The synthesis of diene– alkyl methacrylate diblock and heteroarm star copolymers

The synthesis of A2B2 heteroarm stars, where A is either polyisoprene (PI) or polybutadiene (PB) and B is either poly(methyl methacrylate) (PMMA) or poly(butyl methacrylate) (PBMA) has been achieved using living anionic polymerization. Following polymerization of the diene in hexane by sec-BuLi, the solvent was changed to THF and the living chains were linked in pairs – without loss of anionic reactivity – using 1,2-bis[4-(1-phenylethenyl)]ethane (EPEB). Star synthesis was completed by the addition of MMA or BMA monomer at −78°C. The diblocks were prepared by sequential polymerization. The resulting stereochemistries were those of greatest interest from a practical standpoint, i.e., PI or PB with a high 1,4-content (which is highly elastic) and syndiotactic PMMA (which has a high Tg).