End group
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An end-group in polymer chemistry is a constitutional unit that is an extremity of a macromolecule or oligomer molecule.[1] For example the end-group of a PET polyester may be an alcohol group or a carboxylic acid group.
Each end-group is bonded to just one repetitive unit.[1] A linear polymer contains two end-groups.
End groups in macromolecules may have special reactivity in follow-up reactions, see graft copolymers, or end groups can be used to determine molar mass.