Question

The PDI (polydisersity index) is the ratio of weight to number-average molecular masses, $M\overline{w}/M\overline{n}$. In natural polymers, which are generally monodispersed, PDI is ............. and in synthetic polymers which are always polydispersed, PDI is ............. because $M\overline{w}$ is always ............. than $M\overline{n}$. Fill in the blanks.

• A. greater than $1$, $1$, higher
• B. $1$, greater than $1$, higher
• C. less than $1$, $1$, lower
• D. $1$, less than $1$, lower

Answer 1

The correct option is B $1$, greater than $1$, higher

The PDI (polydisersity index) is the ratio of weight to number-average molecular masses, $M\overline{w}/M\overline{n}$. In natural polymers, which are generally monodispersed, PDI is 1 and in synthetic polymers which are always polydispersed, PDI is greater than 1 because $M\overline{w}$ is always higher than $M\overline{n}$.