composed of molecules uniform with respect to relative molecular mass
A polymer comprising a mixture of linear and branched chains, all of uniform relative molecular mass, is not uniform.
A copolymer comprising linear molecules of uniform relative molecular mass and uniform elemental composition but different sequential arrangements of the various
types of monomeric units, is not uniform (e.g. a copolymer comprising molecules with a random arrangement as well as a block arrangement of monomeric units).
A polymer uniform with respect only to either relative molecular mass or constitution may be termed 'uniform', provided a suitable qualifier is used (e.g. 'a polymer uniform with respect to relative molecular mass').
The adjectives 'monodisperse' and 'polydisperse' are deeply rooted in the literature, despite the former being non-descriptive and
self-contradictory. They are in common usage and it is recognized that they will continue
to be used for some time; nevertheless, more satisfactory terms are clearly desirable.
After an extensive search for possible replacements, the terms 'uniform' and 'non-uniform' have been selected and they are now the preferred adjectives.
PAC, 1996, 68, 2287
(Glossary of basic terms in polymer science (IUPAC Recommendations 1996))
on page 2301