Ultrafast phosphazene-promoted controlled anionic polymerization of styrenic monomers

Abstract

The anionic polymerization of styrenic monomers with phosphazene bases as promoters, utilizing “seeding” technique in a nonpolar solvent and at room temperature was studied. In all experiments, the phosphazene base (t-BuP4, t-BuP2, and t-BuP1) was added in an equimolar amount to the organolithium initiator after the formation of oligomers (2 min) by conventional anionic polymerization. When t-BuP4 was used, the polymerization of styrene and 4-methylstyrene was extremely fast (100 % conversion within 5 min) and the final homopolymers exhibited narrow molecular weight distribution and controlled molecular characteristics. Likewise, when weaker bases were employed, the polymerization was also controlled but showing slower reaction rate. To examine the “livingness” of this system, block copolymers were synthesized by sequential monomer addition. Further studies were conducted in order to extend this novel method to the anionic polymerization of dienes.