Synthesis of well‐defined difunctional polydimethylsiloxane with an efficient dianionic initiator for ABA triblock copolymer

A new efficient dianionic initiator dipotassium diphenylsilanediolate (Ph 2 Si(OK) 2 ) was synthesized by reacting diphenylsilanediol with potassium in the mixture of THF and benzene. The anionic ring‐opening polymerization of octamethylcyclotetrasiloxane (D 4 ) or tetramethyltetravinylcyclotetrasiloxane (D   4 Vi ) initiated by Ph 2 Si(OK) 2 was systematically investigated. A number of factors including the nature of initiators, promoters, and monomers, the molar ratio of promoter to initiator ( C p / C i ratio) and monomer to initiator ( C m / C i ratio) affect the polymerization remarkably. Using N ‐methyl‐2‐pyrrolidinone as the promoter, a series of well‐defined difunctional HSi‐terminated polydimethylsiloxanes (PDMSs) were prepared with high monomer conversion (> 90%) and relatively low polydispersity (< 1.6) at 30°C. By hydrosilation of the synthesized PDMS with ally end‐capped poly(ethylene oxide) (PEO), amphiphilic PEO‐ b ‐PDMS‐ b ‐PEO triblock copolymers with low polydispersities and high block purities were obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 153–159, 2007