ladder chain
A double-strand chain, consisting of an uninterrupted sequence of rings, with adjacent rings having two or more atoms in common. Alternatively, a ladder chain is a double-strand chain with adjacent constitutional units joined to each other through four atoms, two on one side and two on the other side of each constitutional units.
PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2295 (