Oligomerization of electron-deficient vinyl monomers through an ate-complex mechanism: a new role for b(c(6) f(5) )(3) lewis Acid

Cationic Polymerization of Hexamethylcyclotrisiloxane in Excess Water

Ring-opening ionic polymerization of cyclosiloxanes in dispersed media has long been discovered, and is nowadays both fundamentally studied and practically used. In this short communication, we show some preliminary results on the cationic ring-opening polymerization of hexamethylcyclotrisiloxane (D₃), a crystalline strained cycle, in water. Depending on the catalyst or/and surfactants used, polymers of various molar masses are prepared in a straightforward way. Emphasis is given here on experiments conducted with tris(pentafluorophenyl)borane (BCF), where high-molar polymers were generated at room temperature. In surfactant-free conditions, µm-sized droplets are stabilized by silanol end-groups of thus generated amphiphilic polymers, the latter of which precipitate in the course of reaction through chain extension. Introducing various surfactants in the recipe allows generating smaller emulsions in size with close polymerization ability, but better final colloidal stability, at the expense of low small cycles’ content. A tentative mechanism is finally proposed.

Photoinduced Polysiloxane Architectures from Spirosiloxane Precursors via Intramolecular Hydrosilylation

In this letter a method is described to synthesize new polysiloxane architectures by photoacid catalysis. An oxasilaspirocycle is designed that is able to undergo a photoacid generator catalyzed ring-opening reaction leading to either a homopolymer or to copolymers with hydroxyl-terminated polydimethylsiloxane. These polymers feature a defined amount of double bonds in the backbone, which is controlled by the ratio of oxasilaspirocycle to the comonomer. The former was prepared by trispentafluorophenylborane-catalyzed intramolecular hydrosilylation of a dialkenyloxysilane with an appropriate structural motif. The UV-initiated polymerization was characterized via in situ IR spectroscopic studies to determine the rate of reaction.