in polymers
https://doi.org/10.1351/goldbook.C00946
The whole or part of a @[email protected], an @[email protected] or a @[email protected], comprising a linear or branched @[email protected] of @[email protected] between two boundary constitutional units, each of which may be either an @[email protected], a @[email protected] or an otherwise-designated characteristic feature of the macromolecule.
Notes:
  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'.
Source:
PAC, 1996, 68, 2287. (Glossary of basic terms in polymer science (IUPAC Recommendations 1996)) on page 2293 [Terms] [Paper]