Continuous Process for the Synthesis of Dendrimer-Like Star Polymers by Anionic Polymerization

A continuous anionic living process for the fast synthesis of dendrimer-like star polymers is described. The process is based on the selective addition of sec-butyllithium (s-BuLi) toward 1,3-bis(1-phenylethenyl)benzene (MDDPE), which gives stoichiometric monoadduct in tetrahydrofuran (THF). The monoadduct, an anionic inimer-like molecule, is then used as the branching agent in the synthesis of dendrimer-like star polymers. Thus, alpha,omega-bifunctional polystyryllithium (G1.0), initiated by a difunctional anionic initiator, undergoes addition reaction with the monoadduct to form a tetrafunctional species, which is able to initiate the polymerization of styrene to form a four-arm star with terminal polystyryl anions (G2.0). Repeating addition/polymerization in an alternate way leads to the formation of a dendrimer-like star polystyrene up to the fifth generation, G5.0. The process is performed in a continuous way without separation of the intermediate species. The synthetic procedure of dendritic polystyrene is greatly accelerated, e.g., G5.0 with 32 terminal groups being obtained within 12 h. Because the product is living, it is employed as a dendritic precursor to prepare dendrimer-like star block copolymers such as PS-b-PI, PS-b-PMMA, and dendrimer-like star polymer with a graft-on-graft periphery. The solution properties of the dendrimer-like star products, such as viscosity as a function of molecular weight and globular shape, are investigated using viscometry and laser light scattering. The morphology of the individual molecules is observed using AFM and TEM.