symbol: $Ð\!_{\rm{M}}$
synonyms: molecular-weight dispersity, relative-molar-mass dispersity, relative-molecular-mass dispersity
https://doi.org/10.1351/goldbook.12224
Ratio of the mass-average molar mass, \(M_{\rm{m}}\), molecular weight, relative molar mass, or relative molecular mass, \(M_{\rm{r,m}}\), to the number-average molar mass, \(M_{\rm{n}}\), molecular weight, relative molar mass, or relative molecular mass, \(M_{\rm{r,n}}\). \[Ð\!_{\rm{M}} = M_{\rm{m}}/M_{\rm{n}} = M_{\rm{r,m}}/M_{\rm{r,n}}\]
Note: Use of the term "polydispersity index", or other terms involving the word "polydispersity", for \(M_{\rm{m}}/M_{\rm{n}}\), \(M_{\rm{r,m}}/M_{\rm{r,n}}\) is strongly discouraged.