Depends on the bond pattern. Alternating single and triple bonds (polycarbyne or polyyne) would be arrow-straight, rigid, semiconducting, untwisting, and explo

Depends on the bond pattern. Alternating single and triple bonds (polycarbyne or polyyne) would be arrow-straight, rigid, semiconducting, untwisting, and explosive in bulk. Triple C-C bonds are an open invitation for cross-linking. In order to be stable, they have to be capped with a less-reactive group than hydrogen. If you break a ring, and get a C18 with naked electrons instead of protons on the ends, that's going to react with something, quickly and probably energetically. That bond-bending energy has to go somewhere, too. If you break the ring, you're probably going to break the molecule near the antipode, too, giving you two highly reactive C9s, or a C10 and a C8. Like if you cut a bowstring at full draw, you're probably going to break one of the limbs of the bow.