Dendritic Block and Dendritic Brush Copolymers through Anionic Macroinimer Approach

Abstract

Anionic macroinimer is prepared through selective monoaddition of polyisoprenyllithium (PILi) toward 1,3-bis(1-phenylvinyl)benzene (MDDPE) in THF/cyclohexane mixture. The resulting macroinimer, possessing a living anion and a diphenylethylene (DPE) group at the same end of the PI chain, undergoes self-condensing vinyl copolymerization (SCVCP) with styrene after the solvent has been switched from mixture of THF/cyclohexane into pure cyclohexane. Dendritic block copolymers of styrene and isoprene are obtained, in which PI chains are linked to the branch points. The molecular weights of the dendritic products mainly depend on the ratio of monomer to macroinimer, whereas PI chain length has only slight effects. The PI segments are subsequently epoxidized and grafted with PILi or polystyrenyllithium (PSLi) to give dendritic polymer brushes. Both dendritic block copolymers and dendritic polymer brushes show decreased intrinsic viscosities. Dendritic block copolymer of styrene and isoprene undergoes a specially slow process of self-assembly, from unimolecular micelles and intermediate compound micelles to large compound micelles, in mixed solvent (n-heptane/THF = 19/1, v/v). In addition, conversion of large compound micelles into lamellar structure is observed for the first time in self-assembly of dendritically branched polymers.