoprene−Poly(2-vinylpyridine) Diblock Copolymers in Hydrocarbon Solution

Well-defined diblock copolymers of isoprene and 2-vinylpyridine (2VP) were prepared by sequential anionic polymerization at temperatures of 45 and 6−8 °C, respectively, in benzene solution using sec -BuLi as initiator in the presence of lithium chloride ([LiCl]/[PLi] = 5−11). Rapid quenching with acidic methanol 4−7 min after 2VP addition was required to obtain controlled polymerization. The polyisoprene- block -poly(2-vinylpyridine) diblock copolymers with high 1,4-polyisoprene microstructure exhibited narrow molecular weight distributions [ M w / M n (SEC) = 1.01−1.06] and molecular weights (light scattering, universal calibration) that were in good agreement with calculated values. Molecular weights ( M n ) determined by SEC with polyisoprene standards were much lower than calculated values.