Selectivity in anionic and cationic ring‐opening polymerizations of tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane

Abstract Anionic and cationic ring‐opening polymerizations of two novel cyclotrisiloxanes, tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane (I) and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane (II), are reported. Anionic ring‐opening polymerization of I or II leads to copolymers with highly regular microstructures. Copolymers obtained by cationic polymerizations of I or II, initiated by triflic acid, have less regular microstructures characteristic of chemoselective polymerization processes. The composition and microstructure of copolymers have been characterized by 1H and 29Si‐NMR, the molecular weight distributions by GPC, and the thermal properties by DSC and TGA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5235–5243, 2004