The ring expansion or contraction reactions of inorganic cyclic molecules often depend on structural features such as ring strain or side group intramolecular interactions. The ability of an inorganic cyclic system to undergo ring-opening polymerization to open-chain macromolecules usually depends on the same factors. in this paper the influence of transannular structures or heteroelements in the ring on ring-ring or ring-polymer interconversions will be discussed. Particular emphasis is placed on the way in which certain side groups switch the reaction pathway from ring expansion to polymerization. Polymers formed from these ring systems are of interest as electroactive or elastomeric materials, and structure-property relationships are discussed.