Title: degree-of-polymerisation dispersity
Long Title: IUPAC Gold Book - degree-of-polymerisation dispersity
DOI: 10.1351/goldbook.12225
Status: current

Definition
Ratio of the mass-average degree of polymerisation, \(X_{\rm{m}}\), to the number-average degree of polymerisation, \(X_{\rm{n}}\). \[Ð\!_{\rm{X}} = X_{\rm{m}}/X_{\rm{n}}\]

Note
Use of the term "polydispersity index", or other terms involving the word "polydispersity", for \(X_{\rm{m}}/X_{\rm{n}}\) is strongly discouraged.

Source
- PAC, 2015, 87, 71. 'Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)' on page 88 (https://doi.org/10.1515/pac-2013-0201)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/12225/html
- json: https://goldbook.iupac.org/terms/view/12225/json
- xml: https://goldbook.iupac.org/terms/view/12225/xml

Citation: Citation: 'degree-of-polymerisation dispersity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.12225
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Accessed: 2026-06-28T20:27:54+00:00