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).