Anionic ring opening polymerization of cyclotetrasiloxanes with large substituents

Cyclotetrasiloxanes with large substituents were synthesized by hydrosilylation of 1,3,5,7‐tetramethylcyclotetrasiloxane with CH2=CHCH2X, X being (CH2)2CH3, O(CH2CH2O)3CH3, OCH2epoxy and OCH2‐ benzo‐18‐crown‐6. The tetrasubstituted cycles were homo‐polymerized or copolymerized with octamethylcyclotetrasiloxane in the presence of potassium silanolate to yield polysiloxanes with side chains containing oxirane rings, crown ethers or oxyethylene ligands. In addition to a complex mixture of cycles, about 50 to 80% polymer can be recovered. The copolymer generally contains less of the substituted monomer than the starting monomer feed, but the bulky substituents do not appear to prevent formation of homo‐ or copolymer.