Silyl ester initiators for ring opening polymerization of cyclosiloxanes

摘要

Method of making polysiloxanes by ring opening polymerization of dimethylcyclosiloxanes such as hexamethylcyclotrisiloxane (D₃) and cyclosiloxanes such as 1,3,5-trimethyl-1,3,5-tris (3',3',3'-trifluoropropyl) cyclotrisiloxane (F₃) or 1,3,5,7-tetramethyl-1,3,5,7-tetrakis(3',3',3'-trifluoropropyl) cyclotetrasiloxane (F₄) in an acid-free system using electrophillic initiators. The reaction mixture is formed under anhydrous conditions and contains (i) the cyclosiloxanes, (ii) a Lewis base such as 2,6-di-tert-butylpyridine which serves as a co-catalyst and an acid scavenger and, optionally, (iii) a salt of a strong acid such as tetrabutylammonium trifluoromethane sulfonate. The anhydrous mixture is contacted with a silyl ester of a strong acid such as triflic acid. The anhydrous reaction mixture is agitated at room temperature until a polysiloxane is formed. Polymerization can be initiated practically immediately after introduction of the cyclosiloxanes, by first adding the Lewis base to the silyl ester and allowing the Lewis base and the silyl ester to interact.