Controlled anionic synthesis of polyisoprene-poly(2-vinylpyridine) diblockcopolymers 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 degreesC, respectively, in benzene solution using sec-BuLi as initiator in the presence of lithium chloride ([LiCl]/[PLi] = 5-11). Rapid quenching wi th acidic methanol 4-7 min after 2VP addition was required to obtain contro lled polymerization. The polyisoprene-bloch-poly(2-vinylpyridine) diblock c opolymers with high 1,4-polyisoprene microstructure exhibited narrow molecu lar weight distributions [M-w/M-n(SEC) = 1.01-1.06] and molecular weights ( light scattering, universal calibration) that were in good agreement with c alculated values. Molecular weights (M-n) determined by SEC with polyisopre ne standards were much lower than calculated values.