The cyclic trimer (Me2SiO)3 has an internal ring tension
and can be polymerized without reequilibration of the resulting
polymers. With this cyclic, polymers with narrow molecularweight
distribution can be prepared, but also polymers only
carrying one terminal reactive function (living polymerization).
Starting from a mixture of different “tense” cyclics also allows
the preparation of block or sequential polymers (Noll, 1968).