in polymers
The whole or part of a macromolecule, an oligomer molecule or a block, comprising a linear or branched sequence of constitutional units between two boundary constitutional units, each of which may be either an end-group, a branch point or an otherwise-designated characteristic feature of the macromolecule.
  1. Except in linear single-strand macromolecules, the definition of a chain may be somewhat arbitrary.
  2. A cyclic macromolecule has no end groups but may nevertheless be regarded as a chain.
  3. Any number of branch points may be present between the boundary units.
  4. Where appropriate, definitions relating to 'macromolecule' may also be applied to 'chain'.
PAC, 1996, 68, 2287 (Glossary of basic terms in polymer science (IUPAC Recommendations 1996)) on page 2293