Synthesis of Hyperbranched Polysiloxanes by Base-Catalyzed Proton-Transfer Polymerization. Comparison of Hyperbranched Polymer Microstructure and Properties to Those of Linear Analogues Prepared by Cationic or Anionic Ring-Opening Polymerization

Treatment of 1-(hydroxydimethylsiloxy)pentamethylcyclotrisiloxane ( II ), a latent A 2 A‘B monomer, with a phosphazene P 4 - t -Bu superbase followed by quenching with vinyldimethylchlorosilane/triethylamine leads to a hyperbranched polysiloxane ( III ). The microstructure and properties of III are compared to those of linear analogues obtained by cationic or living anionic polymerization of 1-(vinyldimethylsiloxydimethylsiloxy)pentamethylcyclotrisiloxane ( I ).